september 15, 2010 portland’s topsoil for vegetated stormwater facilities henry stevens &...
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September 15, 2010
Portland’s Topsoil for Vegetated Stormwater Facilities
Henry Stevens & Valerie Joachim
Why Does the Specification Matter ?
Green Infrastructure Green Streets
September 2010
900 Public and Private Facilities Constructed in the Right-of-Way
Standard Expectations
• Infiltration. Design assumption: 2”/hr
• Retention. Maximize field capacity
• Pollutants Management. Support immobilization & biological degradation of pollutants
• Substrate for Plants. Provide good growing conditions, in part to minimize maintenance
• Longevity. Continue to perform in the long term
• Available. Be simple to make, not expensive
Fines Content
WSU Research. Bench testing showed that even small amounts of clay and silt can lead to clogging.
Local History with Higher Fines Soils. There had been just a few problems in facilities with higher fines.
COP Bias Toward “Real Soil”. Staff were very concerned about the negative aspects of blends with super-low fines.
Compost Content
• WSU Research. Confirmed that compost is functionally valuable in a number of ways
• WA State Endorsement of Bioretention Soil Based on compost CEC at 40% by volume
• Supplies. Portland has a healthy existing market for supplies of USCC compost made from plant-derived material (yard cuttings)
• Potential Export of Nutrients. The City is tracking this issue (for flow-through systems)
Testing
• Complexity and Cost. The goal was to start with simple testing requirements and only increase complexity as needed.
• Frequency. The Bureau concluded it would be too burdensome to require new tests for each project or load of material
• Reasons for Keeping it Simple
Many soil vendors and builders are smaller operators with no history of testing and paperwork for soil.
The goal is to interest as many vendors as possible
The Specification: The Mix
• Specification Title. SSP 1040.14.(d) Stormwater Facility Topsoil: Standard Blend
• Application. For all vegetated facilities except extreme compaction scenarios (Infiltration Blend for the Right-of-Way = Seattle Blend).
• Basic Composition. Any blend of loamy soil, sand, and compost that is 30-40% compost (by volume) and meets the other criteria
The Specification: GradationGradation Analysis. The particle gradation analysis must
conform with ASTM C117/C136 (AASHTO T11/T27). The analysis shall include the following sieve sizes: 1 inch, 3/8 inch, #4, #10, #20, #40, #60, #100, #200.
Particle Sieves and % Passing Ranges1 inch 100 # 4 75 -100 # 10 40-100 # 40 15-50 # 100 5-25 # 200 5-15
Frequency. The analysis can be no older than 90 days at submittal
The Specification: Gradation
• Coefficient of Uniformity (Cu*). The blend must have a Coefficient of Uniformity equal to or greater than 6 to ensure it is well graded (has a broad range of particle sizes).
* Cu = Particle size at 60% Passing/Particle size at 10% passing
The Specification: Compost
• The material must be plant-derived (no manure). It’s often sold as “garden mulch”.
• The vendor must be a participant in the US Composting Council Seal of Testing Assurance Program (USCC STA).
• The compost is not “certified” ! (Check the results against the specification.)
• STA members always have a current report
The Specification: Installation
• Protect the soil from contaminants
• Place in 8 inch lifts, compacted with roller
• Install plants ASAP after soil placement
• Temporary erosion control measures
• Fence the new facility to avoid compaction
• Placement not allowed in wet conditions
Testing and Monitoring
General Comments• The specifications have resulted in fewer
installations with inadequate infiltration rates
• There are still questions about whether some installations drain too quickly
• Most vendors are out of compliance with the specification at some point (buyer beware !)
• The Bureau will continue to monitor performance as the latest generation of facilities ages.
• The Bureau may develop a separate specification for planters with rock layers.
Stormwater Facility Topsoil Vendor Program
Valerie JoachimEngineering Services Support Analyst
Bureau of Environmental ServicesSoil Vendor Contact & Vendor List Administrator
Where Henry left off….Where Henry left off….
• Did we spec something readily available in Did we spec something readily available in the local market?the local market?
• No central point of contact within BESNo central point of contact within BES
• Product supply issues & same day noticeProduct supply issues & same day notice
• Future needs: Citywide Green Street Future needs: Citywide Green Street program, on-going rehab and private program, on-going rehab and private development-driven projects.development-driven projects.
• Year-round Year-round constructionconstruction
Meet the Vendors
• Area vendors invited to City officesArea vendors invited to City offices• 5-year estimate = 10,000 CY on BES projects 5-year estimate = 10,000 CY on BES projects
alonealone• Intro to specification & submittal requirementsIntro to specification & submittal requirements• Discussion of required testing & paperworkDiscussion of required testing & paperwork• Need to be pro-active versus reactiveNeed to be pro-active versus reactive• Haulers interested too. Began to align Haulers interested too. Began to align
themselves with vendors & sell a complete themselves with vendors & sell a complete serviceservice
Submittal PaperworkSubmittal PaperworkOverall pH 3-way blendParticle Size Analysis
(per ASTHO T11/T27 or ASTM C117/C136 tests)
USCC Technical Data Sheet for compost
Two 5-gallon buckets, if directed by Owner’s Rep.
Paperwork should be no more than 90-days old from time of submittal.
Vendor List
•What it is & isn’t
•Updated monthly
•On the internet
•Ask for the right topsoil product!
Lessons LearnedLessons Learned• Central point of contact is essential for the
success of our program.
• Annual ‘refresher’ training for staff is essential.
• Continue to actively cultivate new vendors, while other vendors may fall out of the program.
• Others are piggy-backing on the SWMM Green Street details & soil construction specification. Expect the market to grow.
• Careful use of vendor list advised.
• Blending, conveyance, handling and compacting methods are key to success of soil performance.
• The soil spec is just one component in ensuring the success of a facility.
Looking ForwardLooking Forward• We are still learning about the topsoil blend.We are still learning about the topsoil blend.
• Are there common Best Practices for Are there common Best Practices for conveyance, installation, and compaction?conveyance, installation, and compaction?
• Keep the management of the soil spec & vendor Keep the management of the soil spec & vendor list as simple as possible.list as simple as possible.
• Continue to cultivate new vendors / sustain Continue to cultivate new vendors / sustain existing relationshipsexisting relationships
• Opportunities to expand training to other bureaus Opportunities to expand training to other bureaus within the City / other interested partners within the City / other interested partners
References:References:
2010 City of Portland2010 City of Portland Standard Construction Specifications
01040.14 & .43 “Stormwater Facility Topsoil”00415 “Vegetated Stormwater Facilities”
2008 City of Portland2008 City of Portland – Stormwater Management Manual– Stormwater Management Manual
Appendix F3 Stormwater Topsoil Vendor ListAppendix G3 Green Street ‘Typical Details’ (Revised Feb. 2010)
City of Portland – Office of TransportationCity of Portland – Office of Transportation
“Standards for Construction - Construction Documents” page (Website also houses stormwater topsoil vendor list)
Contact Info:Contact Info:
Henry StevensHenry Stevens – [email protected] of Portland / Bureau of Environmental Services1120 SW 5th Avenue, # 1000, Portland, OR 97204503.823.7863
Valerie JoachimValerie Joachim – [email protected] of Portland / Bureau of Environmental Services1120 SW 5th Avenue, #1100, Portland, OR 97204503.823.5564