Practical Soil Protection & Restoration 9/27/11 The Science and Practice of Sustainable Sites: Why a Soil Standard? – Multiple Benefits Practical Implementation of Environmental/sustainability benefits • Protect/restore stormwater infiltration Soil Protection & Restoration • Bio-filtration of urban pollutants – protect waterways • Protect existing vegetation , improve tree & plant growth • Reusing organic “wastes” to restore soil function • Reduced irrigation use, less need for fertilizers & pesticides Value to builder/contractor • Quicker planting in prepped soil • Less plant loss = fewer callbacks David McDonald – Seattle Public Utilities • Better appearance sells next job Howard Stenn – Stenn Design Jim Berger – Port Blakely Communities Value to property owner • Better plant health & appearance 9/27/2011 seminar sponsored by the WA Chapter of the American Society of • Lower water bills Landscape Architects, UW Botanic Gardens, • Reduced chemical needs 1 2 and Seattle Public Utilities • Lower maintenance costs Sustainable Sites Initiative WA State “Post Construction (SITES™) Rating System Soil Quality & Depth” BMP Summary of Soil Best Management Practices • Prereq. 1.1 Protect farmland soils in Dept. of Ecology Stormwater New Construction • Credit 1.5 Select brown/grey-fields Manual; coming into local codes Retain and protect native topsoil & vegetation (esp. trees!) • Prereq. 2.1 Conduct pre-design • Soil management plan showing site assessment (incl. soil) areas to be protected, or • Choose sites to conserve good quality existing veg. & soil • Prereq. 2. 2 Use integrated site disturbed & restored, and • Minimize construction footprint development process soil/compost/mulch import • Establish veg. & soil protection zones - fence & protect • Credit 4.4 Minimize soil amounts for each area disturbance (minimize grading) • Keep all impacts off protected • Store and reuse topsoil from site • Prereq. 4.3 Create a Soil veg. & soil areas • Retain “buffer” vegetation along waterways Management Plan • Prereq. 7.2 Restore soils • Restore disturbed areas by Restore disturbed soils by tilling 2-4" of compost disturbed during construction amending with compost, into upper 8-12" of soil. Ripppy to loosen compacted layers. • Credit 7.3 Restore soils disturbed stoc kp iling & reus ing topso il, or by previous development importing amended soil. Existing Landscapes • Prereq. 8.1 Plan for sustainable site Scarify subsoil, for 12” uncompacted depth. • Retrofit soils with tilled-in compost when re-landscaping maintenance • Mulch beds with organic mulches (leaves, wood chips, • Credit 8.3 Recycle organic matter • Mulch, and Maintain to replenish organic content. compost), topdress turf with compost, and mulch-mow to in operations & maintenance 3 4 www.sustainablesites.org www.buildingsoil.org maintain organic content that supports soil ecosystem. 1 Practical Soil Protection & Restoration 9/27/11 Understanding Soil: Sub-Soils in the Puget Sound Basin: development from parent “dirt” & rock Leftovers from glaciers & volcanoes glacial till: unsorted, unstratified mixtures of clay, silt, sand, Soil horizons & their evolution gravel, and boulders; deposited under ice, or in moraines hardpan: till compacted under glacier • Substratum (C) or bedrock (R) outwash soils: layers sorted by particle weathers physically & size by water - sand / gravel / rocks chemically to subsoil (B) lake/marine bed soils: clay or silt that settled out in lakes & estuaries • Primarilyygp biological processes create topsoil (A) volcanic ash: light, fertile, holds moisture - and organic (O) horizons mostly blown east of Cascades mudflows: mixed size, compact - like till Learn about Puget Sound soils at: USDA - NRCS 5 6 http://soils.usda.gov www.puyallup.wsu.edu/soilmgmt/Soils.htm Glacial till Glacial outwash • May be piled, uncompressed • May be sorted boulders, gravel and unsorted, in moraines at • …sand and fines ….. edge or terminus of glacier •Or a mix! • Basal till from under the glacier (1/2 mile of ice over Seattle!) has been compressed into hardpan • Good for foundations, but low permeability and hard for roots to penetrate 7 8 2 Practical Soil Protection & Restoration 9/27/11 Volcanic ash Lake beds, or mudflows lenses, and layers • Tephra (ash) – light, fertile, holds moisture, erodable • Silts and clays settle out… • And then may be overlain in • Mudflow – compact, mixed fines and boulders, low lenses with sand or gravel from permeability, looks and acts like basal till, but more fertile succeeding outwash • Grey-yellow color when saturated and anaerobic • Great for farming, (best nutrient capacity) but unstable in slopes or foundations! 9 10 Layers upon layers… Alluvial soils ignore them at your peril! • Sandy outwash over • Flat, loamy deposits compacted basa l t ill h ard pan in river floodplains (or ancient rivers) • Thin soil over bedrock • Clay lenses over hardpan, • Best for farming, or inter-layered with sand often wasted on (unstable!) development because they’re flat 11 12 3 Practical Soil Protection & Restoration 9/27/11 Disturbed soils in urban areas Soil Texture = mineral particle size (sand and finer particles) Ribbon + feel test: • TillTopsoil layer removed Mo isten so il, ro ll b etween • Compaction hands, then squeeze • Subsoil (or worse) fill out with thumb layers. • Debris or toxins? – Sand: no ribbon, grainy – Sandy loam: ½ inch ribbon – Loam: thick 1 inch ribbon – Silt: makes flakes rather than ribbon – Silty clay loam: thin, breaks easily, floury feel – Sandy clay loam: stronger, grainy 13 – Clay: long (3 inch) ribbon, smooth feel 14 Understanding soil: Understanding Soil Biology texture, structure, & pore space (thus infiltration) Soil life provides essential functions Soil components: • “The Dirt” (mineral part) Good soil is about - half mineral –sand - half space (air & water) Soil – silt - plus a smaller but is –clay essential amount of alive! organic matter & soil life • Air and Water “Loam” is a mix of • Organic Matter sand, silt, clay and organic, USDA-NRCS formed over time by nature and Soil Life “Soil Biology Primer” 15 16 (create aggregates & pores) S. Rose & E.T. Elliott http://soils.usda.gov/sqi/ 4 Practical Soil Protection & Restoration 9/27/11 Common organisms in the soil foodweb Restoring soil life, to restore soil functions • Nematodes Soil organisms create: • Bacteria • soil structure • fertility = nutrient cycling • plant disease protection Soil Foodweb Inc. • Fungi Paul R. August, University of Minn. • Arthropods • biofiltration • erosion control Soil Foodw • stormwater detention e b Inc. SSSSSSA ••ProtozoaProtozoa ••EarthwormsEarthworms Compost kickstarts the soil ecosystem! Wilhelm Foissner, 17 (Provides food and home for organisms)18 University of Salzburg How does soil life create soil structure? How does soil life provide fertility (nutrient cycling)? • Bacteria secretions glue clays, silts and sands together into micro-aggregates. • Soil foodweb stores nutrients in living & dead organic matter • Micro-aggregatbdtes are bound • Nutrients are released in root zone as organisms eat and together by fungal hyphae, excrete “waste” (nitrogen, etc.) root hairs and roots. • Mycorrhizal fungi bring nutrients • Spaces are made by moving and water to roots of plants arthropods & earthworms, and decaying roots. • Only when all organisms are present can roots and water move into the soil with ease. 19 20 S. Rose & E.T. Elliott Dr. Michael P. Amaranthus, Mycorrhizal Applications Inc. 5 Practical Soil Protection & Restoration 9/27/11 How does soil life provide plant disease protection? How does soil life filter out urban pollutants? Diversity predation, parasitization & competition with the few disease-causing organisms • Creates structure • Bacteria cover leaf surfaces, block infection • Breaks down hydrocarbons, pesticides • Converts fertilizers to stable forms, so they are • Ecto- and endo- available to plants but mycorrhizae won’t wash away prevent root Soil Foodweb Inc. infection • Binds heavy metals iilhd’in soil, so they don’t • Many organisms wash into streams prey on the few disease-causing organisms 21 22 SSSA How does soil life How does soil life provide stormwater control erosion? detention / infiltration? • Creates pore spaces, • Builds soil structure, increases infiltration moisture-holding capacity • Sticks soil particles & aggregates together • Increases surface with bacterial slime, fungal hyphae, porosity & root hairs (bigger aggregates are UW trials, turf on glacial till soil harder to move) “aggregate stability” Compost- amended • Promotes rapid plant growth till soil – & deep root development up to 50% reduction in storm water runoff 23 24 6 Practical Soil Protection & Restoration 9/27/11 How can we enhance & restore soil biodiversity, Site selection & planning to protect good soils to improve plant growth, water quality, and • Select previously disturbed sites instead of greenfields. reduce runoff? • Infill to enhance communities, connect with transit. • Protect existing soil & vegetation where possible • Start early to identify site values, and locate development on site to maximize protection of best soils , trees, habitat , • Prevent /reduce compaction natural drainage, etc. Involve arborists, soil & habitat (keep heavy machinery off) experts. Sell these values to developers/ decision makers. • Reduce intensive use of • Plan to minimize grading, soil export/import. pesticides & soluble fertilizers • Incorporate compost into soil to feed soil life organic matter + soil organisms + time creates soil structure,