Water Supply System
The water supply for Bridgewater is comprised of three lakes. The surface of the lakes is approximately 13 km2; however, the natural watershed for these three lakes is approximately 92 km2, of which 56 km2 is designated watershed. The daily safe yield of the water of the lakes is approximately 57 000 cubic meters per day. The PSC’s maximum design flow is approximately 18 300 cubic meters per day.
Water pumped from the low lift pumping station via two transmission mains to the water treatment plant. The pre-treatment component of the water treatment process consists of the addition of potassium permanganate, lime, carbon dioxide, polymer, and alum, followed by mixing and flocculation in two parallel flocculation tanks. Two parallel gravity inclined plate clarifiers remove most of the chemically coagulated material. The clarifiers are followed by four multimedia rapid sand filters. Filtered water is disinfected in a chlorine contact chamber. To reduce corrosion in the distribution system the pH is adjusted with sodium hydroxide and a corrosion inhibitor is added. The treatment plant has a nominal design capacity of 18 000 m3/day in the summer and 14880 m3/day for the winter months.
The high lift pumps at the water treatment plant supply water to an existing distribution system through two transmission mains; a 300 mm cast iron main to the west Side Reservoir and a 350 mm ductile iron main directly into the distribution system. Two below grade in-ground concrete water storage tanks provide 3785 m3 each of storage for the distribution system to meet peak consumption demands and fire demands.
The distribution system within town consists of unlined cast and ductile iron piping installed in the early to mid 1900’s, Lined Ductile iron and transite installed in the 60’s, 70’s and early 80’s, and PVC installed in the past two decades. Pipe sizes range from 150 mm to 400 mm. In addition to the gravity system there are three boosted zones within the system to serve the areas of town that are located at a high section requiring the water pressure to be lifted.