Stormwater Treatment and Conveyance Projects by Century West Engineering
Stormwater Treatment and Conveyance Projects
Alder Basin Sewer Reconstruction Project; Bureau of Environmental Services, Portland, OR
Century West led the team for the design of pipes and a concrete diversion structure to collect and transport combined sewer flows in southeast Portland along SE Hawthorne Boulevard, SE 14th Avenue and SE Taylor Streets. The project included over 2,000 feet of concrete pipe ranging in size from 36-inches to 96-inches in diameter and 2,000 feet of 48-inch cured-in-place pipe with a total construction cost of over $3 million. Extensive coordination was necessary with US West to facilitate the relocation of multiple transmissions conduits within SE 14th Avenue to provide sufficient vertical and horizontal space for installation of the large diameter sewer pipe. Construction sequencing to provide alternative access to businesses and Tri-Met business routes within the project area, and the presence of contaminated soils generated by migration of liquids from underground storage tanks were project challenges addressed by developing stage construction solutions and contract provisions specifying construction requirements for contractor’s handling of disturbed soils.
Browne’s Mountain Stormwater Management Plan; Spokane County, Washington
Browne’s Mountain is an area within Spokane County that has been developed in the past 10 years without adequate stormwater management planning. Storm sewers were constructed in the upper portions of the developments that were discharged to the street surface part way down the mountain. This caused severe flooding and property damage to residents and streets.
Century West provided a plan for the area that evaluated various alternatives for managing the stormwater runoff from these developments. Capacity restrictions in a drainage ditch at the bottom of the mountain required that detention structures be included in the plan. The drainage basins were identified using County GIS information and computer modeled using both HEC 1 and HYDRA to determine storm hydrographs and peak flows. Storm sewers were sized to collect runoff and two alternative stormwater detention ponds were evaluated. Century West used results from the HEC 1 model and the computer model Pond-2 to determine required pond sizes. Cost estimates were developed for each alternative and recommendations were made for type and size of facilities and project phasing.
Clarke Avenue Stormwater Improvements; Liberty Lake, Washington
Century West surveyed, designed, and wrote bid documents for this 4-block post-development stormwater handling project within the Liberty Lake Watershed. Layout of stormwater improvements was complicated by steep slopes, limited right-of-way, and existing improvements.
Colfax Golf Course; Colfax, Washington
Century West assisted the City in acquiring FEMA and FCAAP funding for repair work in the golf course. Repairs included river bank replacement and stabilization along the Palouse River. Banks were severely damaged from 1996 spring flooding. Century West developed design alternatives and assisted the City in obtaining hydraulic and shoreline permits.
Combined Sewer Overflow (CSO) Reduction; Spokane, WA
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.
Highway 212/224 Stormwater Improvements; Water Environment Services, Clackamas, OR
Century West provided professional services for the design and construction of a stormwater system to provide pollution reduction and increase system capacity in the Cow Creek drainage basin. The project included the design of a pollution reduction facility (settling pond), 4,000 feet of 60-inch stormwater piping, plus an outfall to the Clackamas River. A study was performed to select the site and design for the pollution reduction facility based on property available, existing soils, groundwater, elevation requirements, expandability, land uses and expected pollutants, and downstream water resources. The project involved close coordination with Clackamas County and private landowners regarding pipe alignments and easements. Also, meetings were held with local citizens and businesses to discuss the project and temporary construction impacts.
Liberty Lake Stormwater Management Plan; Liberty Lake, Washington
The Liberty Lake Watershed encompasses 19 square miles in eastern Spokane County. Surface flows within the watershed ultimately drain into Liberty Lake, while underground flows percolate into and act as a recharge area for the Spokane-Rathdrum Prairie Aquifer. Steady population growth within the watershed led to deterioration of lake quality, until a sanitary sewer system constructed in 1982 reversed the trend. Subsequent growth necessitated a plan to maintain and preserve water quality within the watershed. With funding from a Washington State Centennial Clean Water Grant, the Liberty Lake Sewer District retained Century West to develop this stormwater management plan. Major elements of the plan include:
- Identification/mapping of the watershed.
- Evaluation of water quality conditions
- Identification of water quality problem sources
- Strategies to control water quality
- Identification of flood hazards and effects
- Strategies to control flooding
- Overall evaluation and monitoring plan
The goals of the plan are to reduce point source and non-point source pollutant loads being discharged into receiving waters, and to reduce the damages caused by flooding and inadequate flood hazard management. By setting and meeting water quality standards, beneficial uses within the watershed will be protected or restored.
Meek Street Storm Improvements- Phase I-II; City of Milwaukie, OR
Century West provided construction engineering services in 2004 for installation of approximately 800 feet of 36” diameter ADS storm drainage pipe as part of their CIP program to relieve flooding problems in the near Harrison Street. The work included weekly site visits and coordination of revisions to the alignment based unforeseen conditions in the field. All pay requests and change orders were also processed for the City.
Off-Road Vehicle Park Erosion Study; Spokane County, Washington
Century West provided an evaluation and preliminary design for improvements to the County’s Liberty Lake ORV Park. ORV pathways and areas of heavy use are experiencing severe erosion and silt migration into Liberty Lake. Century West developed and sized detention ponds, berms, and channels to disperse stormwater and reduce erosion in the park. The study provided recommendations to restrict use of the park and a revegetation plan.
Pend Oreille River Bank Stabilization; Cusick, Washington
Century West provided design, permit applications, and construction management services for this river bank stabilization project. The project included developing alternatives to stop severe river bank erosion in two locations along the river. This erosion was causing a hazard to an existing roadway that was located on top of this 12-foot high bank. A rock gabion wall was designed and constructed along one area that was eroding into the shoulder of the roadway. The second area that represented a lesser risk was stabilized utilizing large boulders and natural vegetation. Century West applied for and obtained all necessary permits including HPA, Corps of Engineers, SEPA, and shore lines.
Port of Portland – Terminal 6 AWC Expansion Phases 1 & 2, Portland, OR
Century West
recently completed the design of improvements for two auto
storage yards at the Port of Portland’s Terminal 6 (T6)
encompassing a total of 45 acres. The improvements include
surfacing of the entire 45-acre auto storage area, fencing,
landscaping, and lighting. In order to deal with the large
volume of stormwater runoff that would be generated from 45
acres of impervious surface, the design utilized a porous
pavement system and a series of vegetated swales to infiltrate
100% of the stormwater on site. The majority of the paved
surfaces will be porous pavement. Traditional impervious
pavement was used in some areas to balance the cut and fill on
the site and in areas where additional structural capacity was
required. The runoff from the traditional pavements will be
infiltrated through on site swales that are incorporated into
the landscaping for the site.
The use of onsite infiltration methods allowed for a significantly shortened design and permitting process that made possible construction during the 2006 construction season by avoiding the need for US Army Corps of Engineers or Oregon Division of State Lands permits for an outfall to the Columbia River. The use of porous pavement also allowed the Port to avoid City of Portland stormwater fees that are calculated by the area of impervious surface on a site. In addition to the cost and time savings, the porous pavement and infiltration swales provide filtering of the stormwater and mimic the predevelopment hydrologic cycle which provide improvements to the overall water quality in the vicinity of the site.
The Oregon Chapter of the American Public Works Association (APWA) awarded the Julian Prize for Sustainability for Public Works to the Port of Portland for the T6 AWC Improvements project. The Julian prize is awarded to people, projects, and practices to recognize excellence in systems thinking, long term design practices and infrastructure systems in public works that further sustainability.
Ramsey Blvd. Storm Sewer; Port of Portland, OR
The project included planning and design services for approximately 7,000 feet of storm sewer ranging in size from 21-inch to 72-inch in diameter. The 230 acre industrial site at Rivergate involved stormwater modeling to determine flow, pipe sizes and assess the risk of the system being surcharged due to flood stages in the Columbia River and the slough.
St. Johns A CSO Project; Bureau of Environmental Services, Portland, OR
The project included approximately 30,000 lineal feet of storm sewer ranging in size from 12-inch to 42-inch in diameter. The project removed storm flows from a combined sewer system in the St. Johns area of the City of Portland. A hydrologic and hydraulic computer model was run on the basin to determine design flows and the size the pipes.
Stormwater Erosion Mitigation; Electric City, Washington
Century West provided design, permit applications and construction management services for this erosion control project. Several areas along the edges of Banks Lake were eroding from concentrated stormwater runoff from SR 155 and other town streets. Century West evaluated alternatives for improvements to reduce this erosion and flooding of residents. A stormwater collection system and treatment pond was designed and constructed. The pond was sited in an existing drainage channel and was designed to reduce the flow of stormwater and treat it prior to discharge into the lake. The channel was partially armored with riprap and berms were placed to reduce flow velocities and the resulting erosion. Natural grasses were planted in the pond and channel to further reduce erosion. Century West worked closely with WSDOE, Corps of Engineers, Bureau of Reclamation, and the Town to obtain all of the necessary permits, easements, and approvals to construct the facilities.
Sutters Phase 3 Sanitary Sewer Project, Spokane County, Washington
Century West provided design services for 17,250 feet of gravity sewer to service 236 existing residents that are currently on septic tanks. The project included sewer mains, services, and roadway reconstruction over an area that is about 10 blocks square. Our services included preparation of plans, specifications, cost estimate and a cultural resources survey. We developed the design using computer modeling software to determine the ultimate 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 include responding to bidders questions and issuing addenda.
White Birch Sewer Project, Spokane County, Washington
Century West provided design services for the White Birch Sewer Project for the Spokane County Utilities Division. This project consisted of design of approximately 14,000 linear feet of gravity sewer to service 193 existing residents that are currently on septic tanks. The project included sewer mains, services, and roadway reconstruction over the project area. Our services included preparation of plans, specifications, cost estimate and a cultural resources survey. This project may also involve the design of a sewer lift station for a portion of the sewer basin as well as a portion of the adjacent Green Haven Sewer Basin. As part of the design, we utilized computer modeling software to determine the ultimate sewer flows for pipe sizing and slope determination. We coordinated side sewer locations with property owners through mailers and a public meeting. We are also provided bidding services which include responding to bidders questions and issuing addenda.
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