6 MG Pala Mesa Tank

IEC delivered a functional and cost-effective design of this reservoir project in a challenging hilltop location near Fallbrook in northern San Diego County. The IEC team also developed a demolition plan to remove on the site, and prepared an IS/MND and supporting technical reports for compliance with CEQA. 

Key design challenges related to the site's location above steep slopes (3:1 horizontal-to-vertical or greater) within 400 feet of existing San Diego County Water Authority (SDCWA) aqueduct facilities. In addition, pipeline pressures to the site were low because of the site's elevation. Low pressures within a portion of the existing pipeline system were mitigated by designing a new transmission main in a new alignment, combined with proper siting of the reservoir control valves. The layout of the new tanks and the reservoir inlet and outlet piping and valves achieved balanced hydraulics for reservoir following a large seismic event, the reservoir outlet valve was instrumented with an electric actuator and seismic saftey switch.

Because of the need for extensive earthwork adjacent to noise-sensitve rural residential land uses, construction noise was a key focus for environmental analysis. Other environmental challenges were addressed through design - for example, nighttime security lighting for the new facility was specifically designed to comply with County restrictions controlling fugitive glare in the area surrounding the Palomar Observatory. To offset increased runoff generated by extensive new hardscape at the site, the project will include a 0.5-acre-foot stormwater detention and water quality basin consistent with CASQA (California Stormwater Quality Association) design standards. As required by the current National Pollutant Discharge Elimination System construction general permit, the new site drainage and detention system will moderate offsite flows to pre-project levels. Construction of the new facility is expected to be completed in winter 2011.