Century West Engineering Corporation

Wastewater Conveyance by Century West Engineering

Wastewater Conveyance

152nd Drive Sanitary Sewer Improvements; Water Environment Services, Clackamas, OR

This project included design and construction management services to complete approximately 5,500 lineal feet of 12” and 15” sanitary sewer pipe. The project reduced the amount of wastewater that would be sent into the Sieben Creek Pump Station by diverting a significant area of contribution east of SE 152 Drive south into the Clackamas Interceptor on Highway 212/224. The design required that individual connection details at all of the side streets be provided along with a suggested construction sequence in order to insure flows were not disrupted. Careful coordination with operation staff resulted in the need for only one short section requiring temporary pumping. Other efforts included working with Clackamas County DTD to complete surface restoration improvements including an asphalt concrete overlay.

2004 Sewer Improvements Project; Fairfield, Washington

Century West assisted in obtaining CDBG funding for the Town of Fairfield and provided design engineering services on 1,200 feet of sanitary sewer main. This project included providing 8-inch PVC sanitary sewer line, side sewers and manholes to rectify infiltration and inflow problems in the existing system. Century West provided construction management services for this $84,000 construction project.

2005 Sewer Improvements, Tekoa, Washington

Century West provided services in preparation of plans, specifications, and estimates for the construction of approximately 1,500 feet of 12 inch PVC sewer pipe with new manholes. CWEC also assisted in bidding the project, including conducting the pre-bid conference. Bidders’ questions were answered and prepared addenda as required. Construction management services were also provided to the City of Tekoa for this $116,000 construction project. Century West provided grant assistance which included filing the application for funding and assistance with the required reporting through CDBG.

2008 Sewer Improvements Project, Tekoa, Washington

Century West prepared plans, specification and cost estimates for the construction of approximately 1000 feet of 12-inch PVC sewer pipe and 350 feet of 8-inch PVC sewer pipe with new manholes. Century West assisted in bidding the project, and will provide construction management services during construction of the project. Century West assisted the City in obtaining funding from the Public Works Trust Fund and CDBG.

5th Street and Hospital Sewer Replacements; Davenport, Washington

Century West provided design and construction management services for this sewer replacement project. The project included replacing approximately 3,000 feet of sewer main, reconnecting side services and replacing manholes. The work was scheduled and completed prior to reconstructing 5th Street to avoid future cuts in the new pavement. Century West provided documents to receive quotes through the City’s Small Works Roster. We reviewed quotes and recommended award. During construction, we provided inspection of the work and prepared pay estimates, change orders and other project documentation.

Alley Sewer Extension; Airway Heights, Washington

Century West Engineering provided engineering design services for 400 feet of sanitary sewer 8”PVC pipe and side sewer to the City of Airway Heights. This project extended a sewer main 400 feet to accommodate several businesses with frontage along SR2, from Lundstrom to Zielger. This project eliminated several septic tanks from infiltrating wastewater into the ground.

Combined Sewer Overflow (CSO) Reduction Project; Spokane, Washington

Century West is currently working with the City of Spokane and other consultants to develop a CSO plan which would address CSO reduction and compliance with State and Federal regulations as they pertain to CSO discharge to the Spokane River and its tributaries. Century West is aiding in basin plan design, regulatory interpretation and program management. This project is a multi-million dollar project designed to protect the water quality of Spokane's river and aquifer that sustain a vibrant future for the Spokane community. This project is multi-disciplinary in nature and includes innovative approaches to sewer design and modeling, water quality analysis, historical and regulatory research, and constant interaction with public and regulatory agencies.

H2 Lift Station Replacement Project; City of Hayden, Idaho

Century West is a subconsultant to CLC Associates for this on-going project which is part of a large commercial development. The project consists of designing a new wet-well drywell self priming pump station. Tasks include designing an 18-feet deep cast-in-place concrete wet well, sizing and selecting the centrifugal pump system, laying out the new gravity and force main connections and coordinating the design of an emergency generator and SCADA system with an electrical engineering subconsultant. Design challenges include the presence of three other lift stations which share two force mains into which the H2 lift station will discharge.

Happy Valley Sewer Improvements – Phase I-III; Water Environment Services, Happy Valley, OR

The projects have included over 70,000 lineal feet of 8" sanitary sewer pipe across public right-of-way and required acquisition of over 250 easements across private property. Extensive coordination efforts were necessary to ensure the topographic survey information over this large area was delivered on schedule to maintain the aggressive project schedule for each phase. Other work completed at the beginning to facilitate the design for review by WES staff included approval of the drafting standards, format, and layout of sheets so major changes were not required from the initial 50% submittal. Negotiations with property owners over alignment and other miscellaneous issues with WES staff were attended whenever requested. The hands-on approach to the design kept the schedule on track for construction of each phase.

Kellogg Pump Station Diversion; Water Environment Service, Oregon City, OR

This project included more than 1,800 feet of 10-inch gravity main located adjacent to and beneath I-205 in the vicinity of the Strawberry Lane overpass. The crossing of I-205 required a 42-inch diameter boring approximately 550 feet long. Preliminary design included review of a previously completed alignment study and selection of a final route through negotiations with private property owners and Oregon Department of Transportation (ODOT). The improvements were able to eliminate one pump station by diverting flows from the sub-basin via a new gravity line to another section of the system. The improvements required extensive coordination with ODOT to garner their support in choosing an alignment to install a boring beneath the freeway and the support from owners of an apartment complex on the east side of the freeway. Other efforts required completion of a wetland delineation study to obtain permits from Division of State Lands and Corps of Engineers for construction of the pipeline in the vicinity of the Kellogg Creek Wetland National Resource Area.

Lift Station Improvements; Reardan, Washington

Century West provided design and construction management services for this recently completed project. This project involved developing alternatives to eliminating large solids that repeatedly clogged up and damaged their existing lift station. Due to the severity of the damage, new submersible chopper pumps were installed. This project was completed in conjunction with improvements to the Town’s wastewater treatment facility and funded in part through a Community Development Block Grant and Centennial Clean Water Fund Loan.

Lilac Lane Sewer Replacement; Liberty Lake, Washington

The existing sewer main was built in the 1920's, was badly deteriorated, and extremely deep. The existing right-of-way, only 20 feet wide, is crowded with beachfront homes and improvements on either side. Century West provided a design for an alternative route that significantly reduced the sewer main depth and eliminated a main that is located under a house and cuts diagonally across vacant lots. We met with residents to determine the side sewer locations and traffic flow restrictions, and to describe the project and the need for the new sewers.

Mission Sanitary Sewer Project; Spokane, Washington

Century West designed 28,000 feet of sewer mains in an unsewered area in the Spokane Valley. This $3 million project for Spokane County Utilities involves roadway reconstruction, sanitary sewers, and side sewers for 440 homes. Design services include preparing plans, specifications, and construction cost estimates for the project, computer modeling of sewage flows, bidding services, and environmental permit applications. We also provided construction inspection services.

North Spokane Pump Stations; Spokane County, Washington

Century West provided construction management and quality control services for three sewage pump stations: Little Spokane (NSI Package 5A), Dartford (NSIE Package 4), and Whitworth (NSIE Package 4). Twin submersible pumps at each pump station were rated at 400 gpm, 2000 gpm, and 2800 gpm each. This $4.1 million project included construction of wet wells, valve vaults, gravity sewer and force mains, pump house and containment structures, access roads and site work. Services included inspection, surveying, design clarifications and modifications, start-up planning and testing, and record drawings.

Rock Creek Wastewater Conveyance; Water Environment Services, Rock Creek, OR

This project includes preliminary and final design services for approximately 7,800 feet of 30” gravity sewer capable of serving more than 18,000 acres of land to be used for residential housing in the next 20 years. The interceptor will be located parallel to and within the Rock Creek Corridor between Sunnyside Road and Highway 212. The project requires several specialized firms on the team to complete environmental permitting, archeological investigations, trenchless construction design, geotechnical investigations, and property surveying. The final route and construction methods including trenchless construction using boring methods were determined after extensive field investigations and meetings with WES staff. Other stakeholders including private property owners, Corps of Engineers, Division of State Lands and Oregon Department of Fish & Wildlife played active roles in the decision making process to find an acceptable route that minimized disturbance through the corridor.

Sewer System Improvements; Fairfield, Washington

Portions of the Town's sewer collection system had serious inflow / infiltration (I/I) problems. Century West analyzed I /I flow measurements, monitored TV inspection of the sewer mains, and coordinated smoke testing. We prepared an evaluation report, assisted the Town with a successful CDBG grant application, and designed collection system improvements. Century West also managed the construction of this $180,000 project, which included replacement of 2,200 feet of 8-inch and 10-inch sewers, including 13 manholes. 

Steamboat Rock and Central Ferry State Parks, Sewage Lagoon Additions/Repairs; Washington State Parks and Recreation Commission.

Century West was retained by the Commission to design additions and repairs to the lagoon treatment systems at Central Ferry and Steamboat Rock State Parks. The improvements included the relining of two existing lagoon cells, as well as the construction of an additional cell. The design of the improvements facilitated construction with uninterrupted usage of the existing treatment systems. At Steamboat Rock State Park, a new treatment cell was added. The new cell was carefully designed so that a balance in the earthwork was achieved, reducing the impact of hauling large amounts of fill material to or from the site. Reducing the visibility of the new cell was also very important aesthetically, so the side slopes were modified to help it blend with the surrounding natural contours. Once the new cell was completed, it was tested and put into service, so that relining work could be undertaken on one of the two existing asphalt-lined cells.

The improvements at Central Ferry State Park included the relining of an existing lagoon cell, upgrading the control piping and overflow between the two cells, and repairs to the spray irrigation disposal system. The side slopes in the existing cells were constructed at a steep (2 to 1) slope. After careful consideration of the options, we decided to leave the existing ACP liner in place, and install a geotextile pad between the ACP and the new PVC liner. On the side slopes, a geotextile pad was also placed over the new liner, adding resistance to sliding of the liner cover material. The deadline for the project’s start date was closely tied to the Commission’s budgetary restrictions. Century West responded to a tight time frame for design completion, and worked effectively as an extension of the Commission’s engineering staff.

Upriver Terrace Phase II Sewer Project; Spokane County, Washington

Century West provided design services for 13,300 feet of gravity sewer and 1,050 feet of pressure sewer main to serve 233 existing residents that were on septic tanks. The project included sewer mains, services, and roadway reconstruction over an area about 10 blocks square. Our services included preparation of plans; specifications, cost estimate, cultural resources survey, and evaluation of existing lift station in the area. We developed the design using computer modeling of sewer flows for pipe sizing and slope determination. We coordinated side sewer locations with property owners through mailers and a public meeting. We also provided bidding services which included responding to bidders questions and issuing addenda.

Vera Terrace Phase II Sewer Project; Spokane County, Washington

Century West provided design services for 10,000 feet of sewer mains in a 24 square block unsewered area of Spokane Valley. This project included providing sewer service to approximately 140 homes that are on septic tanks. The project included sanitary sewer mains and services, and roadway reconstruction improvements totaling over $1.5 million. Our services included preparing plans, specifications, and construction cost estimates for the project. The design was developed using computer modeling of sewer flows for main line sizing. We also provided coordination between Spokane Utilities and the City of the Spokane Valley, coordinated side sewer stub location with property owners, conducted a resident informational meeting, and provided bidding services. The project was on a very tight schedule and was completed efficiently and within budget.

Walnut Sanitary Sewer Project; Spokane, Washington

Century West designed 17,000 feet of sewer mains in an unsewered area in the Spokane Valley. This $1.7 million project for Spokane County Utilities involves roadway reconstruction, sanitary sewers, and side sewers for 310 homes. Design services include preparing plans, specifications, and construction cost estimates for the project, computer modeling of sewage flows, bidding services, and environmental permit applications. We also provided construction inspection services.

Wastewater Facilities Improvements Project; Reardan, Washington

Century West provided design and construction management services on this wastewater treatment project. This project included removing and land applying biosolids from three existing lagoons before regrading and installing a HDPE liner. Additional improvements included a new headworks facility with an auger style screening system, influent and effluent parshall flumes with ultrasonic flow measurement systems, composite wastewater samplers, UV effluent disinfection system, SCADA computer monitoring system, natural gas powered emergency generator and autodialer alarm system. The upgraded facility incorporates diffused aeration from a central 20-hp blower that minimized electrical costs and an attached growth passive media filter for ammonia removal.

During excavation of the lagoons, groundwater springs were encountered. A new underdrain system for each lagoon was added to the project to allow the groundwater and any gasses under the liner to escape. This drain system will prevent gas bubbles from forming under the liner, which has been a major issue in other recent lagoon rehabilitation projects.

The $2.1 million project will bring the Town’s WWTP into compliance with its NPDES permit. The project was funded by a Washington State Department of Ecology Centennial Clean Water Fund Grant and State Revolving Fund Loan, and Community Development Block Grant.

Wastewater Transmission and Disinfection Improvements; Davenport, Washington

Century West provided design, construction management, and inspection services for improvements to the City’s collection and treatment systems. The project included replacing the City’s sewage lift station that pumps all of the City’s wastewater to the treatment lagoons. Due to the wide range of flows as a result of infiltration and inflow this lift station was designed as a triplex submersible station. The project also included completing a parallel force main from the new lift station to the lagoons, a chlorination/dechlorination system for the treatment discharge to the creek, an operations building, and emergency generator. The project was completed with WSDOE Centennial Clean Water Funds.

Wastewater Treatment Plant Expansion; Liberty Lake Sewer and Water District; Liberty Lake, Washington

Century West provided design engineering services for the Liberty Lake Sewer and Water District for the expansion of this plant. The plant capacity was expanded from 1 MGD to 2 MGD capacity and converted to a biological nutrient and phosphorous removal method of treatment. Improvements were made to the headworks grit removal process. New facilities/structures include an aeration basin with anaerobic and anoxic sections, mixed liquor pump stations, two secondary clarifiers, a blower building and a sludge dewatering building. Sludge is now dewatered with the use of a new belt filter press and hauled off-site for disposal. The existing aeration basin was upgraded to be compatible with the new method of treatment. The existing equalization basin was converted to an anaerobic selector. Existing process piping was modified to accommodate new waste streams.

Century West also provided construction management services, which included submittal review, answering Contractor requests for information and clarification, special inspection of structural concrete and steel reinforcement, coordination of materials testing, and schedule monitoring. 

Wastewater Treatment, Reclamation and Recharge Facility, Airway Heights, Washington

Century West is providing design services for a new wastewater treatment facility in the City of Airway Heights. The treatment process will be an extended aeration activated sludge system with biological nitrogen and phosphorus removal. Final treatment will include membrane filtration to met Class A reclaimed water study areas. The treatment plant will provide reclaimed water to customers and for recharging groundwater.  Services provided include complete design, coordinating with the City, Department of Ecology, and Department of Health, establishing design criteria, obtaining permits, and completing environmental documentation.

The project is currently in final design and has received DOE/DOH approval. Our firm is assisting the City in obtaining the necessary funding, approximately $38 million to construct the facilities in 2010. 

Wastewater Treatment System Improvements; Fairfield, Washington

Century West designed improvements to the Town's wastewater treatment facility. The project included reevaluation of the Town's Facilities Plan and design of a new aerated lagoon and constructed wetlands treatment. The $1.8 million project includes a new aerated lagoon, 3.6 acres of constructed wetlands, conversion of the existing lagoon to a flow equalization basin, two lift stations, influent screening, and effluent disinfection. Century West also provided construction services.

Weatherwood / Owens Sanitary Sewer Project; Spokane Valley, Washington

Century West provided design services for 26,600 feet of sewer mains in a 13 square block unsewered area of Spokane Valley. This project included providing sewer service to approximately 490 homes that were septic tanks. The project included sanitary sewer mains, and services, and roadway reconstruction improvements totaling over $3.5 million. Our services included preparing plans, specification, and construction cost estimates for the project. The design was developed using computer modeling of sewer flows for main line sizing. We also provided coordination between Spokane Utilities and the City of the Spokane Valley, coordinated side sewer stub location with property owners, conducted a resident informational meeting, and provided bidding services. The project was on a very tight schedule and was completed efficiently and within budget.

Wicomico Beach Sewer Line Replacement, Liberty Lake, Washington

Century West is responsible for preparing plans, specifications, and estimates for the construction of approximately 2,150 feet of 8 inch PVC sewer pipe with new manholes, obtaining utility easements and temporary construction easements, a shoreline permit, and approval from the WSDOE. assist in bidding the project, including conducting the pre-bid conference. Bidders’ questions will be answered and addenda prepared as required. Century West will attend the bid opening for the project and recommend award of the project to the lowest responsive, responsible bidder and will also provide design support during construction.  

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