2 0 0 9 G U I D E F O R D E V E L O P E R S & D E S I G N E R S
Standard Urban Stormwater Mitigation Plans (SUSMP)
Site-Specific Mitigation Plans
City of Los Angeles
Department of Public Works
Bureau of Sanitation
Watershed Protection Division
HOW TO BUILD
PROTECTION FOR MOTHER NATUREINTO YOUR PROJECT
2 0 0 9 G U I D E F O R D E V E L O P E R S & D E S I G N E R S
This handbook will give you many ideas for features you can
design and build into your projects to control stormwater
runoff that could otherwise pollute Los Angeles’ waterways.
These features include vegetated filter strips, porous pavement,
flow-through planters, parking lot tree wells, infiltration
swales, and rooftop water capture systems. From rooftops
to sidewalks, you can build a better project that benefits you,
improves the neighborhood, and protects natural resources.
Guide for:
Developers
Builders
Planners
Landscape Architects
Architects
Engineers
2 0 0 8 G U I D E F O R D E V E L O P E R S & D E S I G N E R S
T a b l e o f c o n T e n T s
2 Standard Urban Stormwater Mitigation Plan (SUSMP)
3 Site-Specific Mitigation Plan (SSMP)
4 SUSMP and Site-Specific Mitigation Plan Submittal
6 Examples of Best Management Practices (BMP’s)
8 SUSMP Infiltration Requirements and Guidelines
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secTion/elevaTion
ParkinG loT infilTraTion swale
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2 0 0 9 G u i d e f o r d e v e l o P e r s & d e s i G n e r s
standard urban stormwater Mitigation Plan
standard urban stormwater Mitigation Plan (susMP)
Project applicants are required to prepare and
implement a standard urban stormwater Mitigation
Plan (SUSMP) when their projects fall into any of
these categories:
• Single-family hillside residential developments
with grading on slopes of 25% or greater
• Housing developments of 10 or more dwelling
units (including single-family tract developments)
• Industrial/commercial developments with one
acre or more of impervious surface area
• Automotive service facilities*
• Retail gasoline outlets*
• Restaurants*
• Parking lots of 5,000 square feet or more of
surface area or with 25 or more parking spaces
The state of california requires all applicable
new development and redevelopment projects
to maximize the percentage of pervious surfaces
(surfaces that allow water to penetrate the ground
below) and minimize the amount of stormwater
drained to impervious surfaces (like pavement and
sidewalks) and into storm drains. (nPdes Permit
no. cas004001)
• Projects with 2,500 square feet or more of
impervious area that are located in, directly
adjacent to, or draining directly to designated
Environmentally Sensitive Areas (ESA)
*Developments of less than 5,000 square feet in these catagories are
only subject to the prescriptive method specified in “The City of Los
Angeles Best Management Practices Handbook Part B, 3rd Edition”.
Porous PaveMenT rain barrel veGeTaTed swale
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When a project does not fall into one of the SUSMP
categories but could still cause stormwater pollution,
the project applicant must prepare and implement a
Site-Specific Mitigation Plan. The following categories
of projects require a Site-Specific Mitigation Plan:
• Vehicle or equipment fueling areas
• Vehicle or equipment maintenance areas,
including washing and repair
• Commercial or industrial waste handling or
storage
• Outdoor handling or storage of hazardous
materials
• Outdoor manufacturing areas
• Outdoor food handling or processing
• Outdoor animal care, confinement, or slaughter
• Outdoor horticultural activities
• Major transportation projects
site-specific Mitigation Plan
redevelopment Project definition
Redevelopment projects are land-disturbing activities
that results in the creation, addition, or replacement of
5,000 square feet or more of impervious surface area
on an already developed site within the categories
listed above. Existing single-family “non-hillside”
structures are exempt from the redevelopment
requirements.
2 0 0 9 G u i d e f o r d e v e l o P e r s & d e s i G n e r s
susMP and site-specific Mitigation Plan submittal
SUSMP or Site-Specific Mitigation Plans are required
as part of the project plan submittal package.
Project applicants should contact the City of Los
Angeles, Department of Public Works, Bureau of
Sanitation, Watershed Protection Division, SUSMP
Public Counter before submitting a building permit
application to the City’s Department of Building and
Safety. Contact information for the City’s SUSMP
Public Counter is located on the inside back cover or
at lastormwater.org.
Project plans submitted to the city of los angeles,
department of Public works and department of
building and safety must include:
• Site plan showing all property lines, existing
structures and proposed improvements
• Grading plan with existing and proposed contours,
and elevations
• Landscape plan
• Detail drawings of all Best Management Practices
(BMPs) including plan view, cross sections, and
any construction details
• Stenciling note and/or detail for any new catch
basins
• Trash enclosure details
• Stormwater runoff flow calculations
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• Covenant and Agreement with Operation and
Maintenance Plan
Note: Developers may also need to submit plumbing
and architectural plans if the SUSMP BMP is located
within or adjacent to a building.
susMP and site specific Mitigation Plans shall
be included with the project plans. Only flow
calculations and the Covenant and Agreement with
the Operations and Maintenance Plan are to be
submitted on letter size page.
flow calculations: Stormwater BMPs must be
designed to capture the first 3/4-inch of a rain event.
Hydrology calculations must show the flow rate
(Qpm) and volume (Vm) of mitigated stormwater
runoff.
For more information, go to:
lastormwater.org, and click on “Businesses”,
then “For Developers”.
Plan Approval Process
Is project subject to SUSMP/SSMPrequirements?
Does project requireDiscretionary Action?
(environmental clearancezoning variance)
DBS Department of Building and Safety
WPD Watershed Protection Division
PCIS Plan Check and Inspection System
SOR Stormwater Observation Report
SUSMP Standard Urban Stormwater Mitigation Plan
SSMP Site-Specific Mitigation Plan
CITY PLANNING PLAN CHECK
NEW / REDEVELOPMENT
PROJECTS
Plan Check Engineer will issue permit after verifying that all corrections have been completed and clearances are obtained.
BUILDING & SAFETY PLAN CHECK
Projects will be inspected in accordance with the approved plan.Certificate of Occupancy will be issued when projects arecompleted, the SOR is submitted to WPD, and all required
clearances are obtained.
BUILDING & SAFETY INSPECTION
Is project subject to SUSMP/SSMPrequirements?
DBS PLAN CHECK
Applicant submits SUSMP/SSMPto WPD for review and approval.
APPLICANT
WPD will review SUSMP/SSMPand applicable documents, stamp
approved plan, and return to applicant.
WPD will clear project in PCIS.
WPD PLAN REVIEW
Plan Check Engineer will issuecorrections sheet which will referapplicants to WPD for clearance
of stormwater requirements.
Plan Check Engineer will enter intoPCIS that WPD clearance is required
prior to issuance of permit.
DBS PLAN CHECK CORRECTIONS
Imposes stormwater requirements aspart of discretionary review processand advise applicant to contact WPDfor SUSMP/SSMP requirements and
implementation plan.
CITY PLANNING
Final clearance for all conditions.
CITY PLANNING
Yes
YesYes
No
No No
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2 0 0 9 G u i d e f o r d e v e l o P e r s & d e s i G n e r s
examples of
best Management PracticesYou can build protection for Mother nature into
your plans by including features that:
• Allow rainwater and irrigation runoff to infiltrate
into the ground (first priority)
• Reduce runoff that leaves the property and drains
into gutters and storm drains
• Capture and reuse rainwater on the property
• Prevent erosion
• Keep trash and oil, grease and other pollutants
out of storm drains
The followinG exaMPles show how these helpful
design features, also called bMPs, look and work. Here
are great ways to prevent stormwater pollution, and
help project applicants prepare SUSMPs and SSMPs.
Other solutions are welcomed, as long as they curb
stormwater pollution and help protect Los Angeles’
natural resources.
visit
lastormwater.org
to get more ideas.
veGeTaTed sYsTeMs (biofilters) such as swales and
grass filter strips are designed to convey and treat ei-
ther shallow flow or sheet flow runoff. They are of-
ten densely vegetated, uniformly graded areas that
intercept sheet runoff from impervious surfaces such
as parking lots, roadways, and rooftops. Vegetated
swales are designed to slowly convey stormwater run-
off, and in the process trap pollutants, promote bio-
filtration, and reduce flow velocities.
infilTraTion sYsTeMs capture runoff and allow
it to seep into the ground. This reduces the volume
of water that is discharged to receiving water bod-
ies, thereby reducing some of the potential impacts
caused by excessive stormwater flow as well as in-
creased pollutant concentrations in the receiving
waters. Infiltration systems include infiltration ba-
sins, permeable pavement systems, and infiltration
trenches/swales, or dry wells.
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