BHC was selected by Southwest Suburban Sewer District to design improvements for the failing sewer beach line in Seahurst Pak. In the 1950’s, installing buried sewer mains in the tidal zones of Puget Sound was commonly done because it offered unobstructed corridors. However, these pipes, which are subjected to brackish water and shifting foundation support, have approached, and in some cases, exceeded their useful life. Dislocated joints, differential settlement, and thinning pipe wall thicknesses have resulted in increasing maintenance issues and the need for routine flushing.

 

Alternatives evaluated included: abandonment of the beach line and re-directing flow from the beach into a different drainage basin; installation of a new beach line; repair of the gravity line in place; and sliplining the existing pipe with a new force main.

 

The selected option involved sliplining the main with a 4-inch force main, constructing a new waterfront pump station, and serving the parcels along this 6,000 foot segment with grinder pumps.

 

Permits obtained included a Corps Nationwide Permit (wetlands), Shoreline Permit, Biological Evaluation (endangered species), JARPA, SEPA Checklist, and WSDOT agreements.

 

 

BHC is responsible for preliminary and final design of a 1.2 mgd food processing secondary wastewater treatment plant expansion, including expansion of the sequencing batch reactors (SBR), installation of new cloth disc filtration, expansion of UV disinfection and installation of new chlorination / dechlorination facilities.

 

 

The pump station rehabilitation included installation of submersible pumps in the existing wet well, replacement of the dry well with a valve vault, new pumps, valves, controls, and telemetry and replacement of the existing generator building with a new building in the same location. The pumps are sized to provide 324 gpm at 256 feet total dynamic head.

 

The evaluation and selection of improvements, development of construction plans and specifications, and construction engineering services were provided in two phases. Phase 1 included identification and evaluation of lift station alternatives, development of opinions of probable cost, coordination with the public, and selection of a preferred alternative. Development of a Preliminary Design Report, 30 percent design drawings, and assistance with required permits and approvals. Phase 2 included development of final plans and specifications, bidding assistance and construction engineering services. 

 

BHC was selected by PUD No 1 of Clallam County to conduct a Feasibility Study regarding the development of a sewer system for the Carlsborg community, which has been designated by Clallam County as an unincorporated urban growth area. The study projected population and wastewater flows, then developed a conceptual collection system, treatment facilities, and a re-use application. Project costs were estimated and distributed through an assumed assessment methodology to the benefited properties. These concepts were discussed with the public through a series of public meetings to gather comments.

 

Wastewater from the community would be reclaimed and used to augment flows in the Dungeness River. This solution may facilitate an additional water right for the Clallam PUD, which may allow development within the Carlsborg UGA to achieve the land use densities envisioned in the land use plan prepared by Clallam County for the community. Sewerage facilities for the Carlsborg community would likely be implemented through a phased series of sewer collection piping extensions. Treatment is anticipated to be provided initially by a sequencing batch reactor (SBR), which may be expanded during subsequent sewerage phases to become a membrane bioreactor (MBR).

BHC provided preliminary engineering, final design, and services during construction for facilities to intercept and control existing combined sewer overflows (CSO) in the City of Snohomish. The new facilities include a new 6,500 gpm combined CSO and stormwater pump station, nearly 6,200 feet of 18-inch and 24-inch force main and gravity sewer pipe, 3,000 feet of 18- to 30-inch stormwater pipe, and 1,200 feet of 12-inch water main. Special design considerations include stabilization of the pump station site using a stone column system, architectural pump station features to conform to the historic neighboring community, and location of separate sanitary sewer, stormwater, and potable water pipelines within one relatively narrow existing City street. The pump station consists of two suction lift pump sets, one at 6,500 gpm (sewer), and one at 5,400 gpm (storm).

 

A key factor in the project was the crossing of an SR-9 interchange under a WSDOT bridge. We secured WSDOT approval of a Channelization Plan and Franchise Agreements. We also convinced WSDOT to agree to closing off-ramps and on-ramps to SR-9 for weeks at a time to allow for phased, efficient pipeline installation. A six-stage traffic control plan was developed to maintain and detour traffic while pipe installation work proceeded.

 

 

This project consists of the design and construction of three pump stations, approximately 11,000 linear feet of sanitary sewer force main and 25,000 feet of gravity sewer main.  The scope of work included preliminary design, design, permitting, and construction management services as well as assistance with the formation of a Local Improvement District (LID).  The preliminary design services consisted of evaluating potential service areas, reviewing probable construction costs, and defining the LID boundary.  Design efforts included preparing the construction documents for the gravity sewer, force mains, and sewage pump stations, developing detailed construction cost estimates, applying for the required permits, assisting in the acquisition of easements, and assisting the City with the formulation of the LID.  The design team also prepared environmental reports, provided survey, and geotechnical support.  Design challenges included highly saturated ground conditions, two Jack and Bore operations to maintain traffic in SR 161 and multiple utility crossings. The construction management services involved observing the contractor’s work for compliance with the contract, interfacing with the public to determine the location for the side sewers, administering the construction contract, and coordinating with the numerous regulatory agencies.

 

BHC was responsible for design of the new Park Place Pump Station, forcemain, and connection to the wastewater treatment plant. The new Park Place Pump Station intercepts all of the flow from the Department of Corrections plus flow from the West Main Pump Station and the gravity area along Main Street. This service area comprises about 30% of the City’s total flow.

 

The pump station consisted of a 1,700 gpm triplex submersible pump station and 4,500 feet of 16-inch forcemain.