SECTION 7.0

Water Supply

This chapter describes the source, quantity and quality of water required for process water, domestic water and fire water, and the storm and wastewater discharges for the Humboldt Bay Repowering Project (HBRP).

7.1 Water Supply and Use Raw process water for the HBRP is supplied from Pacific Gas and Electric Company (PG&E) Well No. 2 via the existing 6-inch raw water supply pipeline located within the project site. Because the Wärtsilä 18V50DF internal combustion engines are air radiator-cooled, they use very little water for cooling. Key plant process water uses include engine cooling systems (air radiators), closed cooling water system for auxiliary equipment, preheating for jacket water and engine turbocharger washing. Domestic water required for non-process uses (such as sinks, toilets, showers, drinking fountains, and eye wash/safety showers) will be provided from a new 1,200-foot-long, 4- to 6-inch water supply pipeline that will connect with an existing Humboldt Community Services District (HCSD) pipeline that runs along King Salmon Avenue. The new pipeline will be located under the temporary construction access road and extend from the existing pipeline in King Salmon Avenue to the HBRP site. The fire water tank can be filled from both the raw water and domestic water source. Initial filling and routine make-up will be from PG&E Well No. 2; emergency refill requirements will be met from the domestic water source. A will-serve letter from the HCSD indicating ability to provide domestic water and sewer service is included in Appendix 7A.

The reciprocating engine’s water consumption is minimal and does not vary with weather or load because engine cooling will be by closed-loop radiator (dry cooling) system. Cooling water from the engines circulates through tube bundles with fins that are cooled by air circulation provided by fans. The coolant is a solution of water and propylene glycol. The fans are controlled by frequency converters to minimize parasitic load and noise. Two shop-fabricated 2,600-gallon maintenance water tanks will be used to store treated engine coolant. The engine coolant systems are filled from the isolated maintenance water tanks. Any necessary treatment is done in the maintenance water tanks. During maintenance, the coolant is pumped back to the tanks to enable water recycling without discharge. Figure 7.1-1 shows the project’s typical use of water.

Peak operation of the HBRP occurs during the winter. Approximately 1.66 gallons per minute (gpm) of water will be required for operation. Peak load operation assumes that all 10 internal combustion engines are operating at 100 percent load. On an annual average basis, the HBRP is estimated to require, at 100 percent load, approximately 2.7 acre-feet/year of process water (1.66 gpm). This is approximately one four-hundredth (1/400) of the cooling and process water demand of the typical combined-cycle turbine generator power plant. HBRP potable water demands (domestic water system) for uses other than plant and industrial processes are estimated to average 0.11 gpm, less than 0.182 acre-feet per year.

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A new fire system will be used for fire fighting. The new fire system is connected to a new 150,000-gallon fire water tank.

7.2 Water Quality Table 7.2-1 describes the quality of the domestic water that will be supplied to the project. The plant receives domestic water from the HCSD South Bay Well. The source of the project’s raw water is PG&E’s Humboldt Bay Power Plant Well No. 2, which is located approximately 2,250 feet southeast of the project boundary along Humboldt Hill Road. Water is conveyed from this well to the project site via an existing 4-inch transite pipeline. Both of these water wells, PG&E and HCSD, provide water from the same aquifer and have similar characteristics.

TABLE 7.2-1 Summary of Average Water Quality Characteristics for HCSD South Bay Well and PG&E Well No. 2

Water Quality Parameter Project Process Water Supplya

Drinking Water Standard

Secondary Drinking Water

Standardb

General Parameters Alkalinity (as CaCO3) 56 no standard (mg/L) Total Dissolved Solids 130 1,500 mg/L 500 mg/L Turbidity 0.15 1-5 ntu Arsenic 2.2 0.05 mg/Lc Boronc ND no standard (mg/L) Cadmium ND 0.005 mg/L Calcium 5.7 no standard (mg/L) Chloride 32 500 mg/L 250 mg/L Chromium (total) 1.7 0.05 mg/L (0.1 mg/L) Copper (at tap) ND TTc action level 1.3 mg/L 1 mg/L Fluoride 0.12 2 mg/L 2 mg/L Iron 27 0.30 mg/L 0.3 mg/L Lead (at tap) ND TTd action level 0.015 mg/L Magnesium 8.6 no standard (mg/L) Manganese 13 no standard (mg/L) 0.05 mg/L Mercury (inorganic) ND 0.002 mg/L Silver ND no standard (mg/L) 0.01 mg/L Sodium 14 350 mg/L Sulfate 8.4 500 mg/L 250 mg/L Zinc ND no standard (mg/L) 5 mg/L

Source: U.S. Environmental Protection Agency. 2004. Drinking Water Standards and Health Advisories. Winter, 2004. a Data are from HCSD. All units are mg/L except for turbidity, which is in nephelometric turbidity units. b National Secondary Drinking Water Regulations (NSDWRs or secondary standards) are non-enforceable guidelines

regulating contaminants that may cause cosmetic effects (such as skin or tooth discoloration) or aesthetic effects (such as undesirable taste, odor, or color) in drinking water.

c Arsenic standard will change to 0.01 mg/L as of 1/23/06. Boron standard is under review. d TT = Treatment technique indicates that there is a required process to reduce the level of a contaminant in drinking

water. The action level for copper is 1.3 mg/L. For lead it is 0.015 mg/L mg/L = milligrams per liter

ND = non-detect ntu = nephelometric turbidity units

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FIGURE 7.1-1WATER BALANCE, NORMAL OPERATIONSHUMBOLDT BAY REPOWERING PROJECT

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SECTION 7.0: WATER SUPPLY

7.3 Cooling System Water Treatment Chemical water treatment occurs on only one system, the air radiator cooling system, and consists of adding a corrosion inhibiting propylene glycol solution to the maintenance water tanks. Engine cooling will take place using this air radiator (dry cooling) system. It is a closed-loop cooling system in which coolant (consisting of water and corrosion inhibitors) from the engines circulates through tube bundles with fins that are cooled by air circulation provided by fans, as in a conventional automobile engine. The engine cooling water circuits are filled from isolated maintenance water tanks. During maintenance, the coolant is pumped back to the tanks to enable recycling of the coolant without discharge. Two shop-fabricated maintenance water tanks will be used to store coolant, allowing one engine set to be drained for maintenance per tank.

In contrast with evaporative cooling systems which circulate and evaporate water, concentrating chemical constituents until the water must be discharged, the closed loop cooling system entails very little evaporation, and recycles the coolant repeatedly. For this reason, this system does not require the routine discharge of water.

7.4 Wastewater Collection, Treatment, and Disposal Water will leave the HBRP predominantly through three means: (1) waste process water, (2) waste domestic water, and (3) stormwater runoff drains. Water used for engine turbocharger washes (1.17 gpm) exits the engines as vapor.

7.4.1 Waste Process Water Drips from process water that has been used in engine cooling, liquid that has dripped from seals, condensate from compressors, and area wash downs will all be collected in a system of floor drains, hub drains, and piping and routed to two water collection sumps located outside of the engine house. All material which drains into these sumps will go to an oil water separator. The clean water will be discharged to the sanitary sewer system. The accumulated sludge will be removed by a licensed hazardous waste transporter and disposed of at permitted recycling facility or hazardous waste disposal site.

Each maintenance water tank is sized sufficiently to hold all of the engine coolant from a single engine. With two 2,600-gallon maintenance water tanks, two engines could be drained at the same time for maintenance work. This water can then be rerouted back to the air radiator cooling system at the completion of maintenance. Water collected from miscellaneous minor leaks will be sent to the water collection sumps. If the volume of this water needs to be reduced, then the coolant will be trucked off-site for disposal or recycling.

7.4.2 Waste Domestic Water Sanitary wastewater from sinks, toilets, showers and other sanitary facilities will be collected by gravity, discharged to Lift Station No. 3 and pumped to the existing sewer via a 4-inch-diameter piping system that serves the project site. The sanitary wastewater flow will average about 0.11 gpm (158 gallons per day).

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7.4.3 Stormwater Drainage There are two types of stormwater surface runoff associated with the HBRP project: (1) stormwater from project areas with tanks, equipment or activities that could potentially have oil or chemical contamination, requiring treatment prior to discharge; and (2) clean stormwater from plant areas not subject to contamination. Stormwater discharges from the existing Humboldt Bay Power Plant will continue to discharge at the current locations.

7.4.3.1 Stormwater from Area Drains Stormwater area drains in the lubricating oil and diesel tank areas will be collected in four water collection sumps. This sump water will routinely be checked for level and contamination (oil sheen or physical contamination) and periodically pumped to an oil water separator (OWS), if the water is contaminated. Water from these sumps which is not contaminated will be discharged to the plant stormwater drainage system. Clean water from the OWS will be discharged to the sanitary sewer system. Accumulated sludge will be removed by a licensed hazardous waste transporter and taken to a permitted recycling facility or hazardous waste disposal site. Stormwater from these sumps containing any cleaning chemicals or collected spills will be trucked offsite for disposals at an approved wastewater disposal facility.

7.4.3.2 Stormwater Surface Runoff Stormwater drainage areas on the HBRP site, which do not have equipment, tanks, or loading areas for oil or chemicals, will be collected in a new stormwater drainage system (separate from the area drain system) and discharged to a new discharge point southeast of the project. The storm drainage system includes catch basins for collecting stormwater and an underground piping system with manholes at all junction points and turns. An in-ground separator will treat stormwater runoff prior to discharge. See Section 8.2, Biological Resources, for a discussion of the use of this runoff to enhance wetlands adjacent to the site.

HBRP stormwater will be conveyed and discharged into the drainage system in accordance with 40 CFR Part 43 and the requirements of the Project’s General Industrial NPDES permit. Roof drains from the administration/control/maintenance building will discharge directly into a stormwater drainage system and will not flow over parking lots, ground slabs, etc. The inlets and outlets of culverts will be provided with permanent erosion protection.

The stormwater runoff system shall be designed and constructed in accordance with ASCE Manual No. 77, ”Design and Construction of Urban Storm Water Management Systems.”

Surface drainage systems inside the project will be sized to discharge the 10-year, 24-hour runoff without flooding roads and the 50-year, 24-hour storm event without flooding the project and equipment. (The storm events shall be as defined by U.S. Department of Commerce, Technical Paper No. 40, Rainfall Frequency Atlas of the United States, or local regulations if more stringent.)

The site plan in Appendix 7B shows plant drainage after construction and indicates how best management practices would be applied for stormwater. Plant drainage and stormwater discharge permitting is addressed further in Section 8.15, Water Resources.

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7.5 References U.S. Environmental Protection Agency. 2004. Drinking Water Standards and Health Advisories. Winter.

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