roadside rain garden’s: wrong and how we recovered...– gsi o&m manual; defined levels of...
TRANSCRIPT
ASCE LID ConferenceSeptember 27, 2011
Ballard Roadside Rain Garden’s: What Went Wrong and How we Recovered
Overview
Typical Basins by Land Use
45%
4%8%
10%
12%
21%
Single Family Residential
MultiFamily
Commercial/Industrial
Other Developable
Open Space/Parks
Right-of-Way
GSI Accomplishments • CIP projects: Past pilot, now program
– Utility lead and Public/Private Partnering Projects– 232 acres restored to natural hydrology. – $18M Roughly $100K/acre.– GSI O&M Manual; defined Levels of Service; Restoration
protocol
• Redevelopment incentives/requirements– Design Guidance and concept details in Right‐of‐way
improvement manual– Stormwater Code. November 2009 adopted GSI to MEF
requirement.– Rates based on impervious surfaces. Rate credit for BMPs.
GSI higher credits– Green Factor requirement– RainWise Rebates; $4/SF mitigated
• Ongoing Adaptive Management– Greenroof monitoring, hoping to increase credits
Ballard Roadside Raingarden, Phase 1
•Spend Stimulus $$; jobs
•Pilot the application of bioretention for CSO reduction
•Get started on the 3 years allocated to Green before Grey in CSO program
Where:•NPDES 152 – 63 CSOs in 2010, approximately 40 million gallons of combined sewage
Ballard GSI for CSOCSO Control Approach
Estimated Implementation
RainWise 680 of 3800 homes participating (15‐20%)
Green AlleysPermeable Pavement
45 of 69 alleys retrofitted (65%)
Roadside Rain gardens
10 miles of existing 27 miles of roadway
impervious mitigated(37%)
Project Goals• Develop design templates for future
Roadside Raingardens– Planting strip design– Curb extension design– (Full curb shift)
• Refine construction costs• Refine performance data• (Be like Portland)
Timeline• Mar 2009 – began GSI siting and design• July – likely to receive ARRA (Stimulus) funds• July – First community meeting held• Aug 17th – formally awarded ARRA loan• Sept 17th – 90% Plans, Specs and Engineering Report required to be submitted
• October 13th – Second community meeting held
• November – Geotechnical Report finalized
The Perfect Storm• Communication• Design• Construction timing along excessive rainy winter (even for Seattle)
Communication• Inter team communication critical• Internal Knowledge Transfer critical
• Although we’ve lead very inclusive community process with all previous projects, PM chose standard pipe CIP approach
• Although SPU has overseen construction of 65‐70 blocks for complete retrofit with bioretention, CM team had NO knowledge, training about bioretention.
• Public Involvement Strategy • Project requires a lot of face time with community.
Identify who that person will be & give them enough time
• Work in residents front yard need a different model than standard CIP projects
• No existing awareness of a problem
Technical Design• Technical / Design Approach
• Risks taken but not communicated or discussed with Team
• Enthusiasm for trying to meet citizen traffic calming request took precedent over intended project scope (curb shift design and working on 28th without survey)
• Unidentified Subsurface Geology Conditions
29th Ave NW & NW 77th St
Raingardens not exactly to scale.
Raingarden Post-Construction Performance
Infiltrating (drains in < 24 hours)
Not infiltrating or infiltrating very slowly
TP‐111 0.1 in/hr
TP‐1090.15 in/hr
31st Ave NW between NW 75 & 77th St
Raingardens not exactly to scale.
Raingarden Post-Construction Performance
Infiltrating (drains in < 24 hours)
Not infiltrating or infiltrating very slowly
TP‐1080.5 in/hr
NW 66th St
28th Ave NW between NW 65th & 67th St
Raingardens not exactly to scale.
Raingarden Post-Construction Performance
Infiltrating (drains in < 24 hours)
Not infiltrating or infiltrating very slowly
TP‐117 0.15 in/hr
TP‐1180.1 in/hr
TP‐1190.15 in/hr
28th Ave NW between NW 71st & 72nd St
Raingardens not exactly to scale.
Raingarden Post-Construction Performance
Infiltrating (drains in < 24 hours)
Not infiltrating or infiltrating very slowly
30th Ave NW between NW 80th St & Loyal Way NW
Raingardens not exactly to scale.
Raingarden Post-Construction Performance
Infiltrating (drains in < 24 hours)
Not infiltrating or infiltrating very slowly
TP‐1041.2 in/hr
Bad Luck• Construction completion moved into wet
season• Fall rains roughly double typical• Highly technically savvy neighbors
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Policy
• Clear political support• Clear policy ‐ especially
around level of risk tolerated– Signs– Allowable swale depth
and ponding depth
Lessons Learned – Community Engagement
• Get out into the community early and often• Introduce the problem before presenting the solution• Don’t rely just on the community meetings to engage the community and get feedback• Written questionnaire on wet basements & soggy yards
• Projects with flexible siting require lots of rounds of community interface, because each meeting results in design changes that impact new people who haven’t been to the earlier meetings, and they too want to modify or eliminate the design
• Don’t be fooled that just because you have a lot of fans at the planning stage, doesn’t mean you won’t have a lot of critics at final design/construction
• Consider demonstration infiltration tests on evenings/weekends so skeptical neighbors can be eye witnesses.
Lessons Learned – Community Engagement
• Understand the neighborhood “look” – Curb and Gutter creates different community
ownership of frontage than ditch & culvert areas
• Be clear about:– Short term standing water and why it’s
important. Puddles are good. Puddles may be present consistently for four months of winter
– Loss of parking – impact to neighbor in front and other neighbors along the street.
– Change in Aesthetics – during construction, end of construction, 1‐yr later, 5‐yrs later
– Signs!!!– Staging has got to go in front of someone’s
house
• Follow Stormwater Code minimum infiltration feasibility guidance
• Consider ratio of sidewall to bottom area during test and try to limit horizontal flow.
• Consider potential for groundwater mounding on top of glacial till.
• If test pits find <0.5 in/hr, Monitor groundwater levels for a minimum of one winter.
• Ask community about evidence of groundwater springs, basement flooding, and other groundwater problems.
Lessons Learned – Geotechnical
• Whole project team works on site selection and design, including determination of appropriate level of data collection versus risk and cost.
• Leave time for a 2nd round of tests if the initial tests suggest high levels of soil variability
Lessons Learned – Geotechnical
Lessons Learned – Design • Design should include backup system or
at minimum a alternate concept in bid documents (underdrain) if design infiltration rate is less than 0.5 in/hr
• If moving curbs, complete a “light” survey to capture critical elevations, but don’t skip survey
• Don’t be cheap with the plants – buy some larger stock
• Review project design and function and critical project elements with CM. Clearly articulate intent of “field directed” elements in the design.
• Provide design for flow control/bypass plan and erosion control; sandbags aren’t adequate
Lessons Learned – Construction
• Bring geotechs out during construction to verify soils• Review project design goals and objectives with designer
• Review flow control and erosion and sediment control requirements and expectations with designer to ensure cells are adequately protected
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Help I need• Bioretention science and
benefits one page simplified fact sheet
• Child Safety Studies/References– How much bioretention dirt
before human health concern– Clear policy ‐ especially around
level of risk tolerated• MUTCD Requirmeent
“obstuructions within the roadway shall be marked with a Type 1 or Type 3 object marker
Questions?Questions?
City of SeattleSeattle Public UtilitiesRay Hoffman, Director
Tracy Tackett GSI Program Manager Seattle.gov/util/greeninfrastructure
29th Ave NW & NW 77th St
Original design
Retrofit design
Remove and convert back to planting strip
Raingardens not exactly to scale.
Infiltrating raingarden
TP‐111 0.1 in/hr
TP‐1090.15 in/hr
31st Ave NW between NW 75 & 77th St
Raingardens not exactly to scale.
Original design
Retrofit design
Remove and convert back to planting strip
Low functioning raingarden
Infiltrating raingarden
TP‐1080.5 in/hr
NW 66th St
28th Ave NW between NW 65th & 67th St
Raingardens not exactly to scale.
Original design
Retrofit design
Raingarden converted to live storage with underdrain
TP‐117 0.15 in/hr
TP‐1180.1 in/hr
TP‐1190.15 in/hr
Low functioning raingarden
Infiltrating raingarden
28th Ave NW between NW 71st & 72nd St
Raingardens not exactly to scale.
Original design
Retrofit design
Low functioning raingarden
Infiltrating raingarden