Municipalities throughout Washington State have called on BHC Consultants to provide the following Solid Waste services and solutions in response to a wide range of concerns and issues over the last decade. Below is a list of specific Solid Waste services offered. 

BHC Consulting provided civil engineering design services for the closure of Area 4 and development of a new 50-acre landfill cell (Area 5) at the Cedar Hills Regional Landfill. Services included the design and evaluation of both leachate collection and conveyance facilities and drainage management systems and conveyance facilities; assistance on the overall cell and closure system layouts; and design of construction and operation erosion controls.

 

A contaminated surface water lagoon and associated conveyance pipelines, manholes, and flow meters were designed to service Area 4 and future Areas 5, 6 and 7. Hydrologic and hydraulic analyses were performed to determine an appropriate size for the lagoon and the influent and effluent pipelines. Plans and specifications were produced for these facilities. Erosion and sediment control plans and specifications were also produced for the Area 4 closure. Construction services included on-site observations, submittal review and office engineering.

 

For development of Area 5, leachate and stormwater conveyance systems were designed to route leachate and stormwater from Area 5 to the existing leachate and stormwater conveyance facilities. An analysis of leachate generation rates and peak flows for all areas of the landfill was completed. Results of this analysis were used to model future leachate generation rates and peak flows for the landfill, including Area 5. The analysis determined whether the existing leachate and CSW lagoons provided enough storage volume, and identified operating requirements to prevent overfilling of the storage lagoons. Alternatives for conveyance of leachate and stormwater out of Area 5 were evaluated, including the use of forcemains, deep trench pipelines, and micro-tunnelled pipelines. A hydraulic analysis of the selected leachate forcemain and downstream conveyances was completed to identify needed improvements for these facilities.

 

After completing these evaluations, stormwater and leachate conveyance facilities were designed, including a triplex 50-hp pump station and forcemain for stormwater, and a duplex 34-hp pump station and forcemain for leachate. Improvements to existing leachate and CSW conveyance facilities were also designed to accommodate higher flows. Construction services included submittal reviews and production of pump station operation and maintenance manuals. Erosion and sedimentation control plans and specifications were also prepared for Area 5 and the main stockpiles for Area 5 development.

 

As a sub-consultant, BHC Consultants has assisted in the development, preparation, and publication of reports, technical memoranda, and drawings to support permitting requirements, construction projects, and landfill operations. The work included Engineering Reports, Construction Bid Packages, Operations Plans, and Quality Assurance and Control Plans.

BHC Consultants’ role in the design of the cell included 3-D modeling, planning for refuse placement, and modeling and design of collection storage, pumping, and conveyance facilities for contaminated surface water and leachate.

BHC Consultants participated in value engineering reviews and construction meetings throughout the project and provided engineering services for the development of Area 6 at the Cedar Hills Regional Landfill. Additionally, BHC performed preliminary conceptual designs, analyses, and evaluations to determine the configuration and layout of the leachate and contaminated stormwater collection and conveyance systems, and evaluated the leachate lagoon aeration system. The work also included the development of preliminary concepts and BMPs for erosion and sedimentation control measures for the excavation and construction of Area 6 and the soil stockpile.

BHC Consultants assisted in the development, preparation, and publication of reports, technical memoranda, and drawings to support permitting requirements, construction projects, and landfill operations. The work included Engineering Reports, Construction Bid Packages, Operations Plans, and Quality Assurance and Control Plans.

The liner over unlined refuse was completed in 2002 and was immediately put to use. The A5LOURA was the first lining system permitted under WAC 173-351 by Seattle-King County Public Health and WSDOE to be constructed over an existing refuse mound that was previously unlined. Our role included the development of a leachate collection and conveyance system that was designed to accommodate anticipated local and global settlement of up to 20 feet.