roadside rain garden’s: wrong and how we recovered...– gsi o&m manual; defined levels of...

ASCE LID ConferenceSeptember 27, 2011

Ballard Roadside Rain Garden’s: What Went Wrong and How we Recovered

City Sewer System

• Combined and Partially Separated (2/3 of City)

• Separated (1/3 of City)

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

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)

What Could Go Wrong?

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





TP‐1080.5 in/hr

NW 66th St

28th Ave NW between NW 65th & 67th St





TP‐117 0.15 in/hr

TP‐1180.1 in/hr

TP‐1190.15 in/hr

28th Ave NW between NW 71st & 72nd St





30th Ave NW between NW 80th St & Loyal Way NW





TP‐1041.2 in/hr

Bad Luck• Construction completion moved into wet

season• Fall rains roughly double typical• Highly technically savvy neighbors

2121

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

2828

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


Infiltrating raingarden

TP‐111 0.1 in/hr

TP‐1090.15 in/hr

31st Ave NW between NW 75 & 77th St


Original design

Retrofit design

Remove and convert back to planting strip

Low functioning raingarden


TP‐1080.5 in/hr

NW 66th St

28th Ave NW between NW 65th & 67th St


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



28th Ave NW between NW 71st & 72nd St


Original design

Retrofit design



30th Ave NW between NW 80th St & Loyal Way NW


Original design

Retrofit design


TP‐1041.2 in/hr

roadside rain garden’s: wrong and how we recovered...– gsi o&m manual; defined levels of...

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