Title: Department of Public Works
1Department of Public Works
NPDES Low Impact Development and Green Streets
Resolutions
City Council August 17, 2015
2Recommendation
- 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.
3Background
- 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
4Low 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
5Low 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)
6Low 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
7Low Impact Development
Department of Public Works
Low Impact Development BMPs
8Example 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 -
9Example 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
10Example Project 1 Alternative option (Tree Box)
- Department of Public Works
- Proposed BMP Proprietary Tree Box
- Using manufacturer sizing standard, BMP unit
needed 4x6
11Example 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 -
12Example 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
13Example 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 -
14Green 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
-
15NPDES
Department of Public Works
Questions ?