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4. ENVIRONMENTAL CONSEQUENCES AND MITIGATION MEASURES

4.1. Proposed Action

4.1.1. Geology and Mineral Resources

4.1.1.1. Assumptions and Assessment Guidelines

Expose people or structures to major geologic hazards; or
Substantially restrict the future ability to utilize mineral resources.

4.1.1.2. Impacts of the Proposed Action

Slope Stability and Seismic Effects:

Seismic review of regional faults (active and potentially active) has indicated maximum credible earthquake magnitudes of 5.8 to 7.5 (see Table 4.1). However, because of the distance from each of these faults to the Project mine and process area; the nature of the underlying geologic units; and the depth to ground water; regional seismicity is not expected to cause substantial horizontal accelerations or extensive ground shaking within the Project area.

The proposed slope configurations for the leach pad ore heap (2H:1V, including benches) are similar to those used at nearby mining operations, at which no substantial slumping or slope failure has occurred. Stability analyses completed for the planned heaps and waste rock stockpiles (WESTEC, Inc. 1996b) also indicate that the proposed slope of the heap and waste rock stockpiles would be stable and unlikely to produce substantial failures, including landslides, either under normal operating conditions or from ground shaking during regional seismic events.

Preliminary pit slope recommendations prepared for the East Pit and West Pit contained slope angles ranging from 40E to 55E, with circular failure and/or non-daylighting wedge failure potential within the pits controlling most of the slope angles (WESTEC, Inc. 1997). Experience at nearby mines indicates that the proposed final pit wall slope of 1H:1.2V (50 degrees), constructed in cemented alluvium/gravels and metamorphic rock, would provide the required factor of safety for long-term slope stability, including the vibrations from blasting and ground shaking from anticipated seismic events in the region. The proposed pit wall design includes safety benches at regular vertical intervals to contain minor rock falls. The waste rock stockpile slope configurations would also be similar to those used at the Picacho Mine. No substantial slumping or slope failure is anticipated; however, the preliminary pit slope report recommended re-evaluation once mining operations commenced and more data was available.

Table 4.1

Fault or Fault Zone
Distance and Direction
from Project Area
(miles/direction)
Maximum Probable Magnitude
Effects at Project Area

Maximum Probable Peak Acceleration (g)^a Duration of Strong Ground Shaking (seconds)

East Mesa 29/West 6.0 0.17 18

East Highline Canal Lineament 32/West 6.0 0.09 18

Imperial/Brawley 42/Southwest 6.8 0.07 24

Brawley Seismic Zone 44/West 5.8 0.04 18

Superstition Hills 55/West 7.0 0.05 30

San Andreas 63/Northwest 7.5 0.04 36

Elsinore 77/Southwest 7.0 0.03 30

^aSource: Joyner and Fumal 1986 (In: Environmental Solutions, Inc. 1993b.)

Because of the great depth to ground water, and the design of the heap leach pad, which prevents the accumulation of standing water within the heap, there is very little potential for any liquifaction, and no significant effects are anticipated.

Project structures would be designed and constructed subject to the current Uniform Building Code (UBC) Seismic Zone 4 standards, which are the most stringent in the UBC. Implementation of Seismic Zone 4 standards would conform to the current Building Code Requirements of the Imperial County Planning/Building Department, and prevent catastrophic failure of facilities which could endanger human life during seismic events. Therefore, impacts to Project facilities from remote seismic events would not be significant.

No surface ruptures are anticipated from seismic activity because there are no known or currently identified active faults within the Project area. Mining of the proposed pits would not be expected to affect either the physical geology of known faults in the region or regional seismicity. No significant effects are anticipated.

Subsidence:

No land surface subsidence due to the extraction of ground water from the ground water production wells is expected. Generally, land surface subsidence related to ground water extraction occurs only when the drawdown of the ground water table is large or results in a substantial pressure reduction in a confined aquifer; or a substantial percentage of the earth materials forming the aquifer are fine-grained (silts or clays); or the depth from the surface of the land to the water table is small. Because the amount of ground water the Project proposes to extract is not large compared to the size of the aquifer or the amount of water in storage (see Section 4.1.3.2.2); because the sediments in the ground water production area are relatively coarse alluvial materials; and because the depth to ground water is greater than 500 feet below ground surface (bgs), measurable subsidence is not expected to occur as a result of the production of ground water. If subsidence were to occur, it would be localized and not adversely affect any Project facilities or natural or other man-made features. The wells, water pipeline, and electrical transmission and distribution lines can each tolerate localized subsidence. There are also no other existing or planned developments or natural features in the immediate vicinity of the ground water production wells which could be adversely affected by localized subsidence. Thus, the impact of any subsidence which may occur would be below the level of significance.

Naturally Occurring Radioactive Materials:

Materials to be mined by the Project have not been analyzed for naturally occurring radioactive materials (NORM). However, some analyses from the general area for radon gas and uranium and thorium in soils have been conducted and can be used as an indication of the relative amount of NORM in the Project mine and process area. In 1990 the California Department of Health Services (CDHS) conducted an initial phase radon survey by placing short-term radon detectors in approximately 2,858 randomly selected homes (CDHS 1990). Two samples were collected from homes in the Brawley area of Imperial Valley, the results of which indicated radon isotope-222 levels of 1.8 and 1.1 picocuries per liter (pCi/l) of air. These values are substantially below the USEPA recommended level of 4.0 pCi/l at which action should be taken to reduce radon levels. The mining of the proposed West Pit, Singer Pit, and East Pit is not expected to substantially increase the release of naturally occurring radon gas into the atmosphere.

Within an approximately fifteen (15)-mile radius of the Project mine and process area, approximately 37 soil samples were collected as part of the national uranium resource evaluation (NURE) (Hoffman, et al. 1991). The uranium values from these soil samples range from 2.2 to 4.4 ppm, and average 3.0 ppm. The average crustal abundance of uranium is 2.5 ppm (Rose, et al. 1979). The thorium values from the same soil samples range from 4.0 to 21.0 ppm, and average 10.67 ppm. The average crustal abundance of thorium is 10 ppm. In the immediate vicinity of the Project area, two (2) soil samples were collected. The uranium values from these two (2) soil samples are 2.2 and 3.0 ppm, which produce an average of 2.6 ppm. The thorium values from the same two (2) soil samples were 5.0 and 16.0 ppm, which produces an average of 10.5 ppm. Using the radon values in comparison to the USEPA recommended action level, and the uranium and thorium values in comparison to the average crustal abundance of those elements, neither the Project area nor the vicinity appears to have elevated levels of radioactive elements and, therefore, elevated NORM levels would not likely be expected to be produced by operations within the Project mine and process area. These impacts would be below the level of significance.

Loss of Mineral Potential:

Condemnation drilling by Glamis Imperial geologists has been used to determine the limits of the gold ore bodies within the Project mine and process area. The results of this drilling, to date, indicate that valuable mineral resources common to the Project mine and process area do not exist in the areas of the proposed heap pad, waste rock stockpiles, and the process and ancillary facilities. Therefore, no potentially valuable mineralization would be buried by the placement of these facilities in these areas.

Backfilling of the West Pit would result in the burial, and thus likely loss, of some mineral resources since there is some mineralization at the bottom of the West Pit which would not be mined under the Proposed Action. However, as shown in Figure 3.2, this mineralization is dipping steeply to the west, and any mining would produce substantially greater quantities of waste rock per ton of ore than is currently economic under the Proposed Action. Thus, mining of this mineralization is very unlikely to ever be economic, and its loss would not be significant.

Some mineralization would also be left in some locations at the bottom of the East Pit following the completion of mining under the Proposed Action. Since the East Pit would only be partially backfilled, if necessary, to the level needed to raise the floor to the predicted level of any pit lake, the costs of mining this mineralization below the current limits of the Proposed Action under some future Plan of Operations would increase only slightly over that of leaving the East Pit completely open. This decrease in the economic value of the mineralization in the East Pit from partially backfilling would not be significant.

4.1.1.3. Measures Incorporated by Project Design and Regulation and Mitigation Measures

4.1.1-1: Heap leach pad and waste rock stockpile slopes shall be constructed at overall slopes no steeper than 2H:1V.
4.1.1-2: Mine pit slopes shall be constructed at overall slopes no steeper than 1H:1.2V (50 degrees) unless mining conditions and geotechnical factors demonstrate through engineering analysis that steeper slopes would be safe, and such steeper slopes shall be approved by the BLM. Slopes shall not be steeper than is safe considering actual rock strength and structural conditions encountered. Pit slope angles in the West Pit and East Pit shall be re-evaluated after one (1) year of mining of that pit.
4.1.1-3: Approximately 40-foot wide benches shall be constructed at approximately 80-foot high intervals on mine pit slopes to catch loose rocks. Approval shall be obtained from the BLM prior to construction of mine pit benches which differ substantially from these specifications.
4.1.1-4: To avoid any substantial slumping or slope failure of the heap and waste rock stockpile slopes, the recommendations of the slope stability analyses of these facilities shall be followed during the construction of these facilities.

Measures Incorporated by Regulation Which Avoid or Reduce Potentially Significant Impacts:

4.1.1-5: Project structures subject to the Uniform Building Code shall be designed and constructed consistent with the standards of Seismic Zone 4.

Mitigation Measures Proposed to Avoid or Reduce Potentially Significant Impacts:

No mitigation measures are proposed or recommended.

4.1.1.4. Unavoidable Adverse Effects and Level of Significance After Mitigation

There would be no unavoidable adverse effects to geology from implementation of the Proposed Action. The goal of the Proposed Action is to mine precious metal mineral resources for beneficial use.

The effects of the Proposed Action on geology or mineral resources would be below levels of significance.

4.1.2. Soil Resources

4.1.2.1. Assumptions and Assessment Guidelines

Cause substantial erosion.

4.1.2.2. Impacts of the Proposed Action

Approximately 1,302 acres would be disturbed within the Project mine and process area, 38 acres within the Project ancillary area, and 22 acres within the overbuilt 92 kV/34.5 kV transmission line corridor as part of the Proposed Action. Soils within the Project mine and process area are poorly-developed gravelly sands, and only a thin covering of soil is present for Project reclamation and revegetation. Approximately 112,200 cubic yards of soil would be salvaged from all washes and areas where sufficient soil development is noted. Soils would be salvaged to the greatest depth practicable (generally 12 to 18 inches) and stockpiled for later use during reclamation activities. Soils would be stockpiled at two (2) proposed sites within the Project mine and process area (see Figure 2.2). The soil stockpiles would be clearly identified with signs to assure that the material was not misidentified as waste rock material. The gravelly nature of the soils would minimize erosion by wind and rain.

Many of the soils in the Project area, and many of the Project facilities themselves (such as the soil stockpiles, waste rock stockpiles, and heap, etc.), may be subject to erosion, either from precipitation falling directly within the Project area or from flow events in the ephemeral washes. To minimize erosion, Glamis Imperial has indicated that all Project facilities (including the heap leach facility, waste rock stockpiles, soil stockpiles, and roads) would be designed and constructed with erosion control features engineered to meet the performance standards at 14 CCR 3706 (see Section 2.1.11.2.3). The Project would also be required to be constructed and operated in accordance with a Storm Water Pollution Prevention Plan (SWPPP), which requires the use of Best Management Practices for erosion control, in accordance with the California Storm Water National Pollution Discharge Elimination System (Storm Water NPDES) permit program (California Water Code Section 13000 et seq.).

Surface runoff and drainage from disturbed areas within the Project mine and process area would be controlled, collected, conveyed to sediment basins, and infiltrated (or consumed in the mining or heap leach process). Any areas which might be susceptible to erosion from surface flows would be protected through the use of berms, sediment ponds, rip rap, check dams composed of sand bags, silt fences, or other techniques to prevent erosion and potential damage. These erosion control features would be in areas currently proposed for disturbance. Erosion control methods would be designed to handle at least a 20-year/1-hour intensity storm event, in accordance with standards established by 14 CCR 3706(d) (SMARA regulations). Modifications to the erosion control methods would be made as necessary over the life of the Project. As a result, substantial erosion would not be created and the impacts of erosion would not be significant.

Several ephemeral drainages would be permanently diverted around the Project facilities within the Project mine and process area. Rip rap would be placed along the channel banks to prevent erosion. Each diversion would channel the flow into the same major wash, or into another existing wash which was tributary to the same major wash, thus putting all flow back into the same drainage system. Diversion channels would also be built to approximate the original drainage system in both gradient and channel geometry, and would be designed to convey all runoff flows from the 100-year 24-hour, 100-year 6-hour, and 500-year 24-hour precipitation events. This would minimize changes in the hydraulic characteristics of the channel and minimize the potential to increase any erosion from the diversion of the wash. Erosion impacts from the diversion of the ephemeral stream channels would not be significant.

Because the washes which flow through the Project mine and process area continue downgradient to the southwest until each eventually ends in individual areas of infiltration on the eastern edge of the Algodones Sand Dunes (see Figure 3.18), there would be no impacts from erosion, sedimentation, or diversion of ephemeral stream channels on any areas outside of the "Indian Wash Drainage Basin," including the Fort Yuma Indian Reservation or the "Picacho Wash Drainage Basin" in which the Fort Yuma Indian Reservation sits.

Because of the minimal amount, depth, and length of time of the surface disturbance associated with activities to be conducted within the Project ancillary area and the overbuilt 92 kV/34.5 kV transmission line corridor, there is little chance of any substantial erosion. This would be a less-than-significant effect.

4.1.2.3. Measures Incorporated by Project Design and Regulation and Mitigation Measures

4.1.2-1: Surface disturbance shall be kept to the minimum that is required to construct and operate the project.
4.1.2-2: Soils shall be salvaged from all areas where sufficient soil development is noted in conformance with the approved Reclamation Plan. Soils shall be salvaged to the greatest depth practicable and placed in stockpiles clearly delineated with signs to assure the material is not mistaken as waste rock. Soil stockpiles shall be located away from washes and other areas prone to erosion and consolidated as appropriate to reduce disturbance to undisturbed areas within the Project mine and process area. Stockpiles shall be kept shallow and dry, if not to be used within one (1) year of initial placement, to protect seeds.
4.1.2-3: All mine facilities shall be designed and constructed with erosion control features engineered to meet the performance standards of 14 CCR 3706, including the control of runoff and protection of areas susceptible to erosion from surface flows.

Measures Incorporated by Regulation Which Avoid or Reduce Potentially Significant Impacts:

4.1.2-4: A Storm Water Pollution Prevention Plan, incorporating the use of Best Management Practices for erosion control, shall be developed and implemented in accordance with the California Storm Water NPDES permit program.

Mitigation Measures Proposed to Avoid or Reduce Potentially Significant Impacts:

No other mitigation measures are proposed or recommended.

4.1.2.4. Unavoidable Adverse Effects and Level of Significance After Mitigation

Implementation of the Proposed Action would result in the unavoidable loss of those minor amounts of soils which cannot be salvaged during construction. Based upon regulatory requirements and mitigation measures that have been incorporated into the Project design, effects of the Proposed Action on soil resources would be below level of significance.

4.1.3. Hydrologic Resources

4.1.3.1. Surface Waters

4.1.3.1.1. Assumptions and Assessment Guidelines

Substantially degrade water quality;
Contaminate a public water supply;
Cause substantial flooding or siltation; or
Substantially alter surface flow conditions, patterns, or rates.

4.1.3.1.2. Impacts of the Proposed Action

In addition to other changes, this section has been modified from the November 1996 Draft EIR in response to comments to: include a discussion of flood zones; and add a new delineation of "waters of the United States" impacted by the Proposed Action.

Stream Flow Alterations:

The Proposed Action would include the diversion of segments of five (5) existing ephemeral watercourses, and the permanent filling or excavation of tributaries of these watercourses. All diversions divert water entering the Project mine and process area to other segments of these same washes, which then flow naturally through or around the Project mine and process area (see Figure 2.9).

Although these diversions result in a substantial alteration to surface water drainage patterns within the Project mine and process area, each diversion would channel the flow directly into another existing wash which was tributary to the same major watercourse. All other storm water surface flows entering the Project mine and process area which would not otherwise impact Project facilities would flow through the Project mine and process area. Each of the diversion channels has been designed to safely convey all runoff flows from the 100-year, 6-hour precipitation event, which satisfies the siting requirements for mining waste management units (23 CCR 2572(b)) and exceeds the recommended design values for diversions and drainage facilities around mining waste management units as prescribed in 23 CCR 2572(h)(1)(C). Because there is some potential for flash flooding from thunder storms, the diversion channels have also been designed with an additional "flood bench" area immediately adjacent to the main channel so that the channel and "flood bench" together can easily accommodate the 500-year, 24-hour storm flow (see Figure 2.10). Each of the diverted channels directs flows around the mining facilities and back into the same major drainage system from which it was diverted (see Figure 2.9). Thus, all flows would continue in the same channels outside of the Project mine and process area, and there would be no substantial alteration of stream flows or patterns outside of the Project mine and process area. The impacts resulting from these alterations are below the level of significance

Precipitation falling on undisturbed portions of the Project mine and process area would be allowed to collect and flow through the area as before construction of the Project. Precipitation falling within the open pit boundaries would collect on, or infiltrate through, pit floors, thus reducing potential storm water runoff from the Project compared to the existing desert floor. Precipitation falling on the heap leach pad or within the pregnant or barren ponds would also remain within this closed hydrologic system. Depending on the porosity and permeability of the mine facility and the intensity of the precipitation, storm water runoff may be delayed (such as from rain falling on the porous waste rock stockpiles) or accelerated (such as from the relatively impervious roads). Regardless of the effect, because the Project mine and process area facilities which may accelerate, delay, or "capture" precipitation are such a minor percentage of the overall surface area of the drainage basins in which they are located, only a very minor delay, acceleration, or reduction in storm water flow in the major washes downstream of the Project mine and process area would result from the Project activities. Minor, ephemeral tributaries which are truncated by certain Project facilities (such as the heap leach pad) would have a reduction on runoff flow, although this flow reduction is not considered substantial and therefore would not be significant.

Surface runoff and drainage resulting from precipitation falling on the waste rock stockpiles, soil stockpiles, or on project roads and other disturbed areas within the Project mine and process area would be controlled using a number of Best Management Practices (BMPs). Among the methods of control would be collection and detention in sediment basins. Evaporation and infiltration would occur in the sediment basins, further reducing the potential for downstream sedimentation. If excess water is captured, it may be utilized in the mining, dust control, or heap leach processes. Based on experience at the Picacho Mine, it is expected that insignificant quantities of storm water would leave the Project mine and process area. The specific details of storm water management would be documented in a SWPPP, which would be prepared after approval of the Project mine, and implemented when the facility begins operations. This SWPPP would be a public document maintained on the Project mine and process area. Storm water flows would not result in a significant impact.

Stream Sedimentation and Quality Degradation:

The principal throughgoing stream channels appear to be undergoing very little geomorphic change (EMA 1996a). There is a potential for the erosion of materials from the Project soil stockpiles, waste rock stockpiles, and other Project facilities into the washes due to overland storm flow or from erosion by flows in the washes themselves during major precipitation events. Substantial erosion of Project facilities could result in substantial discharge of sediment into the watercourses, which could lead to the deposition of substantial sediment in these watercourses downstream of the Project mine and process area, and which could damage or bury the vegetation in the washes. Areas most susceptible to erosion, and thus, the production of sediment, would be steep, loose, waste rock or soil stockpile slopes adjacent to the major throughgoing watercourses; the outside banks of major turns in the washes, and the "at grade" haul and maintenance road crossings of the major stream channels within the Project mine and process area (and the two (2) "at grade" crossings of the western-most wash adjacent to the Project mine and process area by the relocated Indian Pass Road).

Best management practices to reduce the potential for erosion have been incorporated into the Proposed Action (see Section 2.1.11.2.3 and Section 4.1.2.3) which would also substantially reduce the potential for sedimentation in the ephemeral stream channels. These include placing rip rap on the outside bends of diverted stream channels, providing setbacks of facilities (such as the waste rock stockpiles) from the banks of throughgoing washes, placing berms around facilities as appropriate, and installing sediment basins around the facility designed to capture run off from the 100-year, 24-hour storm event for the entire Project mine and process area. In addition, the heap benches and berms would be constructed to provide for 100 percent containment of the precipitation from the 1-hour probable maximum precipitation (PMP) design storm event. Since the Project would use process solutions that could potentially be harmful to human health and the environment during the 20-year proposed operating life, the use of the PMP design was selected as the most stringent, prudent and reasonable value, compared to the 100-year/24-hour event or other smaller precipitation event). The PMP was calculated to be 4.65" by averaging the PMP values for Yuma, Arizona and El Centro, California. A conservative value of 5" was used in the design. Utilizing this approach would, under probable conditions, provide maximum protection to the environment from the escape of fluids from the heap leach facilities. Erosion control methods around facilities other than the heap leach would be designed to manage not less than a 20-year, 1-hour intensity storm event, in accordance with standards established by 14 CCR 3706(d) (SMARA regulations). The Proposed Action also includes compliance with the conditions of the Storm Water NPDES General Permit applicable to the Project, and preparation and compliance with the requirements of a Storm Water Pollution Prevention Plan (SWPPP) to control drainage and erosion. As a result, the Proposed Action is not anticipated to result in significant sedimentation.

Substantial quantities of various chemicals would be stored and used within the Project mine and process area (see Section 2.1.9.4), and substantial quantities of regulated waste (such as waste oil) would be generated (see Section 2.1.9.5). These materials could be released into the watercourses which flow through the Project area, either through spills directly into the washes or from overland flow of either the spilled material or contaminated soil. Minor spills of chemicals and regulated wastes may occur during the life of the Project, but would not result in any substantial degradation of surface water quality if promptly contained and collected and properly disposed of. Measures to reduce the potential for spills of chemicals or regulated waste have been included in the Proposed Action, which also includes sediment traps designed for the 100-year, 24-hour storm event to ensure no spilled material leaves the Project mine and process area, and measures to reduce erosion and sedimentation which may transport spilled materials or wastes to the watercourses. Together, these measures would reduce the potential for any surface water degradation to insignificance.

The heap leach pad system (heap, pad, ponds, etc.) would be designed to provide for 100-percent containment of the precipitation from the maximum probable one (1)-hour storm event occurring simultaneously with a 24-hour power outage while still maintaining a two-foot freeboard in the process and overflow ponds (see Section 2.1.8). This would reduce the potential for failure of the process facilities to contain all process solutions during high precipitation events, which might otherwise result in a discharge of process solution and sediment to the natural drainage channels. In addition, the waste characterization studies (EMA 1995; EMA 1996b) conducted on samples of waste rock and leached ore concludes that these materials are all properly classified as non-acid generating wastes, and that the leachates which may be formed from precipitation moving through the waste rock or leached ore would have very low concentrations of metals, which would not degrade the quality of surface waters. These effects would also be below the level of significance.

There is no evidence that implementation of the Proposed Action would result in any violations of any applicable state water quality standard, nor violate any applicable toxic effluent standard or prohibition.

Floodplain Encroachment

Pursuant to Sections 74400 through 74402 of Division 4 of Title 7 of the codified ordinances of Imperial County, a development permit is required to be obtained from the Flood Administrator before construction or developments begins within any area of special flood hazard (such as FEMA Zone A, but not Zone C). Sections 74500 through 74501 of Division 4 of Title 7 of the codified ordinances of Imperial County proscribe the standards of construction and standards for utilities which are to be followed when constructing structures within these special hazard areas. Based upon a review of the FEMA FIRM map for the Project area, none of the facilities located within the Project mine and process area would encroach upon any areas designated Zone A, and only a small portion of the buried water pipeline in the Project ancillary area is proposed to be constructed through an area designated Zone A (that in the portion of Zone A which crosses Indian Pass Road) [see Figure 3.8]. Construction in this Zone A section would be subject to these Imperial County standards and would require authorization from the Imperial County Flood Administrator. This would not be a significant effect.

Compliance with Executive Order 11988 would require the BLM (and other federal agencies granting applicable rights) to reference in the granted right those uses, if any, that are restricted under identified federal, state or local floodplain regulations in any floodplain. This is not a significant effect.

Ground Water Inflows:

The West Pit and East Pit are predicted to intercept the local ground water table at elevations of 211 feet and 88 feet AMSL, respectively. Thus, the projected final pit floor elevation of both the East Pit and the West Pit would intersect ground water within the bedrock aquifer. Because of the low permeability and porosity of the bedrock below the ground water table, little ground water is expected to enter the pits. Hydrologic investigations conducted within the area of the proposed pits indicate that hydraulic conductivity in the bedrock is very low (WESTEC, Inc. 1996a); however; these data were calculated from falling head and slug tests and, as such, are of limited value in accurately determining aquifer parameters. Furthermore, information collected to date indicates that the flow of substantial amounts of ground water from the alluvium bedrock contact into the open pits is highly unlikely. This is supported by the fact that approximately 60 percent of the exploration holes drilled in and around the proposed pits have been drilled using dry methods, and only a trace of water has been detected at the alluvium/bedrock contacts (see also Figure 3.11 and Figure 3.12). Should ground water be encountered in the pits during mining operations, it would be utilized in dust control operations, or collected and used in process operations, thus reducing the amount of ground water which would need to be produced from the ground water wells and consumed.

After the cessation of mining activities, it is possible that ground water seepage, surface runon or direct precipitation may accumulate in the bottom of either the East Pit. Calculations based on projected ground water inflow to the pit, annual precipitation, and annual evaporation for the East Pit indicate that the estimated annual evaporation rate is approximately 170 times the annual estimated ground water and precipitation inflow rate (WESTEC, Inc. 1996a). Because the project pit inflow estimates are based on limited data, additional calculations using hydraulic conductivity values ten (10 times higher were made to evaluate possible higher inflows to the pit. These calculations indicated that even in the event that inflow rates an order of magnitude greater than those expected based on existing data, annual evaporation would still exceed annual inflow (Personal Communication, John Heggeness, WESTEC, 1996). Thus, the formation of a pit lake in the bottom of the East Pit after the cessation of mining activities is not likely. The Proposed Action also proposes to conduct an assessment at the end of mining and to backfill the East Pit with waste rock to an elevation which would ensure that no standing water would remain in the pit bottom if the assessment indicates that there is a reasonable potential for a pit lake to form. This reduces the potential for the formation of a pit lake in the East Pit even further. (See also Section 4.1.3.2.2 for a discussion of the potential for the degradation of ground water quality as a result of evaporation and/or leaching of minerals from a pit lake, should it form.) The effects of any pit lake on ground water hydrology are less than significant. However, see Section 4.1.5.3.2 for a discussion of the potential adverse effects of a pit lake on wildlife.

The formation of localized moist areas, seasonal seeps, or ephemeral, localized ponds from ground water inflow, precipitation, or surface water runon, remains a possibility in the East Pit. The effects of these seeps on ground water hydrology are below the level of significance. However, see Section 4.1.5.2 for a discussion of the potential adverse effects of these seeps, etc. on vegetation and plant habitat.

Both the West Pit and the Singer Pit are proposed to be completely backfilled under the Proposed Action. However, if mining is suspended or terminated prior to backfilling of the West Pit above the ground water level, it is possible, but not probable, that a pit lake could form in the West Pit. Also, if mining is suspended or terminated prior to the complete backfilling of either the West Pit or the Singer Pit, formation of localized moist areas, seasonal seeps, or ephemeral, localized ponds from ground water inflow (for the West Pit only), precipitation, or surface water runon remains a possibility. These effects on ground water hydrology are below the level of significance. However, see Section 4.1.5.2 for a discussion of the potential adverse effects of these seeps, etc. on vegetation and plant habitat, and see Section 4.1.5.3.2 for a discussion of the potential adverse effects of a pit lake on wildlife.

"Waters of the United States":

The delineation of "waters of the United States" conducted for the Project (see Section 3.3.1.4) determined that there were approximately 114.5 acres of jurisdictional "waters of the United States" within the Project mine and process area. An assessment of the acreage of "waters of the United States" which would be affected by discharges of dredged or fill material (that is, altered by excavation or the addition of material) by Project activities within the Project mine and process area has been completed (LSA Associates, Inc. 1997b [see Appendix N to this EIS/EIR]). By comparing the layout of the Project facilities within the Project mine and process area to the delineated "waters of the United States," it is estimated that approximately 77.4 acres of "waters of the United States" would be directly affected through the permanent filling or excavation of these "waters of the United States" within the Project mine and process (see Figure 4.1). Indirect impacts to other "waters of the United States" would also occur, both within and immediately adjacent to the Project mine and process area, principally through the isolating or de-watering of a given reach of drainage course by excavating or filling upstream areas. However, such indirect impacts would be restricted to short reaches of tributary stream channels immediately down-gradient of the filled or excavated areas, since all of the major stream channels have been diverted to maintain throughgoing flows.

The draft alternatives analysis prepared under Section 401(b)(1) of the Clean Water Act (LSA 1997b) concludes that the Proposed Action is the least environmentally damaging practicable alternative. In addition, Section 3.3.1 of this EIS/EIR describes the hydrologic function, and Section 3.5 describes the ecosystem values, of the "waters of the United States" located within the Project mine and process area. Section 4.1.2.3, Section 4.1.3.1.3, and Section 4.1.5.4 of this EIS/EIR discuss the appropriate and practicable steps which should be taken to minimize potential adverse impacts of the discharge on these hydrologic functions and aquatic ecosystem values. Alternatives to the proposed discharge to or fill of "waters of the United States" within the Project mine and process area are discussed in Section 2.2 of this EIS/EIR; this analysis supports the conclusion that there are no practicable alternatives to the proposed discharge which would have less adverse impact on the aquatic ecosystem. Section 4.1.3.1.2 concludes that the discharges would not cause or contribute to violations of any applicable state water quality standard, violate any applicable toxic effluent standard or prohibition, or cause or contributed to substantial degradation of the "waters of the United States". Section 4.1.5.3.3 concludes that the mitigated effects of the Proposed Action on the only effected endangered species (desert tortoise) would be below the level of significance, and the Biological Assessment submitted by the BLM to the USFWS for the USFWS Biological Opinion concludes that, with mitigation, the Proposed Action would not jeopardize the continued existence of the desert tortoise. It is also anticipated that, pursuant to 33 CFR 325.4, the ACOE would consider all of the mitigation measures proposed within this EIS/EIR which may be imposed as conditions of approval by the BLM, County of Imperial, and other federal, state, and local agencies which would achieve the objectives of the ACOE Section 404 program, and especially the conditions of approval proposed in the Stream Alteration Agreement between Glamis Imperial and the CDFG. Accordingly, the effects of the Proposed Action on "waters of the United States" is below the threshold of significance.

4.1.3.1.3. Measures Incorporated by Project Design and Regulation and Mitigation Measures

Although the assessment of impacts assumes the implementation of those measures incorporated into the project design or required by regulation which avoid or reduce potentially significant impacts, these measures are expressly identified below to facilitate review and implementation. Mitigation measures, if any, which are proposed to avoid or reduce potentially significant effects are separately identified.

Measures Incorporated by Project Design Which Avoid or Reduce Potentially Significant Impacts:

See also those measures described in Section 4.1.2.3 designed to mitigate erosion and Section 4.1.5.4 designed to mitigate wildlife impacts.

4.1.3.1-1: Major watercourses shall be diverted only to the extent necessary to protect Project facilities, and shall be diverted back into the same wash system after as short a diversion as practical. Permanent diversion channels shall be built to approximate the original drainage system in both gradient and channel geometry, and shall be engineered to adequately contain and deliver stream flows resulting from the 100-year/24-hour precipitation event. The diversion system shall also be designed to adequately contain and deliver stream flows predicted from the 500-year, 24-hour precipitation event.
4.1.3.1-2: All chemicals shall be stored in conformance with applicable local, state and federal regulations. All non-mining wastes shall be stored in secondary containment areas, as required, and disposed of off-site in an approved landfill. Regulated wastes shall be recycled or disposed of in conformance with all applicable local, state and federal laws and regulations, and in a manner approved by the responsible regulatory agencies.
4.1.3.1-3: Major maintenance of equipment shall be conducted within the concrete-paved and bermed areas of the maintenance yard to the extent possible to minimize accidental discharges of waste lubricants and other materials to the ground.
4.1.3.1-4: Each phase of the heap leach pad system (heap, pad, ponds, etc.) shall be designed to provide for 100-percent containment of the precipitation from the maximum probable one (1)-hour storm event occurring simultaneously with a 24-hour power outage while still maintaining a two-foot freeboard in the process and overflow ponds, and shall be consistent with the requirements of the CRWQCB .
4.1.3.1-5: Diversion channels shall be designed to prevent the abrupt diversion of flows from their natural courses, and shall provide sufficient natural protective materials at the points of diversions where necessary to protect the diversion works. All designs for the diversion channels shall be signed and stamped by an engineer registered to practice in California and submitted to the Imperial County Public Works Department for approval prior to commencement of construction.

Measures Incorporated by Regulation Which Avoid or Reduce Potentially Significant Impacts:

See also those measures described in Section 4.1.2.3 designed to mitigate erosion and Section 4.1.5.4 designed to mitigate wildlife impacts.

4.1.3.1-6: Project facilities shall not be constructed within special flood hazard zones (Zone A) as noted on Federal Emergency Management Agency (FEMA) National Flood Insurance Program Flood Insurance Rate Map (FIRM) for Imperial County, California (Unincorporated Areas), Panel 700 of 1175, Community-Panel Number 060065 0700 B, Effective Date: March 15, 1984, except as may be authorized by a Development Permit approved by the Imperial County Flood Administrator pursuant to Division 4 of Title 7 of the codified ordinances of Imperial County and, if applicable, restrictions contained in the approvals of the appropriate federal authorizing agencies.
4.1.3.1-7: Applicant shall acquire and comply with the necessary approvals from the U.S. Army Corps of Engineers for all jurisdiction "waters of the United States" under Section 404 of the Clean Water Act which may be dredged or filled through Project actions.

Mitigation Measures Proposed to Avoid or Reduce Potentially Significant Impacts:

See also those measures described in Section 4.1.5.4 designed to mitigate wildlife impacts and those measures described in Section 4.1.5.2 designed to mitigate adverse effects on vegetation and plant habitat.

No mitigation measures are proposed or recommended.

4.1.3.1.4. Unavoidable Adverse Effects and Level of Significance After Mitigation

Implementation of the Proposed Action would result in unavoidable, although not significant, adverse effects to surface water flows within the Project mine and process area as a result of the permanent diversion of portions of the ephemeral stream channels within the Project mine and process area.

4.1.3.2. Ground Waters

4.1.3.2.1. Assumptions and Assessment Guidelines

Substantially degrade water quality;
Contaminate a public water supply;
Substantially degrade or deplete ground water resources; or
Interfere substantially with ground water recharge.

4.1.3.2.2. Impacts of the Proposed Action

In addition to other changes, this section has been modified from the November 1996 Draft EIR in response to comments to: clarify the relationship of the ground waters in the Project area to the Colorado River aquifer; add a discussion of the absence of impacts to seeps and shallow water wells located in the vicinity of the Project ground water well field area; reduce the estimated quantity of water seeping from All American Canal to the Amos-Ogilby-East Mesa Basin; include a discussion of Imperial County's Ground Water Management Ordinance and requirement for permit; and discuss the relationship between the ground waters in Picacho Wash Basin and the Project mine and process area.

Ground Water Production:

Ground water would be produced to supply water for heap leach processing and other service water requirements. An annual maximum of 1,200 afy of ground water would be supplied from up to four (4) wells drilled in the Project ground water well field area within the Project ancillary area southwest of the Project mine and process area. Imperial County's "Ground Water Management Ordinance" requires that a Ground Water Extraction Permit be obtained prior to commencing the drilling of ground water production wells. The Imperial County Public Works Director is required to determine whether sufficient ground water is available for the proposed use based on the projected use of ground water by the Project in accordance with Section 56614.01(b) of the ordinance. Exemptions from obtaining a permit are allowed for the drilling of production exploration wells.

The projected drawdown of ground water levels in the vicinity of the Project ground water well(s) as a function of time was calculated using data collected during the test of ground water exploration well PW-1, which was drilled under the Ground Water Management Ordinance permit exemption for production exploration wells (WESTEC, Inc. 1996a; see Table 4.2). These calculations assumed an individual ground water supply well, located in the vicinity of ground water exploration well PW-1, would produce approximately 725 gpm, or 1,170 afy, for 20 years. An average hydraulic conductivity of 16 ft/day (5.6 x 10^-3 cm/sec) was assumed for all calculations. Several different drawdown scenarios were calculated using a range of aquifer parameters. The calculations were performed using an aquifer thickness of 300 feet to 600 feet, and a storage coefficient ranging from 0.02 to 0.002. The calculations show that drawdowns ranging from 1.5 feet to 6.4 feet are projected to occur at distances of approximately 50,000 feet (approximately nine and one-half (9.5) miles) from the pumping well after 20 years of continuous pumping (WESTEC, Inc. 1996a). Maximum predicted drawdown at a distance of only 1,000 feet from the modeled water supply well is 19.2 to 24.4 feet. These results would likely be conservative because they assume: no recharge of the ground water basin (previously estimated at 30,000 afy); all wells would be located in the same aquifer as the production well; and conservative thicknesses for the aquifer (thicknesses of 1,000 feet have actually been measured).

Table 4.2

Pumping Rate
(gpm)
Aquifer Thickness
(ft)
Transmissivity
(ft²/day)
Storage Coefficient
Distance to Drawdown Contour in feet

1,000

10,000

20,000

50,000

725¹ 300 4,800 0.02 19.2 8.6 5.4 1.8

725 400 6,400 0.02 14.9 6.9 4.5 1.7

725 500 8,000 0.02 12.2 5.8 4.0 1.6

725 600 9,600 0.02 10.4 5.1 3.4 1.5

725 300 4,800 0.002 24.4 13.8 10.6 6.4

725 400 6,400 0.002 18.8 10.8 8.5 5.3

725 500 8,000 0.002 15.4 9.0 7.1 4.6

725 600 9,600 0.002 13.0 7.7 6.1 4.0

¹This pumping rate is equivalent to approximately 1,200 afy.
Source: WESTEC, Inc. 1996a

Conservative ground water level drawdowns were also calculated for three (3) specific wells located in the vicinity of the Project: the Gold Rock Ranch well, located approximately four and one-half (4.5) miles south-southwest of well PW-1; the Mesquite Mine well GF-3A, located approximately eight (8) miles northwest of well PW-1; and the American Girl Mine well 26-2, located approximately eight (8) miles south of well PW-1 (WESTEC, Inc. 1996a; see Table 4.3). For an aquifer with a thickness of 500 feet (a saturated thickness of 500 feet was used for the alluvial aquifer to account for the thickening of the aquifer to the southwest (Dutcher, et. al. 1972)) and a storativity value of 0.02, a Project well pumping at a rate 725 gpm (approximately 1,200 afy) over a period of 20 years was predicted to result in a drawdown of 3.7 feet in the Gold Rock Ranch well, and a drawdown of 1.8 feet in both the Mesquite Mine well and the American Girl Mine well (WESTEC, Inc. 1996a). These conservative drawdowns represent a three (3) percent, one-half (0.5) percent, and one and one-half (1.5) percent drawdown of the depth of the Gold Rock Ranch, Mesquite Mine, and American Girl Mine ground water wells, respectively, over the life of the Project. These drawdowns, and their effects on the projects and the ground water aquifer, are below the level of significance.

Table 4.3

Pumping
Rate
(gpm)
Aquifer
Thickness
(ft)
Transmissivity
(ft²/day)
Storage
Coefficient Gold Rock
Ranch Well
(126 ft. water column)
4 miles from well Mesquite Mine Well
(470 ft. water column)
8 miles from well American Girl Mine Well 26-2
(110 ft. water column)
9 miles from well

(ft of drawdown)

725 500 8,000 0.02 3.7 1.8 1.8

Source: WESTEC, Inc. 1996a

Wells for the production of ground water for wildlife (guzzler wells, or "extraction devices"), which are powered by windmills, have been drilled within the Algodones Sand Dunes north of Highway 78 and west of the Southern Pacific railroad tracks by the U.S. Bureau of Reclamation (Personal Communication, Randy Rister, ICFGC, June 26, 1997). The wells were drilled to depths of only 75 to 150 feet below ground surface, or approximately 200 feet AMSL. As static ground water levels in the Project ground water production area are greater than 500 feet below ground surface, or approximately 0 feet AMSL, and the guzzler wells are all located further than 20 miles northwest of the Project ground water well field, ground water production for the Project should have no effect on the water available to the guzzler wells.

Several small water seeps are located northwest to southwest of the Project ground water well field area in the vicinity of and adjacent to the eastern side of the Algodones Sand Dunes (Personal Communication, Randy Rister, ICFGC, June 26, 1997). The source of the water for the seeps has not been identified in any area hydrologic studies; however, because the depth to ground water in the ground water well field area is several hundred feet, it is believed that the seeps result from near surface flows of water as sub-flow in ephemeral stream channels, or the surface outflow of precipitation which flows through the sand dunes. In either case, ground water production from the Project ground water well field area, produced from depths of greater than 500 feet below ground surface and at least five (5) miles distant, would not impact the shallow source of the seeps. Furthermore, two (2) production wells, one (1) at the Gold Rock Ranch and one (1) at the Mesquite Mine are both closer to the seeps than the Project ground water well field. No known effects to the seeps from the pumping of these two (2) wells have been observed.

It is unlikely that the Project's ground water production would affect ground water located in the Picacho Wash Basin. A number of published hydrogeologic studies have placed a ground water divide between the Amos-Ogilby-East Mesa Basin and the Picacho Wash Basin, that is, between the Cargo Muchacho Mountains and Picacho Peak (see Figure 3.10), such that ground water would flow away from, rather than toward or across, this divide (Bedinger, et al. 1983; Loeltz, et. al. 1975; and Dutcher, et al. 1972). Furthermore, bedrock depth in the surface water divide between the "Picacho Wash Drainage Basin" and the "Indian Wash Drainage Basin" (at an elevation of approximately 960 feet) is assumed to be shallow, no deeper than several hundred feet, since this surface water divide is bounded by the exposed bedrock on the northeast and west-southwest. The depth to bedrock in the Project mine and process area is zero (0) to 300 feet below ground surface (860 to 560 feet AMSL). Exploration drilling to the southeast of the Project mine and process area has also encountered bedrock at relatively shallow depths (Personal Communication, Dan Purvance, Chemgold, 1996) (see Figure 3.12). Thus, while bedrock is not exposed at the surface of the surface water divide between the "Indian Wash Drainage Basin" and the "Picacho Wash Drainage Basin," and no data (gravity, etc.) has been made available to judge the depth to bedrock in this area, it is very likely that a subsurface bedrock barrier to ground water flow between the Amos-Ogilby-East Mesa and the Picacho Wash ground water basins exists in the same location as the surface divide. Any effect to ground water in the Picacho Wash Basin, were it to occur, would be below the level of significance.

Comparing the amount of water projected to be extracted during the life of the Project to the estimated usable and recoverable stored water and estimated recharge, the Project should not substantially impact the alluvial ground water resources of the area. The Project's maximum annual extraction rate of 1,200 afy represents about four (4) percent of the annual 30,000 acre-feet recharge of the entire Amos-Ogilby-East Mesa Basin. Over the 20-year projected life of the Project, the Project would use an estimated 24,000 acre-feet of water, which represents approximately 0.01 percent of the estimated 230,000,000 acre-feet of useable and recoverable water in the Amos-Ogilby-East Mesa Basin (WESTEC, Inc. 1996a), or approximately 0.02 percent of the estimated 126,000,000 acre-feet of useable and recoverable water in the Amos-Ogilby Basin alone. These effects are below the level of significance.

Ground water inflows into open pits are predicted to be very small, only 1.5 gpm (2.4 afy) for the West Pit and 0.7 gpm (1.1 afy) for the East Pit. This rate of ground water inflow would have a negligible effect on ground water levels in the vicinity of the pits or beyond. Ground water entering either of these pits during mining operations would be utilized in dust control operations, or collected and used in process operations. No ground water is anticipated to be encountered in the Singer Pit. The impacts from ground water inflow into the pits to the surrounding aquifer is below the level of significance.

Ground Water Quality:

Given the depth to ground water in the Project mine and process area, there is little potential for degradation of ground water quality from accidental spills or leakage of chemicals or regulated wastes from containment areas or from the leach pad facility. Minor spills of chemicals and regulated wastes may occur during the life of the Project, but should not result in any substantial degradation of ground water quality if promptly contained and collected and properly disposed of. The Proposed Action also includes measures to reduce the potential for spills of chemicals or regulated waste to below the level of significance.

Based upon the high acid neutralization potential reported for the samples of waste rock and leached ore in the Waste Characterization Study (see Appendix C-1), water from rainfall moving through waste rock or neutralized leached ore would not be likely to generate acidic waters which could degrade ground water quality. In addition, the results of the SPLP extractions conducted on the same rock materials indicate that waters from rainfall would not be likely to leach substantial quantities of metals from these rock materials, and ground water quality would not be degraded. This impact would not be significant.

The heap leach pad has been designed with a dual liner system to decrease the potential for any leakage of leach solution. The first portion of the leach pad would be constructed with a liner consisting of a composite of 40-mil polyvinyl chloride (PVC) primary and 20-mil PVC secondary geomembrane liners placed directly on a minimum of four (4) inches of compacted, fine-grained, bedding material. Similar liners were approved by the CRWQCB and constructed by others at the nearby American Girl mine in 1995. The USEPA is reported to have recognized the acceptability (for seamabilty, punctureability and installability) of 20-mil PVC liners for landfills (Peggs 1992), and the United States Bureau of Reclamation (USBR), which has installed over 40 million square feet of PVC in canal linings since 1968, has specified 20-mil thicknesses since the early 1980's (Comer, et al. 1996). The pad is also designed to drain by gravity into the solution collection system and solution ponds so that there is only a minimum layer of saturated drain rock (typically less than one (1) foot) above the liner, thus reducing the hydraulic head across the liner.

Monitoring of both the vadose zone and ground water for evidence of leakage of leach solution would be conducted under the Proposed Action. The vadose zone monitoring system would be placed under only approximately 25 percent of the leach pad liner and process ponds, but would be located directly under the lowest points of each cell of the heap leach pad and the process ponds. Because of its placement, this vadose monitoring system should be capable of detecting any substantial leak through the double liner system of the heap leach pad and process ponds. The CRWQCB would typically require monthly sampling of both the vadose zone and ground water monitoring points and analysis for the constituents of concern (those constituents of the process solution, such as cyanide and select metals, which if detected in the vadose zone or ground water monitoring points would likely indicate a leak). Results would be required to be reported monthly, more rapidly if evidence of a leak is detected. Detected leaks under the pad would be evaluated and corrected under the supervision of the CRWQCB , either through excavation of the heaped material and repair of the liner, if the height of the heap at the time of detection of the leak is not too great, or through reducing or eliminating the application of leach solution to that portion of the heap located over the leak. Leaks under the process ponds would be repaired after emptying the appropriate pond. Leaks are not common place and are usually detected while still small. Remediation of leaked solution is typically not required because the weak cyanide solution degrades rapidly as the pH drops and it is oxidized in the air, and the soil and rock material above the ground water can attenuate the concentrations of the metals. Taken together, these measures reduce the potential for any ground water quality degradation from the heap leach pad and process ponds to insignificance.

It is also unlikely that any degradation of ground water in the Picacho Wash Basin would result from any accidental spills or leakage of chemicals or regulated wastes from Project containment areas or from the leach pad facility. In addition to the presumed bedrock ground water barrier located between the Indian Wash portion of the Amos-Ogilby-East Mesa Basin and the Picacho Wash Basin, the ground water gradient established by the data presented in Appendix E-1 and Appendix E-2 clearly trends down to the southwest, away from the Project mine and process area toward the area of the Project production well field (near well PW-1), and away from the divide between the Indian Wash portion of the Amos-Ogilby-East Mesa Basin and the Picacho Wash Basin. Thus, impacts to the ground water of the Picacho Wash Basin would be below the level of significance.

Pit Water Quality:

As discussed in Section 4.1.3.1.2, the formation of a pit lake in the bottom of the East Pit following the completion of pit mining is not likely to occur, and the Proposed Action includes backfilling the pit with waste rock material to an elevation that is above the predicted level of any pit lake should a study reasonably determine that a pit lake may form (see Section 2.1.3). Based upon the high acid neutralization potential reported for the samples of waste rock and leached ore in the Waste Characterization Study (see Appendix C-1), ground water moving through backfilled waste rock in either the West Pit or East Pit would not be likely to generate acidic waters. In addition, the results of the SPLP extractions conducted on the same rock materials indicate that the ground waters would not be likely to leach substantial quantities of metals from these rock materials, and the ground water quality would likely remain relatively unchanged.

To further assess the potential interactions which may occur between the waste rock which may be backfilled into either the West Pit or East Pit and the ground water which may enter either pit, an additional geochemical investigation was conducted (see Appendix C-2) to supplement the Waste Characterization Study. Samples of each of the rock types which may be backfilled into either the West Pit or East Pit were processed by several standard USEPA chemical-extraction techniques to conservatively simulate what constituents may be leached from the rock if exposed to ground waters entering a backfilled pit. Modeling was then conducted using analyses of the extracted constituents, analyses of the ground water, and the mineral phases of the rock to evaluate impacts to the ground water after equilibration.

Representative composite samples of each of the principal rock types to be mined (sericite gneiss, biotite gneiss, and gravels) (see Section 3.1.1) were first extracted using USEPA Method 1312, which is designed to determine the mobility of both organic and inorganic constituents in liquids, soils and wastes. It uses a 60/40 weight percent of sulfuric acid/nitric acid diluted with deionized water to a pH of 5.0 added to the solid sample, which is then agitated for 18 hours. The resultant liquid (leachate) is then filtered and analyzed. The analytical results from each of the three (3) samples show that the extracted constituents are in low concentrations, in most cases at or below the respective concentrations in the ground water currently in the undeveloped pits, and are below current California water quality standards except the primary selenium maximum contaminant limit (MCL) and the secondary manganese MCL (see Appendix C-2).

Six (6) additional representative composite samples of four (4) rock types (sericite gneiss, biotite gneiss, volcanics, and gravels) (see Section 3.1.1) were also collected from the locations of both the East Pit and West Pit and extracted using USEPA Method 1320, the Multiple Extraction Procedure, which is "designed to simulate the leaching that a waste would undergo from repetitive precipitation of acid rain on an improperly designed sanitary landfill. The repetitive extractions reveal the highest concentration of each constituent that is likely to leach in a natural environment." (USEPA 1986). As such, this test is very conservative for the types of geologic materials and the environment anticipated within the backfilled Project pits.

The first Method 1320 extraction uses USEPA Method 1310 (Extraction Procedure (EP) Toxicity Test Method) to leach constituents from the solid by agitating for 24 hours with deionized water which is maintained at a pH of 5.0 with acetic acid. The resulting leachate is then filtered and analyzed. Nine (9) subsequent extractions are then sequentially undertaken on the solid residual using a 60/40 weight percent of sulfuric acid/nitric acid diluted with deionized water to a pH of 3.0, each agitated for 24 hours. The resultant leachate from each extraction is filtered and analyzed.

The analytical results from the six (6) samples used in the USEPA Method 1320 extraction show that the concentration of the constituents in the first extraction are much higher than in subsequent extractions (see Appendix C-2). TDS and alkalinity concentrations were uniformly higher than in the ground water in the first extraction for all rock types, as were the concentrations of aluminum, calcium, and manganese. The pH was also uniformly lower than the ground water, reflecting the acidic extraction fluid. Concentrations of copper, lead, potassium, strontium, titanium, zinc, barium, chromium, thallium, beryllium, magnesium, cadmium, arsenic, or silver in the first extractions of some samples also slightly exceeded the respective constituent concentrations in the ground water. Constituent concentrations in extractions 2 through 10 were typically lower than concentrations in either the ground water or extraction 1, although iron concentrations increased in nearly all samples in the later extractions, reflecting the artificially low pH in the extraction fluid (see Section 2.1.4) and the lack of alkalinity remaining in the sample.

The analytical results of the Method 1320 extractions show that high concentrations of calcium and available alkalinity may leach from the backfilled material, probably due to the rigorous leaching procedure and the dissolution of calcite (CaCO₃) which is present as a secondary mineral phase in the rocks. The relatively high manganese concentrations in the Method 1320 extraction leachates are also due to the rigorous leaching method and the dissolution of secondary manganese minerals (oxyhydroxides) in the rock.

Geochemical models were also run to test the effects of the ground water flowing into the pits and equilibrating with the backfilled material under earth surface conditions. The results of these geochemical models were then evaluated relative to existing (background) ground water quality and to the potential impacts to ground water quality downgradient from the pits. Because calcite (CaCO₃) is the most reactive mineral phase present in the rocks, the models assumed that inflowing ground water would equilibrate with calcite and with atmospheric carbon dioxide (CO₂). The model inputs were derived from the analytical results of the ground water samples collected in the areas of the pits, the Method 1312 extractions, and the Method 1320 extractions. The results of all of the geochemical models predict that the dissolved constituent concentrations present in the ground water which has equilibrated with the backfilled material in the pits would be at, or below, the current concentrations present in the ground water. Therefore, no impacts to ground water quality are expected to occur from the complete or partial backfilling of any of the Project pits.

4.1.3.2.3. Measures Incorporated by Project Design and Regulation and Mitigation Measures

Although the assessment of impacts assumes the implementation of those measures incorporated into the project design or required by regulation which avoid or reduce potentially significant impacts, these measures are expressly identified below to facilitate review and implementation. Mitigation measures, if any, which are proposed to avoid or reduce potentially significant effects are separately identified.

Measures Incorporated by Project Design Which Avoid or Reduce Potentially Significant Impacts:

See also those measures described in Section 4.1.3.1.3 designed to mitigate water quality degradation from chemical spills and use, Section 4.1.12.3 designed to respond to and remediate any chemical spills, and Section 4.1.5.4 designed to eliminate the possibility of a pit lake to mitigate potential impacts to wildlife.

4.1.3.2-1: To prevent excessive drawdown or possible damage to the well or pumping system, ground water production from well PW-1 shall be limited to a maximum average of 550 gpm unless a higher pumping rate, supported by reasonable proof of increased well efficiency, is approved by the ICPWD. The maximum average production rate from each additional production well drilled shall be limited to that rate which prevents excessive drawdown or possible damage to the well or pumping system.
4.1.3.2-2: The total annual ground water production rate shall not exceed 1,200 afy.

Measures Incorporated by Regulation Which Avoid or Reduce Potentially Significant Impacts:

4.1.3.2-3: Ground water production and monitoring wells shall be plugged and abandoned in conformance with applicable regulatory requirements, including 14 CCR 3713(a).
4.1.3.2-4: The heap leach pad shall be designed, constructed and operated in conformance with the specifications, requirements and prohibitions of Waste Discharge Requirements issued by the CRWQCB .
4.1.3.2-5: The heap leach pad shall be monitored in conformance with the requirements of the Monitoring and Reporting Program issued by the CRWQCB . This would include collection of groundwater quality baseline data prior to mine development.
4.1.3.2-6: Applicant shall obtain approval from the ICPWD of a "Ground Water Management Ordinance" permit prior to drilling any ground water production well intended for continued use. Production of ground water from the Project ground water well field shall be monitored and reported to the ICPWD consistent with the requirements of this permit.

Mitigation Measures Proposed to Avoid or Reduce Potentially Significant Impacts:

No other mitigation measures are proposed or recommended.

4.1.3.2.4. Unavoidable Adverse Impacts and Level of Significance After Mitigation

Implementation of the Proposed Action would result in the unavoidable, but not significant, loss of ground water produced from the ground water well field, and may result in the unavoidable loss of minor quantities of ground water if exposed as seeps in the walls of the open pit after the cessation of mining.

Effects of the Proposed Action to ground water resources would be below levels of significance.

4.1.4. Air Resources

4.1.4.1. Assumptions and Assessment Guidelines

Violate any regulatory requirement of the ICAPCD; or
Violate any ambient air quality standard; or
Contribute substantially to an existing or projected air quality violation; or
Expose sensitive receptors to substantial pollutant concentrations.

4.1.4.2. Impacts of the Proposed Action

In addition to other changes, this section has been substantially modified from the November 1996 Draft EIR in response to comments to: recalculate fugitive emissions for travel on unpaved roads (and other revisions to reflect changes in the Proposed Action); and add additional cumulative analysis for air quality requested (cumulative analysis extended).

Air Pollutant Emission Sources and Emissions:

The Proposed Action consists of many activities and operations, each of which may have the potential to emit air pollutants. Rule 101 (Definitions) of the Rules and Regulations of the ICAPCD (Rules) defines a "source" as "a specific device, article, or piece of equipment from which air contaminants are emitted, or the distinct place (such as with fires or other chemical activity) from which air pollutants are emitted." Rule 207B. (New and Modified Stationary Source Review-Definitions) goes further to define "emissions unit" as "an identifiable operation or piece of process equipment such as an article, machine, or other contrivance which emits, has the potential to emit, or results in the emissions of any affected pollutant directly or as fugitive emissions." Rule 101 goes on to define "fugitive emissions" as "those emissions which cannot reasonably pass through a stack, chimney, vent or other functionally equivalent opening." A comprehensive list of each of the identified individual potential sources of Project air pollutant emissions ("emission units"), organized into "emission groups" of similar activities (such as mining, heap leaching, etc.), are presented in Table 4.4.

Table 4.4

LIST OF POTENTIAL EMISSION SOURCES AND TYPE FOR THE PROPOSED ACTION

Emission Unit
Emission Unit Description
Emission "Source" Type

Point Fugitive Mobile Other

Emission Unit Group 1: Mining Activity

1.001 Drilling - Waste Rock X

1.002 Drilling - Ore X

1.003 Blasting - Waste Rock X

1.004 Explosives Detonation - Waste Rock Blasting X

1.005 Blasting - Ore X

1.006 Explosives Detonation - Ore Blasting X

1.007 Waste Rock Loading X

1.008 Ore Loading X

1.009 Waste Rock Dumping X

1.010 Ore Dumping X

1.011 Waste Rock Dozing X

1.012 Waste Rock Hauling X

1.013 Ore Hauling X

1.014 Ammonium Nitrate Prill Silo Loading X

1.015 Ammonium Nitrate Prill Silo Unloading X

1.016 Wind Erosion (Waste Rock Stockpile) X

1.017 Wind Erosion (Soil Stockpiles) X

1.018 Haul Truck (Combustion) X

1.019 Mine Dozer (Combustion) X

1.020 Drill Rig (Combustion) X

1.021 Loader (Combustion) X

1.022 Clean-Up Loader (Combustion) X

Emission Unit Group 2: Heap Leaching Activity

2.001 Portable R-O-M Lime Silo Loading X

2.002 Portable R-O-M Lime Hopper Loading X

2.003 Lime Application to Ore X

2.004 Ore Ripping/Spreading/Dozing X

2.005 Heap Leach Dozer (Combustion) X

2.006 Cyanide Application and Leaching X

2.007 Pregnant Solution Pond X

2.008 Barren Solution Pond X

2.009 Wind Erosion (Heap Leach Pad) - Non-Leach X

2.010 Wind Erosion (Heap Leach Pad) - Leach X

Emission Unit Group 3: Process Plant

3.001 Carbon Adsorption Tank 1 X

3.002 Carbon Adsorption Tank 2 X

3.003 Carbon Adsorption Tank 3 X

3.004 Carbon Adsorption Tank 4 X

3.005 Carbon Adsorption Tank 5 X

3.006 Acid Wash Tank X X

3.007 Cyanide Make-up Tank X

3.008 Strip Tank X

3.009 Electrowinning Cell X X

Emission Unit Group 4: Refining

4.001 Mercury Retort Furnace (Electric) X

Emission Unit Group 5: Laboratory

5.001 Jaw Crusher X

5.002 Pulverizer X

5.003 Fume Hood X

5.004 Waste Acid Tank X

Emission Unit Group 6: Shop Area

6.001 Main Diesel Tank 1 X

6.002 Street Diesel Tank X

6.003 Unleaded Gasoline Tank X

6.004 Coolant Tank X

Emission Unit Group 7: Mine & Process Area Support Activities

7.001 Water Truck (Combustion) X

7.002 Water Truck Traffic X

7.003 Backup Diesel-Fueled Generator X

7.004 Mobile Light Plant - Pit #1 X

7.005 Mobile Light Plant - Pit #2 X

7.006 Mobile Light Plant - Heap X

7.007 Mobile Light Plant - WRS X

7.008 Cable Reel Machine X

7.009 Grading of Road Surface X

7.010 Grader (Combustion) X

Emission Unit Group 8: Other Mobile Emission Units

8.001 On-Site Delivery Truck Traffic X

8.002 On-Site Light Vehicle Traffic X

8.003 Off-Site Delivery Truck Traffic X

8.004 Off-Site Light Vehicle Traffic X

8.005 On-Site Delivery Truck (Combustion) X

8.006 On-Site Light Vehicle (Combustion) X

In addition to being organized into emission groups, these emission units can also be characterized by the "type" of emission unit. For the sake of this analysis, four (4) different "types" of emission units were identified which are applicable to the Project: stationary "point" sources (e.g., the diesel-fuel emergency electric generator); "fugitive" sources (i.e., those which do not emit pollutants from single points, but from diffuse areas (e.g., dust generated by vehicles moving on unpaved roads or windblown dust)); mobile combustion sources (e.g., the "tailpipe" emissions from haul trucks, dozers, etc.); and "other" sources (e.g., vapor emissions from the storage of fuel in storage tanks). Table 4.4 also lists the emission "type" of each of the Project emission sources.

Estimates of the annual emissions of each applicable criteria air pollutant from each emission unit during full operation of the Project were prepared using generally available emission estimating techniques and operational parameters for each of the emission units as provided by Glamis Imperial, assuming the implementation of the "emission control" techniques proposed to be implemented as a part of the Proposed Action to reduce emissions (such as the watering of roads) [see Appendix O of this EIS/EIR]. Table 4.5 provides a summary of the maximum estimated daily (in pounds per day) and annual (in tons per year) regulated (criteria) air pollutant emissions expected from the Project during full operations. During the periods of Project construction, and post-Project reclamation, emissions from the Project would be limited to emissions of fugitive particulate matter from loading, hauling, dumping, dozing, and vehicular traffic in the Project area as well as combustion emissions from mobile sources.

Table 4.5

SUMMARY OF TOTAL CALCULATED EMISSION OF REGULATED AIR POLLUTANTS

Emission Unit No.
Emission Unit Description
Regulated Air Pollutants

TSP
PM₁₀
SOx
NOx
CO
VOCs /ROGs

(lbs/day)

(tons/yr)

(lbs/day)

(tons/yr)

(lbs/day)

(tons/yr)

(lbs/day)

(tons/yr)

(lbs/day)

(tons/yr)

(lbs/day)

(tons/yr)

Emission Unit Group 1: Mining Activity

1.001 Drilling - Waste Rock 7.15 0.93 3.58 0.47 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

1.002 Drilling - Ore 3.58 0.47 1.79 0.23 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

1.003 Blasting - Waste Rock 149.00 13.00 74.70 6.51 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

1.004 Explosives Detonation - WR Blasting 0.00 0.00 0.00 0.00 45.40 3.96 386.00 33.60 1,530.00 133.00 0.00 0.00

1.005 Blasting - Ore 0.00 6.51 0.00 3.25 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

1.006 Explosives Detonation - Ore Blasting 0.00 0.00 0.00 0.00 0.00 1.98 0.00 16.80 0.00 66.60 0.00 0.00

1.007 Waste Rock Loading 69.50 8.24 32.90 3.90 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

1.008 Ore Loading 34.70 4.12 16.40 1.95 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

1.009 Waste Rock Dumping 171.00 20.30 80.90 9.60 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

1.010 Ore Dumping 85.50 10.10 40.50 4.80 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

1.011 Waste Rock Dozing 33.70 6.15 4.31 0.79 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

1.012 Waste Rock Hauling 338.00 39.30 152.00 17.70 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

1.013 Ore Hauling 169.00 19.60 76.10 8.84 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

1.014 Ammonium Nitrate Prill Silo Loading 0.50 0.06 0.25 0.03 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

1.015 Ammonium Nitrate Prill Silo Unloading 0.45 0.06 0.23 0.03 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

1.016 Wind Erosion (Waste Rock Stockpiles) 17.90 3.20 8.97 1.60 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

1.017 Wind Erosion (Soil Stockpiles) 4.49 0.80 2.24 0.40 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

1.018 Haul Truck (Combustion) 120.00 21.90 62.50 11.40 266.00 48.50 2,440.00 445.00 1,050.00 192.00 116.00 21.10

1.019 WRS Dozer (Combustion) 6.34 1.16 3.30 0.60 13.40 2.44 123.00 22.40 52.90 9.65 5.83 1.06

1.020 Drill Rig (Combustion) 38.30 7.69 19.90 4.00 18.60 3.74 284.00 56.90 61.10 12.20 22.50 4.51

1.021 Loader (Combustion) 15.80 2.88 8.21 1.50 16.80 3.07 183.00 33.40 53.10 9.70 23.20 4.24

1.022 Clean-up Loader (Combustion) 4.18 0.76 2.18 0.40 4.46 0.81 48.50 8.86 14.10 2.57 6.16 1.12

SUBTOTAL - EMISSION UNIT GROUP 1 1,270.00 167.00 591.00 78.00 364.00 64.50 3,460.00 617.00 2,760.00 426.00 174.00 32.10

Emission Unit Group 2: Heap Leaching Activity

2.001 Portable R-O-M Lime Silo Loading 0.14 0.02 0.07 0.01 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

2.002 Portable R-O-M Lime Hopper Loading 1.00 0.12 1.00 0.12 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

2.003 Lime Application to Ore 0.12 0.01 0.06 0.01 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

2.004 Ore Ripping/Spreading/Dozing 29.70 5.42 3.68 0.67 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

2.005 Heap Leach Dozer (Combustion) 6.34 1.16 3.30 0.60 13.40 2.44 123.00 22.40 52.90 9.65 5.83 1.06

2.006 Cyanide Application and Leaching 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

2.007 Pregnant Solution Pond 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

2.008 Barren Solution Pond 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

2.009 Wind Erosion (Heap) - Non-Leach 8.23 1.47 4.12 0.74 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

2.010 Wind Erosion (Heap) - Leach 0.41 0.07 0.21 0.04 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

SUBTOTAL - EMISSION UNIT GROUP 2 46.00 8.27 12.40 2.18 13.40 2.44 123.00 22.40 52.90 9.65 5.83 1.06

Emission Unit Group 3: Process Plant

3.001 Carbon Adsorption Tank 1 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

3.002 Carbon Adsorption Tank 2 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

3.003 Carbon Adsorption Tank 3 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

3.004 Carbon Adsorption Tank 4 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

3.005 Carbon Adsorption Tank 5 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

3.006 Acid Wash Tank 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

3.007 Cyanide Make-up Tank 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

3.008 Strip Tank 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

3.009 Electrowinning Cell 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

SUBTOTAL - EMISSION UNIT GROUP 3 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

Emission Unit Group 4: Refining

4.001 Mercury Retort Furnace (Electric) 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

SUBTOTAL - EMISSION UNIT GROUP 4 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

Emission Unit Group 5: Laboratory

5.001 Jaw Crusher 1.02 0.19 0.07 0.01 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

5.002 Pulverizer 1.02 0.19 0.07 0.01 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

5.003 Fume Hood 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

5.004 Waste Acid Tank 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

SUBTOTAL - EMISSION UNIT GROUP 5 2.04 0.37 0.15 0.03 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

Emission Unit Group 6: Shop Area

6.001 Main Diesel Tank 1 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.19 0.04

6.002 Street Diesel Tank 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.01 0.00

6.003 Unleaded Gasoline Tank 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 3.26 0.60

6.004 Coolant Tank 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

SUBTOTAL - EMISSION UNIT GROUP 6 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 3.46 0.63

Emission Unit Group 7: Mine & Process Area Support Activities

7.001 Water Truck (Combustion) 6.72 1.23 3.50 0.64 11.90 2.16 109.00 19.80 46.90 8.56 5.17 0.94

7.002 Water Truck Traffic 0.23 0.04 0.10 0.02 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

7.003 Backup Diesel Generator 0.00 0.01 0.00 0.01 0.00 0.01 0.00 0.38 0.00 0.10 0.00 0.01

7.004 Mobile Light Plant - Pit #1 1.02 0.19 0.48 0.09 0.45 0.08 6.82 1.24 1.47 0.27 0.55 0.10

7.005 Mobile Light Plant - Pit #2 1.02 0.19 0.48 0.09 0.45 0.08 6.82 1.24 1.47 0.27 0.55 0.10

7.006 Mobile Light Plant - Heap 1.02 0.19 0.48 0.09 0.45 0.08 6.82 1.24 1.47 0.27 0.55 0.10

7.007 Mobile Light Plant - WRS 1.02 0.19 0.48 0.09 0.45 0.08 6.82 1.24 1.47 0.27 0.55 0.10

7.008 Cable Reel Machine 2.67 0.49 1.36 0.25 15.50 2.83 96.70 17.60 142.00 25.90 16.70 3.04

7.009 Grading of Road Surface 1.40 0.26 4.11 0.75 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

7.010 Grader (Combustion) 4.08 0.74 2.12 0.39 5.73 1.05 46.60 8.51 10.00 1.83 2.34 0.43

SUBTOTAL - EMISSION UNIT GROUP 7 19.20 3.50 13.10 2.40 34.90 6.37 279.00 51.30 204.00 37.40 26.40 4.83

Emission Unit Group 8: Other Mobile Emission Units

8.001 On-Site Delivery Truck Traffic 0.38 0.07 0.17 0.03 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

8.002 On-Site Delivery Truck (Combustion) 0.00 0.00 0.00 0.00 0.00 0.00 0.01 0.00 0.03 0.01 0.00 0.00

8.003 On-Site Light Vehicle Traffic 3.77 0.67 1.70 0.30 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

8.004 On-Site Light Vehicle (Combustion) 0.20 0.04 0.10 0.02 0.05 0.01 0.49 0.09 1.65 0.30 0.20 0.04

8.005 Off-Site Delivery Truck Traffic 19.50 3.48 8.77 1.57 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

8.006 Off-Site Light Vehicle Traffic 274.00 49.00 124.00 22.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

SUBTOTAL - EMISSION UNIT GROUP 8 298.00 53.30 134.00 24.00 1.68 0.31 0.06 0.01 0.50 0.09 0.20 0.04

TOTAL - ALL EMISSION GROUPS 1,640.00 233.00 751.00 107.00 413.00 73.30 3,860.00 691.00 3,020.00 473.31 209.00 38.60

The largest proportion of the emission units are the fugitive emission sources, especially emitters of fugitive particulate matter (TSP and PM₁₀). Mining and heap leaching activities, such as blasting, loading, dumping and dozing, release fugitive particulate matter into the air through the physical movement of the ore or waste rock. Ore and waste rock hauling, and truck and vehicle traffic, all generate fugitive particulate matter emissions by traveling on unpaved roads. Finally, wind erosion of both the waste rock stockpiles and ore heap can generate fugitive particulate matter emissions.

Mobile sources, the next largest category of sources, are principally associated with the mining and heap leaching process. They consist almost exclusively of large diesel engines which power the haul trucks, dozers, graders, and water trucks. Because of the high percentages of use (many would operate nearly 24 hours per day), these mobile sources would produce substantial quantities of "tailpipe" combustion emissions, such as NO_x, SO_x, and CO.

Most of the mobile sources fall into the category of "non-road engines," generally defined under 40 CFR '89 as internal combustion engines which are in or propel a vehicle which is not a "road" vehicle, or are portable or transportable, but which do not remain in a fixed location for more than a year. These federal regulations require that "non-road" engines must be manufactured to meet specific emission standards for criteria pollutants, based on the size (hp rating) of the engine and date of manufacture, according to a specific timetable commencing on January 1, 1996. Table 4.6 lists the identified Project "non-road" engines, the size (kW rating) of each, whether the engine would be purchased (in 1998) "new" or "used," and whether the engine would be subject to these new federal emission limitations.

Table 4.6

Engine

Engine Rating

Year of Manufacture

Applicability of 40 CFR 89

Haul Trucks (8) 2,500 hp 1998 No

Dozers (2) 375 hp 1998 Yes

Drill Rigs (2) 550 hp 1998 Yes

Loader (1) 1,250 hp 1998 No

Light Plants (4) 35 hp 1998 No

Cable Reel Machine (1) 350 hp <1996 No

Clean-up Loader (1) 690 hp <1996 No

Water Trucks (2) 1,050 hp <1996 No

Grader (1) 275 hp 1998 Yes

Back-Up Generator (1) 750 hp 1998 Yes

Based on the Project engine size ratings and their assumed date of manufacture (based on the purchase date), less than half of the Project "non-road" engines would be required to be manufactured to met the new federal emission standards. However, many engine manufacturers are already meeting or exceeding the new emission standards.

Although the Project has a number of stationary point sources, these sources are individually and collectively minor sources of criteria air pollutant emissions. About one-half (2) of the stationary point sources are combustion sources, which as a class emit substantially more gaseous combustion pollutants (NO_x, SO_x, and CO) than particulate matter.

Finally, the "other" category of criteria pollutant emission sources consist exclusively of the diesel, gasoline and other volatile organic compound storage and dispensing tanks. However, the total quantities of these materials emitted by the Project to the atmosphere are small.

Federal PSD Regulations:

Federal Prevention of Significant Deterioration (PSD) regulations are applicable only to major stationary sources which are either specific types of facilities which emit, or have the potential to emit, 100 tons per year or more of a criteria pollutant, or any facility which emits, or has the potential to emit, 250 tons per year or more of any criteria pollutant. Most fugitive emissions, however, are not included as applicable emissions under the federal PSD program. Since the few stationary emission units under the Proposed Action emit collectively substantially less than 1 ton per year of any criteria pollutant, the Project is not subject to federal PSD regulations.

Title V of the CAAA:

The CAAA included Title V, which established a very detailed and extensive operating permit system for "major sources" of regulated air pollutants. The ICAPCD has adopted Rule 900 to implement Title V within the District, and USEPA's delegation of authority to implement Title V through Rule 900 became effective on June 2, 1995. Rule 900 is applicable only to a "major" source of air pollutants, which is defined as "a stationary source which has the potential to emit a regulated air pollutant or a hazardous air pollutant (HAP) in quantities equal to or exceeding the lesser of any of the following thresholds:"

"100 tons per year (tpy) of any regulated air pollutant;"

"10 tpy of one HAP or 25 tpy of two or more HAP's; or"

"Any lesser quantity threshold promulgated by the U.S. EPA."

At present, no lower quantity threshold has been set by the USEPA.

To determine the applicability of Title V (Rule 900) to the Project, an inventory of the annual potential to emit for each of the applicable emission units was conducted for the Proposed Action (see Appendix O). Since Title V (Rule 900) specifically excludes "fugitive" and "mobile" (road and non-road engine) sources of regulated air pollutants, it is basically applicable only to stationary ("point" and "other") sources of criteria (regulated) air pollutants (and certain HAPs). As such, few of the Project's emission units are included in the Title V applicability for criteria pollutants. The largest applicable annual emission rate for a single criteria pollutant for the Proposed Action is 0.64 tons per year of volatile organic compounds/reactive organic gases (VOCs /ROGs); all of this emitted from the fuel and other organic liquid storage and dispensing facilities.

HAPs are specifically listed hazardous air pollutants, some of which can be found in many of the natural earth materials which would be mined by the Project; in the fuels used and stored by the Project; and in the solution used to leach the precious metals from the ore. Current USEPA and ICAPCD guidance provides that reasonably quantifiable HAP emissions from fugitive sources, as well as from stationary sources, must be counted to determine the applicability of Title V for HAPs. The potential HAPs component of the emitted Project particulates has been conservatively estimated by assuming that all of the HAPs contained in the fugitive particulate matter are subject to Title V (Rule 900). Based upon analyses of ore and waste rock samples collected during exploration drilling (see Section 2.1.4), and using the calculated total annual TSP emission estimates (see Table 4.5), the total annual emission of particulate-based HAPs has been estimated at less than 0.01 tons (see Appendix O).

HAPs released as a result of the combustion of diesel fuel and gasoline in mobile engines are not subject to Title V (Rule 900). In addition, the HAPs released from most uses of the leaching solution (principally HCN) are not subject to Rule 900 because they cannot be reasonably quantified. Due to its limited use, combustion HAPs from the diesel-fueled emergency generator total less than one (1) pound (0.0002 ton) per year. The total annual emission of all potentially applicable HAPs from the Project, including reasonably quantifiable fugitive HCN emissions, is approximately 0.5 tons, substantially below both the 25 ton project-wide Title V threshold and the 10 ton individual HAP Title V threshold (see Appendix O).

New Source Review and Emission Offsets:

Rule 207 of the ICAPCD regulations requires the preconstruction review of new or modified stationary sources to ensure that a project would not interfere with the attainment or maintenance of ambient air quality standards. This rule also states that no net increase in emissions to the air basin would be allowed from new permitted stationary sources with the potential to emit 137 pounds per day (equivalent to 25 tons per year) or more of any nonattainment pollutant or its precursors. Rule 207 also requires that emissions in excess of the 137 pound per day threshold be "offset" with an actual reductions of the same pollutant or its precursors. These offsets can be obtained from another source at the same location, and offset at a ratio of 1:1; or from another source up to 50 miles away at a ratio of 1.2:1. Based upon the emission estimates for permitted stationary sources as presented in Appendix O, which are maximum, not anticipated, emission levels, the Proposed Action would not emit more than 25 tons per year of any nonattainment pollutant or its precursors, and would be in compliance with Rule 207.

Conformity to the State Implementation Plan

Section 176 of the Clean Air Act (CAA), as amended (42 USC 7401 et seq.), and regulations under 40 CFR Part 51, Subpart W, apply to projects within non-attainment areas with respect to the conformity of general federal actions to the applicable State implementation plan (SIP). Under those authorities, "no department, agency or instrumentality of the Federal Government shall engage in, support in any way or provide financial assistance for, license or permit, or approve any activity which does not conform to an applicable implementation plan." Under CAA 176© and 40 CFR Part 51, Subpart W, a federal agency must make a determination that a federal action conforms to the applicable SIP before the action is taken. The emission reduction measures contained in the Proposed Action conform to the requirements of the SIP.

As required by the CAA and the CAAA, the ICAPCD in 1992 issued its final air quality attainment plan (AQAP) outlining how the basin would conform to the requirements of the state implementation plan (SIP). The ICAPCD AQAP requires emission offsets of nonattainment air pollutants to produce net emission reductions within the basin. This is implemented by ICAPCD Rule 207, which requires that emissions of nonattainment air pollutants in excess of 137 pounds per day (25 tons per year) from stationary sources be "offset" with actual net reductions of the same air pollutant or its precursors in excess of the emissions from the project. Based upon the analysis of compliance with Rule 207 presented above, the Proposed Action would not emit more than 25 tons per year of any nonattainment pollutant or its precursors covered by Rule 207, and thus would be in compliance with Rule 207 and conform to the State Implementation Plan.

Best Available Control Technology/Reasonably Achievable Control Measures:

Rule 207 of the ICAPCD regulations also requires the application of Best Available Control Technology (BACT) to any new (stationary) emission unit which has the potential to emit 25 pounds per day (approximately 4.5 tons per year) of any nonattainment pollutant or its precursors. The Project contains no applicable emission unit which produces more than 1 ton per year, and thus is not subject to BACT requirements.

ICAPCD Regulation VIII (Fugitive Dust Requirements for Control of Fine Particulate Matter) requires the implementation of Reasonably Available Control Measures (RACM) to reduce the amount of PM₁₀ entrained in the ambient air as a result of emissions generated from anthropogenic (man-made) fugitive dust sources generated from within Imperial County. RACM must be applied to any active operation, except as specifically exempted in the regulations. Because the silt content of both the Project ore and waste rock is less than five (5) percent, and most other Project activities which would generate fugitive PM₁₀ are specifically exempted from Regulation VIII, only the use of internal roads for traffic and hauling; the discharge of the lime to the ore trucks; and the soil stockpiles are subject to RACM for PM₁₀. For each of these activities, the Proposed Action already contains one (1) or more of those measures required as RACM: the haul and maintenance roads are watered at least once per day; the lime discharge to the ore trucks is controlled by water sprays; and emissions from the soil stockpiles are controlled through the application of vegetation. Therefore, there is no regulatory requirement for the implementation of any additional measures to reduce emissions of fugitive PM₁₀.

California Air Toxics "Hot Spots" Information and Assessment Act (AB2588):

The Air Toxics "Hot Spots" Information and Assessment Act (AB2588) ("Hot Spots" Act) was enacted in September 1987, and subsequently amended in 1992 and again in 1997. The goal of the "Hot Spots" Act is to collect emission data indicative of routine, predictable releases of toxic substances to the air; to identify facilities having localized impacts from these releases; to evaluate health risks from exposure to these emissions; to notify nearby residents of significant risks; and reduce risk below the determined level of significance.

The "Hot Spots" Act requires CARB to compile and maintain a list of substances posing chronic or acute health threats when present in the air. The Air Toxics "Hot Spots" Act currently identifies by reference over 600 substances which are required to be subject to the program, a portion of which must be quantified. Under Section 4432 of the California Health & Safety Code, AB2588 applies to the following:

A(a) Any facility which manufactures, formulates, uses, or releases any of the substances listed pursuant to Section 44321 or any other substance which reacts to form a substance listed in Section 44321 and which releases or has the potential to release total organic gases, particulates, or oxides of nitrogen or sulfur in the amounts specified in Section 44322.

"(b) Except as provided in Section 44323, any facility which is listed in any current toxics use or toxics air emission survey, inventory, or report released or compiled by a district. A district may, with the concurrence of the state board, waive the application of this part pursuant to this subdivision for any facility which the district determines will not release any substance listed pursuant to Section 44321 due to a shutdown or a process change."

Of the 600 substances listed under the "Hot Spots" Act, a large portion of them are also listed as HAPs under Title V of the federal CAA. Of those listed as "Substances Which Must Be Quantified" under AB2588, the Proposed Action is not expected to emit any substances which were not already identified as a HAP under Title V of the Clean Air Act. The Proposed Action would use several chemicals listed as "Substances For Which Production, Use, or Other Presence Must be Reported." Given the use and presence of these chemicals, Glamis Imperial would be expected to prepare and submit to the ICAPCD an AB2588 Emission Inventory Plan (EIP) as specified in California Health & Safety Code Sections 44300 et seq. This plan must meet the requirements of the Emission Inventory Criteria and Guidelines Regulation, California Code of Regulations Subchapter 7.6, Sections 93300 through 93347, and outline "a comprehensive characterization of the full range of hazardous materials that are released, or that may be released, to the surrounding air from the facility." Once the EIP is approved by the ICAPCD, a complete Emission Inventory would be prepared in accordance with the requirements of AB2588. Given the limited quantities of applicable emissions as discussed above, and the remote location of the Project, exposure of sensitive populations to significant concentrations of air toxics from the Proposed Action is very unlikely. Any impacts would be below the level of significance.

Compliance with Ambient Air Quality Standards:

The principal pollutant of concern emitted by the Project is PM₁₀ because of the relatively large quantity of PM₁₀ emitted by the Project, the relatively low ambient air quality standard for PM₁₀, and the fact that nearly all of the Project PM₁₀ emissions are from fugitive and mobile sources which are emitted throughout the Project mine and process area. (The newly adopted PM_2.5 standard is not yet applicable and, because of the lack of baseline ambient measurements, determinations of attainment for any area cannot yet be made. In addition, the techniques necessary to estimate a project's PM_2.5 emissions have not yet been fully developed, and thus an evaluation of a project's potential impacts and compliance with the new standard cannot be made.)

In order to estimate the ambient air concentrations of PM₁₀ which may result from Project emissions, computer-aided dispersion modeling for the Project PM₁₀ emissions was conducted (see Appendix O). The modeling was conducted with the USEPA Industrial Source Complex - Short Term (ISCST3R) dispersion model, which utilized the Trinity Consultants, Inc. Breeze "graphical front end" (IBM-PC Version 3.00, dated 96113). Using USEPA's regulatory default model options and rural dispersion parameters with elevated terrain, emissions from Project were modeled based on hourly emission rates calculated in Appendix O and summarized in Table 4.5 for all sources (fugitive, point, mobile and other) of PM₁₀ within the Project mine and process area. Surface meteorological data for the year 1989 from the National Weather Surface (NWS)-operated Yuma Air Station, combined with upper-air data from the NWS-operated Tucson Upper Air Station, was used, as it provided the most readily and reasonably available meteorological data set for the modeling.

One (1) set of discrete receptors and four (4) Cartesian receptor grids were used for the modeling the emissions from the Proposed Action. Two (2) coarse Cartesian receptor screening grids were used: a 24 x 21, 1,000-meter receptor grid, centered on the Project mine and process area, which extended out over five (5) miles from the Project mine and process area boundary (and included the wilderness areas located in the vicinity of the Project mine and process area); and a 21 x 21, 250-meter receptor grid, also centered on the Project mine and process area, which extended out over one-half (0.5) mile from the Project mine and process area boundary. The single discrete receptor set consisted to two (2) groups: a set of receptors placed at approximate 50-meter intervals along the fenced Project mine and process area boundary; and individual receptor points located in areas of potential public concern outside of those areas modeled under the Cartesian receptor grids (these receptor points, and their respective locations, are listed in Table 4.7). In addition, two (2) densely spaced Cartesian receptor grids were modeled in those areas on the Project mine and process area boundary near pollutant "highs" identified by the coarser modeling.

Table 4.7

Receptor Point
Location (UTM)

Northing Easting

Bard, California 3630500 729000

Fort Yuma Reservation Boundary - Wash 3635200 720000

Fort Yuma Reservation Boundary - NW Corner 3634850 711750

Picacho State Recreation Area 3656000 723000

American Girl Mine 3637300 707200

Glamis, California 3652500 680000

Gold Rock Ranch 3640000 700000

Picacho Mine 3649500 720200

Mesquite Regional Landfill 3655943 685581

Mesquite Mine 3658556 688788

Modeling was conducted for each of the four (4) modelable criteria pollutants (PM₁₀, NO_x, SO₂, and CO) emitted by the Project using the applicable regulatory averaging times for each pollutant. A complete discussion of the modeling conducted, including the parameters used in the model runs and a discussion of the meteorological data, is contained in Appendix O to this EIS/EIR.

The computer-calculated maximum ambient 24-hour PM₁₀ concentration located at any point on or outside of the Project mine and process area perimeter fence was 30.73 Fg/m³, located on the perimeter fence near the northwest corner of the Project mine and process area. Calculated maximum annual PM₁₀ concentrations were 5.7 Fg/m³, also located on the perimeter fence at a point near the northwest corner of the Project mine and process area. Both of these values are below the applicable CAAQS and NAAQS (see Table 3.7), although close to the CAAQS when the background (annual) PM₁₀ concentration (either 19.0 Fg/m³ (arithmetic mean) or 17.5Fg/m³ (geometric mean)) calculated from the nearest monitored location, Gold Rock Ranch, is added. Calculated Project-generated ambient concentrations at distances greater than 3,750 meters (2.3 miles) from the Project mine and process area boundary were universally below 5 Fg/m³. Maximum ambient concentrations at receptor points on the northern boundary of the Ft. Yuma Indian Reservation, a distance of 12,000 meters (7.5 miles) from the southern boundary of the Project mine and process area, were well below 1.0 Fg/m³ (both 24-hr and annual concentrations) and would be impossible to distinguish from background ambient concentrations. Impacts from the Project at the other discrete receptors placed at points of potential public concern were universally modeled at below 2 Fg/m³, and would likewise be impossible to distinguish from background concentrations. These impacts would be below the level of significance. However, monitoring is proposed to be required to verify that the project does not exceed the ambient air quality standards.

One-hour and annual average concentrations were modeled from the Project's estimated emissions of NO_X. However, as indicated in Table 3.7, both the CAAQS and NAAQS are for concentrations of the NO₂ portion of NO_X. In order to reasonably predict the Project's compliance with the CAAQS and NAAQSs for NO₂, the NO₂fraction of ambient NO_X was estimated utilizing the USEPA's "Ozone Limiting Method." Using this method, the highest estimated 1-hr concentration of NO₂ from the Project at any point on or outside of the perimeter fence was 0.24 ppmv, less than the CAAQS of 0.25 ppmv (250 ppbv). The highest annual average ambient NO₂ concentration resulting from the Proposed Action was 0.0116 ppmv, much less than the NAAQS of 0.053 ppmv (53 ppbv), this at a point well within the fenced boundary of the Project mine and process area. Ambient concentrations modeled at the other discrete receptors placed at points of potential public concern were universally at or below 0.01 ppmv (10 ppbv). These impacts would be below the level of significance. A complete discussion of the "Ozone Limiting Method," as well as the results of the NO_X modeling conducted, is included in Appendix O.

The highest modeled 1-hour SO₂ concentration, at a point near the center of the Project mine and process area, was 494 µg/m³, well below the CAAQS of 655 µg/m³. All modeled concentrations at points accessible to the public, at or beyond the boundary of the Project mine and process area, were universally less than 150 µg/m³. The modeled 3-hour high, at a point near the center of the Project mine and process area, was 264 µg/m³, well below the secondary NAAQS of 1,300 µg/m³. All modeled SO₂ concentrations at points accessible to the public were universally below 100 µg/m³, well below the secondary NAAQS. The modeled 24-hour SO₂ high, at a point near the center of the Project mine and process area, was 61 µg/m³, below both the CAAQS and NAAQS. Calculated 24-hour SO₂ ambient concentrations at distances greater than 3,750 meters (2.3 miles) from the Project mine and process area boundary were universally below 10 µg/m³. The highest modeled annual average, at a point again near the center of the Project mine and process area, was less than 22 µg/m³, well below the annual NAAQS. These impacts would be below the level of significance. A complete discussion of the modeling conducted for SO₂ emissions from the Project is contained in Appendix O.

The results of the CO model indicate a maximum 1-hour high, at a point near the center of the Project mine and process area, of 2,501 µg/m³, well below both the 24-hour NAAQS and CAAQS . In addition, all calculated 1-hour ambient concentrations beyond the Project mine and process area boundary were universally below 1,500 µg/m³. The results of the 8-hr average model shows a maximum modeled high, at a point again near the center of the Project mine and process area, of 993 µg/m³, well below both the annual NAAQS and CAAQS for CO. All modeled concentrations at points accessible to the public, beyond the Project mine and process area boundary, were universally below 500 µg/m³, well below both the annual NAAQS and CAAQS for CO. These impacts would be below the level of significance. A complete discussion of the modeling conducted for CO emissions from the Project is contained in Appendix O.

Deposition and Depletion of Suspended Particulate Matter

Deposition of lofted particulate matter from Project operations is expected to occur on and around the Project area. The rate at which particulate matter settles out from the atmosphere is a function of its gravitational settling velocity. Larger particles (those greater than 30 microns in diameter) have sufficient mass to overcome turbulent eddies, and as such settle out much more quickly than smaller particles. In order to evaluate the quantity of material potentially deposited on nearby surface and flora in the area, the emissions of total suspended particulates were modeled using the ISCST3 model. The EPA model has algorithms which simulates the effects of dry and wet deposition of particulates on the surface due to the processes of gravitational settling and turbulent diffusion. The depositional velocity is a function of the meteorology and surface conditions near the source, but is independent of the distance from the source.

In modeling the deposition of particulate matter, model settings identical to those used for the criteria pollutant modeling were used: EPA's regulatory default model options, rural dispersion parameters, elevated terrain, etc. In addition, the dry deposition option was enabled. Also, consistent with earlier runs, the Yuma/Tucson meteorological data set was used. A radial receptor grid, consisting of eight (8) radii with 30 rings spaced at 100-meter intervals, roughly centered on the Project mine and process area, and extending approximately 2.0 kilometers beyond the Project mine and process area boundary, was used. Given the high gravitational settling velocity of particulate matter greater than 30 microns, only suspendable particulate matter (those less than 30 microns in diameter, or TSP) were modeled using the same model source parameters as were used in the modeling performed for impacts from PM₁₀, and using calculated annual average emissions of TSP. In addition, the model conservatively assumed that no wet deposition occurred, that no depletion or removal of mass from the plume occurred, and that deposited particulate matter was not re-suspended as a result of additional turbulence or eddies.

The modeled annual average deposition values calculated at all points beyond the Project mine and process area boundary were less that six (6.0) grams per square meter (g/m²). At all points greater than 0.5 kilometers from the Project mine and process area boundary, the annual average deposition was less than 2.0 g/m². The highest amount of deposition (24.1 g/m²) occurred at a receptor point located near the center of the Project mine and process area, and the amount of deposited material decreased rapidly as the distance from the source increased. A complete discussion of the deposition modeling conducted for the Project is contained in Appendix O. These impacts are not considered significant in regards to their air quality impacts (see above); the effects on vegetation are discussed in Section 4.1.5.2.

Exposure of Sensitive Populations:

Project air pollutant emissions would produce modest increases in the annual average ambient concentrations of both criteria air pollutants and HAPs in the immediate vicinity of the Project mine and process area, well below any applicable threshold for exposure of sensitive populations. In addition, the Project mine and process area is far removed from any resident population, sensitive or otherwise, which could be exposed to any significant, long-term increase in the ambient concentrations of either criteria air pollutants or HAPs. Transient populations (i.e., recreational visitors) could be temporarily exposed to slightly higher level concentrations, although again these ambient air concentrations would be well below any appropriate threshold exposure level.

Other Air Quality Related Health Concerns:

Coccidioidomycosis ("valley fever" or "desert fever") is caused by an infection from the fungus Coccidiodes immitis. Spores of this fungus are endemic in the uppermost few inches of the soil of those areas where the disease occurs (CDHS No Date). Spores are carried into the air on dust, particularly during dust storms, and infection is caused by inhalation of dust carrying the spores. The California Department of Health Services (CDHS) indicates that:

"Nearly everyone living for many years in areas where coccidioidomycosis occurs becomes exposed to and infected by the fungus that causes the disease... most people never get sick, and ... only two out of every 1,000 individuals infected develop severe illness.... Even the mildest >attack= of coccidioidomycosis confers lifelong immunity." (CDHS No Date)

Although much of Arizona (including Yuma), portions of San Diego County, and northern Mexico have been established as endemic areas for the disease, Imperial Valley has not been designated as an endemic area for coccidioidomycosis. The Imperial County Department of Health Services, Division of Environmental Health (ICDHS-DEH) has indicated that there are no recorded cases of valley fever in Imperial County (Personal Communication, Thomas Wolf, ICDHS-DEH, May 5, 1997).

Assuming that the area of the Proposed Action is endemic for the disease, only the top few inches of soil would be expected to contain the spores (Personal Communication, Dr. C. Talbert, Kern County Health Department, June 6, 1997). This layer of soil would be removed or buried during the first days of construction activity in any particular area, so that any exposure to dust-containing spores would be limited to those times when construction in new areas was initiated. Although this is not expected to result in a significant effect, a mitigation measure is proposed to reduce the effect further.

4.1.4.3. Measures Incorporated by Project Design and Regulation and Mitigation Measures

4.1.4-1: Chemical dust suppressant treatments, in combination with water sprays, shall be applied to the haul and maintenance roads within the Project mine and process area to minimize the generation of fugitive PM₁₀. Only chemical dust suppressants acceptable to all appropriate agencies shall be applied, and the application rates and frequencies, for both the dust suppressant and water, shall be consistent with the guidance of the manufacturer to achieve optimal suppression of dust. Dust suppressant and/or water shall be applied no less than twice per day on days without precipitation unless road surface moisture is documented as sufficient to achieve maximum suppression of fugitive dust emissions without the additional dust suppressant or water.
4.1.4-2: Project employees, contractors, and visitors shall be advised of the need to adhere to speed limits to minimize the generation of fugitive dust. Applicant shall develop and implement appropriate measures to strengthen compliance with posted speed limits to prevent the generation of fugitive dust.
4.1.4-3: Shrouding of the lime discharge to the ore trucks, or equivalent RACM for these fugitive PM₁₀ emissions, shall be implemented and maintained.
4.1.4-4: Water sprays or dust suppressants (chemical treatments acceptable to all appropriate agencies) shall be applied to Indian Pass Road from its intersection with Ogilby Road to the boundary of the Project mine and process area with sufficient frequency to minimize the emissions of fugitive PM₁₀ from Project traffic on Indian Pass Road.
4.1.4-5: All disturbed surfaces no longer needed for project activities shall be reclaimed as soon as practical to minimize fugitive PM₁₀ emissions from wind erosion.

Measures Incorporated by Regulation Which Avoid or Reduce Potentially Significant Impacts:

4.1.4-6: All permits required by the ICAPCD shall be obtained, and all operations conducted in compliance with the conditions of these permits.
4.1.4-7: All fuels used at the Project shall conform to the CARB low-sulfur requirements in order to minimize SOx emissions from Project-related vehicular activities.

Mitigation Measures Proposed to Avoid or Reduce Potentially Significant Impacts:

No mitigation measures are proposed or recommended.

Other Mitigation Measures (These are measures which may further reduce the impacts of certain effects which are below the level of significance without mitigation):

4.1.4-8: Appropriate measures, such as water sprays, dust suppressants (chemical treatments acceptable to all appropriate agencies), or reduced operating speeds, shall be applied to all activities which disturb the top foot of soil in any areas during construction and reclamation activities to minimize emissions of fugitive PM₁₀ which may contain Coccidiodes immitis spores. Project employees, contractors, and visitors shall be advised to use appropriate precautions regarding the inhalation of dust while in the Project area during the initial construction/reclamation phases to minimize exposure to Coccidiodes immitis spores.
4.1.4-9: Applicant shall, in consultation with the ICAPCD, establish and maintain one (1) meteorological monitoring station (for wind speed and wind direction) and two (2) PM₁₀ monitoring stations (6-day high volume samplers) to monitor project the ambient concentrations of PM₁₀ which may be generated by Project activities. It shall be the intent of the two (2) PM₁₀ monitors to be located in generally an upwind and downwind arrangement and operated simultaneously to provide information on the Project's effects on ambient PM₁₀ concentrations. Should the monitoring show that Project operations may be contributing to a significant increase in ambient PM₁₀ concentrations, then the Applicant shall review its procedures for reducing PM₁₀ emissions and recommend to the ICAPCD methods which could be applied to reduce these emissions sufficiently to eliminate the significant increase.

4.1.4.4. Unavoidable Adverse Effects and Level of Significance After Mitigation

Project emissions of criteria air pollutants and HAPs would produce increases in the ambient concentrations of both these air pollutants in the immediate vicinity of the Project mine and process area during the life of the Proposed Action. Application of the measures proposed as part of the Proposed Action would prevent impacts to air resources from reaching or exceeding the level of significance.

4.1.5. Biological Resources

This assessment of the effects of the Project on biological resources is based on the findings described in several biological technical investigation reports of the area of the Proposed Action which are appended to this EIS/EIR as Appendices F, G, H, I, J, and K. A summary of the findings of the biological surveys is provided in Section 3.5.6.2. In addition, the findings of the Biological Assessment of the anticipated effects of the Project on the federal and state listed and proposed biological resources in the Project area, prepared on behalf of the BLM (Rado 1997) and submitted to the USFWS, have been summarized in this assessment, and the recommended mitigation measures provided in the Biological Assessment have been integrated into measures provided in this EIS/EIR.

4.1.5.1. Assumptions and Assessment Guidelines

The assessment of impacts assumes the implementation of those measures incorporated into the project design or required by regulation which avoid or reduce potentially significant impacts.

To determine the potential significance of the effects of the Proposed Action on biological resources, it is necessary to consider the relative importance of the identified biological resources in the vicinity of the area of the Proposed Action and the degree of potential Proposed Action-related impacts on these respective resources. As discussed in the regulatory framework for biological resources section of this EIS/EIR (Section 3.5.1), factors utilized to determine the relative importance of the biological resources in the vicinity of the Proposed Action are, in part, based on species and habitats afforded protection under both the federal Endangered Species Act (ESA) and the California Endangered Species Act (CESA), as well as BLM sensitive species , and other species of concern, collectively referred to as special-interest species for the purposes of this assessment (see Section 3.5.1).

Based upon NEPA and CEQA guidelines, and commonly accepted criteria, a project would normally be considered to have a significant effect on biological resources if it could:

Substantially affect a rare or endangered species of animal or plant or the habitat of the species;
Interfere substantially with the movement of any resident or migratory fish or wildlife species; or
Substantially diminish habitat for fish, wildlife, or plants.

4.1.5.2. Impacts of the Proposed Action on Vegetation and Plant Habitat

In addition to other changes, this section has been modified from the November 1996 Draft EIR in response to comments to assess the effects of Project dust which may settle on vegetation.

The Project would impact vegetation and plant habitat primarily through direct destruction of plants by surface disturbance during construction of the mine and ancillary facilities. An estimated 1,362 acres of surface disturbance would result from the Proposed Action from the development of the mine pits, heap leach pad, waste rock stockpiles, soil stockpiles, process ponds, haul roads and access road realignment, drainage diversions, ground water well field and pipeline, electrical power lines, and other ancillary facilities. The surface locations of these facilities are identified on Figure 2.1 and Figure 2.2, and the surface acreage disturbed by these activities is listed in Table 2.2.

Surface disturbance would occur incrementally throughout the early life of the Project as individual pits are mined and waste rock stockpiles, soil stockpiles, and process facilities are expanded. Plant habitat would be lost as result of: initial surface blading of vegetation, stockpiling of soil and waste rock, and construction of surface facilities and access corridors; crushing or damage to vegetation as a result of heavy equipment use and vehicle use and parking; periodic geological survey activities; and the use of heavy equipment during reclamation activities. Vegetation existing in the areas of surface disturbance would be destroyed or damaged as a result of removal, crushing, entombment, soil compaction, or root damage.

A total 1,302 acres of surface disturbance would occur within the Project mine and process area, of which an estimated 1,215 acres of the sparse, widely-distributed shrub/scrub vegetation habitat, dominated by creosote bush, characteristic of the upland areas within the Project mine and process area, would be affected. The remaining area of surface disturbance, approximately 87 acres, would impact the shrub/tree vegetation (i.e., microphyll woodland vegetation) habitat characteristic of the primary and secondary washes within the Project mine and process area. As discussed in Section 3.5.6, approximately 2 acres microphyll woodland vegetation habitat within the Project ancillary area and approximately 1 acre of microphyll woodland vegetation habitat in the overbuilt 92 kV/34.5 kV transmission line corridor would be subject to surface disturbance.

Vegetation and plant habitat recovery is a function of the type and degree of soil disturbance. Disturbed or compacted soils associated with construction or human activity may take longer to recover than soils disturbed by natural disturbances (i.e., such as flooding), in part because seeds, and perhaps related symbionts (e.g., rhizobial bacteria), may no longer be present (Virginia and Bainbridge 1987). Revegetation strategies would be implemented to reduce the time involved for natural plant establishment on land disturbed by the Proposed Action. Examples of strategies in desert revegetation include soil preparation (scarification and topsoil restoration), reseeding, transplantation, and plant protection (see Section 2.1.11, or Appendix A, Reclamation Plan). Application of these strategies within the Project area would continue during the life of the revegetation program under the Proposed Action.

As discussed in the Reclamation Plan, the revegetation program has been developed based upon experience gained from revegetation efforts at the Picacho Mine and information provided by qualified experts on desert flora and revegetation. When the measures discussed in the Reclamation Plan are successfully implemented, the effects of surface disturbance from mine construction and operations on the vegetation and plant habitat within the area of the Proposed Action would be below the level of significance.

Project mining activities and vehicular traffic would affect vegetation and plant habitat within the immediate vicinity of the Project area by increasing the amount of airborne particulate deposition onto vegetation surfaces (see Section 4.1.4.2). Experiments currently underway in other parts of the California desert have demonstrated that the short-term effects of dusting may cause lowered primary production in desert plants due to reduced photosynthesis and decreased water-use efficiency. No long-term effects were detected in creosote bushes that were exposed to periodic acute heavy dust deposition along an unpaved road. Dusted creosote recovered its normal canopy by shedding dusted leaves and producing new shoots in response to seasonal rainfall (Personal Communication, S. Ahmann, U.S. Army National Training Center, June 6, 1997). The projected average annual particulate deposition onto vegetation outside the boundaries of the Project mine and process area would be less than 6.0 g/m² and would not exceed 4.0 g/m² in areas further than 0.5 km from the Project mine and process area boundary. Further, the potential effects on vegetation from dust would be reduced by natural occurrences of wind and infrequent precipitation which would remove some of the accumulated dust. With the implementation of the fugitive dust reduction measures contained in the Proposed Action, the effect of dust from the Proposed Action on vegetation and plant habitat would be below the level of significance.

Moisture available from watering of roads and other traffic areas for dust suppression during construction and mining activities could result in a temporary increase in some opportunistic plant species immediately adjacent to active roadways or other watered surface areas. Similarly, new low spots or drainage areas where water could pond or accumulate within the active portions of the Project mine and process area could result in the introduction of salt cedar, introduced species or other noxious weeds. Salt cedar could also invade moist pit areas following the completion of active mining activities where water may accumulate; however, these conditions are not expected to exist following the completion of mining (see Section 4.1.3.2.2). Seasonally moist areas within the remnant East Pit (or West Pit, if mining is terminated prior to the commencement of backfilling) could result in small areas (estimated at less than 1 to 2 acres of pit bottom) in which salt cedar growth might be supported (Personal Communication, Samuel A. Bamberg, Ph.D., Bamberg and Associates, April 25, 1996). The Proposed Action includes measures to actively control introduced plant species during and following active operations. The resulting impacts would be below the level of significance.

There would be a potential for impacts on vegetation and plant habitat due to the transport of hazardous chemicals to the Project area via public highways and access roads. The probability of hazardous chemical spillage occurring due to a transport accident is considered low, but the potential for occurrence cannot be entirely eliminated. The preventative and corrective measures discussed in Section 4.1.12.3 would reduce the effects of the potential risk to vegetation and plant habitat resulting from spills of hazardous chemicals being transported to the Project area to below the level of significance.

Up to 1,200 afy of ground water would be produced from the Project ground water well field for use in mining operations. The static elevation of the ground water in the alluvial production reservoir has been measured at 540 feet below ground surface (WESTEC, Inc. 1996a). The water table is far below the depth that surface vegetation could be utilizing the ground water; therefore, anticipated drawdown and lowering of the ground water elevation as a result of the proposed ground water production would not impact surface vegetation or plant habitat.

Microphyll vegetation habitat exists in the wash systems down topographic gradient of the Project mine and process area (see Figure 3.16). Concern exists that diversions of the ephemeral drainages around the mine facilities would change the flow of water through the drainages feeding this vegetation habitat in the downgradient wash systems. There is also concern that these hydrologic changes to ephemeral drainages would increase erosion or affect fluvial processes in the washes, resulting in increased sedimentation or changes in the quality of water flowing through the Project area. Construction of facilities within the Project mine and process area would also eliminate the uppermost portions of some small drainages, reducing the amount of runoff which may flow down the remaining channel and, thus, be available to the channel vegetation immediately downstream.

Under the Proposed Action, storm waters in the major ephemeral drainages would either be allowed to flow naturally through the Project area, or would be diverted into channels around the Project facilities and returned to the same natural watercourse downgradient of the Project mine and process area. Each of the diversion channels would be designed to channel the surface flow back into the same major downstream ephemeral drainages from which the flow originated (see Section 2.1.9.7). The diversion channels through the Project mine and process area would be built to approximate the original drainage system in both gradient and channel geometry to prevent erosion, and would be revegetated with microphyll vegetation to establish the same type plant habitat. Major Project facilities have been located to minimize the number and amount of small, ephemeral tributaries which may have their upper reaches eliminated. These Project design measures would minimize the effects on downstream vegetation and plant habitat from any potential changes in ephemeral stream flow and fluvial processes to below the level of significance.

4.1.5.2.1. Impacts to Threatened or Endangered Plant Species

No federal or California listed, proposed, or special status plant species were observed during the botanical surveys of the Project area or overbuilt 92 kV/34.5 kV transmission line corridor. Based on the findings of the surveys and prior database records, no listed, proposed, rare or special status plants would be affected by this Proposed Action.

4.1.5.2.2. Impacts to BLM Sensitive Plant Species and Habitat

One BLM sensitive plant species, fairy duster, was observed along the edges and banks of the smaller (2- to 8-foot wide) ephemeral drainages within the Project mine and process area and in ephemeral drainages throughout the vicinity of the Project area. Individual fairy duster plants would be destroyed and their seed bank potentially lost (i.e., the dormant seeds left by previous years= plants would be buried) as a result of the proposed grading and development activities within the Project mine and process area. Fairy duster occurs over a large geographic area, including the Colorado, eastern Mojave, and Sonoran Deserts. Based on surveys, an estimated 500+ individual plants occur within the Project mine and process area. Since most of the smaller ephemeral drainages in the Project mine and process area would be disturbed as a result of Project construction, all of this habitat, and essentially all of these fairy duster plants, would be lost. However, the species is locally common, and can and would recolonize in washes previously disturbed by mining operations (Environmental Solutions 1987). Native seeds, including fairy duster, would be collected from wash soils for use during reseeding during reclamation activities (see Section 2.1.11.1), thus replacing the communities lost during Project construction. The impact resulting from the loss of individual fairy duster plants, and fairy duster habitat, within the Project area is considered to be below the level of significance.

4.1.5.2.3. Impacts to CNPS List 4 Species and Habitat

One CNPS List 4 ("watch" list) species, the winged cryptantha, was observed within the Project area. This species was reported to exist in low numbers along the banks of the larger ephemeral drainages. Fewer than 60 individual plants were estimated to exist within the Project mine and process area (Rado 1997). These plants would be destroyed and their localized seed bank and habitat within the Project mine and process area would be potentially lost as a result of surface disturbance during mine construction. This species is widespread in distribution, ranging from the southeastern desert in California into Arizona and Nevada, but it is typically encountered in low densities and numbers of individual plants. The CNPS List 4 status indicates that these plants are not "rare" but are sufficiently uncommon that their status should be monitored. Native seeds, including the winged cryptantha, would be collected from wash soils for use during reseeding during reclamation activities (see Section 2.1.11.1), thus replacing the communities lost during Project construction. Given the current status and the distribution of the winged cryptantha, the impact from the loss of the observed plants and habitat within the Project area would be below the level of significance.

Chapter 3 continued Previous
Next Chapter 4 continued

Chapter 3 continued Previous Next Chapter 4 continued 4. ENVIRONMENTAL CONSEQUENCES AND MITIGATION MEASURES

4.1. Proposed Action

4.1.1. Geology and Mineral Resources

4.1.1.1. Assumptions and Assessment Guidelines

4.1.1.2. Impacts of the Proposed Action

4.1.1.3. Measures Incorporated by Project Design and Regulation and Mitigation Measures

4.1.1.4. Unavoidable Adverse Effects and Level of Significance After Mitigation

4.1.2. Soil Resources

4.1.2.1. Assumptions and Assessment Guidelines

4.1.2.2. Impacts of the Proposed Action

4.1.2.3. Measures Incorporated by Project Design and Regulation and Mitigation Measures

4.1.2.4. Unavoidable Adverse Effects and Level of Significance After Mitigation

4.1.3. Hydrologic Resources

4.1.3.1. Surface Waters

4.1.3.1.1. Assumptions and Assessment Guidelines

4.1.3.1.2. Impacts of the Proposed Action

4.1.3.1.3. Measures Incorporated by Project Design and Regulation and Mitigation Measures

4.1.3.1.4. Unavoidable Adverse Effects and Level of Significance After Mitigation

4.1.3.2. Ground Waters

4.1.3.2.1. Assumptions and Assessment Guidelines

4.1.3.2.2. Impacts of the Proposed Action

4.1.3.2.3. Measures Incorporated by Project Design and Regulation and Mitigation Measures

4.1.3.2.4. Unavoidable Adverse Impacts and Level of Significance After Mitigation

4.1.4. Air Resources

4.1.4.1. Assumptions and Assessment Guidelines

4.1.4.2. Impacts of the Proposed Action

4.1.4.3. Measures Incorporated by Project Design and Regulation and Mitigation Measures

4.1.4.4. Unavoidable Adverse Effects and Level of Significance After Mitigation

4.1.5. Biological Resources

4.1.5.1. Assumptions and Assessment Guidelines

4.1.5.2. Impacts of the Proposed Action on Vegetation and Plant Habitat

4.1.5.2.1. Impacts to Threatened or Endangered Plant Species

4.1.5.2.2. Impacts to BLM Sensitive Plant Species and Habitat

4.1.5.2.3. Impacts to CNPS List 4 Species and Habitat

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4. ENVIRONMENTAL CONSEQUENCES AND MITIGATION MEASURES