Presentation Abstract

Clarks Creek is designated as an important salmon-bearing creek (7 species) in Pierce County, WA. Clarks Creek was identified as a Category 2 waters of concern in 2004 for low dissolved oxygen (DO). In 2014, the Washington State Department of Ecology (Ecology) reassigned Clarks Creek as a Category 5 water body and placed it on the 303d list for being impaired by low dissolved oxygen (DO) and excessive fine sediment. In December 2014, Ecology issued a Total Maximum Daily Load (TMDL) designed to increase DO and reduce sediment loads. The DO waste load allocation (WLA) used stormwater runoff as a “surrogate measure.” It requires the County to remove or treat 50 percent of the stormwater runoff volume from a very large storm event that occurred on October 20-21, 2003. The sediment WLA requires a 66 percent reduction in the average annual sediment load to the creek. In addition, there were two Load Allocations (LAs) issued to address the dense aquatic plant growth (Elodea nuttalii) and lack of riparian shade (high temperatures) that exist in the Creek. Pierce County contested the TMDL, citing concerns regarding data and modeling limitations and the associated uncertainty regarding cause and effect relationships between stormwater, Elodea, sediment, and DO. In addition, the County was very concerned about how expensive programmatic implementation would be and whether its expenditures (investments) would reliably result in the re-attainment of the applicable water quality standards (and result in a delisting). The County entered into a Dispute Resolution process with Ecology, which culminated in a formal agreement to develop a mutually acceptable TMDL implementation plan (Plan). The Dispute Resolution agreement included a 5-Year Reassessment of the TMDL metrics, models, data and progress and an adaptive management approach. The County prepared the Plan using a continuous simulation hydrologic model in combination with a spreadsheet model to estimate (quantify) the stormwater volumes treated and sediment loads reduced by a range of measures including stormwater treatment, channel stabilization and street sweeping. The Plan includes conceptual designs, cost estimates, and a schedule for the measures slated for the next 5 years. The Plan introduces a number of other innovative approaches such as the use of Urban Stormwater Catchments, BMP Rapid Assessments and a crediting program for quantifying and tracking the County’s measures. The Plan also describes the proposed 5-year Reassessment process which includes monitoring, modeling, and other activities to assess progress and identify potential adjustments to the TMDL. The County will begin implementing the Plan in the spring of 2017.

Session Title

Policy and Management Challenges for Restoring and Protecting Water Quality in the Salish Sea

Keywords

Clarks Creek, TMDL dispute resolution agreement

Conference Track

SSE8: Policy, Management, and Regulations

Conference Name

Salish Sea Ecosystem Conference (Seattle, WA : 2018)

Document Type

Event

SSEC Identifier

SSE8-27

Start Date

5-4-2018 2:30 PM

End Date

5-4-2018 2:45 PM

Type of Presentation

Oral

Contributing Repository

Digital content made available by University Archives, Heritage Resources, Western Libraries, Western Washington University.

Geographic Coverage

Salish Sea (B.C. and Wash.)

Rights

This resource is displayed for educational purposes only and may be subject to U.S. and international copyright laws. For more information about rights or obtaining copies of this resource, please contact University Archives, Heritage Resources, Western Libraries, Western Washington University, Bellingham, WA 98225-9103, USA (360-650-7534; heritage.resources@wwu.edu) and refer to the collection name and identifier. Any materials cited must be attributed to the Salish Sea Ecosystem Conference Records, University Archives, Heritage Resources, Western Libraries, Western Washington University.

Type

text

Language

English

Format

application/pdf

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Apr 5th, 2:30 PM Apr 5th, 2:45 PM

The Clarks Creek TMDL dispute resolution agreement plan: advancing the use of model based analysis to demonstrate reasonable assurance in WA State

Clarks Creek is designated as an important salmon-bearing creek (7 species) in Pierce County, WA. Clarks Creek was identified as a Category 2 waters of concern in 2004 for low dissolved oxygen (DO). In 2014, the Washington State Department of Ecology (Ecology) reassigned Clarks Creek as a Category 5 water body and placed it on the 303d list for being impaired by low dissolved oxygen (DO) and excessive fine sediment. In December 2014, Ecology issued a Total Maximum Daily Load (TMDL) designed to increase DO and reduce sediment loads. The DO waste load allocation (WLA) used stormwater runoff as a “surrogate measure.” It requires the County to remove or treat 50 percent of the stormwater runoff volume from a very large storm event that occurred on October 20-21, 2003. The sediment WLA requires a 66 percent reduction in the average annual sediment load to the creek. In addition, there were two Load Allocations (LAs) issued to address the dense aquatic plant growth (Elodea nuttalii) and lack of riparian shade (high temperatures) that exist in the Creek. Pierce County contested the TMDL, citing concerns regarding data and modeling limitations and the associated uncertainty regarding cause and effect relationships between stormwater, Elodea, sediment, and DO. In addition, the County was very concerned about how expensive programmatic implementation would be and whether its expenditures (investments) would reliably result in the re-attainment of the applicable water quality standards (and result in a delisting). The County entered into a Dispute Resolution process with Ecology, which culminated in a formal agreement to develop a mutually acceptable TMDL implementation plan (Plan). The Dispute Resolution agreement included a 5-Year Reassessment of the TMDL metrics, models, data and progress and an adaptive management approach. The County prepared the Plan using a continuous simulation hydrologic model in combination with a spreadsheet model to estimate (quantify) the stormwater volumes treated and sediment loads reduced by a range of measures including stormwater treatment, channel stabilization and street sweeping. The Plan includes conceptual designs, cost estimates, and a schedule for the measures slated for the next 5 years. The Plan introduces a number of other innovative approaches such as the use of Urban Stormwater Catchments, BMP Rapid Assessments and a crediting program for quantifying and tracking the County’s measures. The Plan also describes the proposed 5-year Reassessment process which includes monitoring, modeling, and other activities to assess progress and identify potential adjustments to the TMDL. The County will begin implementing the Plan in the spring of 2017.