Department of Public Works

NPDESLow Impact Development and

Green Streets Resolutions

City CouncilAugust 17, 2015

Department of Public Works

It is recommended that the City Council: 1. Find the resolutions proposed herein to be exempt under the California

Environmental Quality Act (CEQA) in accordance with Title 14 Chapter 3, Class 8, Section 15308, actions taken by regulatory agencies to assure the maintenance, restoration, enhancement, or protection of the environment

2. Adopt a resolution approving the amended Stormwater and Urban Runoff Pollution Control Legal Authority for New or Redevelopment Projects to expand the existing Standard Urban Stormwater Mitigation Plan (SUSMP) requirements by imposing Low Impact Development (LID) strategies and Green Streets policies

3. Adopt a resolution approving a Green Streets policy for transportation corridors on publicly-owned street and road projects

4. Repeal Resolution No. 8151, which addressed the stormwater and urban runoff control regulations under the previous Municipal National Pollutant Discharge Elimination System (NPDES) Permit.

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Recommendation

Department of Public Works

• December 28, 2012 – New Municipal Separate Storm Sewer System (MS4) Permit became effective

• June 2013 – Notice of Intent to develop an Enhanced Watershed Management Program (EWMP) & Coordinated Integrated Monitoring Program (CIMP) with other agencies submitted to Los Angeles Regional Water Quality Control Board (Regional Board)

• June 28, 2015 – EWMP & CIMP submitted to the Regional Board

• June 28, 2015 – Low Impact Development (LID) and Green Streets requirements in effect

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Background

Department of Public Works

• Components of the Low Impact Development:> Capture and treat storm water on site, before it runs

off the parcel (rain barrels, infiltration areas)> Focus on infiltration/biotreatment> Design requirements and prescriptive language

• Large number of small projects have significant effect on pollutant reduction

• Minimize impervious area and control runoff from impervious surfaces through infiltration

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Low Impact Development

Department of Public Works

• Projects requiring Low Impact Development: > Development ≥ 1 acre if 10,000 ft2 will be impervious > Industrial/commercial ≥ 10,000 ft2

> Automotive service, gasoline outlets, restaurants and parking lots ≥ 5,000 ft2

> Significant Ecological Areas ≥ 2,500 ft2

> Redevelopment ≥ 5,000 ft2

> Roads, streets, highways ≥ 10,000 ft2

> Hillside SFR (limited requirements)

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Low Impact Development Categories

Department of Public Works

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Low Impact Development

Previous Requirements New LID RequirementsDesign Requirements

• Can use any Best Management Practice (BMP)

• Tiered requirements: 1. Infiltration2. Harvest & use 3. Biotreatment

• Infiltration not Required • Must deem infiltration and harvest & use infeasible prior to using biotreatment

• Treat 0.75-inch, 24-hour rain event

• Same numerical criteria for all BMPs

• No Specification

• Treat 0.75-inch, 24-hour rain event or the 85th percentile, 24-hour rain event, whichever is greater

• Biotreatment BMPs must be sized to 1.5 times the design volume

• Prescriptive design specifications

Department of Public Works

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Low Impact Development

Low Impact Development BMPs

Example Project #1

Department of Public Works

Pasadena Hotel (Colorado Blvd.)

• Site characteristics > Building addition to existing hotel

> 0.25 acres

> 84% impervious

> 1 drainage area

> Stormwater Volume for site = 693 cubic feet

> Infiltration infeasible

> Biotreatment BMPs must be sized to 1.5 times the stormwater volume for the site 693 cubic feet x 1.5 = 1040 cubic feet

Example Project #1 – Planter Box

Department of Public Works• Proposed BMP – Flow Through Planter

Box

• Using design standard, minimum area needed for the BMP is 692 square feet

• Various size configurations could be selected

Example Project #1 – Alternative option (Tree Box)

Department of Public Works

• Proposed BMP – Proprietary Tree Box

• Using manufacturer sizing standard, BMP unit needed = 4x6

Example Project #2

Department of Public Works

Hudson & Walnut

•Site characteristics > Multiple story building

> 0.84 acres

> 90% impervious

> 3 drainage areas

> Stormwater Volume for site = 2,245 cubic

feet

> Infiltration infeasible

> Biotreatment BMPs must be sized to 1.5 times the stormwater volume for the site 2,245 cubic feet x 1.5 = 3,367 cubic feet

Example Project #2 - Planter Box & Tree Box

Department of Public Works

Stormwater storage tank

Stormwater storage tank

• Proposed BMPs – Proprietary Tree Box and Flow Through Planter Box and Storage Tank

• Utilize stormwater storage tank to reduce planter box size

Example Project #3 – Existing Project in West Hollywood

Department of Public Works

Approved and built project in the City of West Hollywood

• Site characteristics

> Mixed Use Building

> 0.87 acres

> 95% impervious

> 2 drainage areas

> Stormwater Volume for site = 2,310 cubic feet

> Infiltration infeasible

> Biotreatment BMPs must be sized to 1.5 times the stormwater volume for the site 2,245 cubic feet x 1.5 = 3,456 cubic feet

• Proposed BMPs –Storage Tank and Flow Through Planter Box

Department of Public Works• Green Streets Policy requires the use of

strategies for transportation corridors> Modeled after LA County’s Green

Streets policy

> Reference Document: USEPA guidance regarding Managing Wet Weather with Green Infrastructure: Green Streets

• Required for construction of ≥ 10,000 SF of impervious area in transportation corridors

• Does not include routine maintenance activities to maintain the original street alignment and elevations > Exempt activities include:

Slurry seal Resurfacing - grind and overlay

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Green Streets

Department of Public Works

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NPDES

Questions ?