Department of Public Works

1
Department of Public Works
NPDES Low Impact Development and Green Streets
Resolutions
City Council August 17, 2015
2
Recommendation

• Department of Public Works
• It is recommended that the City Council
• 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
• 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
• Adopt a resolution approving a Green Streets
  policy for transportation corridors on
  publicly-owned street and road projects
• Repeal Resolution No. 8151, which addressed the
  stormwater and urban runoff control regulations
  under the previous Municipal National Pollutant
  Discharge Elimination System (NPDES) Permit.

3
Background

• 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

4
Low Impact Development

• Department of Public Works
• Components of the Low Impact Development
• gt Capture and treat storm water on site, before
  it runs off the parcel (rain barrels,
  infiltration areas)
• gt Focus on infiltration/biotreatment
• gt 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

5
Low Impact Development Categories

• Department of Public Works
• Projects requiring Low Impact Development
• gt Development 1 acre if 10,000 ft2 will be
  impervious
• gt Industrial/commercial 10,000 ft2
• gt Automotive service, gasoline outlets,
  restaurants and parking lots 5,000 ft2
• gt Significant Ecological Areas 2,500 ft2
• gt Redevelopment 5,000 ft2
• gt Roads, streets, highways 10,000 ft2
• gt Hillside SFR (limited requirements)

6
Low Impact Development
Department of Public Works
Previous Requirements New LID Requirements
Design Requirements Design Requirements
Can use any Best Management Practice (BMP) Tiered requirements Infiltration Harvest use 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
7
Low Impact Development
Department of Public Works
Low Impact Development BMPs
8
Example Project 1

• Department of Public Works

• Pasadena Hotel (Colorado Blvd.)
• Site characteristics gt Building addition to
  existing hotel
• gt 0.25 acres
• gt 84 impervious
• gt 1 drainage area
• gt Stormwater Volume for site 693 cubic feet
• gt Infiltration infeasible
• gt Biotreatment BMPs must be sized to 1.5 times
  the stormwater volume for the site 693 cubic
  feet x 1.5 1040 cubic feet

9
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

10
Example Project 1 Alternative option (Tree Box)

• Department of Public Works

• Proposed BMP Proprietary Tree Box
• Using manufacturer sizing standard, BMP unit
  needed 4x6

11
Example Project 2

• Department of Public Works

• Hudson Walnut
• Site characteristics
• gt Multiple story building
• gt 0.84 acres
• gt 90 impervious
• gt 3 drainage areas
• gt Stormwater Volume for site 2,245 cubic
• feet
• gt Infiltration infeasible
• gt 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

12
Example Project 2 - Planter Box Tree Box

• Department of Public Works

• Proposed BMPs Proprietary Tree Box and Flow
  Through Planter Box and Storage Tank
• Utilize stormwater storage tank to reduce planter
  box size

Stormwater
storage tank


Stormwater storage tank

13
Example Project 3 Existing Project in West
Hollywood

• Department of Public Works

• Approved and built project in the City of
  West Hollywood
• Site characteristics
• gt Mixed Use Building
• gt 0.87 acres
• gt 95 impervious
• gt 2 drainage areas
• gt Stormwater Volume for site 2,310 cubic
  feet
• gt Infiltration infeasible
• gt 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

14
Green Streets

• Department of Public Works
• Green Streets Policy requires the use of
  strategies for transportation corridors
• gt Modeled after LA Countys Green Streets policy
• gt 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
• gt Exempt activities include
• Slurry seal
• Resurfacing - grind and overlay

15
NPDES
Department of Public Works
Questions ?