Redondo Beach City Council
February 7, 2023

B.A. SIMS ENGINEERING, INC.
1341 Orizaba Avenue
Long Beach, CA 90804
Ph (562) 735-4955
Fx (562) 735-4965
www.basims.com

HYDROLOGY / LID STUDY

PROPOSED RESIDENCE
1021 N. HARBOR DR.

REDONDO BEACH, CA 90027
22327-R0.xmcd
11/4/2022
Purpose of this document:

To provide supporting hydraulic calculations for the proposed residential development.

Design criteria:
1) Greater LA County Municipal Separate Storm Sewer System. Order #R4-2012-0175, NPDES CAS004001. 2) LACDPW Hyd. Design Manual, 2019 California Building Code / City of Redondo Beach.

Definition of Units:
k 1000 lb :=  ksi k
in2
:= pcf lb
ft3
:= psf lb
ft2
:= plf lb
ft
:= psi lb
in2
:= sf ft2:= ftk ft k :=  ksf k
ft2
:=
cfs ft3
sec
:= gpm
gal
min
:= fps ft
sec
:= cy 27 ft3:=  cf ft3:= ea 1 :=
EXP: 6/30/24
9/14/2020
B.A. SIMS ENGINEERING, INC.
1341 Orizaba Avenue
Long Beach, CA 90804
Ph (562) 735-4955
Fx (562) 735-4965
www.basims.com

HYDROLOGY / LID STUDY

PROPOSED RESIDENCE
1021 N. HARBOR DR.

REDONDO BEACH, CA 90027
22327-R0.xmcd
11/4/2022
Design Parameters:

Lot size: Atotal := 37313 sf  Atotal = 0.857 acre 
Areas: Pervious surfaces (including planters): A1
:= 6397 sf  (pervious area)
Concrete/Hardscape: A2
:= 13721 sf  (impervious)
Roof Area: A3
:= 17195 sf  (impervious)
Acheck A1 + A2 + A3 37313 ft2:= =
Imperviousness of lot (proposed): Imperv Atotal - A1 30916 ft2 := =
Imperv 30916 sf = 
Total impervious %: Imperv
Atotal
= 0.83 IMP 0.95 :=
General hyd. Calculations:

See 'Fig. 1' attached. From LACDPWHM , Figure: 1-H1.3, Appendix B.

Soil class area: 010
50 yr ISOHYET: REDUCTION FACTOR: RF 1.0 :=
ISO50 := 5.1 RF  in
24-hr intensity: I1440
ISO50
24hr
:= I1440 0.21
in
hr
= 
Assumed initial time of
concentration: tc
:= 7 min 
Convert to 50-year, 7 min
intensity:

I50
1440
tc
min









0.47 I1440 :=  I50 2.60
in
hr
= 
From App. C, curve #010: CU := 0.61 See 'Fig. 2' attached.

CD := 0.9 IMP  + ( ) C 1.0 IMP -  U CD = 0.89
Qtotal CD I50  Atotal :=  Qtotal = 1.99 cfs  Qtotal = 891.75 gpm  For ENTIRE Lot B.A. SIMS ENGINEERING, INC.
1341 Orizaba Avenue
Long Beach, CA 90804
Ph (562) 735-4955
Fx (562) 735-4965
www.basims.com

HYDROLOGY / LID STUDY

PROPOSED RESIDENCE
1021 N. HARBOR DR.

REDONDO BEACH, CA 90027
22327-R0.xmcd
11/4/2022
Site drainage calculations:

Low Impact Development Design :

Site must retain 0.75" 24-hr event, or 85th percentile 24-hr event per LA County 85th% Iso map, whichever is greater.

See map and info attached (Fig. 3).

PSWQDv := 0.65 in < 0.75 inches, Use 0.75" as per City of Hermosa Beach Requirements instead of 0.65" obtained from Figure 3 (attached).

PDESIGN := 0.75 in
Total 24-hr volume: ACATCH ( ) A2 + A3
:= .9 + ( ) A10.1 ACATCH = 28464.10 sf 
V24 PDESIGN
1ft
12in







:= ACATCH V24 1.78 103=  cf
SWQDv is the same as the Total 24-hr volume. SWQDv V24 := SWQDv 1.78 103 =  cf
Determine Capture and Use Feasibility: Use LA COUNTY LID Appendix F sample calculations.

Design Volume: Calculated above V24 = 1779.01 cf 
Planter Factor: PF 0.4 := low water use plants
only, per WUCOLS.

Planting Area: PA PF A( )1
 2558.8 ft2:= =
ETWU7 21.7 0.62  PA
gal
ft2
:=  = 4602.10 cf  if ETWU7 > V24 ( ) , "OK" , "NO GOOD" = "OK" Therefore, Capture and Use is feasible and shall not be implemented.

Planter Box Design:

Tributary Roof Areas: Tributary Hardscape Areas:

Area A: AA := 870 sf 
Area 1: A3 17195 ft2
=
Area B: AB := 871 sf 
Area C: AC := 871 sf 
B.A. SIMS ENGINEERING, INC.
1341 Orizaba Avenue
Long Beach, CA 90804
Ph (562) 735-4955
Fx (562) 735-4965
www.basims.com

HYDROLOGY / LID STUDY

PROPOSED RESIDENCE
1021 N. HARBOR DR.

REDONDO BEACH, CA 90027
22327-R0.xmcd
11/4/2022
LID Planter Box Design:

Summary Table
Area (sf) % of total Area portion of Vm (cf)
Roof - 2200 100% 150.0
Subtotal - 2200 100% 150.0***
Hardscape - 256
Driveway - 156
Landscape - 238
Total - 2850 - - *** 100% design volume mitigated onsite.

Planter areas
Vm = 150.0 cf
Permeable Pavers, see sheet C-1.0
To sheet flow to driveway on 1st Court
NOTE: Refer to "Appendix F sample design calculations for planter boxes" for more information.

Planter Box Sizing: Vm := 1780 cf  Roof Area to flow to LID Planter Design Volume: Vdesign := 1.5 V( ) m = 2670.0 cf 
Design infiltration rate: KSat.Design
5 in
hr

2 2.50
in
hr
:= =  (factor of safety of 2)
Max. ponding depth: dp
:= 1 ft  Time to fill 2 ft. of planter media: Tfill := 2 hr  Use LID (Hard-Bottom) Planter Box.

Total Planter Area provided = 1880 sf,
therefore OK.

BMP Surface Area AAmin
Vdesign
Tfill KSat.Design ( )  + dp

1.88 103 ft2:= =
B.A. SIMS ENGINEERING, INC.
1341 Orizaba Avenue
Long Beach, CA 90804
Ph (562) 735-4955
Fx (562) 735-4965
www.basims.com

HYDROLOGY / LID STUDY

PROPOSED RESIDENCE
1021 N. HARBOR DR.

REDONDO BEACH, CA 90027
22327-R0.xmcd
11/4/2022
Site Drainage Calculations:

Qsump 125% Qtotal :=  Qsump = 1114.68 gpm
See Zoeller info attached.

Use Duplex Sump System.

SAY 190 GPM.

Qpump
Qsump
6 ea 
:= Qpump = 185.78 gpm
TOTAL STATIC HEAD OF PUMP: hs
:= 93.77 ft  - 86.00 ft  hs = 7.77 ft Conservatively, SAY 8 FT.

Total pipe length to discharge point: L 72 ft :=  use (1) 4" pipes, (6) for each pump.

Elbows, bends, and check valves: Use (2) Zoeller Model 292 pumps.

See Zoeller pump sizing software input/output attached. (FIG 4) The program calculates total dynamic head (TDH) and required pump based off of inputs.

Required basin size: must retain 1 min of Qpump: Volreqd 1 min  Qtotal :=  Volreqd = 891.75 gal  Try 36" SQ. X 36" DEEP

OLDCASTLE PRECAST BASIN,
See plans for more information.

VolREQVAULT
Volreqd
3 ea 
:= VolREQVAULT = 297.25 gal
Vol 48 in :=  48in36in Vol 359.06 gal =  OK
Discharge velocity: must be < 3 ft/s: r 2 in :=  (for 4" pipe) V
Qtotal
12 3.14  r
2 
:= V 1.9
ft
s
= < 3 ft/s. Use (2) 4" pipes, (6) for each pump.

B.A. SIMS ENGINEERING, INC.
1341 Orizaba Avenue
Long Beach, CA 90804
Ph (562) 735-4955
Fx (562) 735-4965
www.basims.com

HYDROLOGY / LID STUDY

PROPOSED RESIDENCE
1021 N. HARBOR DR.

REDONDO BEACH, CA 90027
22327-R0.xmcd
11/4/2022
Basement Wall
Drainage Calculations:

Basement retaining wall drainage will collect and flow to a sump system.

Water will then be pumped to the street, if necessary.

Abasement := 19819 sf 
Qonsite Abasement0.025
gpm
sf
:=
Qsump 125% Qonsite :=  Qsump = 619.34 gpm
See Zoeller info attached.

Use Duplex Sump System.

SAY 55 GPM.

Qpump
Qsump
4 ea 
:= Qpump = 154.84 gpm
TOTAL STATIC HEAD OF PUMP: hs
:= 93.64 ft  - 86.90 ft  hs = 6.74 ft Conservatively, SAY 8 FT.

Total pipe length to discharge point: L 36 ft :=  use (3) 4" pipes, (1) for each pump.

Elbows, bends, and check valves: Use (2) Zoeller Model 95 pumps.

See Zoeller pump sizing software input/output attached (FIG 5).

The program calculates total dynamic head (TDH) and required pump based off of inputs.

Required basin size: must retain 1 min of Qpump:

Volreqd 1 min 
Qonsite
2 :=  Volreqd = 247.74 gal 
Try 36" SQ. X 36" DEEP

OLDCASTLE PRECAST BASIN,
See plans for more information. Vol 48 in :=  48in36in Vol 359.06 gal =  OK Discharge velocity: must be < 3 ft/s: r 2 in :=  (for 4" pipe) V
Qonsite
6 3.14  r
2 
:= V 2.11
ft
s
= < 3 ft/s. Use (3) 4" pipes, (1) for each pump.
<<< END OF CALCULATIONS >>>