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Build Green With LID
- 1. A Builder’s Introduction To Low Impact Development How to Make LID Pencil Out For Your Project
- 18. State Stormwater Regulation Local ordinances must include “Provisions to allow non-structural preventive actions and source reduction approaches such as Low Impact Development Techniques (LID)…Provisions for LID should take into account site conditions, access and long term maintenance.” Department of Ecology Construction Stormwater Permit Municipal Stormwater Permits (Phase I & II) Stormwater Manual (Western & Eastern) Disturbing > acre or < acre if in subdivision Disturbing > acre or < acre if in subdivision “ Guidance” required by constr and muni permits WWHM or MGS Flood to estimate surface runoff and size facilities SWPPP must use BMPs from Manual SWPPP must use BMPs from Manual Phase I: LID mandatory Phase II: locals must allow Addendum to Vol. III provides flow control credits for LID practices
- 21. Types of LID Practices
- 39. Asphalt Sedro-Woolley Photos courtesy of Pete Haase
- 41. Top: Stratford Place, 20-lot LID development in Sultan (2002) Pervious Concrete, Inc., Snohomish WA www.perviouscrete.com Bottom: PercoCrete installation on 15’ road Sammamish www.percocrete.com
- 52. Homeowners need to understand maintenance requirements…
- 55. Questions? Jodi Slavik BIAW 1-800-228-4229
Editor's Notes
- A lot of attention on LID BUT…LID in infancy for developers and builders b/c in many cases it doesn’t pencil out incentives aren’t fully developed local gov’ts still learning about LID many LID practices still being tested, and outside comfort zone for builders.
- For the past 2 decades, the rate of land development across the country has been 2X the rate of population growth (EPA)
- Because of this growth, stormwater management has become the focus of attention
- EXAMPLE: Instead of a treatment pond, the subdivision could have a rain garden in each yard, disconnect downspouts from driveway surfaces, remove curbs, and install grassed swales in common areas.
- CSO = combined sewer overflow storage & conveyance systems Groundwater recharge = instream flows Less expensive to keep water clean than to clean up (treat)
- Pilot project by Sea Pub Utils to redesign entire 660 ft block Apparently Fire Dep’t did not approve
- Meadow on the Hylebos Poor/low infiltrating soils—Pierce Co considered good site to test LID Intensive monitoring; report due fall ’08 Dreamcraft Homes
- Key lessons: GMA is forcing us to develop more marginal sites to accommodate density. But LID becomes more difficult and costly with steep slopes, rolling topography, poor soils, and high water table (which accounts for crawl space flooding). Developer must be on board and part of plat agreement. Developer must set foundation elevations and design utilities for 6” compost tilled and 12” scarified. Amended soil cannot be afterthought. Buyers had expectations and couldn’t necessarily see economic return.
- PSAT created in 1996 to coord & implement env agenda (PS Conservation & Recovery Plan); recent focus on LID; regulation assistance project started in 2005 PSAT no funded/absorbed by PSP; PSP created by Gregoire in 2006 to address health of Puget Sound; 13-yr $12 billion plan issued 12/06; action agenda due September
- Muni permits – 104 cities/17 counties must adopt erosion control ordinances & regulate construction (certain BMPs are required based on impervious surface)
- King County Dedicated “Green Track” for LID projects Free LID consulting services
- Leadership in Energy and Environmental Design – national green building standards (1998—developed by US Green Building Council)
- Pierce Co= “yellow light” for cluster development; “red light” for decreased road widths
- Cell = shallow depression with amended soils & special plants; may or may not have underdrain; not designed as conveyance system Swale = same but are designed as part of a conveyance system (w/gentle side slopes and flow depths less than 12 inches)
- Sand mixture general rule: 60-65% loamy sand mixed with 35-40% compost OR 30% sandy loam/30% coarse sand/40% compost
- Meadow on Hylebos – gardens were finished before construction. Major fine sediment problems. Bioretention areas were still functioning even with extreme fine sediment inputs). Builder & developer have to determine financing, contracting, bonding, and liability. Developer probably willing to come back & finish garden (removing top 6”, other repairs, and planting) if figured into initial land costs.
- 3500 lot size (typical LID) w/1900 sq ft for amended soils = $700
- 1 a) Use soil berm instead of silt fence & then spread berm as organic matter 1 b) Hylebos tried to stockpile but too big; became costly because equipment to spray compost didn’t work & had to wheelbarrow in material (primarily to back yard areas) 2. Flow control for dispersion & have to use amended soils for dispersion, thus indirect credits 3. Heavily amended soils can become saturated = poor plant quality
- 2-day class by PSP/WSU will certify your company
- Pierce Co = “yellow light” for porous pavement in private travel ways
- F & S Grade Rd and Jones Dr just NW of Sedro-Woolley and there are several hundred feet of porous asphalt. Was done by Lakeside Paving and it is several months old and holding up just fine.
- Bunyan power screed place pervious concrete smoothly Most expense in fully cleaning out equipment between regular & pervious concrete—prices will drop when more applicators or new equip available Perco-Crete is a sandy mix verses a 3/8&quot; or Gran stone mix you have seen earlier. All pervious concrete needs to be consolidated. However, Perco-Crete, being made of 'fluffy, slightly moist' sand, must be packed 1/8&quot; for each inch of thickness place.
- Craig Morrison, CMI Homebuilders Started Pervious Concrete Inc in 2002 w/Sultan plat Ran into stormwater issues & suggested to do entirely pervious in order to avoid piping, catch basins & detention
- EcoStone is high density w/aggregate in openings New specs do not require compaction…but no flow credits yet
- Grass & GravelPave – 100% recycled
- Vacuuming may not be as necessary—use rented leaf vac if needed
- Acceptable methods to restore levels of flowability are to vacuum, flush the pervious concrete sections with high volume-low pressure wash or to spray enzymes that digest organic materials on to the pervious concrete sections during wet seasons of the year without excessively low temperature. My counsel has always been to treat it just like any other pavement. Remove leaves and debris from the surface when it accumulates, and DO NOT let people dump topsoil, bark dust, etc. on it. Andrew E. Marks, PE Managing Director Puget Sound Concrete Specification Council &quot;The Concrete Council&quot; [email_address]
- Pierce Co = “yellow light”
- Pierce Co = yellow light
- Discharge has to match pre-developed forested discharge from 50% of 2-yr peak flow to 50-yr peak flow unless prairie or 40% impervious since 1985 (subject to appeal)
- Credits for amended soil?
- Maintenance requirements for property owners should be conveyed with deed