City of Spokane Stormwater Spokane River Forum Conference March 26, 2013
Feb 24, 2016
City of Spokane Stormwater
Spokane River Forum ConferenceMarch 26, 2013
About 1/3 of City 130 outfalls
Municipal Separate Storm Sewer System (MS4)
Direct Sewers
• Raw sewage and stormwater to Spokane River without treatment
• 1892
Interceptor
• Sewage to treatment plant and wet weather overflows to Spokane River
• 1950s
Separated
• Stormwater in separate pipes to River
• Sewage to plant (no overflows)
• 1980-93
Infiltrated
• Treatment and disposal to ground (or evaporated)
• Early 1980s to present
Spokane’s Stormwater History
2000s1940 1950 1960 1970 1980 19901890 1900 1920
Spokane’s Stormwater History
Oldest System
1980s
Modern Practice
Less stringent regulation than wastewater◦ Non-numeric standards ◦ BMPs
First Phase II NPDES permit: 2007◦ Public Education and Involvement◦ Illicit Discharge Detection and Elimination◦ Construction stormwater controls◦ Post-construction stormwater management◦ Municipal Pollution Prevention and Good Housekeeping
Regulatory Framework
Second Phase II NPDES permit cycle: 2014◦ Enhances existing requirements ◦ Adds regional effectiveness studies◦ Requires jurisdictions to “allow” low impact
development ◦ Require developments to retain on-site runoff
from the 10-year storm event
Regulatory Framework
EPA: Green Infrastructure Stormwater Management
◦ Retention and infiltration◦ Storm gardens, green roofs,
permeable pavement Land Use Management
◦ Preservation of natural features
◦ Minimize construction disturbance area
◦ Minimize impervious area
Low Impact Development (LID)
Seattle SEA Streets
No curbsReduced Street Width
(11% less impervious
area)
Reinforced Grassy ShouldersBioretention
Cells
Reduced runoff by 99%
Lincoln SURGE Spokane Urban
Runoff Greenways Ecosystem
Storm garden bio-infiltration cells
Treated stormwater flows to Cannon Hill Park Pond
Broadway SURGE Constructed 2010 Bio-infiltration cells
(storm gardens) Permeable
sidewalk Urbanized area Infiltration
Hazel’s Creek LID demonstration site and
regional stormwater facility at 42nd and Freya
Eastern WA LID Guidance Manual Ecology grant awarded to Spokane County
◦ Due date: June, 2013 Eastern WA Phase II Jurisdictions Washington Stormwater Center:
www.wastormwatercenter.org ◦ Public Comment◦ Interactive educational website
PCB Consent Decree - Supplemental Environmental Project I: LID◦ Formation of Internal LID Subcommittee and Technical
Advisory Committee◦ Educational materials
Utility Bill Insert Brochure Website: www.spokanewastewater.org/LID.aspx
◦ Formation of Stakeholders Group
City of Spokane and LID
Draft ordinance with monetary or other incentives to City Council by August 2013
Reference the Eastern WA LID Guidance Manual◦ Streamline permitting process◦ Guidance on what LID technologies are available
and suitable for Eastern Washington Assess existing City code
◦ Refer to ordinances applicable to LID
Draft LID Incentives Ordinance
What are PCBs? Man-made compounds “Banned” in 1977 but sources remain Doesn’t break down readily 209 Congeners
Why are we concerned? Spokane River out of compliance with standards Ecology sampling found PCBs in City of Spokane stormwater and
CSO Carcinogen that accumulates in food chain
What are we doing? City of Spokane: PCB Consent Decree and permit-
required wastewater monitoring Spokane River Regional Toxics Task
Force
Polychlorinated Biphenyls (PCBs)
PCB Investigations
Union Stormwater
Basin
CSO 34
Drywells
Sample and analyze for PCB Aroclors and Congeners
Catch Basin Sediments
Review Aroclor analysis results◦ Residential cleanup std. 1.0 mg/kg
Remove all sediments from catch basins Dump on separate pad, mix with sawdust Haul to lined cell at landfill
PCB Remedial Maintenance
432 CBs [Union and HI CSO 34]
280,000 pounds
26 grams PCBs removed
2010362 CBs [CSO 34 up-gradient]
268,000 pounds
3.7 grams PCBs removed
201190 CBs [Most Union, 4 HI CSO 34]
39,600 pounds
2.7 grams PCBs removed
2012
Catch Basin (CB) Sediments
Automatic flow-weighted composite sampling
Stormwater Characterization: Union Basin
Goal: 6 samples per site
Wet season 2012-2013
Event mean concentration
Compare congener patterns
Compare to previous samples (Ecology)
Stormwater Characterization: Union Basin
Level
Flow Rate
Sample Aliquots
Integrated Plan◦ Basin priority
Total PCB load greater than Union basin?
Sampling spring 2013
Stormwater Characterization : Washington Basin
Stormwater Monitoring: Cochran Basin
Samples collected wet season 2012-2013◦ DO TMDL-related
parameters BOD, phosphorus,
ammonia◦ Metals◦ Suspended solids◦ Fecal Coliform◦ Total Coliform◦ PCBs
Flow rate and volume
Stormwater Monitoring: Cochran Basin
Integrated Plan◦ Flow Volume◦ Pollutant
concentration◦ Comparison to CSOs
NPDES Permit and DO TMDL◦ Estimate pollutant
concentrations in typical City stormwater