Summary

The Metcalf Energy Center will use about 3 to 4 million gallons of water per day. Ninety-five percent of this water will be used in the plant's cooling system. The other 5% will be used to supply highly-purified makeup water to the facility's heat recovery steam generators, to cool the air entering the combustion turbines in hot weather and for domestic uses by the plant workers.

In the Metcalf Energy Center Application for Certification, Calpine assessed the local surface and ground water conditions and supplies and evaluated the potential environmental impact of the project's use and discharge of water. Water resources that could potentially be affected by the Metcalf Energy Center include water supply, wastewater quality and flooding.

Water Supply

The Metcalf Energy Center's cooling water is recycled water supplied by the South Bay Water Recycling Program. This will minimize the plant's impact on water supplies in the North Coyote Valley area. Currently, the treated and disinfected water from the San Jose/Santa Clara Water Pollution Control Plant is discharged to the Bay. This fresh water is impacting saltwater plants and fish species by diluting the brackish water that supports the fragile ecosystem at the southern end of the Bay. Thc South Bay Water Recycling Program supplys water to the Metcalf Energy Center from the San Jose/Santa Clara Water Pollution Control Plant. The recycled tertiary-treated water is processed, treated and used in the Metcalf Energy Center's cooling tower where approximately 80% of it will evaporate into the atmosphere as water vapor. The remaining processed recycled water is then discharged to the San Jose sewer system. This approach significantly reduces the current impacts of fresh water discharges to the Bay while minimizing the plant's demands on other fresh water sources.

The remaining 5% of the water required by Metcalf Energy Center will be obtained from the San Jose Municipal Water District. San Jose Municipal Water District provides groundwater to its customers from its groundwater wells in the northern Coyote Valley. Metcalf Energy Center's non-cooling tower needs are comparable to the water demands of a medium-size restaurant. Preliminary studies indicate that the groundwater basin has sufficient capacity to supply the non-cooling water demands. In addition, withdrawing some groundwater from northern portion of the Coyote Valley may reduce flooding that can occur during wet winters because of high groundwater levels. Therefore, the fresh water demands of the Metcalf Energy Center will not have a significant adverse impact on the area's water supply.

Wastewater Quality

The industrial wastewater produced by the Metcalf Energy Center is returned via the San Jose sewer system to the Water Pollution Control Plant for treatment. The Metcalf Energy Center's industrial wastewater consists of the discharge from the cooling tower, effluent from the non-cooling water uses and very small amounts of non-toxic chemicals added to control corrosion and fouling of piping and heat exchangers. City staff has evaluated the quantity and composition of Metcalf Energy Center's industrial wastewater and have determined that it will be acceptable for blending with other wastewater received by the Water Pollution Control Plant. Once treated, it will either be discharged to the Bay or return it to SBWR's recycled water distribution system for reuse. Metcalf Energy Center's industrial wastewater will therefore not produce an adverse impact on water quality in the area.

Flooding

The City of San Jose requires that the project detain all storm water from a 25-year storm. Site drainage from stormwater will be routed to a retention basin capable of holding the site runoff from a once-in-100 years, 24-hour duration storm event. Basin overflow will be pumped or gravity-drained into Fisher Creek. Detained stormwater will also be pumped out or gravity-drained into Fisher Creek after the storm subsides and the suspended sediments have settled in the detention basin. Operators regularly test the water to ensure purity.

There is a history of flooding in the general North Coyote Valley because of shallow groundwater. However, the system of levees and channelization of Coyote and Fisher Creeks acts to prevent flooding at the MEC site itself, even though flooding is common moving upstream. The FEMA flood zone maps show that the MEC project site is outside the 100-year flood boundary. Therefore, no significant adverse impacts to flooding are anticipated from construction and operation of the MEC project. In fact, proposed groundwater for non-cooling tower uses are anticipated to benefit local flooding potential.