Module 6.2 Advanced Soil Protection & Compost
Amended Soils – DMcDonald 5-4-2017.pptx
SOILS
ADVANCED TOPICS IN LID DESIGN:
Soil Protection and Compost-Amended Soils
Learning Objective:
Know the options for meeting BMP T5.13 Post-Construction Soil Quality and Depth,
strategies for determining site soil conditions, and how to develop a soil management plan.
David McDonald,
Seattle Public Utilities
6.2
Module 6.2 Advanced Soil Protection & Compost
Amended Soils – DMcDonald 5-4-2017.pptx
SOILS
Introduction
Determining Site Soil Conditions
Soil Protection
Soil Amendment
Developing a Soil Management Plan
– Requirements & guidance
– How soil manages runoff & water quality
Module 6.2 Advanced Soil Protection & Compost
Amended Soils – DMcDonald 5-4-2017.pptx
BMP T5.13 (in Ecology Stormwater Manual, vol. V)
Post-Construction Soil Quality and Depth
• Retain native soil and duff wherever possible –
protect from construction disturbance, compaction etc.
• All areas cleared and graded require 8 inch soil depth:
• Organic matter content 10% dry weight (5% for turf areas)
• Use native topsoil, amend existing soil with compost,
or import topsoil blend
• Subsoil scarified 4 inches below 8-inch topsoil layer (12” total)
• Protect amended soil from compaction
• Mulch after planting
• Maintenance practices to replenish organic content
Required on all sites in Western WA.
Recommended in Eastern WA.
Module 6.2 Advanced Soil Protection & Compost
Amended Soils – DMcDonald 5-4-2017.pptx
SOILS
BMP T5.13: Runoff Model Representation
• Areas meeting the design guidelines may be entered into
approved runoff models as “Pasture” rather than “Lawn.”
• Flow reduction credits can be taken in runoff modeling when
BMP T5.13 is used as part of a dispersion design under the
conditions described in:
• BMP T5.10B Downspout Dispersion
• BMP T5.11 Concentrated Flow Dispersion
• BMP T5.12 Sheet Flow Dispersion
• BMP T5.18 Reverse Slope Sidewalks
• BMP T5.30 Full Dispersion
(for public road projects)
Module 6.2 Advanced Soil Protection & Compost
Amended Soils – DMcDonald 5-4-2017.pptx
SOILS
BMP T5.13 design guidance:
2012 LID Manual for Puget Sound
• 2.4 Soil Protection Areas
• 4.1 Vegetation and Soil Protection
• 5.2 Techniques to Minimize Site
Disturbance
• 6.2 Amending Construction Site Soils
Similar guidance in
Eastern WA LID Manual:
– Chapter 4, BMP 4.2
Amending Construction Site Soils
Module 6.2 Advanced Soil Protection & Compost
Amended Soils – DMcDonald 5-4-2017.pptx
BMP T5.13 design guidance:
Ecology-approved Building Soil manual
• Source of LID Manual content
• Manual developed regionally with experts
• Develop a “Soil Management Plan” for each site
• Four options for soil management (can use 1 or more per site):
1) Retain undisturbed native soil & vegetation, protect from compaction
2) Amend existing soil in place with compost
3) Stockpile topsoil prior to grading, and reuse on site (amend if needed)
4) Import topsoil meeting organic matter content requirements
• Choose pre-approved or custom calculated amendment rates
• Simple field inspection and verification procedures
Available www.soilsforsalmon.org or www.buildingsoil.org
Module 6.2 Advanced Soil Protection & Compost
Amended Soils – DMcDonald 5-4-2017.pptx
Development typically
degrades soil functions.
How can we make this
Function more
like this?
Native forest
After development
Module 6.2 Advanced Soil Protection & Compost
Amended Soils – DMcDonald 5-4-2017.pptx
BMP T5.13 asks:
How can we protect or restore soil functions on every site?
Module 6.2 Advanced Soil Protection & Compost
Amended Soils – DMcDonald 5-4-2017.pptx
SOILS
Restoring soil life, to restore soil functions
Soil organisms create:
• soil structure
• fertility = nutrient cycling
• plant disease protection
• biofiltration
• erosion control
• stormwater detention
Compost kick-starts the soil ecosystem.
(Provides food and home for organisms)
Module 6.2 Advanced Soil Protection & Compost
Amended Soils – DMcDonald 5-4-2017.pptx
SOILS
• Bacteria secretions glue clays, silts and
sands together into micro-aggregates.
• Micro-aggregates are bound
together by fungal hyphae,
root hairs and roots.
• Spaces are made by moving
arthropods & earthworms,
and decaying roots.
• Only when all organisms
are present can roots and
water move into the soil
with ease.
How does soil life create soil structure?
S. Rose & E.T. Elliott
Good soil is about
– half mineral
– half space (air & water)
– plus a smaller but
essential amount of
organic matter &
soil life
Module 6.2 Advanced Soil Protection & Compost
Amended Soils – DMcDonald 5-4-2017.pptx
How does soil life provide fertility (nutrient cycling)?
• Soil foodweb stores nutrients in living & dead organic matter
• Nutrients are released in root zone as organisms eat and
excrete “waste” (nitrogen, etc.)
• Mycorrhizal fungi bring nutrients
and water to roots of plants
Dr. Michael P. Amaranthus, Mycorrhizal Applications Inc.
Module 6.2 Advanced Soil Protection & Compost
Amended Soils – DMcDonald 5-4-2017.pptx
How does soil life provide plant disease protection?
Diversity predation, parasitization & competition
with the few disease-causing organisms
• Bacteria cover leaf surfaces, block infection
• Ecto- and endo-
mycorrhizae
prevent root
infection
• Many organisms
prey on the few
disease-causing
organisms
SSSA
Soil Foodweb Inc.
Module 6.2 Advanced Soil Protection & Compost
Amended Soils – DMcDonald 5-4-2017.pptx
SOILS
How does soil life filter & remove pollutants?
• Creates soil structure
• Breaks down hydrocarbons, pesticides, etc.
• Converts fertilizers/nutrients to stable forms, so they are
available to plants but won’t wash away
• Increases cation exchange capacity,
binding nutrients & other ions
• Binds metals in soil, so they
don’t wash into streams
• Creates “dissolved organic carbon”
(DOC) complexes, which sequester
metals & other pollutants in water,
reducing toxicity.
Module 6.2 Advanced Soil Protection & Compost
Amended Soils – DMcDonald 5-4-2017.pptx
SOILS
WsDOT: Compost Amended Vegetated Filter Strip
– 2004 pollutant & flow reduction trials along I-5
These 3 slides courtesy of:
Mark Maurer, WSDOT
[email protected]
Module 6.2 Advanced Soil Protection & Compost
Amended Soils – DMcDonald 5-4-2017.pptx
Module 6.2 Advanced Soil Protection & Compost
Amended Soils – DMcDonald 5-4-2017.pptx
SOILS
TDS=Total Dissolved Solids, COD=Chemical Oxygen Demand, TSS=Total Suspended Solids
“first flush” – first winter’s rain events
WsDOT 2004:
10 ft. wide compost-amended strip
treats stormwater from 2 lanes
Module 6.2 Advanced Soil Protection & Compost
Amended Soils – DMcDonald 5-4-2017.pptx
Cation exchange capacity = binding sites
The smaller the particle the greater the CEC,
but organic complexes multiply binding sites.
Humus/clay colloids have the most!
Sand
Silt
Clay
Cation Exchange Capacity (CEC) for soil mixes
Low fertility soil
Less than 5 meq+/100g
Medium fertility
5-10
High fertility
10-30
Compost/humus
up to 200!
Relative surface area
Module 6.2 Advanced Soil Protection & Compost
Amended Soils – DMcDonald 5-4-2017.pptx
SOILS
Organic-amended soil removes pollutants and
binds remainder to Dissolved Organic Carbon (DOC)
Soil removes most toxics,
adds dissolved organic
complexes that bind
remaining metals,
nutrients, PAH’s and
other pollutants.
DOC-bound pollutants are
much less toxic to aquatic
organisms.
Fig. 4 Survival of three test organisms exposed to control water, untreated September
2012 runoff, runoff treated with bioretention without plants (No Plants), and runoff
treated with bioretention with plants (Plants). Asterisks indicate survival significantly lower
than control. Error bars are ± one standard error of the mean.
Soil bioretention protects juvenile salmon and their prey from the toxic
impacts of urban stormwater runoff
J.K. McIntyre , J.W. Davis , C. Hinman , K.H. Macneale , B.F. Anulacion , N.L. Scholz , J.D.
Stark; Chemosphere, 2015 http://dx.doi.org/10.1016/j.chemosphere.2014.12.052
http://www.sciencedirect.com/science/article/pii/S0045653514014805
juvenile coho salmon
Highway runoff filtered
through bioretention soil mix:
60% sand: 15% compost: 15%
shredded bark: 10% water
treatment residuals
Highway runoff:
lethal to
daphnia and
juvenile salmon
daphnia
mayfly
dechlorinated
drinking water
“DOC” is the fraction of water-borne organics
that pass through a 0.45 μm filter
Module 6.2 Advanced Soil Protection & Compost
Amended Soils – DMcDonald 5-4-2017.pptx
SOILS
How does soil life
control erosion?
• Creates pore spaces,
increases infiltration
• Sticks soil particles & aggregates together
with bacterial slime, fungal hyphae,
& root hairs (bigger aggregates are
harder to move)
“aggregate stability”
• Promotes rapid plant growth
& deep root development
Module 6.2 Advanced Soil Protection & Compost
Amended Soils – DMcDonald 5-4-2017.pptx
SOILS
How does soil life provide stormwater detention
and infiltration?
• Builds soil structure, pores, &
moisture-holding capacity
• Increases surface porosity
• Modifies underlying sub-soils
UW trials, turf on glacial till soil
Compost-
amended
till soil –
over 50%
reduction in
storm water
runoff
Learn more:
USDA-NRCS Soil Biology Primer
http://soils.usda.gov/sqi/
Module 6.2 Advanced Soil Protection & Compost
Amended Soils – DMcDonald 5-4-2017.pptx
SOILS
How can we enhance & restore soil biodiversity,
to improve plant growth, water quality, and
reduce runoff?
• Prevent /correct compaction
• Reduce use of pesticides
& soluble fertilizers
• Incorporate compost into soil
to feed soil life
organic matter + soil organisms + time
creates 
soil structure, biofiltration, fertility, & stormwater detention
Module 6.2 Advanced Soil Protection & Compost
Amended Soils – DMcDonald 5-4-2017.pptx
SOILS
Soil Amendment: A cost-effective solution
for new development
• Much better plant survival
= fewer callbacks
• Easier
planting
• Can cut irrigation needs by 50%
= 3-7 year payback on
irrigation savings alone
Module 6.2 Advanced Soil Protection & Compost
Amended Soils – DMcDonald 5-4-2017.pptx
SOILS
Improving & maintaining soil
functions in existing development
• Amend soil when re-landscaping
• Plant native trees & shrubs,
especially near waterways
• Mulch beds annually with
leaves, chips, compost, etc.
• Mulch-mow (leave clippings) &
top-dress turf areas with compost
Module 6.2 Advanced Soil Protection & Compost
Amended Soils – DMcDonald 5-4-2017.pptx
SOILS
Determining Site Soil Conditions
USDA Soil Surveys: a good starting
point, but use with caution!
Compare site soil to the existing
USDA survey description.
Changes since development:
• Consistency with existing conditions
• Graded and compacted conditions
• Imported soils
http://websoilsurvey.nrcs.usda.gov/app/
Module 6.2 Advanced Soil Protection & Compost
Amended Soils – DMcDonald 5-4-2017.pptx
Washington soils: leftovers from
glaciers, floods, & volcanoes
glacial till: unsorted, unstratified mixtures of clay, silt, sand,
gravel, and boulders; deposited under ice, or in moraines
hardpan: till compacted under glacier
outwash soils: layers sorted by particle
size by water – sand / gravel / rocks
lake/marine bed soils: clay or silt that
settled out in lakes & estuaries
volcanic ash: light, fertile, holds moisture –
mostly blown east of Cascades
mudflows: mixed size, compact – like till
Learn about Washington soils at:
www.puyallup.wsu.edu/soilmgmt/Soils.htm
Module 6.2 Advanced Soil Protection & Compost
Amended Soils – DMcDonald 5-4-2017.pptx
Limitations of traditional soil analysis methods
for disturbed urban soils
• Soils vary across site:
fill? native? subsoil?
• Mixed or missing horizons –
topsoil layer often removed
• Sharp interface problems
(between native and fill soils)
• Compaction
• Low ph, anaerobic?
• Low organic matter
• Debris, toxins?
Module 6.2 Advanced Soil Protection & Compost
Amended Soils – DMcDonald 5-4-2017.pptx
Read existing
topography
Soil tests:
• Organic Matter
• Bulk Density
• Nutrients
• Texture (% sand/silt/clay)
• Contaminants (if suspected)
Old maps and photos
Project
soil
borings
Regional geologic maps
Interviews
Soil information sources
Module 6.2 Advanced Soil Protection & Compost
Amended Soils – DMcDonald 5-4-2017.pptx
Creating a soil profile with a Dutch
auger
Changes in soil type
Module 6.2 Advanced Soil Protection & Compost
Amended Soils – DMcDonald 5-4-2017.pptx
Compile information on a site soil survey map
• Record different soil types, test results, and issues
• Identify potential soil & vegetation protection zones
Module 6.2 Advanced Soil Protection & Compost
Amended Soils – DMcDonald 5-4-2017.pptx
SOILS
Developing A Soil Management Plan (SMP)
• A scale-drawing identifying
areas where each soil treatment
option will be applied.
• A completed SMP form
identifying treatment options,
amendment products and
calculated application rates for
each area.
• Copies of laboratory analyses for
compost and topsoil products to
be used, with OM content and
C:N
Module 6.2 Advanced Soil Protection & Compost
Amended Soils – DMcDonald 5-4-2017.pptx
1: Review Landscape and Grading Plans
Working with plans, check the soil in each area to assess how grading will impact
soil conditions and potential for reuse of topsoil excavated from building
foundations, stormwater detention facilities, and planned pavement areas.
Identify potential
vegetation and soil
protection zones –
If you don’t mess it
up, you don’t have
to fix it!
Module 6.2 Advanced Soil Protection & Compost
Amended Soils – DMcDonald 5-4-2017.pptx
SOILS
2. Identify Areas Suitable for Each Option
• Established “native” plants and duff– to be left undisturbed.
• Areas to be protected from compaction during construction.
• Areas to be cleared of native vegetation but not graded –
may be amended at reduced rate.
• Excavated or graded topsoil suitable for stockpiling and
reuse on site.
• Compacted layers less than
12 inches deep (after grading) –
require scarification or soil import.
• Existing organic content in soil to
be retained or stockpiled and
reapplied – reduced amendment rate.
Module 6.2 Advanced Soil Protection & Compost
Amended Soils – DMcDonald 5-4-2017.pptx
Soil Treatment Options
Amendment Rate Options
Option 1. Retain undisturbed native
vegetation and soil, and protect from
compaction during construction.
Option 2. Amend existing soil at pre-
approved or custom calculated rates based
on soil and amendment tests.
Option 3. Import topsoil mix of sufficient
organic content and depth.
Option 4. Stockpile native topsoil during
grading, and reapply after construction.
(import soil if needed to achieve depth).
Amend stockpiled soil if needed to meet
5% O.M. (turf) or 10% (planting beds)
Pre-approved Amendment Rate
Turf: Mix 1.75” compost in to 8” depth
(5% OM by loss-on-ignition test)
Beds: Mix 3” compost in to 8” depth
(10% OM by loss-on-ignition test)
Custom-Calculated Rate
Test soil and amendment for organic
content and bulk density, to determine
amendment rate needed to achieve 5 or
10% organic content
Module 6.2 Advanced…