Paso Robles City Council
April 21, 2026

2022_Ardmore Type I 24-hr _95th Rainfall=1.45", AMC=1
Prepared by Wallace Group Printed 2/17/2023
HydroCAD® 10.20-2f s/n 05444 © 2022 HydroCAD Software Solutions LLC Page 80 Pond LID A1: A-1 Chambers - Chamber Wizard Field A
Chamber Model = ADS_StormTech MC-3500 d +Cap (ADS StormTech® MC-3500 d rev 03/14 with Cap volume)
Effective Size= 70.4"W x 45.0"H => 15.33 sf x 7.17'L = 110.0 cf Overall Size= 77.0"W x 45.0"H x 7.50'L with 0.33' Overlap Cap Storage= 14.9 cf x 2 x 7 rows = 208.6 cf

77.0" Wide + 9.0" Spacing = 86.0" C-C Row Spacing
35 Chambers/Row x 7.17' Long +1.85' Cap Length x 2 = 254.65' Row Length +12.0" End Stone x 2 = 256.65' Base Length
7 Rows x 77.0" Wide + 9.0" Spacing x 6 + 12.0" Side Stone x 2 = 51.42' Base Width

9.0" Stone Base + 45.0" Chamber Height + 12.0" Stone Cover = 5.50' Field Height 245 Chambers x 110.0 cf + 14.9 cf Cap Volume x 2 x 7 Rows = 27,146.8 cf Chamber Storage 72,578.5 cf Field - 27,146.8 cf Chambers = 45,431.7 cf Stone x 40.0% Voids = 18,172.7 cf Stone Storage Chamber Storage + Stone Storage = 45,319.5 cf = 1.040 af Overall Storage Efficiency = 62.4%
Overall System Size = 256.65' x 51.42' x 5.50'
245 Chambers
2,688.1 cy Field
1,682.7 cy Stone

2022_Ardmore Type I 24-hr _95th Rainfall=1.45", AMC=1
Prepared by Wallace Group Printed 2/17/2023
HydroCAD® 10.20-2f s/n 05444 © 2022 HydroCAD Software Solutions LLC Page 81 Pond LID A1: A-1 Chambers
Inflow
Outflow
Discarded
Primary
Hydrograph
Time (hours)
727068666462605856545250484644424038363432302826242220181614121086420 Flow (cfs)
3 2
1 0
Inflow Area=6.074 ac
Peak Elev=818.57'
Storage=0.304 af

3.33 cfs

0.06 cfs

0.06 cfs

0.00 cfs

2022_Ardmore Type I 24-hr _95th Rainfall=1.45", AMC=1
Prepared by Wallace Group Printed 2/17/2023
HydroCAD® 10.20-2f s/n 05444 © 2022 HydroCAD Software Solutions LLC Page 82 Summary for Pond LID A2: A-2 Bioretention
Inflow Area = 1.122 ac, 86.00% Impervious, Inflow Depth = 0.77" for _95th event Inflow = 0.62 cfs @ 9.94 hrs, Volume= 0.072 af
Outflow = 0.17 cfs @ 10.31 hrs, Volume= 0.072 af, Atten= 72%, Lag= 21.7 min Discarded = 0.17 cfs @ 10.31 hrs, Volume= 0.072 af
Primary = 0.00 cfs @ 0.00 hrs, Volume= 0.000 af
Routed to Link A : Outlet A
Routing by Dyn-Stor-Ind method, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Peak Elev= 823.17' @ 10.31 hrs Surf.Area= 2,267 sf Storage= 576 cf Plug-Flow detention time= 27.4 min calculated for 0.072 af (100% of inflow) Center-of-Mass det. time= 27.4 min ( 814.4 - 787.0 )
Volume Invert Avail.Storage Storage Description
#1 821.90' 5,348 cf Roadside Bioretention (Prismatic) Listed below (Recalc) Elevation Surf.Area Voids Inc.Store Cum.Store
(feet) (sq-ft) (%) (cubic-feet) (cubic-feet)
821.90 0 0.0 0 0
823.90 3,565 40.0 1,426 1,426
825.90 3,565 30.0 2,139 3,565
826.40 3,565 100.0 1,783 5,348
Device Routing Invert Outlet Devices
#1 Primary 825.90' 3.6" x 1.0" Horiz. Orifice/Grate X 77.00 C= 0.600 in 18.0" x 18.0" Grate (86% open area)
Limited to weir flow at low heads
#2 Discarded 821.90' 3.250 in/hr Exfiltration over Surface area Conductivity to Groundwater Elevation = 100.00'
Discarded OutFlow Max=0.17 cfs @ 10.31 hrs HW=823.17' (Free Discharge) 2=Exfiltration ( Controls 0.17 cfs)
Primary OutFlow Max=0.00 cfs @ 0.00 hrs HW=821.90' TW=0.00' (Dynamic Tailwater) 1=Orifice/Grate ( Controls 0.00 cfs)

2022_Ardmore Type I 24-hr _95th Rainfall=1.45", AMC=1
Prepared by Wallace Group Printed 2/17/2023
HydroCAD® 10.20-2f s/n 05444 © 2022 HydroCAD Software Solutions LLC Page 83 Pond LID A2: A-2 Bioretention
Inflow
Outflow
Discarded
Primary
Hydrograph
Time (hours)
727068666462605856545250484644424038363432302826242220181614121086420 Flow (cfs)

0.65 0.6

0.55 0.5

0.45 0.4

0.35 0.3

0.25 0.2

0.15 0.1

0.05 0
Inflow Area=1.122 ac
Peak Elev=823.17'
Storage=576 cf

0.62 cfs

0.17 cfs

0.17 cfs

0.00 cfs

2022_Ardmore Type I 24-hr _95th Rainfall=1.45", AMC=1
Prepared by Wallace Group Printed 2/17/2023
HydroCAD® 10.20-2f s/n 05444 © 2022 HydroCAD Software Solutions LLC Page 84 Summary for Pond LID B1a: B-1a Chambers
Inflow Area = 1.360 ac, 74.37% Impervious, Inflow Depth = 0.67" for _95th event Inflow = 0.65 cfs @ 9.94 hrs, Volume= 0.075 af
Outflow = 0.02 cfs @ 24.02 hrs, Volume= 0.075 af, Atten= 98%, Lag= 844.5 min Discarded = 0.02 cfs @ 24.02 hrs, Volume= 0.075 af
Primary = 0.00 cfs @ 0.00 hrs, Volume= 0.000 af
Routed to Link B : Outlet B
Routing by Dyn-Stor-Ind method, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Peak Elev= 820.61' @ 24.02 hrs Surf.Area= 0.155 ac Storage= 0.055 af Plug-Flow detention time= 1,453.6 min calculated for 0.075 af (99% of inflow) Center-of-Mass det. time= 1,447.4 min ( 2,235.2 - 787.7 ) Volume Invert Avail.Storage Storage Description
#1A 819.80' 0.217 af 87.25'W x 77.40'L x 5.50'H Field A

0.853 af Overall - 0.311 af Embedded = 0.542 af x 40.0% Voids #2A 820.55' 0.311 af ADS_StormTech MC-3500 d +Cap x 120 Inside #1 Effective Size= 70.4"W x 45.0"H => 15.33 sf x 7.17'L = 110.0 cf Overall Size= 77.0"W x 45.0"H x 7.50'L with 0.33' Overlap 120 Chambers in 12 Rows
Cap Storage= 14.9 cf x 2 x 12 rows = 357.6 cf

0.528 af Total Available Storage
Storage Group A created with Chamber Wizard
Device Routing Invert Outlet Devices
#1 Primary 822.63' 18.0" Round Culvert L= 50.0' Ke= 0.500 Inlet / Outlet Invert= 822.63' / 822.50' S= 0.0026 '/' Cc= 0.900 n= 0.012 Corrugated PP, smooth interior, Flow Area= 1.77 sf #2 Discarded 819.80' 0.100 in/hr Exfiltration over Surface area Conductivity to Groundwater Elevation = 98.80' Phase-In= 0.10' Discarded OutFlow Max=0.02 cfs @ 24.02 hrs HW=820.61' (Free Discharge) 2=Exfiltration ( Controls 0.02 cfs)
Primary OutFlow Max=0.00 cfs @ 0.00 hrs HW=819.80' TW=0.00' (Dynamic Tailwater) 1=Culvert ( Controls 0.00 cfs)

2022_Ardmore Type I 24-hr _95th Rainfall=1.45", AMC=1
Prepared by Wallace Group Printed 2/17/2023
HydroCAD® 10.20-2f s/n 05444 © 2022 HydroCAD Software Solutions LLC Page 85 Pond LID B1a: B-1a Chambers - Chamber Wizard Field A
Chamber Model = ADS_StormTech MC-3500 d +Cap (ADS StormTech® MC-3500 d rev 03/14 with Cap volume)
Effective Size= 70.4"W x 45.0"H => 15.33 sf x 7.17'L = 110.0 cf Overall Size= 77.0"W x 45.0"H x 7.50'L with 0.33' Overlap Cap Storage= 14.9 cf x 2 x 12 rows = 357.6 cf

77.0" Wide + 9.0" Spacing = 86.0" C-C Row Spacing
10 Chambers/Row x 7.17' Long +1.85' Cap Length x 2 = 75.40' Row Length +12.0" End Stone x 2 = 77.40' Base Length
12 Rows x 77.0" Wide + 9.0" Spacing x 11 + 12.0" Side Stone x 2 = 87.25' Base Width

9.0" Stone Base + 45.0" Chamber Height + 12.0" Stone Cover = 5.50' Field Height 120 Chambers x 110.0 cf + 14.9 cf Cap Volume x 2 x 12 Rows = 13,551.8 cf Chamber Storage 37,142.3 cf Field - 13,551.8 cf Chambers = 23,590.5 cf Stone x 40.0% Voids = 9,436.2 cf Stone Storage Chamber Storage + Stone Storage = 22,988.0 cf = 0.528 af Overall Storage Efficiency = 61.9%
Overall System Size = 77.40' x 87.25' x 5.50'
120 Chambers
1,375.6 cy Field
873.7 cy Stone

2022_Ardmore Type I 24-hr _95th Rainfall=1.45", AMC=1
Prepared by Wallace Group Printed 2/17/2023
HydroCAD® 10.20-2f s/n 05444 © 2022 HydroCAD Software Solutions LLC Page 86 Pond LID B1a: B-1a Chambers
Inflow
Outflow
Discarded
Primary
Hydrograph
Time (hours)
727068666462605856545250484644424038363432302826242220181614121086420 Flow (cfs)

0.7 0.65

0.6 0.55

0.5 0.45

0.4 0.35

0.3 0.25

0.2 0.15

0.1 0.05
0 Inflow Area=1.360 ac
Peak Elev=820.61'
Storage=0.055 af

0.65 cfs

0.02 cfs

0.02 cfs

0.00 cfs

2022_Ardmore Type I 24-hr _95th Rainfall=1.45", AMC=1
Prepared by Wallace Group Printed 2/17/2023
HydroCAD® 10.20-2f s/n 05444 © 2022 HydroCAD Software Solutions LLC Page 87 Summary for Pond LID B1b: B-1b Bioretention
Inflow Area = 0.238 ac, 87.88% Impervious, Inflow Depth = 0.78" for _95th event Inflow = 0.13 cfs @ 9.94 hrs, Volume= 0.016 af
Outflow = 0.03 cfs @ 10.41 hrs, Volume= 0.016 af, Atten= 77%, Lag= 27.7 min Discarded = 0.03 cfs @ 10.41 hrs, Volume= 0.016 af
Primary = 0.00 cfs @ 0.00 hrs, Volume= 0.000 af
Routed to Link B : Outlet B
Routing by Dyn-Stor-Ind method, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Peak Elev= 821.94' @ 10.41 hrs Surf.Area= 667 sf Storage= 142 cf Plug-Flow detention time= 40.9 min calculated for 0.016 af (100% of inflow) Center-of-Mass det. time= 40.9 min ( 827.8 - 786.9 )
Volume Invert Avail.Storage Storage Description
#1 820.88' 1,884 cf Roadside Bioretention (Prismatic) Listed below (Recalc) Elevation Surf.Area Voids Inc.Store Cum.Store
(feet) (sq-ft) (%) (cubic-feet) (cubic-feet)
820.88 0 0.0 0 0
822.88 1,256 40.0 502 502
824.88 1,256 30.0 754 1,256
825.38 1,256 100.0 628 1,884
Device Routing Invert Outlet Devices
#1 Primary 824.88' 3.6" x 1.0" Horiz. Orifice/Grate X 77.00 C= 0.600 in 18.0" x 18.0" Grate (86% open area)
Limited to weir flow at low heads
#2 Discarded 820.88' 2.000 in/hr Exfiltration over Surface area Conductivity to Groundwater Elevation = 100.00' Phase-In= 0.10' Discarded OutFlow Max=0.03 cfs @ 10.41 hrs HW=821.94' (Free Discharge) 2=Exfiltration ( Controls 0.03 cfs)
Primary OutFlow Max=0.00 cfs @ 0.00 hrs HW=820.88' TW=0.00' (Dynamic Tailwater) 1=Orifice/Grate ( Controls 0.00 cfs)

2022_Ardmore Type I 24-hr _95th Rainfall=1.45", AMC=1
Prepared by Wallace Group Printed 2/17/2023
HydroCAD® 10.20-2f s/n 05444 © 2022 HydroCAD Software Solutions LLC Page 88 Pond LID B1b: B-1b Bioretention
Inflow
Outflow
Discarded
Primary
Hydrograph
Time (hours)
727068666462605856545250484644424038363432302826242220181614121086420 Flow (cfs)

0.14 0.13

0.12 0.11

0.1 0.09

0.08 0.07

0.06 0.05

0.04 0.03

0.02 0.01
0 Inflow Area=0.238 ac
Peak Elev=821.94'
Storage=142 cf

0.13 cfs

0.03 cfs

0.03 cfs

0.00 cfs

2022_Ardmore Type I 24-hr _95th Rainfall=1.45", AMC=1
Prepared by Wallace Group Printed 2/17/2023
HydroCAD® 10.20-2f s/n 05444 © 2022 HydroCAD Software Solutions LLC Page 89 Summary for Pond LID B2a: B-2a Chambers
Inflow Area = 1.200 ac, 92.04% Impervious, Inflow Depth = 0.82" for _95th event Inflow = 0.71 cfs @ 9.94 hrs, Volume= 0.082 af
Outflow = 0.02 cfs @ 24.01 hrs, Volume= 0.082 af, Atten= 97%, Lag= 844.0 min Discarded = 0.02 cfs @ 24.01 hrs, Volume= 0.082 af
Primary = 0.00 cfs @ 0.00 hrs, Volume= 0.000 af
Routed to Link B : Outlet B
Routing by Dyn-Stor-Ind method, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Peak Elev= 821.32' @ 24.01 hrs Surf.Area= 0.093 ac Storage= 0.058 af Plug-Flow detention time= 1,356.6 min calculated for 0.082 af (100% of inflow) Center-of-Mass det. time= 1,356.2 min ( 2,142.8 - 786.6 ) Volume Invert Avail.Storage Storage Description
#1A 820.19' 0.131 af 22.75'W x 177.78'L x 5.50'H Field A

0.511 af Overall - 0.184 af Embedded = 0.327 af x 40.0% Voids #2A 820.94' 0.184 af ADS_StormTech MC-3500 d +Cap x 72 Inside #1 Effective Size= 70.4"W x 45.0"H => 15.33 sf x 7.17'L = 110.0 cf Overall Size= 77.0"W x 45.0"H x 7.50'L with 0.33' Overlap 72 Chambers in 3 Rows
Cap Storage= 14.9 cf x 2 x 3 rows = 89.4 cf

0.315 af Total Available Storage
Storage Group A created with Chamber Wizard
Device Routing Invert Outlet Devices
#1 Primary 822.19' 18.0" Round Culvert L= 30.0' Ke= 0.500 Inlet / Outlet Invert= 822.19' / 821.89' S= 0.0100 '/' Cc= 0.900 n= 0.012 Corrugated PP, smooth interior, Flow Area= 1.77 sf #2 Discarded 820.19' 0.190 in/hr Exfiltration over Surface area Conductivity to Groundwater Elevation = 98.79' Phase-In= 0.10' Discarded OutFlow Max=0.02 cfs @ 24.01 hrs HW=821.32' (Free Discharge) 2=Exfiltration ( Controls 0.02 cfs)
Primary OutFlow Max=0.00 cfs @ 0.00 hrs HW=820.19' TW=0.00' (Dynamic Tailwater) 1=Culvert ( Controls 0.00 cfs)

2022_Ardmore Type I 24-hr _95th Rainfall=1.45", AMC=1
Prepared by Wallace Group Printed 2/17/2023
HydroCAD® 10.20-2f s/n 05444 © 2022 HydroCAD Software Solutions LLC Page 90 Pond LID B2a: B-2a Chambers - Chamber Wizard Field A
Chamber Model = ADS_StormTech MC-3500 d +Cap (ADS StormTech® MC-3500 d rev 03/14 with Cap volume)
Effective Size= 70.4"W x 45.0"H => 15.33 sf x 7.17'L = 110.0 cf Overall Size= 77.0"W x 45.0"H x 7.50'L with 0.33' Overlap Cap Storage= 14.9 cf x 2 x 3 rows = 89.4 cf

77.0" Wide + 9.0" Spacing = 86.0" C-C Row Spacing
24 Chambers/Row x 7.17' Long +1.85' Cap Length x 2 = 175.78' Row Length +12.0" End Stone x 2 = 177.78' Base Length
3 Rows x 77.0" Wide + 9.0" Spacing x 2 + 12.0" Side Stone x 2 = 22.75' Base Width

9.0" Stone Base + 45.0" Chamber Height + 12.0" Stone Cover = 5.50' Field Height 72 Chambers x 110.0 cf + 14.9 cf Cap Volume x 2 x 3 Rows = 8,005.9 cf Chamber Storage 22,244.7 cf Field - 8,005.9 cf Chambers = 14,238.8 cf Stone x 40.0% Voids = 5,695.5 cf Stone Storage Chamber Storage + Stone Storage = 13,701.5 cf = 0.315 af Overall Storage Efficiency = 61.6%
Overall System Size = 177.78' x 22.75' x 5.50'
72 Chambers
823.9 cy Field
527.4 cy Stone

2022_Ardmore Type I 24-hr _95th Rainfall=1.45", AMC=1
Prepared by Wallace Group Printed 2/17/2023
HydroCAD® 10.20-2f s/n 05444 © 2022 HydroCAD Software Solutions LLC Page 91 Pond LID B2a: B-2a Chambers
Inflow
Outflow
Discarded
Primary
Hydrograph
Time (hours)
727068666462605856545250484644424038363432302826242220181614121086420 Flow (cfs)

0.75 0.7

0.65 0.6

0.55 0.5

0.45 0.4

0.35 0.3

0.25 0.2

0.15 0.1

0.05 0
Inflow Area=1.200 ac
Peak Elev=821.32'
Storage=0.058 af

0.71 cfs

0.02 cfs

0.02 cfs

0.00 cfs

2022_Ardmore Type I 24-hr _95th Rainfall=1.45", AMC=1
Prepared by Wallace Group Printed 2/17/2023
HydroCAD® 10.20-2f s/n 05444 © 2022 HydroCAD Software Solutions LLC Page 92 Summary for Pond LID C2: C-1 Bioretention
Inflow Area = 0.223 ac, 72.91% Impervious, Inflow Depth = 0.65" for _95th event Inflow = 0.10 cfs @ 9.94 hrs, Volume= 0.012 af
Outflow = 0.04 cfs @ 10.21 hrs, Volume= 0.012 af, Atten= 66%, Lag= 16.2 min Discarded = 0.04 cfs @ 10.21 hrs, Volume= 0.012 af
Primary = 0.00 cfs @ 0.00 hrs, Volume= 0.000 af
Routed to Link C : Outlet C
Routing by Dyn-Stor-Ind method, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Peak Elev= 821.06' @ 10.21 hrs Surf.Area= 509 sf Storage= 82 cf Plug-Flow detention time= 17.1 min calculated for 0.012 af (100% of inflow) Center-of-Mass det. time= 17.1 min ( 804.9 - 787.9 )
Volume Invert Avail.Storage Storage Description
#1 820.25' 1,884 cf Roadside Bioretention (Prismatic) Listed below (Recalc) Elevation Surf.Area Voids Inc.Store Cum.Store
(feet) (sq-ft) (%) (cubic-feet) (cubic-feet)
820.25 0 0.0 0 0
822.25 1,256 40.0 502 502
824.25 1,256 30.0 754 1,256
824.75 1,256 100.0 628 1,884
Device Routing Invert Outlet Devices
#1 Primary 824.25' 3.6" x 1.0" Horiz. Orifice/Grate X 77.00 C= 0.600 in 18.0" x 18.0" Grate (86% open area)
Limited to weir flow at low heads
#2 Discarded 820.25' 3.000 in/hr Exfiltration over Surface area Conductivity to Groundwater Elevation = 100.00' Phase-In= 0.10' Discarded OutFlow Max=0.04 cfs @ 10.21 hrs HW=821.06' (Free Discharge) 2=Exfiltration ( Controls 0.04 cfs)
Primary OutFlow Max=0.00 cfs @ 0.00 hrs HW=820.25' TW=0.00' (Dynamic Tailwater) 1=Orifice/Grate ( Controls 0.00 cfs)

2022_Ardmore Type I 24-hr _95th Rainfall=1.45", AMC=1
Prepared by Wallace Group Printed 2/17/2023
HydroCAD® 10.20-2f s/n 05444 © 2022 HydroCAD Software Solutions LLC Page 93 Pond LID C2: C-1 Bioretention
Inflow
Outflow
Discarded
Primary
Hydrograph
Time (hours)
727068666462605856545250484644424038363432302826242220181614121086420 Flow (cfs)

0.115

0.11 0.105

0.1 0.095

0.09 0.085

0.08 0.075

0.07 0.065

0.06 0.055

0.05 0.045

0.04 0.035

0.03 0.025

0.02 0.015

0.01 0.005
0 Inflow Area=0.223 ac
Peak Elev=821.06'
Storage=82 cf

0.10 cfs

0.04 cfs

0.04 cfs

0.00 cfs

2022_Ardmore Type I 24-hr _95th Rainfall=1.45", AMC=1
Prepared by Wallace Group Printed 2/17/2023
HydroCAD® 10.20-2f s/n 05444 © 2022 HydroCAD Software Solutions LLC Page 94 Summary for Pond LID D: Basin
Inflow Area = 3.790 ac, 73.64% Impervious, Inflow Depth = 0.66" for _95th event Inflow = 1.78 cfs @ 9.94 hrs, Volume= 0.208 af
Outflow = 0.01 cfs @ 24.16 hrs, Volume= 0.049 af, Atten= 99%, Lag= 853.0 min Discarded = 0.01 cfs @ 24.16 hrs, Volume= 0.049 af
Primary = 0.00 cfs @ 0.00 hrs, Volume= 0.000 af
Routed to Link D : Outlet D
Secondary = 0.00 cfs @ 0.00 hrs, Volume= 0.000 af
Routed to Link D : Outlet D
Routing by Dyn-Stor-Ind method, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Peak Elev= 814.33' @ 24.16 hrs Surf.Area= 6,392 sf Storage= 8,527 cf Plug-Flow detention time= 1,811.0 min calculated for 0.049 af (24% of inflow) Center-of-Mass det. time= 1,572.8 min ( 2,360.6 - 787.8 ) Volume Invert Avail.Storage Storage Description
#1 810.00' 35,708 cf DMA D Basin (Prismatic) Listed below (Recalc) Elevation Surf.Area Voids Inc.Store Cum.Store
(feet) (sq-ft) (%) (cubic-feet) (cubic-feet)
810.00 4,775 0.0 0 0
812.00 4,775 40.0 3,820 3,820
814.00 4,775 30.0 2,865 6,685
815.00 9,674 100.0 7,225 13,910
816.00 10,885 100.0 10,280 24,189
817.00 12,153 100.0 11,519 35,708
Device Routing Invert Outlet Devices
#1 Primary 816.25' 3.6" x 1.0" Horiz. Orifice/Grate X 310.00 C= 0.600 in 36.0" x 36.0" Grate (86% open area)
Limited to weir flow at low heads
#2 Discarded 810.00' 0.070 in/hr Exfiltration over Surface area Conductivity to Groundwater Elevation = 100.00' Phase-In= 0.10' #3 Secondary 816.75' 30.0' long x 2.0' breadth Spillway_Broad-Crested Rectangular Weir Head (feet) 0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60 1.80 2.00

2.50 3.00 3.50
Coef. (English) 2.54 2.61 2.61 2.60 2.66 2.70 2.77 2.89 2.88

2.85 3.07 3.20 3.32
Discarded OutFlow Max=0.01 cfs @ 24.16 hrs HW=814.33' (Free Discharge) 2=Exfiltration ( Controls 0.01 cfs)
Primary OutFlow Max=0.00 cfs @ 0.00 hrs HW=810.00' TW=0.00' (Dynamic Tailwater) 1=Orifice/Grate ( Controls 0.00 cfs)
Secondary OutFlow Max=0.00 cfs @ 0.00 hrs HW=810.00' TW=0.00' (Dynamic Tailwater) 3=Spillway_Broad-Crested Rectangular Weir ( Controls 0.00 cfs)

2022_Ardmore Type I 24-hr _95th Rainfall=1.45", AMC=1
Prepared by Wallace Group Printed 2/17/2023
HydroCAD® 10.20-2f s/n 05444 © 2022 HydroCAD Software Solutions LLC Page 95 Pond LID D: Basin
Inflow
Outflow
Discarded
Primary
Secondary
Hydrograph
Time (hours)
727068666462605856545250484644424038363432302826242220181614121086420 Flow (cfs)
1 0
Inflow Area=3.790 ac
Peak Elev=814.33'
Storage=8,527 cf

1.78 cfs

0.01 cfs

0.01 cfs

0.00 cfs

0.00 cfs

2022_Ardmore Type I 24-hr _95th Rainfall=1.45", AMC=1
Prepared by Wallace Group Printed 2/17/2023
HydroCAD® 10.20-2f s/n 05444 © 2022 HydroCAD Software Solutions LLC Page 96 Summary for Link A: Outlet A
Inflow Area = 7.196 ac, 86.00% Impervious, Inflow Depth = 0.00" for _95th event Inflow = 0.00 cfs @ 0.00 hrs, Volume= 0.000 af
Primary = 0.00 cfs @ 0.00 hrs, Volume= 0.000 af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Link A: Outlet A
Inflow
Primary
Hydrograph
Time (hours)
727068666462605856545250484644424038363432302826242220181614121086420 Flow (cfs)
1 0
Inflow Area=7.196 ac

0.00 cfs

0.00 cfs

2022_Ardmore Type I 24-hr _95th Rainfall=1.45", AMC=1
Prepared by Wallace Group Printed 2/17/2023
HydroCAD® 10.20-2f s/n 05444 © 2022 HydroCAD Software Solutions LLC Page 97 Summary for Link B: Outlet B
Inflow Area = 2.798 ac, 83.10% Impervious, Inflow Depth = 0.00" for _95th event Inflow = 0.00 cfs @ 0.00 hrs, Volume= 0.000 af
Primary = 0.00 cfs @ 0.00 hrs, Volume= 0.000 af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Link B: Outlet B
Inflow
Primary
Hydrograph
Time (hours)
727068666462605856545250484644424038363432302826242220181614121086420 Flow (cfs)
1 0
Inflow Area=2.798 ac

0.00 cfs

0.00 cfs

2022_Ardmore Type I 24-hr _95th Rainfall=1.45", AMC=1
Prepared by Wallace Group Printed 2/17/2023
HydroCAD® 10.20-2f s/n 05444 © 2022 HydroCAD Software Solutions LLC Page 98 Summary for Link C: Outlet C
Inflow Area = 0.274 ac, 77.95% Impervious, Inflow Depth = 0.17" for _95th event Inflow = 0.03 cfs @ 9.94 hrs, Volume= 0.004 af
Primary = 0.03 cfs @ 9.94 hrs, Volume= 0.004 af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Link C: Outlet C
Inflow
Primary
Hydrograph
Time (hours)
727068666462605856545250484644424038363432302826242220181614121086420 Flow (cfs)

0.036

0.034

0.032

0.03 0.028

0.026

0.024

0.022

0.02 0.018

0.016

0.014

0.012

0.01 0.008

0.006

0.004

0.002
0 Inflow Area=0.274 ac

0.03 cfs

0.03 cfs

2022_Ardmore Type I 24-hr _95th Rainfall=1.45", AMC=1
Prepared by Wallace Group Printed 2/17/2023
HydroCAD® 10.20-2f s/n 05444 © 2022 HydroCAD Software Solutions LLC Page 99 Summary for Link D: Outlet D
Inflow Area = 3.790 ac, 73.64% Impervious, Inflow Depth = 0.00" for _95th event Inflow = 0.00 cfs @ 0.00 hrs, Volume= 0.000 af
Primary = 0.00 cfs @ 0.00 hrs, Volume= 0.000 af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Link D: Outlet D
Inflow
Primary
Hydrograph
Time (hours)
727068666462605856545250484644424038363432302826242220181614121086420 Flow (cfs)
1 0
Inflow Area=3.790 ac

0.00 cfs

0.00 cfs

PRELIMINARY DRAINAGE DESIGN REPORT
For

ARDMORE INDUSTRIAL
Ardmore Road, Paso Robles, California
WG Project Number:
0751-0005 Ardmore
February 21, 2023
Prepared by:

Wallace Group
612 Clarion Court
San Luis Obispo, CA 93401
805 544-4011
Job Number: 1493-0007

Ardmore Industrial – Preliminary Drainage Design Report February 21, 2023

Table of Contents
Certification ................................................................................................................................ 4 I. Project Background ................................................................................................................. 5 I.A. Project Description ........................................................................................................... 5 I.B. Existing Site Conditions .................................................................................................... 7 I.C. Existing Drainage Studies ................................................................................................ 8 I.D. Soil Characteristics .......................................................................................................... 8 I.E. Proposed Site Drainage ................................................................................................... 9 I.F. Purpose of Report ...........................................................................................................12 I.G. Regional Regulations ......................................................................................................13 I.H. Design Criteria ................................................................................................................13 II. Topographic Survey and Data Sources .................................................................................13 III. Hydrologic and Hydraulic Analysis .......................................................................................14 III.A. Hydrologic Analysis .......................................................................................................14 Land Use .......................................................................................................................15 Rainfall Depth and Distribution ......................................................................................16 Drainage Management Areas ........................................................................................16 Time of Concentration ...................................................................................................16 Peak Flow Analysis and Flood Control ..........................................................................17 III.B. Hydraulic Analysis .........................................................................................................17 III.C Safe Overland Conveyance Paths .................................................................................20 Outlet A .........................................................................................................................20 Outlet B .........................................................................................................................21 Onsite Runoff (C) ..........................................................................................................21 Outlet D .........................................................................................................................21 List of Figures
Figure 1. Project Location within the City of Paso Robles .......................................................... 5 Figure 2: Offsite Properties Exhibit – Ardmore Industrial ............................................................ 6 Figure 3. Ardmore Existing Site Drainage Patterns .................................................................... 7 Figure 4: Proposed Drainage Management Areas ..................................................................... 9 Figure 5: Outlet B for DMA B1 and DMA B2 ..............................................................................11 Figure 6: Onsite Runoff (C) for DMA C ......................................................................................11 Figure 7: Safe overland escape path for offsite run-on from the south ......................................18 Figure 8: 25-year Hydraulic Analysis for Bypass Culvert - Profile ..............................................19 Figure 9: 25-year Hydraulic Analysis for Bypass Culvert – Front View ......................................19 Figure 10: Safe Overland Escape Paths ...................................................................................20 List of Tables
Table 1: Comparison of Ardmore Industrial offsite watershed run-on ......................................... 8 Table 2: Pre-development Site Conditions ................................................................................10 Table 3: Post-development Site Conditions ...............................................................................10 Table 4: Hydrologic analysis methods by project drainage area ................................................14 Table 5. Pre-Development vs. Post-Development Hydrologic Analysis .....................................15 Table 6: Design Storm Event Data - SBUH ...............................................................................16 Table 7: Design Storm Event Data - Rational Method ...............................................................16 Table 8: Offsite Run-on Peak Flow Summary ...........................................................................18

Ardmore Industrial – Preliminary Drainage Design Report February 21, 2023

List of Appendices
Appendix A – Supporting Exhibits
• Existing Watersheds and Proposed Drainage Management Areas (DMA) Exhibits • Offsite Properties Exhibit
Appendix B – Excerpts from Design Standards and References • Geotechnical and soils documentation
• Site Infiltration data and Porchet Method conversion calculations • Pages from City of Paso Robles public work standards
• Time of Concentration & Rainfall data - County of San Luis Obispo Public Improvement Standards
• Rainfall data – NOAA Atlas 14, Volume 6, Version 2 excerpt (for Paso Robles, CA) Appendix C – Preliminary Drainage Design Calculations
• Existing and Proposed Hydrologic Calculations
• Existing and Proposed Land Use Data
• Time of Concentration Calculations
• HydroCAD Drainage Results – Existing Site
o 25-Year, 50-Year, and 100-Year Design Storms
• HydroCAD Drainage Results – Proposed Site
o 25-Year, 50-Year, and 100-Year Design Storms
• Ardmore Bypass Culvert analysis – 25-year and 100-year storm event Appendix D – Preliminary Storm Drain Facility Concepts
• ADS StormTech MC-3500 Chamber overview
• Roadside Bioretention concept

Ardmore Industrial – Preliminary Drainage Design Report February 21, 2023

Certification
Professional Engineer
This report was prepared by, or under the direction of the following Professional Engineer’s in accordance with the provisions of Section 6700 of the Business and Professions Code of the State of California.

DRAFT – FOR REVIEW ONLY
___________________________________
Tom Zehnder, PE C72702
Principal, Wallace Group

Ardmore Industrial – Preliminary Drainage Design Report February 21, 2023

I. Project Background
I.A. Project Description
The Ardmore project is a planned commercial development to be located in the City of Paso Robles, off of Ardmore Road just south of Union Road. The existing property is 14.06 acres of primarily undeveloped rural grassland with two agricultural structures. The southern portion of the site slopes gently to the west while the northern portion of the site gently slopes to the northeast corner. The current site plan design includes six commercial buildings, associated parking areas, interior courtyards and a new city-maintained road segment extending from Ardmore Road through the project to the eastern boundary of the site. Proposed storm drain facilities for this project include five separate storm drain pipe networks, three underground infiltration and detention chambers, and one surface infiltration and detention basin.

As a project located within the city limits of Paso Robles, this report is intended to support issuance of entitlement by the City of Paso Robles. A project map is shown below in Figure 1 and the Offsite Properties Exhibit is shown in Figure 2, for reference.

Figure 1. Project Location within the City of Paso Robles Ardmore
Project Site
Hwy 46
Downtown
Paso Robles Union Road

Ardmore Industrial – Preliminary Drainage Design Report February 21, 2023

Figure 2: Offsite Properties Exhibit – Ardmore Industrial

Ardmore Industrial – Preliminary Drainage Design Report February 21, 2023

I.B. Existing Site Conditions
The Ardmore Project is part of an existing 106-acre watershed that drains north towards Union Road where it is collected by the City of Paso Robles’ storm drain system. This project is located at the upstream end of this greater existing watershed encompassing approximately 69 acres of the project drainage area. The northwest corner of the site, which is about 3.27 acres of the project area, drains offsite to the northeast towards Union Road and Huer Huero Creek.

The project drainage area consists of four existing major watersheds that each drain to different discharge locations (See Appendix A for the Existing Watershed Exhibit). Existing watershed #1 (EX1 offsite) includes approximately 57 acres of undeveloped, rural grassland that flows onto the site. Existing watershed #1 (EX1 onsite) includes 7.20 acres of undeveloped onsite area.

Stormwater from this drainage area flows through shallow, natural drainage paths to two existing 24” storm drain pipe inlets along the west project boundary located on the adjacent Spurr property (Outlet A). Existing Watershed #2 (EX2) drains to an existing culvert inlet, conveying it beneath Ardmore Road to the adjacent Daniels Woodlands property (Outlet B).

Existing Watershed #3 (EX3) consists of the northeast corner of the site with stormwater flowing offsite through shallow, natural drainage paths towards Union Road and Huer Huero Creek (Outlet D). Existing Watershed #4 (EX4) is the smallest existing project watershed. Stormwater from this area flows northwest towards Ardmore Road where it is collected in a natural roadside swale and conveyed north towards Union Road (Onsite Runoff (C)).

Figure 3. Ardmore Existing Site Drainage Patterns
EX3 DRAINS NORTHEAST

TOWARDS UNION ROAD/

HUER HUERO CREEK
Project Boundary
EX1, EX2 & EX4 DRAIN NORTHWEST

TO UNION ROAD LOW POINT
EX2

Ardmore Industrial – Preliminary Drainage Design Report February 21, 2023

I.C. Existing Drainage Studies
Several existing drainage studies have been completed for the surrounding offsite properties adjacent to the Ardmore Industrial site. These studies are listed in Section I.F. of this report as additional references.

During the Ardmore preliminary drainage design, the existing offsite hydrology was analyzed and compared to the drainage studies of the surrounding properties (Spurr and Daniels Woodland), both prepared by Roberts Engineering. This was to review the offsite run-on to the Ardmore site and identify the pre-developed drainage condition for the “EX1 offsite” watershed – also called “Spurr (Area B)” within the Roberts Engineering reports. This existing watershed, after crossing the Ardmore site, discharges to an existing storm drain inlet (Outlet A in this report) that is located on the adjacent Spurr property, to the west. This existing inlet will remain and serve as the proposed discharge location for DMA A of Ardmore Industrial, following historic drainage patterns.

Table 1 shows the comparison of 100-year peak flows for this existing, offsite watershed. This preliminary drainage report has been prepared using the assumption that the offsite run-on from “EX1 offsite” in the 100-yr storm event is 76.97 cfs – which is more conservative than previous studies. We also believe that the County of San Luis Obispo standard time of concentration equation (see detail H-2) is more representative of this watershed.

Table 1: Comparison of Ardmore Industrial offsite watershed run-on

I.D. Soil Characteristics
A geotechnical engineering soils report for the Ardmore Project has been prepared by Beacon Geotechnical, Inc (dated October 12, 2022).

Based on this geotechnical report, soils across the site are comprised of mostly very silty clayey sands overlain by layers of multiple silty clayey sands with gravel. Soil expansion capabilities were determined to be low, and groundwater was not encountered in any of the site borings to a depth of 20 feet. Twelve different infiltration borings and tests were completed across the site with infiltration rates recorded range from 1.50 in/hr. to 5.00 in/hr. and are directly applicable to the design of infiltration trenches and similar deep facilities. For shallow facilities with more bottom area than sidewall area, the Porchet conversion is applied to the test data to determine the applicable infiltration rate. Using the Porchet conversion method, infiltration rates ranged from 0.07 to 0.70 in/hr.

Offsite Area * Report Total Area in
Report (ac)
Calculated
tc (min) tc Method
Hydrology
Calculation
Method
100-yr Flow
(cfs)
Spurr (Area B)
Roberts, Spurr/
Daniels Wood
Reports (9/8/2020)

59.00 35.00 FAA method Rational 44.00
EX1 offsite
Wallace Group,
Ardmore Industrial
Prelim Report
(2/2023)

57.27 11.04
SLO County
Equation Rational 76.97
* These two areas represent the same drainage watershed but have different names in different drainage reports

Ardmore Industrial – Preliminary Drainage Design Report February 21, 2023

NRCS web soil data identifies the soils as primarily Hydrologic Soil Group C (mostly clay and loams), which is associated with generally moderate-to-low infiltration rates and is usually due to the existence of clays within the soil complexes.

See Appendix B for excerpts from the geotechnical engineering report, NRCS web soil survey, and additional data related to onsite infiltration.

I.E. Proposed Site Drainage
The proposed site plan will be divided into five drainage management areas (DMAs) while following historic drainage patterns and discharge locations for stormwater runoff. See Figure 4 below, and Appendix A for the Proposed Drainage Management Areas Exhibit.

Figure 4: Proposed Drainage Management Areas
The proposed site plan consists primarily of impervious surface areas such as large commercial buildings, associated parking areas, a new city-maintained road extension of Ardmore Road east through the project site, and frontage improvements along the east side of the existing Ardmore Road. Tables 2 and 3 show the pre-development vs. post-development values for land use types associated with the proposed site plans.

DMA A
DMA B1 DMA B2
DMA D
DMA C

Ardmore Industrial – Preliminary Drainage Design Report February 21, 2023

Table 2: Pre-development Site Conditions
Table 3: Post-development Site Conditions
With limited surface area available for pervious land uses, the current drainage design will utilize surface bioretention swales, underground gravel facilities, and underground ADS StormTech chamber systems to meet post-construction stormwater requirements (PCRs) and peak flow management requirements. Further information on design calculations can be found in Section III of this report. See Appendix D for conceptual details of these proposed drainage systems.

DMA A is designed to drain runoff from 7.20 acres of mixed commercial land and new roadway area towards existing Outlet A along the west project boundary. Stormwater from the mixed commercial area will be directed to an underground StormTech chamber system via a storm drain network. This StormTech chamber system is designed to retain and infiltrate smaller storm events while detaining larger events to meter project runoff to Outlet A following historic patterns. The new right-of-way extension of Ardmore Road will drain to roadside bioretention facilities with underground gravel chambers. Runoff from larger storm events, not exceeding historic peak flow patterns will be directed to the existing Outlet A.

Existing Outlet A will also receive offsite run-on from approximately 57 acres of undeveloped, rural grassland that flows onto the site from the south and then is routed via two proposed 36” HDPE storm drain culverts, following historic drainage patterns.

DMA B1 is designed to drain runoff from 1.60 acres of mixed commercial land and the east side of Ardmore Road towards existing Outlet B along the west project boundary. The existing storm drain pipe will be maintained while the existing inlet will be replaced with a standard curb inlet connected to the proposed storm drain system associated with DMA B1. Roadside bioretention swales with underground gravel chambers will manage stormwater runoff from Ardmore Road while onsite runoff will be conveyed to an underground StormTech chamber system where historic peak flow patterns will be directed to Outlet B. See Figure 5 below for a detailed diagram of Outlet B.

DMA B2 is designed to drain runoff from 1.20 acres of mixed commercial land towards Outlet B along the west project boundary. Onsite runoff will be conveyed to an underground StormTech chamber system where historic peak flow volumes will be directed to Outlet B via a new storm drain pipe that crosses Ardmore Road. This new connection will tie in to an existing storm drain manhole just east of Ardmore Road on the Daniels Woodlands property driveway entrance. The combined stormwater runoff of DMA B1 and DMA B2 has been designed to be less than the existing drainage design volume of the Daniels Woodlands storm drain network, by Roberts Engineering. For more information of these calculations and references to the Roberts Engineering report, see Appendix C.

Land Type Total Area (sf) % of Total Area
Impervious (Imp) 3,223 0.5%
Pervious (P) 609,141 99.5%
Total Area 612,364 14.06 100.0%
Total Area (ac)

0.07 13.98
Land Type Total Area (sf) % of Total Area
Impervious (Imp) 501,730 81.9%
Pervious (P) 110,633 18.1%
Total Area 612,363 100.0%
Total Area (ac)

2.54 11.52

14.06

Ardmore Industrial – Preliminary Drainage Design Report February 21, 2023

Figure 5: Outlet B for DMA B1 and DMA B2
DMA C is designed to drain runoff from 0.27 acres of onsite mixed commercial land and the east side of Ardmore Road towards the northwest corner of the project. A majority of stormwater runoff from DMA C will be directed into a proposed roadside bioretention swale with underground gravel storage. Following historic drainage patterns and runoff volumes, excess flow from DMA C will be directed offsite along the east side of Ardmore Road (see Figure 6).

This designed onsite runoff with be flow northward towards Union Road via an existing roadside swale. See Appendix C for stormwater calculations of DMA C and the Onsite Runoff (C) location.

Figure 6: Onsite Runoff (C) for DMA C
Exist. SD manhole located on
Daniels Woodlands property
New SD pipe connection
(from DMA B2)
Exist SD pipe across
Ardmore Rd. (from DMA B1)

Ardmore Industrial – Preliminary Drainage Design Report February 21, 2023

The northeast portion of the project site consists of DMA D which drains 3.79 acres of mixed commercial land towards the northeast and Union Road. This drainage area is connected to a separate offsite watershed that flows directly towards Huer Huero Creek, unlike the previously discussed project DMAs A, B1, B2, and C which drain to a separate low point along Union Road. Stormwater runoff from DMA D will be directed to a surface detention basin at the northeast corner of the project site. This basin will also have retention and infiltration capabilities to manage smaller storm events while onsite runoff from larger events will be metered offsite by a proposed box inlet (Outlet D) and concrete spillway towards the northeast, following historic drainage patterns.

Overall, it is expected that the combined performance of these proposed storm drain detention systems across the project will decrease stormwater run-off from the site compared to predevelopment drainage conditions. Historic discharge locations will also be maintained, and it expected that appropriate erosion control measures will be implemented to minimize downstream stormwater runoff impacts.

I.F. Purpose of Report
The purpose of this preliminary report is to assess the onsite drainage conditions and document the preliminary drainage design for the Ardmore Industrial project in support of the preliminary grading plans. This report provides relevant data and calculations to meet the requirements set out by the City of Paso Robles and County of San Luis Obispo Public Improvement Standards.

This preliminary report will address the following subjects related to Ardmore project:
• Drainage design standards
• Existing drainage patterns and proposed drainage management areas • Hydrologic methodology and hydraulic calculations
• Peak flow management and flood control
• Safe overland conveyance paths
The following future reports are anticipated:
• Final Drainage Design Report
• Final Stormwater Control Plan
Additional references :
• Daniels Woodland Commercial Facility drainage report, by Roberts Engineering Inc, dated 3/15/19 and revised 9/8/20.
• Stormwater Control Plan for Daniels Woodland Commercial Complex, by Roberts Engineering Inc, dated 3/13/19.
• Stormwater Quality Control Plan for Spurrco Commercial Development Project, by Roberts Engineering Inc, dated 5/14/18.
• Ardmore Road Public Improvement Plans (Parcel Map PR 18-0067), by Roberts Engineering Inc, record drawings dated 2/12/20.

Ardmore Industrial – Preliminary Drainage Design Report February 21, 2023

I.G. Regional Regulations
The Admore project is primarily subject to the City of Paso Robles Standard Specification and Details as it lies within the City of Paso Robles jurisdiction. Where any guidance is not found within the City of Paso Robles standards, designs for this project will then follow County of San Luis Obispo Public Improvement Standards.

This project is also subject to the Stormwater Post Construction Requirements #1 - # 4 (PCRs).

A separate preliminary stormwater control plan will be prepared to review and assess the current site plan as it relates to PCR compliance.

This project does not include any impacts that would involve other governing jurisdictions such as the California Department of Fish and Wildlife (CDFW), and the Federal Emergency Management Agency (FEMA). This project does not impact waters within the jurisdiction of the US Army Corps of Engineers.

I.H. Design Criteria
The design standards used for the Ardmore drainage facilities are summarized below.

1. Peak Flow Management and Flood Control (City of Paso Robles and County of SLO) a. No significant flow increase from the existing condition for the 2-year through 100-year storms. Historic stormwater drainage patterns will be maintained.

2. Swales and open channels (City of Paso Robles)
a. 25-year storm event volume with 1-ft of freeboard
b. 100-year storm event volume shall be contained within the banks or within channel easement.

3. Closed Conduits (City of Paso Robles)
a. 25-year design storm event.
b. 100-year storm event volume shall be contained within the banks or within channel easement of secondary, safe overland escape path.

4. Overland Conveyance (City of Paso Robles)
a. Sump conditions must have safe overflow path for 100-year flow.

5. Stormwater Quality (City of Paso Robles, County of SLO and PCRs) a. Comply with Central Coast Regional Water Quality Control Board PostConstruction Stormwater Requirements #1 - #4.

II. Topographic Survey and Data Sources
The following data sources were utilized for the analysis presented in this report:
• Topographic survey prepared by North Coast Engineering, dated 11-09-2022 and 2-2-2023.
• Site visits and field observations

Ardmore Industrial – Preliminary Drainage Design Report February 21, 2023

III. Hydrologic and Hydraulic Analysis
III.A. Hydrologic Analysis
A hydrologic analysis was performed as described in the City of Paso Robles Standard Specifications and Details, evaluating peak stormwater flows from each existing watershed and DMA (see Table 4). The primary analytical method used for most project drainage areas was the Santa Barbara Urban Hydrograph (SBUH) Method in the HydroCAD software. A separate Rational Method calculation was used for peak flow analysis of the “EX1 (offsite)" existing watershed due to the offsite location and undeveloped land use. It is our opinion that the Rational Method produced more consistent and realistic peak flow values compared to the SBUH Method. Section I.C of this report provides more information on the hydrologic results of “EX1 (offsite)” compared to previous drainage studies.

Table 4: Hydrologic analysis methods by project drainage area The preliminary drainage design of Ardmore Industrial utilizes the combined performance of surface bioretention swales with underground gravel retention, underground retention and detention (StormTech) chamber systems, and a surface basin with retention and detention capabilities. Each DMA will be connected to an existing drainage discharge location preserving historic drainage patterns with minimal stormwater diversion. Post-developed project peak flows for 2-year through 100-year storm events will be less than or equal to pre-developed peak flow conditions. Offsite run-on to the project from the south will be conveyed through a bypass culvert to an existing discharge location (Outlet A), following historic drainage patterns.

A summary of the existing vs. proposed hydrologic conditions is presented in Table 5. For further information on the overall hydrologic analysis see Appendix C.

EX1 (offsite) * Rational Method DMA A SBUH in HydroCAD
EX1 (onsite) SBUH in HydroCAD DMA B1 SBUH in HydroCAD
EX2 **
Peak flow data referenced from
2019 Daniels Comm. drainage
report by Roberts Eng. -- these
values were more conservative
(less than) the peak flows
calculated by Wallace Group.

DMA B2 SBUH in HydroCAD
EX3 SBUH in HydroCAD DMA C SBUH in HydroCAD
EX4 SBUH in HydroCAD DMA D SBUH in HydroCAD
Existing/ Pre-developed Hydrology Proposed/ Post-developed Hydrology

Ardmore Industrial – Preliminary Drainage Design Report February 21, 2023

Table 5. Pre-Development vs. Post-Development Hydrologic Analysis

Land Use
Project land uses were delineated into pervious and impervious areas. Existing land uses consist of undeveloped rural grassland with good vegetation cover and two agricultural structures across 71.33 acres of drainage area. The proposed project area of 14.06 acres will consist of a mixed commercial development, with impervious surfaces planned for approximately 85% of the site. The project minimizes excessive land disturbance and site improvements given the required project conditions, with pervious/ landscaped areas resulting in 18% of the proposed site (See Table 3).

For project calculations within the HydroCAD software, impervious areas were assigned a runoff curve number (CN) of 98, and pervious/ landscaped areas were assigned a CN of 79 (landscaped, 50-75% Grass cover, Fair, Hydrologic Soil Group C) following the standard US Natural Resources Conservation Service (NRCS) runoff curve number method.

Pre-Dev.

Total Area
(ac)
Post-Dev.

Total Area
(ac)
Storm Pre-Developed
Flow, Q (cfs)
Post-Developed
Flow, Q (cfs)
95th - -
2 YR 32.51 31.75
10 YR 61.76 59.90
25 YR 72.83 71.33
50 YR 85.55 83.41
100 YR 93.67 90.48
95th Data Unknown -
2 YR 1.02 0.04
10 YR 2.11 0.59
25 YR 2.46 1.65
50 YR 2.97 2.53
100 YR 3.54 3.42
95th 0.01 0.03
2 YR 0.15 0.07
10 YR 0.74 0.12
25 YR 1.17 0.15
50 YR 1.52 0.18
100 YR 1.89 0.20
95th - -
2 YR 0.56 -
10 YR 2.94 0.54
25 YR 4.70 1.37
50 YR 6.11 3.36
100 YR 7.62 6.81

71.33 71.33

3.27 Drainage Area Subtotal

64.43 64.46

2.80 0.27

3.79 2.82

0.80 Outlet D
Onsite Runoff (C)
Outlet B
Outlet A
Outlet Location

Ardmore Industrial – Preliminary Drainage Design Report February 21, 2023

Rainfall Depth and Distribution
Average annual rainfall data used in SBUH calculations was derived from the NOAA Atlas 14, Volume 6, Version 2 for the project location within Paso Robles, California (Table 6, below).

Table 6: Design Storm Event Data - SBUH
Average annual rainfall data used in Rational Method calculations was derived from County of San Luis Obispo standard details H-1 through H-4 (2022) for the project location within Paso Robles, California (Table 7, below).

Table 7: Design Storm Event Data - Rational Method
See Appendix B for selected pages of rainfall data from each respective jurisdictional agency.

Drainage Management Areas
As described earlier in the Proposed Site Drainage section, five drainage management areas (or DMAs) were delineated based upon the preliminary grading design for the Ardmore project.

Appendix A shows the delineation of the existing and proposed Ardmore DMAs.

Time of Concentration
The time of concentration (Tc) for each existing watershed and drainage management area was calculated using the County of San Luis Obispo standard detail H-2 (2022) time of concentration equation. A minimum time of concentration of 6 minutes was used in the calculations of this report, as standardized by the City of Paso Robles Section V-1.B rainfall chart.

Detailed time of concentration calculations for each existing watershed and drainage management are shown in Appendix C.
95th 1.45 inches
2 YR 2.14 inches
10 YR 3.74 inches
25 YR 4.70 inches
50 YR 5.42 inches
100 YR 6.16 inches
* See NOAA Atlas 14 Rainfall data (24-hr
storm duration)
Rainfall Event Data
2 YR 1.30 in/ hr
10 YR 2.30 in/ hr
25 YR 2.60 in/ hr
50 YR 3.00 in/ hr
100 YR 3.20 in/ hr
Rainfall Event Data
* See 2022 County of San Luis Obispo
Public Improvement Standards H-4, Table 2

Ardmore Industrial – Preliminary Drainage Design Report February 21, 2023

Peak Flow Analysis and Flood Control
Peak flows were calculated primarily using the Santa Barbara Urban Hydrograph (SBUH) Method analysis through the HydroCAD software for each existing watershed and proposed DMA. See Table 4 for exceptional cases related to this project. Summaries of the hydrologic analyses and corresponding results are included in Appendix C.

The proposed underground retention facilities, surface detention basin, and underground detention chambers will combine to meet all peak flow management requirements for the 2-year through 100-year storm events, as required by the City of Paso Robles and Central Coast Regional Water Quality Control Board Post-Construction Stormwater Requirements #3 and #4.

III.B. Hydraulic Analysis
Bypass Culvert
A bypass culvert consisting of two 36” HDPE storm drain pipes is proposed along the south and southwestern side of the project to collect and convey offsite run-on to existing Outlet A (see Table 8), following historic drainage patterns. These parallel culvert pipes will combine to have the capacity to convey the 2-year through 100-year storm events but will be outlet-controlled due to the limited inlet capacity of existing Outlet A. See Section I.F of this report for the additional references containing the calculations for existing Outlet A, completed by Roberts Engineering.

It is expected that stormwater will pond at existing Outlet A to a maximum elevation of 823.35’ in events larger than the 2-year storm due to limited inlet capacity, following historic drainage conditions. Due to this drainage condition at Outlet A, a constant tailwater elevation of 823.35’ has been included in the analysis of the Ardmore bypass culvert. Stormwater ponding above 823.35’ at Outlet A will escape overland to the west and flow towards Ardmore Road. See Section III.C of this report for more information on safe overland escape paths. This water surface elevation will also likely cause variable ponding to occur at the bypass culvert inlet along the southern project boundary.

A safe overland escape path for stormwater upstream of the bypass culvert is proposed along the southern property boundary (see Figure 7). As onsite grading will conform to existing offsite topography at the property line, the proposed safe overland drainage path will have a crest elevation of 823.5’. Due to the combined effects of the bypass culvert tailwater condition and the safe overland escape path crest, further ponding of stormwater onto the adjacent southern property can be expected up to an elevation of 824.5’ in the 100-year storm event.

Permanent erosion control and energy dissipation is planned to be designed at the downstream end of the bypass culvert near existing Outlet A. These calculations will be included in the final drainage design report, to be completed at a later date.

Ardmore Industrial – Preliminary Drainage Design Report February 21, 2023

Figure 7: Safe overland escape path for offsite run-on from the south Table 8: Offsite Run-on Peak Flow Summary
A hydraulic analysis of the bypass culvert was performed using the HY-8 software. Summary images of the hydraulic analysis are presented in Figures 8 and 9. See Appendix C for detailed, hydraulic calculations for the bypass culvert.

DMA Outlet
Location
Total Area
(sf)
Total Area
(ac) C
Land Type
Description Storm Intensity, I
(in/hr)
Flow, Q
(cfs)
2 YR 1.30 31.27
10 YR 2.30 55.32
25 YR 2.60 62.54
50 YR 3.00 72.16
100 YR 3.20 76.97
Outlet A
(Exist.
double 24"
SD pipes)
EX1
(offsite) 2,494,621 57.27 0.42

OFFSITE
RUN-ON
Undeveloped.

Rural grassland/
open space, few
trees
Crest Elev. = 823.5’

Ardmore Industrial – Preliminary Drainage Design Report February 21, 2023

Figure 8: 25-year Hydraulic Analysis for Bypass Culvert - Profile Figure 9: 25-year Hydraulic Analysis for Bypass Culvert – Front View

Ardmore Industrial – Preliminary Drainage Design Report February 21, 2023

III.C Safe Overland Conveyance Paths
The proposed, preliminary Ardmore grading has been designed to safely direct overland conveyance of 100-year storm events away from proposed structures and downstream following historic drainage patterns. Below is a summary of each Ardmore project discharge location.

Figure 10 shows the different overland conveyance paths for each of project discharge location.

Figure 10: Safe Overland Escape Paths
Outlet A
Outlet A is comprised of two existing 24” storm drain pipes. This outlet is expected to receive stormwater flows from three contributing sources: undeveloped offsite run-on from the south via the proposed bypass culvert, onsite runoff from StormTech chambers in DMA A, and a second storm drain network in DMA A. These flows converge at a low point where the existing Outlet A is located. The existing condition and as-built construction status of this existing storm drain inlet is not completely known at the time of this report. Wallace Group was provided a design invert elevation of 816.84’ for existing Outlet A by MBS Land Surveys. Further review of Outlet A will likely be necessary to fully analyze the actual, existing storm drain infrastructure.

In large storm events, or where the two existing 24” storm drain pipes do not perform as designed by Roberts Engineering, it is expected that this area will flood to an elevation of 823.35’. The overland escape path will be northwest across the Spurr property towards Ardmore Road where three stormwater basins will capture and convey flow westward into the downstream storm drain system. This overland escape path aligns with existing, historic drainage patterns.

ARDMORE

ROAD OUTLET A OUTLET B

OUTLET D
Onsite
Runoff (C)

Ardmore Industrial – Preliminary Drainage Design Report February 21, 2023

Outlet B
Outlet B is an existing storm drain manhole just east of Ardmore Road designed as a part of the Daniels Woodlands project (see Figure 5, above). Outlet B is proposed to receive stormwater from an existing 12” storm drain pipe (from DMA B1) and a new storm drain pipe connection (from DMA B2). This existing storm drain network conveys stormwater westward through the Daniels Woodlands property where it discharges into a perimeter bypass swale. Stormwater will then be conveyed around the north side of the Daniels Woodlands property towards the downstream drainage channel that flows north to Union Road.

The proposed DMAs B1 and B2 have been designed to maintain this overland escape path following historic conditions and in accordance with the existing drainage design of the Daniels Woodlands project by Roberts Engineering.

Onsite Runoff (C)
Historic drainage patterns of the northwest corner of the Ardmore Industrial site show topography that directs stormwater northwest towards Ardmore Road. Once collected along the east side of Ardmore Road, stormwater continues to flow north and discharges into an existing roadside swale. DMA C has been designed to follow this historic drainage pattern, directing excess stormwater away from developed areas of Ardmore Industrial and onto Ardmore Road.

Outlet D
Proposed Outlet D consists of a box inlet with riser within the DMA D stormwater basin. This outlet has been designed to direct stormwater runoff from the area to the northeast, following historic drainage patterns and volumes. For excess stormwater runoff from DMA D into the proposed basin, a spillway has been proposed above the designed 100-year water surface elevation. Energy dissipation and permanent erosion control measures will be necessary to minimize downstream impacts of the concentrated flow from the proposed pipe outlet and the basin spillway.

APPENDIX A
Appendix A – Supporting Exhibits
• Existing Watersheds and Proposed Drainage Management Areas (DMA) Exhibits • Offsite Properties Exhibit

822.5 inv 12" 18" 821.0 inv
CO

WL WL GAS GAS

UTL UTL
818
821 821
830
840
824
826
828 832
834
836
838
830
840
850
860 870 880
890
900
910
920
930
840
850
860
870
880
890
900
910
920
930
940
950 960 970
980
780
790
800
840
830
820
810
760
770
758 762 764
766
768
772
774
776
776
776
778
815
820
825
830
825
824
826
827
828
829
820
820
825
830
825
830
835 832
832
826 825
827
828
828
826
825
824
823
826
826
837
795
800
805
810
815
820
825
830
770
780
790
800
810
820
830
840
840
850
850
860
860
870
870
880
880
823
825
824
826
827
826
N
0 (IN FEET)

GRAPHIC SCALE
60 120 240
1 IN = 120 FT

ORIGINAL SCALE IS IN INCHES

FOR REDUCED PLANS
T 805 544-4011 F 805 544-4294
612 CLARION COURT
SAN LUIS OBISPO, CA 93401

DATE SIGNED

SIGNATURE
www.wallacegroup.us

PLANNING

CIVIL AND TRANSPORTATION ENGINEERING

CONSTRUCTION MANAGEMENT

LANDSCAPE ARCHITECTURE

MECHANICAL ENGINEERING

PUBLIC WORKS ADMINISTRATION

SURVEYING / GIS SOLUTIONS

WATER RESOURCES
0 1 2 3
DESIGNERS:

DRAWING NO.

DATE:

DRAWN BY:

JOB #:

OF
1 2 3 4
A
B
C
D
1 2 3 4
5 5
Copyright © Wallace Group, a California
Corporation. All rights reserved. Copies of this
drawing shall have this notice.

These plans and specifications, and the ideas and
designs incorporated herein, are instruments of
service prepared for the construction of work shown
hereon and shall not be used in whole or in part for
any other project without written authority of Wallace
Group, a California Corporation.
®
2009 COVELOP ARDMORE PROJECT DEVELOPMENT
1 12/06/2022
751-005

CD/ ZKP
ZKP

SHEETEXISTING WATERSHED EXHIBIT
1 FILE NAME: 2022_ARDMORE_DRAINAGE MANAGEMENT AREAS.DWG

ARDMORE ROAD

EXISTING CULVERT INLET
(TO BE REPLACED)
EX1 (offsite)
AREA = 2,494,621 SF
AREA = 57.27 AC
EX3
AREA = 142,459 SF
AREA = 3.27 AC
EX4
AREA = 34,918 SF
AREA = 0.80 AC

ARDMORE ROAD

UNION ROAD
EXISTING DBL. 24" STORM

DRAIN PIPE AT ADJACENT

SPURR PROPERTY
LEGEND:

ARDMORE PROJECT BOUNDARY

EXISTING WATERSHED BOUNDARY
EX2
AREA = 122,877 SF
AREA = 2.82 AC

EXISTING

AGRICULTURAL

STRUCTURES TO
BE REMOVED.

THOMAS K. ZEHNDER

C I V I L
No. 72702

NOT FOR CONSTRUCTION

FOR PLAN REVIEW ONLY
AL
A T T
S
OF E C
A

O N R I F
I

REGISTERED PROFESSIONA L ENGINE
R
EX1 (onsite)
AREA = 312,111 SF
AREA = 7.17 AC

EXISTING ONSITE
RUNOFF (FROM EX4)

NORTHWARD ALONG
ARDMORE ROAD.

EXISTING ONSITE

SURFACE RUNOFF (FROM
EX3) TO THE NORTHEAST.

822.5 inv 12" 18" 821.0 inv SS SS SS SS

SS SS SS SS SS

SS SS SS SS SS SS

SS SS SS SS

SD SD SD SD SD
SD
SD SD

SD SD SD
SD
SD

SD SD SD
SD
SD
SD

WL WL WL WL WL WL WL CO FIRE
FIRE

FIRE FIRE FIRE FIRE FIRE
FIRE

GAS GAS GAS GAS GAS GAS GAS

UTL UTL UTL UTL UTL UTL SS WL WL WL WL WL

FIRE FIRE FIRE

FIRE FIRE FIRE FIRE FIRE

FIRE FIRE FIRE
1 2
3 4
5 6
821
821
815
820
825
830
825
824
826
827
828
829
820
820
825
830
825
830
835 832
832
825
826
827
828
828
825
824
823
826
826
826
837
820
825
830
823
825
824
826
827
826
825
826
825
826
818
825
821 820 819
822
825
824
826
827
827
823
827
828
828 822
828
829
828829 825 826 827
830
829
829
815
814
820
828
827
826
825
824
823 825 820
827
828
830
830
829
829
827
827
826
827
828
833
826
827
828
829
830
829
831 829 829 828828 828 827 829829
825
825
824
826
826
827
827 828 828 829 829
N
0 (IN FEET)

GRAPHIC SCALE
40 80
1 IN = 40 FT
20 ORIGINAL SCALE IS IN INCHES

FOR REDUCED PLANS
T 805 544-4011 F 805 544-4294
612 CLARION COURT
SAN LUIS OBISPO, CA 93401

DATE SIGNED

SIGNATURE
www.wallacegroup.us

PLANNING

CIVIL AND TRANSPORTATION ENGINEERING

CONSTRUCTION MANAGEMENT

LANDSCAPE ARCHITECTURE

MECHANICAL ENGINEERING

PUBLIC WORKS ADMINISTRATION

SURVEYING / GIS SOLUTIONS

WATER RESOURCES
0 1 2 3
DESIGNERS:

DRAWING NO.

DATE:

DRAWN BY:

JOB #:

OF
1 2 3 4
A
B
C
D
1 2 3 4
5 5
Copyright © Wallace Group, a California
Corporation. All rights reserved. Copies of this
drawing shall have this notice.

These plans and specifications, and the ideas and
designs incorporated herein, are instruments of
service prepared for the construction of work shown
hereon and shall not be used in whole or in part for
any other project without written authority of Wallace
Group, a California Corporation.
®
2023 COVELOP ARDMORE PROJECT DEVELOPMENT
1 2/14/2023
751-005

CD/ ZKP
ZKP

SHEETPROPOSED DRAINAGE MANAGEMENT AREAS
1 FILE NAME: 2022_ARDMORE_DRAINAGE MANAGEMENT AREAS.DWG

OUTLET B

PROPOSED CONNECTIONS TO

EXISTING DANIEL WOODLANDS
PROPERTY STORM DRAIN SYSTEM.

ARDMORE ROAD

OUTLET A
EXISTING DBL. 24" STORM DRAIN PIPE AT

ADJACENT SPURR PROPERTY (TO REMAIN)
LEGEND:

ARDMORE PROJECT BOUNDARY

PROPOSED DRAINAGE MANAGEMENT AREA (DMA)

BOUNDARY

PROPOSED DRAINAGE MANAGEMENT AREA (DMA)
(DRAINS OFFSITE OVER SURFACE)

BIORETENTION WITH UNDERGROUND GRAVEL TRENCH ARDMORE ROAD DMA C
AREA = 11,941 SF
AREA = 0.27 AC
DMA A
AREA = 313,474 SF
AREA = 7.20 AC
DMA B1
AREA = 69,586 SF
AREA = 1.60 AC
DMA B2
AREA = 52,287 SF
AREA = 1.20 AC
DMA D
AREA = 165,076 SF
AREA = 3.79 AC

OUTLET D

PROPOSED RETENTION BASIN WITH METERED
OUTLET STRUCTURE. FLOW DIRECTED TO
NORTHEAST FOLLOWING HISTORIC PATTERNS.

PROPOSED UNDERGROUND ADS
STORMTECH MC-3500 CHAMBERS
(PORCHET INFIL. RATE = 0.20 IN/HR)

PROPOSED SAFE OVERLAND

ESCAPE PATH FOR OFFSITE RUN-ON

PROPOSED STORMWATER CHANNEL

OF OFFSITE RUN-ON INTERCEPT

PROPOSED UNDERGROUND ADS
STORMTECH MC-3500 CHAMBERS
(PORCHET INFIL. RATE = 0.20 IN/HR)
THOMAS K. ZEHNDER

C I V I L
No. 72702

NOT FOR CONSTRUCTION

FOR PLAN REVIEW ONLY
AL
A T T
S
OF E C
A

O N R I F
I

REGISTERED PROFESSIONA L ENGINE
R

PROPOSED ROADSIDE

BIORETENTION SWALES

PROPOSED ROADSIDE

BIORETENTION SWALES

PROPOSED ROADSIDE

BIORETENTION SWALE

PROPOSED BIORETENTION TRENCH AREA
(PORCHET INFIL. RATE = 0.07 IN/HR)

PROPOSED UNDERGROUND ADS
STORMTECH MC-3500 CHAMBERS
(PORCHET INFIL. RATE = 0.19 IN/HR)

ONSITE RUNOFF (C)

RUNOFF FLOWS TO NORTH ALONG EAST SIDE OF
ARDMORE ROAD TOWARDS EXIST. ROADSIDE SWALE.

PROPOSED DOUBLE 30" HDPE

STORM DRAIN CULVERT FOR

OFFSITE RUN-ON BYPASS

T 805 544-4011 SAN LUIS OBISPO, CA 93401
612 CLARION COURT
www.wallacegroup.us F 805 544-4294
DRAWING :

DRAWN BY:

JOB No. :

DATE :

SCALE : ®

EXHIBIT

OFFSITE PROPERTIES

ARDMORE PROJECT SITE

PASO ROBLES, CA
751-005

OFFSITE PROPS
ZKP
DEC 6, 2022
1" = 300'
N
9 SPURR AREA A - WEST

SPURR AREA B - EAST

ARDMORE ROAD - CASE FRONTAGE

ARDMORE ROAD - SPURR FRONTAGE

ARDMORE ROAD - DANIELS FRONTAGE

FLOW DIRECTION
DANIELS WOODLAND 24' WIDE BIOSWALE
1 2
3 4
5 6
7 8

ARDMORE ROAD - DANIELS FRONTAGE

TATE PROPERTY

CASE PROPERTY

DANIELS WOODLAND

UNION ROAD SAFETY & TRAINING CENTER

AUTOCRAFT

SOUTH UNION ROAD
1 2
3 4
5 6
7 8
9 10
11 12
10 11
12 HYDROLOGY BY

ROBERTS

ENGINEERING

UNION ROAD

ARDMORE ROAD ARDMORE ROAD

ARDMORE

INDUSTRIAL
ARDMORE IND.

PROJECT SITE

ARDMORE EXIST

WATERSHEDS

UNION ROAD

LOW-POINT

APPENDIX B
Appendix B – Excerpts from Design Standards and References • Geotechnical and soils documentation
• Site Infiltration data and Porchet Method conversion calculations • Pages from City of Paso Robles public work standards
• Time of Concentration & Rainfall data - County of San Luis Obispo Public Improvement Standards
• Rainfall data – NOAA Atlas 14, Volume 6, Version 2 excerpt (for Paso Robles, CA)

Geotechnical Engineering Report
For
Proposed Commercial Buildings and Street Improvements
2930 Union Road Lots 6 and 13
Paso Robles, California
October 12, 2022
F-103116
Prepared For
MD3 Investments
By
Beacon Geotechnical, Inc.

P.O. Box 4814
Paso Robles, California 93447

October 12, 2022 F-103116
MD3 Investments
P.O. Box 13174
San Luis Obispo, CA 93406
Project: Proposed Commercial Buildings and Street Improvements 2930 Union Roads Lots 6 and 13
Paso Robles, California
Subject: Geotechnical Engineering and Infiltration Report As authorized, we have performed a Geotechnical Study for the above referenced project. The accompanying Geotechnical Engineering Report presents the results of our subsurface exploration, laboratory-testing program and conclusions and recommendations for geotechnical engineering aspects of project design. Our services were performed using the standard of care ordinarily exercised in this locality at the time this report was prepared.

Based on our study, it is our opinion that the site is suitable for the proposed developments from a geotechnical engineering standpoint provided the recommendations of this report are successfully implemented.

We have appreciated this opportunity to be of service to you on this project.

Please call if you have any questions, or if we can be of further service.

Respectfully submitted,
Beacon Geotechnical, Inc.

Greg McKay
Project Manager

Copies: 3-MD3 Investments
1-File Nicholas A. McClure
Geotechnical Engineer

F-103116 October 12, 2022

2 1. INTRODUCTION
This report presents results of a Geotechnical Engineering Study performed for the proposed commercial buildings and street improvements to be located in Paso Robles, California.

1.1 Description

1.1.1. It should be noted that grading and foundation plans were not provided for the purpose of this report. Prior to any construction, this firm should review the grading and foundation plans to verify or modify the recommendations offered herein. We anticipate that the sites will be developed by cutting and filling to create level building pads.

1.1.2. The proposed structures are assumed to be one (1) or two (2) stories of wood or metal framed construction.

1.1.3. Structural considerations for maximum wall load of 1.75 kips per square foot and maximum point loads of 25.0 kips were used as a basis for the recommendations of this report. If actual loads vary significantly from these assumed loads, Beacon Geotechnical, Inc. should be notified as re-evaluation of the recommendations contained herein may be required.
2 SCOPE OF WORK

2.1 The purpose of the geotechnical investigation that led to this report was to evaluate the soil conditions of the site with respect to the proposed developments. These conditions include surface and subsurface soil types, expansion potential, settlement potential, bearing capacity, and presence or absence of subsurface water. The scope of our work included:
• Reconnaissance of the site.
• Drilling, sampling, and logging of eighteen (18) borings to investigate soils and groundwater conditions.
• Laboratory testing of soil samples obtained from subsurface exploration to determine their physical and engineering properties.
• Geotechnical analysis of the data obtained.
• Consultation with owner representatives and design professionals. • Preparation of this report.

2.2 Contained in the report are:
• Discussions on local soil and groundwater conditions. • Results of laboratory and field tests.
• Conclusions and recommendations pertaining to site grading and structural design.

F-103116 October 12, 2022

3 3 SITE SETTING

3.1 The site of the proposed development is located in Paso Robles, California, with the approximate geographical coordinates 35°38’25.55” N and 120°39’05.92” W. See the Vicinity Map in Appendix A.

3.2 The proposed building sites are relatively level to slightly sloping with weeds up to one (1) foot high and a few existing structures to be removed prior to preparation of the new building pads.
4 SITE CONDITIONS

4.1 Soil Conditions

4.1.1 Evaluation of the subsurface indicates that soils are generally light brown very silty clayey sand overlain by light brown silty clayey sand with gravel, brown silty very clayey sand, and brown silty clayey sand with gravel.

4.1.2 Soils encountered at approximate bearing depths should be designed as Site Classification D in accordance with the local building code.

4.1.3 Expansion determination indicates that the bearing soils lie in the “Low” range.

4.2 Groundwater

4.2.1 Groundwater was not encountered to a depth of twenty (20) feet.

4.3 Infiltration Testing

4.3.1 Infiltration testing was done on the site in accordance with the Central Coast Low Impact Development Initiative standard. Twelve (12) infiltration borings were drilled with their locations shown on the Site Map in Appendix A. The borings were presaturated and subsequently tested. The resulting infiltration rates are as follows:

Test No. Depth (Ft.) Rate (Inch/Hour)
A 5.0’ 2.25
B 5.0’ 3.00
C 5.0’ 2.00
D 5.0’ 1.50
E 5.0’ 3.25
F 5.0’ 4.00
G 5.0’ 2.00
H 5.0’ 4.25
I 5.0’ 5.00
J 5.0’ 2.50
K 5.0’ 3.00
L 5.0’ 3.25

1 A
B
C
D
2 E
F
PROJECT #: F-103116
G
H
I
J
L
K
3 4
5 6

Ardmore Project
Location: Paso Robles, CA
Project: 0751-0005 Ardmore
Date: 12/05/2022
By: ZKP
Porchet Method Summary - Infiltration Calculations
Geotech Boring ID
Referenced*
Proposed DMA Selection
for design
Tested Infiltration Rate
(in/hr)*
Porchett Infiltration Rate
(in/hr) **
A --- 2.25 0.07
B DMA B2 3.00 0.19
C DMA B1 2.00 0.10
D --- 1.50 0.08
E --- 3.25 0.13
F --- 4.00 0.36
G --- 2.00 0.13
H --- 4.25 Data Not Included
I --- 5.00 0.70
J --- 2.50 0.10
K --- 3.00 0.17
L DMA A 3.25 0.20
* See Geotechnical Engineering Report (page 3) by Beacon Geotechnical, dated 10/12/2022 ** See Infiltration Test Field Mesaurements by Beacon Geotechnical, dated 09/28/2022 0751-0005_PorchetMethod_InfiltrationRate_PercTest Page 731 of 1344 Page 1 of 13 City Council Agenda April 21, 2026

1 A
B
C
D
2 E
F
PROJECT #: F-103116
G
H
I
J
L
K
3 4
5 6
Site Map from Geotechnical Engineering Report, by Beacon Geotechnical Inc, dated 10/12/2022 Selected locations for
WG drainage design

Infiltration Test Field Measurements
2930 Union Road
BORING NO. A
Site Location: Paso Robles, CA F-103116
Auger Diameter: 6”
Depth: 61 inches
Date: September 28, 2022
Time (Minutes) Depth (inches) Change in Depth (Inches) Rate (Inches/Hour) ---- 24.25 ---- ----
30 minutes 26.50 2.25 4.50
30 minutes 29.00 2.50 5.00
30 minutes 31.00 2.00 4.00
30 minutes 32.75 1.75 3.50
30 minutes 34.50 1.75 3.50
30 minutes 35.75 1.25 2.50
30 minutes 36.875 1.125 2.25
30 minutes 38.00 1.125 2.25

Range used
for Porchet
conversion

Test - Boring No. A
delta H 1.125 inches First Reading 3.07 ft User Input
delta T 60 minutes Last Reading 3.17 ft Calculated Values effective radius 3 inches Hole Depth 5.08 ft
H start 24.13 inches Riser Height 0
H end 23.00 inches
H ave 23.5625 inches
I
t 0.07 inches/hour
"Porchet Method"
Source: Riverside County Low Impact Development BMP Design Handbook, 2011 0751-0005_PorchetMethod_InfiltrationRate_PercTest Page 734 of 1344 Page 2 of 13 City Council Agenda April 21, 2026 Infiltration Test Field Measurements
2930 Union Road
BORING NO. B
Site Location: Paso Robles, CA F-103116
Auger Diameter: 6”
Depth: 58 inches
Date: September 28, 2022
Time (Minutes) Depth (inches) Change in Depth (Inches) Rate (Inches/Hour) ---- 25.00 ---- ----
30 minutes 30.25 5.25 10.50
30 minutes 33.00 2.75 5.50
30 minutes 35.00 2.00 4.00
30 minutes 37.50 2.50 5.00
30 minutes 39.50 2.00 4.00
30 minutes 41.00 1.50 3.00
30 minutes 42.75 1.75 3.50
30 minutes 44.25 1.50 3.00

Range used
for Porchet
conversion

Test - Boring No. B
delta H 3.25 inches First Reading 3.42 ft User Input
delta T 90 minutes Last Reading 3.69 ft Calculated Values effective radius 3 inches Hole Depth 4.83 ft
H start 17.00 inches Riser Height 0
H end 13.75 inches
H ave 15.375 inches
I
t 0.19 inches/hour
"Porchet Method"
Source: Riverside County Low Impact Development BMP Design Handbook, 2011 0751-0005_PorchetMethod_InfiltrationRate_PercTest Page 736 of 1344 Page 3 of 13 City Council Agenda April 21, 2026 Infiltration Test Field Measurements
2930 Union Road
BORING NO. C
Site Location: Paso Robles, CA F-103116
Auger Diameter: 6”
Depth: 60 inches
Date: September 28, 2022
Time (Minutes) Depth (inches) Change in Depth (Inches) Rate (Inches/Hour) ---- 24.50 ---- ----
30 minutes 27.00 2.50 5.00
30 minutes 28.50 1.50 3.00
30 minutes 30.25 1.75 3.50
30 minutes 31.50 1.25 2.50
30 minutes 32.50 1.00 2.00
30 minutes 33.75 1.25 2.50
30 minutes 35.00 1.25 2.50
30 minutes 36.00 1.00 2.00

Range used
for Porchet
conversion

Test - Boring No. C
delta H 3.5 inches First Reading 2.71 ft User Input
delta T 120 minutes Last Reading 3.00 ft Calculated Values effective radius 3 inches Hole Depth 5.00 ft
H start 27.50 inches Riser Height 0
H end 24.00 inches
H ave 25.75 inches
I
t 0.10 inches/hour
"Porchet Method"
Source: Riverside County Low Impact Development BMP Design Handbook, 2011 0751-0005_PorchetMethod_InfiltrationRate_PercTest Page 738 of 1344 Page 4 of 13 City Council Agenda April 21, 2026 Infiltration Test Field Measurements
2930 Union Road
BORING NO. D
Site Location: Paso Robles, CA F-103116
Auger Diameter: 6”
Depth: 57 inches
Date: September 28, 2022
Time (Minutes) Depth (inches) Change in Depth (Inches) Rate (Inches/Hour) ---- 26.00 ---- ----
30 minutes 27.25 1.25 2.50
30 minutes 28.50 1.25 2.50
30 minutes 30.00 1.50 3.00
30 minutes 31.00 1.00 2.00
30 minutes 31.75 0.75 1.50
30 minutes 32.75 1.00 2.00
30 minutes 33.75 1.00 2.00
30 minutes 34.50 0.75 1.50
Range used
for Porchet
conversion

Test - Boring No. D
delta H 2.75 inches First Reading 2.65 ft User Input
delta T 120 minutes Last Reading 2.88 ft Calculated Values effective radius 3 inches Hole Depth 4.75 ft
H start 25.25 inches Riser Height 0
H end 22.50 inches
H ave 23.875 inches
I
t 0.08 inches/hour
"Porchet Method"
Source: Riverside County Low Impact Development BMP Design Handbook, 2011 0751-0005_PorchetMethod_InfiltrationRate_PercTest Page 740 of 1344 Page 5 of 13 City Council Agenda April 21, 2026 Infiltration Test Field Measurements
2930 Union Road
BORING NO. E
Site Location: Paso Robles, CA F-103116
Auger Diameter: 6”
Depth: 59 inches
Date: September 28, 2022
Time (Minutes) Depth (inches) Change in Depth (Inches) Rate (Inches/Hour) ---- 26.75 ---- ----
30 minutes 29.75 3.00 6.00
30 minutes 32.00 2.25 4.50
30 minutes 34.50 2.50 5.00
30 minutes 36.50 2.00 4.00
30 minutes 38.25 1.75 3.50
30 minutes 40.00 1.75 3.50
30 minutes 41.625 1.625 3.25
30 minutes 43.25 1.625 3.25
Range used
for Porchet
conversion

Test - Boring No. E
delta H 1.625 inches First Reading 3.47 ft User Input
delta T 60 minutes Last Reading 3.60 ft Calculated Values effective radius 3 inches Hole Depth 4.92 ft
H start 17.38 inches Riser Height 0
H end 15.75 inches
H ave 16.5625 inches
I
t 0.13 inches/hour
"Porchet Method"
Source: Riverside County Low Impact Development BMP Design Handbook, 2011 0751-0005_PorchetMethod_InfiltrationRate_PercTest Page 742 of 1344 Page 6 of 13 City Council Agenda April 21, 2026 Infiltration Test Field Measurements
2930 Union Road
BORING NO. F
Site Location: Paso Robles, CA F-103116
Auger Diameter: 6”
Depth: 62 inches
Date: September 28, 2022
Time (Minutes) Depth (inches) Change in Depth (Inches) Rate (Inches/Hour) ---- 33.25 ---- ----
30 minutes 37.50 4.25 8.50
30 minutes 39.75 2.25 4.50
30 minutes 42.50 2.75 5.50
30 minutes 44.75 2.25 4.50
30 minutes 46.75 2.00 4.00
30 minutes 49.00 2.25 4.50
30 minutes 51.00 2.00 4.00
30 minutes 53.25 2.25 4.50
Range used
for Porchet
conversion

Test - Boring No. F
delta H 6.5 inches First Reading 3.90 ft User Input
delta T 120 minutes Last Reading 4.44 ft Calculated Values effective radius 3 inches Hole Depth 5.17 ft
H start 15.25 inches Riser Height 0
H end 8.75 inches
H ave 12 inches
I
t 0.36 inches/hour
"Porchet Method"
Source: Riverside County Low Impact Development BMP Design Handbook, 2011 0751-0005_PorchetMethod_InfiltrationRate_PercTest Page 744 of 1344 Page 7 of 13 City Council Agenda April 21, 2026 Infiltration Test Field Measurements
2930 Union Road
BORING NO. G
Site Location: Paso Robles, CA F-103116
Auger Diameter: 6”
Depth: 61 inches
Date: September 29, 2022
Time (Minutes) Depth (inches) Change in Depth (Inches) Rate (Inches/Hour) ---- 30.25 ---- ----
30 minutes 33.00 2.75 5.50
30 minutes 36.00 3.00 6.00
30 minutes 37.50 1.50 3.00
30 minutes 39.00 1.50 3.00
30 minutes 40.00 1.00 2.00
30 minutes 41.25 1.25 2.50
30 minutes 42.50 1.25 2.50
30 minutes 43.50 1.00 2.00
Range used
for Porchet
conversion

Test - Boring No. G
delta H 3.5 inches First Reading 3.33 ft User Input
delta T 120 minutes Last Reading 3.63 ft Calculated Values effective radius 3 inches Hole Depth 5.08 ft
H start 21.00 inches Riser Height 0
H end 17.50 inches
H ave 19.25 inches
I
t 0.13 inches/hour
"Porchet Method"
Source: Riverside County Low Impact Development BMP Design Handbook, 2011 0751-0005_PorchetMethod_InfiltrationRate_PercTest Page 746 of 1344 Page 8 of 13 City Council Agenda April 21, 2026 Infiltration Test Field Measurements
2930 Union Road
BORING NO. H
Site Location: Paso Robles, CA F-103116
Auger Diameter: 6”
Depth: inches No Available Data
Date: September 29, 2022
Time (Minutes) Depth (inches) Change in Depth (Inches) Rate (Inches/Hour) ---- ---- ----
30 minutes
30 minutes
30 minutes
30 minutes
30 minutes
30 minutes
30 minutes
30 minutes

Test - Boring No. H
delta H 0 inches First Reading 0.00 ft User Input
delta T 0 minutes Last Reading 0.00 ft Calculated Values effective radius 3 inches Hole Depth 0.00 ft
H start 0.00 inches Riser Height 0
H end 0.00 inches
H ave 0 inches
I
t #DIV/0! inches/hour
"Porchet Method"
Source: Riverside County Low Impact Development BMP Design Handbook, 2011 0751-0005_PorchetMethod_InfiltrationRate_PercTest Page 748 of 1344 Page 9 of 13 City Council Agenda April 21, 2026 Infiltration Test Field Measurements
2930 Union Road
BORING NO. I
Site Location: Paso Robles, CA F-103116
Auger Diameter: 6”
Depth: 60 inches
Date: September 29, 2022
Time (Minutes) Depth (inches) Change in Depth (Inches) Rate (Inches/Hour) ---- 32.50 ---- ----
30 minutes 38.25 5.75 11.50
30 minutes 41.75 3.50 7.00
30 minutes 44.75 3.00 6.00
30 minutes 47.25 2.50 5.00
30 minutes 49.75 2.50 5.00
30 minutes 52.50 2.75 5.50
30 minutes 55.25 2.75 5.50
30 minutes 57.75 2.50 5.00
Range used
for Porchet
conversion

Test - Boring No. I
delta H 10.5 inches First Reading 3.94 ft User Input
delta T 150 minutes Last Reading 4.81 ft Calculated Values effective radius 3 inches Hole Depth 5.00 ft
H start 12.75 inches Riser Height 0
H end 2.25 inches
H ave 7.5 inches
I
t 0.70 inches/hour
"Porchet Method"
Source: Riverside County Low Impact Development BMP Design Handbook, 2011 0751-0005_PorchetMethod_InfiltrationRate_PercTest Page 750 of 1344 Page 10 of 13 City Council Agenda April 21, 2026 Infiltration Test Field Measurements
2930 Union Road
BORING NO. J
Site Location: Paso Robles, CA F-103116
Auger Diameter: 6”
Depth: 62 inches
Date: September 29, 2022
Time (Minutes) Depth (inches) Change in Depth (Inches) Rate (Inches/Hour) ---- 30.75 ---- ----
30 minutes 32.75 2.00 4.00
30 minutes 34.75 2.00 4.00
30 minutes 37.00 2.25 4.50
30 minutes 38.50 1.50 3.00
30 minutes 40.00 1.50 3.00
30 minutes 42.00 2.00 4.00
30 minutes 43.25 1.25 2.50
30 minutes 44.50 1.25 2.50
Range used
for Porchet
conversion

Test - Boring No. J
delta H 1.25 inches First Reading 3.60 ft User Input
delta T 60 minutes Last Reading 3.71 ft Calculated Values effective radius 3 inches Hole Depth 5.17 ft
H start 18.75 inches Riser Height 0
H end 17.50 inches
H ave 18.125 inches
I
t 0.10 inches/hour
"Porchet Method"
Source: Riverside County Low Impact Development BMP Design Handbook, 2011 0751-0005_PorchetMethod_InfiltrationRate_PercTest Page 752 of 1344 Page 11 of 13 City Council Agenda April 21, 2026 Infiltration Test Field Measurements
2930 Union Road
BORING NO. K
Site Location: Paso Robles, CA F-103116
Auger Diameter: 6”
Depth: 56 inches
Date: September 29, 2022
Time (Minutes) Depth (inches) Change in Depth (Inches) Rate (Inches/Hour) ---- 28.50 ---- ----
30 minutes 31.25 2.75 5.50
30 minutes 34.25 3.00 6.00
30 minutes 37.25 3.00 6.00
30 minutes 39.25 2.00 4.00
30 minutes 41.50 2.25 4.50
30 minutes 43.00 1.50 3.00
30 minutes 44.75 1.75 3.50
30 minutes 46.25 1.50 3.00
Range used
for Porchet
conversion

Test - Boring No. K
delta H 3.25 inches First Reading 3.58 ft User Input
delta T 90 minutes Last Reading 3.85 ft Calculated Values effective radius 3 inches Hole Depth 5.17 ft
H start 19.00 inches Riser Height 0
H end 15.75 inches
H ave 17.375 inches
I
t 0.17 inches/hour
"Porchet Method"
Source: Riverside County Low Impact Development BMP Design Handbook, 2011 0751-0005_PorchetMethod_InfiltrationRate_PercTest Page 754 of 1344 Page 12 of 13 City Council Agenda April 21, 2026 Infiltration Test Field Measurements
2930 Union Road
BORING NO. L
Site Location: Paso Robles, CA F-103116
Auger Diameter: 6”
Depth: 63 inches
Date: September 28, 2022
Time (Minutes) Depth (inches) Change in Depth (Inches) Rate (Inches/Hour) ---- 33.00 ---- ----
30 minutes 35.75 2.75 5.50
30 minutes 38.25 2.50 5.00
30 minutes 40.50 2.25 4.50
30 minutes 42.75 2.25 4.50
30 minutes 44.375 1.625 3.25
30 minutes 46.125 1.75 3.50
30 minutes 47.75 1.625 3.25
30 minutes 49.50 1.75 3.50
Range used
for Porchet
conversion

Test - Boring No. L
delta H 3.375 inches First Reading 3.84 ft User Input
delta T 90 minutes Last Reading 4.13 ft Calculated Values effective radius 3 inches Hole Depth 5.25 ft
H start 16.88 inches Riser Height 0
H end 13.50 inches
H ave 15.1875 inches
I
t 0.20 inches/hour
"Porchet Method"
Source: Riverside County Low Impact Development BMP Design Handbook, 2011 0751-0005_PorchetMethod_InfiltrationRate_PercTest Page 756 of 1344 Page 13 of 13 City Council Agenda April 21, 2026

United States
Department of
Agriculture
A product of the National
Cooperative Soil Survey,
a joint effort of the United
States Department of
Agriculture and other
Federal agencies, State
agencies including the
Agricultural Experiment
Stations, and local
participants
Custom Soil Resource
Report for
San Luis Obispo
County, California,
Paso Robles Area
Natural
Resources
Conservation
Service
October 17, 2022 Page 758 of 1344 City Council Agenda April 21, 2026 45 Custom Soil Resource Report
Map—Hydrologic Soil Group
3945400 3945600 3945800 3946000 3946200 3946400 3946600 3946800 3947000 3945400 3945600 3945800 3946000 3946200 3946400 3946600 3946800 3947000 712100 712300 712500 712700 712900 713100
712100 712300 712500 712700 712900 713100 713300
35° 38' 39'' N
120° 39' 31'' W
35° 38' 39'' N
120° 38' 38'' W
35° 37' 42'' N
120° 39' 31'' W
35° 37' 42'' N
120° 38' 38'' W
N
Map projection: Web Mercator Corner coordinates: WGS84 Edge tics: UTM Zone 10N WGS84 0 400 800 1600 2400
Feet
0 100 200 400 600
Meters
Map Scale: 1:8,620 if printed on A portrait (8.5" x 11") sheet.

Soil Map may not be valid at this scale.

MAP LEGEND MAP INFORMATION
Area of Interest (AOI)
Area of Interest (AOI)
Soils
Soil Rating Polygons
A
A/D
B
B/D
C
C/D
D
Not rated or not available
Soil Rating Lines
A
A/D
B
B/D
C
C/D
D
Not rated or not available
Soil Rating Points
A
A/D
B
B/D
C
C/D
D
Not rated or not available
Water Features
Streams and Canals
Transportation
Rails
Interstate Highways
US Routes
Major Roads
Local Roads
Background
Aerial Photography
The soil surveys that comprise your AOI were mapped at
1:24,000.

Warning: Soil Map may not be valid at this scale.

Enlargement of maps beyond the scale of mapping can cause misunderstanding of the detail of mapping and accuracy of soil line placement. The maps do not show the small areas of contrasting soils that could have been shown at a more detailed scale.

Please rely on the bar scale on each map sheet for map
measurements.

Source of Map: Natural Resources Conservation Service
Web Soil Survey URL:

Coordinate System: Web Mercator (EPSG:3857)
Maps from the Web Soil Survey are based on the Web Mercator projection, which preserves direction and shape but distorts distance and area. A projection that preserves area, such as the Albers equal-area conic projection, should be used if more accurate calculations of distance or area are required.

This product is generated from the USDA-NRCS certified data as of the version date(s) listed below.

Soil Survey Area: San Luis Obispo County, California, Paso Robles Area
Survey Area Data: Version 16, Sep 14, 2022
Soil map units are labeled (as space allows) for map scales 1:50,000 or larger.

Date(s) aerial images were photographed: Mar 12, 2022—Apr 12, 2022
The orthophoto or other base map on which the soil lines were compiled and digitized probably differs from the background Custom Soil Resource Report
46

MAP LEGEND MAP INFORMATION
imagery displayed on these maps. As a result, some minor shifting of map unit boundaries may be evident.

Custom Soil Resource Report
47

Table—Hydrologic Soil Group
Map unit symbol Map unit name Rating Acres in AOI Percent of AOI 100 Arbuckle fine sandy
loam, 0 to 2 percent
slopes
C 22.6 5.9%
102 Arbuckle-Positas
complex, 9 to 15
percent slopes
C 4.2 1.1%
103 Arbuckle-Positas
complex, 15 to 30
percent slopes
C 39.1 10.1%
104 Arbuckle-Positas
complex, 30 to 50
percent slopes
C 14.3 3.7%
106 Arbuckle-San Ysidro
complex, 2 to 9
percent slopes
C 82.1 21.3%
133 Cropley clay, 2 to 9
percent slopes, MLRA
14 C 33.8 8.8%
149 Hanford and Greenfield
gravelly sandy loams,
0 to 2 percent slopes
A 12.5 3.2%
150 Hanford and Greenfield
gravelly sandy loams,
2 to 9 percent slopes
A 14.2 3.7%
167 Metz-Tujunga complex,
occasionally flooded, 0
to 5 percent slopes
A 3.5 0.9%
177 Nacimiento-Ayar
complex, 9 to 30
percent slopes
C 76.2 19.7%
179 Nacimiento-Los Osos
complex, 9 to 30
percent slopes

60.4 15.6%
197 San Ysidro loam, 0 to 2
percent slopes, MLRA
14 C 23.0 6.0%
300 Corducci and Typic
Xerofluvents, 0 to 5
percent slopes,
occasionally flooded,
MLRA 14
A 0.1 0.0%
Totals for Area of Interest 386.2 100.0%
Rating Options—Hydrologic Soil Group
Aggregation Method: Dominant Condition
Aggregation is the process by which a set of component attribute values is reduced to a single value that represents the map unit as a whole.

Custom Soil Resource Report
48

A map unit is typically composed of one or more "components". A component is either some type of soil or some nonsoil entity, e.g., rock outcrop. For the attribute being aggregated, the first step of the aggregation process is to derive one attribute value for each of a map unit's components. From this set of component attributes, the next step of the aggregation process derives a single value that represents the map unit as a whole. Once a single value for each map unit is derived, a thematic map for soil map units can be rendered. Aggregation must be done because, on any soil map, map units are delineated but components are not.

For each of a map unit's components, a corresponding percent composition is recorded. A percent composition of 60 indicates that the corresponding component typically makes up approximately 60% of the map unit. Percent composition is a critical factor in some, but not all, aggregation methods.

The aggregation method "Dominant Condition" first groups like attribute values for the components in a map unit. For each group, percent composition is set to the sum of the percent composition of all components participating in that group. These groups now represent "conditions" rather than components. The attribute value associated with the group with the highest cumulative percent composition is returned. If more than one group shares the highest cumulative percent composition, the corresponding "tie-break" rule determines which value should be returned. The "tie-break" rule indicates whether the lower or higher group value should be returned in the case of a percent composition tie. The result returned by this aggregation method represents the dominant condition throughout the map unit only when no tie has occurred.

Component Percent Cutoff: None Specified
Components whose percent composition is below the cutoff value will not be considered. If no cutoff value is specified, all components in the database will be considered. The data for some contrasting soils of minor extent may not be in the database, and therefore are not considered.

Tie-break Rule: Higher
The tie-break rule indicates which value should be selected from a set of multiple candidate values, or which value should be selected in the event of a percent composition tie.

Custom Soil Resource Report
49

References
American Association of State Highway and Transportation Officials (AASHTO). 2004. Standard specifications for transportation materials and methods of sampling and testing. 24th edition.

American Society for Testing and Materials (ASTM). 2005. Standard classification of soils for engineering purposes. ASTM Standard D2487-00.

Cowardin, L.M., V. Carter, F.C. Golet, and E.T. LaRoe. 1979. Classification of wetlands and deep-water habitats of the United States. U.S. Fish and Wildlife Service FWS/OBS-79/31.

Federal Register. July 13, 1994. Changes in hydric soils of the United States.

Federal Register. September 18, 2002. Hydric soils of the United States.

Hurt, G.W., and L.M. Vasilas, editors. Version 6.0, 2006. Field indicators of hydric soils in the United States.

National Research Council. 1995. Wetlands: Characteristics and boundaries.

Soil Survey Division Staff. 1993. Soil survey manual. Soil Conservation Service.

U.S. Department of Agriculture Handbook 18. http://www.nrcs.usda.gov/wps/portal/ nrcs/detail/national/soils/?cid=nrcs142p2_054262
Soil Survey Staff. 1999. Soil taxonomy: A basic system of soil classification for making and interpreting soil surveys. 2nd edition. Natural Resources Conservation Service, U.S. Department of Agriculture Handbook 436. http:// www.nrcs.usda.gov/wps/portal/nrcs/detail/national/soils/?cid=nrcs142p2_053577 Soil Survey Staff. 2010. Keys to soil taxonomy. 11th edition. U.S. Department of Agriculture, Natural Resources Conservation Service. http:// www.nrcs.usda.gov/wps/portal/nrcs/detail/national/soils/?cid=nrcs142p2_053580 Tiner, R.W., Jr. 1985. Wetlands of Delaware. U.S. Fish and Wildlife Service and Delaware Department of Natural Resources and Environmental Control, Wetlands Section.

United States Army Corps of Engineers, Environmental Laboratory. 1987. Corps of Engineers wetlands delineation manual. Waterways Experiment Station Technical Report Y-87-1.

United States Department of Agriculture, Natural Resources Conservation Service.

National forestry manual. http://www.nrcs.usda.gov/wps/portal/nrcs/detail/soils/ home/?cid=nrcs142p2_053374
United States Department of Agriculture, Natural Resources Conservation Service.

National range and pasture handbook. http://www.nrcs.usda.gov/wps/portal/nrcs/ detail/national/landuse/rangepasture/?cid=stelprdb1043084 50

United States Department of Agriculture, Natural Resources Conservation Service.

National soil survey handbook, title 430-VI. http://www.nrcs.usda.gov/wps/portal/ nrcs/detail/soils/scientists/?cid=nrcs142p2_054242
United States Department of Agriculture, Natural Resources Conservation Service. 2006. Land resource regions and major land resource areas of the United States, the Caribbean, and the Pacific Basin. U.S. Department of Agriculture Handbook 296. http://www.nrcs.usda.gov/wps/portal/nrcs/detail/national/soils/? cid=nrcs142p2_053624
United States Department of Agriculture, Soil Conservation Service. 1961. Land capability classification. U.S. Department of Agriculture Handbook 210. http:// www.nrcs.usda.gov/Internet/FSE_DOCUMENTS/nrcs142p2_052290.pdf Custom Soil Resource Report
51

SECTION V

STORM DRAINS, STORM WATER QUALITY, AND WATERSHED PROTECTION V-1. GENERAL
It is the general purpose of these standards that storm water be contained and treated on the area to be developed. Adjacent improvements, existing or planned, will be free from flood hazard and will not receive a greater volume and intensity of storm water runoff than pre-existing conditions. Flood hazard is defined as potential damage by water having sufficient depth or velocity to damage improvements or to deposit or scour soil.

These specifications are intended to meet the requirements of the National Flood Insurance Program, the City’s Flood Plain Ordinance, and the City’s Storm Water Management Plan. These specifications reflect numeric storm water control criteria adopted by the Water Board on July 13, 2013 (including subsequent revisions) and modified as specifically applicable to the City of Paso Robles.

The lowest floor of any project that is located within a Special Flood Hazard Area and shown as an A, AE, AH or AO Zone shall be elevated above the highest adjacent grade to a height equal to or exceeding the depth number specified in feet on the Flood Insurance Rate Map (FIRM) by at least one foot, or elevated at least three feet above the highest adjacent grade if no depth number is specified.

Upon completion of a structure in a Special Flood Hazard Area, the elevation of the lowest floor including basement shall be certified by a registered professional engineer or land surveyor, and verified by the city building inspector to be properly elevated.

Such certification or verification shall be provided to the City Engineer.

Modification of a flood-plain shall be accomplished in accordance with Federal Management Emergency Management (FEMA) regulations and the City’s Floodplain Ordinance. The design engineer shall provide all data necessary for a Conditional Letter of Map Amendment (CLOMA) and a final Letter of Map Amendment (LOMA).

These standards are intended to provide general design criteria. Most design details are left to the responsibility of the consultant. The design standards contained herein are minimal and alternates may be approved, provided such alternates are to a higher standard than those set forth. Exceptions to these standards may be allowed by the City Engineer when it can be determined that such exceptions are in the best interest of the City.

FROM

CITY OF PASO ROBLES STANDARD SPECIFICATIONS AND DETAILS

sustain a minimum infiltration rate of 5 inches per hour throughout the life of the project and must maximize runoff retention and pollutant removal.

A mixture of sand (60%-70%) meeting the specifications of ASTM C33 and compost (30%-40%) may be used. An alternative planting medium may be utilized if it is demonstrated to be equal or more effective at attenuating pollutants than the specified planting medium mixture. • Proper plant selection as provided by the Central Coast LID Initiative. • Subsurface drainage/storage (gravel) layer with an area equal to the biofiltration treatment system surface area and having a minimum depth of 12 inches.
• Underdrain with discharge elevation at top of gravel layer. • No compaction of soils beneath the biofiltration facility. • No liners or other barriers interfering with infiltration (excepting conditions were lateral infiltration is not feasible).
.

Non-Retention Based Treatment Systems:

Stormwater Control Measures that collectively achieve at least one of the following hydraulic sizing criteria for non-retention based treatment systems:
• Volume Design Basis: Treat stormwater runoff equal to the volume of runoff generated by the 85th percentile 24-hour storm event (0.80 inches). • Flow Design Basis: Treat the flow of runoff produced by a rain event equal to at least 0.2 inches per hour intensity.
(5) Performance Requirement No. 3: Runoff Retention
Projects that create and/or replace greater than or equal to 15,000 square feet of impervious surface are required to meet runoff retention performance requirements using Low Impact Development Standards. See Stormwater Technical Guide.

Prevent off-site discharge from events up to the 95th percentile 24-hour rainfall event (1.45 inches). Retention is to be achieved by optimizing infiltration.

Project design shall be founded in Low Impact Development principles. Site opportunities and constraints shall be identified and a site assessment shall include:
• Topography, structures, utilities, easements
• Hydrologic features including natural areas, wetlands, watercourses, seeps, or springs.
• Depth to seasonal high groundwater
• Locations of wells
• Depth to impervious bedrock
• Presence of unique geology
FROM

CITY OF PASO ROBLES STANDARD SPECIFICATIONS AND DETAILS

• Geotechnical hazards
• Soil and/or groundwater contamination
• Soil types and hydrologic soil groups
• Vegetative cover/trees
• Run-on characteristics (estimate off-site runoff discharging to the project area)
• Existing drainage infrastructure
• Zoning, setbacks and open space requirements
• Define the development envelope and protected areas, identifying areas that are most suitable for development and areas to be left undisturbed. • Conserve natural areas including existing trees, vegetation and soils • Limit the overall impervious footprint of the project • Set back development from creeks, wetlands and riparian habitats • When runoff reduction measures and natural landscape areas have been maximized to the extent feasible storm water control measures shall be used to comply with performance requirements. Storm water control measures associated with small-scale, decentralized facilities designed to infiltrate, evapotranspirate, filter, or capture storm water shall be optimized. Refer to the City’s technical guidelines for sizing of storm water retention facilities.
(6) Performance Requirement No. 4: Peak Management
All projects that create and/or replace greater than or equal to 22,500 square feet of impervious surface in Watershed Management Zone 1 shall manage peak stormwater runoff as required below as well as meeting Water Quality and Runoff Retention requirements.

Post-development peak flows, discharged from the site, shall not exceed preproject peak flows for the 2 through 10-year storm events.

A Stormwater Control shall be provided in conformance with the Stormwater Technical Guide on File with the Stormwater Control Manager in the Department of Public Works.
(7) Operation and Maintenance for Structural Stormwater Control Measures The design of all structural stormwater control measures must be accompanied by an operation and maintenance (O and M) plan. Minimum requirements for the O and M plan are described in the City’s Technical Guide.

Prior to project acceptance or occupancy, verification of on-going maintenance of structural stormwater control measures must be established by legal binding agreements.

FROM

CITY OF PASO ROBLES STANDARD SPECIFICATIONS AND DETAILS

B. Off-Site Hydrology, Cross-Culverts, Open Channels

1. Hydrology Calculations
The Rational Method shall be used to compute the total volume of runoff from a development with an area less than 200 acres. For drainage areas in excess of 200 acres, or where the design engineer determines that the Rational Method is not practical or appropriate, the design engineer shall provide all documents necessary to confirm computations.

All calculations shall be prepared by a registered professional engineer with a current license to practice in the State of California. The rainfall intensity curve included herein is available for use as part of the hydrology calculations. In computing runoff in a partial development, adequate provisions must be made for the drainage of the overall improvements and/or drainage tributary.

Hydrology calculations shall be based upon ultimate land use designations in accordance with the adopted General Plan.

FROM

CITY OF PASO ROBLES STANDARD SPECIFICATIONS AND DETAILS

 





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FROM

CITY OF PASO ROBLES STANDARD SPECIFICATIONS AND DETAILS

3. Open Channels
Open channels shall be designed based on Manning's equation. The impacts of culverts, bridges or other structures affecting the hydraulic performance of the channel shall be considered as appropriate.

The City Engineer may require more complete analysis if he/she determines conditions merit a more thorough study. This additional analysis may include determination of the water surface profile, analysis of critical sections, and analysis of erosion and/or sedimentation.

Maximum velocity for channels flowing full shall be limited to preclude erosion.

Freeboard of at least one foot based on 25-year volumes shall be provided for all channels. Lining treatments shall extend to the full height of freeboard. The 100-year discharge shall be contained within the banks or within the easement established for the channel. For natural waterways, the design flow may be allowed in the natural overflow area.

4. Retention Basins
Storm water retention for flood control purposes shall be applied as determined by the design engineer; typically where downstream conditions are constrained and properties are threatened or have been flooded in conditions existing prior to upstream development. Criteria for the design of retention basins may be reviewed on a case by case basis. Typically, the volume of storage for flood control purposes is based upon the post-development 100-year, 24-hour storm event.

5. Detention Basins
A detention basin is defined as a holding facility where the rate of flow from the basin is limited to that rate historically occurring prior to development. The volume of storage of a detention basin shall be determined by theoretically matching the historical hydrograph of flows leaving the previously undeveloped land under consideration.

6. Storm Drain Alignment Criteria
Storm drain lines shall be parallel with street centerlines to the extent practical and typically twelve feet southerly or easterly of the centerline (Standard Detail U-1).

FROM

CITY OF PASO ROBLES STANDARD SPECIFICATIONS AND DETAILS

DEPARTMENT OF PUBLIC WORKS - STANDARD DRAWINGS Scale:

Drawing
Issued:

August 2022 NTS
Revised: Revision No:

No: H-1

HYDROLOGY

AVERAGE ANNUAL RAINFALL MONTEREY COUNTY PACIFIC OCEAN SANTA BARBARA COUNTY 6 8
10 10
10 16
18 16
18 14
14 12
12 16
16 18
18 18
18 14 12
14 14
14 16
16 18
16 20 20
22 24 26
26 24
28 28
20 20
20 22
22 20
24 26
26 28
3230
32 34 36 38
36 36
30 32
34 40
42 40
40 SAN LUIS OBISPO COUNTY AVERAGE ANNUAL PRECIPITATION (JULY 1 THROUGH JUNE 30) FOR 42 YEAR PERIOD FROM 1955-56 THROUGH 1997-98) SAN LUIS OBISPO FLOOD CONTROL AND WATER CONSERVATION DISTRICT LOS OSOS MORRO BAYAVILA BEACHOCEANO SAN LUIS OBISPO 24 NIPOMOPOZO GROVER BEACH CAMBRIA SAN SIMEON 24 PASO ROBLES SAN MIGUEL 33 166 CUYAMA 101 1 KERN COUNTY 101 SANTA MARGARITA 227 1 41 41CRESTON TEMPLETON 58 229 46 46 SHANDON ARROYO GRANDE 1 CALIFORNIA VALLEY ATASCADERO PISMO BEACH LEGEND: 22 - AVERAGE ANNUAL PRECIPITATION (INCHES) Project Site

DEPARTMENT OF PUBLIC WORKS - STANDARD DRAWINGS Scale:

Drawing
Issued:

August 2022 NTS
Revised: Revision No:

No: H-2

HYDROLOGY

TIME OF CONCENTRATION
TC

HOURS MINUTES
4 3
2 1 TIME OF FLOOD CONCENTRATION 18
16 14
12 9
8 7
6 4
3 5
20 30
40 240
180
120
70 80
90 100
60 50
10 LENGTH OF CHANNEL FROM MOST REMOTE POINT TO POINT OF CONCENTRATION L

MILES FEET

0.5 1
2 3
4 5
10 600
700
800
900
1200
1400
1600
1800
300
5000
4000
3000
2000
1000
500
400
200
HELEVATION IN FEET OF MOST REMOTE POINT OF WATERSHED ABOVE POINT OF CONCENTRATION. 900 800
700
600
15 FEET
5000
4000
3000
2000
1000
500
400
300
200
100
50 40
30 20
10 ( )
LEGEND:

Tc = TIME OF CONCENTRATION
IN HOURS.

L = LENGTH OF CHANNEL IN
MILES.

H = DIFFERENCE IN ELEVATION

BETWEEN MOST REMOTE

POINT AND THE POINT OF
CONCENTRATION IN FEET.

EQUATIONS FOR ESTIMATED
"TIME OF CONCENTRATION"
NOTES:

1. THIS NOMOGRAPH IS LIMITED TO
WATERSHED AREAS OF 200
ACRES OR LESS. FOR LARGER

WATERSHEDS REFER TO THE
DESIGN STANDARDS.

PROFILE STREAM
Tc =

0.3853
H

11.9L
H
L

POINT OF

CONCENTRATION

WATERSHED
LIMITS
REF: P.Z. KIRPICH, CIVIL ENGINEERING, Vol. 10, No. 6, JUNE 1940, p. 362 FOR WATERSHEDS LESS THAN 200 ACRES

DEPARTMENT OF PUBLIC WORKS - STANDARD DRAWINGS Scale:

Drawing
Issued:

August 2022 NTS
Revised: Revision No:

No: H-3

HYDROLOGY

RUNOFF COEFFICIENTS-DEVELOPED
FOOT NOTES:

1. ESTIMATION OF COMPOSITE "C" VALUE USING ESTIMATED IMPERVIOUS AREAS AND STD. DWG. H-3a (TABLE 2) MAY BE REQUIRED BY THE DEPARTMENT. IMPERVIOUS AND PAVED AREAS SHALL USE C=0.95. 2, ALL VALUES SHOWN ARE INTENDED TO BE MINIMUMS. HIGHER VALUES MAY BE REQUIRED BY THE DEPARTMENT.

SOIL SLOPE
TYPE OF DEVELOPMENT TYPE <2% 2% to 10% >10% NOTE
RESIDENTIAL LOTS > 20,000 SF C 1,2
S 1,2
RESIDENTIAL LOTS 10,000 SF TO 19,999 SF C 0.40 0.45 0.55 1,2 " S 0.30 0.40 0.45 1,2
RESIDENTIAL LOTS 6,000 SF TO 9,999 SF C 0.45 0.55 0.65 1,2 " S 0.35 0.40 0.50 1,2
PLANNED DEVELOPMENTS (PUD) C 1,2
" S 1,2
APARTMENTS C 0.50 0.60 0.70 2
" S 0.40 0.50 0.60 2
INDUSTRIAL C 0.55 0.65 0.75 2
" S 0.45 0.55 0.65 2
COMMERCIAL C 0.75 0.80 0.85 2
" S 0.70 0.75 0.80 2
LEGEND:

C - CLAY, ADOBE, ROCK, OR IMPERVIOUS MATERIAL

S - SAND, GRAVEL, LOAM, OR PERVIOUS MATERIAL
NOTES:

1. COEFFICIENTS FOR RESIDENTIAL LOTS ASSUME TYPICAL SINGLE FAMILY RESIDENCE WITH ASSOCIATED GARAGE, DRIVEWAY, FLATWORK, AND LANDSCAPING. HIGHER DENSITY RESIDENTIAL DEVELOPMENTS MAY REQUIRE USING

COMPOSITE COEFFICIENT EVALUATED BY THE DESIGN ENGINEER AND BASED ON PROPOSED DEVELOPMENT IMPERVIOUS AREAS.

2. FOR ALL TYPES OF DEVELOPMENT, COEFFICIENTS ARE INCLUSIVE OF ONLY THE LOT AREA OUTSIDE THE RIGHT-OF-WAY (NET LOT AREA). PAVED SURFACES BETWEEN ROAD CENTERLINE AND RIGHT-OF-WAY SHALL BE EVALUATED SEPARATELY AND INCLUDED TO DETERMINE A COMPOSITE "C" FACTOR.

3. ALL IMPERVIOUS AREAS AND PAVED AREAS SHALL USE C = 0.95.

FOOT

0.25 0.35 0.40

0.35 0.40 0.50

0.60 0.65 0.70

0.65 0.70 0.75
TABLE 1: RATIONAL METHOD STANDARD RUNOFF COEFFICIENTS FOR

DEVELOPED AREAS

DEPARTMENT OF PUBLIC WORKS - STANDARD DRAWINGS Scale:

Drawing
Issued:

August 2022 NTS
Revised: Revision No:

RUNOFF COEFFICIENTS-UNDEVELOPED No:

HYDROLOGY
H-3a

EXTREME HIGH NORMAL LOW
EXAMPLE:

GIVEN: AN UNDEVELOPED WATERSHED CONSISTING OF:

1. ROLLING TERRAIN WITH AVERAGE SLOPES OF 5%

2. CLAY SOILS

3. GOOD GRASSLAND AREA

4. NORMAL SURFACE DEPRESSIONS
FIND: THE RUNOFF COEFFICIENT FOR THE ABOVE WATERSHED
SOLUTION:

1. RELIEF = 0.14

2. SOIL INFILTRATION = 0.08

3. VEGETAL COVER = 0.04

4. SURFACE STORAGE = 0.06
ANSWER: THE RUNOFF COEFFICIENT, C = 0.14 + 0.08 + 0.04 + 0.06 = 0.32 RELIEF
SOIL

INFILTRATION

VEGETAL
COVER

SURFACE

STORAGE

0.28 TO 0.35

STEEP, RUGGED

TERRAIN WITH AVERAGE
SLOPES ABOVE 30%

0.20 TO 0.28

HILLY, WITH AVERAGE
SLOPES OF 10% TO 30%

0.14 TO 0.20 ROLLING,

WITH AVERAGE SLOPE
OF 5% TO 10%

0.08 TO 0.14

RELATIVELY FLAT LAND,

WITH AVERAGE SLOPES
OF 0% TO 5%

0.12 TO 0.16

NO EFFECTIVE SOIL

COVER, EITHER ROCK

OR THIN MANTLE OF

NEGLIGIBLE

INFILTRATION CAPACITY

0.08 TO 0.12

SLOW TO TAKE UP

WATER, CLAY OR

SHALLOW LOAM SOILS

OF LOW INFILTRATION

CAPACITY,

IMPERFECTLY OR

POORLY DRAINED

0.06 TO 0.08
NORMAL; WELL

DRAINED LIGHT OR

MEDIUM TEXTURED

SOILS, SANDY LOAMS,

SILT AND SILT LOAMS

0.04 TO 0.06
HIGH; DEEP SAND OR

OTHER SOILS THAT

TAKES UP WATER

READILY, VERY LIGHT

WELL DRAINED SOILS

0.12 TO 0.16

NO EFFECTIVE PLANT

COVER, BARE OR VERY

SPARSE COVER

0.08 TO 0.12
POOR TO FAIR;

CULTIVATION CROPS, OR

POOR NATURAL COVER,
LESS THAN 20% OF

DRAINAGE AREA OVER

GOOD COVER

0.06 TO 0.08
FAIR TO GOOD; ABOUT
50% OF AREA IN GOOD

GRASSLAND OR

WOODLAND, NOT MORE
THAN 50% OF AREA IN

CULTIVATED CROPS

0.04 TO 0.06
GOOD TO EXCELLENT;
ABOUT 90% OF

DRAINAGE AREA IN

GOOD GRASSLAND,

WOODLAND, OR

EQUIVALENT COVER

0.04 TO 0.06
HIGH; SURFACE
STORAGE, HIGH;

DRAINAGE SYSTEM NOT
SHARPLY DEFINED;

LARGE FLOOD PLAIN

STORAGE OR LARGE

NUMBER OF PONDS OR

MARSHES

0.06 TO 0.08
NORMAL;

CONSIDERABLE

SURFACE STORAGE,

LAKES AND POND

MARSHES

0.08 TO 0.10
LOW; WELL DEFINED

SYSTEM OF SMALL

DRAINAGE WAYS, NO

PONDS OR MARSHES

0.10 TO 0.12

NEGLIGIBLE SURFACE

DEPRESSIONS FEW AND
SHALLOW; DRAINAGE

WAYS STEEP AND

SMALL, NO MARSHES
(REFERENCES FIGURE 819.2A OF HIGHWAY DESIGN MANUAL)
TABLE 2: RATIONAL METHOD STANDARD RUNOFF COEFFICIENTS FOR

UNDEVELOPED AREAS

0.20 0.08 0.06 0.08 0.42 Subtotal

DEPARTMENT OF PUBLIC WORKS - STANDARD DRAWINGS Scale:

Drawing
Issued:

August 2022 NTS
Revised: Revision No:

RAINFALL INTENSITY No:

HYDROLOGY
H-4
Duration
TABLE 1: ANNUAL RAINFALL < 14"
10 Min 15 Min 30 Min 1 Hr 2 Hr 3 Hr 6 Hr 10 Hr
2 1.00 0.90 0.60 0.40 0.26 0.22 0.18 0.14
5 1.40 1.20 0.80 0.50 0.37 0.32 0.25 0.20
10 1.70 1.40 1.00 0.60 0.44 0.38 0.30 0.23
25 2.00 1.70 1.10 0.70 0.54 0.47 0.37 0.28
50 2.20 1.90 1.30 0.80 0.60 0.53 0.44 0.34
100 2.40 2.10 1.40 0.90 0.65 0.59 0.48 0.36
10 Min 15 Min 30 Min 1 Hr 2 Hr 3 Hr 6 Hr 10 Hr

1.30 1.10 0.80 0.50 0.35 0.30 0.23 0.18

1.90 1.60 1.10 0.70 0.49 0.42 0.33 0.26

2.30 1.90 1.30 0.80 0.60 0.51 0.40 0.30

2.60 2.20 1.50 1.00 0.71 0.63 0.50 0.38

3.00 2.50 1.70 1.10 0.81 0.74 0.60 0.47

3.20 2.70 1.90 1.20 0.90 0.80 0.65 0.49
10 Min 15 Min 30 Min 1 Hr 2 Hr 3 Hr 6 Hr 10 Hr

1.70 1.40 1.00 0.65 0.44 0.37 0.29 0.22

2.30 1.90 1.30 0.85 0.60 0.52 0.41 0.33

2.80 2.40 1.60 1.03 0.74 0.64 0.50 0.38

3.20 2.70 1.90 1.20 0.92 0.80 0.64 0.50

3.70 3.10 2.10 1.40 1.05 0.92 0.74 0.58

4.00 3.40 2.30 1.50 1.13 1.00 0.80 0.62
10 Min 15 Min 30 Min 1 Hr 2 Hr 3 Hr 6 Hr 10 Hr

2.10 1.80 1.20 0.77 0.55 0.47 0.36 0.28

2.80 2.50 1.70 1.05 0.76 0.64 0.52 0.42

3.60 3.00 2.10 1.30 0.92 0.81 0.64 0.48

3.90 3.50 2.40 1.50 1.10 0.98 0.78 0.60

4.50 3.90 2.60 1.70 1.28 1.15 0.94 0.72

5.00 4.30 2.90 1.85 1.40 1.25 0.98 0.76
Duration
TABLE 2: ANNUAL RAINFALL 14" TO 17"
Duration
TABLE 3: ANNUAL RAINFALL 18" TO 21"
Duration
TABLE 4: ANNUAL RAINFALL 22" TO 28" (Years) Recurrence Interval Recurrence Interval (Years) 100
50 25
10 5
2 2
5 10
25 50
100 (Years) Recurrence Interval
2 5
10 25
50 100 (Years) Recurrence Interval
Intensity (inches/hour)
Intensity (inches/hour)
Intensity (inches/hour)
Intensity (inches/hour)








 









 
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NOAA ATLAS 14,
VOLUME 6, VERSION 2

FOR PASO ROBLES, CA



















 




FROM
NOAA ATLAS 14, VOLUME 6,
VERSION 2 FOR PASO ROBLES, CA












 






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FROM
NOAA ATLAS 14,
VOLUME 6, VERSION 2

FOR PASO ROBLES, CA

APPENDIX C
Appendix C – Preliminary Drainage Design Calculations
• Existing and Proposed Hydrologic Calculations
• Existing and Proposed Land Use Data
• Time of Concentration Calculations
• HydroCAD Drainage Results – Existing Site
o 25-Year, 50-Year, and 100-Year Design Storms
• HydroCAD Drainage Results – Proposed Site
o 25-Year, 50-Year, and 100-Year Design Storms
• Ardmore Bypass Culvert analysis – 25-year and 100-year storm event

Ardmore Project
Location: Paso Robles, CA
Project: 0751-0005 Ardmore
Date: 2/16/2022
By: ZKP
Overall Hydrologic Calculations - SBUH method in HydroCAD 95th inches 1.45
2 YR inches 2.14
10 YR inches 3.74
25 YR inches 4.70
50 YR inches 5.42
100 YR inches 6.16
Pre-Dev.

Total Area
(ac)
Post-Dev.

Total Area
(ac)
Storm Pre-Developed
Flow, Q (cfs)
Post-Developed
Flow, Q (cfs)
Proposed Structural
Control Measures
(SCM)
95th - -
2 YR 32.51 31.75
10 YR 61.76 59.90
25 YR 72.83 71.33
50 YR 85.55 83.41
100 YR 93.67 90.48
95th Data Unknown -
2 YR 1.02 0.04
10 YR 2.11 0.59
25 YR 2.46 1.65
50 YR 2.97 2.53
100 YR 3.54 3.42
95th 0.01 0.03
2 YR 0.15 0.07
10 YR 0.74 0.12
25 YR 1.17 0.15
50 YR 1.52 0.18
100 YR 1.89 0.20
95th - -
2 YR 0.56 -
10 YR 2.94 0.54
25 YR 4.70 1.37
50 YR 6.11 3.36
100 YR 7.62 6.81

71.33 71.33
Pre-Dev.

Total Area
(ac)
Post-Dev.

Total Area
(ac)
Storm Pre-Developed
Flow, Q (cfs)
Post-Developed
Flow, Q (cfs)
95th 0.01 0.03
2 YR 2.97 0.59
10 YR 12.23 5.83
25 YR 18.62 11.96
50 YR 23.99 17.32
100 YR 29.75 23.94
2 2
2 2
1 Roadside bioretention
swales, StormTech
Chamber:
(B1 = 78' x 88')
(B2 = 178' x 23')
Ardmore Industrial
* See NOAA Atlas 14 Rainfall data (24-hr storm
duration)

3.27 Drainage Area Subtotal
Antecedent Moisture Condition (AMC) utilized in
HydroCAD.

14.06 64.43 64.46

2.80 0.27

14.06 3.79

2.82 0.80
Pre- vs. Post-Development Peak Flow Summary - OVERALL PROJECT SITE Project Site
Drainage Notes
A bypass culvert is proposed to
intercept offsite run-on from the
south (EX1 offsite) and convey it
to Outlet A following historic
drainage patterns.

Pre-developed data referenced
from Daniels Commercial drainage
report by Roberts Eng. (2019,
2020)
Designed onsite runoff to north
along Ardmore Road following
historic drainage patterns
Rainfall Event Data
Outlet D
Onsite Runoff (C)
Outlet B
Outlet A
Outlet Location
Pre- vs. Post-Development Peak Flow Summary - OUTLETS
Roadside bioretention
swales, StormTech
Chamber:
(A =257' x 52')
Detention Basin with
metered SD outlet.

Underground
bioretention trench
along basin bottom
Roadside bioretention
swale
Antecedent Moisture Condition
2 2022_Ardmore Drainage Calculations_NEW infilt rates Page 784 of 1344 Page 1 of 2 City Council Agenda April 21, 2026 Ardmore Project
Location: Paso Robles, CA
Project: 0751-0005 Ardmore
Date: 2/16/2022
By: ZKP
Overall Hydrologic Calculations - SBUH method in HydroCAD WSHD Outlet
Location
Total Area
(sf)
Total Area
(ac) Weighted CN Land Type Description
Time of Conc.
(min) Storm Flow, Q (cfs)
2 YR 31.27
10 YR 55.32
25 YR 62.54
50 YR 72.16
100 YR 76.97
95th -
2 YR 1.24
10 YR 6.44
25 YR 10.29
50 YR 13.39
100 YR 16.70
95th Data Unknown
2 YR 1.02
10 YR 2.11
25 YR 2.46
50 YR 2.97
100 YR 3.54
95th -
2 YR 0.56
10 YR 2.94
25 YR 4.70
50 YR 6.11
100 YR 7.62
95th 0.01
2 YR 0.15
10 YR 0.74
25 YR 1.17
50 YR 1.52
100 YR 1.89
Subtotal 3,106,984 71.33
DMA Outlet
Location
Total Area
(sf)
Total Area
(ac) Weighted CN Land Type Description
Time of Conc.
(min) Storm Flow, Q (cfs)
95th -
2 YR 0.48
10 YR 4.58
25 YR 8.79
50 YR 11.25
100 YR 13.51
95th -
2 YR 0.04
10 YR 0.59
25 YR 1.65
50 YR 2.53
100 YR 3.42
95th 0.03
2 YR 0.07
10 YR 0.12
25 YR 0.15
50 YR 0.18
100 YR 0.20
95th -
2 YR -
10 YR 0.54
25 YR 1.37
50 YR 3.36
100 YR 6.81
Subtotal 612,363 14.06
Developed
* Calculated time of concentrations values were found to be less than the minimum 6-minute standard set by the City of Paso Robles Standards.

EX1
(offsite)
EX1
(onsite)
2,494,621
312,111
C 11,941 0.27 Developed 98 6.00
D 165,076 3.79 Developed 95 6.00
B1 + B2 121,873 2.80 95 6.00
* Calculated time of concentrations values were found to be less than the minimum 6-minute standard set by the City of Paso Robles Standards.

Proposed/ Post-developed Hydrology - Land Use Data & Peak Flow

57.27 See Offsite
Hydrology
Calculations
(Rational
Method)

OFFSITE
RUN-ON
Undeveloped.

Rural grassland/
open space, few
trees

11.04 Outlet A
(Exist. double
24" SD pipes)

7.17 74 6.00
ONSITE
Undeveloped.

Rural grassland/
open space with
few trees
(Data referenced from 2019 Daniels Commercial
drainage report by Roberts Engineering - see
"Tate Property/ Offsite flow from east"
calculations)
Developed 95 6.00
Onsite Runoff
(C)
(Sheet flow
runoff to north
along Ardmore
Rd)
Outlet B
(Exist 12"
culvert)
Undeveloped.

Rural grassland/
agricultural with
few trees

6.00 EX4 34,918 0.80
Outlet D
(Surface
runoff/ sheet
flow to
northwest)
74 Mostly
undeveloped
(single ag
structure). Rural
grassland/
agricultural, few

6.00 EX3 142,459 3.27 74
** DMA C storm drain system has been designed to over-retain and detain stormwater to account for DMA E onsite stormwater runoff.

Outlet A
(Exist. double
24" SD pipes)
Outlet B
(Prop. curb
inlet at exist
12" culvert)
Outlet D
(Prop. basin
outlet with
metered flow
to northwest)
Onsite Runoff
(C)
(Sheet flow
runoff to north
along Ardmore
Rd)
Existing/ Pre-developed Hydrology - Land Use Data & Peak Flow A 313,474 7.20
EX2 122,877 2.82
2022_Ardmore Drainage Calculations_NEW infilt rates Page 785 of 1344 Page 2 of 2 City Council Agenda April 21, 2026 Ardmore Project
Location: Paso Robles, CA
Project: 0751-0005 Ardmore
Date: 2/16/2022
By: ZKP
Offsite Hydrologic Calculations - Rational method
2 YR 1.30 in/ hr
10 YR in/ hr 2.30
25 YR in/ hr 2.60
50 YR in/ hr 3.00
100 YR in/ hr 3.20
DMA Outlet
Location
Total Area
(sf)
Total Area
(ac) C
Land Type
Description
Time of
Conc. (min) Storm Intensity, I (in/hr) Flow, Q (cfs)
2 YR 1.30 31.27
10 YR 2.30 55.32
25 YR 2.60 62.54
50 YR 3.00 72.16
100 YR 3.20 76.97
2,494,621 57.27
Land Type C-Value
Rural
grass/ ag SF 0.42 2,494,621 Undeveloped
1,047,741
2,494,621 57.27 ac

0.42 Description C-value
Relief 0.20
Soil Infiltration 0.08
Vegetal Cover 0.06
Surface Storage 0.08
Total 0.42
Rainfall Event Data
* See 2022 County of San Luis Obispo Public
Improvement Standards H-4, Table 2
Outlet A
(Exist. double
24" SD pipes)
EX1 (offsite)
Subtotal
Existing/ Pre-developed Offsite Hydrology Conditions
* Calculated time of concentrations values were found to be less than the minimum 10-minute standard set by the 2022 County of San Luis Obispo Public Improvements Standards.

EX1
(offsite) 2,494,621 57.27 0.42

OFFSITE
RUN-ON
Undeveloped.

Rural grassland/
open space, few
trees

11.04 Area
ΣCA
Total DMA Area
Weighted C-Value
Undeveloped Area C-Value (SLO County detail H-3a)
Relatively flat land, with average slopes 0-5%
Slow to take up water, clay or shallow loam soils
Good to excellent - 90% or more area is good
grassland or equiv. cover
Low - well defined system of small drainage ways
with no ponds or marshes
Rural/ Ag
Land
2022_Ardmore Drainage Calculations_NEW infilt rates Page 1 of 1 Page 786 of 1344 City Council Agenda April 21, 2026 Project: 751-005 Ardmore
Date: 2/14/2022
By: ZKP
Existing/ Pre-developed Watershed Land Use
(For HydroCAD model use)
Land Type Total Area (sf) % of Total Area SF to Acre
Impervious (Imp) 3,223 0.5% 43,560
Pervious (P) 609,141 99.5%
Total Area 612,364 100.0%
Catchment Catchment Area
(sf) P/I % of Catchment
Breakdown
Area (sf)
Breakdown Area
(acre) Notes
P 100% 2,494,621 57.27
Imp 0% - -
P 100% 2,494,621 57.27
Imp 0% - -
 100% 2,494,621 57.27
.

Catchment Catchment Area
(sf) P/I % of Catchment
Breakdown
Area (sf)
Breakdown Area
(acre) Notes
P 100% 312,111 7.17
Imp 0% - -
P 100% 312,111 7.17
Imp 0% - -
 100% 312,111 7.17
.

Catchment Catchment Area
(sf) P/I % of Catchment
Breakdown
Area (sf)
Breakdown Area
(acre) Notes
P 98% 120,160 2.76
Imp 2% 2,717 0.06
P 98% 120,160 2.76
Imp 2% 2,717 0.06
 100% 122,877 2.82
.

Catchment Catchment Area
(sf) P/I % of Catchment
Breakdown
Area (sf)
Breakdown Area
(acre) Notes
P 100% 142,459 3.27
Imp 0% - -
P 100% 142,459 3.27
Imp 0% - -
 100% 142,459 3.27
.

Catchment Catchment Area
(sf) P/I % of Catchment
Breakdown
Area (sf)
Breakdown Area
(acre) Notes
P 99% 34,412 0.79
Imp 1% 506 0.01
P 99% 34,412 0.79
Imp 1% 506 0.01
 100% 34,918 0.80
.

71.33 3,106,984
Exist Outlet A
Exist Outlet B
Exist Outlet A
Surface runoff to
northeast
Exist Outlet B
Subtotal 122,877
EX4 34,918
Subtotal 142,459
EX3 142,459
EX2 122,877
EX1 (onsite) 312,111
Subtotal 312,111
Existing Watershed Area
Subtotal 34,918
EX1 (offsite) 2,494,621
Subtotal 2,494,621
Existing/ Pre-developed Site Summary (excludes EX1 offsite)

14.06 Total Area (ac)

0.07 13.98
2022_Ardmore Drainage Calculations_NEW infilt rates Page 787 of 1344 Page 1 of 1 City Council Agenda April 21, 2026 Project: 751-005 Ardmore
Date: 2/14/2022
By: ZKP
Proposed/ Post-developed DMA Land Use
(For HydroCAD model use)
Land Type Total Area (sf) % of Total Area SF to Acre
Impervious (Imp) 501,730 81.9% 43,560
Pervious (P) 110,633 18.1%
Total Area 612,363 100.0%
Catchment Catchment Area
(sf) P/I % of Catchment
Breakdown
Area (sf)
Breakdown Area
(acre) Notes
P 14% 37,042 0.85
Imp 86% 227,546 5.22
P 14% 6,844 0.16
Imp 86% 42,041 0.97
P 14% 43,886 1.01
Imp 86% 269,587 6.19
 100% 313,474 7.20
.

P 24% 15,178 0.35
Imp 76% 44,042 1.01
P 24% 1,256 0.03
Imp 76% 9,109 0.21
P 24% 16,434 0.38
Imp 76% 53,151 1.22
 100% 69,586 1.60
.

P 24% 4,163 0.10
Imp 76% 48,124 1.10
P 24% 4,163 0.10
Imp 76% 48,124 1.10
 100% 52,287 1.20
P 10% 2,633 0.06
Imp 90% 7,087 0.16
P 10% - -
Imp 90% 2,221 0.05
P 10% 2,633 0.06
Imp 90% 9,308 0.21
 100% 11,941 0.27
.

P 26% 43,517 1.00
Imp 74% 121,559 2.79
P 26% 43,517 1.00
Imp 74% 121,559 2.79
 100% 165,076 3.79
.
612,363 14.06
Subtotal (D) 165,076
Total Project Area
A1 264,589
A2
B1b
Subtotal (A)
Subtotal (B) 52,287
B2a 52,287
Basin w/ Bioretention,
Outlet D
Roadside Bioswale,
Run-off to the north
C2 2,221 Onsite run-off to the
north
Subtotal (C)
D1 165,076
11,941
Roadside Bioswale,
Outlet A 48,885
Proposed/ Post-developed Site Summary
C1 9,720
59,221
10,365
Subtotal (B) 69,586
313,474
B1a
StormTech Chambers,
Outlet B
Total Area (ac)

2.54 11.52

14.06 StormTech Chambers,
Outlet B
Roadside Bioswale,
Outlet B
StormTech Chambers,
Outlet A
2022_Ardmore Drainage Calculations_NEW infilt rates Page 788 of 1344 Page 1 of 2 City Council Agenda April 21, 2026 Project: 751-005 Ardmore
Date: 2/16/2022
By: ZKP
Time of Concentration calculations
References:
2022 County of San Luis Obispo Public Improvement Standard H-2 Watershed Outlet L (Mile) H (ft) tc (hr) tc (min)
EX1 (offsite) 0.54 152 0.18 11.04 6.00
EX1 (onsite) 0.11 19 0.07 4.06 6.00
EX2 Outlet B (Exist 12" culvert)
EX3 Outlet D (Surface runoff/
sheet flow to northwest) 0.11 19 0.06 3.89 6.00
EX4
Onsite Runoff (C)
(Sheet flow runoff to north
along Ardmore Rd)

0.05 6 0.05 2.74 6.00
DMA Outlet L (MI) H tc (hr) tc (min)
A Exist. Dbl. 24" SD pipes 0.11 13.0 0.08 4.77 6.00
B Proposed Curb Inlet 0.06 3.9 0.06 3.77 6.00
C Onsite Runoff 0.09 4.7 0.09 5.49 6.00
D Basin Outlet 0.13 15.0 0.08 4.97 6.00
Existing Conditions
Proposed Conditions
City of Paso
Robles min.
tc (min)
City of Paso
Robles min.
tc (min)
Outlet A (Exist. double 24"
SD pipes)
(Data referenced from 2019 Daniels Commercial
drainage report by Roberts Engineering)
2022_Ardmore Drainage Calculations_NEW infilt rates Page 789 of 1344 Page 1 of 1 City Council Agenda April 21, 2026 Calculated using
Rational Method (see
report Appendix)
Exist WSHD 2 (EX2)
Data from Roberts Eng.
reports (2019/20) Exist WSHD 1
(EX1offsite)
EX1*
Exist WSHD 1 (onsite)
EX3
Exist WSHD 3
EX4
Exist WSHD 4
Routing Diagram for 2022_Ardmore_Exist
Prepared by Wallace Group, Printed 12/8/2022
HydroCAD® 10.20-2f s/n 05444 © 2022 HydroCAD Software Solutions LLC Subcat Reach Pond Link
EX1 (offsite) not included in this HyrdoCAD report
(See "Offsite Hydrology Calcs - Rational Method" by Wallace Group in Appendix C) EX2 not included in this HyrdoCAD report
(See data from 2019/2020 Daniels Woodlands drainage reports by Roberts Engineering, referenced in "Overall Hydrology Calculations" by Wallace Group in Appendix C)

EXISTING ROUTING DIAGRAM

2022_Ardmore_Exist Table of Contents
Prepared by Wallace Group Printed 12/8/2022
HydroCAD® 10.20-2f s/n 05444 © 2022 HydroCAD Software Solutions LLC

TABLE OF CONTENTS
Project Reports
1 Routing Diagram
2 Rainfall Events Listing (selected events)
3 Area Listing (all nodes)
4 Soil Listing (all nodes)
5 Ground Covers (all nodes)
25-YR Event
6 Node Listing
7 Subcat EX1*: Exist WSHD 1 (onsite)
8 Subcat EX3: Exist WSHD 3
9 Subcat EX4: Exist WSHD 4
50-YR Event
10 Node Listing
11 Subcat EX1*: Exist WSHD 1 (onsite)
12 Subcat EX3: Exist WSHD 3
13 Subcat EX4: Exist WSHD 4
100-YR Event
14 Node Listing
15 Subcat EX1*: Exist WSHD 1 (onsite)
16 Subcat EX3: Exist WSHD 3
17 Subcat EX4: Exist WSHD 4

2022_Ardmore_Exist
Prepared by Wallace Group Printed 12/8/2022
HydroCAD® 10.20-2f s/n 05444 © 2022 HydroCAD Software Solutions LLC Page 2 Rainfall Events Listing (selected events)
Event# Event
Name
Storm Type Curve Mode Duration
(hours)
B/B Depth
(inches)
AMC
1 25-YR Type I 24-hr Default 24.00 1 4.70 2
2 50-YR Type I 24-hr Default 24.00 1 5.42 2
3 100-YR Type I 24-hr Default 24.00 1 6.16 2

2022_Ardmore_Exist
Prepared by Wallace Group Printed 12/8/2022
HydroCAD® 10.20-2f s/n 05444 © 2022 HydroCAD Software Solutions LLC Page 3 Area Listing (all nodes)
Area
(acres)
CN Description
(subcatchment-numbers)

0.012 98 Ag Building, HSG C (EX4)

11.225 74 Pasture/grassland/range, Good, HSG C (EX1*, EX3, EX4)

11.237 74 TOTAL AREA

2022_Ardmore_Exist
Prepared by Wallace Group Printed 12/8/2022
HydroCAD® 10.20-2f s/n 05444 © 2022 HydroCAD Software Solutions LLC Page 4 Soil Listing (all nodes)
Area
(acres)
Soil
Group
Subcatchment
Numbers

0.000 HSG A

0.000 HSG B

11.237 HSG C EX1*, EX3, EX4

0.000 HSG D

0.000 Other

11.237 TOTAL AREA

2022_Ardmore_Exist
Prepared by Wallace Group Printed 12/8/2022
HydroCAD® 10.20-2f s/n 05444 © 2022 HydroCAD Software Solutions LLC Page 5 Ground Covers (all nodes)
HSG-A
(acres)
HSG-B
(acres)
HSG-C
(acres)
HSG-D
(acres)
Other
(acres)
Total
(acres)
Ground
Cover
Subcatchment
Numbers

0.000 0.000 0.012 0.000 0.000 0.012 Ag Building EX
4 0.000 0.000 11.225 0.000 0.000 11.225 Pasture/grassland/range, Good EX 1*,
EX
3,
EX
4 0.000 0.000 11.237 0.000 0.000 11.237 TOTAL AREA

2022_Ardmore_Exist Type I 24-hr 25-YR Rainfall=4.70"
Prepared by Wallace Group Printed 12/8/2022
HydroCAD® 10.20-2f s/n 05444 © 2022 HydroCAD Software Solutions LLC Page 6 Time span=0.00-72.00 hrs, dt=0.01 hrs, 7201 points
Runoff by SBUH method, Split Pervious/Imperv.

Reach routing by Dyn-Stor-Ind method - Pond routing by Dyn-Stor-Ind method Subcatchment EX1*: Exist WSHD 1 (onsite)Runoff Area=312,111 sf 0.00% Impervious Runoff Depth=2.13" Tc=6.0 min CN=74/0 Runoff=10.29 cfs 1.270 af
Subcatchment EX3: Exist WSHD 3 Runoff Area=142,459 sf 0.00% Impervious Runoff Depth=2.13" Tc=6.0 min CN=74/0 Runoff=4.70 cfs 0.580 af
Subcatchment EX4: Exist WSHD 4 Runoff Area=34,918 sf 1.45% Impervious Runoff Depth=2.16" Tc=6.0 min CN=74/98 Runoff=1.17 cfs 0.144 af
Total Runoff Area = 11.237 ac Runoff Volume = 1.994 af Average Runoff Depth = 2.13"

99.90% Pervious = 11.225 ac 0.10% Impervious = 0.012 ac

2022_Ardmore_Exist Type I 24-hr 25-YR Rainfall=4.70"
Prepared by Wallace Group Printed 12/8/2022
HydroCAD® 10.20-2f s/n 05444 © 2022 HydroCAD Software Solutions LLC Page 7 Summary for Subcatchment EX1*: Exist WSHD 1 (onsite)
Runoff = 10.29 cfs @ 9.95 hrs, Volume= 1.270 af, Depth= 2.13" Routed to nonexistent node A
Runoff by SBUH method, Split Pervious/Imperv., Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type I 24-hr 25-YR Rainfall=4.70"
Area (sf) CN Description
312,111 74 Pasture/grassland/range, Good, HSG C
312,111 74 100.00% Pervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)

6.0 Direct Entry, Calculated
Subcatchment EX1*: Exist WSHD 1 (onsite)
Runoff
Hydrograph
Time (hours)
727068666462605856545250484644424038363432302826242220181614121086420 Flow (cfs)
11 10
9 8
7 6
5 4
3 2
1 0
Type I 24-hr
25-YR Rainfall=4.70"
Runoff Area=312,111 sf
Runoff Volume=1.270 af
Runoff Depth=2.13"
Tc=6.0 min
CN=74/0

10.29 cfs

2022_Ardmore_Exist Type I 24-hr 25-YR Rainfall=4.70"
Prepared by Wallace Group Printed 12/8/2022
HydroCAD® 10.20-2f s/n 05444 © 2022 HydroCAD Software Solutions LLC Page 8 Summary for Subcatchment EX3: Exist WSHD 3
Runoff = 4.70 cfs @ 9.95 hrs, Volume= 0.580 af, Depth= 2.13" Routed to nonexistent node D
Runoff by SBUH method, Split Pervious/Imperv., Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type I 24-hr 25-YR Rainfall=4.70"
Area (sf) CN Description
142,459 74 Pasture/grassland/range, Good, HSG C
142,459 74 100.00% Pervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)

6.0 Direct Entry, City of Paso Robles minimum
Subcatchment EX3: Exist WSHD 3
Runoff
Hydrograph
Time (hours)
727068666462605856545250484644424038363432302826242220181614121086420 Flow (cfs)
5 4
3 2
1 0
Type I 24-hr
25-YR Rainfall=4.70"
Runoff Area=142,459 sf
Runoff Volume=0.580 af
Runoff Depth=2.13"
Tc=6.0 min
CN=74/0

4.70 cfs

2022_Ardmore_Exist Type I 24-hr 25-YR Rainfall=4.70"
Prepared by Wallace Group Printed 12/8/2022
HydroCAD® 10.20-2f s/n 05444 © 2022 HydroCAD Software Solutions LLC Page 9 Summary for Subcatchment EX4: Exist WSHD 4
Runoff = 1.17 cfs @ 9.95 hrs, Volume= 0.144 af, Depth= 2.16" Routed to nonexistent node C
Runoff by SBUH method, Split Pervious/Imperv., Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type I 24-hr 25-YR Rainfall=4.70"
Area (sf) CN Description
34,412 74 Pasture/grassland/range, Good, HSG C
* 506 98 Ag Building, HSG C
34,918 74 Weighted Average
34,412 74 98.55% Pervious Area
506 98 1.45% Impervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)

6.0 Direct Entry, City of Paso Robles minimum
Subcatchment EX4: Exist WSHD 4
Runoff
Hydrograph
Time (hours)
727068666462605856545250484644424038363432302826242220181614121086420 Flow (cfs)
1 0
Type I 24-hr
25-YR Rainfall=4.70"
Runoff Area=34,918 sf
Runoff Volume=0.144 af
Runoff Depth=2.16"
Tc=6.0 min
CN=74/98

1.17 cfs

2022_Ardmore_Exist Type I 24-hr 50-YR Rainfall=5.42"
Prepared by Wallace Group Printed 12/8/2022
HydroCAD® 10.20-2f s/n 05444 © 2022 HydroCAD Software Solutions LLC Page 10 Time span=0.00-72.00 hrs, dt=0.01 hrs, 7201 points
Runoff by SBUH method, Split Pervious/Imperv.

Reach routing by Dyn-Stor-Ind method - Pond routing by Dyn-Stor-Ind method Subcatchment EX1*: Exist WSHD 1 (onsite)Runoff Area=312,111 sf 0.00% Impervious Runoff Depth=2.70" Tc=6.0 min CN=74/0 Runoff=13.39 cfs 1.614 af
Subcatchment EX3: Exist WSHD 3 Runoff Area=142,459 sf 0.00% Impervious Runoff Depth=2.70" Tc=6.0 min CN=74/0 Runoff=6.11 cfs 0.737 af
Subcatchment EX4: Exist WSHD 4 Runoff Area=34,918 sf 1.45% Impervious Runoff Depth=2.74" Tc=6.0 min CN=74/98 Runoff=1.52 cfs 0.183 af
Total Runoff Area = 11.237 ac Runoff Volume = 2.534 af Average Runoff Depth = 2.71"

99.90% Pervious = 11.225 ac 0.10% Impervious = 0.012 ac

2022_Ardmore_Exist Type I 24-hr 50-YR Rainfall=5.42"
Prepared by Wallace Group Printed 12/8/2022
HydroCAD® 10.20-2f s/n 05444 © 2022 HydroCAD Software Solutions LLC Page 11 Summary for Subcatchment EX1*: Exist WSHD 1 (onsite)
Runoff = 13.39 cfs @ 9.95 hrs, Volume= 1.614 af, Depth= 2.70" Routed to nonexistent node A
Runoff by SBUH method, Split Pervious/Imperv., Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type I 24-hr 50-YR Rainfall=5.42"
Area (sf) CN Description
312,111 74 Pasture/grassland/range, Good, HSG C
312,111 74 100.00% Pervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)

6.0 Direct Entry, Calculated
Subcatchment EX1*: Exist WSHD 1 (onsite)
Runoff
Hydrograph
Time (hours)
727068666462605856545250484644424038363432302826242220181614121086420 Flow (cfs)
14 13
12 11
10 9
8 7
6 5
4 3
2 1
0 Type I 24-hr
50-YR Rainfall=5.42"
Runoff Area=312,111 sf
Runoff Volume=1.614 af
Runoff Depth=2.70"
Tc=6.0 min
CN=74/0

13.39 cfs

2022_Ardmore_Exist Type I 24-hr 50-YR Rainfall=5.42"
Prepared by Wallace Group Printed 12/8/2022
HydroCAD® 10.20-2f s/n 05444 © 2022 HydroCAD Software Solutions LLC Page 12 Summary for Subcatchment EX3: Exist WSHD 3
Runoff = 6.11 cfs @ 9.95 hrs, Volume= 0.737 af, Depth= 2.70" Routed to nonexistent node D
Runoff by SBUH method, Split Pervious/Imperv., Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type I 24-hr 50-YR Rainfall=5.42"
Area (sf) CN Description
142,459 74 Pasture/grassland/range, Good, HSG C
142,459 74 100.00% Pervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)

6.0 Direct Entry, City of Paso Robles minimum
Subcatchment EX3: Exist WSHD 3
Runoff
Hydrograph
Time (hours)
727068666462605856545250484644424038363432302826242220181614121086420 Flow (cfs)
6 5
4 3
2 1
0 Type I 24-hr
50-YR Rainfall=5.42"
Runoff Area=142,459 sf
Runoff Volume=0.737 af
Runoff Depth=2.70"
Tc=6.0 min
CN=74/0

6.11 cfs

2022_Ardmore_Exist Type I 24-hr 50-YR Rainfall=5.42"
Prepared by Wallace Group Printed 12/8/2022
HydroCAD® 10.20-2f s/n 05444 © 2022 HydroCAD Software Solutions LLC Page 13 Summary for Subcatchment EX4: Exist WSHD 4
Runoff = 1.52 cfs @ 9.95 hrs, Volume= 0.183 af, Depth= 2.74" Routed to nonexistent node C
Runoff by SBUH method, Split Pervious/Imperv., Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type I 24-hr 50-YR Rainfall=5.42"
Area (sf) CN Description
34,412 74 Pasture/grassland/range, Good, HSG C
* 506 98 Ag Building, HSG C
34,918 74 Weighted Average
34,412 74 98.55% Pervious Area
506 98 1.45% Impervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)

6.0 Direct Entry, City of Paso Robles minimum
Subcatchment EX4: Exist WSHD 4
Runoff
Hydrograph
Time (hours)
727068666462605856545250484644424038363432302826242220181614121086420 Flow (cfs)
1 0
Type I 24-hr
50-YR Rainfall=5.42"
Runoff Area=34,918 sf
Runoff Volume=0.183 af
Runoff Depth=2.74"
Tc=6.0 min
CN=74/98

1.52 cfs

2022_Ardmore_Exist Type I 24-hr 100-YR Rainfall=6.16"
Prepared by Wallace Group Printed 12/8/2022
HydroCAD® 10.20-2f s/n 05444 © 2022 HydroCAD Software Solutions LLC Page 14 Time span=0.00-72.00 hrs, dt=0.01 hrs, 7201 points
Runoff by SBUH method, Split Pervious/Imperv.

Reach routing by Dyn-Stor-Ind method - Pond routing by Dyn-Stor-Ind method Subcatchment EX1*: Exist WSHD 1 (onsite)Runoff Area=312,111 sf 0.00% Impervious Runoff Depth=3.32" Tc=6.0 min CN=74/0 Runoff=16.70 cfs 1.982 af
Subcatchment EX3: Exist WSHD 3 Runoff Area=142,459 sf 0.00% Impervious Runoff Depth=3.32" Tc=6.0 min CN=74/0 Runoff=7.62 cfs 0.905 af
Subcatchment EX4: Exist WSHD 4 Runoff Area=34,918 sf 1.45% Impervious Runoff Depth=3.36" Tc=6.0 min CN=74/98 Runoff=1.89 cfs 0.224 af
Total Runoff Area = 11.237 ac Runoff Volume = 3.111 af Average Runoff Depth = 3.32"

99.90% Pervious = 11.225 ac 0.10% Impervious = 0.012 ac

2022_Ardmore_Exist Type I 24-hr 100-YR Rainfall=6.16"
Prepared by Wallace Group Printed 12/8/2022
HydroCAD® 10.20-2f s/n 05444 © 2022 HydroCAD Software Solutions LLC Page 15 Summary for Subcatchment EX1*: Exist WSHD 1 (onsite)
Runoff = 16.70 cfs @ 9.95 hrs, Volume= 1.982 af, Depth= 3.32" Routed to nonexistent node A
Runoff by SBUH method, Split Pervious/Imperv., Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type I 24-hr 100-YR Rainfall=6.16"
Area (sf) CN Description
312,111 74 Pasture/grassland/range, Good, HSG C
312,111 74 100.00% Pervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)

6.0 Direct Entry, Calculated
Subcatchment EX1*: Exist WSHD 1 (onsite)
Runoff
Hydrograph
Time (hours)
727068666462605856545250484644424038363432302826242220181614121086420 Flow (cfs)
18 17
16 15
14 13
12 11
10 9
8 7
6 5
4 3
2 1
0 Type I 24-hr
100-YR Rainfall=6.16"
Runoff Area=312,111 sf
Runoff Volume=1.982 af
Runoff Depth=3.32"
Tc=6.0 min
CN=74/0

16.70 cfs

2022_Ardmore_Exist Type I 24-hr 100-YR Rainfall=6.16"
Prepared by Wallace Group Printed 12/8/2022
HydroCAD® 10.20-2f s/n 05444 © 2022 HydroCAD Software Solutions LLC Page 16 Summary for Subcatchment EX3: Exist WSHD 3
Runoff = 7.62 cfs @ 9.95 hrs, Volume= 0.905 af, Depth= 3.32" Routed to nonexistent node D
Runoff by SBUH method, Split Pervious/Imperv., Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type I 24-hr 100-YR Rainfall=6.16"
Area (sf) CN Description
142,459 74 Pasture/grassland/range, Good, HSG C
142,459 74 100.00% Pervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)

6.0 Direct Entry, City of Paso Robles minimum
Subcatchment EX3: Exist WSHD 3
Runoff
Hydrograph
Time (hours)
727068666462605856545250484644424038363432302826242220181614121086420 Flow (cfs)
8 7
6 5
4 3
2 1
0 Type I 24-hr
100-YR Rainfall=6.16"
Runoff Area=142,459 sf
Runoff Volume=0.905 af
Runoff Depth=3.32"
Tc=6.0 min
CN=74/0

7.62 cfs

2022_Ardmore_Exist Type I 24-hr 100-YR Rainfall=6.16"
Prepared by Wallace Group Printed 12/8/2022
HydroCAD® 10.20-2f s/n 05444 © 2022 HydroCAD Software Solutions LLC Page 17 Summary for Subcatchment EX4: Exist WSHD 4
Runoff = 1.89 cfs @ 9.95 hrs, Volume= 0.224 af, Depth= 3.36" Routed to nonexistent node C
Runoff by SBUH method, Split Pervious/Imperv., Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type I 24-hr 100-YR Rainfall=6.16"
Area (sf) CN Description
34,412 74 Pasture/grassland/range, Good, HSG C
* 506 98 Ag Building, HSG C
34,918 74 Weighted Average
34,412 74 98.55% Pervious Area
506 98 1.45% Impervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)

6.0 Direct Entry, City of Paso Robles minimum
Subcatchment EX4: Exist WSHD 4
Runoff
Hydrograph
Time (hours)
727068666462605856545250484644424038363432302826242220181614121086420 Flow (cfs)
2 1
0 Type I 24-hr
100-YR Rainfall=6.16"
Runoff Area=34,918 sf
Runoff Volume=0.224 af
Runoff Depth=3.36"
Tc=6.0 min
CN=74/98

1.89 cfs

A1
DMA A-1
A2
DMA A-2
B1a
Catch B-1a
B1b
Catch B-1b
B2a
Catch B-2a
C1
Catch C-1
C2
Catch C-2
D1
DMA D-1
LID A1
A-1 Chambers
LID A2
A-2 Bioretention
LID B1a
B-1a Chambers
LID B1b
B-1b Bioretention
LID B2a
B-2a Chambers
LID C2
C-1 Bioretention
LID D
Basin
A
Outlet A
B
Outlet B
C
Outlet C
D
Outlet D
Routing Diagram for 2022_Ardmore
Prepared by Wallace Group, Printed 2/14/2023
HydroCAD® 10.20-2f s/n 05444 © 2022 HydroCAD Software Solutions LLC Subcat Reach Pond Link

PROPOSED ROUTING DIAGRAM

2022_Ardmore Table of Contents
Prepared by Wallace Group Printed 2/14/2023
HydroCAD® 10.20-2f s/n 05444 © 2022 HydroCAD Software Solutions LLC

TABLE OF CONTENTS
Project Reports
1 Routing Diagram
2 Rainfall Events Listing (selected events)
3 Area Listing (all nodes)
4 Soil Listing (all nodes)
5 Ground Covers (all nodes)
6 Pipe Listing (all nodes)
25-YR Event
7 Node Listing
8 Link A: Outlet A
9 Link B: Outlet B
10 Link C: Outlet C
11 Link D: Outlet D
50-YR Event
12 Node Listing
13 Link A: Outlet A
14 Link B: Outlet B
15 Link C: Outlet C
16 Link D: Outlet D
100-YR Event
17 Node Listing
18 Link A: Outlet A
19 Link B: Outlet B
20 Link C: Outlet C
21 Link D: Outlet D

2022_Ardmore
Prepared by Wallace Group Printed 2/14/2023
HydroCAD® 10.20-2f s/n 05444 © 2022 HydroCAD Software Solutions LLC Page 2 Rainfall Events Listing (selected events)
Event# Event
Name
Storm Type Curve Mode Duration
(hours)
B/B Depth
(inches)
AMC
1 25-YR Type I 24-hr Default 24.00 1 4.70 2
2 50-YR Type I 24-hr Default 24.00 1 5.42 2
3 100-YR Type I 24-hr Default 24.00 1 6.16 2

2022_Ardmore
Prepared by Wallace Group Printed 2/14/2023
HydroCAD® 10.20-2f s/n 05444 © 2022 HydroCAD Software Solutions LLC Page 3 Area Listing (all nodes)
Area
(acres)
CN Description
(subcatchment-numbers)

8.728 98 Impervious, HSG C (A1, A2, B1a, B1b, B2a, C1, C2)

2.540 79 Landscaped, 50-75% Grass cover, Fair, HSG C (A1, A2, B1a, B1b, B2a, C1, D1)

2.791 98 Paved parking, HSG C (D1)

14.058 95 TOTAL AREA

2022_Ardmore
Prepared by Wallace Group Printed 2/14/2023
HydroCAD® 10.20-2f s/n 05444 © 2022 HydroCAD Software Solutions LLC Page 4 Soil Listing (all nodes)
Area
(acres)
Soil
Group
Subcatchment
Numbers

0.000 HSG A

0.000 HSG B

14.058 HSG C A1, A2, B1a, B1b, B2a, C1, C2, D1

0.000 HSG D

0.000 Other

14.058 TOTAL AREA

2022_Ardmore
Prepared by Wallace Group Printed 2/14/2023
HydroCAD® 10.20-2f s/n 05444 © 2022 HydroCAD Software Solutions LLC Page 5 Ground Covers (all nodes)
HSG-A
(acres)
HSG-B
(acres)
HSG-C
(acres)
HSG-D
(acres)
Other
(acres)
Total
(acres)
Ground
Cover
Subcatc
Number

0.000 0.000 8.728 0.000 0.000 8.728 Impervious

0.000 0.000 2.540 0.000 0.000 2.540 Landscaped, 50-75% Grass cover, Fair

0.000 0.000 2.791 0.000 0.000 2.791 Paved parking

0.000 0.000 14.058 0.000 0.000 14.058 TOTAL AREA

2022_Ardmore
Prepared by Wallace Group Printed 2/14/2023
HydroCAD® 10.20-2f s/n 05444 © 2022 HydroCAD Software Solutions LLC Page 6 Pipe Listing (all nodes)
Line# Node
Number
In-Invert
(feet)
Out-Invert
(feet)
Length
(feet)
Slope
(ft/ft)
n Width
(inches)
Diam/Height
(inches)
Inside-Fill
(inches)
1 LID A1 819.00 818.50 35.0 0.0143 0.012 0.0 18.0 0.0
2 LID B1a 822.63 822.50 50.0 0.0026 0.012 0.0 18.0 0.0
3 LID B2a 822.19 821.89 30.0 0.0100 0.012 0.0 18.0 0.0

2022_Ardmore Type I 24-hr 25-YR Rainfall=4.70"
Prepared by Wallace Group Printed 2/14/2023
HydroCAD® 10.20-2f s/n 05444 © 2022 HydroCAD Software Solutions LLC Page 7 Time span=0.00-72.00 hrs, dt=0.01 hrs, 7201 points
Runoff by SBUH method, Split Pervious/Imperv.

Reach routing by Dyn-Stor-Ind method - Pond routing by Dyn-Stor-Ind method Link A: Outlet A Inflow=8.79 cfs 1.613 af
Primary=8.79 cfs 1.613 af
Link B: Outlet B Inflow=1.65 cfs 0.371 af
Primary=1.65 cfs 0.371 af
Link C: Outlet C Inflow=0.15 cfs 0.019 af
Primary=0.15 cfs 0.019 af
Link D: Outlet D Inflow=1.37 cfs 0.601 af
Primary=1.37 cfs 0.601 af

2022_Ardmore Type I 24-hr 25-YR Rainfall=4.70"
Prepared by Wallace Group Printed 2/14/2023
HydroCAD® 10.20-2f s/n 05444 © 2022 HydroCAD Software Solutions LLC Page 8 Summary for Link A: Outlet A
Inflow Area = 7.196 ac, 86.00% Impervious, Inflow Depth = 2.69" for 25-YR event Inflow = 8.79 cfs @ 10.13 hrs, Volume= 1.613 af
Primary = 8.79 cfs @ 10.13 hrs, Volume= 1.613 af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Link A: Outlet A
Inflow
Primary
Hydrograph
Time (hours)
727068666462605856545250484644424038363432302826242220181614121086420 Flow (cfs)
9 8
7 6
5 4
3 2
1 0
Inflow Area=7.196 ac

8.79 cfs

8.79 cfs

2022_Ardmore Type I 24-hr 25-YR Rainfall=4.70"
Prepared by Wallace Group Printed 2/14/2023
HydroCAD® 10.20-2f s/n 05444 © 2022 HydroCAD Software Solutions LLC Page 9 Summary for Link B: Outlet B
Inflow Area = 2.798 ac, 83.10% Impervious, Inflow Depth = 1.59" for 25-YR event Inflow = 1.65 cfs @ 10.10 hrs, Volume= 0.371 af
Primary = 1.65 cfs @ 10.10 hrs, Volume= 0.371 af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Link B: Outlet B
Inflow
Primary
Hydrograph
Time (hours)
727068666462605856545250484644424038363432302826242220181614121086420 Flow (cfs)
1 0
Inflow Area=2.798 ac

1.65 cfs

1.65 cfs

2022_Ardmore Type I 24-hr 25-YR Rainfall=4.70"
Prepared by Wallace Group Printed 2/14/2023
HydroCAD® 10.20-2f s/n 05444 © 2022 HydroCAD Software Solutions LLC Page 10 Summary for Link C: Outlet C
Inflow Area = 0.274 ac, 77.95% Impervious, Inflow Depth = 0.83" for 25-YR event Inflow = 0.15 cfs @ 9.94 hrs, Volume= 0.019 af
Primary = 0.15 cfs @ 9.94 hrs, Volume= 0.019 af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Link C: Outlet C
Inflow
Primary
Hydrograph
Time (hours)
727068666462605856545250484644424038363432302826242220181614121086420 Flow (cfs)

0.17 0.16

0.15 0.14

0.13 0.12

0.11 0.1

0.09 0.08

0.07 0.06

0.05 0.04

0.03 0.02

0.01 0
Inflow Area=0.274 ac

0.15 cfs

0.15 cfs

2022_Ardmore Type I 24-hr 25-YR Rainfall=4.70"
Prepared by Wallace Group Printed 2/14/2023
HydroCAD® 10.20-2f s/n 05444 © 2022 HydroCAD Software Solutions LLC Page 11 Summary for Link D: Outlet D
Inflow Area = 3.790 ac, 73.64% Impervious, Inflow Depth = 1.90" for 25-YR event Inflow = 1.37 cfs @ 10.79 hrs, Volume= 0.601 af
Primary = 1.37 cfs @ 10.79 hrs, Volume= 0.601 af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Link D: Outlet D
Inflow
Primary
Hydrograph
Time (hours)
727068666462605856545250484644424038363432302826242220181614121086420 Flow (cfs)
1 0
Inflow Area=3.790 ac

1.37 cfs

1.37 cfs

2022_Ardmore Type I 24-hr 50-YR Rainfall=5.42"
Prepared by Wallace Group Printed 2/14/2023
HydroCAD® 10.20-2f s/n 05444 © 2022 HydroCAD Software Solutions LLC Page 12 Time span=0.00-72.00 hrs, dt=0.01 hrs, 7201 points
Runoff by SBUH method, Split Pervious/Imperv.

Reach routing by Dyn-Stor-Ind method - Pond routing by Dyn-Stor-Ind method Link A: Outlet A Inflow=11.25 cfs 2.003 af
Primary=11.25 cfs 2.003 af
Link B: Outlet B Inflow=2.53 cfs 0.527 af
Primary=2.53 cfs 0.527 af
Link C: Outlet C Inflow=0.18 cfs 0.022 af
Primary=0.18 cfs 0.022 af
Link D: Outlet D Inflow=3.36 cfs 0.819 af
Primary=3.36 cfs 0.819 af

2022_Ardmore Type I 24-hr 50-YR Rainfall=5.42"
Prepared by Wallace Group Printed 2/14/2023
HydroCAD® 10.20-2f s/n 05444 © 2022 HydroCAD Software Solutions LLC Page 13 Summary for Link A: Outlet A
Inflow Area = 7.196 ac, 86.00% Impervious, Inflow Depth = 3.34" for 50-YR event Inflow = 11.25 cfs @ 10.08 hrs, Volume= 2.003 af
Primary = 11.25 cfs @ 10.08 hrs, Volume= 2.003 af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Link A: Outlet A
Inflow
Primary
Hydrograph
Time (hours)
727068666462605856545250484644424038363432302826242220181614121086420 Flow (cfs)
12 11
10 9
8 7
6 5
4 3
2 1
0 Inflow Area=7.196 ac

11.25 cfs

11.25 cfs

2022_Ardmore Type I 24-hr 50-YR Rainfall=5.42"
Prepared by Wallace Group Printed 2/14/2023
HydroCAD® 10.20-2f s/n 05444 © 2022 HydroCAD Software Solutions LLC Page 14 Summary for Link B: Outlet B
Inflow Area = 2.798 ac, 83.10% Impervious, Inflow Depth = 2.26" for 50-YR event Inflow = 2.53 cfs @ 10.05 hrs, Volume= 0.527 af
Primary = 2.53 cfs @ 10.05 hrs, Volume= 0.527 af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Link B: Outlet B
Inflow
Primary
Hydrograph
Time (hours)
727068666462605856545250484644424038363432302826242220181614121086420 Flow (cfs)
2 1
0 Inflow Area=2.798 ac

2.53 cfs

2.53 cfs

2022_Ardmore Type I 24-hr 50-YR Rainfall=5.42"
Prepared by Wallace Group Printed 2/14/2023
HydroCAD® 10.20-2f s/n 05444 © 2022 HydroCAD Software Solutions LLC Page 15 Summary for Link C: Outlet C
Inflow Area = 0.274 ac, 77.95% Impervious, Inflow Depth = 0.96" for 50-YR event Inflow = 0.18 cfs @ 9.94 hrs, Volume= 0.022 af
Primary = 0.18 cfs @ 9.94 hrs, Volume= 0.022 af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Link C: Outlet C
Inflow
Primary
Hydrograph
Time (hours)
727068666462605856545250484644424038363432302826242220181614121086420 Flow (cfs)

0.19 0.18

0.17 0.16

0.15 0.14

0.13 0.12

0.11 0.1

0.09 0.08

0.07 0.06

0.05 0.04

0.03 0.02

0.01 0
Inflow Area=0.274 ac

0.18 cfs

0.18 cfs

2022_Ardmore Type I 24-hr 50-YR Rainfall=5.42"
Prepared by Wallace Group Printed 2/14/2023
HydroCAD® 10.20-2f s/n 05444 © 2022 HydroCAD Software Solutions LLC Page 16 Summary for Link D: Outlet D
Inflow Area = 3.790 ac, 73.64% Impervious, Inflow Depth = 2.59" for 50-YR event Inflow = 3.36 cfs @ 10.26 hrs, Volume= 0.819 af
Primary = 3.36 cfs @ 10.26 hrs, Volume= 0.819 af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Link D: Outlet D
Inflow
Primary
Hydrograph
Time (hours)
727068666462605856545250484644424038363432302826242220181614121086420 Flow (cfs)
3 2
1 0
Inflow Area=3.790 ac

3.36 cfs

3.36 cfs

2022_Ardmore Type I 24-hr 100-YR Rainfall=6.16"
Prepared by Wallace Group Printed 2/14/2023
HydroCAD® 10.20-2f s/n 05444 © 2022 HydroCAD Software Solutions LLC Page 17 Time span=0.00-72.00 hrs, dt=0.01 hrs, 7201 points
Runoff by SBUH method, Split Pervious/Imperv.

Reach routing by Dyn-Stor-Ind method - Pond routing by Dyn-Stor-Ind method Link A: Outlet A Inflow=13.51 cfs 2.409 af
Primary=13.51 cfs 2.409 af
Link B: Outlet B Inflow=3.42 cfs 0.690 af
Primary=3.42 cfs 0.690 af
Link C: Outlet C Inflow=0.20 cfs 0.026 af
Primary=0.20 cfs 0.026 af
Link D: Outlet D Inflow=6.81 cfs 1.045 af
Primary=6.81 cfs 1.045 af

2022_Ardmore Type I 24-hr 100-YR Rainfall=6.16"
Prepared by Wallace Group Printed 2/14/2023
HydroCAD® 10.20-2f s/n 05444 © 2022 HydroCAD Software Solutions LLC Page 18 Summary for Link A: Outlet A
Inflow Area = 7.196 ac, 86.00% Impervious, Inflow Depth = 4.02" for 100-YR event Inflow = 13.51 cfs @ 10.05 hrs, Volume= 2.409 af
Primary = 13.51 cfs @ 10.05 hrs, Volume= 2.409 af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Link A: Outlet A
Inflow
Primary
Hydrograph
Time (hours)
727068666462605856545250484644424038363432302826242220181614121086420 Flow (cfs)
15 14
13 12
11 10
9 8
7 6
5 4
3 2
1 0
Inflow Area=7.196 ac

13.51 cfs

13.51 cfs

2022_Ardmore Type I 24-hr 100-YR Rainfall=6.16"
Prepared by Wallace Group Printed 2/14/2023
HydroCAD® 10.20-2f s/n 05444 © 2022 HydroCAD Software Solutions LLC Page 19 Summary for Link B: Outlet B
Inflow Area = 2.798 ac, 83.10% Impervious, Inflow Depth = 2.96" for 100-YR event Inflow = 3.42 cfs @ 10.07 hrs, Volume= 0.690 af
Primary = 3.42 cfs @ 10.07 hrs, Volume= 0.690 af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Link B: Outlet B
Inflow
Primary
Hydrograph
Time (hours)
727068666462605856545250484644424038363432302826242220181614121086420 Flow (cfs)
3 2
1 0
Inflow Area=2.798 ac

3.42 cfs

3.42 cfs

2022_Ardmore Type I 24-hr 100-YR Rainfall=6.16"
Prepared by Wallace Group Printed 2/14/2023
HydroCAD® 10.20-2f s/n 05444 © 2022 HydroCAD Software Solutions LLC Page 20 Summary for Link C: Outlet C
Inflow Area = 0.274 ac, 77.95% Impervious, Inflow Depth = 1.13" for 100-YR event Inflow = 0.20 cfs @ 9.94 hrs, Volume= 0.026 af
Primary = 0.20 cfs @ 9.94 hrs, Volume= 0.026 af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Link C: Outlet C
Inflow
Primary
Hydrograph
Time (hours)
727068666462605856545250484644424038363432302826242220181614121086420 Flow (cfs)

0.22 0.21

0.2 0.19

0.18 0.17

0.16 0.15

0.14 0.13

0.12 0.11

0.1 0.09

0.08 0.07

0.06 0.05

0.04 0.03

0.02 0.01
0 Inflow Area=0.274 ac

0.20 cfs

0.20 cfs

2022_Ardmore Type I 24-hr 100-YR Rainfall=6.16"
Prepared by Wallace Group Printed 2/14/2023
HydroCAD® 10.20-2f s/n 05444 © 2022 HydroCAD Software Solutions LLC Page 21 Summary for Link D: Outlet D
Inflow Area = 3.790 ac, 73.64% Impervious, Inflow Depth = 3.31" for 100-YR event Inflow = 6.81 cfs @ 10.10 hrs, Volume= 1.045 af
Primary = 6.81 cfs @ 10.10 hrs, Volume= 1.045 af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Link D: Outlet D
Inflow
Primary
Hydrograph
Time (hours)
727068666462605856545250484644424038363432302826242220181614121086420 Flow (cfs)
7 6
5 4
3 2
1 0
Inflow Area=3.790 ac

6.81 cfs

6.81 cfs

HY-8 Culvert Analysis Report
Crossing Discharge Data
Discharge Selection Method: Specify Minimum, Design, and Maximum Flow Minimum Flow: 1 cfs
Design Flow: 62.54 cfs
Maximum Flow: 76.97 cfs

BYPASS CULVERT

Tailwater
Elevation = 823.35' BYPASS CULVERT

Property Line

BYPASS CULVERT

Table 1 - Summary of Culvert Flows at Crossing: Ardmore Double Culvert Headwater Elevation
(ft)
Total Discharge (cfs) Double 36 Discharge
(cfs)
Roadway Discharge
(cfs)
Iterations
823.30 1.00 1.00 0.00 1
823.33 8.60 8.60 0.00 1
823.39 16.19 16.19 0.00 1
823.49 23.79 23.79 0.00 1
823.63 31.39 31.37 0.04 4
823.79 38.98 38.69 0.29 4
823.96 46.58 45.60 0.97 5
824.13 54.18 51.58 2.58 5
824.29 61.78 57.02 4.72 5
824.31 62.54 57.52 4.96 3
824.57 76.97 66.72 10.21 5
823.50 24.45 24.45 0.00 Overtopping

BYPASS CULVERT

Table 2 - Culvert Summary Table: Double 36
Total
Discharge
(cfs)
Culvert
Discharge
(cfs)
Headwater
Elevation (ft)
Inlet Control
Depth (ft)
Outlet
Control
Depth (ft)
Flow
Type
Normal
Depth (ft)
Critical
Depth (ft)
Outlet Depth
(ft)
Tailwater
Depth (ft)
Outlet
Velocity
(ft/s)
Tailwater
Velocity
(ft/s)

1.00 1.00 823.30 0.292 1.760 1-S1f 0.197 0.214 3.000 3.200 0.071 0.000

8.60 8.60 823.33 0.882 1.785 1-S1f 0.563 0.644 3.000 3.200 0.608 0.000

16.19 16.19 823.39 1.230 1.848 1-S1f 0.774 0.892 3.000 3.200 1.145 0.000

23.79 23.79 823.49 1.512 1.949 1-S1f 0.944 1.090 3.000 3.200 1.683 0.000

31.39 31.37 823.63 1.802 2.085 1-S1f 1.093 1.261 3.000 3.200 2.219 0.000

38.98 38.69 823.79 2.052 2.248 1-S1f 1.225 1.411 3.000 3.200 2.737 0.000

46.58 45.60 823.96 2.270 2.424 1-S1f 1.344 1.536 3.000 3.200 3.225 0.000

54.18 51.58 824.13 2.448 2.592 1-S1f 1.443 1.635 3.000 3.200 3.649 0.000

61.78 57.02 824.29 2.607 2.751 1-S1f 1.532 1.724 3.000 3.200 4.034 0.000

62.54 57.52 824.31 2.621 2.765 1-S1f 1.540 1.732 3.000 3.200 4.068 0.000

76.97 66.72 824.57 2.889 3.032 1-S1f 1.688 1.872 3.000 3.200 4.719 0.000

BYPASS CULVERT

******************************************************************************** Straight Culvert
Inlet Elevation (invert): 821.54 ft, Outlet Elevation (invert): 820.10 ft Culvert Length: 271.67 ft, Culvert Slope: 0.0053
******************************************************************************** Site Data - Double 36
Site Data Option: Culvert Invert Data
Inlet Station: 0.00 ft
Inlet Elevation: 821.54 ft
Outlet Station: 271.67 ft
Outlet Elevation: 820.10 ft
Number of Barrels: 2
Culvert Data Summary - Double 36
Barrel Shape: Circular
Barrel Diameter: 3.00 ft
Barrel Material: Smooth HDPE
Embedment: 0.00 in
Barrel Manning's n: 0.0120
Culvert Type: Straight
Inlet Configuration: Square Edge with Headwall
Inlet Depression: None

BYPASS CULVERT

Table 3 - Downstream Channel Rating Curve (Crossing: Ardmore Double Culvert) Flow (cfs) Water Surface Elev (ft) Depth (ft)

1.00 823.30 3.20

8.60 823.30 3.20

16.19 823.30 3.20

23.79 823.30 3.20

31.39 823.30 3.20

38.98 823.30 3.20

46.58 823.30 3.20

54.18 823.30 3.20

61.78 823.30 3.20

62.54 823.30 3.20

76.97 823.30 3.20

BYPASS CULVERT

Tailwater Channel Data - Ardmore Double Culvert
Tailwater Channel Option: Enter Constant Tailwater Elevation Constant Tailwater Elevation: 823.30 ft
Roadway Data for Crossing: Ardmore Double Culvert
Roadway Profile Shape: Irregular Roadway Shape (coordinates) Roadway Surface: Gravel
Roadway Top Width: 2.00 ft

BYPASS CULVERT

SAFE OVERLAND ESCAPE PATH ANALYSIS

FOR BYPASS CULVERT

OFFSITE RUN-ON

FLOW PATH

OFFSITE RUN-ONOVERLAND ESCAPECROSS-SECTION

100-Year Storm -- Cross Section for Offsite Run-on OVE (crest) Project Description
Manning
Formula Friction Method
Solve For Normal Depth
Input Data
Channel Slope %1.00
Normal Depth ft1.96
Discharge cfs76.97
27 Siemon Company Drive Suite 200 W Page 1 of 1
Watertown, CT 06795 USA +1-203-755-1666
2/16/2023
FlowMaster
[10.03.00.03]
Bentley Systems, Inc. Haestad Methods Solution
2023-02-16_Ardmore_Misc SD.fm8 Center

100-Year Storm -- Offsite Run-on OVE (crest)
Project Description
Manning
Formula Friction Method
Solve For Normal Depth
Input Data
Channel Slope %1.00
Discharge cfs76.97
Section Definitions
Elevation
(ft)
Station
(ft)
0+00 827.64
0+01 828.06
0+02 828.00
0+05 827.00
0+08 826.00
0+10 825.00
0+13 824.00
0+15 823.50
0+16 824.00
0+22 825.00
0+43 826.00
Roughness Segment Definitions
Start Station Ending Station Roughness Coefficient
(0+00, 827.64) (0+02, 828.00) 0.013
(0+02, 828.00) (0+43, 826.00) 0.025
Options
Pavlovskii's
Method
Current Roughness Weighted
Method
Pavlovskii's
Method
Open Channel Weighting
Method
Pavlovskii's
Method
Closed Channel Weighting
Method
Results
Normal Depth ft1.96
Roughness Coefficient 0.025
Elevation ft825.46
823.50 to
828.06 ft Elevation Range
Flow Area ft²16.3
Wetted Perimeter ft22.86
Hydraulic Radius ft0.71
Top Width ft22.34
Normal Depth ft1.96
27 Siemon Company Drive Suite 200 W Page 1 of 2
Watertown, CT 06795 USA +1-203-755-1666
2/16/2023
FlowMaster
[10.03.00.03]
Bentley Systems, Inc. Haestad Methods Solution
2023-02-16_Ardmore_Misc SD.fm8 Center

100-Year Storm -- Offsite Run-on OVE (crest)
Results
Critical Depth ft1.95
Critical Slope %1.05
Velocity ft/s4.73
Velocity Head ft0.35
Specific Energy ft2.31
Froude Number 0.979
Flow Type Subcritical
GVF Input Data
Downstream Depth ft0.00
Length ft0.00
Number Of Steps 0
GVF Output Data
Upstream Depth ft0.00
Profile Description N/A
Profile Headloss ft0.00
Downstream Velocity ft/sInfinity
Upstream Velocity ft/sInfinity
Normal Depth ft1.96
Critical Depth ft1.95
Channel Slope %1.00
Critical Slope %1.05
27 Siemon Company Drive Suite 200 W Page 2 of 2
Watertown, CT 06795 USA +1-203-755-1666
2/16/2023
FlowMaster
[10.03.00.03]
Bentley Systems, Inc. Haestad Methods Solution
2023-02-16_Ardmore_Misc SD.fm8 Center

APPENDIX D
Appendix D – Preliminary Storm Drain Facility Concepts
• ADS StormTech MC-3500 Chamber overview
• Roadside Bioretention concept

® ARDMORE - L.I.D. CONCEPT

TYPICAL ROADSIDE BIOSWALES WITH GRAVEL TRENCH
0751-0005

NOT TO SCALE
DATE: 11/08/2022
SIDEWALK PARKWAY 0.50' 2.00' 2.00'

0.50'

5.00'
30 MIL PVC LINER
(BOTH SIDES)
CALTRANS CLASS 3

PERMEABLE MATERIAL

DO NOT USE FILTER FABRIC

BETWEEN BSM AND

AGGREGATE LAYERS

BIORETENTION SOIL

MEDIA (BSM)
LEGEND:

DESIGN FINISHED GRADE
MAX. PONDING ELEVATION

CITY OF
P.R. C&G

ROADSIDE BIOSWALE WITH UNDERGROUND GRAVEL TRENCH
FOR PLAN REVIEW ONLY.

NOT FOR CONSTRUCTION
4" CURB

SPACED GRAVEL

CHECK DAMS ROCK SPLASH PAD

AT CURB OPENINGS
(BOTH SIDES) 0.25' 3
4 " (NO. 4) OPEN

GRADED AGGREGATE
PAGE 1 OF 1

0.50'





 




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(805) 316-0101
895 Napa Avenue, Suite A-6, Morro Bay, CA 93442

MEMORANDUM
Date: December 7, 2022
To: David Athey and Darren Nash, City of Paso Robles
From: Michelle Matson and Joe Fernandez, CCTC
Subject: Ardmore Industrial, Paso Robles –Transportation Analysis This memorandum summarizes the transportation impact analysis for the proposed Ardmore Industrial development at 2930 Union Road in the City of Paso Robles. The proposed project would construct 250,082 square feet of potential warehouse, office, winemaking, storage, and retail uses. The project site plan is included as Figure 1.

TRANSPORTATION ANALYSIS SUMMARY
The proposed project would generate approximately 1,194 net new vehicle trips per weekday, including 117 AM peak hour trips and 158 PM peak hour trips. The project would not significantly impact intersection operations and would have a less than significant impact on vehicle miles traveled (VMT).

The Golden Hill Road/Union Road roundabout project could consider restriping the left turn lane just south of Ardmore Road to a two-way left turn lane. We also recommend the following:
• Install all-way stop control at the Ardmore Road/Ardmore Road Extension t-intersection. • Consider consolidating the two central driveways on the existing Ardmore Road and placing the new driveway opposite the existing driveway location on the west side. Alternatively, remove the second northernmost driveway which has potential left turn conflicts with the existing driveway location on the west side.
• The Building 1 western driveway does not meet City standards. Relocate the proposed truck access for Building 1 so it is at least 200 feet away from the Ardmore Road/Ardmore Extension intersection.

Alternatively, this driveway could be one-way inbound forcing trucks to circulate through the parking lot and exit at the easternmost driveway.
• Add ADA parking spaces on the Ardmore Road extension and consider replacing parking tees with edge line striping.
• Install edge line striping on Ardmore Road along the project frontage. • Install no parking within the Ardmore Road intersection and 25 feet from each curb return and install no parking 6 feet from the curb return on either side of driveways.

Regional improvements are included in the City’s Development Impact Fees.





  

December 2022 Source

Ardmore Industrial, Paso Robles – Transportation Analysis 3 Central Coast Transportation Consulting December 7, 2022

CEQA ANALYSIS
Vehicle miles traveled (VMT) were analyzed consistent with recently mandated changes to the California Environmental Quality Act (CEQA) and state Office of Planning and Research (OPR) guidance. The City’s 2022 Transportation Impact Analysis (TIA) Guidelines Supplement provide VMT and safety thresholds consistent with OPR guidance. Office and industrial projects may have a significant impact if the work VMT per employee exceeds 85 percent of the regional average. Work VMT captures home-based-work attractions (trips from homes to workplaces). In addition, projects may have a significant impact if they exacerbate an existing high-priority or similar safety location, introduces a design feature that substantially increases hazards, or propose features that do not meet City design standards. Caltrans relies on VMT and safety to evaluate transportation impacts and published a VMT Focused TIS Guide in May 2020, which replaced the prior guide reliant on LOS. The TIS Guide notes that lead agencies have the discretion to choose VMT thresholds and methods, and generally conforms to OPR guidance.

The SLOCOG Travel Demand Model was applied to estimate VMT. Project employees were estimated using typical square footage per employee from industry standard sources, then were added to the model. Table 1 summarizes the VMT results.

Table 1: Regional VMT Analysis
The addition of the project would reduce regional work VMT due to the provision of jobs in a housing-rich area. Therefore, the project would have a less-than-significant impact to VMT.

Scenario
Regional
Employees
Regional
Work VMT
2020 No Project 117,332 1,595,867
2020 With Project 117,537 1,593,552
Change from No Project 205 -2,315
Source: SLOCOG TDM, CCTC, 2022
Regional VMT Analysis

1. Work VMT is attracted to workplaces (sum of home-basedwork attractions).

Ardmore Industrial, Paso Robles – Transportation Analysis 4 Central Coast Transportation Consulting December 7, 2022

PROJECT TRIP GENERATION
The Institute of Transportation Engineers’ (ITE) Trip Generation Manual 11th Edition was used to estimate project trip generation. Table 2 summarizes the project trip generation.

Table 2: Project Trip Generation
The proposed project would generate 1,194 net new vehicle trips per weekday, including 117 AM peak hour trips and 158 PM peak hour trips.

TRANSPORTATION ANALYSIS
The following section summarizes the existing conditions, existing Ardmore Road trip generation, intersection operations, and site access and circulation.

Existing Conditions
Ardmore Road is a two-lane minor road with a 30 miles per hour (MPH) posted speed limit and intermittent sidewalks on either side of the roadway. Streetside parking is allowed intermittently along either side of the roadway.

Traffic collision data was obtained from the Statewide Integrated Traffic Records System (SWITRS). Between 2017 and 2021, no collisions occurred on Ardmore Road. One property damage only collision occurred just south of the Golden Hill Road/Ardmore Road intersection when a northbound driver sideswiped another vehicle and ran off the road due to unsafe speed. No other collisions occurred at the Golden Hill Road/Ardmore Road intersection. There are no collision patterns and no recommendations.

Currently, the Golden Hill Road/Union Road intersection is closed for the construction of a single lane roundabout through 2023. Traffic counts at the Golden Hill Road/Union Road intersection were collected in June and July of 2021 and are attached. No traffic counts are available on Ardmore Drive and new data was not collected due to the current detour on Ardmore Road.

Existing Ardmore Road Trip Generation
There is approximately 100,000 square feet of industrial uses and seven single family homes currently on Ardmore Road. The Institute of Transportation Engineers’ (ITE) Trip Generation Manual 11th Edition was also Daily
Total In Out Total In Out Total
Warehouse¹ 166.083 KSF 301 34 10 44 13 33 46
Manufacturing² 76.607 KSF 491 42 14 56 15 34 49
Retail³ 7.392 KSF 402 10 7 17 31 32 63
1,194 86 31 117 59 99 158

2. ITE Land Use Code #140, Manufacturing. Fitted curve equations used.

3. ITE Land Use Code #822, Strip Retail Plaza. Average rates used for Daily and AM. Fitted curve equation used for PM.

Size Unit
Total Project Trips
KSF = Thousand Square Feet; ITE = Institute of Transportation Engineers.

1. ITE Land Use Code #150, Warehouse. Fitted curve equations used.

AM Peak Hour PM Peak Hour
Ardmore Industrial Trip Generation
Land Use

Ardmore Industrial, Paso Robles – Transportation Analysis 5 Central Coast Transportation Consulting December 7, 2022 used to estimate the existing trip generation on Ardmore Road. Table 3 summarizes the trip generation estimate for the existing uses on Ardmore Road.

Table 3: Existing Ardmore Road Trip Generation
The existing uses would generate 513 net new vehicle trips per weekday, including 79 AM peak hour trips and 48 PM peak hour trips. Following completion of the Golden Hill Road/Union Road roundabout, Ardmore Road will not be the fastest route and cut through traffic is not anticipated.

Intersection Operations
The 2021 traffic counts at Golden Hill/Union Road were used to develop through volumes on Golden Hill Road north of Ardmore Road and the existing Ardmore Road trip generation was used to estimate the turning movement volumes at Ardmore Road without the detour. Project trips were then added to develop Existing Plus Project Conditions. The Existing Plus Project volumes are shown on Figure 2 and the intersection operations are shown on Table 4. Detailed calculation sheets are attached.

Table 4: Existing Plus Project Intersection Operations
Both the Golden Hill Road/Union Road (#1) and Golden Hill/Ardmore Road (#2) intersections would operate at LOS C or better with the addition of project traffic and the completion of the Golden Hill Road/Union Road (#1) roundabout. No queues exceed the available storage.

In Out Total In Out Total
General Light Industrial 100.000 KSF 426 63 9 72 5 35 40 Single Family Home 7.000 DU 87 2 5 7 5 3 8
513 65 14 79 10 38 48

1. ITE Land Use Code #110, General Light Industrial. Fitted curve equations used.

2. ITE Land Use Code #210, Single Family Detached Housing. Fitted curve equations used.

Land Use Size Unit
Daily
Total
Existing Ardmore Road Trip Generation
AM Peak Hour PM Peak Hour
Total Gross Vehicle Trips
KSF = Thousand Square Feet; ITE = Institute of Transportation Engineers, DU = Dwelling Unit Intersection Weekday
Peak Hour Delay1 LOS
AM 10.0 A
PM 10.9 B
AM 1.6 (18.6) - (C)
PM 2.7 (23.4) - (C)
Existing Plus Project Intersection Operations

1. HCM 6th average control delay in seconds per vehicle. For two-way stop controlled (TWSC) intersections the worst approach's delay is reported in parentheses next to the overall delay.

1. Golden Hill Rd/Union Rd

2. Golden Hill Rd/Ardmore Rd Page 852 of 1344 City Council Agenda April 21, 2026 
 


 

  

 

 
   






  

 





 

 








   

  

 



 

 







December 2022 December 2022

Ardmore Industrial, Paso Robles – Transportation Analysis 7 Central Coast Transportation Consulting December 7, 2022 Exhibit 1 below shows the proposed intersection striping at Golden Hill Road/Ardmore Road (#2) following completion of the roundabout.

Exhibit 1: Golden Hill Road/Ardmore Road Intersection Striping The Ardmore Road stop bar is located east of the existing curb ramp to allow for pedestrian travel. Therefore, drivers on Ardmore Road need to stop at the stop bar and then creep toward Golden Hill Road prior to making a turning movement. The intersection analysis did not include two-stage gap acceptance; however, the Golden Hill Road/Union Road roundabout project could consider restriping the left turn lane just south of Ardmore Road to a two-way left turn lane to allow for two-stage gap acceptance, which would improve operations.

Site Access and On-Site Circulation
The current site is vacant. The project proposes four driveways on Ardmore Road. The project proposes a main driveway extending Ardmore Road to the east, creating a t-intersection. The project also proposes three additional driveways along Ardmore Road north of the extension, a minimum of 200 feet apart. However, there is an existing intersection on the west side of the road approximately 300 feet north of Ardmore Road.

We recommend the project install all-way stop control at the Ardmore Road/Ardmore Road Extension tintersection to control left turn conflicts. We also recommend consolidating the two central driveways on the existing Ardmore Road and placing the new driveway opposite the existing driveway location on the west side.

Alternatively, remove the second northernmost driveway which has potential left turn conflicts with the existing driveway location on the west side.

The primary truck access point for Building 1 is proposed on the Ardmore Road extension just east of the existing Ardmore Road. The driveway does not meet City Standard Drawing C-10 and the truck turning movements as shown on the site plan are not recommended in this location. 200-foot minimum driveway spacing is recommended. We recommend the project relocate the proposed truck access or convert to one-way inbound.

Ardmore Industrial, Paso Robles – Transportation Analysis 8 Central Coast Transportation Consulting December 7, 2022 Americans with Disabilities Act (ADA) parking spaces are recommended on the Ardmore Road extension.

Edge line striping could also be considered as an alternative to the parking tees.

Street features including landscaping, utility poles, street furniture, signs, and parked vehicles can inhibit sight distance in urban areas. Per California Manual on Uniform Traffic Control Devices (CAMUTCD) guidance, “At all intersections, one stall length on each side measured from the crosswalk or end of curb return should have parking prohibited. A clearance of 6 feet measured from the curb return should be provided at alleys and driveways.” We recommend parking restriction consistent with the CAMUTCD.

ATTACHMENTS
Traffic Count
Synchro Worksheets

REFERENCES
California Department of Transportation. May 2020. Vehicle Miles Traveled-Focused Transportation Impact Study Guide.
_____. 2012, 2018. Highway Design Manual.
_____. 2014, Revision 6. California Manual on Uniform Traffic Control Devices.

City of El Paso De Robles. 2017. Bicycle & Pedestrian Master Plan. _____. 2018. General Plan Circulation Element.
_____. 2013. Transportation Impact Analysis Guidelines. _____. 2022. Transportation Impact Analysis Guidelines Supplement.

Institute of Transportation Engineers (ITE). 2021. Trip Generation Manual, 11th Edition. _____. 2017. Trip Generation Handbook, 3rd Edition. ‘
The Natelson Company, Inc. 2001. Employment Density Study Summary Report.

Transportation Research Board. 2017. Highway Capacity Manual, 6th Edition.

4 5 d B A c o u s t i c s , L L C
w w w . 4 5 d B . c o m
( 8 0 5 ) 2 5 0 - 1 5 6 6
P O B o x 1 7 1 7
B u e l l t o n , C A 9 3 4 2 7
This report (including any enclosures and attachments) has been prepared for the exclusive use and benefit of the addressee(s) and solely for the purpose for which it is provided. No part of this report shall be reproduced, distributed, or communicated to any third party without written permission. We do not accept any liability if this report is used for an alternative purpose from which it is intended, nor to any third party.

March 8, 2023
45dB Project # 23002
Acoustical Analysis:

Commercial/Light Industry
Development
2930 Union Rd.

Paso Robles, CA 93446
Requested by:

Kirk Consulting
Attn: Ian McCarville
8830 Morro Rd.

Atascadero, CA 93422
Client/Owner:

Covelop
1135 Santa Rosa St., Ste #210
San Luis Obispo, CA 93401
Summary
45dB Acoustics (“45dB”) has reviewed the applicable noise-related regulations for the commercial and light industrial 6-building planned development at the above address in the City of Paso Robles. Residences exist to the immediate north and east of the project, and a residential development is planned for the vacant site located directly south of the project. Properties to the west are industrial/commercial land uses. All neighboring properties exist within the City of Paso Robles.

Existing daytime hourly noise levels due to road traffic noise, primarily from Highway 46, range up to 43 dBA at the north property line adjacent to an existing residence, as predicted from published traffic counts and the FHWA’s Traffic Noise Model implemented into SoundPLAN®, a 3D noise propagation software package.

The proposed project was modeled to analyze the potential noise impact on the neighboring land uses. Noise levels associated with the project are anticipated to comprise of the following: traffic noise associated with the increased traffic on Ardmore Road; traffic and parking activities of 994 passenger vehicles daily in the surrounding parking lots; truck traffic and loading of up to 80 semi-trucks daily at the loading docks on the west side of Building 1; truck traffic and loading of up to 60 medium delivery trucks daily at the loading dock and in the service/loading lane along the north side of Building 6; truck traffic and loading of up to 60 medium delivery trucks daily in the service/loading lane along the south side of Building 3; a total of 37 rooftop HVAC units on the six Project buildings, each modeled with a sound power level of 87 dBA rel 10-12 W (i.e., sound pressure level of 76 dBA rel 20µPa at 1-m). All site activities were assumed to occur during daytime hours between 7am and 7pm. No vehicle idling was included in the service/loading lanes near Buildings 3 and 6 or near the loading docks at Building 1.

Refrigerated trucks are not expected at the Project site and were not included as a noise source in the model.

45dB Acoustics, LLC 2930 Union Rd.
page ii noise management : room acoustics : environmental impact www.45dB.com With the project in place and the above assumptions about site traffic and rooftop HVAC equipment, the modeled Daytime Hourly LAeq levels along the property lines adjacent to residential land uses ranged up to 55 dBA and Nighttime Hourly LAeq levels ranged up to 45 dBA, both of which comply with the Municipal Code Daytime limit of 55 dBA and Nighttime limit of 45 dBA for residential land uses.
for 45dB Acoustics, LLC:

Sarah Taubitz, Mem.INCE, ASA

45dB Acoustics, LLC 2930 Union Rd.
page iii noise management : room acoustics : environmental impact www.45dB.com Contents
Summary .......................................................................................................................................................................i 1 Introduction........................................................................................................................................................1 2 Regulatory Setting..............................................................................................................................................2

2.1 Local Regulation – City of Paso Robles Noise Ordinance..............................................................................2

2.1.1 Residential Exterior Ambient Noise Levels...........................................................................................2

2.1.2 Commercial/Industrial Exterior Ambient Noise Levels.........................................................................2 3 Noise Propagation Model ..................................................................................................................................4

3.1 Local Transportation Noise.............................................................................................................................4

3.2 Warehouse Shipping Activity...........................................................................................................................5

3.3 Service and Loading Lanes .............................................................................................................................5

3.4 Parking Areas..................................................................................................................................................6

3.5 HVAC Equipment ............................................................................................................................................6 4 Existing Site Ambient Noise Environment.......................................................................................................7 5 Predicted Future Noise Environment with Project.........................................................................................8

5.1 Assumptions and Limitations...........................................................................................................................9

5.1.1 Loading Areas........................................................................................................................................9

5.1.2 Parking Lots...........................................................................................................................................9

5.1.3 Rooftop HVAC Equipment .................................................................................................................10 6 Conclusion ........................................................................................................................................................11 7 Figures...............................................................................................................................................................12 8 Appendix...........................................................................................................................................................17

8.1 Characteristics of Sound ...............................................................................................................................17

8.2 Terminology/Glossary ...................................................................................................................................18

8.3 SoundPLAN Acoustics Software....................................................................................................................20

8.3.1 ISO 9613-2...........................................................................................................................................20

8.3.2 Traffic Noise Model.............................................................................................................................20

45dB Acoustics, LLC 2930 Union Rd.
page iv noise management : room acoustics : environmental impact www.45dB.com Figures
FIGURE 1: AERIAL MAP OF PROPOSED PROJECT SITE AND SURROUNDING PROPERTIES (GOOGLEMAPS) ...........................................12 FIGURE 2: PROJECT SITE PLAN (DATED 2-13-2023)...............................................................................................................13 FIGURE 3: DAYTIME (“LEQ,D”) SOUND LEVEL CONTOURS, EXISTING SITE ......................................................................................14 FIGURE 4: 3D VIEW OF SITE GEOMETRY, WITH PROPOSED PROJECT...........................................................................................15 FIGURE 5: DAYTIME (“LEQ,D”) SOUND LEVEL CONTOURS, WITH PROPOSED PROJECT ......................................................................16 Tables
TABLE 1: CITY OF PASO ROBLES NOISE ORDINANCE STANDARDS FOR NON-TRANSPORTATION NOISE SOURCES (REPRINT)......................3 TABLE 2: TRAFFIC COUNT DATA, 2023 ESTIMATES, AND PROJECTIONS DUE TO PROJECT..................................................................4 TABLE 3: SOUND LEVELS AT RECEIVERS OF INTEREST..................................................................................................................8 TABLE 4: SOUND LEVEL CHANGE RELATIVE LOUDNESS/ACOUSTIC ENERGY LOSS...........................................................................17

45dB Acoustics, LLC 2930 Union Rd.
page 1 noise management : room acoustics : environmental impact www.45dB.com 1 Introduction
This sound level assessment and analysis was carried out to determine the noise impacts associated with the proposed mixed-use development at 2930 Union Rd in Paso Robles, CA. 45dB Acoustics, LLC (“45dB”) has predicted sound levels across the site and evaluated the project’s suitability in reference to local regulations. Neighboring properties—particularly the existing residence to the immediate north and future residential developments to the immediate south—have been considered. The following factors are also considered:
• The topographical relationship of potential noise sources and applicable noise ordinances/laws
• Identification of noise sources and their characteristics, including predicted noise levels at representative neighboring receiver location(s), considering present and future land usage • Basis for the sound level prediction (i.e., engineering inputs and assumptions) • Noise attenuation measures (mitigation) to be applied, if needed • Information on fundamentals of noise and vibration to aid in interpreting the report (Section 8, Appendix)
The project would consist of six new commercial/light industrial buildings located in the City of Paso Robles. Anticipated uses included warehousing / storage, wine processing and tasting, light /craft manufacturing, office, and limited retail. Residences and farmland are located immediately north and east of the project’s property lines (Figure 1). A residential development is planned to the immediate south. Commercial and industrial properties are located to the west of the project.

The project is planned to include 330 vehicle parking spaces and 17 motorcycle parking spaces.

A Transportation Impact Study was completed and is referenced herein for the increased traffic due to the project.

For the purposes of an acoustic study, with trucks in the loading areas as the dominant noise sources on site, the operating hours of 7am to 7pm (i.e. daytime hours) on weekdays were utilized for a conservative analysis. Most days and times of the year may have less traffic, and hence noise, emitting from the proposed project.

45dB Acoustics, LLC 2930 Union Rd.
page 2 noise management : room acoustics : environmental impact www.45dB.com 2 Regulatory Setting
Throughout this document, noise levels and limits are assumed to be A-weighted decibel levels.

2.1 Local Regulation – City of Paso Robles Noise Ordinance The project and all surrounding properties are located within Paso Robles. The City of Paso de Robles, CA Municipal Code Noise Ordinance1provides regulation and guidelines regarding noise. The Interior and Exterior Noise Standards (Table 1) define the limits due to locally regulated (non-transportation) noise sources at residential, industrial, and commercial receiving land uses.

2.1.1 Residential Exterior Ambient Noise Levels
The nearest potentially sensitive noise receptors evaluated in this study are the residential homes/dwellings—including those on agriculturally zoned land—at the locations indicated on Figure 1.

For residential uses, the limits are 55 dBA LAeq and 75 LAmax during daytime hours, 50 dBA LAeq and 70 LAmax during evening hours, and 45 dBA LAeq and 65 dBA LAmax during nighttime hours. Daytime hours are defined as 7am to 7pm, evening hours are 7pm to 10pm, and nighttime hours are 10pm – 7am. These limits are to be evaluated at the receiving land use property line.

2.1.2 Commercial/Industrial Exterior Ambient Noise Levels The nearest commercial/industrial properties are located directly west of the project, across Ardmore Rd. These land uses are highlighted in Figure 1.

For commercial and industrial land uses, The City of Paso Robles’ exterior noise standards for locally regulated noise sources are 60 dBA LAeq and 80 LAmax during daytime hours, and 55 dBA LAeq and 75 LAmax during evening hours (Table 1). Daytime hours are defined as 7am to 7pm and evening hours are 7pm to 10pm. Nighttime limits are not defined for these land uses because commercial and industrial properties are assumed to be unoccupied at night. 1 El Paso de Robles, California Municipal Code, Section 21.60.060, Interior and Exterior Noise Standards, 2019. https://library.municode.com/ca/el_paso_de_robles/codes/code_of_ordinances?nodeId=TIT21ZO_ARTVNO_CH21 .60NO_21.60.060EXINNOST

45dB Acoustics, LLC 2930 Union Rd.
page 3 noise management : room acoustics : environmental impact www.45dB.com Table 1: City of Paso Robles Noise Ordinance Standards for Non-Transportation Noise Sources (reprint)

45dB Acoustics, LLC 2930 Union Rd.
page 4 noise management : room acoustics : environmental impact www.45dB.com 3 Noise Propagation Model
SoundPLAN® is a state-of-the-art sound propagation modeling software package that calculates sound levels while taking into account the air and ground attenuation factors, terrain variation and the built environment, road pavement types, and other relevant factors. This software has incorporated many noise propagation standards, including the ISO 9613-2 and the FHWA’s Traffic Noise Model (TNM) calculation standards. More details about SoundPLAN®, TNM, and ISO 9613-2 can be found in Section 8.3.

Traffic counts for nearby roads are input to the model to establish an ambient existing noise environment. All sound pressure levels in this report are in units of A-weighted decibels (dBA) for direct comparison to the Code.

3.1 Local Transportation Noise
AADT (Annual Average Daily Traffic) counts are taken from the CalTrans traffic database2and the County of San Luis Obispo Traffic Engineering online database3and input directly into SoundPLAN®, which then distributes them across the day, evening, and nighttime periods to predict outdoor noise levels. Traffic counts are adjusted upward 1% per year to 2023.

Current traffic counts for Ardmore, Golden Hill, and Union Roads and their projected increases due to the Project were detailed in the transportation impact analysis4provided by the Client. The study provided peak AM and PM hourly counts which were used to estimate the current and projected AADT numbers used in the model. Of particular note, the average daily traffic on Ardmore is anticipated to increase by 1194, which includes passenger vehicles as well as the semi-trucks and medium delivery trucks that are anticipated to arrive daily at the Project site. 226 daily passenger and semi-truck trips are expected for Building 1 and 968 daily passenger and medium delivery truck trips are expected for Buildings 2-6.

Table 2: Traffic Count Data, 2023 Estimates, and Projections due to Project Road AADT Year
Years to
Project
2023 AADT
Projections
Projected AADT
Increase due to Project
Hwy 462 26500 2020 3 27303 --
Union Rd (E of Paso Robles)3 2985 2002 21 3679 --
Union Rd (Golden Hill to Paso
Robles)4
-- -- -- 8029 --
Union Rd (W of Golden Hill)4 -- -- -- 5389 215
2 CalTrans Traffic Census Program, 2020. https://dot.ca.gov/programs/traffic-operations/census 3 County of San Luis Obispo, Department of Public Works, Traffic Count Data, 2021. https://www.slocounty.ca.gov/Departments/Public-Works/Forms-Documents/Transportation/Traffic-Count-Data.pdf 4 Ardmore Industrial, Paso Robles –Transportation Analysis, Central Coast Transportation Consulting, December 2022.

45dB Acoustics, LLC 2930 Union Rd.
page 5 noise management : room acoustics : environmental impact www.45dB.com Road AADT Year
Years to
Project
2023 AADT
Projections
Projected AADT
Increase due to Project
Golden Hill (N of Union)4 -- -- -- 5785 358
Golden Hill (S of Union)4 -- -- -- 7445 539
Golden Hill (S of Ardmore)4 -- -- -- 7242 603
Ardmore (E of Golden Hill)4 -- -- -- 513 1194
All traffic was assumed to travel at a speed of 15 mph. All passenger, semi-truck, and delivery truck traffic was modeled for the hours between 7am and 7pm.

3.2 Warehouse Shipping Activity
The loading dock area on the west side of Building 1 (Figure 2) is expected to handle 80 semitrucks daily. These are input into the model with the following details:
• 80 heavy trucks per day, traveling at 10 mph between the hours of 7am and 7pm through the loading area and around Building 1
• Backup alarms for each semi-truck with an average sound power level (LWA) of 100 dBA and maximum sound power level (LWAmax) of 103 dBA, emitted for no longer than 15 seconds per vehicle in the loading area
• Air brakes for each semi-truck having a maximum sound power level (LWAmax) of 110 dBA, which would be emitted for no more than 2 seconds per vehicle in the loading area • We assumed that all vehicles would not idle for any significant amount of time • We assumed that no refrigerated trucks would be expected at this site. (Refrigerated semi-trailer trucks can be problematic for noise, as the refrigerator units for the containers tend to be high level, low-frequency tonal, may operate even when the truck is parked, and are located at a higher height toward the top of the truck containers.)

3.3 Service and Loading Lanes
Two service/loading areas are included on the project site, on the south side of Building 3 and on the north side of Building 6. These are input into the model with the following details:
• Each service lane would have no more than 60 cars and medium-sized delivery trucks, traveling at speeds of 10 mph or less between the hours of 7am and 7pm • A loading area on the northeast corner of Building 6, which includes a loading dock where delivery trucks may have a backup alarm. The backup alarms have an average sound power level (LAeq) of 100 dBA and maximum sound power level (LWAmax) of 103 dBA, which would be emitted for no longer than 10 seconds per vehicle at the loading dock
• We assumed that no medium truck or delivery vehicles would use air brakes • We assumed that all vehicles would not idle for any significant amount of time

45dB Acoustics, LLC 2930 Union Rd.
page 6 noise management : room acoustics : environmental impact www.45dB.com For reference, a medium-duty truck typically has noise emission levels 5-7 dB lower than heavyduty semi-trucks.

3.4 Parking Areas
Parking areas surround the six Project site buildings. Modeled parking lot noise includes door slams and vehicle ignitions – and conservatively assumes all vehicles have internal-combustion engines. Per the Client, 186 daily vehicle trips are expected for Building 1 and 968 daily vehicle trips are expected for Buildings 2-6. With expected semi- and delivery truck traffic excluded, we modeled the parking area around Building 1 with parking activities for 146 passenger vehicles and the parking areas around Buildings 2-6 with activities for 848 passenger vehicles. All parking activities were assumed to only occur during daytime hours, between 7am and 7pm.

3.5 HVAC Equipment
Placement of the 37 rooftop HVAC units was provided by the architect on March 2, 2023. Nine (9) rooftop units (RTUs) were included for Building 1, two (2) RTUs on Building 2, six (6) RTUs on Building 3, six (6) RTUs on Building 4, eight (8) RTUs on Building 5, and 6 (6) RTUs on Building 6.

Although the models have not yet been selected, based upon our experience with this equipment and calculated sound levels that would comply with the Municipal Code at the property lines, we assumed each unit has a sound power level (“LWA”) of no more than 87 dBA rel 10-12 W, corresponding to a sound pressure level of 76 dBA rel 20µPa at a distance of 1 meter.

All HVAC equipment was assumed to be operating continuously, 24 hours per day, since although not typical, the project has the potential for all units to be running simultaneously.

45dB Acoustics, LLC 2930 Union Rd.
page 7 noise management : room acoustics : environmental impact www.45dB.com 4 Existing Site Ambient Noise Environment
A 3D geometric model of the situation is created within the SoundPLAN® noise modeling software. Buildings and main roads are modeled on the terrain to create a realistic model of the outdoor noise propagation for the area.

All sound contour plots, in plan view, are presented at a height of 1.5 m / 5 feet (AGL) within this report, and all are in units of A-weighted dB rel 20µPa for direct comparison with the applicable regulations.

The Federal Highway Administration’s Traffic Noise Model (TNM) calculation method is utilized to predict outdoor noise propagation from the existing road traffic. Resulting daytime (“Leq,d”) sound level contours for the existing site are shown in Figure 3. Because these sound levels are calculated based only on road traffic, they are very low levels, particularly during evening and nighttime hours when traffic counts are lower. In reality, other sounds such as wind through vegetation, and other community sounds may contribute to and create levels higher than those shown here. In general, the areas further away from the roads are relatively quiet rural environments. For the residential use areas north of the project site on Ardmore Rd, daytime noise levels are approximately 42 dBA.

45dB Acoustics, LLC 2930 Union Rd.
page 8 noise management : room acoustics : environmental impact www.45dB.com 5 Predicted Future Noise Environment with Project
The 3D model with the project in place is shown in Figure 4. The resulting daytime sound level contours (at a 5-ft height) from the proposed Project and associated traffic, loading dock, and HVAC noise in place (as described in Section 3) are illustrated in Figure 5. The red asterisks (*) on each of the buildings represent the rooftop HVAC unit locations.

The daytime hourly levels at the residential property lines to the north, east, and south of the project site are not expected to exceed the Municipal Code residential Leq limit of 55 dBA.

Maximum daytime levels are also not expected to exceed the associated Lmax limit of 75 dBA.

Levels at the western commercial/industrial property lines are also not expected to exceed the Municipal Code limits.

Table 3 shows the existing ambient levels due to road traffic alone at selected property line receiver locations (shown in Figure 3 and Figure 5) as well as the anticipated effect the proposed Project would have at each location.

Table 3: Sound Levels at Receivers of Interest
Existing Ambient (Road Traffic Only) With Project
Receiver
CNEL /Ldn
(dBA)
Daytime
Hourly
Leq,d (dBA)
Evening
Hourly
Leq,e (dBA)
Nighttime
Hourly
Leq,n (dBA)
CNEL /Ldn
(dBA)
Daytime
Hourly
Leq,d (dBA)
Evening
Hourly†
Leq,e (dBA)
Nighttime
Hourly
Leq,n (dBA)
Daytime
Lmax
(dBA)
E1 42 41 36 34 52 51 45 44 44
E2 37 36 31 28 53 52 46 45 30
E3 38 37 32 29 49 47 41 41 32
N1 43 42 37 35 51 53 40 39 66
N2 42 41 36 34 53 55 39 38 71
NE 43 42 37 35 49 48 41 41 58
NW 43 43 37 34 53 54 44 42 52
S1 35 34 29 27 51 53 36 36 65
S2 34 33 28 26 45 46 36 35 52
SE 32 31 25 23 44 42 36 36 34
SW 36 35 30 27 51 53 37 36 64
W1* 35 35 29 26 57 60 40 39 66
W2* 35 34 29 26 57 60 39 38 76
* Receivers W1 & W2 are located on a property line shared with industrial/commercial land uses

45dB Acoustics, LLC 2930 Union Rd.
page 9 noise management : room acoustics : environmental impact www.45dB.com All locations are expected to comply with the Municipal Code, assuming all site activities operate as described within this report and between 7am and 7pm. Although vehicle noise is not present at night, the HVAC units are often still running, which is responsible for a sizable increase during nighttime hours as shown. HVAC units typically run a fraction of any hour, so the increase shown is conservatively high and may be approximately 10dB lower on an hourly Leq basis. Rooftop units also can be screened to provide mitigation (not included here), and parapet walls may further redirect noise due to rooftop equipment.

5.1 Assumptions and Limitations
The sound level contours are provided for visualization purposes showing resulting sound levels during daytime hours. Daytime hourly sound levels are the primary metric used for evaluation since all Project site activities are expected to occur during daytime hours.

5.1.1 Loading Areas
The related maximum (“Lmax” or “LAmax”) limits within the regulations also apply while evaluating any proposed project. Maximum short-duration noises for this project include mainly the braking from semi-trucks and backup alarms from semi-trucks and medium delivery trucks in the loading areas outside Buildings 1 and 6. We anticipate that backup noises are within 20dB above the hourly LAeq levels from the trucking activities, such that if the hourly LAeq levels for the site comply, then the maximum levels for the site will also comply with the applicable regulations.

We assume trucks will not idle for long periods of time while parked. We recommend that any semi-trucks wishing to continuously idle do so near the north side of the Building 1 loading area, away from the property lines. If trucks run idle for the majority of a given hour, it can become a nuisance and potential code exceedance. The most effective mitigation is limiting/minimizing truck idling, which we presume is already the case. This is also true for backup beeping and truck air brakes usage.

Noise levels at the property lines are primarily limited by the number of semi-trucks and medium delivery trucks in the loading areas around Buildings 1 and 6. If more than 80 semi-trucks per day are expected in the loading area of Building 1, mitigation will be required at the south and west property lines due to the additional truck traffic noise in the loading area. Similarly, if more than 60 medium delivery trucks are anticipated to use the service/loading lane and dock north of Building 1, mitigation will be required.

5.1.2 Parking Lots
Parking areas surrounding the Project buildings were conservatively modeled with 994 passenger vehicles per day between the hours of 7am and 7pm. Further analysis would be required if parking activities were expected during evening or nighttime hours to ensure compliance with the Municipal Code.

45dB Acoustics, LLC 2930 Union Rd.
page 10 noise management : room acoustics : environmental impact www.45dB.com

5.1.3 Rooftop HVAC Equipment
Using the preliminary HVAC rooftop unit (RTU) layout provided by the architect, we included a maximum sound power level “LWA” of 87 dBA for each unit on the buildings as constant 24/7 noise sources in our model that would allow the Project to comply with the Municipal Code.

This HVAC noise can be considered “worst-case” for the project, and it contributes a significant portion of the total noise increase calculated.

Sound levels at the property lines can increase or decrease depending on the proximity of the RTUs. Nighttime levels along the east property line will not comply if the RTUs on Buildings 3 and 5 are placed closer than 100 feet from the east property line.

These units typically run less frequently at night and perhaps 25 to 50% of the daytime hours, so projected levels may be higher than typical during day and night hours. However, if the RTUs are louder than the sound power level “LWA” of 87 dBA, are located in significantly different locations than shown in the model, are placed closer to the property lines than indicated above, or if there will be more units on-site than included in this analysis, a revised analysis would be required to verify compliance. RTUs can also be screened/mitigated to reduce potential impact.

45dB Acoustics, LLC 2930 Union Rd.
page 11 noise management : room acoustics : environmental impact www.45dB.com 6 Conclusion
Existing daytime hourly noise levels due to road traffic noise, primarily from Highway 46, range up to 43 dBA at the north property line adjacent to an existing residence, as predicted from published traffic counts and the FHWA’s Traffic Noise Model implemented into SoundPLAN®.

The proposed project was modeled to analyze the potential noise impact on the neighboring land uses. Noise levels associated with the project are anticipated to comprise of the following:
• Traffic noise associated with the increased traffic on Ardmore Road • Traffic and parking activities of 994 passenger vehicles daily in the surrounding parking lots
• Truck traffic and loading of up to 80 semi-trucks daily at the loading docks on the west side of Building 1
• Truck traffic and loading of up to 60 medium delivery trucks daily at the loading dock and in the service/loading lane along the north side of Building 6 • Truck traffic and loading of up to 60 medium delivery trucks daily in the service/loading lane along the south side of Building 3
• 37 rooftop HVAC units on the six Project buildings, each modeled with a sound power level of 87 dBA rel 10-12 W (i.e., sound pressure level of 76 dBA rel 20µPa at 1-m). • All site activities were assumed to occur during daytime hours between 7am and 7pm • No vehicle idling was included for the service/loading lanes near Buildings 3 and 6 or near the loading docks at Building 1
• Refrigerated trucks are not expected at the Project site and were not included as a noise source in the model
With the project in place and the above assumptions about site traffic and rooftop HVAC equipment, the modeled Daytime Hourly LAeq levels along the property lines adjacent to residential land uses ranged up to 55 dBA and Nighttime Hourly LAeq levels ranged up to 45 dBA, both of which comply with the Municipal Code Daytime limit of 55 dBA and Nighttime limit of 45 dBA for residential land uses.

The conclusions and recommendations of this acoustical analysis are based upon the information known to 45dB Acoustics, LLC (“45dB”) at the time the analysis was prepared concerning the proposed site plans, traffic volumes, and proposed project activities. Any significant changes to these factors will require a reevaluation of the findings of this report. Additionally, any significant future changes in site plan, noise regulations, or other factors beyond 45dB’s control may result in long-term noise results that differ from those described by this analysis.

45dB Acoustics, LLC 2930 Union Rd.
page 12 noise management : room acoustics : environmental impact www.45dB.com 7 Figures
Figure 1: Aerial Map of Proposed Project Site and Surrounding Properties (GoogleMaps)

45dB Acoustics, LLC 2930 Union Rd.
page 13 noise management : room acoustics : environmental impact www.45dB.com Figure 2: Project Site Plan (Dated 2-13-2023)

45dB Acoustics, LLC 2930 Union Rd.
page 14 noise management : room acoustics : environmental impact www.45dB.com Figure 3: Daytime (“Leq,d”) Sound Level Contours, Existing Site

45dB Acoustics, LLC 2930 Union Rd.
page 15 noise management : room acoustics : environmental impact www.45dB.com Figure 4: 3D View of Site Geometry, with Proposed Project

45dB Acoustics, LLC 2930 Union Rd.
page 16 noise management : room acoustics : environmental impact www.45dB.com Figure 5: Daytime (“Leq,d”) Sound Level Contours, with Proposed Project

45dB Acoustics, LLC 2930 Union Rd.
page 17 noise management : room acoustics : environmental impact www.45dB.com 8 Appendix

8.1 Characteristics of Sound
When an object vibrates, it radiates part of its energy as acoustical pressure in the form of a sound wave. Sound can be described in terms of amplitude (loudness), frequency (pitch), or duration (time). The human hearing system is not equally sensitive to sound at all frequencies.

Therefore, to approximate this human, frequency-dependent response, the A-weighted filter system is used to adjust measured sound levels. The normal range of human hearing extends from approximately 0 to 140 dBA. Unlike linear units such as inches or pounds, decibels are measured on a logarithmic scale, representing points on a sharply rising curve. Because of the physical characteristics of noise transmission and of noise perception, the relative loudness of sound does not closely match the actual amounts of sound energy. Table 4 below presents the subjective effect of changes in sound pressure levels.

Table 4: Sound Level Change Relative Loudness/Acoustic Energy Loss5 0 dBA Reference 0%
-3 dBA Barely Perceptible Change 50%
-5 dBA Readily Perceptible Change 67%
-10 dBA Half as Loud 90%
-20 dBA 1/4 as Loud 99%
-30 dBA 1/8 as Loud 99.9%
Sound levels are generated from a source and their decibel level decreases as the distance from that source increases. Sound dissipates exponentially with distance from the noise source. This phenomenon is known as spreading loss. Generally, sound levels from a point source will decrease by 6 dBA for each doubling of distance. Sound levels for a highway line source vary differently with distance because sound pressure waves propagate along the line and overlap at the point of measurement. A closely spaced, continuous line of vehicles along a roadway becomes a line source and produces a 3 dBA decrease in sound level for each doubling of distance. However, experimental evidence has shown that where sound from a highway propagates close to “soft” ground (e.g., plowed farmland, grass, crops, etc.), a more suitable drop-off rate to use is not 3.0 dBA but rather 4.5 dBA per distance doubling (FHWA 2010).

When sound is measured for distinct time intervals, the statistical distribution of the overall sound level during that period can be obtained. The Leq is the most common parameter associated with such measurements. The Leq metric is a single-number noise descriptor that represents the average sound level over a given period of time. For example, the L50 noise level is the level that is exceeded 50 percent of the time. This level is also the level that is exceeded 30 minutes in an hour. Similarly, the L02, L08 and L25 values are the noise levels that are exceeded 2, 8, and 25 percent of the time or 1, 5, and 15 minutes per hour. Other values typically noted during a 5 Highway Traffic Noise Analysis and Abatement Policy and Guidance, U.S. Department of Transportation, Federal Highway Administration, Office of Environment and Planning, Noise and Air Quality Branch, June 1995.

45dB Acoustics, LLC 2930 Union Rd.
page 18 noise management : room acoustics : environmental impact www.45dB.com noise survey are the Lmin and Lmax. These values represent the minimum and maximum rootmean-square noise levels obtained over the measurement period.

Because community receptors are more sensitive to unwanted noise intrusion during the evening and at night, State law requires that, for planning purposes, an artificial dB increment be added to quiet-time noise levels in a 24-hour noise descriptor called the CNEL or Ldn. This increment is incorporated in the calculation of CNEL or Ldn, described earlier.

8.2 Terminology/Glossary
A-Weighted Sound Level (dBA)
The sound pressure level in decibels as measured on a sound level meter using the internationally standardized A-weighting filter or as computed from sound spectral data to which A-weighting adjustments have been made. A-weighting de-emphasizes the low and very high frequency components of the sound in a manner similar to the response of the average human ear. Aweighted sound levels correlate well with subjective reactions of people to noise and are universally used for community noise evaluations.

Air-borne Sound
Sound that travels through the air, differentiated from structure-borne sound.

Ambient Sound Level
The prevailing general sound level existing at a location or in a space, which usually consists of a composite of sounds from many sources near and far. The ambient level is typically defined by the Leq level.

Background Sound Level
The underlying, ever-present lower level noise that remains in the absence of intrusive or intermittent sounds. Distant sources, such as Traffic, typically make up the background. The background level is generally defined by the L90 percentile noise level.

Community Noise Equivalent Level (CNEL)
The Leq of the A-weighted noise level over a 24-hour period with a 5-dB penalty applied to noise levels between 7 p.m. and 10 p.m. and a 10-dB penalty applied to noise levels between 10 p.m. and 7 a.m. CNEL is similar to Ldn.

Day-Night Sound Level (Ldn)
The Leq of the A-weighted noise level over a 24-hour period with a 10-dB penalty applied to noise levels between 10 p.m. and 7 a.m. Ldn is similar to CNEL.

Decibel (dB)
The decibel is a measure on a logarithmic scale of the magnitude of a particular quantity (such as sound pressure, sound power, sound intensity) with respect to a reference quantity.

DBA or dB(A)
A-weighted sound level. The ear does not respond equally to all frequencies and is less sensitive at low and high frequencies than it is at medium or speech range frequencies. Thus, to obtain a single number representing the sound level of a noise containing a wide range of frequencies in a manner representative of the ear’s response, it is necessary to reduce the effects of the low and

45dB Acoustics, LLC 2930 Union Rd.
page 19 noise management : room acoustics : environmental impact www.45dB.com high frequencies with respect to the medium frequencies. The resultant sound level is said to be A-weighted, and the units are dBA. The A-weighted sound level is also called the noise level.

Energy Equivalent Level (Leq)
Because sound levels can vary markedly in intensity over a short period of time, some method for describing either the average character of the sound or the statistical behavior of the variations must be utilized. Most commonly, one describes ambient sounds in terms of an average level that has the same acoustical energy as the summation of all the time-varying events. This energy-equivalent sound/noise descriptor is called Leq. In this report, an hourly period is used.

Field Sound Transmission Class (FSTC)
A single number rating similar to STC, except that the transmission loss values used to derive the FSTC are measured in the field. All sound transmitted from the source room to the receiving room is assumed to be through the separating wall or floor-ceiling assembly.

Noise Reduction (NR)
Noise reduction is the difference between outdoor sound level and indoor sound level. It is not identical to Sound Transmission Class.

Outdoor-Indoor Transmission Class (OITC)
A single number classification, specified by the American Society for Testing and Materials (ASTM E1332 issued 1994), that establishes the A-weighted sound level reduction provided by building facade components (walls, doors, windows, and combinations thereof), based upon a reference sound spectrum that is an average of typical air, road, and rail transportation sources.

The OITC is the preferred rating when exterior façade components are exposed to a noise environment dominated by transportation sources. Once built, as much as a 5-point reduction in Apparent Outside-Inside Transmission Class (OITC) from the original, as-designed OITC may be expected.

Percentile Sound Level, Ln
The noise level exceeded during n percent of the measurement period, where n is a number between 0 and 100 (e.g., L10 or L90)
Sound Transmission Class (STC)
STC is a single number rating, specified by the American Society for Testing and Materials, which can be used to measure the sound insulation properties for comparing the sound transmission capability, in decibels, of interior building partitions for noise sources such as speech, radio, and television. It is used extensively for rating sound insulation characteristics of building materials and products.

Structure-Borne Sound
Sound propagating through building structure. Rapidly fluctuating elastic waves in gypsum board, joists, studs, etc.

Subjective Loudness Level
In addition to precision measurement of sound level changes, there is a subjective characteristic which describes how most people respond to sound:
• A change in sound level of 3 dBA is barely perceptible by most listeners. • A change in level of 6 dBA is clearly perceptible.

45dB Acoustics, LLC 2930 Union Rd.
page 20 noise management : room acoustics : environmental impact www.45dB.com • A change of 10 dBA is perceived by most people as being twice (or half) as loud.

8.3 SoundPLAN Acoustics Software
SoundPLAN®, the software used for this acoustic analysis, is an acoustic ray-tracing program dedicated to the prediction of noise in the environment. Noise emitted by various sources propagates and disperses over a given terrain in accordance with the laws of physics. The software calculates sound attenuation of environmental noise, even over complex terrain, uneven ground conditions, and with complex obstacles. Up to three reflections for each noise source are taken into account to closely and accurately predict real-world acoustics. Worldwide, governments and engineering associations have created algorithms to calculate acoustical phenomena to standardize the assessment of physical scenarios. Accuracy has been validated in published studies to be + / - 2.7 dBA with an 85% confidence level.

8.3.1 ISO 9613-2
For industrial and other noise sources besides road traffic, SoundPLAN calculates the sound field in accordance with ISO 9613-2 “Acoustics - Attenuation of sound during propagation outdoors, Part 2: General Method of Calculation.” The standard states that “this part of ISO 9613 specifies an engineering method for calculating the attenuation of sound during propagation outdoors, in order to predict the levels of environmental noise at a distance from a variety of sources. The method predicts the equivalent continuous A-weighted sound pressure level under meteorological conditions favorable to propagation from sources of known sound emissions.

These conditions are for downwind propagation under a well-developed moderate ground-based temperature inversion, such as commonly occurs at night.” Uncertainty of calculations with this method are +/-1 dB for sources less than 10m in height and within 1000m of the receiver.

8.3.2 Traffic Noise Model
The Federal Highway Administration Traffic Noise Model (TNM), implemented into the SoundPLAN® software, was used for the road traffic sound level modeling in this study. TNM contains the following components:

1. Modeling of five standard vehicle types, including automobiles, medium trucks, heavy trucks, buses, and motorcycles, as well as user-defined vehicles.

2. Modeling both constant- and interrupted-flow traffic using a field-measured data base.

3. Modeling effects of different pavement types, as well as the effects of graded roadways.

4. Sound level computations based on a one-third octave-band data base and algorithms.

5. Graphically-interactive noise barrier design and optimization.

6. Attenuation over/through rows of buildings and dense vegetation.

7. Multiple diffraction analysis.

8. Parallel barrier analysis.

9. Contour analysis, including sound level contours, barrier insertion loss contours, and sound-level difference contours.

These components are supported by a scientifically founded and experimentally calibrated acoustic computation methodology, as well as a flexible data base, made up of over 6000 individual pass-by events measured at forty sites across the country.

1343 Bishop Street, San Luis Obispo, CA 93401
Tel: 805 234 8760 Email: [email protected] October 21, 2022 To: Michael Stoltey – MD3 Investments & Damien Mavis – CoVelop Re: Oak Tree Impact and Protection report for Ardmore Road Project, 2930 Union Rd, Paso Robles, CA 93446
Gentlemen,
In response to your request for an Oak Assessment, Impact and Protection plan for native oaks growing on a lot you intend to purchase and develop at 2930 Union Road, I have produced the following report.

Assignment
• Collect tree data and perform Level 2 inspections on 8 valley oaks (Quercus lobata) to determine condition and suitability for retention.
• Perform advanced Level 3 Assessment with Resistograph for 3 valley oaks. • Provide written summary of condition and suitability for retention for all 8 valley oaks. • Determine Tree Protection Zones (TPZs) for all trees proposed for retention that will potentially have construction impacts occurring in the Critical Root Zone (CRZ) or within 5 feet of the CRZ per City of Paso Robles requirements.
• Produce written oak tree impact and tree protection report based on the International Society of Arboriculture’s (ISA) best management practices for tree protection during construction and City of Paso Robles tree protection requirements.

Report to include:
o Inventory of all trees being impacted
o Critical root zone calculations
o Tree protection zone calculations
o Tree impact assessment
o Tree protection requirements and standards
o Tree protection map with TPZ fencing delineated
o Photographs
Summary
The proposed project is for the construction of a multi-unit, mixed-use industrial site.

In total, I recommended six (6) native oak trees for removal based on structural and health issues.

Proposed tree removals equate to 75% of all oak trees on site.

Tree replacements are required for all native oak trees removed that are six (6) inch diameter and larger. If all proposed oak tree removals are approved, forty-five (45) native oaks at the minimum 1.5- inch caliper or thirty-four (34) native oaks at 2-inch caliper would be required to be planted on the premises or somewhere in the city, upon the Public Works Director’s approval.

2 An International Society of Arboriculture Certified Arborist shall observe and approve all construction activities that occur within or adjacent to the critical root zone (CRZ) of any trees proposed for retention.

A pre-construction meeting shall be held with the project arborist and all parties involved in the project. All tree protection fencing, and tree protection measures shall be in place before any construction activity begins. All necessary pruning shall also be completed before grading and construction.

Introduction
This project is located on an old cattle ranch. Most of the trees had been heavily impacted by cattle and were in severe decline due to root damage and drought or were structurally unstable. On August 2, 2022, I visited the site and performed a basic assessment on all native oaks 6-inch diameter and greater on the property you intend to develop. Initially, I found 4 trees were in such poor condition that I recommended their removal. One (1) tree was in good condition and deemed fit to retain.

As a result of the defects, I found during my basic inspection, 3 of the 8 trees on site required an advanced inspection with a Resistograph, wood density measuring device to determine their structural integrity. I returned to the site on August 5, 2022, and performed the advanced inspections with a Resistograph. On August 12, 2022, I collected additional data for 1 tree via a climbing inspection. I analyzed data collected during the advanced inspections and made recommendations regarding tree condition, tree risk and potential for retention. Ultimately, I determined 1 of the trees included in the advanced inspection could be retained. Combined with the tree deemed retainable during the basic inspection, I recommended 2 native oaks be retained and incorporated within the project.

All tree inspections were based on the potential for a tree to fail within the next 5 years from the date of this report. Any tree retained should be re-inspected on an annual basis to determine health and structural integrity status.

Methodology and Tools
My initial level 2 inspection consisted of a ground based, visual inspection and full walk around of the tree. I used a rubber mallet to sound the trunk to detect decay. I tagged each tree with an aluminum tag and assigned it a number. Based on a previous arborist’s inspection of the trees, I assigned the same number that was listed in their report so we would have consistency when referencing the trees.

Advanced inspections consisted of Resistograph wood density testing, and in one instance, an aerial inspection that consisted of determining the extent of decay with a tape measure.

Tree Diameter Measurements
Diameter at Standard Height (DSH) was measured at 4.5’ above ground. For multi-stem trees that divided below 4.5’, I measured below the division at the narrowest point on the trunk.

If it was not possible to measure below the division, I measured each stem individually, then squared the diameter of each stem. Finally, I summed the squared diameters and took the square root of the sum to get the most accurate diameter of the tree. Diameters were rounded up or down depending on fractions of inches.

3 Tree Numbering
I numbered all trees in the field with a rectangular metal tag and nailed it to the trunk at approximately 5 feet above ground.

Critical Root Zone Measurements
CRZs were determined by giving a radius of 1-foot per every inch of tree diameter. E.g., a 12- inch diameter tree would have a 12-foot CRZ radius measured from the outside of the trunk.

Tree Protection Zone Measurements
Generally, TPZ distances followed the distances listed for CRZs. The exception is if there were proposed tree-root encroachments into the CRZ of less than 25%. In most cases encroachments of less than 25% were allowed unless the structure or health of the tree would be compromised.

TPZ’s were also adjusted if the tree would outgrow the space and cause damage to foundations or cause clearance issues from buildings.

Tree Condition Ratings
All trees in the inventory were given a condition rating. The rating was based on the health, structure and presence of disease and insects. See the following definitions:
• Dead = Severely declining or no foliage, large dead branches, decay cavities, loss of bark, roots decayed or dead.
• Very Poor = Evidence of multiple large past failures, advanced decay, uncontrollable pest infestations or disease infection. Tree in severe decline. • Poor = Tree may be suppressed, drought stressed, or had at least 1 large branch failure.

Disease or pest infestations may be present. Can potentially be retained with attention to mitigation pruning, cultural care changes, pest and disease control. • Fair = May have had minor past failures. Some pests or structural defects may be present, small deadwood. Minor to moderate drought stress present. Defects may be mitigated with pruning and pests can be controlled.
• Good = A relatively healthy tree with minor to no structural defects with minimal to no pest observed. Defects can be mitigated with pruning and pests can be controlled. • Very Good = Trees that have had professional arboricultural care. No structural defects, disease or pests identified.
• Excellent = Specimen tree with superior form, root structure and health. Tree has been regularly cared for by professional arborists over its lifetime, E.g., estate or arboretum tree.

Inspection Levels
Level 1 – Limited Visual Inspection – This is a limited walk-by or drive-by, which does not typically include a complete walk around a tree. The inspection focuses on obvious defects, imminent or probable likelihood of failures. There are generally no tools used at this level. This is the fastest and least thorough assessment.

4 Level 2 – Basic Assessment – Generally includes a complete walk around inspection. Basic tools such as probes, measuring devices, binoculars, mallet or magnifying glass are used. At this level, an aerial inspection is not included. A Level 2 assessment is usually necessary to establish the need for a Level 3 assessment.

Level 3 – Advanced Inspection – Detailed inspection which usually employs the use of special equipment, data collection and analysis. A higher level of training is also required, such as International Society of Arboriculture (ISA) Tree Risk Assessment Qualification. Specialized equipment may include an Air Spade (device that uses compressed air to expose roots or root crown for inspections without causing damage to sensitive plant tissues).

Resistograph (drilling device used to measure and graph wood density) Level 3 inspections may also include sending samples to labs for analysis. A Level 3 inspections will usually take place later because of time needed to perform a Level 2 inspection.

Assessing Tree Structure and Potential to Fail
Estimating the structural integrity of trees is a challenge because, unlike steel I-beams or other construction materials there is no precise engineering standard to help determine the load a tree can withstand. Arborists must use measurement of decay, experience with previous, similar trees as well as factor in the various stressors on the compromised areas within the tree. Trees with thicker outer shells are going to be stronger. Oval internal decay areas and areas of decay that have broken through the outer shell of the trunk or branch will be weaker due to the inconsistency of the cylinder.

Tree Risk
Tree risk is determined by identifying the targets e.g. (people, buildings, cars or property) that could be injured or damaged by a whole or partial tree failure, the occupancy rate, exposure of the target to the tree hazard, the size of part of the tree that may impact the target if it were to fail, the likelihood of impact on the target, and the consequences of failure on the target.

The part of the tree most likely to fail and cause the largest impact is used to determine the highest overall risk for the tree.

When considering likelihood of failure, the definitions are as follows:
• Imminent – Failure has started or most likely to occur in the near future. Even if there is no significant wind or increased load. The imminent category overrides the time frame stated in the scope of work.
• Probable – Failure may be expected under normal weather conditions within the specified time frame.
• Possible – Failure may be expected in extreme weather conditions, but is unlikely during normal weather conditions during a specified time frame. • Improbable – The tree or part is not likely to fail during normal weather conditions and may not fail in extreme weather conditions within the specified time frame.

5 Risk Matrices
I used the International Society of Arboriculture’s Basic Tree Risk Assessment Form to determine risk. Matrix 1 the “Likelihood Matrix” determines the likelihood of failure and impact. The result is entered into Matrix 2, the “Risk Rating Matrix” which factors uses Consequences of Failure to get the overall risk rating. In the example below, Likelihood of failure of a part was Probable. The Likelihood of Impact was High. The result was Likely. In Matrix 2, I entered the result of Likely and entered Severe in the Consequences of Failure which gave me a risk rating of High. See example chart below.

Mitigation
When assessing risk for a tree, it is important to determine if the risk of tree failure can be reduced through mitigation. Mitigation can be made through pruning, installing cabling or bracing support structures. Moving targets out of the strike zone of a tree or restricting access to a tree are also viable mitigation measures. The recommended mitigation should not be so excessive that they compromise the health of the tree.

Tree Risk Assessments
I performed level 2 assessments on trees 1,2,3,4,9,10,11 & 13. See Tree Map Appendix B. From those assessments, I determined that trees 1, 2 and 13 required level 3 advanced inspections. Each assessment below includes a condition rating as well as potential for retention and mitigation recommendations. For level 3 inspections, I included a tree risk assessment matrix.

Tree 1 – A 43” diameter valley oak was in Very Poor condition. See Appendix A - Photographs - Photo 1.

Basic Level 2 Inspection –
This tree had drought stress which was indicated by dead wood in the canopy. It also had decay throughout its scaffold branches which was evident from the presence of decay cavities and woodpecker nests excavated in dead wood. See Appendix A - Photographs - Photos 1 & 4.

6 The trunk had an approximate lean to the east of 10 degrees. It also had a horizontal compression bulge on the east side of its trunk approximately 1’ above ground. Compression bulges or wrinkles, indicate that wood fibers are being crushed by the weight of the canopy and trunk due to lack of supportive structure in the trunk. Further the tree had a large, decayed, anchor root on its southwest side. The root was on the opposing side of the lean of the tree and is likely to fail as decay advances and stress from the weight of the canopy continues to build.

See Appendix A - Photographs - Photos 1-3.

Although this tree had a full canopy it has significant trunk decay. When I sounded the trunk with a rubber mallet, it resounded hollow on all sides. To further confirm the sounding results, I performed an advanced inspection of the decay using a Resistograph.

Advanced Level 3 Inspection -
I took 4 measurements of the wood density of the trunk at 3.5’ above ground. o Sample 1 – west side of tree. Outer shell thickness was 4” o Sample 2 – south side of tree. Outer shell thickness was 6” o Sample 3 – east side of tree. Outer shell thickness was 4” with a small 1.25” pocket of sound wood at 8” laterally, then total decay
o Sample 4 – north side of tree. Outer shell thickness was 5.25” Based on the Resistograph results, it was apparent that the interior wood of the trunk was significantly decayed. The evidence of compression bulges showed that the trunk is losing structural integrity and leaning due to lack of supportive wood fibers.

Armillaria mellea, a.k.a. Oak root fungus is a common disease in valley oaks and is likely the cause of the decay in the roots and the trunk. Christopher J. Luley in his guide Wood Decay Fungi calls this fungus Number one of the “Big Three” of the important decay fungi. Again, according to Mr. Luley, “Armillaria is a root and butt rot fungus that increases the risk of tree failure and is a pathogen capable of killing cambium of roots and lower trunk of stressed trees”.

See Appendix A - Photographs - Photos 29 & 30 for example of failed oak due to root and butt rot.

Parts Assessed – Roots and Trunk

I used the International Society of Arboriculture’s Basic Tree Risk Assessment Form to determine risk for this tree. In Matrix 1 the “Likelihood Matrix” I selected Likelihood of Failure of the roots and trunk as Probable. The Likelihood of impacting a target in a built environment would be High. The resulting Likelihood of Impact was Likely, which I entered into Matrix 2, the “Risk Rating Matrix” in the Likelihood of Failure and Impact section.

For the Consequences of Failure section of Matrix 2, I entered Severe. The Likelihood of Failure and Impact rating combined with the Consequences of Failure resulted in a risk rating of High.

7 Part Assessed – Scaffold Branches
In Matrix 1 the “Likelihood Matrix” I selected Likelihood of Failure of the scaffold branches as Probable. The Likelihood of impacting a target in a built environment would be High. The resulting Likelihood of Impact was Likely, which I entered into Matrix 2, the “Risk Rating Matrix” for the Likelihood of Failure and Impact section. Under Consequences of Failure in Matrix 2, I entered Severe. The Likelihood of Failure and Impact rating combined with the Consequences of Failure resulted in a risk rating of High.

Combined Inspection Results and Risk Assessment
The highest risk rating for this tree was High and was associated with root and trunk failure. I found decay in one anchor root and significant decay was detected in the trunk. Buckling of trunk fibers was evident. Based on shell strength measurements, the likelihood of trunk failure was probable, due to lack of structural integrity. Root failure was Probable due to significant decay in the anchor root on the southwest side of the tree. Scaffold failure was also probable with a high likelihood of failure.

8 Mitigation:

Scaffolds - Reducing the canopy through end weight reduction and removing decayed branches 2” diameter and larger would relieve some stress on remaining scaffold branches and reduce their risk to Moderate.

Roots and Trunk - Reducing the canopy through end weight reduction would relieve some stress on the trunk but not enough to offset the overall stress being exerted on the buckling area on the north side of the tree. No structural support or bracing will help the stability of the tree’s trunk or roots. Significant decay has been detected in the roots as well as the trunk. Based on shell strength measurements, lean of the tree and buckling of wood fibers on the east side of the trunk made failure likely due to lack of structural integrity. I recommend removing the tree before commencement of construction.

Tree 2 – A 47” diameter valley oak was in Poor condition. See Appendix A - Photographs - Photo 5.

Basic Level 2 Inspection –
On the south side of the trunk there was a decay cavity originating at the root-crown and extending approximately 5.5’ upward. When sounded with a rubber mallet on either side of the cavity, it resounded hollow. Moving around the trunk to the east side, I detected another hollow sounding area with my mallet at approximately 3.5’ above ground. See Appendix A - Photographs - Photo 6. Like Tree 1, I suspect Armillaria mellea - Oak root fungus, is the cause of the rot.

At approximately 8 feet above ground, on the southwest side of the trunk there was another decay area that was almost closed over with scar tissue. Although almost closed, I suspected a large area of decay behind the scar. See Appendix A - Photographs – Photo 7. There was a large scaffold branch attached to the trunk above the scar. It had a desiccated fungal fruiting body growing on it and cankers had killed strips of bark near the fungus. See Appendix A - Photographs – Photo 8. I identified the fungi genus to be that of Inonotus. Jessie A. Glaeser and Kevin T. Smith in the winter 2010 issue of Western Arborist, note this fungus to cause a white rot of heartwood in the trunk of living oaks and also decays strips or sections of sapwood, forming elongate cankers and killing the cambium. According to Swiecki, T. J.; Bernhardt, E. A. 2006, A Field Guide to Insects and Diseases of California Oaks, “Inonotus dryophilus is one of the most serious pathogens of living oaks in California associated with decline, failure, and mortality”. In this tree, the weakened trunk area at the scar combined with the heavy, decayed scaffold branch make this section of the tree likely to fail.

In the upper canopy at approximately 14’ above ground there was another decay cavity in the center of the canopy, where a large scaffold branch had failed many years ago. I suspected advanced decay in the trunk at this location. See Appendix A - Photographs - Photo 9.

9 Advanced Level 3 Inspection -
During the aerial inspection, I discovered that the opening of the decayed scaffold in the upper canopy was 13” in diameter. The depth of the cavity was 13’2” deep. When I measured the distance to the ground from the outside of the cavity, it was 14’3”, which illustrated that the entire trunk of the tree was hollow. See Appendix A - Photographs – Photos 9 -14.

From the cavity opening, the decay continued upward into the scaffold branch growing east.

This scaffold is very likely to fail due to weak trunk structure. See Appendix A - Photographs – Photo 12.

Based on the decay detected during mallet sounding, I wanted to investigate the extent of the decay further. I performed an advanced inspection for decay using a Resistograph. I took 6 measurements of the wood density of the trunk at 3.5’ above ground unless otherwise indicated.
o Sample 1 – west side of tree. Outer shell thickness was 8” o Sample 2 – south side of tree, 1’ west of decay cavity, outer shell thickness was 8.5” o Sample 3 – south side of tree at decay cavity seam, outer shell thickness was 3” at 3’ above ground.
o Sample 4 – south side of tree, 1’ east of decay cavity, outer shell thickness was 7.25” o Sample 5 – east side of tree, outer shell thickness was 5.5” o Sample 6 – north side of tree, outer shell thickness was 12” I have highlighted the tables below to show how risk was determined for the part or parts of the tree that was being considered regarding failure potential.

I used the International Society of Arboriculture’s Basic Tree Risk Assessment Form to determine risk for this tree.

Part Assessed - Trunk
In Matrix 1 the “Likelihood Matrix” I selected Likelihood of Failure of the trunk as Probable.

The Likelihood of impacting a target in a built environment would be High. The resulting Likelihood of Impact was Likely, which I entered into Matrix 2, the “Risk Rating Matrix” in the Likelihood of Failure and Impact section. Under Consequences of Failure in Matrix 2, I entered Severe. The Likelihood of the Failure and Impact rating combined with the Consequences of Failure resulted in a risk rating of High.

10 Part Assessed – Scaffold Branches
In Matrix 1 the “Likelihood Matrix” I selected Likelihood of Failure of the scaffold branches as Probable. The Likelihood of impacting a target in a built environment would be High. The resulting Likelihood of Impact was Likely, which I entered into Matrix 2, the “Risk Rating Matrix” for the Likelihood of Failure and Impact section. Under Consequences of Failure in Matrix 2, I entered Severe. The Likelihood of Failure and Impact rating combined with the Consequences of Failure resulted in a risk rating of High.

Combined Inspection Results and Risk AssessmentThe highest risk rating for this tree was High and was associated with trunk and scaffold branch failure. Significant decay was detected in the trunk and eastern scaffold branch.

Based on shell strength measurements, and the void caused by decay on the south side of the tree, the trunk is likely to fail due to lack of structural integrity. In regard to the eastern scaffold branch and other decayed branches, they could be removed, and end-weight could be reduced to relieve some stress on remaining scaffold branches. However, the reduction of the canopy would be close to 50% and would compromise the health of the tree. Further, since the trunk is not structurally sound, this negates the mitigation measure.

Mitigation: Remove tree before commencement of construction. No structural support or bracing will help the stability of the tree’s trunk.

11 Tree 3 – A 47” diameter valley oak was in Very Poor condition. When I sounded the trunk with a rubber mallet, it resounded hollow on the southwest side. A large wound left by a scaffold branch failure in the crown of the tree has since decayed and left a 3’x 4’ hollow at approximately 14’ above ground on the east side of tree. Another decay cavity on the north side of the tree at the same height as the previous, measured approximately 2’ in diameter.

Remaining scaffold was overextended and attached to the decaying trunk. The remaining parts of this tree have a high likelihood of failure. See Appendix A - Photographs – Photos 15 & 16.

Mitigation: Remove tree before commencing project.

Tree 4 – A 52” diameter valley oak was in Very Poor condition. The tree was growing off-site but had critical root zone (CRZ) and crown encroachments into your proposed construction area.

This tree has had several large scaffold branch failures.

At the failure points, significant decay was visible. The remaining scaffolds were overextended and potentially had similar internal decay and had a high likelihood of failure. See Appendix A - Photographs – Photo 17.

Mitigation: I highly recommend removal of this tree due to the advancement of decay in the scaffold branches which is compromising their structural integrity. Crown reduction needed to reduce the risk of scaffold branches failing would take up to 50% of the live canopy and jeopardize the tree’s health. Because this tree is off site, you will need to coordinate with the owner regarding removal.

At minimum this tree should have all overextended branches reduced to help prevent further failures and protect any buildings or other targets you may place on your property within striking distance of the tree. If the owner of the tree chooses to retain it, you will need to design buildings, service and loading zones outside of the CRZ.

Tree 9 – A 51” diameter valley oak was in Very Poor condition. Multiple large scaffold branches had failed. Extensive decay was present at branch failure points. Only 2 overextended scaffold branches remain, and they are connected to a decaying trunk.

When I sounded the trunk with a rubber mallet, it resounded hollow. A 3’ long by 10” wide decay cavity was on the northeast side of trunk. This tree has a high risk of complete failure. See Appendix A - Photographs – Photos 18 & 19.

Mitigation: Remove tree before commencing project.

Tree 10 – A 51” diameter valley oak was in Good condition. The trunk of the tree resounded solid when sounded with a rubber mallet. Tree form was good, but there was some large dead wood and decaying scaffolds. This tree can be retained, but it should have maintenance pruning performed prior to commencement of your project. See Appendix A - Photographs – Photos 20 & 21.

12 Mitigation: Reduce end-weight up to 25% on overextended scaffold branches. Remove dead wood 2” diameter and larger. Remove decayed and structurally unsound scaffold branches.

Supervision of pruning work by the Project Arborist shall be required.

Tree 11 – A 30” diameter valley oak was in Very Poor condition. The tree was in severe decline due to drought stress and root disease. Many of the smaller branches had died. I detected decay at the root crown on the southwest side of the tree. I found an ant nest at the root-crown decay area indicating ants are excavating and nesting in dead roots and root crown.

The dead roots contribute to the decline of the canopy and compromise the stability of the tree.

At least five, 12” average diameter scaffolds had extensive decay on the east side of the tree. To reduce scaffold failure risk, up to 50% of the live canopy would need to be removed, which would compromise the health of and already unhealthy tree. See Appendix A - Photographs – Photos 22-24.

Mitigation: Remove tree prior do commencement of project.

Tree 13 – A 42” diameter valley oak was in Poor condition.

Basic Level 2 Inspection –
The tree had a full canopy with a balanced form. On the south side of the tree at the root crown, there was an area of decay in the underside of one of the anchor roots. Like trees 1 and 2, the decay is likely caused by Armillaria mellea. I also noted the lower trunk was bulging and larger than normal which may indicate butt-rot caused by A. mellea. Further, I observed that the eastern scaffold branch was decayed, and large dead wood was present throughout the canopy.

See Appendix A - Photographs – Photos 25 - 28.

A previous report, by another arborist, expressed concern that a scar at the base of the tree might indicate decay and structural instability. When I sounded the tree’s trunk with a rubber mallet, it resounded solid, except on the north side of the trunk. Due to the difference of opinion regarding the structural integrity of the trunk, I performed an advanced inspection for decay using a Resistograph.

Advanced Level 3 Inspection -
I took 5 measurements of the wood density of the trunk at 3.5’ above ground. o Sample 1 – west side of tree. Outer shell thickness was 7” o Sample 2 – south side of tree. Outer shell thickness was 8.5” o Sample 3 – east side of tree. Outer shell thickness was 8.5” o Sample 4 – east side of tree scarred area on east side of trunk approximately 1’ above ground. Outer shell thickness was 12”.
o Sample 5 – north side of tree. Outer shell thickness was 5” Like Tree 1, the trunk of this tree had advanced internal decay, however when comparing outer shell thickness, this specimen had thicker walls and did not have indications of trunk fibers buckling, therefore its structural integrity is likely stronger.

13 Tree Risk - I used the International Society of Arboriculture’s Basic Tree Risk Assessment Form to determine the risk. I used Matrix 1 the “Likelihood Matrix” on the form and entered the result into Matrix 2, the “Risk Rating Matrix” to get the overall risk rating.

I have highlighted the tables below to show how risk was determined for the part or parts of the tree that was being considered regarding failure potential.

Part Assessed - Root

In Matrix 1 the “Likelihood Matrix” I selected Likelihood of Failure of the roots as Possible.

The Likelihood of impacting a target in a built environment would be High. The resulting Likelihood of Impact was Somewhat Likely, which I entered into Matrix 2, the “Risk Rating Matrix” for the Likelihood of Failure and Impact section. Under Consequences of Failure in Matrix 2, I entered Severe. The Likelihood of Failure and Impact rating combined with the Consequences of Failure resulted in a risk rating of Moderate.

Part Assessed – Trunk
In Matrix 1 the “Likelihood Matrix” I selected Likelihood of Failure of the scaffold branches as Probable. The Likelihood of impacting a target in a built environment would be High. The resulting Likelihood of Impact was Likely, which I entered into Matrix 2, the “Risk Rating Matrix” for the Likelihood of Failure and Impact section. Under Consequences of Failure in Matrix 2, I entered Severe. The Likelihood of Failure and Impact rating combined with the Consequences of Failure resulted in a risk rating of High.

14 Part Assessed – Scaffold Branches
In Matrix 1 the “Likelihood Matrix” I selected Likelihood of Failure of the scaffold branches as Probable. The Likelihood of impacting a target in a built environment would be High. The resulting Likelihood of Impact was Likely, which I entered into Matrix 2, the “Risk Rating Matrix” for the Likelihood of Failure and Impact section. Under Consequences of Failure in Matrix 2, I entered Severe. The Likelihood of Failure and Impact rating combined with the Consequences of Failure resulted in a risk rating of High.

Combined Inspections Results and Risk AssessmentThe highest risk rating for this tree was High and was associated with scaffold and trunk failure. I found decay in one anchor root and significant decay was detected in the trunk, however no bulging of trunk fibers was evident. Based on shell strength measurements, the likelihood of trunk failure is probable due to lack of structural integrity. Scaffold failure was also probable.

Risk of root failure remained moderate.

Mitigation:

Mitigations are meant to reduce risk without compromising the health of the tree. Ultimately, the tree manager, owner or other controlling entity must decide if the residual risk assessed is reasonable.

Scaffold Branches - Reduce end weight on overextended scaffold branches between 25% and 40% to reduce the likelihood of failure. Concentrate reduction more on the northeast and east side of the tree. Remove dead branches 2” diameter and larger. Remove decayed and structurally unsound scaffold branches. Supervision of pruning work by the Project Arborist shall be required. If all pruning recommendations are implemented, the risk of branch failure for the next 12 months will be reduced from High to Moderate.

Roots - Reducing the canopy through end weight reduction will relieve some stress on roots, however due to the overall weight of the canopy and stem, the risk rating for root failure will remain Moderate.

15 Trunk – Scaffold branch reduction will relieve some stress on the trunk of the tree, however it will not likely be enough to lower trunk failure risk to moderate. If this tree is to be retained, and the goal is to reduce the risk rating, the only reasonable way to achieve that goal will be to restrict access by installing a permanent fence around it. The fence shall be a minimum of 4.5’ tall and be built at the limits of the tree protection zone. Once access is restricted, the risk rating will be Moderate. See Trees to be Protected section on page 16 of this report for more detail regarding permanent fencing.

Critical Root Zone Calculations
According to the ISA’s definition, the CRZ is an area of soil around a tree where the minimum number of roots considered critical to the structural stability or health of the tree are located. CRZ determination is sometimes based on the drip line or a multiple of the DSH.

Per City of Paso Robles oak tree ordinance and ISA guidance, the CRZ was determined by assigning a radius of 1-foot per every inch of tree diameter. E.g., a 12-inch diameter tree would have a 12-foot CRZ radius measured from the outside of the trunk. Calculations for all oaks with CRZs potentially being impacted are listed in Appendix E - Tree Inventory and are shown in Appendix D - Tree Protection Map.

Tree Protection Zone Requirements
A tree protection zone or TPZ is similar to a CRZ. Ideally it will be the same size as the CRZ, however it can be smaller. The general rule for CRZ encroachments is that they may be allowed if the impact to critical roots is not more than 25% with no disturbance of Structural Roots (large roots that provide anchorage and stability to the tree).

Once the TPZ limits have been established, tree protection fencing shall be provided for all trees listed for protection. See Table 1 - Tree Protection Zone Measurements on page 17 of this report. Tree protection fencing is required to be in place for the duration of the construction project and shall be installed before starting any ground disturbing activities. • Do not remove any tree protection fencing or enter the TPZ without approval of the project arborist. The fencing shall delineate and protect the tree protection zone.

• The fencing shall at minimum, be 4 feet tall and made of orange, high density, polyethylene with

3.5” x 1.5” openings. It shall be installed on steel posts 8 feet on center and tightly stretched to prevent sagging. I STRONGLY recommend installing 6’ X 8’ temporary, chain-link, fence panels secured to driven steel post. This is a more secure and less moveable option than vinyl fencing that can easily be moved by hand or run over by vehicles. See Appendix C - Tree Protection Diagrams & Photos - Diagram 2 – Temporary Chain-link Fence Panel. • Trunk Protection shall also be provided – Often, the trunk of a tree will be damaged by construction equipment activities. In order to protect as much of the trunk as possible, 2” X 4” wood slats with a minimum height of 8’ shall be placed against the trunk of the tree and secured with wire or zip-ties. DO NOT use anchors such as screws or nails to connect to the trunk. See Appendix C – Tree Protection Diagrams - Diagram 3- Trunk Protection for more detail.

16 • Tree protection signs shall be placed on the TPZ fencing and be spaced 10 feet apart. Signs shall be weatherproof, and state, “Tree Protection Zone – Do Not Enter”. The signs shall also include the project manager’s and project arborist’s phone numbers. Signs shall remain in place until completion of the project. See Appendix C – Tree Protection Diagrams - Diagram 1 – Tree Protection Fencing for further detail.
• No construction or ground disturbance shall be allowed inside the fenced TPZ or CRZ without the project arborist’s permission and/or oversite. If you are unsure whether an activity is allowed, refer to Appendix D - Tree Protection Requirements – Quick Reference List or contact the project arborist Rodney Thurman at 805 234 8760.

Trees To Be Protected
There were 2 native oaks in this project that were selected for retention and will required protection due to proposed construction encroachments inside the CRZ or within 5 feet of tree canopies. All TPZ fencing shall be set as prescribed in Table 1 - Tree Protection Zone Measurements on page 17 and be completed before construction begins. Trunk protection shall also be installed before construction begins. See Appendix C - Tree Protection Diagrams & Photos- Diagrams 1-3.

If construction occurs during the months of June through November, the TPZs shall be irrigated to a depth of 12 inches 1 time before construction begins, which will ensure the trees are properly hydrated.

Additional irrigations during construction may be recommended by the project arborist.

I have recommended retaining and protecting Trees 10 & 13. Refer to Tree Protection Zone map in Appendix B Maps - Map 2.

All work within or adjacent to the CRZs of oak trees will require arborist supervision to ensure that all tree protection measures are implemented. To avoid damage to critical roots, no machine use will be allowed in the TPZ. In order to prevent undue damage to roots when grading, the grading limits along the perimeter of the TPZ shall be DUG BY HAND to the final grading depth. If a root 1” diameter or larger is exposed, it shall not be cut without the project arborist’s permission.

If the project arborist determines that a root over 1-inch diameter needs to be cut, it shall be cut by hand with a pruning saw or reciprocating saw. Once the entire perimeter outside the TPZ has been dug and roots are severed, the project arborist can approve use of machinery to complete excavation and grading if work is outside of the TPZ.

Both trees have gravity walls proposed to be built around them to prevent soil erosion. These walls shall be constructed outside the TPZ fencing area.

Tree 13 requires a permanent fence be built at the limits of the tree protection zone to restrict access. I recommend anchoring it on top of the gravity wall. The fence shall be a minimum of 4.5’ tall and be made of ornamental steel or chain-link mounted on anchored fence posts. The fence openings should not be more than 6” wide. A locked access gate shall be provided to allow maintenance personnel to access the tree. See Appendix C - Tree Protection Diagrams & Photos - Photo A, for permanent fence example.

17 Tree Removals & Tree Pruning
All tree removals and pruning maintenance shall be completed prior to construction activities.

Removals - There were 6 native oak trees that I recommended for removal. They were numbered 1,2,3,4 9 and 11. Reasons for removals are listed in Tree Risk Assessment section of this report. See Appendix A – Photographs for pictures of defects. See Appendix B – Maps - Map 1 for locations.

Tree Pruning - I have recommended that Trees 10 and 13 have mitigation pruning performed. See Appendix B – Maps - Map 1 for locations.

Tree 10 - Reduce end-weight up to 25% on overextended scaffold branches. Remove dead wood 2” diameter and larger. Remove decayed and structurally unsound scaffold branches.

Supervision of pruning work by the Project Arborist shall be required.

Tree 13 - Reduce end weight on overextended scaffold branches between 25% and 40% to relieve stress on and reduce the likelihood of failure. Concentrate reduction more on the northeast and east side of the tree. Remove dead branches 2” diameter and larger. Remove decayed and structurally unsound scaffold branches. Supervision of pruning work by the Project Arborist shall be required.

Oak Tree Replacements
The City of Paso Robles requires replacements for any native oak removed that is 6-inches in diameter or greater. This requirement is at the discretion of the Director of Public Works. The following is excerpted from the city’s Oak Tree Ordinance 835 N.S.:

Replacement oaks being equivalent to twenty-five percent of the diameter of the removed tree(s). (For example, the replacement requirement for removal of two trees of fifteen-inch DBH (thirty total diameter inches), would be seven and one-half inches (thirty inches removed multiplied by twenty-five hundredths replacement factor).

Table 1 - Tree Protection Zone Measurements
Tree # DSH CRZ TPZ Fence Distance
from tree trunk
% CRZ
Impact Specific Protection Requirements
10 51” 51’
51’ North, 48’
South.
53’ East & West
< 5
Set TPZ fencing according to measurements
provided. Refer to Tree Protection Zone map in
Appendix B Maps - Map 2
13 42” 42’ 42’ all directions 0
Set TPZ fencing according to measurements
provided. Refer to Tree Protection Zone map in
Appendix B Maps - Map 2

18 This requirement could be satisfied by planting five, one and one-half inch caliper trees, or three, two-and one-half-inch caliper trees or any other combination totaling seven and one-half inches).

A minimum of two, twenty-four-inch box, one and one-half inch minimum trunk caliper measurement trees shall be required for each oak tree removed.

Replacement trees shall be located on the same property as where the tree is approved for removal or, subject to approval of the director, arrangements can be made to locate the replacement trees on public property. Planting standards for replacement trees shall he consistent with City Standard Details and Specification L-4 except that deep root barriers shall not be required if the trees are not adjacent to sidewalk areas. Oak tree preservation and maintenance measures shall be consistent with the provisions of this chapter.

The combined diameter of the oak trees proposed for removal within your project is 270 inches.

Twenty-five percent of 270 inches is 67.5 inches. Therefore, forty-five (45) native oaks at the minimum

1.5-inch caliper or thirty-four (34) native oaks at 2-inch caliper would be required to be planted on the premises or somewhere in the city, upon the Public Works Director’s approval.

When incorporating new oak trees into your landscape, you will need to allow for at least an 8’ x 8’ planting area. Curbing for the planting area shall not count as part of the planting area dimensions.

Planting areas smaller than 8’x 8’ will result in sidewalk and curb buckling when tree roots mature.

Distances between oak trees should be no less than 25 feet. If oak trees can be incorporated into open, non-hardscape areas, they will have a higher success rate. Planting trees in groups of 3, in larger landscape planting islands is also a great way to ensure better root health and tree survival rates while maximizing parking lot shade benefits.

Landscaping – Irrigation - Amenities
Tree 10 –

• Do not till or trench within the TPZ to install landscaping or irrigation. • Install only drought tolerant and preferably California native plants beneath the tree canopy. • Irrigation shall be drip-type and all supply hoses shall be routed above ground. • Do not install overhead sprinkler irrigation because it will introduce too much moisture and potentially rot the tree’s roots.
• Do not install weed block cloth beneath the canopy of the tree. It restricts rainwater from percolating into the soil.
• Provide decorative bark as a top dressing to help retain moisture in the root zone. • Do not construct permanent concrete or brick patios beneath the canopy of the tree. • Install Raised deck patios. They are the preferred treatment for seating areas within the critical root zones of trees.

Tree 13 –
• DO NOT provide any permanent or temporary amenities such as patios or seating beneath the canopy of this tree.
• Do not till or trench within the TPZ to install landscaping or irrigation. • Install only drought tolerant and preferably California native plants beneath the tree canopy. • Irrigation shall be drip-type and all supply hoses shall be routed above ground.