Spokane River Forum: City of Spokane Permeable Pavements

Spokane River Forum: City of Spokane Permeable Pavements Spokane River Forum March 23, 2016 Mark Papich, PE Senior Engineer City of Spokane Integrated Capital Management

It s all about the Spokane River City of Spokane is invested in reducing pollutant discharges to the Spokane River through the use of permeable pavements and other BMPs. Improving the health of the Spokane River provides a statewide benefit & is a statewide priority Flows through 2 states, several WA counties & sovereign lands of the Spokane Tribe Spokane River and Columbia basins represent 2 of 4 priority water basins listed by Ecology

Permeable Pavements and the Integrated Strategy As part of the Integrated Clean Water Plan the City is committed to mitigate stormwater when rebuilding streets. Permeable pavements are a solution 3-dimensional view of R/W Solving multiple infrastructure needs with the same dollar. Financial commitment to integration Revenue Bonds (investors) Street Levy Approved (voters)

Objectives of Permeable Pavements Environmental Cleaner River faster Pollutant removal beyond permit requirements Financially Responsible Live within our means by achieving savings from multiple benefits

Permeable Pavement Benefits Permeable Pavement Manages stormwater WITHOUT Large surface area for swales Extra cost for piping and collection system AND provides a means for New pavement Bike lane options Maintenance Benefits No turf to mow, fertilize, irrigate

Current Porous Pavement Installations West Broadway Hazel s Creek LID Liberty Park (Madelia St.) Upriver Dam Olmsted Brothers Green RPWRF LID Parking Lot

Future Projects Havana Street Bike Lanes 2016 Construction Sharp Avenue 2017 Construction

Sharp Avenue Project Area

Sharp Avenue: MS4 Basins MS4 Outfall

Sharp Avenue Existing Condition Existing Features: 2 vehicle lanes in each direction Parking lanes on each side of the street Crowned road draining to catch basins on the sides of the street 12 Hr. pedestrian volumes are 200-1,000

Sharp Avenue Proposed Condition Proposed Features: Lane reduction from 2 vehicle lanes each direction to 1 lane each direction Bike lanes in each direction Parking on both sides of the street Porous asphalt and pervious concrete paving Reverse crown to drain to center medians (backup system/landscaping) Bumpouts for pedestrian safety

Sharp Avenue

Sharp Avenue - Geotech Geotech Summary: 4 borings drilled Soils generally gravels and sands (consistent w/ N. Spokane) CEC values ranged from 8.92 meq/100g to 14.2 meq/100g. >5 meq/100g required by Ecology for treatment credit No groundwater encountered (borings to 25-feet)

Sharp Avenue Collaboration with Gonzaga University: City and Gonzaga to share maintenance Median landscaping, striping, etc. GU conducted a Permeable Pavement Feasibility Study (August 2014) Faculty and students Concluded that the proposed permeable pavements are feasible for Sharp Avenue Senior Projects associated with Sharp Avenue

Sharp Avenue Monitoring and research: We want to confirm that it works. Water quantity and quality GU to develop monitoring system design. City is committed to monitoring the project for 3-years after construction.

Sharp Avenue Proposed Monitoring System Design 4 individual monitoring cells (50 x 26 )

Sharp Avenue Funding Design and construction funding through Ecology stormwater grants.

Havana Street Project Area

Havana Street Typical Section Main Features Porous Asphalt Bike Lanes Gravel Swale Structural bioretention soil mix Trees No Curb

Havana Street Treatment Area Section CEC testing not performed Sand filter utilized for Ecology treatment credit

LID Demonstration at RPWRF Traditional Asphalt Gravel Strip Grass Pavers Interlocking Pavers Pervious Concrete

LID Demonstration at RPWRF Photos

LID Demonstration at RPWRF Photos

West Broadway Too much water in the initial mix and the addition of water to the surface by misting caused binding-not pervious. Oak St. Pervious concrete sidewalk installed July, 2010 Elm St.

Liberty Park Sidewalk Pervious concrete sidewalk installed: 2011 Low infiltration rate Infiltration improves from north to south: did the pour start at the north end and continue to dry the mix as it moved south? did skill improve over length of sidewalk?

Hazel s Creek LID Pervious concrete trail installed August 9, 2012 Excellent Infiltration

Olmsted Brothers Green Pervious concrete sidewalk and pavers demonstration project installed July 2014 Excellent infiltration

Finch Arboretum LID Project FEATURES Completed in Fall of 2015 7,000 SF porous asphalt parking lot expansion Original lot drained directly to drywell Original lot and F Street treated in new bioretention facility Porous asphalt expansion drains great and has weathered its first winter

Finch Arboretum LID Project

Finch Arboretum LID Project Questions?