How To: Soil Best Management Practices,
Tools, & Specifications
Soil best management practices (BMPs) include preserving native soil, and restoring soils disturbed during development with organic amendments like compost. This reduces stormwater runoff and pollution, reduces landscape maintenance needs for water, fertilizer, and pesticides, and makes healthier, more attractive landscapes.
Soil Best Practices:New Construction
On this page:
- Washington State’s Soil BMPs for New Construction: How-to Guide and Specifications
- Low Impact Development
- Local Soil Regulations Around Washington
- Erosion Control with Compost Berms, Blankets, and Socks
- Improving the Soil in Existing Landscapes
- Information for Homeowners
Washington State’s Soil BMPs for New Construction:
How-to Guide, Specs, and “Low Impact Development”
Soil BMPs are simple – see the Summary at right.
Or view a slideshow: Building Soil: Foundation for Success (PDF 37 slides, 4.8 MB)
Washington State now requires Soil BMPs in new construction. Washington State Department of Ecology’s Stormwater Management Manual for Western Washington (WDOE website), used by local jurisdictions for stormwater design, requires soil protection or restoration (Volume V, Chapter 5, BMP T5.13). Read that what it requires in this excerpt, BMP T5.13, Post-Construction Soil Quality and Depth (PDF) Flow credits in stormwater modeling for use of the soil BMP are shown at the end of that PDF.
A practical Guide to implementing these soil BMPs has been developed by experts in soil, landscapes, construction, and permitting. It is intended as a practical aid to builders, landscape contractors, and local jurisdictions.
Download the Guide:
BUILDING SOIL: Guidelines and Resources for Implementing Soil Quality and Depth BMP T5.13 in WDOE Stormwater Management Manual for Western Washington (PDF, 44 pages, 2.5 MB) includes these sections:
- Role of soil quality in stormwater management
- Summary of BMP T5.13, and related BMPs in the State Stormwater Manual
- Soil preservation and amendment options, and calculations
- How to develop a simple “Soil Management Plan”
- Field guide to verifying soil quality and depth (PDF) – a practical inspection guide
- Compost suppliers and soil testing labs
- Model soil specifications, in APWA and CSI formats
- Compost Amendment Rate, Amount, and Cost Calculator (Excel spreadsheet, based on formula in the Guide)
- The soil specs from the Guide in APWA or CSI format (in MS Word for cut and paste into design documents)
- Blank forms (in MS Word for easy editing) for the Soil Management Plan or Field Verification Form.
Low Impact Development
Low Impact Development is a term used to describe all the strategies for managing stormwater in a dispersed, on-site fashion, rather than relying on expensive collection, detention, and treatment facilities. Soil best practices and natural area protection are the first steps in LID, which also includes techniques such as bioretention swales, “raingardens”, permeable paving, green roofs, and a watershed-wide planning to slow and infiltrate runoff.The best local resources for LID (which also include information on soil best practices) are:
- Low Impact Development Technical Guidance Manual for Puget Sound (2012 update) with design guidance for all the BMPs in the WA State Stormwater Manual
- Seattle’s Green Stormwater Infrastructure, Natural Drainage Systems, and RainWise website
- Washington Stormwater Center with resources from UW and WSU's LID research program
- Stormwater Design Seminars
Local Soil Regulations Around Washington
Local governments in Western Washington are required to adopt stormwater codes that comply with the State Manual over the next few years. The Guide above will help them implement practical Soil BMP permitting and inspection methods. Many local governments have already adopted soil best practice regulations, or developed local information for builders, including:
- King County's Post Construction Soil Standard, in effect since January 2005 -- this website includes:
- A how-to video
- Achieving the Post-Construction Soil Standard (PDF)
- Compost and Topsoil Calculator for the King County standard
- City of Seattle's Stormwater Manuals, see Volume 3 Project Stormwater Control, chapter 5.1 Soil Amendment BMP, and
- Client guide to Post Construction Soil Management (PDF) and
- Green Stormwater Infrastructure resources for designers, builders, and homeowners
- Other cities around Western Washington have also recently updated their codes to require soil best practices - check with your local jurisdiction. This list will be updated periodically. Please contact WORC (email at bottom of page) if you have information to add.
Erosion Control with Compost Berms, Blankets, and Socks
Compost also is proving to be very effective in erosion control during and after construction, covering slopes (compost blankets)
or in place of silt fence (compost berms or compost-filled filter socks).
The best resource is the US EPA’s Construction Site Erosion Control website – look down that page for specifications on compost blankets, berms, and socks.
Improving the Soil in Existing Landscapes
Soil organic matter is replenished in Nature by leaf fall and decaying plants. This feeds the soil ecosystem,
maintaining and building soil functions over the centuries.
Soils need feeding in our landscapes too. Simple methods include:
- Amend beds with compost when re-landscaping.
- Annual mulching of existing landscape beds with shredded leaves, woodchips, bark, or compost. This builds the soil, prevents weeds, keeps plant roots warmer in winter and cooler in summer, and can cut summer irrigation needs by 50%!
- On lawns, mulch-mowing or “grasscycling” – leaving the clippings to feed the soil, reduce fertilizer needs, and build lawn health. See Ecologically Sound Lawn Care for the Pacific Northwest: findings from the scientific literature and recommendations from turf professionals (PDF, on City of Seattle website)
- Top-dress with compost to improve poor lawns, ¼ to ½ inch of compost raked in after aeration in spring or fall. See lawn manual above, and also Using Composts to Improve Turfgrass Performance (on Penn State University website)
- Avoid overuse of soluble fertilizers and pesticides which can damage beneficial soil life.
Information for Homeowners
Build it and they will come – the simple practices for existing landscapes described above are just as useful at home, for building organic matter to restore beneficial soil organisms. Benefits include healthier plants and lawns, fewer weeds, less need for chemicals, and lower summer water bills. Some good brochures for homeowners on all this include:
- Natural Yard Care guides available in English and Spanish, along with Growing Healthy Soil, Composting, Natural Pest Control, Food Gardening, and other Natural Lawn and Garden Care guides (on City of Seattle website).
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