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