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
  • Retain and protect native topsoil & vegetation where practical
  • Restore disturbed soils by tilling 2-3" of compost into upper 8" of soil
  • Loosen compacted subsoil, if needed, by ripping to 12" depth
  • Mulch landscape beds after planting
Existing Landscapes
  • Till in compost when re-landscaping
  • Mulch beds with organic mulches
  • Topdress turf with compost

On this page:

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
Related tools on this website include:


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:


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:


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 are summarized in Natural Landscaping: Design, Build, Maintain and include:


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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