Background

In 2003, wastewater treatment was provided by three facilities that served the Old Bisbee, Warren and San Jose drainage basins. The Mule Gulch Wastewater Treatment Plant built in 1941 and serving Old Bisbee, was in violation of effluent limits for various toxic metals and was unable to meet its pollutant discharge limits on a consistent basis. The Warren and San Jose lagoons built in the 1970’s treated the wastewater from their respective areas. However, the Warren lagoons had no liners, and the liners in the San Jose lagoons were damaged, allowing untreated sewage to seep into the aquifer. Moreover, the collection systems in Old Bisbee and Warren were built in the early 1900's mainly using vitrified clay pipe and had reached the end of their useful life. A significant number of sewer back-ups and overflows were reported due to undersized and deteriorated pipes, root intrusion and other problems.

Project Scope 

The project consisted of replacing the existing treatment facilities with a new activated sludge plant with the capacity to provide preliminary, secondary and advanced treatment to meet the needs of the community for a minimum of 20 years. It also included rehabilitating or replacing approximately 146,847 linear feet of sewer lines with diameters ranging from 8 to 18 inches, in the most deteriorated sections of the collection system.

Benefits

Improvements to the wastewater collection and treatment systems addressed potentially serious human health and environmental problems by preventing pollution of surface and groundwater sources. Replacing and rehabilitating the sewer system reduced sewage back-ups and overflows, as well as corrected infiltration and inflow problems that were overloading the treatment facilities and adversely affecting the quality of the effluent. The project helped the City meet all regulatory requirements related to wastewater treatment in compliance with the State of Arizona Aquifer Protection Plan.