Water Conservation and Management

According to the Electric Power Research Institute, more than 75 percent of U.S. fossil and nuclear power plants use freshwater resources for "once-through" cooling. Once-through cooling systems, although they do not consume water, are the most water-intensive systems in the power plants.

PG&E has no power plants that use freshwater for once-through cooling. Like the other electric utilities in California, PG&E uses saltwater to supply the once-through cooling systems at two power plants. PG&E does use freshwater to support the internal operations of the plants, but this, by comparison, represents a much smaller volume of water. As discussed more fully below, most of PG&E's freshwater use is for non-consumptive purposes.

Water Use Statistics

¹ Net operating capacity in January 2009: Diablo Canyon: 2,240 MW; Humboldt Bay: 105 MW; Gateway Generating Station: 600 MW

² In 2010, PG&E is replacing its aging Humboldt Bay Power Plant with a high-efficiency 163 MW plant at the same site that does not use once-through cooling.

³ Freshwater sources were well water and creek water through June 2008 and are now solely well water for back-up and emergency purposes.

⁴ Gateway relies on a dry-cooled system and became operational in January 2009.

⁵ This figure represents the water supplied to 71 facilities managed by PG&E’s Corporate Real Estate Department for the 12-month period from October to September. These facilities represent the scope of operations covered by PG&E’s water reduction target in 2010. We expect to report water consumption from additional facilities in subsequent sustainability reports, consistent with our plan to encompass more facilities in our water reduction target.

⁶ These are estimated figures as PG&E only measures water withdrawal associated with once-through cooling.

PG&E owns and operates two power plants that use saltwater for once-through cooling to condense steam to water in the electricity generating process. Diablo Canyon is a 2,240 MW nuclear power plant with a maximum discharge limit of 2.5 billion gallons per day. Humboldt Bay is a 105 MW two-unit fossil fuel plant with a maximum discharge limit of 76 million gallons per day. The water discharge limits are set by the facilities' environmental permits.

In 2010, PG&E is replacing its aging Humboldt Bay Power Plant with a high-efficiency plant at the same site that does not use once-through cooling, which will leave the Diablo Canyon Power Plant as PG&E's only once-through cooled plant.

Because once-through cooling systems can adversely affect aquatic organisms in some circumstances, steps must be taken to ensure the protection of the surrounding aquatic ecosystem. PG&E closely monitors the marine environment at its Diablo Canyon Power Plant by conducting regular studies and sampling required under the plant's Clean Water Act permit. The marine studies at Diablo Canyon, ongoing since the mid-1970s, represent one of the largest databases of intertidal marine data in the United States.

In May 2010, California's State Water Resources Control Board adopted a new policy regulating the use of once-through cooling at existing power plants and establishing a compliance schedule to phase out once-through cooling at most facilities. The policy acknowledges the unique contributions of nuclear plants to both baseload power and meeting the state's greenhouse gas reduction goals, and allows for alternative compliance requirements for these facilities after a review of compliance costs and factors such as engineering and permitting constraints, as well as any adverse environmental impacts of a cooling tower installation. If the State Board allows a nuclear plant to comply through alternative requirements, the policy requires that the impacts of the plant be mitigated through projects that increase marine life near the facility.

For new generation projects, PG&E supports efforts to transition away from once-through cooling and is using alternative technologies that rely on air for cooling at its repowered and new facilities. For example, we are using new advanced reciprocating engine technology at the repowered Humboldt Bay Generating Station. Because this plant is cooled with air radiators using a closed loop liquid coolant, it requires minimal water use.

PG&E is using another dry cooling technology, an air-cooled condenser, at the Gateway and Colusa Generating Stations. The Gateway Generating Station went online in early 2009 and is a state-of-the-art 600 MW combined-cycle natural gas power plant that uses approximately 97 percent less water and discharges 98 percent less wastewater than a traditional “wet” cooled plant. The similarly designed 657 MW Colusa Generating Station will also use dry cooling and will be completed in 2010; it will also use a zero liquid discharge system that recycles wastewater.

PG&E also requested regulatory approval last year for two new, state-of-the-art natural gas-fired facilities in Contra Costa County, both of which would use dry cooling. The first is a 586 MW plant in Oakley that PG&E plans to purchase, own, and operate once it becomes operational in 2014. The second is a 719 MW peaker plant near Antioch to be owned by a subsidiary of Mirant Corporation. As part of the power purchase agreement for the new facility, Mirant agreed to retire two older existing boiler units that use once-through cooling before bringing the new plant online in 2013.

PG&E consumes some freshwater for the internal operations at the three power plants we own and operate. These operations are largely closed-loop systems, which minimizes the amount of water consumed. The systems draw from on-site well water and/or municipal water. Additionally, the Diablo Canyon Power Plant uses freshwater generated through seawater reverse osmosis. The freshwater is used to generate steam, cool auxiliary equipment, support fire water systems and supply drinking water at the power plants, among other uses. To ensure operational efficiency and maintain plant chemistry, we closely monitor these internal systems to ensure they are watertight, thus reducing consumptive use.

PG&E also purchases a significant portion of its delivered electricity from third-party suppliers. Some of this purchased electricity comes from conventional power generation facilities that use freshwater for once-through or other wet cooling technologies.

We also consume freshwater in our office buildings for kitchens and bathrooms, landscape irrigation and cooling towers associated with heating, ventilation and air conditioning systems. Our gas and electric transmission and distribution facilities consume freshwater as well for operation, maintenance and construction activities. These include washing electric circuit insulators, cleaning vehicles, suppressing dust, conducting pipeline and other underground drilling operations, as well as pipeline hydrostatic testing.

PG&E's hydroelectric power plants are largely non-consumptive. After water passes through turbines to produce electricity, it is returned to the river.

Of PG&E's 68 hydroelectric power houses, 24 are classified as “run-of-the-river.” This refers to hydroelectric plants that operate on water as it is available from the natural flow of a stream without the need for storing the water. The other units draw water from reservoirs. Some experts have begun to characterize the evaporation that naturally occurs from reservoirs as water consumption. PG&E will continue to monitor such reporting developments as we further quantify our water conservation and management efforts. Evaporation represents a small percentage of the total water that flows in the watersheds where PG&E operates hydroelectric facilities.

PG&E also uses water for energy storage to help balance daily variations in electric demand. The Helms Pumped Storage Project is located in Fresno County at a site more than 1,000 feet inside a solid granite mountain. With a total output of 1,212 MW, the facility alternately draws water from an upper reservoir to produce electricity when demand is high, and pumps it back when demand is low for reuse during the next high demand period.

Demonstrating a long-term commitment, PG&E set a five-year goal to reduce water usage in offices and service yards by 20 percent by the end of 2014, with 2009 as the baseline year.

In 2009, we reduced water use by 8 percent—or 8.1 million gallons—from the prior year at more than 70 offices and service yards, exceeding the 5 percent target. To achieve these reductions, we installed “smart” controllers for irrigation systems, replaced HVAC water treatment systems, added aerators on faucets and shower heads and installed low-flow toilets and waterless urinals at selected sites.

In 2010, we aim to achieve an additional 4 percent reduction by continuing to install smart controllers for irrigation, drought resistant landscaping, upgraded plumbing fixtures and additional water treatment systems. We also intend to engage employees in water conservation efforts.

It takes large amounts of energy to extract, treat and deliver water—and still more energy to use, collect and treat it after use. The CEC estimates that almost 20 percent of California's electricity demand is related to the use of water.

As a major focus of the program, PG&E collaborated with several water agencies to provide incentives to 11 high-use commercial customers—K-12 schools, universities, hotels, detention centers and commercial buildings—for projects expected to save more than 25 million gallons of water each year. Customers earned rebates from both PG&E and their local water agency by conducting water audits and then retrofitting laundry equipment, replacing commercial dishwashers, upgrading toilets and sinks and switching from potable water to recycled water for cooling towers and landscaping.

Working in partnership with the Santa Clara Valley Water District, PG&E also installed nearly 500 high-efficiency toilets in the homes of low-income customers, which is expected to save up to two million gallons per year. The pilot program also explored ways that new and emerging technologies can yield water savings at water utilities and assessed opportunities for investor-owned water utilities to adopt system-wide energy efficiency improvements.

As a next step, the CPUC is conducting studies to better understand how much energy is used to treat water before and after use, which will help assess potential new embedded energy programs for California's electric utilities.

In California, storm water run-off poses potentially significant environmental threats, with precipitation transporting pollutants into nearby lakes, rivers, wetlands and coastal water. Some of these sites are also home to sensitive plants and animals.

For PG&E, preventing storm water pollution associated with our operations is a high priority. As a result, we are implementing best management practices at construction sites to protect water quality, plants and animals. This includes using reusable fencing to prevent sediment from entering streams and waterways, setting up portable vehicle wash stations to prevent the spread of plant diseases and invasive weeds and installing biological exclusion fences to prevent sensitive species—such as the California red-legged frog and the California tiger salamander—from entering construction sites.

Last year, PG&E used reusable fencing at nearly 30 construction projects, making sure to clean the fencing between uses to avoid spreading plant diseases. PG&E used portable vehicle wash stations at targeted projects where it was especially important to control noxious weeds and the spread of plant pathogens. This included a major project in an ecologically sensitive area spanning Santa Clara and Monterey Counties, where PG&E raised and reinforced forty-three transmission towers and completed the associated reconductoring.

PG&E is also focused on best practices for managing storm water at its power plants, including those under construction. For example, during construction of our Humboldt Bay Generating Station, we are sending storm water to a hydrodynamic separator and then a bioswale before discharging into a waterway. Once the new plant is operational, storm water will be gravity-fed from a newly-constructed bioretention pond to a hydrodynamic separator designed for industrial operations, which will then release to the bioswale.

PG&E has also taken necessary steps to prepare for new state requirements that go into effect in mid-2010 for storm water management associated with construction projects. The new, more stringent requirements will call for PG&E to implement best management practices commensurate with a project's risk level to minimize potential impacts.