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  In 1990, the Town of Thomaston initiated a wastewater system improvement program, the essence of which was to improve the water quality of the St. George River by the elimination of combined sewer overfIows (CSOs) in the sewer system and to improve the compliance record of the treatment facility. The Town began an aggressive sewer replacement program in an effort to eliminate the CSOs. The Town retained Wright-Pierce to conduct an evaluation of the existing treatment plant to determine the scope of work necessary to upgrade the plant to meet the current and future needs of the Town.

   In 1992, the Town determined it was in its best interest to construct a completely new treatment facility. The Town and the Maine Department of Environmental Protection (DEP) agreed to evaluate alternatives that would eliminate the existing discharge to the St. George River. The St. George River is a very productive shellfish area, and by eliminating Thomaston's wastewater discharge, much of the area previously closed to shellfishing could be opened. It was determined that complete elimination of the river discharge was not economically feasible.

    The Town and the DEP worked together to develop an alternative that fit within the available funding and would utilize land application of treated effluent for as much of the year as possible (May through October) and discharge to the river only in the months of January, February and March when much of the river is typically frozen and less accessible for shellfishing. The total area with suitable soils for land application was limited at the proposed treatment site, however those soils present would allow a spray application rate of three inches per week (twice the typical rate in Maine) which made the alternative feasible. This alternative would ultimately allow those areas of the St. George River currently closed to shellfishing to be opened for approximately nine months each year.


    By the end of 1997, the new pumping stations began transporting Thomaston's wastewater to the new treatment facility culminating a 7-year process to upgrade their wastewater collection system and replace their 30-year old treatment plant.
 

New Facilities


    In 1991, the Town began a sewer replacement program to reduce the amount of non-sanitary (stormwater and groundwater) flows in their sanitary sewer system. By the end of 1997, the Town had replaced approximately 36,500 linear feet of gravity sewer pipe and associated sewer services to each building, and installed five new pump stations with approximately 7,100 linear feet of force main pipe. Through this effort, the Town has eliminated all of its CSOs and no longer discharges untreated wastewater to the St. George River during rainstorms.


    The new wastewater treatment facility also went on-line at the end of 1997. The treatment facility consists of three aerated facultative treatment lagoons constructed in series with a total capacity of 21 million gallons. The treatment lagoons are followed by a storage lagoon with a capacity of 36 million gallons. The facility is designed to treat an average daily flow of 427,000 gallons per day. Aeration is provided to the treatment lagoons via three blowers, air distribution piping, and 98 fine-bubble tubular membrane diffuser assemblies.

    The treated effluent from the lagoons is disposed of in one of two ways. In January, February and March the effluent is disinfected with sodium hypochlorite and discharged by gravity through 7, 100 linear feet of pipe to the St. George River via the outfall pipe at the old treatment plant. From mid may through October, the effluent is land applied by a spray irrigation system consisting of two 75 Hp spray pumps, approximately 26,000 linear feet of distribution piping, and 130 spray nozzles. The land application area is divided into five fields, each consisting of approximately ten acres. The effluent is applied to one field at a time, with each field being used one day each week. Between the river discharge period and the land application season, the treatment lagoon effluent is stored in the storage lagoon. The 78-foot x 40-foot operations building at the treatment facility includes a control room, laboratory, blower room, chemical room, pump room and a garage.
 

Funding


    The total cost of the project, which began in 1991, was $12.2 million, including construction, land acquisition, administration, and technical services. The total construction cost was approximately $8.5 million. The project was funded by state and federal grants and loans from the Department of Environmental Protection (DEP), the Rural Utility Service (RUS), and the Maine Municipal Bond Bank (MMBB) as summarized below.