CPC Report Appendix D Project WQMP_Part2 — Riverside City Council, April 21, 2026

APPENDIX D: PART 2
Project WQMP
- 27 -

Appendix 7: Hydromodification
Supporting Detail Relating to Hydrologic Conditions of Concern

P R A D O D A M

MYSTIC LAK
E

PRADO DA
M

BEAUMONT

WILDOMAR

MURRIETA
CANYON
LAK
E
CORONA
NORCO

CALIMESA

LAKE ELSINO
RE

BANNING

RIVERSIDE
PERRIS

JURUPA VA
LLEY
HEMET

EASTVALE

MENIFEE

SAN JACINT
O
MORENO
VALL
EY

D I A M O N D V A L L E Y

L A K E

S K I N N E R
LAKE
MATH
EWS

C A N Y O N

L A K E

E L S I N O R E

L A K E

P E R R I S
ZONE 1
ZONE 5
ZONE 3
ZONE 7
ZONE 4
ZONE 2
°
0 1 2 3 4
Miles
HCOC Applicability MapHCOC Applicability Map
Map Document: (M
:\Mdata\10108202\RCFCWCD_Hydromodification_Large_5500.mxd.mxd - IRV) - 1/9/2012 Legend
Stream T
ype
Not Susceptible
Stream Channels
Potentiall
y Susceptible Stream Channels
Large River (
Not Susceptible)
Santa Ana River
Adequate Sum
p
Watershed Areas
Not Applicable Area
Applicable Area
Applicable Area
Watershed Boundaries
Flood Control an
d Water
Conservation District Boundary
Study Area
County Bounda
ry
Hydromodificat
ion Susceptibility Documentation Report and Mapping
Riverside County Flood Control and Water Conservation District Map 2

PROJECT
SITE

1/18/22, 7:08 PM Precipitation Frequency Data Server
https://hdsc.nws.noaa.gov/hdsc/pfds/pfds_printpage.html?lat=33.9204&lon=-117.4801&data=depth&units=english&series=pds 1/4 NOAA Atlas 14, Volume 6, Version 2
Location name: Riverside, California, USA*
Latitude: 33.9204°, Longitude: -117.4801°
Elevation: 711.14 ft**
* source: ESRI Maps
** source: USGS

POINT PRECIPITATION FREQUENCY ESTIMATES
Sanja Perica, Sarah Dietz, Sarah Heim, Lillian Hiner, Kazungu Maitaria, Deborah Martin, Sandra Pavlovic, Ishani Roy, Carl Trypaluk, Dale Unruh, Fenglin Yan, Michael Yekta, Tan Zhao, Geoffrey Bonnin, Daniel Brewer, Li-Chuan Chen, Tye Parzybok, John Yarchoan NOAA, National Weather Service, Silver Spring, Maryland PF_tabular |
PF_graphical | Maps_&_aerials
PF tabular
PDS-based point precipitation frequency estimates with 90% confidence intervals (in inches)1 Duration Average recurrence interval (years)
1 2 5 10 25 50 100 200 500 1000
5-min 0.085
(0.071‑0.103)

0.120
(0.100‑0.145)

0.166
(0.138‑0.202)

0.204
(0.169‑0.250)

0.257
(0.205‑0.326)

0.299
(0.233‑0.387)

0.341
(0.259‑0.454)

0.386
(0.285‑0.529)

0.448
(0.317‑0.641)

0.497
(0.339‑0.737)
10-min 0.122
(0.102‑0.147)

0.172
(0.143‑0.208)

0.238
(0.198‑0.289)

0.293
(0.242‑0.358)

0.369
(0.294‑0.467)

0.428
(0.334‑0.555)

0.489
(0.372‑0.651)

0.554
(0.408‑0.758)

0.642
(0.454‑0.919)

0.712
(0.485‑1.06)
15-min 0.147
(0.123‑0.178)

0.208
(0.173‑0.251)

0.288
(0.240‑0.349)

0.354
(0.292‑0.433)

0.446
(0.355‑0.565)

0.518
(0.403‑0.671)

0.592
(0.450‑0.787)

0.669
(0.494‑0.917)

0.777
(0.549‑1.11)

0.862
(0.587‑1.28)
30-min 0.218
(0.182‑0.263)

0.307
(0.256‑0.371)

0.425
(0.354‑0.516)

0.523
(0.431‑0.640)

0.658
(0.524‑0.834)

0.764
(0.596‑0.991)

0.874
(0.664‑1.16)

0.989
(0.729‑1.35)

1.15 (0.810‑1.64)

1.27 (0.867‑1.89)
60-min 0.316
(0.264‑0.382)

0.446
(0.372‑0.539)

0.618
(0.514‑0.750)

0.760
(0.627‑0.930)

0.957
(0.762‑1.21)

1.11 (0.866‑1.44)

1.27 (0.965‑1.69)

1.44 (1.06‑1.97)

1.67 (1.18‑2.38)

1.85 (1.26‑2.74)
2-hr 0.465
(0.389‑0.562)

0.624
(0.521‑0.755)

0.836
(0.695‑1.01)

1.01 (0.834‑1.24)

1.25 (0.999‑1.59)

1.45 (1.13‑1.87)

1.64 (1.25‑2.18)

1.85 (1.36‑2.53)

2.13 (1.50‑3.04)

2.35 (1.60‑3.48)
3-hr 0.569
(0.476‑0.688)

0.753
(0.628‑0.911)

0.997
(0.830‑1.21)

1.20 (0.990‑1.47)

1.48 (1.18‑1.88)

1.70 (1.33‑2.21)

1.93 (1.46‑2.56)

2.16 (1.60‑2.96)

2.49 (1.76‑3.56)

2.74 (1.87‑4.07)
6-hr 0.790
(0.660‑0.954)

1.03 (0.863‑1.25)

1.36 (1.13‑1.65)

1.63 (1.34‑1.99)

2.00 (1.59‑2.54)

2.29 (1.79‑2.97)

2.59 (1.97‑3.45)

2.91 (2.15‑3.98)

3.34 (2.36‑4.78)

3.68 (2.51‑5.46)
12-hr 1.03
(0.857‑1.24)

1.36 (1.14‑1.65)

1.81 (1.51‑2.20)

2.19 (1.80‑2.68)

2.70 (2.15‑3.42)

3.10 (2.42‑4.02)

3.52 (2.67‑4.68)

3.95 (2.91‑5.41)

4.55 (3.21‑6.50)

5.02 (3.42‑7.44)
24-hr 1.35
(1.19‑1.56)

1.84 (1.62‑2.12)

2.48 (2.19‑2.88)

3.02 (2.64‑3.52)

3.75 (3.18‑4.52)

4.33 (3.59‑5.32)

4.92 (3.98‑6.19)

5.53 (4.36‑7.16)

6.38 (4.83‑8.60)

7.04 (5.15‑9.82)
2-day 1.67
(1.47‑1.92)

2.30 (2.03‑2.65)

3.13 (2.76‑3.62)

3.82 (3.34‑4.45)

4.76 (4.03‑5.73)

5.49 (4.55‑6.75)

6.24 (5.05‑7.86)

7.01 (5.53‑9.08)

8.08 (6.11‑10.9)

8.91 (6.52‑12.4)
3-day 1.80
(1.60‑2.08)

2.51 (2.22‑2.90)

3.44 (3.03‑3.98)

4.21 (3.68‑4.91)

5.26 (4.45‑6.34)

6.07 (5.03‑7.47)

6.90 (5.59‑8.70)

7.77 (6.12‑10.1)

8.95 (6.77‑12.1)

9.87 (7.22‑13.8)
4-day 1.95
(1.73‑2.25)

2.73 (2.41‑3.15)

3.77 (3.32‑4.36)

4.62 (4.04‑5.39)

5.78 (4.89‑6.97)

6.68 (5.54‑8.22)

7.61 (6.16‑9.59)

8.57 (6.75‑11.1)

9.88 (7.48‑13.3)

10.9 (7.98‑15.2)
7-day 2.24
(1.98‑2.58)

3.15 (2.78‑3.64)

4.37 (3.85‑5.06)

5.38 (4.70‑6.28)

6.78 (5.74‑8.17)

7.87 (6.52‑9.68)

8.98 (7.28‑11.3)

10.1 (8.00‑13.1)

11.8 (8.89‑15.8)

13.0 (9.52‑18.1)
10-day 2.40
(2.12‑2.77)

3.39 (3.00‑3.92)

4.73 (4.17‑5.48)

5.85 (5.12‑6.83)

7.41 (6.27‑8.93)

8.63 (7.15‑10.6)

9.89 (8.01‑12.5)

11.2 (8.83‑14.5)

13.0 (9.87‑17.6)

14.5 (10.6‑20.2)
20-day 2.87
(2.54‑3.31)

4.08 (3.61‑4.71)

5.75 (5.07‑6.66)

7.17 (6.27‑8.37)

9.18 (7.77‑11.1)

10.8 (8.94‑13.3)

12.5 (10.1‑15.7)

14.3 (11.2‑18.5)

16.8 (12.7‑22.6)

18.8 (13.7‑26.2)
30-day 3.39
(3.00‑3.91)

4.81 (4.25‑5.56)

6.81 (6.00‑7.88)

8.51 (7.44‑9.94)

11.0 (9.29‑13.2)

13.0 (10.8‑16.0)

15.1 (12.2‑19.0)

17.3 (13.7‑22.4)

20.5 (15.5‑27.7)

23.1 (16.9‑32.3)
45-day 4.01
(3.55‑4.62)

5.65 (4.99‑6.52)

7.97 (7.02‑9.23)

9.99 (8.74‑11.7)

13.0 (11.0‑15.6)

15.4 (12.8‑18.9)

18.0 (14.6‑22.7)

20.8 (16.4‑27.0)

24.9 (18.8‑33.5)

28.2 (20.6‑39.3)
60-day 4.62
(4.09‑5.33)

6.43 (5.68‑7.43)

9.04 (7.97‑10.5)

11.3 (9.91‑13.2)

14.7 (12.5‑17.7)

17.5 (14.5‑21.6)

20.6 (16.7‑25.9)

23.9 (18.8‑30.9)

28.7 (21.7‑38.7)

32.7 (23.9‑45.6)
1 Precipitation frequency (PF) estimates in this table are based on frequency analysis of partial duration series (PDS).

Numbers in parenthesis are PF estimates at lower and upper bounds of the 90% confidence interval. The probability that precipitation frequency estimates (for a given duration and average recurrence interval) will be greater than the upper bound (or less than the lower bound) is 5%. Estimates at upper bounds are not checked against probable maximum precipitation (PMP) estimates and may be higher than currently valid PMP values.

Please refer to NOAA Atlas 14 document for more information.

RIVERSIDE COUNTY FLOOD

CONTROL AND WATER

CONSERVATION DISTRICT
Isohyetal Map
for the 85th Percentile
24 hour Storm Event
July 2011
Rain Gage
Locations
Project site
1/18/22, 7:08 PM Precipitation Frequency Data Server
https://hdsc.nws.noaa.gov/hdsc/pfds/pfds_printpage.html?lat=33.9204&lon=-117.4801&data=depth&units=english&series=pds 2/4 Back to Top
Maps & aerials
Small scale terrain
1/18/22, 7:08 PM Precipitation Frequency Data Server
https://hdsc.nws.noaa.gov/hdsc/pfds/pfds_printpage.html?lat=33.9204&lon=-117.4801&data=depth&units=english&series=pds 3/4 Large scale terrain
Large scale map
Large scale aerial
+
–
3km
2mi
+
–
100km
60mi
+
–
100km
60mi
1/18/22, 7:08 PM Precipitation Frequency Data Server
https://hdsc.nws.noaa.gov/hdsc/pfds/pfds_printpage.html?lat=33.9204&lon=-117.4801&data=depth&units=english&series=pds 4/4 Back to Top
US Department of Commerce
National Oceanic and Atmospheric Administration
National Weat
her Service
National Wat
er Center
1325 East West Highway
Silver Spring, MD 20910
Questions?: [email protected]
Disclaimer
+
–
100km
60mi
- 28 -

Appendix 8: Source Control
Pollutant Sources/Source Control Checklist

S T O R M W A T E R P O L L U T A N T S O U R C E S / S O U R C E C O N T R O L C H E C K L I S T How to use this worksheet (also see instructions in Section G of the WQMP Template):

1. Review Column 1 and identify which of these potential sources of stormwater pollutants apply to your site. Check each box that applies.

2. Review Column 2 and incorporate all of the corresponding applicable BMPs in your WQMP Exhibit.

3. Review Columns 3 and 4 and incorporate all of the corresponding applicable permanent controls and operational BMPs in your WQMP. Use the format shown in Table G.1on page 23 of this WQMP Template. Describe your specific BMPs in an accompanying narrative, and explain any special conditions or situations that required omitting BMPs or substituting alternative BMPs for those shown here.

Mainta
in and periodically repaint or
replace inlet markings.

Provide stormwater pollution
prevention information to new site
owners, lessees, or operators.

See applicable operational BMPs in
Fact Sheet SC-44, Drainage System
Maintenance, in the CASQA
Stormwater Quality Handbooks at
www.cabmphandbooks.com
Include
the following in lease
agreements: Tenant shall not allow
anyone to discharge anything to storm
drains or to store or deposit materials
so as to create a potential discharge to
storm drains.
B. Interi
or floor drains
and elevator shaft sump
pumps
State t
hat interior floor drains and
elevator shaft sump pumps will be
plumbed to sanitary sewer.

Inspect a
nd maintain drains to prevent
blockages and overflow.

C. Interi
or parking
garages
State t
hat parking garage floor
drains will be plumbed to the
sanitary sewer.

Inspect a
nd maintain drains to prevent
blockages and overflow.
x x x x

S T O R M W A T E R P O L L U T A N T S O U R C E S / S O U R C E C O N T R O L C H E C K L I S T

Provid
e Integrated Pest Management
information to owners, lessees, and
operators.

D2. Lan
dscape/
Outdoor Pesticide Use
Show lo cations of native trees or
areas of shrubs and ground cover to
be undisturbed and retained.

Show self-retaining landscape
areas, if any.

Show stormwater treatment and
hydrograph modification
management BMPs. (See
instructions in Chapter 3, Step 5
and guidance in Chapter 5.)

State t
hat final landscape plans will
accomplish all of the following.

Preserve existing native trees,
shrubs, and ground cover to the
maximum extent possible.

Design landscaping to minimize
irrigation and runoff, to promote
surface infiltration where
appropriate, and to minimize the
use of fertilizers and pesticides that
can contribute to stormwater
pollution.

Where landscaped areas are used to
retain or detain stormwater, specify
plants that are tolerant of saturated
soil conditions.

Consider using pest-resistant
plants, especially adjacent to
hardscape.

To insure successful establishment,
select plants appropriate to site
soils, slopes, climate, sun, wind,
rain, land use, air movement,
ecological consistency, and plant
interactions.

Mainta
in landscaping using minimum
or no pesticides.

See applicable operational BMPs in
What you should know
for…..Landscape and Gardening at
http://rcflood.org/stormwater/Error!
Hyperlink reference not valid.

Provide IPM information to new
owners, lessees and operators.
x
x
x x
x
x
x
x

S T O R M W A T E R P O L L U T A N T S O U R C E S / S O U R C E C O N T R O L C H E C K L I S T

Show lo
cation of water feature and
a sanitary sewer cleanout in an
accessible area within 10 feet.
(Exception: Public pools must be
plumbed according to County
Department of Environmental
Health Guidelines.)
If the Co-Permittee requires pools
to be plumbed to the sanitary
sewer, place a note on the plans
and state in the narrative that this
connection will be made according
to local requirements.

See appl
icable operational BMPs in
“Guidelines for Maintaining Your
Swimming Pool, Jacuzzi and Garden
Fountain at
http://rcflood.org/stormwater/
F. Food s
ervice

For rest aurants, grocery stores, and
other food service operations, show
location (indoors or in a covered
area outdoors) of a floor sink or
other area for cleaning floor mats,
containers, and equipment.

On the drawing, show a note that
this drain will be connected to a
grease interceptor before
discharging to the sanitary sewer.

Describ e the location and features
of the designated cleaning area.

Describe the items to be cleaned in
this facility and how it has been
sized to insure that the largest
items can be accommodated.

See the
brochure, The Food Service
Industry Best Management Practices for:

Restaurants, Grocery Stores,
Delicatessens and Bakeries at
http://rcflood.org/stormwater/
Provide this brochure to new site
owners, lessees, and operators.

G. Refuse a
reas

Show wh
ere site refuse and
recycled materials will be handled
and stored for pickup. See local
municipal requirements for sizes
and other details of refuse areas.

If dumpsters or other receptacles
are outdoors, show how the
designated area will be covered,
graded, and paved to prevent run-
on and show locations of berms to
prevent runoff from the area.

Any drains from dumpsters,
compactors, and tallow bin areas
shall be connected to a grease
removal device before discharge to
sanitary sewer.

State h
ow site refuse will be
handled and provide supporting
detail to what is shown on plans.

State that signs will be posted on or
near dumpsters with the words Do
not dump hazardous materials
here or similar.

State h
ow the following will be
implemented:

Provide adequate number of
receptacles. Inspect receptacles
regularly; repair or replace leaky
receptacles. Keep receptacles covered.

Prohibit/prevent dumping of liquid or
hazardous wastes. Post no hazardous
materials signs. Inspect and pick up
litter daily and clean up spills
immediately. Keep spill control
materials available on-site. See Fact
Sheet SC-34, Waste Handling and
Disposal in the CASQA Stormwater
Quality Handbooks at
www.cabmphandbooks.com

S T O R M W A T E R P O L L U T A N T S O U R C E S / S O U R C E C O N T R O L C H E C K L I S T

No processes to drain to exterior or
to storm drain system.
See Fac
t Sheet SC-10, Non-
Stormwater Discharges in the
CASQA Stormwater Quality
Handbooks at
www.cabmphandbooks.com
See the b
rochure Industrial &
Commercial Facilities Best Management
Practices for: Industrial, Commercial
Facilities at
http://rcflood.org/stormwater/

S T O R M W A T E R P O L L U T A N T S O U R C E S / S O U R C E C O N T R O L C H E C K L I S T

Show an y outdoor storage areas,
including how materials will be
covered. Show how areas will be
graded and bermed to prevent run-
on or run-off from area.

Storage of non-hazardous liquids
shall be covered by a roof and/or
drain to the sanitary sewer system,
and be contained by berms, dikes,
liners, or vaults.

Storage of hazardous materials and
wastes must be in compliance with
the local hazardous materials
ordinance and a Hazardous
Materials Management Plan for the
site.

Include a detailed description of
materials to be stored, storage
areas, and structural features to
prevent pollutants from entering
storm drains.

Where appropriate, reference
documentation of compliance with
the requirements of Hazardous
Materials Programs for:

Hazardo
us Waste Generation
Hazardo
us Materials Release
Response and Inventory
Califo
rnia Accidental Release
(CalARP)
Abovegr
ound Storage Tank
Unifor
m Fire Code Article 80
Section 103(b) & (c) 1991
Undergr
ound Storage Tank
www.cchealth.org/groups/hazmat
/
See the
Fact Sheets SC-31, Outdoor
Liquid Container Storage and SC-33,
Outdoor Storage of Raw Materials
in the CASQA Stormwater Quality
Handbooks at
www.cabmphandbooks.com

S T O R M W A T E R P O L L U T A N T S O U R C E S / S O U R C E C O N T R O L C H E C K L I S T

IF THESE SOURCES WILL BE
ON THE PROJECT SITE …
… THEN YOUR WQMP SHOULD INCLUDE THESE SOURCE CONTROL BMPs, AS APPLICABLE 1 Potentia
l Sources of
Runoff Pollutants
2 Permanent Controls—Show on
WQMP Drawings
3 Permanent Controls—List in WQMP
Table and Narrative
4 Operational BMPs—Include in WQMP
Table and Narrative
J. Vehic
le and
Equipment Cleaning
Show on
drawings as appropriate:
(1) Commercial/industrial facilities
having vehicle/equipment cleaning
needs shall either provide a
covered, bermed area for washing
activities or discourage
vehicle/equipment washing by
removing hose bibs and installing
signs prohibiting such uses.
(2) Multi-dwelling complexes shall
have a paved, bermed, and covered
car wash area (unless car washing
is prohibited on-site and hoses are
provided with an automatic shut-
off to discourage such use).
(3) Washing areas for cars, vehicles,
and equipment shall be paved,
designed to prevent run-on to or
runoff from the area, and plumbed
to drain to the sanitary sewer.
(4) Commercial car wash facilities
shall be designed such that no
runoff from the facility is
discharged to the storm drain
system. Wastewater from the
facility shall discharge to the
sanitary sewer, or a wastewater
reclamation system shall be
installed.

If a car w
ash area is not provided,
describe any measures taken to
discourage on-site car washing and
explain how these will be enforced.

Describe o
perational measures to
implement the following (if
applicable):

Washwater from vehicle and
equipment washing operations shall
not be discharged to the storm drain
system. Refer to Outdoor Cleaning
Activities and Professional Mobile Service
Providers for many of the Potential
Sources of Runoff Pollutants categories
below. Brochure can be found at
http://rcflood.org/stormwater/
Car dea
lerships and similar may
rinse cars with water only.

Riverside City CouncilApril 21, 2026

Riverside City Council
April 21, 2026