As part of the District’s 10-year plan which began in 1999, a facility plan to cover the North Berkeley Area was completed in 2002 in response to increased development in the study area. This new development was causing stress on the limited existing wastewater collection and treatment facilities in the area. In addition, onsite sewer disposal systems within the area are ineffective due to improper construction or poor soil conditions, causing partially treated or untreated wastewater to be discharged into the County’s groundwater supply and surface waters according to USGS and DEP studies. The Phase I area is part of the District’s larger North Berkeley Area Facility Plan. The Phase I project covers the higher density areas primarily around the I-81 and Route 11 corridors in the Bedington and Spring Mills area.
The basis of the Phase I system configuration follows the District’s philosophy of constructing an infrastructure “backbone” along the major highways in the county to serve the current customer base in the pocket areas of development. This will immediately provide public sewer facilities to the high density areas that are in most need and also provide public facilities for extension by private development in the areas dictated by market demand and land availability. This philosophy maximizes public resources, helps control user fees, provides the necessary public facilities and eliminates construction of costly sewer extensions to currently underdeveloped areas of the county.
The project is planned to go to bid in Fall/Winter 2006. Construction of project would begin shortly thereafter with a one year construction period. The system is planned to begin operation in Winter of 2007.
Collection System
The Phase I project service area contains approximately 2,530 total equivalent customers as of 2003. This includes existing BCPSSD customers tributary to the Spring Mills Wastewater Treatment Plant. The total new equivalent customers included in the Phase 1 project area are 2,013 as of 2003. This number excludes the existing BCPSSD customers in the Phase 1 project area. The proposed gravity collection system contains approximately 150,000 linear feet of various diameter gravity sewer, 800 manholes, 37,000 linear feet of force main, 14 pump stations and miscellaneous other improvements. Seven (7) existing package sewer treatment plants are proposed to be eliminated by the Phase 1 project totaling approximately 317,900 gallons per day of permitted point source discharges into area streams. The estimated construction cost for the collection system is approximately $17,830,000.
Treatment System & Process
A Sequencing Batch Reactor (SBR) biological type wastewater treatment plant with a capacity of 1.0 million gallons per day (MGD) average daily flow and 3.25 MGD peak hourly flow will be constructed on a site located east of the Opequon Creek along with an effluent discharge into the Opequon Creek. An SBR system receives the raw wastewater directly into the treatment basins similar to other aerobic extended aeration processes except that the flow is not a continuous flow through, but is handled in a batch process typically cycled between multiple basins. One basin will fill with influent wastewater, a separate basin will aerate accumulated sewage for biological treatment. Following the aeration cycle, the aerated basin is then allowed to settle for a predetermined period of time and then clear water is decanted from the top level of water within the basin. BOD removal, nitrification, denitrification and solids reduction are all accomplished within a single treatment unit. This eliminates the need for a separate clarifier, sludge return equipment and scum removal devices resulting in a more compact unit size and reduced energy requirement. The SBR process is also able to handle variations in inflow rates due to the batch sequence allowing diversion of flows between basins without increase in flow through velocities, which would result in carryover of solids. A post flow equalization basin is also being constructed to equalize the peak flows experienced. This post EQ basin is intended to aid in dampening the effects of the decant cycle from the SBR reactor in order to avoid over sizing or flooding the proposed UV disinfection system.
Primary treatment will consist of mechanical fine screening and grit removal units. Secondary or biological treatment will occur in the SBR unit as previously described. The waste stream will then be processed through an ultraviolet light disinfection system, followed by mechanical or cascade post aeration prior to effluent discharge into the receiving stream. The solids wasted from the SBR process will be digested in an aerobic sludge digestion tank with solids dewatered through a belt filter press. The sludge cake can then be hauled to a landfill for disposal or land applied.
The estimated construction costs for the 1.0 MGD SBR is approximately $5,272,000. The total estimated project cost for Phase I including all non construction capital costs is approximately $28,626,500.