Collection System

The District owns and operates nearly 9 miles of collection sewer referred to as the District Trunk Line. The purpose of this line is to allow for the collective transport of wastewater from the smaller municpal lines of the three member agencies to the final destination of the District’s Wastewater Treatment Plant. The Trunk Line was initially constructed as part of the original District design of 1963. It is comprised of sewer pipe ranging in size from 15-30 inches in diameter.

The pipe segments are primarily composed of either Vitrified Clay Pipe or Asbestos Cement Pipe. Due to the the naturally sloping coastal topography and owing to careful consideration and planning during the design phase of the collection system, the District’s collection system operates entirely as a gravity fed sewer. As a result, the District is not dependent upon the use of pumps at any point in the collection system to convey the wastewater. The result is reduced annual operating expenses which in turn are passed directly on to the District’s customers.

Annual average daily flow passing through the collection system is in the order of 2.9 million gallons per day with peak daily flows of approximately 3.16 million gallons per day. Routine video inspection of the entire system is performed every 4 years by means of Closed Circuit Television cameras (CCTV). The videos resulting from those inspections are reviewed by system engineers and accurate assessments are made of the system. System abnormalities and/or deficiencies noted within the collection system are ranked and prioritized, assisting in the development of short term and long term rehabilitation plans. In addition, the collection system is also cleaned on average every 4th year as part of the District’s preventative maintenance plan.