Fitting Green Infrastructure In a Historic Neighborhood

Transcription

1 Fitting Green Infrastructure In a Historic Neighborhood May 17, 2017 Presented by Marcia Davis, PE

2 Spokane Stormwater Map of stormwater infrastructure throughout the City of Spokane The City s Stormwater infrastructure consists of an MS4, combined sewer overflow(cso), infiltration including underground injection controls (UIC), and evaporation. Image from:

3 West Central Neighborhood Historic Character

4 West Central Neighborhood Historic Character

5 West Central Neighborhood Demographics Area: Square miles Population: 8,435 Population density: West Central: 5,334 people per square mile Spokane: 3,692 people per square mile Population Portion: Males: 4,153 Females: 4,280 Education Attainment Median age: Males: 35.7 years Females: 35.2 years Average number of cars or other vehicles available in houses/condos: West Central Neighborhood: 1.8 Spokane: 2.1 Based on data

6 West Central Neighborhood Assets The intersection of Elm St.& Gardner Ave The intersection of Dean Ave & Cannon St Most streets have sidewalk and full street tree canopy. Gardner Ave

7 West Central Neighborhood Challenges Holmes Elementary School on-street parking Dean Ave.& Cochran Intersection The availability of on-street parking remains a problem for many areas of the neighborhood.

8 Old Trolley Tracks

9 CSO Basins 14 & 15 Charteristics CSO Basin 14 consists of 7 impervious acres CSO 15 consists of 14 impervious acres Catch basins are connected directly to the sanitary sewer Basins are relatively flat with good draining soils CSO 14 and 15 Basins

10 Spokane Regional Stormwater Manual Bioinfiltration Swale Requirements: Treat the 6 month storm 1.0 inch NRCS Type II 24 hour storm Contain the volume of the 10 year storm 1.8 inch NRS Type IA 24 hour storm

11 Goal: Remove enough area to reduce to one overflow per year CSO 14 s Outfall Hydrograph from 1.2 yr Storm CSO 15 s Outfall Hydrograph from 1.2 yr Storm CSO 14 s Outfall Hydrograph from 1.2 yr Storm after impervious area is removed/separated CSO 15 s Outfall Hydrograph from 1.2 yr Storm after impervious area is removed/separated

12 Finding Balance Objectives Reduce overflows one per year over 20 years Stay within budget Low maintenance cost Challenges State of the art engineering Avoid removing parking Accommodate bus service Protect Trees Minimize street replacement Create an neighborhood amenity Old Trolley Tracks

13 Feasible Separation Locations

14 Alternative 1- Bioretention Swales Spokane Region Stormwater Manual o 200 bioretention swales o 18 Acres removed CSO Removal Method o 150 bioretention swales o 13 Acres removed

15 Opportunities for the neighborhood Amenities More Planting Native plants along the sidewalk Utilize the existing infrastructure Dutch Jake Park (existing green infrastructure in Neighborhood) Dutch Jake Park Plants list from AHBL

16 Alternative 1- Bioretention Swales Advantages & Disadvantages Advantages City has extensive experience with this type of system Approved by SRSM Treats and infiltrates at the site Disadvantages Largest impact to streets and sidewalk Curb extensions reduced street parking Significant irrigation system costs Greater cost than budgeted amount

17 Alternative 2- Storage

18 Alternative 2- Storage Advantages & Disadvantages Advantages Less neighborhood construction disruption Lower capital cost alternative than #1 Does not remove parking places Disadvantages Conveys additional runoff to the reclamation facility Higher maintenance cost

19 Alternative 3- Soil Cells

20 Alternative 3- Soil Cell Advantages & Disadvantages Advantages Small system foot print Curb lines will remain as they are today No system medium replacement Approved as bio infiltration equivalent Allows parking to be retained Reduces overall maintenance Treats and infiltrates at the site Disadvantages New system to City construction management City maintenance crews do not have experience with this type of system

21 Final Map Final Plan

22 Lesson Learned Understand your goals at the beginning. Consider life cycle costs for maintenance and treatment. Space is a premium in the urban environment. Communication with residents & property owners is essential. Creative solutions are available if you are willing to step outside the ordinary and look for them.

23 Enhancements Traffic Calming on A Street Reference from City of Spokane Traffic Calming Toolbox: ms/trafficcalming/2017/2017-traffic-calming-toolbox.pdf Landscaping Signage Crosswalks Bulb Out North Denver Avenue / Portland, Oregon

24 Project Schedule Design is expected to be completed in the summer of Construction is anticipated to begin in late summer of 2017 with construction completed in 2018.

25 It s All About the River Special Thanks to ICM Staff: Beryl Fredrickson Eric Lester Mark Papich Ryan Broadwater Sam McKee Xue Bai Photos by Charley Gurche Marcia Davis, PE City of Spokane Principal Engineer Integrated Capital Management mdavis@spokanecity.org