Operational Hazards
The power generating units are designed and built to operate using coal as the primary fuel. The units rely on rotating equipment, a ready supply of fuel, cooling water, and routine maintenance. Rotating equipment requires lubricating oils, and routine maintenance includes activities using various solvents and other hazardous materials. Fuel supply is provided from a coal slurry pipeline network with inventories maintained on-site.

The operation and maintenance of the units also requires the use of various hazardous materials for pretreatment of boiler feed water and cooling water and for the management of waste streams resulting from operations and maintenance. The electrical energy emanating from the generating station into the power distribution grid is a source of electrical and magnetic fields (EMFs). Transformers are also found on-site and contain oil that is documented to have less than 50 parts per million (ppm) of polychlorinated biphenyls (PCBs) but were reported to have contained greater PCB concentrations prior to 1976.

The use of hazardous materials presents the potential for release of those materials to the environment. Table 4.7-1 lists the hazardous materials used at the MGS. More detailed information on inventories, storage tank capacities, and storage locations are available from the MGS’s Hazardous Materials Inventory Statement (HMIS).

Existing Safeguards
The risk of operational hazards (e.g., spills, fires, or upsets) is reduced through design, operational, maintenance, regulatory, and administrative controls. Design standards are developed through industry groups, independent institutes, and government agencies. Operational controls include automatic devices to control and monitor process variables and documented procedures for manual operations. Routine preventative maintenance and inspections of critical equipment help to prevent unscheduled process shutdowns and potential equipment failures. Administrative controls include operator training, documentation of equipment inspection and maintenance history, and procurement of prequalification controls over contractors and vendors.

Table 4.7-1: Hazardous Materials of Concern

Hydrocarbons	Hazardous Substances Non-Hydrocarbon	Hazardous Wastes
Mineral Oil	1,1,1 Trichloroethane	Asbestos
Waste Oil	Acetylene	Arsenic
Gear Oil	Ammonia	Chromium
Lube Oil	Ammonium Sulfate	.
Motor Oil	Bromochlorodimethyhydrant	.
	Dichlorodimethylhydantoin	.
Gasoline	Lime (Calcium Oxide)	.
Petroleum Distillate	Coal	.
Natural Gas	Dichlorodiflouromethane	.
Petroleum Naphtha	Hydrochloric Acid	.
Diesel	Hydrogen	.
.	Hydrazine Mercury Methyl ethyl ketone (MEK) Nitrogen Oxygen Rubber Sodium Hydroxide Sulfuric Acid Asbestos Polychlorinated Biphenyl Arsenic Chromium	.

SOURCE: SCE 1999

The following administrative and engineering controls are in place at the MGS.

Hazardous Materials Inventory Statement. The Hazardous Materials Inventory Statement (HMIS) focuses on hazardous materials and hazardous wastes and their management, documents the reportable quantities in the event of a spill, presents a hazard evaluation of chemical storage and mixing areas, and provides chemical and waste inventories and storage locations. Specific response actions are prescribed for releases of several hazardous materials.

Station Order O-6. Station Order O-6 focuses on oil products and hazardous substances and their management. The order includes the facility spill response procedures, a listing of chemical storage tank capacities, reportable quantities in the event of a spill, and an inspection form for Resource Conservation and Recovery Act (RCRA) and 1990 Federal Clean Water Act (CWA) compliance.

Accidental and Fire Prevention Manual. The Accident and Fire Prevention Manual implements OSHA’s injury and illness prevention requirements and includes a review of potential hazards that employees may encounter at the facility. The manual identifies preventative measures for injury or illness related to hazards, such as chemicals, elevated temperature, noise, and physical hazards.

Hazardous Materials Inherent to Facility Equipment

Chemical Hazards. Based on a review of the results of the draft Phase I Environmental Site Assessment (HSI-Geotrans 1998), PCBs and asbestos-containing materials (ACMs) exist and are recognized as environmental conditions at the facility. Included below is a brief description of the potential health risks from exposure to these compounds if they are disturbed or removed.

Based on the mechanism of release, the potential exposure pathways to humans from these materials would be inhalation of volatile compounds, fugitive dusts, or particulates; skin absorption; incidental ingestion; and/or direct skin or eye contact. The risks to human health from each of these potential pathways depend on the contaminant concentrations, route, and duration of exposure.

Polychlorinated Biphenlys. PCBs are a group of man-made organic chemicals that contain over 200 individual compounds with varying harmful effects (ATSDR 1993). PCBs have been used as coolants and lubricants in transformers and other electrical equipment. PCBs in air can be present as both solid and liquid aerosols and as vapor. A small amount of PCBs may dissolve in water, but most tend to bind to particles and sediments. In addition, PCBs bind tightly to soil and tend to remain there for several years.

Potential human exposure to PCBs may occur through inhalation of contaminated air and through direct contact with contaminated soils, resulting in irritation. Studies of workers exposed to PCBs do not provide conclusive evidence for the risk of cancer; however, the International Agency for Research on Cancer and the USEPA have determined PCBs to be probable human carcinogens (ATSDR 1993).

Asbestos-Containing Materials. Asbestos fibers do not evaporate into air or dissolve in water (ATSDR 1994); however, pieces of fibers can enter the air and water from the demolition or wearing down of man-made asbestos products (e.g., insulation, roof shingles, and tiles). Small fibers and fiber-containing particles may be carried long distances by wind or water currents before settling. Asbestos fibers are not able to move through soil and are not broken down to other compounds in the environment.

Potential human exposures to ACMs may occur by inhaling asbestos fibers suspended in the air (ATSDR 1993). Fibers either are deposited in the air passages in the lungs or are removed from the lung by coughing. Asbestos fiber buildup in the deepest parts of the lung can lead to scar-like tissue buildup, resulting in difficult breathing and decreased blood flow to the lungs. This condition manifests itself over a number of years and can eventually lead to disability, cancer, or death in people exposed to high levels of asbestos.

Current EMF Profile
The following information was summarized from two documents: (1) an SCE employee information brochure entitled Southern California Edison, Questions and Answers EMF: Electric and Magnetic Fields in the Work Environment (SCE 1994); and (2) a review document entitled Electric and Magnetic Fields and Human Health, A Review of the Issues and the Science (Sahl and Murdock 1995).

EMFs naturally result from the use of electricity: electric fields from voltage and magnetic fields from current. Both electric and magnetic fields quickly diminish as distance from the source increases. EMFs result from electricity flowing through transmission and distribu-tion lines, transformers, generators, and other electrical equipment and appliances. In the electric utility work environment, people who work closely to energized equipment tend to have higher exposures to EMFs. At substations, the highest magnetic fields are near underground cables and circuit breakers. At generating stations, the highest magnetic fields are near high-current bases, switch-gear equipment, and cable-feeding auxiliary equipment.

Health research on EMFs is generally of two types: epidemiology studies and laboratory experiments. The results of epidemiological studies over the last 15 years concerning diseases (e.g., cancer) related to EMFs are not always consistent and are often contradictory. Most scientists familiar with EMF research conclude that the evidence linking these fields to cancer is insufficient to conclude that a hazard exists. Laboratory research has shown some biological effects; however, these effects have not been shown to be harmful, and no link has been established between them and the increased incidence of cancer reported in some epidemiology studies.

A report released in September 1989 by the California Department of Health Services (DHS) and the CPUC concluded that evidence is insufficient to determine that a health risk exists or to speculate about safe or unsafe levels of EMFs (SCE 1994).

Surface and Subsurface Contamination and Associated Potential Human Health Risks
The draft Phase I Environmental Site Assessment (HSI-Geotrans 1998) identified four primary categories of hazardous materials as potential contributors to surface and/or subsurface contamination:
• Total petroleum hydrocarbons (TPH) (primarily in oil storage tanks and power block areas),
• PCBs (primarily in transformer areas);
• Metals (primarily near cooling towers); and
• Water treatment chemicals (primarily from chemical storage and mixing and evaporation ponds).

Owing to the type and history of station operation, surface and/or subsurface contamination occurs at the MGS. Potential surface and/or subsurface contamination presents a possible exposure risk depending on the extent of the contamination, the nature of the contaminant, and the location of the contaminant zone. The draft Phase I and Phase II Environmental Site Assessments prepared for the facility (HSI-Geotrans 1998) identifies storage tanks, evaporation ponds, transformer yards, chemical storage and mixing areas, and power block areas as likely sources of releases. These environmental source areas are described below.

Storage Tanks. Aboveground Storage Tanks (ASTs) may have corrosion-induced leaks, flange and fitting leaks, spills due to overfilling during coal slurry and oil transfers, leaks and drips from pressure relief valves, and spills of residual oil inventory from pipe sections during maintenance and construction activities. Underground Storage Tanks (USTs) may have corrosion-induced leaks and leaks due to improper installation, such as loose fittings or piping connections. These leaks and spills typically result in the release of hydrocarbon fuel to secondary containment structures. When secondary containment consists of earthen berms, soil and groundwater contamination may result.

Phase II sampling results near two USTs revealed one sample containing 250 milligrams per kilogram (mg/kg) of TPH, which is above the Nevada Division of Environmental Protection (NDEP) Action Level.

Evaporation Ponds, Canals, and Separators. Evaporation ponds, canals, and separators are used at generating stations to collect, accumulate, and hold the wastewater generated during boiler cleaning operations and other wastewater. The wastewater may contain hazardous chemicals, including acids or caustic materials, resulting in a low or high pH. The wastewater may contain dissolved and suspended metals and high total dissolved solids (TDSs). The wastewater and the residual solids derived from the wastewater may be classified as hazardous wastes under state or federal laws. Releases from the evaporation ponds and canals may occur due to uneven settling below the ponds or other factors that lead to cracks in the liner material. Leaks may result in contamination of soil and groundwater.

The groundwater underneath the MGS is contaminated as a result of the Clark County Sewage Plant and the evaporation ponds at the MGS. Groundwater remediation is currently being conducted under an NDEP permit. Results of the remediation indicate that interim goals for 1996 have been met. The ponds are now lined and a leak detection system has been installed underneath them.

Transformers. Transformers may leak due to corrosion, physical impact from a forklift or other heavy equipment, or spills/leaks during an inspection and oil sampling. Transformers that previously contained PCBs may have leaked PCB oil in the past. After removal of the PCB oil, replacement oil may continue to carry residual concentrations of PCBs. Transformer oil leaks may result in soil and groundwater contamination in the vicinity of the transformers.

Phase II sampling results from shallow samples adjacent to two transformers exceeded NDEP action levels for petroleum hydrocarbons. However, samples collected at deeper depths at the same location were below action levels.

Chemical Storage and Mixing Areas. Typically, chemicals received in 55-gallon drums and smaller containers are stored in one or more dedicated storage areas and used in a nearby mixing room area. Some chemicals (e.g., aqueous ammonia, acids, and bases) may be received in bulk from tank trucks and stored in tanks. Many different chemicals are used for water treatment (cooling water system, boiler feed water system, and boiler cleaning wastewater system). These storage and mixing areas are provided with paved secondary containment to capture leaks or spills. Large spills that breach the containment berm or accumulated material that may seep through the secondary containment may result in soil or groundwater contamination.

Power Block Area. The Power Block Area includes rotating equipment with lubricating oil reservoirs, lubricating oil conditioning units, and other oil-containing equipment. The floor is typically oil-stained due to small leaks and spills. Long-term presence of oil on the floor may lead to seepage and contamination of underlying soil.

Phase II sampling results in the Power Block Area indicate de minimis conditions with the exception of total petroleum hydrocarbons (TPH) and arsenic. One TPH sample collected at 5 feet bgs was above the NDEP action level. However, a sample collected from 15 feet bgs, at the same location, was below the action level.

Arsenic concentrations in six of eight samples exceeded USEPA Preliminary Remediation Goals (PRGs). However, the levels are within ranges for naturally occurring arsenic in western soils.

Regulatory Framework

The current regulatory framework that applies to the MGS encompasses process risks related to use of hazardous materials and management of risks from hazardous wastes that have been released to the environment.

Comprehensive and Environmental Response, Compensation and Liability Act (CERCLA) 1980/Superfund Amendments and Reauthorization Act of 1986. Commonly known as Superfund, this federal law defines reportable quantities for soiled materials and the process for investigation and cleanup of contaminated sites. CERCLA requires that a prospective buyer apply due diligence in obtaining information regarding environmental liabilities associated with the property in order to be relieved of liabilities under the "innocent landowner defense." Financial institutions providing loans for property acquisitions typically require a due diligence investigation as a condition of loan approval. The law also sets up public reporting of the use of certain chemicals under SARA Title III (i.e., the Emergency Planning and Community Right-to-Know Act).

Clean Water Act. The CWA sets up the framework through which permits to discharge wastes to surface water are authorized. The National Pollutant Discharge Elimination System (NPDES) permit typically has conditions specific to the permitted operation and may set limits on pH, chemical concentrations, oil and grease, dissolved and suspended solids, and temperature. The CWA also prohibits the discharge of pollutants to stormwater.

Oil Pollution Act of 1990 (OPA). OPA regulations supplement existing laws regulating the storage and handling of oil. Spill Prevention, Control and Countermeasure (SPCC) Plans are required for facilities storing bulk oil in quantities that can harm navigable waters. OPA added requirements for facilities presenting a threat to navigable water, including a Facility Response Plan (FRP) that prepares the facility for responding to potential worst-case spills. OPA includes employee training requirements related to prevention of releases and responses to releases.

Occupational Safety and Health Administration. The federal OSHA regulations (CFR Title 29) contain employee safety provisions that attempt to minimize the hazards for employees in the workplace.

Asbestos Hazard Emergency Response Act (AHERA) and Clean Air Act (CAA). AHERA provides a classification systems for asbestos-containing materials and specifies the type and quantity and required training for workers involved with asbestos projects. The CAA establishes requirements for removal of asbestos-containing materials.

Toxic Substances Control Act (TSCA). The TSCA includes requirements for the storage, use, and disposal of PCB-containing materials.

Electric and Magnetic Fields. At present, no federal or state regulations relevant to this project pertain to public or work exposures to EMFs.

ENVIRONMENTAL IMPACTS

Sale of the MGS
a), b), c), d), e), f), g), h) The sale of the MGS itself would result in a change of ownership and would not result in any physical changes. The future owner would most likely operate the plant in a similar manner using comparable amounts of hazardous materials and generating similar amounts of hazardous waste.

Current use of hazardous materials and management of hazardous wastes are within existing legal requirements and permit conditions. Future station operators would similarly be in a position to comply with all legal mandates. This analysis is based upon the following assumptions:
• The operator, whether SCE or another party, will be subject to and comply with state and federal regulations and with site-specific permit conditions.
• No physical demolition, removal, and/or remodeling work potentially affecting hazardous materials existing as part of structures, insulation or otherwise inherent in the physical plant (e.g., ACM and PCBs) is proposed as part of the sale.
• After the AB 1890 mandated two-year period in which SCE continues operation of the MGS, the new operator will be trained to the levels specified by applicable local, state and federal regulations.

Construction of 500 feet of Fence
a), b), c), d), e), f), g), h) The construction of the fence would not include the use of hazardous materials. Therefore, no impacts would occur due to hazardous materials.

Continued Existing Operations
a), b), c), d), e), f), g), h) Continued existing operations would not impact the current amount of hazardous materials used or the amount of hazardous wastes generated. Therefore, no impacts would occur due to hazardous materials.

Increased Plant Output by Approximately 10%
a) Increasing the facility’s output may involve the acquisition of new equipment or increased operational time of the existing equipment. If new equipment is installed, it is likely to use less hazardous materials and have reduced occurrence of spills or leaks because of new technologies, such as the use of less hazardous materials and the reuse of hazardous materials in recirculating systems. If the older equipment is operated for longer time periods, the possibility of spills and leaks would increase. It is assumed that the design, operational, maintenance, regulatory, and administrative controls described above would continue to be implemented and would address leaking equipment. Increasing output by 10% would also increase the quantity of ash produced at the facility. The increase would not be substantial and the ash would be handled in the same manner as the ash currently generated at the facility.

b) The facility currently has sufficient procedures to prevent hazards to the public or environment from accidents involving hazardous materials. The HMIS focuses on hazardous materials and hazardous wastes and their management, documents the reportable quantities in the event of a spill, presents a hazard evaluation of chemical storage and mixing areas, and provides chemical and waste inventories and storage locations. Specific response actions are prescribed for releases of several hazardous materials. Station Order O-6 focuses on oil products and hazardous substances and their management. The order includes the facility spill response procedures, a listing of chemical storage tank capacities, reportable quantities in the event of a spill, and an inspection form for RCRA and 1990 Federal CWA compliance.

c) No schools are located within a quarter mile of the operating facility. In addition, the operating facility is surrounded with a buffer zone of undeveloped land.

d) Increasing the output of the MGS would not involve building on sites that have been designated under Government Code Section 65962.5 as a hazardous waste facility, land designated as hazardous waste property, or a hazardous waste disposal site.

e) The facility is not located within the vicinity of an airport and would not interfere with airplane traffic. In addition, the operating facility is surrounded with a buffer zone of undeveloped land.

f) The facility is not located within the vicinity of a private airstrip and would not interfere with airplane traffic. In addition, the operating facility is surrounded with a buffer zone of undeveloped land.

g) The Accident and Fire Prevention Manual implements OSHA’s injury and illness prevention requirements and includes a review of potential hazards that employees may encounter at the facility. The manual identifies preventative measures for injury or illness related to hazards, such as chemicals, elevated temperature, noise, and physical hazards. Under existing OSHA requirements the Accident and Fire Prevention Manual would be updated if substantial changes were made in the operations or equipment. No emergency response or evacuation plans would be impaired.

h) The risk of the MGS starting a wildland fire from increased production is reduced through operational, maintenance, and administrative controls. Operational controls include automatic devices to control and monitor equipment and documented procedures for manual operations. Routine preventative maintenance and inspections of critical equipment help to prevent unscheduled process shutdowns and potential equipment failures. Administrative controls include operator training, documentation of equipment inspection and maintenance history, and procurement of prequalification controls over contractor and vendors.

MITIGATION MEASURES
None required.

Hydrology and Water Quality

Would the project have:	Potentially Significant Impact	Less-Than-Significant With Mitigation Incorporated	Less-Than-Significant Impact	No Impact
a) Violate any water quality standards or waste discharge requirements?	.	.	x	.
b) Substantially deplete groundwater supplies or interfere substantially with groundwater recharge such that there would be a net deficit in aquifer volume or a lowering of the local groundwater table level (e.g., the production rate of pre-existing nearby wells would drop to a level which would not support existing land uses or planned uses for which permits have been granted)?	.	.	.	x
c) Substantially alter the existing drainage pattern of the site or area, including through the alteration of the course of a stream or river, in a manner which would result in substantial erosion or siltation on- or off-site?	.	.	.	x
d) Substantially alter the existing drainage pattern of the site or area, including through the alteration of the course of a stream or river, or substantially increase the rate or amount of surface runoff in a manner which would result in flooding on- or off-site?	.	.	.	x
e) Create or contribute runoff water which would exceed the capacity of existing or planned stormwater drainage systems or provide substantial additional sources of polluted runoff?	.	.	x	.
f) Otherwise substantially degrade water quality?	.	.	.	x
g) Place housing within a 100-year flood hazard area as mapped on a Federal Flood Hazard Boundary or Flood Insurance Rate Map or other flood hazard delineation map?	.	.	.	x
h) Place within a 100-year flood hazard area structures which would impede or redirect flood flows?	.	.	x	.
i) Expose people or structures to a significant risk of loss, injury or death involving flooding, including flooding as a result of the failure of a levee or dam?	.	.	.	x
j) Inundation by seiche, tsunami, or mudflow?	.	.	.	x

ENVIRONMENTAL SETTING

Water Supply
The total influent water capacity is approximately 18,660 gallons per minute (gpm). The water is supplied from three sources: (1) the Colorado River supplies 15,000 gpm; (2) the reclaimed and treated water from the coal slurry pipeline supplies 2,860 gpm; and (3) the reclaimed water from the monitoring wells supplies 800 gpm. One other small contributor to the station water supply is the station water reclaim system.

The river water system begins in a pump house located on the Colorado River due east of the MGS and just north of Harrah’s Casino. The pump house contains three pumps that can each deliver 8,400 gpm. During normal operation, two pumps are in service with the third being in standby. The make-up water rate is dependent on seasonal temperature fluc-tua-tions with summer rates of up to 17,000 gpm and winter rates as low as 5,000 gpm. The water is transported via a 30-inch pipeline to the influent tank to the softener of the primary water treatment system. When the softener is removed from service for maintenance or other operational requirements, the water is pumped directly to the 500,000 gallon water service tank without treatment. Recently, the station has consumed a yearly average of 15,000 acre feet with a station capacity factor of 73%. A level switch on the service water tank will start or stop the pumps automatically.

The coal slurry pipeline, which contains 50 percent water, is routed to a centrifuge prior to being used as fuel. The centrifuge removes most of the water from the coal slurry. The water is then pumped to the clarifloculator, which further treats the water and removes more of the coal. The treated water effluent is called the clarifloculator overflow. The overflow is pumped to the lime/soda ash softener where it is treated.

There are 20 groundwater recovery wells located on the MGS property that operate continuously to remove groundwater with elevated levels of TDS and selenium. In May of 1997, SCE noted that some of the wells may be shut down if the TDS and selenium levels decrease to acceptable levels. The water recovered by these wells is pumped to the Service Water System, where it is co-mingled with the river water and the clarifloculator overflow.

The station reclaim water system consists of water reclaimed from evaporation Pond #2 and from area drains located throughout the MGS.

The three reclaim water streams, the coal slurry water, monitoring well water, and reclaim system water are mixed in the softener influent tank. The water from the softener influent tank is pumped to the Service Water System where it is mixed with the River Water System (SCE 1999).

Water Uses and Systems
Current water uses include:
• Potable water for station personnel uses and landscaping
• The service water system, which is used for cooling water and boiler feed water

The cooling water system consists of seven cooling towers that cool 540,000 gpm of circulating water. Water leaving the towers flows into a canal, which extends 2,556 feet. Water from the canal is pumped into the condensers to cool and condense the spent steam. From the condensers, water is carried to the top of the cooling towers and cascades down the tower structure, releasing heat picked up in the condensers.

The boiler feedwater system consists of two distinct streams: (1) condensate return from condensed steam and (2) treated make-up water. The feedwater system is divided into two parts: the deaerator to the boiler feed pumps and downstream of the boiler feed pumps to the economizer input. Feedwater from the deaerator storage tank is pumped through a series of heaters by the boiler feed pumps.

The Colorado River is the sole source of the potable water system. The river water is softened and filtered through Zeolite® filters, potable water sand filters, one micron disposable cartridge filters, and one micron cuno cartridge filters. Following filtering and chemical treatment, the water is stored in the potable water tank. The water must be chlorinated to control biological growth. Chlorination is accomplished by injecting a hypochlorite solution into the potable water storage tank. The potable water is used for personnel and landscaping purposes (SCE 1999).

Water Treatment System
The water treatment system consists of a lime system, soda ash system, softener equipment, and the Zeolite® resin exchange system. The softener influent tank, with a capacity of 16,700 gallons, receives water from the clarifloculator overflow, the station monitoring wells, station water reclaim system, and the river water system. The role of the softener influent tank is to provide make-up water to the primary softener. Water leaves the influent tank and flows directly into the primary softener centerwell.

The softener tank, with a capacity of 2.5 million gallons, is designed for a continuous flow of 16,000 gpm, with a short-term maximum capability of 20,000 gpm. The primary softener provides soft water make-up for the service water system. The softener uses unslaked lime, calcium oxide to produce the elevated pH needed for softener operation. Soda ash is added to remove calcium from the water. Calcium, magnesium, silica, and suspended solids are removed from the treated water through precipitation and adsorption. The precipitate sludge is removed to the station’s wastewater ponds. The softener effluent water is pH adjusted and pumped to the service water tank with a capacity of 500,000 gallons. From the service water tank, the water is pumped throughout the plant for any use except potable water (SCE 1999).

Current Wastewater System
The MGS is designed as a "zero discharge facility" with excess water being removed through evaporation. The evaporation system includes the cooling towers and lined evaporation ponds. Water unusable due to high salt content, solids, or health risks is pumped to one of the station evaporation ponds. The largest wastewater stream is the brine concentrator (BC), which concentrates salts from the open circulating water system and sends the concentrated salt solution to the wastewater ponds. Two other large contributors to the wastewater stream are the lime/soda ash softener sludge and the station sewage treatment system effluent.

The wastewater effluent streams include the following:
• Potable water system - 60 gpm
• Brine concentrator - 50 gpm
• Stack evaporation - 1,341 gpm
• Cooling tower evaporation - 17,209 gpm

To ensure the MGS is meeting its zero discharge permit requirements, an extensive array of monitoring wells and underground resistivity cables have been installed throughout the station. There are four systems for gathering and delivering wastewater in the plant. Two of the systems, the primary sump and oily water sump, are in constant use. The other two systems, the 6601 line and the clarifloculator underflow to waste, are used infrequently and only for a specific operation.

The primary sump is the gathering point for the cooling water supply canal blowdown, BC blowdown, and softener sludge blowdown. All of these wastes are high in TDS and non-reclaimable. These non-reclaimable wastes are sent to either the primary or secondary evaporation ponds.

The canal blowdown is the largest wastewater stream to the primary sump. The blowdown is drawn form the canal outfall tunnels and is used to ensure the water in the canal system remains soft.

The BC is a thin-film evaporator/condenser and is used to help minimize non-reclaimable wastes. The BC takes water from the canals and increases the solid content of the wastewater through evaporation. The concentrated wastewater solution is pumped to the ponds. A by-product of the BC is a high purity water, which is used as a feedstock for the boiler feedwater make-up system. The BC has reduced the amount of wastewater generated by a factor of 10.

The oily water sump collects the water from all the station drains, equipment pit sumps, auxiliary boiler blowdown tank, acid sump, and the peripheral ponds. The sump is a two compartment concrete tank with a connecting siphon. The water is allowed to settle in the first compartment and is then siphoned off to the second compartment. The oil is retained in the first compartment and is removed by vacuum truck as needed. All wastewater gathered in the oily water sump is reclaimable. Once the oil has been separated out, the water is pumped to the reclaim ponds. The water from the reclaim ponds is pumped back to the softener influent tank.

The clarifloculator underflow is normally sent to the boiler for burning. However, when this is not possible due to operating constraints, the underflow is sent to the evaporation ponds. The 6601 line delivers pipeline water used to flush the Black Mesa Pipeline (SCE 1999).

Groundwater
Groundwater occurs at depths of 150 to 200 feet below ground surface at the project site, roughly corresponding to the elevation of the Colorado River. Regional groundwater flows to the east, but groundwater gradient at the station is to the southeast and quite flat.

An ephemeral stream channel that flows south towards the Colorado River is located on-site. The channel would carry runoff from the station, but is intercepted by the Ash Dam that is designed to capture site runoff from the fly ash disposal area. The MGS is located approximately 3,000 feet northwest of the Colorado River.

The Ash Dam is permitted in the discharge permit issued by the NDEP’s Bureau of Water Pollution Control. It is assumed that adjudicated water rights or stipulated water agreements can be transferred. The MGS plans to shut down some of the monitoring wells as the groundwater quality returns to acceptable levels. If the current owners (or the new owner) initiates the action to shut down the wells, this will further reduce the amount of water available for the station (SCE 1999).

Flooding
The MGS facility is not within the 100-year storm flood area mapped by the Federal Emergency Management Agency. The MGS itself is not within the flood inundation area.

According to Bob Walsh of the US Bureau of Reclamation, the MGS will not flood in the event of a dam failure. Failure of Hoover and Davis Dam would not result in inundation of the MGS itself but could result in inundation of the water intake for the MGS that is located at the edge of the Colorado River.

ENVIRONMENTAL IMPACTS

Sale of the MGS
a), b), c), d), e), f), g), h), i), j) Sale of the MGS would not itself result in any physical changes to the environment because the sale would result only in a change in the ownership of the MGS. Therefore, no impacts to hydrology or water quality would occur.

Construction of 500 feet of Fence
a) Construction of 500 feet of fencing on a site that is already used for a power plant may result in exposure of small amounts of soils that may be excavated to erosion. This impact would be less-than-significant because only a small amount of soils would be exposed on relatively level ground that is subject to infrequent rainfall.

b) Construction of 500 feet of fencing would have no effect on groundwater. Therefore, fence construction would not deplete groundwater or affect groundwater recharge.

c) Construction of 500 feet of fencing would not alter drainage patterns because the fence would allow occasional low volume surface flows to pass under it. Constructing the fence would thus not result in substantial erosion or siltation on- or off-site.

d) Construction of 500 feet of fencing would not alter drainage patterns or change the amount of runoff from the site. The fence occupies very little area and so does not increase the amount of impervious surface that would generate additional runoff. Constructing the fence would thus not result in flooding on- or off-site.

e) Construction of 500 feet of fencing could result in a minor increase in soil erosion that may become suspended in storm water or runoff. In total, the amount of soil displaced is expected to be less than a cubic yard. In addition the construction site is flat and the climate hot, allowing for maximum evaporation. Construction would not cause a substantial increase in soil runoff. Existing drainage systems would adequately accommodate runoff.

f) Construction of 500 feet of fencing would not otherwise substantially degrade water quality. The fence would not change the amount of runoff from the site (see d above) or change the direction of any existing flows because the fence would allow low volume surface flows to pass under it. The fence would only increase impervious surface by a small amount, which would not result in a noticeable increase in runoff.

g) Construction of 500 feet of fencing would not result in the location of housing in a 100 year flood area because no housing would be constructed.

h) The MGS facility, including the fence site, is not within the 100-year storm flood area mapped by the Federal Emergency Management Agency. The fence would thus not impede or redirect flood flows within a 100-year flood hazard area.

i) Construction of 500 feet of fencing would not result in subjecting any people or structures to flooding, including flooding from failure of a levee or dam. Failure of Hoover and Davis Dam would not result in inundation of the MGS.

j) Construction of 500 feet of fencing would not be subject to tsunami because the fence is located a sufficient distance from the ocean to be outside the area subject to tsunami. The site is located on relatively flat terrain that is unlikely to be subject to mudflow. A seiche could occur in the storage ponds located on the site. The liquids in the storage ponds could possibly reach the fence area but are a sufficient distance from the fence to ensure that the low volumes that reach the fence do not substantially damage the fence. Therefore, sale of the MGS will not result in any new property being subject to inundation by seiche, tsunami, or mudflow.

Continued Existing Operations
a), b), c), d), e), f), g), h), i), j) Continuation of existing operations would not itself result in any physical changes to the environment because there would be no change in operations of the MGS. Therefore, no impacts to hydrology or water quality would occur.

Increased Plant Output by Approximately 10%
a) Increased plant operations is not expected to result in any difference in water quality and will therefore not violate any water quality standards. The MGS does not discharge any wastewater from the MGS. Wastewater is evaporated in evaporation ponds. When the solids in the evaporation ponds reach a certain depth, their chemical composition is evaluated to ensure they do not contain any hazardous materials and they are then transported to an on-site landfill. The slight increase in water use to accommodate increased generation would result in slightly more solids being transported to the on-site landfill.

b) The MGS obtains most of its water from the Colorado River and from water used to transport the coal. Some groundwater is used at the MGS as a part of a hazardous materials clean-up project. Increased operations at the MGS is not expected to increase use of groundwater. Increased use of groundwater would, up to a point, accelerate the clean-up of the contaminated water beneath the site and would therefore be beneficial. The MGS is restricted in the total amount of water it uses from the Colorado River and groundwater. Increased generation would occur within the constraints of the existing water supply. Therefore, the increase in operations is not expected to deplete groundwater resources. Increasing plant output would not require additional structures that would substantially affect groundwater recharge.

c) An increase in output at the MGS would not result in any changes in drainage patterns because no physical improvements likely to alter drainage patterns would occur. The output increase would thus not cause erosion or siltation.

d) An increase in output at the MGS would not result in any changes in drainage patterns because no physical improvements likely to alter drainage patterns would occur. The output increase would thus not cause flooding.

e) An increase in output at the MGS would not result in any changes in run-off quality because no physical improvements are proposed that will alter run-off quality or amounts.

f) An increase in output at the MGS would not result in any decrease in water quality because none of the process water at the MGS is discharged to drainage courses. Process water is left in ponds where evaporation reduces the liquid fraction and leaves material that is tested to ensure no hazardous materials are included and then removed and transported to an on-site landfill.

g) No housing would be constructed.

h) An increase in output at the MGS would not result in any changes in the exposure to flood risks because no physical improvements would be constructed that would be subject to flooding and the MGS is not located within a Federal Emergency Management Agency 100 year flood zone. No new structures would be constructed within a 100 year flood zone.

i) An increase in output at the MGS will not result in any new construction. No new facilities would be subject to flooding resulting from failure of a levee or dam.

j) An increase in output at the MGS will not result in any changes in the exposure to seiche because no physical improvements would be constructed that would be subject to seiche. Tsunami and mudflow hazards do not occur on the project site because of the distance from the ocean to the site and the absence of nearby elevated areas to be a source of mudflows.

MITIGATION MEASURES
None required.

Land Use and Planning

Would the project have:	Potentially Significant Impact	Less-Than-Significant With Mitigation Incorporated	Less-Than-Significant Impact	No Impact
a) Physically divide an established community?	.	.	.	x
b) Conflict with any applicable land use plan, policy, or regulation of an agency with jurisdiction over the project (including, but not limited to the general plan, specific plan, local coastal program, or zoning ordinance) adopted for the purpose of avoiding or mitigating an environmental effect?	.	.	.	x
c) Conflict with any applicable habitat conservation plan or natural community conservation plan?	.	.	.	x

ENVIRONMENTAL SETTING

Regional Land Use Characteristics
The MGS is located in the Mohave Desert in the southern portion of the State of Nevada within the unincorporated community of Laughlin, approximately 90 miles south of Las Vegas. The site is in the Mohave Valley, a desert valley between parallel north-south mountain ranges, generally with elevations of 2,000 to 3,000 feet above the valley floor. The community of Laughlin is set in rugged mountain terrain that gently slopes to the banks of the Colorado River.

To the east of the station is the Colorado River and the community of Laughlin, which primarily consists of hotels/casinos. Approximately one mile east of the MGS, across the river, is Bullhead City, Arizona. To the west are residential properties, and to the southwest are commercial properties. To the north of the MGS is the Clark County Sewage Treatment Plant, Laughlin High School, and open land owned by BLM. Approximately 10 miles north of the MGS is Lake Mead National Recreation Area, with Lake Mohave and Davis Dam located along the Colorado River. Directly south of the station is the highway into Laughlin, a golf course, the Colorado River, and some residential property.

Site-Specific Land Use Characteristics
The MGS lies on a site of approximately 2,490 acres; Units 1 and 2 are approximately one mile west of the Colorado River. The units are built on a plateau with arroyos falling away to the river on the east and south sides and with a sloped plain rising to mountains to the northwest. The majority of the property is undeveloped desert terrain. In addition to the generating station and its facilities, the site hosts several other facilities:
• Mountain View Park (about 17.49 acres)
• Nevada Power Service Center (10 acres)
• Flyash Haulers (5 acres)
• Western Ash (4 acres)
• Nevada Power Switchyard (2 acres)
• The MGS Visitor Center (1 acre)

The Mountain View Park is located in the northwest portion of the property and has picnic areas, playground, tennis court, ball fields, a Senior Center, a Police Sub-Station, and Boys and Girls facilities. The property is under a licensed agreement between SCE and the community of Laughlin (further discussion on recreational resources is provided in Section 4.14).

Existing Land Use Patterns
Since construction of the MGS was completed in 1971, Laughlin, Bullhead City, and the surrounding community area have developed into an urban area with nearly 65,000 full-time residents. Growth in the area has been fueled by the development of the casino industry, the recreational opportunities provided by both the Colorado River and lakes formed on the river by dams, and the desert climate. The "casino row" in Laughlin now extends one to two miles from the station, and most of the Laughlin/Bullhead City area population lives within four or five miles of the plant.

General Plan and Zoning Ordinance
The main tools used in land use regulation are planning documents, ordinances, and permitting procedures, as employed by local agencies. The general plan assembles the local jurisdiction’s basic land use doctrine and regulates future land use decisions. Zoning ordinances govern the type and intensity of land uses and set standards for development within a city or county. The following paragraphs outline the general plan and zoning ordinance that govern the facility property and surrounding lands.

Laughlin is an unincorporated area of Clark County, represented by a Town Advisory Board and governed by a County Commission. The site and surrounding area fall under the jurisdiction of the Laughlin Land Use and Development Guide (Clark County Department of Comprehensive Planning 1993). The Guide is a land use development plan that consists of a set of land use maps and policies that define a land use development pattern suitable for the Laughlin area. The following policy has been established specifically for the MGS:

In order to maintain land use compatibility, limit industrial development in Laughlin North to the current boundaries of the Mohave Generating Station. Encourage on-site buffering of the heavy industrial area with uses in the MD (Designed Manufacturing), PF (Public Facility), and CG (Commercial General) categories.

The majority of the MGS is designated IND-Industrial in the Laughlin Land Use and Development Plan. IND-Industrial designation includes areas where the primary land uses are medium to heavy industrial, including most utilities.

Typical uses include manufacturing and assembly plants requiring outdoor storage, wholesale sales and storage, utility stations or plants, laboratories, and industries that produce or use hazardous materials. The northwest portion of the site surrounding Mountain View Park is designated open land, and the park itself is designated public recreation. The southwest portion of the site is also designated open land.

The land immediately to the west of the MGS is designated low, medium, and high density residential with pockets of commercial areas. To the south, the golf course is designated public recreation and other lands are designated commercial tourist. The majority of the land to the east is designated commercial tourist, and to the north the water treatment plant is designated industrial, the high school is designated public facility, and the remainder of the land is federally owned by the BLM.

The entire site is zoned M-3 (Heavy Industrial District) with the exception of the Mountain View Park land, which is zoned P-F (Public Facility District).

ENVIRONMENTAL IMPACTS

Sale of the MGS
a), b), c) Sale of the MGS would not have any physical impacts on the environment because it would only change the owner of the MGS; therefore, the sale of the MGS would not result in division of an established community, conflict with any applicable plan, policy or regulation of an agency with jurisdiction over the project, or conflict with any applicable habitat conservation plan or natural community conservation plan.

Construction of 500 feet of Fence
a) The 500 feet of fencing would be constructed within the existing MGS facility. There is no community in the vicinity of the fence; the fence construction would not divide any community.

b) The 500 feet of fencing would be constructed within the confines of an existing industrial facility. The construction of 500 feet of fencing does not conflict with any plan, policy, or regulation of an agency with jurisdiction over the project.

c) The construction of 500 feet of fencing in the midst of an existing industrial facility would not conflict with any applicable habitat conservation plan or natural community conservation plan.

Continued Existing Operations
a), b), c) Continued operation of the MGS would not have any new physical impacts on the environment. Therefore, the continuation of operations would not physically divide an existing community, conflict with any applicable plan, policy or regulation of an agency with jurisdiction over the project, or conflict with any applicable habitat conservation plan or natural community conservation plan.

Increased Plant Output by Approximately 10%
a) Increase in generation at the MGS would result in an incremental increase in the rate of use of coal and more intense use of the MGS. The increased use of coal would not result in a physical division of a community because it occurs at an existing mine where no community is located. The increased generation would occur on a site that does not include any community. Therefore, the increased generation would not result in the division of any community.

b) Increase in generation at the MGS would result in an incremental increase in the rate of use of coal and more intense use of the MGS. The increase in generation would not conflict with any plan, policy, or regulation of an agency with jurisdiction over the project as long as the generation stays within existing permit requirements. This projected increase in output would be expected to be conducted within permit requirements.

c) Increase in generation at the MGS would result in an incremental increase in the rate of use of coal and more intense use of the MGS. The MGS is an existing facility that would operate more intensely. The coal mine is operating and would increase the rate of mining slightly. The increased coal mining and increased generation would not conflict with any habitat conservation plan or natural community plan.

MITIGATION MEASURES
None required.

Mineral Resources

Would the project have:	Potentially Significant Impact	Less-Than-Significant With Mitigation Incorporated	Less-Than-Significant Impact	No Impact
a) Result in the loss of availability of a known mineral resource that would be of value to the region and the residents of the state?	.	.	.	x
b) Result in the loss of availability of a locally-important mineral resource recovery site delineated on a local general plan, specific plan, or other land use plan?	.	.	.	x

ENVIRONMENTAL SETTING
The BLM manages mineral resources on their public lands in the region. For their lands in southern Clark County, there are no occurrences of coal, phosphate, or oil shale. There are no active oil, gas, or geothermal leases in the area, and there are no active mines (BLM 1998).

There are no lands designated for Mineral Extraction by the Laughlin Land Use and Development Plan (SCE 1999). No mineral resources are extracted on the project site.

ENVIRONMENTAL IMPACTS

Sale of the MGS
a), b) The sale of the MGS would not in and of itself, result in physical changes and would thus not result in impacts to mineral resources.

Construction of 500 feet of Fencing
a), b) Currently, there are no mineral resources on the site and no plans to change the existing land use. Structural additions, such as the addition of 500 feet of fencing, would therefore not affect mineral resources.

Continued Existing Operations
a), b) Continuation of existing operations would not result in the loss of availability of a known mineral resource that would be of future value to the region or residents of the State of Nevada, nor would the proposed project result in the loss of availability of a locally-important mineral resource recovery site delineated by the Laughlin Land Use and Development Plan (SCE 1999).

Increased Plant Output by Approximately 10%
a), b) There are no mineral resources within the site boundary or in the project vicinity. No change in land use would be associated with increased plant output. Consequently, no on-site impacts to mineral resources would occur.

Increased output will result in an increase in the rate of use of coal from the mine. This would accelerate the use of the resource. Since this resource has already been dedicated as a fuel source, and the increase in rate of use is minor, this impact is identified as less-than-significant.

MITIGATION MEASURES
None required.