Wastewater Treatment Plant Upgrade

Owner: Skagit County Sewer District No. 2

Client: Kelly Wynn Wastewater Treatment Plant Operator  |  Contractor: McClure and Sons, Mill Creek

The District’s secondary WWTP is located northeast of the outlet of Big Lake, less than a quarter mile from Nookachamps Creek. The WWTP exports treated effluent out of the Nookachamps Creek basin to the lower Skagit River. Equipment in the SCSD#2 WWTP – built in 1978 – was nearing the end of its useful life and comprehensive planning showed the need to increase capacity to meet the expected growth in the area surrounding Big Lake.

The District, led by CHS, completed a water reuse feasibility study to consider upgrading to a water reclamation facility (WRF), treating effluent to reclaimed water standards for beneficial use as instream flow mitigation. A new reclaimed water outfall to Nookachamps Creek would allow water to be discharged in the same tributary basin, thus achieving more effective water resource management by reducing the impact of water withdrawal limitations imposed by the recently-amended Skagit River instream flow rule. The study concluded instream flow mitigation was not presently feasible due to creek water quality impairment designations and the need for additional total maximum daily loading (TMDL) analysis prior to any new discharge.

Although construction of a WRF was postponed, the WWTP upgrade was designed for future conversion to a water reclamation facility. The rotating biological contactors and secondary clarifiers were replaced with a membrane biological reactor (MBR) system with UV disinfection. In addition, the upgrade incorporated stormwater management facilities, upgrade of Lift Station #1, and upgrade of the electrical connections between the two. The project involved extensive permitting and multi-agency coordination – led by CHS – with DOE, DOH, DFW, USACE, WSDOT and Skagit County. Construction was completed in late 2014.

Funding: PWTF Construction Loan

Dates:
Design 2008,  Construction completed 2014
CHS Staff:
Rodney Langer, P.E., Project Manager
Nadine Firestine, P.E. Project Engineer

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