Low-Impact Development Code Update 2016 Overview Thurston County - - PowerPoint PPT Presentation

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Low-Impact Development Code Update 2016 Overview Thurston County - - PowerPoint PPT Presentation

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Low-Impact Development Code Update 2016 Overview Thurston County Planning Commission January 20, 2016 Allison Osterberg, Associate Planner Resource Stewardship What is LID? Ecology definition: Low-impact development (LID) is a stormwater

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Low-Impact Development Code Update 2016 Overview

Thurston County Planning Commission January 20, 2016 Allison Osterberg, Associate Planner Resource Stewardship

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What is LID?

  • Ecology definition:

Low-impact development (LID) is a stormwater and land use management strategy 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, and distributed stormwater management practices that are integrated into a project design.

  • Key LID Principles
  • Conserve vegetation
  • Reduce and disconnect impervious surfaces
  • Infiltrate runoff on site
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Why do we need to update the codes?

  • NPDES Municipal Stormwater Permit, reissued in 2013
  • Review codes to make LID the “preferred and commonly-used

approach to site development”

  • Should consider measures to minimize:
  • Impervious surfaces
  • Loss of native vegetation
  • Stormwater runoff
  • Deadline: December 31, 2016
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How are the codes reviewed?

  • Internal County Workgroup
  • Multiple county departments
  • Provided initial recommended changes
  • Community Stakeholder Advisory Group
  • Provided feedback
  • Includes representatives from developers, builders, realtors,

landscapers, contractors, SSWAB, and others

  • Interjurisdictional Work Group
  • Discussed codes for Lacey, Olympia, Tumwater and UGAs
  • Planning Commission
  • Board of Commissioners – Final Adoption
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What codes are being reviewed?

  • Zoning Code (TCC 20)

– Parking – Landscaping – Impervious surface limits – Building setbacks and lot sizes

  • Subdivisions and Open Space (TCC 18)
  • Clearing and Grading (TCC 14.37)
  • UGA Codes (Lacey, Tumwater, Olympia) (TCC 21, 22, 23)

Also being reviewed, but not by the Planning Commission

  • Drainage Manual (TCC 15.05)
  • Road Standards (TCC 15.04)
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Thurston County http://www.co.thurston.wa.us

2016 Drainage Design and Erosion Control Manual Revision

Mark Maurer, PE, PLA Stormwater Utility Planner

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Thurston County http://www.co.thurston.wa.us

Thurston County Mission

“Creating Solutions for our

Future.”

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Thurston County http://www.co.thurston.wa.us

Goal of this Presentation- Give an overview of the DDECM changes and how it fits into the LID code revision

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Thurston County http://www.co.thurston.wa.us

Water Cycle

Information/photos?

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Thurston County http://www.co.thurston.wa.us

“Traditional” vs. LID

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Thurston County http://www.co.thurston.wa.us

DDECM

What is the DDECM? How do we use it? What is changing with the 2016 revision?

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Thurston County http://www.co.thurston.wa.us

What is the DDECM?

It’s a technical manual that:

  • Establishes minimum requirements for

projects regarding stormwater,

  • Gives guidelines for designing stormwater

systems for treatment and flow control.

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Thurston County http://www.co.thurston.wa.us

How do we use it?

  • County employees use it to

determine if projects are meeting the minimum requirements

  • Developers and designers use it to

know what is required and to correctly design their projects to meet those requirements

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Thurston County http://www.co.thurston.wa.us

What is changing with the 2016 revision?

  • Incorporates new requirements from

the NPDES permit

  • LID is now a requirement
  • Additional LID infeasibility criteria
  • Projects must use a list of LID BMPs or

meet the LID flow control standard

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Thurston County http://www.co.thurston.wa.us

What is changing with the 2016 revision?

  • Flow control standard 50% of the 2

year to the 50 year storm event

  • LID flow control standard 8% of the 2

year to 50% of the two year storm event

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Thurston County http://www.co.thurston.wa.us

LID BMP’s

Bullet Points? Information? Photos?

Rain Garden Porous Pavement Bioretention Area

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Thurston County http://www.co.thurston.wa.us

LID BMP’s

Downspout Infiltration Dispersion Area

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Thurston County http://www.co.thurston.wa.us

Questions?

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Thurston County http://www.co.thurston.wa.us

LID Infeasibility Criteria

  • Mostly follow the site suitability criteria

in the 2009 manual, i.e., set backs from steep slopes, erosive soils, contaminated areas, landfills, high ground water, septic drain fields, etc.

  • LID is infeasible if the initial infiltration

rate is less than 0.30 inches per hour

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Thurston County http://www.co.thurston.wa.us

65/10

  • Full dispersion applies to sites with a

maximum of 10% effective impervious and the water from that area is dispersed through 65% of the site

  • Sites that meet the 65/10 rule do not

trigger the flow control facility req.

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LID Code Update Schedule

  • February – May: Code Review Work Sessions
  • Feb 3: Olympia UGA
  • April: Lacey & Tumwater UGAs
  • May/June: Public Hearing on All Code Changes
  • July: PC Recommendation
  • August: BoCC Public Hearing
  • September-December: BoCC Decision/Adoption
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Questions?

Staff Contact

Allison Osterberg

  • sterba@co.thurston.wa.us

(360) 754-3355 x7011

Project Website

http://www.co.thurston.wa.us/waterresources/lid