Thursday, April 2, 2015

Catalina Island Wastewater

Wastewater service on Catalina Island is provided by the United Water Company in Avalon, and by Two Harbors Enterprises in the Two Harbors community. Outside these areas, the property owner or leaseholder is responsible for disposing of wastewater.  The Avalon Wastewater Treatment Facility (AWTF) receives freshwater and saltwater used indoors. To protect Avalon Harbor, the plant treats dry weather surface runoff, which is pumped from the storm drain to the treatment plant via a low flow diversion system.  The plant has an average dry weather design treatment capacity of 1.2 million gallons per day (mgd). Peak demand occurs on rainy days when the plant is pushed to its capacity. Peak dry weather demand in Avalon typically occurs on the 4th of July weekend, with 0.8 mgd in 2003. By comparison, the annual average daily discharge was .56 mgd in 2000. In Two Harbors, the Two Harbors Sewage treatment plant has a design capacity of 57,000 gallons per day. Peak demand occurs the first weekend of October when the area hosts its Buccaneer Days festivities.[1]

Between Yellow Building and Blue Tanks

             The Avalon Wastewater Treatment Facility (AWTF) is owned by the City and operated by United Water Company, under contract to the City. The AWTF is located in the industrial area of Avalon on Pebbly Beach Road. The treated wastewater is discharged into the Pacific Ocean through an outfall 400 feet off Pebbly Beach at a depth of 130 feet below the surface.  Raw sewage is pumped from the City to the AWTF through two lift stations. The waste flow is unique in that it is approximately 40-50 percent salt water due to the use of saltwater for toilet-flushing in Avalon. Wastewater at the plant is treated through a rotating screen for removal of large particles, a trickling filter and activated sludge reactors. The effluent is chlorinated, and solids are separated. Sludge is dried before being hauled to a landfill.[2]

            The Island Company owns and, through its subsidiary Two Harbors Enterprises, operates the Two Harbors Sewage Treatment Plant one-quarter mile south of the town of Two Harbors. Sewage treatment consists of aeration in two small treatment plants. Sludge generated in these plants is dried and barged to mainland landfills. Effluent from the treatment system is chlorinated, pumped into a concrete holding pond, and used for spray irrigation and dust control.  The treatment plants have a capacity of 57,000 gallons, and the holding pond has a capacity of 270,000 gallons.[3]

[1] [2] [3] Santa Catalina Island Final Municipal Service Review, Prepared by Burr Consulting, May 4, 2004, p. 48 & 50