OC Watersheds Water Quality Management Plan (WQMP)
What is the Model Water Quality Management Plan (WQMP)?
The Model WQMP has been developed to aid the County of Orange, the Orange County
Flood Control District, and cities of Orange County (the Permittees) and development
project proponents with addressing post-construction urban runoff and stormwater
pollution from new development and significant redevelopment projects that qualify
as Priority Projects. Priority Projects include development that creates new impervious
surface and significant redevelopment that adds or replaces 5,000 or more square
feet of impervious area on an already developed site.
The Model WQMP describes the process that Permittees will employ for developing
a Project WQMP for individual new development and significant redevelopment projects.
A Project WQMP is a plan for minimizing the adverse effects of urbanization on site
hydrology, runoff flow rates and pollutant loads. Development of a Model WQMP to
provide guidance for preparation of a Project WQMP is required by the two National
Pollutant Discharge Elimination System (NPDES) permits held jointly by the Permittees
administered by two Regional Water Quality Control Boards. The permits also require
development of Conceptual or Preliminary WQMPs prior to submission of a Project
WQMP.
In which Regional Water Quality Control Board is your project located?
Orange County is split into two Regional Water Quality Control Board jurisdictional
areas. North and Central Orange County (any area north of El Toro Road) is part
of the Santa Ana Regional Water Quality Control Board (SARWQCB). South Orange County
(any area South of El Toro Road) is part of the San Diego Regional Water Quality
Control Board (SDRWQCB). The County of Orange (Unincorporated area) and cities of
Laguna Hills, Laguna Woods and Lake Forest have land area in both Regions
Santa Ana Regional Water Quality Control Board (SARWQCB) – North of El Toro Road
In response to permit requirements from the SARWQCB, the County of Orange has prepared
a 2011 Model WQMP
to assist with project development in North and Central Orange County. Consistent
with the 2011 Model WQMP, a Project WQMP may include:
- Site design measures
- Low Impact Development (LID) Best Management Practices (BMPs)
- Participation in sub regional/regional BMPs
- Hydromodification BMPs
- Use of alternative programs or treatment control BMPs, and
- Applicable source control BMPs
This updated 2011 Model WQMP was approved by the SARWQCB on May 19, 2011 and became
effective on August 17, 2011. To assist with compliance with the SARWQCB permit
requirements and to explain aspects of the Model WQMP, a Technical Guidance Document is available for project proponents.
A compilation of all of the worksheets from the Technical Guidance Document in Word
format is also available.
San Diego Regional Water Quality Control Board (SDRWQCB) – South of El Toro Road
Check with the city in which your project is located in order to comply with their
local Project WQMP requirements. Each city’s requirements are currently based on
the 2003 Model WQMP and may vary slightly so it is important that you contact the
city in which your project is located before planning your project.
For a project in unincorporated County area south of El Toro Road, the document
that explains the requirements placed upon all new development and significant redevelopment
projects can be found by clicking on the County of Orange Local WQMP (Exhibit A-7.VI of the County’s Local
Implementation Plan)
Helping you prepare your Project Water Quality Management Plan (WQMP)
A Project WQMP template has been prepared to help guide you through the process.
Go to the city website in which your project is located and you will be able to
access their WQMP template. If your project is located in unincorporated county
land, simply click on the
OC Community Development Water Quality website and click on the WQMP template instructions.
Interim Hydromodification Criteria for Priority Development Projects in the San Diego
Regional Water Quality Control Board Jurisdiction
In addition to preparing a Project WQMP for Priority Development Projects, as of
December 16, 2010 all Priority Development Projects* in the San Diego Region are
required to comply with interim hydromodification criteria (IHC). The goal of the
IHC is to integrate hydrologic controls into a proposed project such that the flow
duration curve corresponding to the post project condition agrees with the baseline
condition curve over the range of flows of interest. This range is 10% of the 2-year
peak flow (0.1Q2) to the 10-year peak flow (Q10). The baseline condition is the
pre-development condition, which is typically oak grassland habitat.
A BMP sizing tool is available to enable project proponents to easily determine
the necessary BMP storage volume and footprint area for flow duration control as
a function of the proposed level of imperviousness and the onsite hydrologic soil
group (A/B or C/D). The four BMP types incorporated into the sizing tool are: (1)
a bioretention facility, (2) a rectangular underground vault with an open bottom,
(3) a rectangular underground vault with a closed bottom, and (4) a planter box.
While the sizing tool provides a straightforward means for sizing hydromodification
control BMPs, project applicants may prefer to conduct their own sizing analysis
in order to: (1) best reflect specific hydrologic conditions at the project site;
(2) use a type of BMP that is not included in the sizing tool; and/or (3) optimize
a BMP design to reduce storage and footprint requirements. The Technical Memorandum
describes alternative methods to the use of the sizing tool for meeting the IHC.
*The interim hydromodification criteria do not apply to Priority Development Projects
where the project discharges (1) storm water runoff into underground storm drains
discharging directly to bays or the ocean, or (2) storm water runoff into conveyance
channels whose bed and bank are concrete lined all the way from the point of discharge
to ocean waters, enclosed bays, estuaries, or water storage reservoirs and lakes.
It is the project proponent’s responsibility to field verhify the condition of the
downstream channel.
Environmentally Sensitive Areas (ESAs)
Your project may be subject to additional requirements if it:
a) involves the addition of more than 2,500 square feet of impervious surface, and
b) is located within 200 feet of or is discharging directing into receiving waters
of an Environmentally Sensitive Area.
Your project may be subject to additional requirements if it:
- includes 2,500 square feet or more of impervious surface, and
- is directly adjacent to (located within 200 feet) or is discharging directly into
receiving waters of an ESA, defined as an area such as those designated in the Ocean
Plan as an Area of Special Biological Significance or a waterbody listed
on the Clean Water Act Section 303(d) list of impaired waters.
2003 Drainage Area Management Plan (DAMP)
The current documents for the 2003 Drainage Area Management Plan (DAMP) are listed
below.
DAMP Section 7, New Development/Significant Redevelopment
- DAMP
Section 7, Exhibit 7.I, CEQA Guidance
- DAMP
Section 7, Exhibit 7.II, Model WQMP Text (For projects in Santa Ana Region through
August 16, 2011)
-
DAMP Section 7, Exhibit 7.II, Model WQMP Attachments (For projects in Santa Ana
Region through August 16, 2011)
-
County of Orange Local Implementation Plan (LIP) Section 7, Exhibit 7.VI, County
of Orange Local WQMP: (For projects in the unincorporated areas of the County
of Orange located south of El Toro Road in the San Diego Regional Water Quality
Control Board area)
We’re here to help!
In order to provide land developers, project proponents, and associated consultants
and organizations with an overview of the new land development requirements in Orange
County in the area under the jurisdiction of the Santa Ana Regional Water Quality
Control Board, training modules have been developed
to orient readers to the contents of both the updated Model WQMP and the Technical
Guidance Document. The training modules provide an overview of the level of detail
that must be included at each phase of the WQMP preparation process, site and watershed
assessment methods, LID BMP selection and prioritization methods, LID BMP design
standards and performance criteria, regional LID BMP options, watershed-based plans
and LID alternative compliance options.
OC Watersheds has also prepared a Frequently Asked Questions
(FAQs) page to address common questions that arise regarding the new land
development requirements. If you have a specific question that is not addressed
in the training modules or the FAQs, please use
our comment form to submit your question, or any comments or concerns. Please
note that it may take up to three business days to respond to your question.
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