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LID and Stormwater Technical Resource Center Update County Road Administration Board November 3, 2010 1.

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Presentation on theme: "LID and Stormwater Technical Resource Center Update County Road Administration Board November 3, 2010 1."— Presentation transcript:

1 LID and Stormwater Technical Resource Center Update County Road Administration Board November 3,

2 LID Permitting History  Current Phase 1 Permit (Allow LID)  PCHB Decision (Mandate LID)  Advisory Committees (Technical Implementation)  Draft Outline for Permit 2

3 LID GOALS To prevent changes in the natural hydrology of streams, lakes, wetlands, and other natural aquatic systems from land development; and to reduce the hydrologic changes on aquatic systems caused by existing development.

4 LID DEFINITION Low-impact development is a stormwater and land use management strategy that that strives to mimic pre-disturbance hydrologic processes of infiltration, filtration, storage, evaporation and transpiration by emphasizing conservation, use of on-site natural features, site planning, rainwater harvest, rainwater re-use, and distributed stormwater management practices that are integrated into a project design. LID strategies can be applied to new development, redevelopment, urban retrofits, and infrastructure improvements. LID strategies can have a site, subdivision, or basin scale focus.

5 What Now?  Phase I and WW Phase II Permits  Ecology has defined LID Principles LID Principles LID Techniques LID Techniques 5

6 Proposed Permit Approach  Permits would use the PCHB language and performance standard  Jurisdictions would have flexibility in the specifics of code revisions.  Deadlines for implementation would align with Growth Management Act (GMA) update deadlines 6

7 Three Pieces to LID in Permit  Basin Scale Approach  Site/Subdivision LID Development Principles LID Development Principles Performance Criteria Performance Criteria 7

8 Basin Scale  Actions that significantly increase the Urban Growth Area (UGA) or to significantly increase densities Conduct an analysis of impacts to water quality and hydrology Conduct an analysis of impacts to water quality and hydrology The analysis would be subject to a public review process The analysis would be subject to a public review process Requirement based on specific actions or triggers Requirement based on specific actions or triggers 8

9 Suggested Basin Scale Triggers  Significant Expansion of UGA Proposed as 80 acres or >5% of area of the existing UGA, whichever is smaller. Proposed as 80 acres or >5% of area of the existing UGA, whichever is smaller. The requirement would apply to cumulative increases in area. The requirement would apply to cumulative increases in area. 9

10 Suggested Basin Scale Triggers  Significant Increase in Density Proposed as any increase in density for an area of 80 acres or, for cities, >5% of the area of the incorporated city, whichever is smaller. Proposed as any increase in density for an area of 80 acres or, for cities, >5% of the area of the incorporated city, whichever is smaller. The requirement would apply to cumulative areas of increases in density. The requirement would apply to cumulative areas of increases in density. 10

11 Required Analysis  An assessment of the predicted water quality impacts  Pollution prevention measures and other mitigation alternatives.  The public interest benefits of the action, including social, environmental, and economic benefits.  Conduct the analysis and include it in the public process either as part of SEPA or under the public process for the GMA action.  The action could not allow a violation of water quality standards.  11

12 LID Development Principles  Refers to LID measures authorized through a variety of local development codes beyond the stormwater code. Examples include provisions for: clustering and impervious surface limits (zoning and subdivision code) clustering and impervious surface limits (zoning and subdivision code) narrower roads (road standards) narrower roads (road standards) native vegetation retention (clearing and grading and subdivision code) native vegetation retention (clearing and grading and subdivision code) reduced lot setbacks (zoning and utilities code) reduced lot setbacks (zoning and utilities code) 12

13 Performance Standards  Flow control is the primary standard for LID facilities Continue to meet existing standard (50% of the 2-year flow through 100% 50-year flow) Continue to meet existing standard (50% of the 2-year flow through 100% 50-year flow) Control from 8% of the 2-year flow through 50% of the 2-year flow Control from 8% of the 2-year flow through 50% of the 2-year flow  Different criteria for within UGA 13

14 Flow Duration Curve 14

15 Mandatory Techniques  On-site SW Management BMP’s of M.R. #5  Use site- appropriate development principles to retain native vegetation and minimize impervious surfaces to the extent feasible as required by local code. 15

16 Mandatory Techniques  Infiltration below pavement (permeable pavement or impermeable pavement with collection and redistribution below) for new or replaced impervious surfaces, e.g., public and private walks, driveways, patios, sports courts, roads, parking lots 16

17 Mandatory Techniques  Rain Gardens meeting a minimum size designation and through which all runoff and overflow from permeable pavement storage basins must pass. Rain gardens should comprise at least 7.5% of residential developments and 4% of commercial developments. 17

18 Mandatory Techniques  For commercial buildings (not single family residences), green roofs or an impervious roof with runoff routed below the permeable pavement parking lot (cost analysis to claim unreasonableness of green roof if latter option not used 18

19 Stormwater Technical Resource Center  HB 2222  RCW  Grants for TAPE and Tech Center  Advisory Committee 19

20 Stormwater Technical Resource Center  Web Page elopment-services/puyallups-stormwater- management-program/washington- stormwater-center/ elopment-services/puyallups-stormwater- management-program/washington- stormwater-center/ elopment-services/puyallups-stormwater- management-program/washington- stormwater-center/  20

21 TAPE Schedule  Existing technologies are being reviewed  Open application process within 1 month  Revise existing TAPE Manual by April 2011  Board of External Reviewers (BER) in place 21

22 QUESTIONS? 22

23 Comments and Questions Doug Howie (360) Wash. Dept. of Ecology P.O. Box Olympia, WA


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