The EPA is considering authorizing the award of a Border Environment Infrastructure Fund (BEIF) grant to the Comisión Estatal de Servicios Publicos de Mexicali (CESPM), the local utility, for construction of a force main, pump station, new wastewater treatment plant (WWTP), and purchase of emergency pumping equipment.
Mexicali, a municipality of around 800,000 people, is located just south of Calexico, California in Baja California, Mexico.
Wastewater generated by the Mexicali II service area was originally intended to be treated at a proposed new wastewater treatment plant in El Choropo, but this plant was not built because of public opposition from local residents. Consequently, approximately 14-16 mgd of untreated wastewater continues to enter the New River. This river originates 20 river miles south of the border, and travels 65 river miles through Calexico and the Imperial Valley, before emptying into the Salton Sea.
The new proposal by Mexico is to build this Wastewater Treatment Plant in a relatively uninhabited area known as Las Arenitas, located approximately 20.6 miles south of the border. The pipeline, pump station, and WWTP will be sized to treat and convey 20.1 mgd to accommodate flows until the year 2014. A pumping station will be constructed, and 11.8 miles more pipeline will be installed, given the increase in distance to the new location of the wastewater treatment plant.
The treated wastewater will be discharged south of the New River drainage basin, into a tributary of the Rio Hardy, which empties into the Colorado River Delta. The wastewater will therefore no longer enter the New River. This will result in a reduction of flows to the New River at the border of about 11% and a decrease of flows into the Salton Sea of about 1%. This will also reduce total phosphorous and orthophosphate loadings to the Salton Sea by 10% and loadings of total suspended solids (TSS) and biological oxygen demand (BOD5) in the New River at the International boundary by over 40% and 60% respectively.