Santa Margarita Region of Riverside County
Water Quality Management Plan (WQMP), Hydromodification Management Plan (HMP)
Program Training
Presented by:
Daniel Apt, CPSWQ, CPESCVice President
Kevin VillaramaDesign Engineer
December 2, 2014
HMP Introduction & Process Module
Training Agenda
• HMP Introduction and Process Module– Recap MS4 Program Documents/Nexus w/ HMP– Background Studies– HMP Process– HMP Tools/Documents
• SMRHM Training• Sediment‐Supply Performance Standard
INTRODUCTION TO OVERALL PROGRAM
SANTA MARGARITA REGION
Santa Margarita River within Riverside County (Source: http://www.friendsoftheriver.org/site/PageServer?pagename=FORCalRiversSantaMargarita)
SMR Compliance Documents
SMR Model WQMP
SMR Project‐Specific WQMP Template
LID BMP Handbook
&SMRHM
SMR HMP
SMR HMP
• Must implement SMR HMP beginning July 11, 2014
• Section F.1.h of the 2010 SMR MS4 Permit requires:– Manage increases in runoff discharge rates and durations from PDPs
– Prevent or reduce the potential for downstream increases of erosion, sedimentation, lateral bank migration, or impacts to in‐stream vegetation
SMR HMP
• Background Studies– Retrofit Study Findings
• Purpose• Results• Alternative Compliance
– Hydromodification Susceptibility Study Findings• GeoDataBase
SMR HMP
• Santa Margarita Region Retrofit Program Study• Provides framework for selection and implementation of Best Management Practices (BMPs) at appropriate sites and scales
• Multi‐step process to identify and prioritize the BMPs best suited to address specific water quality issues
• Used to assist in Alternative Compliance
Background Studies
• HydromodificationSusceptibility Study Findings– Appendix D of the SMR
HMP
Find the susceptibility for delivering Bed Sediment to the Receiving Channel (Sediment Supply Performance Standard)
Background Studies
Use the Program GeoDatabase for localized channel susceptibility mappinghttp://rivco.permitrack.com/
SMR HMP
How to identify if my project is subject to the requirements of this HMP?
Figure 1 HMP Decision Matrix
SMR HMP – Performance Standards
Hydromodification Performance StandardAll PDPs must use continuous simulation to ensure that post‐project runoff flow rates and durations for the PDP shall not exceed pre‐development, naturally occurring, runoff flow rates and durations by more than 10% over more than 10% the length of the flow duration curve, from 10% of the 2‐year runoff event up to the 10‐year runoff event.
Sediment Supply Performance StandardMaintain the pre‐development supply of Bed Sediment to receiving channels following urban development
Meeting the Hydrologic Performance Standard
Figure 2
Meeting the Hydrologic Performance Standard
• Implement Hydrologic Control BMPs– 3 typical cases: 1. LID principles as defined in
Section 3.2. of the SMR WQMP;
2. Structural LID BMPs that may be modified or enlarged, if necessary, beyond the DCV
3. Structural Hydrologic Control BMPs may also distinct from the LID BMPs
• Size Hydrologic Control BMPs using SMRHM
Meeting the Hydrologic Performance Standard
Technical Feasibility Study demonstrating the infeasibility of onsite must be approved by Copermittee prior to investigating alternative compliance options. It should evaluate:
• Applicability of LID principles onsite;• Feasibility of
– infiltration – harvest‐and‐use BMPs based on local water demands;– implementing detention or retention BMPs onsite based on critical geotechnical considerations
Meeting the Hydrologic Performance Standard
• Alternative Compliance Options:– Option 1a – Offsite Hydrologic Control Management within the same channel system as the PDP
– Option 1b – In‐Channel Restoration or Rehabilitation of the channel receiving runoff from the PDP
– Option 2 – HMP Management Bank (not available)
SMR HMP – Exemption #1
A project is not a PDP, if it does not meet the following criteria:
New DevelopmentProjects
Threshold
New Development Projects 10,000 SF new Impervious surface
Automotive Repair Shops Dependent on SIC Code
Restaurants 5,000 SF
Hillside Developments 5,000 SF
Environmentally Sensitive Areas 2,500 SF Impervious surface
Parking Lots 5,000 SF Impervious surface
Streets, Roads, Highways and Freeways
5,000 SF Impervious surface
Retail Gasoline Outlets 5,000 SF or ADT >100
Pollutant Generating projects disturbing over 1 acre
1 acre disturbed area
SMR HMP – Exemption #1
A project is not a PDP, if it does not meet the following criteria:
Redevelopment Projects
Project creates, adds, or replaces at least 5,000 square feet of impervious surfaces on an already developed site AND The existing development AND/OR the proposed redevelopment project meets the criteria in Table 1‐1 ofthe SMR TGD
50% RuleProject results in an increase of less than 50% of the impervious surfaces compared to the previously existing development, and the existing development was not subject to WQMP requirements, the WQMP applies only to the addition or replacement, and not to the entire development.
Project results in an increase of less than 50% of the impervious surfaces compared to the previously existing development, and the existing development was not subject to WQMP requirements, the WQMP applies only to the addition or replacement, and not to the entire development.
SMR HMP – Exemption #2
• Exemptions granted to projects discharging directly or via a continuous concrete‐lined channels / MS4 facilities into:Vail Lake or Skinner Lake Large River (Drainage Area >100 sq mi & Q100= 20,000cfs)
River Downstream Limit Upstream Limit
Murrieta Creek Confluence with Santa Margarita River
Above Warm Springs Creek
Temecula Creek Confluence with Santa Margarita River
Outlet of Vail Lake
Santa Margarita River Pacific Ocean At Origin
Table 5 of SMR HMP – Large River Segments in the SMR
SMR HMP – Exemption Map
Figure 10 of SMR HMP – Also available at http://rivco.permitrack.com/
Meeting the Sediment Supply Performance Standard
• Standard: Maintain the pre‐development supply of Bed Sediment to receiving channels following urban development
WHY?Bed sediment supply plays a role in alluvial channel stability
Murrieta Creek – Vertical Degradation
Sediment Supply Performance Standard
Figure 5 ‐ Sediment Supply Performance Standard – Stepwise Approach
Is the portion of the site a Significant Source of Bed Sediment Supply? If yes: Avoid those
areas in the site design
If infeasible: By‐pass Bed Sediment Supply from those areas
If infeasible: Alternative • Sediment transport modeling•Long‐term monitoring and corrective actions
HMP Tools / Documents
• SMR Model WQMP• Santa Margarita Region Hydrology Model (SMRHM)
• SMR Project Specific WQMP Template
SMR Model WQMP
• Guidance document to aid design of PDPs in compliance with 2010 SMR MS4 Permit.
• Used in conjunction with the HMP and WQMP template to produce Project‐Specific WQMPs
SMR Model WQMP Requirements & Timeline
Requirement Type Old Requirement (2012 – July 10, 2014) New Requirement (On & After July 11, 2014)
LID Requirement BMP design to ensure onsite retention of the runoff volume produced from a 24‐hour 85th percentile storm event
Identical
Hydrologic Performance Standard
Project’s runoff flow rate, volume, velocity and duration for the post‐development condition do not exceed the pre‐development condition for the 2‐year, 24‐hour and 10‐year 24‐hour rainfall events
Project shall not exceed pre‐development, naturally occurring, runoff flow rates and durations by more than 10% over more than 10% the length of the flow duration curve, from 10% of the 2‐year runoff eventup to the 10‐year runoff event.
SMR Model WQMP Requirements & Timeline – cont.
Requirement Type Old Requirement (2012 – July 10, 2014) New Requirement (On & After July 11, 2014)
Sediment SupplyPerformance Standard
None Maintain the pre‐development supply of Bed Sediment to receiving channels due to development
Timeline 1. Before July 11, 2014 2. OR3. Project with a lawful prior approval
(Contact your Copermittee. May be an approved preliminary WQMP or Rough Grading Plan) –“Grandfathering” condition
1. On and after July 11, 2014
SMR Model WQMP‐ Overview
• Chapter 1 ‐ determine applicability of requirements apply to project• Chapter 2 ‐ key stormwater concepts and regulations, including
criteria for the design and selection of BMPs• Chapter 3 ‐ guidance to prepare a Project‐Specific WQMP• Chapter 4 ‐ strategies to coordinate Project‐Specific WQMP with
other site plans and overseeing construction of BMPs• Chapter 5 ‐ description of the process for ongoing operation and
maintenance of BMPs. Includes step‐by‐step instructions for preparing a WQMP Operation and Maintenance Plan.
SMR WQMP
Preliminary Project‐Specific WQMP• The level of detail based on knowledge of project design at the time• ID type, size, location, and final ownership of Structural BMPs• Manage runoff from an expected reasonable estimate of the area of
future roofs, driveways, and other impervious surfaces on each individual lot
• Structural BMPs not to be located on individual single‐family residential lots to ensure long‐term maintenance, particularly when those BMPs manage runoff from streets, or from common areas
SMR WQMP
Final Project Specific WQMP• Submitted with grading & improvement plans• Must be in substantial conformance w/ an approved
Preliminary Project‐Specific WQMP• Approved by the Copermittee with jurisdiction over the
project site during land use entitlement process
SMR WQMP
• The 2010 SMR MS4 Permit also requires implementation of:– LID approach (as described in Model WQMP)– SMR HMP to manage runoff discharge rates and durations from PDPs to avoid increased erosion of stream beds and banks in receiving waters.
SMR Hydrology Model (SMRHM)
• Integrated Hydrologic Control BMP sizing tool
• Continuous Hydrologic Simulation over available rainfall record
• Integrated flow‐duration analysis component, for the range of flows (10% of Q2 to Q10)
• Made available for download and use at no cost (http://www.floodcontrol.co.riverside.ca.us/NPDES/SantaMargaritaWS.aspx#SMdocs)
SMRHM – Available Resources
SMRHM Guidance Document SOCHM Reviewer Checklist
Appendix Dof
SMRHM GuidanceDocument
http://www.floodcontrol.co.riverside.ca.us/NPDES/SantaMargaritaWS.aspx#SMdocs
SMR WQMP Template
• The MS4 Permit requires preparation of a WQMP for all Development Projects
• Download document from Copermittee website (http://www.floodcontrol.co.riverside.ca.us/NPDES/SantaMargaritaWS.aspx#SMdocs)
• Use template as a live document and populate required fields
SMR WQMP Preparation –Report Outline
Section A •Project and Site Information•Identification of LID and Hydromodificationrequirements, if any
Section B•Optimize Site Utilization
Section C•Delineate Drainage Management Areas (DMAs)
Section D •Technical Feasibility•Implement LID BMPs
Section E•Technical Feasibility•Implement Hydromodification BMPs
Section F•Alternative Compliance (LID Waiver Program & Hydromodification)
Section G•Source Control BMPs
Section H•Operation, Maintenance, and Funding
Questions
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