Model BMP Design Manual for San Diego Region Public Input 2013 - - PowerPoint PPT Presentation

New “Draft”

Model BMP Design Manual for San Diego Region

June 10, 2014 & June 11, 2014 Public Input 2013 Storm Water Permit

1

W elcom e

 Sign-In  Refreshments Sponsor  Break  Q&A and Input

2

Outline of Presentation

 Introduction  Permit Requirements and Concepts  Break  Proposed Structure of the Model BMP

Design Manual

 Project Development Approaches

3

Model BMP Design Manual I ntroduction

Sumer Hasenin, P .E. City of San Diego

4

Project Development Approaches

Standard Project PDP with Only Pollutant Control Requirement PDP Integrating Hydromodification Management with Pollutant Control

Structure of the Model BMP Design Manual Permit Requirements and Concepts

Overview and changes from 2007 to 2013 MS4 Permit Source Control and Site Design Practices Storm Water Pollutant Control Requirements Hydromodification Management Requirements

Introduction

5

Project Team

 Coperm ittees Sub-w orkgroup

• Sumer Hasenin, P

.E., Chair

 Rick Engineering Com pany

• Jayne Janda-Timba, P

.E.

• Laura Henry, P

.E.

 Geosyntec Consultants

• Trevor Alsop, P

.E.

• Aaron Poresky, P

.E.

• Venkat Gummadi, P

.E.

6

Purpose of W orkshop

 New Model BMP Design Manual

 Concepts and approaches

 Public Participation

 Input during workshop  First Public Review – thru June 27th

7

W orkshop Lim itations

 Workshop will not address:

• Policies
• Local Jurisdictional Procedures
• Alternative Compliance Program

8

Perm it Background

 Pursuant to Clean Water Act  Issued by San Diego Regional Water

Quality Control Board

 Regulates Municipal Storm Drain Systems  Adopted May 2013

9

BMP Design Manual Developm ent Process

 Replaces Model SUSMP  Update due June 2015  San Diego Copermittees’ joint effort  Formed a sub-workgroup  Hired a consultant

1 0

Goals of Sub-w orkgroup

1) Responsive to permit requirements 2) Leverage available resources 3) Preserve overall approach and format 4) Integrate with local ordinances/ technical

guidance

5) Provide consistency across Jurisdictions 6) Identify opportunities to streamline

manual

1 1

I m portant Definitions

 Refer to handout - Acronyms  Permit includes complete list  Consistent with industry standards

1 2

Model BMP Design Manual

 Manual will Include:

1. Source Control & Site Design LID for All Projects 2. Storm Water Pollutant Control

I. Retention

• II. Biofiltration
• III. Flow-thru Treatment Control BMPs

3. Hydromodification Management

I. Sediment Supply

• II. Flow Control

PDP

1 3

Public Workshops June, 10 & 11 2014 Comments

• n Public

Workshop June 27, 2014 Draft Manual available Public review February 2015

Final Manual June 2015 Local Adoption Dec 2015

Developm ent Tim eline

1 4

R9-2007-0001 R9-2013-0001

Permit Adoption Date Permit Effective Date May 8, 2013 June 27, 2013 24 months BMP Design Manual Update June 26, 2015 Development Regs. Effective Date Dec 24, 2015

Perm it Tim eline

180 days

1 5

Perm it Requirem ents and Concepts Overview and Changes from

2 0 0 7 to 2 0 1 3 MS4 Perm it

Jayne Janda-Timba, P .E. Rick Engineering Company

1 6

Project Development Approaches

Standard Project PDP with Only Pollutant Control Requirement PDP Integrating Hydromodification Management with Pollutant Control

Structure of the Model BMP Design Manual Permit Requirements and Concepts

Overview and changes from 2007 to 2013 MS4 Permit Source Control and Site Design Practices Storm Water Pollutant Control Requirements Hydromodification Management Requirements

Introduction

1 7

Highlights of Changes

• Who does this apply to?
• PDP categories
• Changes for all projects
• Changes for PDPs
• Storm water treatment hierarchy
• Hydromodification management
• Compliance options

1 8

1 9

 Applies to the following activities:

• Development Projects
• Significant Redevelopment Projects
• Public and Private Projects

Developm ent Planning Requirem ents

Standard Project vs. Priority Developm ent Project

2 0

Standard Project

Standard Source Control Standard Low-Impact Development

Priority Development Project

Analysis/ Report Pollutant Control BMP Hydromodification Management Site Design & Source Control Determine if HMP Applies

Land Use

2 0 0 7 Perm it [ Total Project Area] 2 0 1 3 Perm it [ Total I m pervious Area]

Residential 10 dwelling units ≥10,000 sf Commercial 1 acre ≥10,000 sf Industrial 1 acre ≥10,000 sf Public Improvements 1 acre ≥10,000 sf Parking ≥5,000 sf OR ≥15 Parking Spaces ≥5,000 sf

Changes to PDP Categories

2 1

 Site Design/ LI D BMPs applicable to ALL

PROJECTS

• Many requirements previously applicable to

PDPs only are now applicable to ALL PROJECTS

• “Small collection strategies” and “harvesting

and using precipitation” have been added

2 2

New Requirem ents for All Projects

PDP Requirem ents Form atted Differently

 2 0 0 7 Perm it

• Low Impact Development (LID) BMP Requirements
• Treatment Control BMP Requirements
• Hydromodification Management criteria was to be

developed

 2 0 1 3 Perm it

• Storm Water Pollutant Control BMP Requirements
• Hydromodification Management BMP Requirements
• Optional Alternative Compliance

2 3

 Significant changes to the hierarchy of

treatment (pollutant control) requirements

• 2007 Permit

 Treat and release runoff  Infiltration or bioretention preferred  Filtration and/ or extended detention also accepted

2 4

Changes to PDP Requirem ents

• 2013 Permit

 Retain onsite 85th percentile runoff (infiltrate, evaporate, evapotranspire, harvest and use)  Biofiltration if infeasible to retain runoff onsite  Flow -thru treatm ent control BMPs AND m itigate ( offsite) for the design capture volume that was not retained onsite, if infeasible to retain or use biofiltration

2 5

Changed PDP Requirem ents

Hydrom odification Managem ent Changes

 Changes to exemptions  Pre-development baseline (not pre-

project condition)

 Avoid critical sediment yield areas (to be

defined by Copermittees)

2 6

PDP Com pliance Options

2 7

PDP Pollutant Control

2 Options Onsite

Retention BMP

Offsite

Biofiltration BMP

Flow-Thru Treatment Control BMP Onsite

AND

INFEASIBLE INFEASIBLE

Perm it Requirem ents and Concepts

Source Control and Site Design Practices

Aaron Poresky, P .E. Geosyntec Consultants

2 8

Project Development Approaches

Standard Project PDP with Only Pollutant Control Requirement PDP Integrating Hydromodification Management with Pollutant Control

Structure of the Model BMP Design Manual Permit Requirements and Concepts

Overview and changes from 2007 to 2013 MS4 Permit Source Control and Site Design Practices Storm Water Pollutant Control Requirements Hydromodification Management Requirements

Introduction

2 9

Source Control & Site Design for All Projects

 General Requirements

• Onsite BMPs shall be close to the source
• Structural BMPs must not be constructed

within the Waters of the U.S

• Implement measures for vector control

 Source Control BMP Requirements  Site Design BMP Requirements

(also referred to as LID BMPs)

3 0

Source Control BMP Requirem ents

Storm drain system stenciling or signage Prevention of illicit discharges into the MS4

3 1

 Protect the

following from rainfall, run-on, runoff and wind dispersal

• Outdoor material

storage areas

• Materials stored in
• utdoor work areas
• Trash storage areas

3 2

Source Control BMP Requirem ents

Source Control BMP Requirem ents

 Any additional BMPs determined to be

necessary by the Copermittee to minimize pollutant generation at each project

3 3

Site Design BMP Requirem ents

Conserve natural areas, soils and vegetation

3 4

Site Design BMP Requirem ents

Maintain natural drainage pathways and hydrologic features

3 5

Minimize Impervious Area

3 6

Site Design BMP Requirem ents

Minimize Soil Compaction

3 7

Site Design BMP Requirem ents

Disperse Impervious Areas

3 8

Site Design BMP Requirem ents

Runoff Collection (small collection strategies and permeable material)

3 9

Site Design BMP Requirem ents

Harvesting and using precipitation (City of SD has Rain Barrel Rebates)

4 0

Site Design BMP Requirem ents

Landscaping with native or drought tolerant species

4 1

Site Design BMP Requirem ents

Adjust Runoff Factors Reduced Structural BMP

Site Design Benefits for PDPs

4 2

Create Opportunities for Retention and Biofiltration Reduce or Eliminate Need for Flow-thru Treatment and Alternative Compliance

Site Design Benefits for PDPs

4 3

Perm it Requirem ents and Concepts

Storm W ater Pollutant Control Requirem ents Aaron Poresky, P .E. Geosyntec Consultants

4 4

Project Development Approaches

Standard Project PDP with Only Pollutant Control Requirement PDP Integrating Hydromodification Management with Pollutant Control

Structure of the Model BMP Design Manual Permit Requirements and Concepts

Overview and changes from 2007 to 2013 MS4 Permit Source Control and Site Design Practices Storm Water Pollutant Control Requirements Hydromodification Management Requirements

Introduction

4 5

Pollutant Control BMPs for PDPs

 Permit Requirements  Permit Hierarchy for

Onsite BMPs

 Technical Feasibility  BMP Selection Flow Chart  Storm Water Pollutant

Control BMPs

4 6

Onsite Pollutant Control BMPs

Retention BMPs Implement technically feasible retention BMPs Biofiltration BMPs Flow -thru Treatm ent Control BMPs Implement technically feasible Biofiltration BMPs for remaining volume. Treat remaining volume AND participate in alternative compliance program

4 7

Pollutant Control Requirem ent

The “New ” Standard

Infiltration

Evapotranspiration

4 8

Technical Feasibility

Physical Lim itations Site Constraints Risk of I m pacts

4 9

Technical Feasibility

Physical Lim itations

• Soil infiltration rate
• Limiting soil horizons
• High, mounded

groundwater

5 0

Technical Feasibility

5 1

Risk of I m pacts

• Groundwater and/ or soil

contamination

• Groundwater source

protection

• Groundwater mounding
• Geotechnical, setbacks
• Sanitary sewer onflow &

infiltration

• Ephemeral streams

Technical Feasibility

5 2

Site Constraints

• Elevation
• Utility conflicts
• Physical Constrains

Technical Feasibility

 Retention Feasibility

• Feasibility Screening for Harvest and Use BMPs

 Is there a demand onsite?

• Feasibility Screening for Infiltration BMPs

 Is infiltration potentially feasible and desirable?  If so, what quantity?

 Biofiltration Feasibility

• Can it be designed for remaining DCV onsite?

5 3

Project Planning and Design

Assess the site for

• pportunities

and constraints Develop the site layout Select Source Controls and Site Design BMPs

5 4

Document site planning and

• pportunity

assessment activities

Adjust runoff factor to account for site design BMPs and update DCV Priority Development Projects

Evaluate at Drainage Management Area (DMA) Scale

Estimate Design Capture Volume (DCV) Is DMA Self-retaining? NO

A

YES

5 5

BMP Selection

Com pliant w ith Pollutant Control BMP Sizing Requirem ents

Com pliant w ith Pollutant Control BMP Sizing Requirem ents YES

Is Harvest and Use Feasible? Is remaining DCV retained? Implement Harvest and Use BMPs*

NO

A

YES

B

NO * Project applicant has an option to choose between

infiltration and harvest and use BMPs if both feasible

5 6

BMP Selection

Com pliant w ith Pollutant Control BMP Sizing Requirem ents

Is Infiltration Feasible? Full Infiltration

Implement Infiltration BMPs

Partial Infiltration

Implement Bioinfiltration BMPs

No Infiltration

Implement Biofiltration BMPs

Compute Sizing Requirements Compute Sizing Requirements Compute Sizing Requirements

B C

5 7

More on this later

BMP Selection

* Project approval at the discretion of agency/ jurisdiction Com pliant w ith Pollutant Control BMP Sizing Requirem ents YES NO

C

Can the BMP be designed for the remaining DCV? Implement BMP using maximum feasible footprint and document why the remaining BMP size could not fit on site* Design BMP for the required size, per design criteria and considerations listed in the fact sheets Implement Flow-thru Treatment Control BMPs Participate in alternative compliance program to mitigate for the pollutant load not retained onsite

5 8

BMP Selection

Site planning principles incorporated, as applicable, and potential BMP locations identified; conduct feasibility screening for each DMA Site Design / Project Type Site Characteristics Watershed Characteristics Would infiltration of water in any appreciable amount be physically feasible without any negative consequences that cannot be reasonably mitigated? Would infiltration of the full design volume be feasible from a physical perspective without any undesirable consequences that cannot be reasonably mitigated?

No Infiltration Category No No

Full Infiltration Category

Yes Partial Infiltration Category Yes

 Harvest and Use if feasible, then  Biofiltration if feasible, then  Flow-thru Treatment Control BMPs  Bioinfiltration (i.e., bioretention with elevated underdrains)  Infiltration Basin  Bioretention with No Underdrain (or plugged underdrain)  Permeable Pavement

5 9

I nfiltration Feasibility

Harvest and Use BMP

Pump system for reuse Building Cistern Filter First Flush System “Roof washer” Roof Downspout Optional discharge to infiltration Irrigation valve for landscape use Access Hatches Storage discharged to infiltration Storage reserved for irrigation

BMP manual will have a Fact Sheet for:

• Cistern

Sizing

BMPs shall be sized to retain the Design Capture Volume (DCV; runoff from 85th percentile 24-hr rainfall depth)

6 0

Biofiltration Standards

 MS4 Permit requires the Copermittee's to

provide guidance for hydraulic loading rates and other biofiltration design criteria necessary to maximize storm water retention and pollutant removal

• Standards and Checklist to be included in an

Appendix of Manual

• Facilitates consistent review and approval of

Biofiltration BMPs

6 3

Rem oval Mechanism s/ Conversions

Sources/ Conversions

Influent

Concentrations Speciation Flowrates/ Volumes

Volum e Reduction

• Infiltration rates
• Underdrain

placement

• Evapotranspiration

Effluent

Concentrations Speciation Flowrates/ Volumes

Bypass

• Sizing
• Media

filtration rate

• Clogging

6 4

1) BMP selection process based on

documented feasibility analysis

2) Sized using acceptable sizing methods

described in the Model BMP Design Manual

3) Sited and designed to achieve

maximum feasible infiltration and evapotranspiration

6 5

Biofiltration Standard

4) Designed with a hydraulic loading

rate to maximize pollutant retention, preserve pollutant control/ sequestration processes, and minimize potential for pollutant washout

5) Designed to promote appropriate

biological activity to support and maintain treatment processes

6 6

Biofiltration Standard

5) Designed to prevent erosion, scour,

and channeling within the BMP

6) Include O&M design features to provide

for continued effectiveness of pollutant and flow control functions

6 7

Design features and criteria to meet these goals will be described in BMP Fact Sheets

Biofiltration Standard

6 8

Flow -thru Treatm ent Control BMPs

Check dam if bottom slope exceeds 2.5% Outlet Inlet Flow Spreader Energy Dissipater Bottom Slope: 1.5- 6% Side Slope: 3H:1V or milder

BMP manual will have Fact Sheets for

• Vegetated Swales
• Media Filters
• Sand Filters
• Dry Extended Detention Basin

6 9

Proprietary BMPs can be used as Flow-thru treatment control BMPs

Perm it Requirem ents and Concepts

Hydrom odification Managem ent Requirem ents Laura Henry, P .E. Rick Engineering Company

7 0

Project Development Approaches

Standard Project PDP with Only Pollutant Control Requirement PDP Integrating Hydromodification Management with Pollutant Control

Structure of the Model BMP Design Manual Permit Requirements and Concepts

Overview and changes from 2007 to 2013 MS4 Permit Source Control and Site Design Practices Storm Water Pollutant Control Requirements Hydromodification Management Requirements

Introduction

7 1

Hydrom odification Background I nform ation

 What is hydromodification?

• Hydromodification means changes in a

watershed’s runoff characteristics resulting from development, together with associated morphological changes to channels receiving the runoff  Hydromodification Management Plan

(HMP) for San Diego County

• Final HMP dated March 2011

72

 Strategies for hydromodification flow control

• LID Devices
• Flow control ponds
• Sizing based on continuous simulation modeling

 Methods

• San Diego BMP Sizing Calculator
• Project-specific continuous simulation modeling

73

Hydrom odification Background I nform ation

Hydrom odification Managem ent Requirem ents

 Background information  What is new under the 2013 MS4 Permit  What is not changing at this time  Logistics of implementing new/ updated

standards

 Future of San Diego BMP Sizing Calculator

7 4

Hydrom odification Managem ent Applicability

 Hydromodification management applies to

PDPs when runoff from the project site will drain to systems susceptible to erosion

 Does not apply to projects discharging runoff

to exempt water bodies

 Detailed applicability requirements will be

addressed later in this workshop

7 5

W hat is new in the 2 0 1 3 MS4 Perm it?

 Changes to applicability / exemption criteria  Requirement to control to “pre-developm ent”

condition instead of “pre-project” condition

 New requirement to protect coarse sediment

yield areas

7 6

Lane’s Diagram

7 7

From Rosgen (1996), from Lane, Proceedings, 1955. Published with the permission of American Society of Civil Engineers

W hat is NOT Changing

 Flow control performance standard

(range of flow rates to be controlled)

• 0.1, 0.3, or 0.5Q2 to Q10

 Methods to determine lower flow threshold

• SCCWRP Channel Screening Tools
• Critical Flow Calculation

7 8

 San Diego 2011 Final HMP is not being

updated

• 2011 HMP components are being incorporated into

the Model BMP Design Manual with modifications as necessary

7 9

W hat is NOT Changing

I m plem entation of Updated Standards

 Where criteria has changed, the Model BMP

Design Manual will supersede the Final HMP

• Applicability / exemption criteria
• “Pre-development” condition

 New requirements will be addressed in the

Model BMP Design Manual

• Management of critical coarse sediment yield areas

8 0

I m plem entation of Updated Standards

 Model BMP Design Manual will compile

guidance and parameters for continuous simulation modeling

8 1

BMP Sizing Calculator

 Accessing the tool  Use of BMP Sizing Calculator and sizing

factors under the 2013 MS4 Permit

8 2

BMP Sizing Calculator

 June 30, 2014 end of support for web-based

application

 LID Sizer Tool replaced with spreadsheet tool

• available now on www.projectcleanwater.org
• Sizing factors are still valid for sizing LID

facilities under the 2007 MS4 Permit

 Pond Sizer Tool will not be replaced  Critical Flow Calculator

8 3

BMP Sizing Calculator

 Under the 2013 Permit:

• Do not use “impervious” surface coefficients when

determining “pre-development” Q2 for outlet orifice sizing

• Sizing Factors for some facilities will be removed due

to inconsistency with new retention requirements

• “Treatment-Only” sizing will not be available – use

procedures presented in the Model BMP Design Manual

8 4

BREAK

1 0 Minutes

8 5

Structure of the Model BMP Design Manual

Trevor Alsop, P .E. Geosyntec Consultants

8 6

Project Development Approaches

Standard Project PDP with Only Pollutant Control Requirement PDP Integrating Hydromodification Management with Pollutant Control

Structure of the Model BMP Design Manual Permit Requirements and Concepts

Overview and changes from 2007 to 2013 MS4 Permit Source Control and Site Design Practices Storm Water Pollutant Control Requirements Hydromodification Management Requirements

Introduction

8 7

Organization

Chapter 4

Source Control and Site Design Practices for all Projects

Chapter 5

Storm Water Pollutant Control BMPs for PDPs

Chapter 6

Hydromodification Management BMPs for PDPs

Chapter 1

Policies and Procedural Requirements

Chapter 2

Performance Standards and Concepts

Chapter 3

Planning and Design

• f a Project

BMP Requirem ents Chapter 7

Long Term Operation & Maintenance

Chapter 8

Submittal Requirements

8 8

8 9

Model SUSMP Model BMP Design Manual

Chapter 1. Policies and Procedures Chapter 1. Policies and Procedural Requirements Chapter 2. Concepts and Criteria Chapter 2. Performance Standards and Concepts Chapter 3. Preparing your Project Submittal Chapter 3. Planning and Design of a Project Chapter 4. Low Impact Development Design Guide Chapter 4. Source Control and Site Design Practices for all Projects Chapter 5. Storm Water Pollutant Control BMPs for PDPs Chapter 6. Hydromodification Management BMPs for PDPs. Chapter 5. Operation & Maintenance of Stormwater Facilities Chapter 7. Long term Operation & Maintenance Chapter 8. Submittal Requirements

Chapter 4: Source Control and Site Design Practices for All Projects

Appendix A: Source Control BMP Requirements

Chapter 5: Storm Water Pollutant Control BMPs for PDPs

Appendix B: Hydrologic Calculations and Sizing Methods Appendix C: Geotechnical and Groundwater Investigation Requirements Appendix D: Approved Infiltration Rate Assessment Methods for Selection and Design of Storm Water BMPs Appendix E: BMP Design Fact Sheets Appendix F: Biofiltration Standard and Checklist

Chapter 6: Hydromodification Management BMPs for PDPs

Appendix B: Hydrologic Calculations and Sizing Methods Appendix G: Guidance for Continuous Simulation Appendix H: Regional Watershed Management Area Analysis

Chapter 8: Submittal Requirements

Appendix I: Forms and Checklists

9 0

Organization

Chapter 1 –

Model BMP Design Manual

9 1

Is Project a Priority Development Project (PDP)? Standard Project PDP with Only Pollutant Control Requirement PDP with Pollutant Control and Hydromodification Management Requirements Is Hydromodification Management Applicable? YES YES NO NO Section 2.1 & Chapter 3 Section 2.1; 2.2 & Chapter 3 Chapters 2 & 3

9 2

Chapter 3 –

Model BMP Design Manual

Step 1

• Coordinating

Between Disciplines

Step 2

• Gathering

Information About the Site

Step 3

• Site Planning and

Assessing Opportunities & Constraints Chapter 4, 5 & 6

Step 4

• Developing Final

Site Layout and Storm Water Design Chapter 4, 5, 6 & 7

Step 5

• Preparing a Project

Storm Water Submittal Chapter 8

Standard Project

Chapter 3: Planning and Design of a Project Chapter 4: Source Control and Site Design Practices for all Projects Chapter 8: Submittal Requirements

9 3

PDP W ith Pollutant Control

9 4

Chapter 3: Planning and Design of a Project BMP Requirements Chapter 4: Source Control and Site Design Practices for all Projects Chapter 5: Storm Water Pollutant Control BMPs for PDPs Chapter 7: Long Term Operation & Maintenance Chapter 8: Submittal Requirements

PDP W ith Pollutant Control & Hydrom odification Mgt.

9 5

Chapter 3: Planning and Design of a Project BMP Requirements Chapter 4: Source Control and Site Design Practices for all Projects Chapter 5: Storm Water Pollutant Control BMPs for PDPs Chapter 6: Hydromodification Management BMPs for PDPs Chapter 7: Long Term Operation & Maintenance Chapter 8: Submittal Requirements

Project Developm ent Approaches

Standard Project

Venkat Gummadi, P .E. Geosyntec Consultants

9 6

Project Development Approaches

Standard Project PDP with Only Pollutant Control Requirement PDP Integrating Hydromodification Management with Pollutant Control

Structure of the Model BMP Design Manual Permit Requirements and Concepts

Overview and changes from 2007 to 2013 MS4 Permit Source Control and Site Design Practices Storm Water Pollutant Control Requirements Hydromodification Management Requirements

Introduction

9 7

Standard Project

 Implement most of the same measures as before

9 8

Project Site Impervious Area Dispersion Minimize Impervious Areas Buffer Zones

Site Design

Protect Outdoor Storage Areas Prevent Illicit Discharges Protect Trash storage Areas

Source Control

Standard Project Must Now I m plem ent

9 9

Project Site Harvesting and using precipitation Small collection strategies Landscaping with native or drought tolerant species

New

Minimize disturbance to natural drainages Conserve natural areas, soils and vegetation Minimize soil compaction and use of permeable material

PDPs in 2007

Docum enting Design

 Use Checklists to document design

• Priority Development Project determination

Checklist

• Source Control & Site Design Checklist

 Prepare and submit a Storm Water

Management Plan

1 0 0

Project Developm ent Approaches PDP w ith Only Pollutant Control Requirem ent

Venkat Gummadi, P .E. Geosyntec Consultants

1 0 1

Project Development Approaches

Standard Project PDP with Only Pollutant Control Requirement PDP Integrating Hydromodification Management with Pollutant Control

Structure of the Model BMP Design Manual Permit Requirements and Concepts

Overview and changes from 2007 to 2013 MS4 Permit Source Control and Site Design Practices Storm Water Pollutant Control Requirements Hydromodification Management Requirements

Introduction

1 0 2

PDP w ith Only Pollutant Control Requirem ent

1 0 3

Retention BMPs Biofiltration BMPs Flow-thru Treatment Control BMPs + Alternative Compliance

Infiltration Feasibility Screening

Would infiltration of the full design volume be feasible?

1 0 4

I nfiltration Feasibility

Categorization of I nfiltration Feasibility Condition

 Part 1 - Full Infiltration Feasibility Screening

Criteria

• Is infiltration rate below proposed facility > 0.5 in/ hr.?
• Can infiltration of the full DCV be allowed without:

 increasing risk of geotechnical hazards  increasing risk of groundwater contamination  causing potential water balance issues

1 0 5

Infiltration Feasibility Screening Would infiltration of water in any appreciable amount be physically feasible? Would infiltration of the full design volume be feasible? No Full Infiltration Category Yes

1 0 6

I nfiltration Feasibility

Categorization of I nfiltration Feasibility Condition

 Part 2 - Partial Infiltration vs. No Infiltration

Feasibility Screening Criteria

• Do soil and geologic conditions allow for any

infiltration in any appreciable rate or volume?

• Can Infiltration in any appreciable quantity be

allowed without

 increasing risk of geotechnical hazards  posing significant risk for groundwater related concerns  violating downstream water rights

1 0 7

Infiltration Feasibility Screening Would infiltration of water in any appreciable amount be physically feasible? Would infiltration of the full design volume be feasible? No Infiltration Category No No Full Infiltration Category Yes Partial Infiltration Category Yes

1 0 8

I nfiltration Feasibility

PDP w ith Only Pollutant Control Requirem ent

1 0 9

Full I nfiltration

Retain

Partial I nfiltration

Bioinfiltrate; Retain as feasible, then biofilter

No I nfiltration

Biofilter Bioretention Permeable Pavement Infiltration Gallery Or equivalent Bioinfiltration Or equivalent Biofiltration Or equivalent

Docum enting Design

 Document feasibility and selection

• Criteria, checklists
• Reference supporting documents

 Use BMP Fact Sheets to design selected

BMPs

 Prepare a Storm Water Submittal

• Prepare storm water management report
• Worksheets/ checklists to document design
• O&M Plan

1 1 0

Project Developm ent Approaches

PDP I ntegrating Hydrom odification Managem ent w ith Pollutant Control Laura Henry, P .E. Rick Engineering Company

1 1 1

Project Development Approaches

Standard Project PDP with Only Pollutant Control Requirement PDP Integrating Hydromodification Management with Pollutant Control

Structure of the Model BMP Design Manual Permit Requirements and Concepts

Overview and changes from 2007 to 2013 MS4 Permit Source Control and Site Design Practices Storm Water Pollutant Control Requirements Hydromodification Management Requirements

Introduction

1 1 2

PDP Hydrom odification Mgt. & Pollutant Control

 Applicability / exemptions  Designing for “pre-development” condition  Protection of coarse sediment yield areas  Integrating hydromodification management

with pollutant control

 Using San Diego BMP Sizing Calculator LID

facilities under the 2013 MS4 Permit

1 1 3

Applicability / Exem ptions

 Review of March 2011 Final HMP

Applicability Requirements Language

• Section 6.1 HMP Applicability Requirements
• Figure 6.1 HMP Applicability Determination

1 1 4

Exem ption

2 0 0 7 Perm it 2 0 1 3 Perm it Not a Priority Development Project Exempt Exempt No increase to impervious area or peak flows Exempt Invalidated due to requirement to control to “pre-development condition”

HMP Applicability Checklist

1 1 5

Exem ption

2 0 0 7 Perm it 2 0 1 3 Perm it Direct discharge to exempt receiving water Exempt receiving waters:

• Pacific Ocean
• San Diego Bay
• Exempt river reach
• Exempt reservoir
• Tidally influenced

area Still exempt receiving waters:

• Pacific Ocean
• San Diego Bay
• Exempt reservoir

Must be re-approved through WMAA/ WQIP:

• Exempt river reach
• Tidally influenced

area

HMP Applicability Checklist

1 1 6

Exem ption

2 0 0 7 Perm it 2 0 1 3 Perm it Discharge to exempt receiving water via stabilized conveyance system Stabilized conveyance system includes:

• Existing storm

drain systems

• Concrete channels
• Stable engineered

unlined channels Still includes:

• Existing storm

drain systems

• Concrete channels

Must be re-approved through WMAA/ WQIP:

• Stable engineered

unlined channels

1 1 7

HMP Applicability Checklist

Exem ption

2 0 0 7 Perm it 2 0 1 3 Perm it Project in highly impervious watershed (> 70% impervious) Exempt Must be re-approved through WMAA/ WQIP Urban infill project Exempt Must be re-approved through WMAA/ WQIP

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HMP Applicability Checklist

Designing for “Pre-Developm ent”

 Pre-development condition runoff

means runoff conditions from the project footprint based on:

• Infiltration characteristics of the

underlying soil

• Existing grade
• No impervious area

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Protection of Critical Coarse Sedim ent Yield Areas

 Each PDP must:

• Avoid critical sediment yield areas known

to the Copermittee or identified by the

• ptional Watershed Management Area

Analysis, or

• Implement measures that allow critical

coarse sediment to be discharged to the receiving water, such that there is no net impact to the receiving water

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Protection of Critical Coarse Sedim ent Yield Areas

 How will critical coarse sediment

yield areas be protected?

• Identify locations
• Provide management measures for on-

site areas and off-site areas draining through the site

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I dentifying Critical Coarse Sedim ent Yield Areas

 Regional mapping of critical coarse sediment

yield areas will be available

 Procedures will be included to define

Geomorphic Landscape Units (GLUs)

 Procedures will be presented to identify

GLUs expected to be critical coarse sediment yield areas

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 What is a Geomorphic Landscape Unit (GLU)?

• Combination of slope, geology, and land cover

 What kind of GLU will be defined as a critical

coarse sediment yield area?

• Open (undeveloped) land cover
• Areas of high relative sediment production based on

normalized RUSLE Analysis

• Coarse-grained geologic material - material that is

expected to produce greater than 50% sand when weathered

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I dentifying Critical Coarse Sedim ent Yield Areas

 Delineate drainage boundaries for the project  Intersect project-level topographic mapping,

land cover, and geologic information to create GLUs

• For on-site areas use project-level topographic

mapping, verify the existing land cover, and use best available geologic information

• For off-site areas ok to use regional mapping

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I dentifying Critical Coarse Sedim ent Yield Areas

 Determine whether any critical coarse

sediment yield GLUs exist within the drainage boundaries

• Provide optional additional analysis to determine if

areas are not producing sediment that is critical to receiving streams

 This could refine/ reduce the area to be avoided/ protected

 Provide management measures for critical

coarse sediment yield areas

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I dentifying Critical Coarse Sedim ent Yield Areas

Managem ent Measures

 On-site areas

• Preserve natural drainage

systems

• Avoid disturbing critical coarse

sediment yield areas

• Do not process drainage from

these areas through basins that will trap sediment

Property Boundary

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Critical Coarse Sediment Yield Area

Property Boundary

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• Avoid disturbing this area
• Do not process runoff from

this area through a basin

• Preserve natural stream
• Avoid disturbing this area
• Do not process runoff from

this area through a basin

On-Site Areas

Critical Coarse Sedim ent Yield Area

Managem ent Measures

 Off-site areas draining

through the site

• Preserve natural conveyance

systems

• Allow coarse sediment from
• ff-site areas to be conveyed

through the project site

• Do not process drainage from

these areas through basins that will trap sediment

Property Boundary

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Critical Coarse Sediment Yield Area

Property Boundary

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• Allow coarse sediment from off-

site areas to be conveyed through the project site

• Do not process runoff from this

area through a basin

• Preserve natural stream on-site

Off-Site Areas

Critical Coarse Sedim ent Yield Area

Hydrom odification Mgt. w ith Pollutant Control Onsite

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Pollutant Control Capture WSL Hydromod Capture WSL Peak Flood WSL

Hydrom odification Mgt. w ith Pollutant Control Onsite

1) Evaluate feasibility to retain runoff for

pollutant control

2) Determine pollutant control category 3) Initiate design based on the pollutant

control category

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Full I nfiltration Partial I nfiltration No I nfiltration

 Design retention area to meet pollutant

control standards

 Check flow control  Increase volume as needed to meet

flow control performance standards

• Increase retention if feasible
• Employ outflow control for runoff to be

discharged from the facility as needed to meet flow control performance standards

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Full I nfiltration

Hydrom odification Mgt. w ith Pollutant Control Onsite

 Design retention area to maximize retention  Design additional runoff storage area with

• utflow control to meet flow control

performance standards

• Use biofiltration if feasible
• If not biofiltration, use a flow control basin



Address pollutant control requirements for the portion

• f the design capture volume that could not be

retained on-site

• Design biofiltration area to pollutant control

performance standards if feasible

• If not biofiltration, use flow-thru treatment control

and participate in alternative compliance program

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Partial I nfiltration

Hydrom odification Mgt. w ith Pollutant Control Onsite

 Alternative Com pliance

• Design a flow control basin to

meet flow control performance standards

• Use flow-thru treatment control

and participate in alternative compliance program

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No I nfiltration

 Biofiltration

• Design a biofiltration facility to

meet flow control performance standards

• Check pollutant control by

biofiltration

• Increase volume as needed to

address pollutant control

Hydrom odification Mgt. w ith Pollutant Control Onsite

1) Evaluate feasibility to retain runoff for pollutant

control

2) Determine pollutant control category 3) Initiate design based on pollutant control category 4) Adjust design to meet the second standard 5) Check drawdown time 6) Demonstrate each standard separately

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Hydrom odification Mgt. w ith Pollutant Control Onsite

Questions & Feedback

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Thank you for your input!

Resources:

• www.projectcleanwater.org
• Regional MS4 Permit:

 http: / / www.waterboards.ca.gov/ sandiego / water_issues/ programs/ stormwater/

 Contact Information

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Sumer Hasenin, P

.E.

City of San Diego

tel: (858) 541-4330 syhasenin@sandiego.gov

Jayne Janda-Timba, P

.E.

Rick Engineering Company

tel: (619) 688-1448 jjanda-timba@rickengineering.com