Wastewater

 Below are some of our representative projects, sorted alphabetically.

  • City of Anacortes,
    Wastewater Treatment Plant Outfall Repair

Skillings Connolly worked closely with the City to develop a plan to repair and replace approximately 175 LF of existing 24-inch reinforced concrete pipe with 24-inch HDPE pipe. The existing wastewater treatment plant’s sole outfall, located at the end of R Avenue on the Port of Anacortes property, had been experiencing effluent leakage along a section of the old outfall pipe, prior to the effluent reaching the multi-port diffuser discharge point. A combination of joint failure, settlement, and a prior unsuccessful attempt at slip-lining with an 18-inch HDPE pipe.

The repair required designing a temporary bypass system to maintain operation of the treatment plant during the repair (the plant only had a 4-hour shutdown window for the implementation of a bypass), coordination with the Port’s logistics throughout the project, design of a sheet-pile cofferdam and implementation of the fish-exclusion measures to comply with the environmental requirements set forth in the USACE permits and HPA, and providing construction management and on-site support to the City and the Contractor to mitigate for unknown conditions and prevent over-run of the fish-window mandated schedule.

Our experience in marine outfall construction, pumps, and hydraulic design allowed us to design an implementable temporary bypass solution which was critical to executing the repairs. We provided active construction support to help mitigate for unknown conditions discovered during construction. Our responsiveness and ability to communicate effectively allows us to reduce conflicts and prevent schedule impacts.

  • City of Lynnwood,
    Sewer Improvements
    Lift Stations #4 and #8

Skillings Connolly, Inc. provided design services for Sewer Improvements Related to Lift Stations No. 4 & 8. The project involved the upgrades of the existing sewer lines for increased flow capacity. The project consisted of two separate sewer conveyance systems: One from Lift Station No. 4 to 8, and the other the gravity portion of the sewer conveyance system from Lift Station No. 8 to 10.

City of Yelm,
Reclaimed Water Comp Plan

Skillings Connolly completed the planning, design, construction management and startup of various upgrades to the City of Yelm’s sewer facility to provide municipal water reclamation and reuse, primarily via land application.

The project included preparation of a comprehensive sewer plan, engineering report, SEPA/NEPA documentation and design of the City’s new water reclamation plant. The project increased the plant’s capacity from a 300,000-gallon per day secondary treatment facility to a 1,000,000-gallon per day Class A Water Reuse Facility. This undertaking, for which Pilot Project status had been granted by DOE and DOH, uses the innovative approach of applying wastewater to land areas within specified classes of land use and was the first in Washington to use this methodology for 100% of the wastewater generated city-wide.

Skillings Connolly designed the reclaimed water pump station for Yelm’s water reclamation facility. The pump station delivers reclaimed water to various facilities located along the two-mile distribution line and is connected to the plant’s SCADA system to track water use and pump operation. It maintains 75-psig pressure and provides a flow of 700 gallons per minute. Through public involvement and identification of potential reclaimed water uses, Skillings Connolly helped the City of Yelm develop a plan for zero wastewater discharge to surface water and achieve 100% reuse of reclaimed water. The following consumptive and non-consumptive beneficial uses were identified:

  • Groundwater Recharge
  • Stream Flow Augmentation
  • Wetland Enhancement
  • Fire Protection
  • Food Production
  • Industrial Uses
  • Vehicle Washing
  • Irrigation – Parks, Schools, Churches, & Streetscapes

The City’s reclaimed water program continues to be successful due to the widespread community acceptance of reclaimed water as a viable resource. Skillings Connolly led the public acceptance effort through school-based education and awareness programs, marketing and direct education with users. By working closely with schools, churches, fire stations and residents, all of which are now among Yelm’s many paying reclaimed water customers, Skillings Connolly helped the City go forward with confidence, knowing that users would be there to create demand for the reclaimed water.

Helix Design Group,
Mason County Public Works Facility

We prepared final PS&E for the site development which included drainage, septic, and water reports in conjunction with the SEPA documentation; gathered existing record data along with survey work for compilation of a base map; and provided engineering of water system, site septic system, drainage, erosion control, grading, paving, and access roads.  Skillings Connolly coordinated with utility companies and gained approval from the Department of Health for the water system.  The water system included a new well, a 200,000 gallon storage tank, fire pump, distribution piping, and fire suppression.

Washington State Department of Corrections,  Larch Corrections Center Wastewater Lagoon Sludge Removal

The Larch Corrections Center (LCC) wastewater treatment plant sludge/biosolids storage lagoon had a 50-year accumulation of both organic and inorganic sludge, which was in need of being dredged.  There were concerns about the integrity of the treatment lagoon lining, along with the stability of the lagoon dirt levee and its ability to hold water in the event of an earthquake or significant rain event.  Consequently, Skillings Connolly documented three alternatives in the pre-design report for sewer system reconfiguration and a “status quo” option, including conceptual system layouts, estimates of capital and operational costs, life-cycle cost analyses, and a discussion of advantages and disadvantages of each option.  Based on this work, DOC selected a preferred alternative to remove sludge from the existing lagoon so it could be abandoned and to install a new sludge dewatering bed system to recycle biosolids. This option resulted in significant savings in operational costs over the 30-year study period.

Washington State Department of Transportation (WSDOT), Sewer Lagoon Study

WSDOT operates Safety Rest Areas (SRA) around Washington State. Nine (9) of the SRAs in Eastern Washington utilize sewer lagoons to treat effluent generated from SRA use. Skillings Connolly is currently evaluating each of the lagoon systems, to include: lagoon chemistry, liner integrity, overall operations and condition, and current sludge volumes within the lagoons. The Condition Assessment of WSDOT’s Safety Rest Areas utilizing sewer lagoons includes land surveying, aerial survey using a drone, ground and pond topography, base map preparations, data collection, and analysis at nine (9) individual sites.