5.1. IntroductionAs required under NEPA and CEQA, this chapter addresses the potential for cumulatively significant effects on the environmental resources in the surrounding area which could result from the implementation of the Proposed Action and other past, present and reasonably foreseeable future projects in the general vicinity of the Project. A cumulative impact is defined under federal regulations as:
The State of California CEQA guidelines define cumulative impacts as:
The geographical area considered for the analysis of cumulative effects
may vary in size and shape to reflect each environmental resource which
is evaluated. For this cumulative impact analysis, the potentially affected
resources are located in a study area which is generally bounded by the
Colorado River to the east; the Chocolate Mountains to the northwest; the
Algodones Sand Dunes/East Mesa to the west; and the Mexican border to the
south (see Figure 5.1). 5.2. Past, Present, and Reasonably Foreseeable Activities in the Area of Cumulative AnalysisThe individual projects described below comprise the past, present, and reasonably foreseeable future projects identified by Imperial County, the BLM, El Centro Resource Area, other agencies and the public. The uses have been categorized into mining uses, commercial uses, water conservation projects, military uses, and recreational uses. All of these projects and uses have the potential to impact the environmental resources of concern within the area of the cumulative impacts analysis. The reasonably foreseeable future analysis for this EIS/EIR was evaluated for a 20-year time frame, based on the estimated potential future life of the Proposed Action. 5.2.1. Mining Uses5.2.1.1. American Girl Mine ProjectThe following description of the American Girl Mine Project was obtained from the Draft EIS/EIR which was prepared on behalf of the U.S. Bureau of Land Management by P.M. DeDyker and Associates (BLM 1994a), as updated by the cited sources. The American Girl Mine Project consisted of two (2) adjacent operating components, the Padre Madre operation and the American Girl Canyon operation (see Figure 5.1). The American Girl Canyon and Padre Madre operations were originally scheduled to cease mining operations in 1994, although operations continued into 1996. A third component, the Oro Cruz operation of the American Girl Mine Project, began operations in late 1995. Although scheduled to cease mining operations by 1999, all mining operations were terminated in 1997. Reclamation activities are currently underway at all of the American Girl Mine Project facilities, and are expected to last until mid-2001. The Padre Madre operation involved the annual mining and heap leaching of approximately 200,000 tons of ore, and the annual mining and stockpiling of approximately 400,000 tons of waste rock. Cumulative totals of 3.5 million tons of ore and 12.5 million tons of waste rock were authorized. The American Girl Canyon operation was authorized to extract 8.5 million tons of surface- and underground-mined ore, and excavate and stockpile 17 million tons of waste rock. The cumulative total surface disturbance for both of these operations was estimated to be 618 acres. As proposed, mining activities associated with the Oro Cruz operation (pits, waste dumps, haul roads, etc.) would directly disturb an estimated 191 acres. Ore processing and milling would be conducted at the existing American Girl Canyon facility. Surface mining at the Oro Cruz operation would cumulatively produce approximately 2.5 million tons of ore and 8.5 million tons of waste rock at maximum yearly rates of approximately 1.2 million tons of ore and 3.5 million tons of waste rock. During this same time underground mining would produce approximately 65,000 tons of waste rock and 500,000 tons of ore, at a maximum rate of approximately 250,000 tons of ore per year. Water required for mining, milling and heap leach processing was to be supplied from ground water produced from the American Girl well southwest of American Girl Canyon. The maximum yearly consumptive use for the Oro Cruz operation was not expected to exceed 300 acre-feet. 5.2.1.2. Mesquite MineThe Mesquite Mine and associated facilities occupy a total of approximately 5,200 acres of land east of Glamis (Environmental Solutions, Inc. 1987) (see Figure 5.1). Approximately 3,100 acres of the total project area are public lands managed by the BLM. Approximately 4,000 acres of the 5,200-acre Project area have been, or would eventually be, disturbed by the mining activities. Disturbed areas would include approximately ten (10) overburden stockpiles, which would be used to dispose of approximately 350 million tons of waste rock. These overburden piles are projected to reach heights of about 280 feet above the existing ground surface. Other disturbed areas include the four (4) open pits, the approximately 1,000 acres of lined heap leach pads, mine access roads, utility infrastructure, and other ancillary facilities (Environmental Solutions, Inc. 1987). The Mesquite Mine, which began operating in 1985, is currently operating under an Imperial County conditional use permit which was amended on January 8, 1997 to increase the authorized annual amount of mined material to 60 million tons and the amount of ore mined to 25 million tons (Personal Communication, Jesse Soriano, ICPBD, May 5, 1997). Over its life, the Mesquite Mine would extract a total of approximately 440 million tons of gold-bearing ore and barren rock from four (4) open pits by the anticipated closure within the next nine (9) to fourteen (14) years. Water consumption is expected to be approximately 1,000 afy (BLM and ICPBD 1995). Water is supplied by a system consisting of three (3) 2,500-gpm capacity water wells located approximately three (3) miles south of the mine (Environmental Solutions, Inc. 1993a). 5.2.1.3. Picacho MineThe following description of the Picacho Mine operation was obtained from personal communications with Glamis Imperial (Personal Communication, C.K. McArthur, Chemgold, 1995). Chemgold, Inc. operates the Picacho Mine, which is located in easternmost Imperial County, California, approximately eighteen (18) miles north of Yuma, Arizona (see Figure 5.1). The Picacho Mine property consists of 600 acres of fee lands and 1,650 acres of unpatented lode mining claims. The total disturbed area at the Picacho Mine amounts to approximately 330 acres. Since 1980, open-pit, run-of-mine, heap leach gold mining and processing has occurred at the Picacho Mine. Four (4) open pit deposits have been developed, with current total annual mining averaging approximately 1.5 million tons of ore and 7.0 million tons of waste. Development of an additional 3.6 million tons of ore reserves is now nearly completed, which is projected to be the final phase of mining at Picacho Mine. The completed pits and heaps are currently undergoing reclamation. Mining is expected to terminate in early 1998, with processing and reclamation activities scheduled to continue until 2001 (Personal Communication, Jesse Soriano, ICPBD, May 5, 1997). Water for mining and processing operations is supplied by pipeline to the mine from a shallow well located adjacent to, and which is assumed to produce water recharged from, the Colorado River river aquifer. Water from the Colorado River is used through a present-perfected water right to 115 afy of water held by the property and verified by contract with the USBR. The Picacho Mine uses the entire annual 115 afy allocation of water from the Colorado River river aquifer. No local ground water is used at the Picacho Mine due to the lack of a sufficient aquifer in this location. 5.2.1.4. Mineral ExplorationMineral exploration activities are ongoing to some extent at each of the mines within the cumulative impacts study area. However, these activities would not substantially impact the resources of concern because they have already been accounted for in the impacts resulting from the mine operations themselves. 5.2.2. Commercial Uses5.2.2.1. Mesquite Regional LandfillThe Mesquite Regional Landfill is a proposed new regional Class III sanitary landfill, to be located in Imperial County adjacent to the existing Mesquite Mine (BLM and ICPBD 1995) (see Section 5.2.1.2). The landfill would accommodate up to a total of 600 million tons of municipal solid waste residue and would have a life span of approximately 100 years. The municipal solid waste residue would be transported to the landfill from various Southern California communities via the existing Southern Pacific Transportation Company main line rail track and a short new railroad spur extending from the main line rail track to the landfill site. The landfill would be constructed on land recently subject to an exchange by the BLM for other land in the Santa Rosa Mountains Natural Scenic Area and near the Chuckwalla Bench ACEC. The landfill property covers approximately 4,245 acres, although the actual landfill footprint is expected to occupy approximately 2,290 acres. Approximately 588 acres of the landfill site has been extensively disturbed by previous on-site activities, and vegetation over an area of approximately 3,657 acres would be disturbed. The proposed landfill anticipates the use of water supplied from the existing Mesquite Mine ground water well field, located approximately three (3) miles south of the landfill site. The three (3) wells each have estimated maximum yields of 2,500 gallons per minute (gpm). The average annual water usage associated with the landfill operations is expected to be less than 1,000 acre-feet per year. 5.2.2.2. Gold Rock RanchThe following description of the Gold Rock Ranch was provided by the BLM (Personal Communication, A. Schoeck, BLM, 1997) and ICPBD (Personal Communication, John L. Morrison, ICPBD, October 10, 1997). Gold Rock Ranch is a privately-owned area that, until recently, was owned by a single family. Gold Rock Ranch is located approximately seven (7) miles southwest of the Project mine and process area. Gold Rock Ranch is a mobile home/RV park which operates under a permit from Imperial County. This permit authorizes the accommodation of 21 mobile homes and 14 RV's. Water, sewer, and electrical hookups are provided. A small country store is also located on the site. Primary usage is during the winter months. An on-site well is used to supply domestic water for Gold Rock Ranch. Current average usage is estimated at 5,000 gpd (less than 6 afy), with an estimated historic maximum usage rate of 12,000 gpd (less than 14 afy), as estimated by the former owner (BLM 1994a). Surface disturbance associated with Gold Rock Ranch is estimated at 20 acres. 5.2.2.3. Agricultural ProjectsCitrus Heights Ranches received a Conditional Use Permit (CUP) from Imperial County which allows for the reactivation and operation of three (3) water wells on approximately 475 acres of land in Section 8, Township 16, Range 21 East, SBB&M. The site is located approximately two (2) miles east of the intersection of Ogilby Road and Interstate Highway 8 (ICPC 1995). Citrus Height's Conditional Use Permit was amended on April 9, 1997 to allow the pumping of up to 2,800 acre-feet of ground water per year for agricultural purposes. The existing site is fallow farm land which was previously used to grow jojoba. Other than the improvements to the three (3) wells, the only other new improvements would be for the installation of irrigation systems (Imperial County Planning Department 1997). 5.2.3. Water Conservation Projects5.2.3.1. All American Canal Lining ProjectThe following description of the All American Canal Lining Project was obtained from Imperial Irrigation District's Notice of Determination filed with the County Clerk of Imperial County. The Imperial Irrigation District proposes to build a parallel concrete canal along the All American Canal from 1.6 miles west of Rock Section 2 (one (1) mile west of Pilot Knob) to Drop 3 (a total of 23 miles) to conserve water lost by seepage. The project would conserve approximately 67,700 acre-feet per year. The project was authorized by Congress in Title II of Public Law 100-675. Construction of the project would result in the emissions of PM10, although dust from excavation and grading operations would be localized and controlled by sprinkling access roads and exposed areas with water. Implementation of this project would also reduce ground water recharge to the Amos-Ogilby-East Mesa ground water basin and would reduce or eliminate the wetland vegetation, and wetland habitat-dependent wildlife, which has developed from this leaking water along the adjacent unlined portion of the canal. However, plans for construction of this canal lining project have been suspended and there is no current schedule for implementation (Personal Communication, Michael Walker, USBR, 1996). 5.2.3.2. U.S. Bureau of Reclamation East Mesa Recharge Demonstration Recovery ProjectThe following description of the USBR East Mesa Recharge Demonstration Recovery Project (USBR East Mesa Recharge Project) was obtained from the Final EIS/EIR for the proposed Mesquite Regional Landfill (BLM and ICPBD 1995). The USBR East Mesa Recharge Project involves the development of a recharge/recovery operation in the vicinity of the All American Canal at the Coachella Canal branch to demonstrate the feasibility and economics of recovering water lost from the unlined canal. The proposal involves the installation of four (4), 16-inch diameter pilot demonstration wells, each to be dug within the recharge area to a depth of approximately 70 feet along the west side of the old, unlined Coachella Canal. Water recovered from the wells would be diverted to the lined canal to the east through an 8-inch diameter pipe. The USBR intends on conducting the recovery test by pumping 1,000 acre-feet of water from the East Mesa Basin over a one (1)-year period. Approximately an equivalent volume of water would be recharged to the area from the unlined canal, thereby resulting in no net loss of ground water in the East Mesa Basin during the test. If the recharge and recovery process proves successful, the USBR has indicated that the project could be made permanent, but the potential for long-term recharge and recovery pumping is uncertain and beyond the scope of this cumulative impact assessment. 5.2.3.3. Imperial Irrigation District East Mesa Ground Water Recharge Test ProgramThe following description of the IID East Mesa Ground Water Recharge Test Program (IID East Mesa Recharge Program) was obtained from the Draft Mitigated Negative Declaration prepared by the IID for the IID East Mesa Recharge Program (IID 1997). The IID East Mesa Recharge Program is a proposal to augment ground water in storage under East Mesa through the infiltration of excess water flows from the Colorado River, then recover most of the infiltrated water in times of lower water availability. The project is proposed for implementation in early 1998, when excess flood releases from Hoover Dam and Parker Dam would be available from the Colorado River. Approximately 20,000 AF of this excess flood water, or about four (4) percent of the excess flood flows available in 1997, would be diverted from the Colorado River down the All American Canal, then into the lined Coachella Canal, then into a section of the old, unlined branch of the Coachella Canal, where the water would infiltrate into the East Mesa aquifer as it did before the lining of the Coachella Canal in the early 1980's (see Section 3.3.2). As much as 90 percent of the infiltrated water would be recovered through pumping, which would essentially eliminate any net recharge to the East Meas ground water aquifer. The current program proposes only the 1998 test, but the potential for long-term recharge is possible if the test program is successful and excess flood flows are available in the future. However, this is beyond the scope of this cumulative impact assessment. Implementation of the IID East Mesa Recharge Program may temporarily displace some dispersed OHV recreational activity which has developed within the old Coachella Canal, and may temporarily affect a small amount of flat-tailed horned lizard habitat. No appreciable new surface disturbance would be necessary, and there would be little emission of PM10. 5.2.4. Military Uses5.2.4.1. Chocolate Mountain Aerial Gunnery RangeThe USMC maintains the Chocolate Mountain Aerial Gunnery Range (CMAGR) which, at its closest, is approximately ten (10) miles northwest of the Project area, immediately north of the Mesquite Mine and State Route 78. The CMAGR is actively used by various branches of the U.S. Armed Forces for military aircraft training and testing and for live ordnance delivery practice (BLM and ICPBD 1995). The activities associated with the CMAGR substantially increase ambient noise levels in the area during the activities (BLM and ICPBD 1995). The resulting increase in noise levels disrupts and alters sensitive wildlife species and their migratory patterns for intermittent short-term, and possibly long-term, periods. Low-level military overflights and ordnance explosions also contribute to airborne dust generation and some loss of vegetation and wildlife habitat. 5.2.4.2. Other Military UsesThe USMC conducts both daytime and nighttime helicopter flight training on public lands in and around the Project area and vicinity (Personal Communication, T.A. Manfredi, USMC, June 2, 1995). These training exercises are conducted at low-levels, sometimes including touch downs. The nighttime training includes the use of night vision goggles (NVG) and other night vision devices (NVD). This activity can increase ambient noise levels, increase airborne dust generation, and disturb both wildlife and recreational users (campers, hikers, etc.). Two (2) military Visual Flight Rule (VFR), low-level flying routes for fixed wing aircraft are also located in the vicinity of the Project area and cumulative impact study area (Personal Communication, T.A. Manfredi, USMC, June 2, 1995). VFR-299 (445th Military Airlift Wing-March Air Force Base) and VFR-1266, -1267, and -1268 (Marine Air Group-13-MCAS Yuma) each consist of six (6)"-mile wide flight corridors which are used by fixed-wing military aircraft during training or travel. Aircraft use of the VFR corridors through the cumulative impacts study area has the potential to also increase ambient noise levels, increase airborne dust generation, and disturb both wildlife and recreational users, although to a lesser extent than the low-level helicopter use. 5.2.5. Recreational UsesDispersed recreational activities, including OHV uses, hunting, rock hounding, and camping, are conducted in the cumulative impacts study area. These activities have the continuing potential to adversely impact environmental resources within the described cumulative impacts study area. OHV, hunting, rock hounding, and camping activities can impact air quality by increasing airborne dust generation from soils and pollutant emissions. These activities also place increased pressure on wildlife and have the potential for long-term impact on wildlife habitat. Dispersed recreational activities can also be a contributing factor in the destruction of cultural resources. 5.3. Evaluation of Potential Cumulative Impacts and Mitigation5.3.1. Hydrologic Resources (Ground Water)The existing ground water in storage in the Amos-Ogilby-East Mesa Basin has been estimated at 230 million acre-feet (126 million acre-feet in the Amos-Ogilby Basin alone), and the amount of recharge to the Amos-Ogilby-East Mesa Basin has recently been estimated to be 30,000 afy (see Section 3.3.2.1). The cumulative maximum total of annual ground water consumption from the basin by the relevant identified cumulative projects, including the Proposed Action, totals approximately 6,306 afy. Figure 5.2 presents a graph of the annual gross recharge to the Amos-Ogilby-East Mesa Basin, the annual consumption by applicable projects, and the resulting net recharge to the Amos-Ogilby-East Mesa Basin, for each year from 1998 through the year 2017. As shown, the annual consumption of ground water by all of these wells together is a relatively small percentage (a maximum of approximately twenty (20) percent) of the gross estimated recharge to the Amos-Ogilby-East Mesa Basin. The All American Canal Lining Project, if constructed, would probably result in only an estimated reduction in recharge to the basin of 6,770 afy (two-thirds (2/3) of the 10,000 afy assumed to seep into the Amos-Ogilby-East Mesa Basin). However, even with this reduction, the net recharge to the Amos-Ogilby-East Mesa Basin would still exceed the cumulative ground water consumption from the identified projects and uses. As stated in Section 5.2.3., the All American Canal Lining Project is currently on hold and has no schedule for implementation. The maximum total estimated cumulative annual consumption of ground water by the cumulative projects within the Amos-Ogilby-East Mesa Basin also represents approximately 0.003 percent of the ground water currently estimated stored in the Amos-Ogilby-East Mesa Basin (or approximately 0.005 percent of the ground water currently estimated stored in the Amos-Ogilby Basin alone). Based upon ground water drawdown estimates provided for the Project wells alone (see Section 4.1.3.2.2), and because these cumulative projects are widely scattered and the ground water consumption distributed, there should be no significant interference between the projects from their individual uses of the ground water resources. No mitigation measures are recommended. 5.3.2. Air ResourcesThe identified individual projects within the cumulative study area each emit most or all of the criteria air pollutants. However, since the monitored levels of these pollutants are well below the applicable established NAAQSs and CAAQS and the ambient levels of these pollutants produced by the Proposed Action are low, the addition of these criteria pollutants emitted by the Proposed Action to those from these cumulative projects would be below the level of significance. Emissions of O3 precursors (NOx and ROGs) from the Proposed Action could potentially contribute to exceedences of the NAAQS and CAAQS for O3. However, much of the O3 in Imperial County is transported into the basin from the South Coast Air Basin to the north and the Mexicali basin to the south, and are not formed from the reaction of O3 precursors within the Salton Sea Air Basin. Emissions of O3 precursors by the cumulative projects are also not likely to react to form O3 within the basin, and thus there is little potential for a significant cumulative impact from O3. As with the Proposed Action, the principal pollutant of concern emitted or generated by the identified cumulative projects is PM10. To evaluate the potential cumulative impacts from PM10 from the reasonably foreseeable future projects within the cumulative assessment area, the Air Quality Analysis conducted for the Proposed Action (see Appendix O) included calculations of the maximum 24-hour concentration of PM10 resulting from the Proposed Action at each of the other substantial sources of PM10 within the cumulative assessment area, including the American Girl Mine, the Picacho Mine, the Mesquite Mine, and the Mesquite Regional Landfill. Of these sources, both the American Girl Mine and the Picacho Mine are existing sources which are in the process of closing (their emissions of PM10 have been or are being reduced), and the Mesquite Mine is an existing source which is continuing. The effects of the emissions of PM10 from these projects are included in the ambient PM10 concentrations currently being monitored. However, the Mesquite Regional Landfill has not yet been constructed, and is not yet operating or producing PM10. The maximum 24-hour ambient PM10 concentration predicted from modeling Project emissions of PM10 were 0.61 µg/m3 at the Mesquite Regional Landfill. When this predicted value is added to the 27.4 µg/m3 maximum 24-hour ambient PM10 concentration predicted by modeling conducted for the Mesquite Regional Landfill (BLM and ICPBD 1995), and the 19.9 µg/m3 "background" annual ambient concentration monitored (at the Mesquite Mine) for the Mesquite Regional Landfill is also added, the total combined concentration of 47.9 µg/m3 is still below the 24-hour ambient PM10 CAAQS of 50 µg/m3. Thus, the cumulative impact of PM10 emissions from all of the cumulative projects is expected to be below the level of significance during typical conditions. However, local exceedences of the CAAQS for PM10 have occured in the past, and may continue in the future, during periods of high winds. The Proposed Action would contribute to these future exceedences during periods of high wind since there would still be a net increase in PM10 emissions from the Proposed Action. This would be a cumulatively significant effect. Mitigation measures to reduce emissions of PM10 from the cumulative projects (and the many other sources of PM10) are already contained in the ICAPCD regulations, and implementation of these rules and regulations are directed at reducing PM10 emissions sufficiently to attain compliance with the NAAQS and CAAQS in the future. 5.3.3. Biological ResourcesPlant and wildlife habitat would be adversely impacted by the cumulative effects of the identified projects. Surface disturbance within the respective project areas would result in a direct loss of habitat. In addition, the quality of habitat in neighboring areas would be indirectly impacted by project noise, surface disturbance, dust, and other off-site intrusions. Direct impacts are semi-quantifiable in terms of habitat loss, but indirect biological impacts are much more difficult to assess as they vary with site-specific conditions and the sensitivity of the species which occur in the respective habitat types impacted. A distinction can also be made between the cumulative temporary losses of habitat that is removed over the active life of project activities but can be reclaimed after project activities have been completed, and permanent losses of habitat that remain indefinitely at the end of project activities and after the respective project sites are closed. Both direct and indirect, and temporary and permanent, cumulative impacts result from the existing and reasonably foreseeable projects identified. As discussed in Section 3.5, multiple species of plants and wildlife were observed within the Project area or are known or suspected to occur within the areas of one or more of the projects evaluated by this cumulative impact assessment. Special-interest species (i.e., listed species, USFWS special status species, BLM sensitive species , etc.) which are known or suspected to be "resident" species in one or more of the project areas include: cheeseweed owlfly, flat-tailed horned lizard, chuckwalla, desert tortoise, loggerhead shrike, crissal thrasher, black-tailed gnatcatcher, and long-eared owl. A cumulative, incremental loss of primary breeding or nesting habitat for these species results from the projects. Special-interest species which may make "permanent" use of one or more of the project areas for varied uses (i.e., foraging, roosting or resting) include: desert bighorn sheep, Yuma puma/mountain lion, American badger, burrowing owl, prairie falcon, barn owl, California leaf-nosed bat, greater western mastiff bat, spotted bat, Townsend's big-eared bat, Yuma myotis, cave myotis, small-footed myotis, occult little brown bat, and desert pallid bat. A cumulative incremental loss of foraging, roosting, resting, or other limited habitat use results from the projects for these species. Special-interest species which may make "occasional" use of one or more of these cumulative project areas as migrant or seasonal foraging or resting areas, primarily in the winter months, include: northern harrier, sharp-shinned hawk, peregrine falcon, golden eagle, ferruginous hawk, Cooper's hawk, Gila woodpecker, and Vaux's swift. An incremental loss of seasonal or transient habitat for these species results from these cumulative projects. Many other wildlife species are also known to use one or more of the cumulative project areas for resident, permanent, and occasional uses (see Section 3.5.6). Notable among these species is mule deer, which is a permanent resident species, and other game species such as Gambel's quail, mourning dove, and white-winged dove. Other common mammals include: antelope ground squirrel, Merriam kangaroo rat, desert woodrat, black-tailed jackrabbit, kit fox, coyote, and wild burro. A cumulative incremental loss of habitat results for these and other permanent, resident, or migrant species which use one or more of the cumulative project areas. Similarly, a cumulative incremental loss of habitat results for both sensitive plant species and common plants which occur in the areas disturbed by one or more of the identified projects. The cumulative surface disturbance from all of the identified mine projects would total approximately 6,552 acres. The approximate areas of surface disturbance from the other identified cumulative projects and non-dispersed activity areas with surface disturbance include the Mesquite Regional Landfill (3,657 acres), Gold Rock Ranch (20 acres), and Citrus Heights (475 acres). Thus, the combined concentrated areas of surface disturbance total approximately 10,686 acres of potential desert vegetation and wildlife habitat that is or would be unavailable over the respective lives of these projects. However, these individual projects in the cumulative impact analysis are dispersed over a regional area at least 20 miles long by 15 miles wide (approximately 300 square miles, or nearly 200,000 acres) in which large vacant tracts of land, with similar vegetation and wildlife habitat, remain. Dispersed recreation and military uses of the area put added pressure on wildlife species, in particular on game species and on wildlife intolerant of human activities. Dispersed recreation and military uses of the area also adversely impact vegetation and habitat over wide, unconcentrated areas. However, most of these dispersed activities are intermittent and/or temporary, and except for small, localized areas of concentrated or recurrent use (e.g., campsites or OHV use areas), both vegetation and wildlife can typically tolerate the level of these activities. Concern exists over the continuing loss of wildlife habitat, in particular the loss of microphyll woodland habitat which exists in the desert washes that cross much of this cumulative analysis area. Because of the limited forage and cover available in the alluvial flats and uplands between the wash systems, the microphyll woodland habitat is necessary for the success of many species which occur in the area. Microphyll woodland habitat is considered important by the CDFG and a necessary component of the ecosystem for the continuing success of deer and other sensitive species which utilize the habitat. Aerial photographs of the general area made available by Glamis Imperial were used to grossly estimate the amount of microphyll woodland habitat within the cumulative impact analysis area. Microphyll woodland habitat is easily distinguished from upland communities on the photographs as dark ribbons of vegetation within lighter areas of sparse vegetation (see Figure 3.16). Limited ground-truthing of the vegetation present in the washes intersecting roads within the cumulative impact assessment area confirmed that the vegetation is comprised of microphyll woodland species similar to those observed in the Project area. An estimate of the total area of microphyll woodland habitat within the cumulative impacts assessment area was based on a visual comparison of the relative density of wash systems external to the Imperial Project area with the density of wash systems within the project area, known to be approximately five (5) percent (Bamberg and Hanne 1995b; Appendix F). Using this technique, it is roughly estimated that approximately four (4) to eight (8) percent of the nearly 200,000 acres (i.e., about 7,680 to 15,360 acres) evaluated in this cumulative impact analysis may be microphyll woodland habitat. Assuming that, on average, a comparable proportion (i.e., four (4) to eight (8)percent) of the microphyll woodland habitat is directly impacted by surface disturbance within the areas of the combined cumulative projects, then a total of approximately 427 to 855 acres of microphyll woodland has been or would be lost within the cumulative assessment area. Because each individual cumulative project would be required to implement appropriate mitigation and compensation measures (such as those contained within a CDFG Stream Alteration Agreement), this cumulative impact on microphyll woodland habitat is below the level of significance. (Validation of the estimated percentage of microphyll woodland habitat in the cumulative assessment area may be taken from the preliminary results of the vegetation mapping being done for the NECDMP (BLM 1997). Although the NECDMP has not specifically identified "microphyll woodland" (or "tree/shrub," as described in Section 3.5.5) as a vegetation type in its database, the five (5) percent of the Project mine and process area mapped for this EIS/EIR as "microphyll woodland habitat" is included in the approximately 25 percent of the Project mine and process area labeled on the NECDMP maps as "desert dry wash woodland." The remainder of the Project mine and process area is shown on the NECDMP maps as "Sonoran creosote scrub." In the area of the cumulative assessment, the NECDMP maps show that approximately 40 to 50 percent of all of the lands are "desert dry wash woodland." The ratios of these two (2) vegetation/habitat types within the Project mine and process area and in the cumulative assessment area (5:8 and 25:40) are identical.) The cumulative indirect impacts resulting from the identified cumulative projects are assumed to be proportionately the same as those described for the Project, and would also be expected to be similar with respect to the temporary loss of habitat occurring over the life of the cumulative projects and the permanent loss of habitat after each of the cumulative projects had been closed and the area reclaimed. Individual projects are required to implement measures to mitigate impacts on desert tortoise and other listed or sensitive plant and animal species, which reduces the potential for both individual and cumulative impacts to wildlife. Because of the implementation of the project-specific mitigation measures and the widely dispersed nature of the cumulative projects, the cumulative effects of the identified cumulative projects and uses on biological resources would be below the level of significance. 5.3.4. Cultural ResourcesThe area of cumulative analysis for cultural resources, which generally corresponds to the area of cumulative analysis for the other resources, includes the area from the Algodones Sand Dunes in the west to the Colorado River in the east, and the international border with Mexico to the south to an east-west line through the junction of Ogilby Road and Highway 78 to the north. The Quechan Tribe has expressed strong concerns for the cumulative loss of cultural heritage sites within this area and elsewhere in the territory traditionally occupied by Yuman-speaking tribes. In order to assess the cumulative impacts of the Imperial Project and the other cumulative projects within this area of cumulative analysis, two (2) data sources have been utilized. First, consultation conducted with the Quechan Tribe helped identify the impacts of past project to sites of traditional cultural value. Second, an archaeological literature review was conducted to identify cultural resource sites that have been reported for projects in the area of cumulative analysis. The cumulative effects analysis focused on prehistoric archaeological sites and sites of concern to the Quechan Tribe. Non-Indian historic period resources are not considered because the Imperial Project will not have an adverse effect on any such resources and, consequently, would not have a cumulative impact on them. Cumulative effects to resources of traditional cultural concern to the Quechan are discussed first, followed by consideration of cumulative impacts to prehistoric archaeological sites. Based upon substantial input received from the Quechan Tribe, the cumulative effects of past and current development projects and other land uses on cultural resources located within their traditional territory have been viewed as significant by the Quechan Tribe. Among the projects specifically mentioned by the Quechan Tribe as having contributed to the cumulative loss of cultural resources within the area of cumulative analysis are mining uses (both the modern American Girl Mine Project and the Mesquite Mine, plus "The Potholes" area, located northwest of Laguna Dam; the historic Tumco Mine, located near the Oro Cruz portion of the American Girl Mine Project in the Cargo Muchacho Mountains; and the historic Pilot Knob rock quarry); commercial uses (such as the proposed Mesquite Regional Landfill, the existing Imperial County Picacho Landfill, located on Picacho Road inside the boundaries of the Ft. Yuma Indian Reservation, and land development for agriculture, in general); water projects (specifically the construction of the All American Canal); military uses (General Patton's training exercises in 1940's in the Picacho Basin); transportation/transmission projects (construction of the Arizona Public Service/San Diego Gas and Electric Company Interconnection Project 500 kV electric transmission line, the Southern Pacific Railway, and Interstate Highway 8); and archaeological survey activities for other projects which included artifact collection (Personal Communication, Lorey Cachora, Quechan Tribal member, November 4, 1997). In addition, the Quechan Tribe has indicated that other activities located outside of the area of cumulative analysis have similarly resulted in, or will result in, the cumulative loss of cultural resources (such as the Marine Corps Air Station Yuma; U.S. Army Yuma Proving Grounds; Luke Air Force Base/Goldwater Bombing Range; the proposed Ward Valley low-level nuclear disposal site, and the development of Yuma and Winterhaven) (Personal Communication, Lorey Cachora, Quechan Tribal member, November 4, 1997). The Quechan believe that these and other development projects and land use activities have resulted not only in cumulative effects on highly sensitive or sacred resources, but also on such cultural resources as flaking stations, lithic scatters, and pot drops that are generally considered by archaeologists to represent little scientific value after the impacts to these resources have been adequately mitigated. However, the Quechan believe that the most significant impacts to cultural resources have been the destruction or damaged to highly sacred and important mountains, trails, "teaching areas," and geoglyphs. Specific examples of significant impacts offered by Quechan Tribal members include impacts from rock quarrying to Pilot Knob; impacts to key trails, geoglyphs and other resources by the Mesquite Mine and proposed Mesquite Regional Landfill; impacts to a key teaching area located in the Picacho Basin area; and destruction of a portion of the Medicine Trail by the Picacho Mine. Since the Medicine Trail is one (1) of only two (2) key trails that allow actual and dream travel to Avikwaame, the single most important place in traditional Quechan culture and religion, the proposed impacts from the Imperial Project to the Trail of Dreams in the Project mine and process area, taken together with the recent destruction of a portion of the Medicine Trail in the vicinity of Picacho Peak, would combine to cut-off both key corridors to Avikwaame. More generally, the Quechan Tribe believes that these past and current projects have already destroyed key places of extreme importance to their cultural survival, and that implementation of the Imperial Project would irreversibly add to these affects on their cultural and religious beliefs and practices. From an archeological perspective, the cumulative effects of the loss of prehistoric cultural resources by the identified cumulative projects would not be considered significant for certain types of resources such as lithic scatters, flaking stations, ceramic scatters, temporary camps, quarry sites and sleeping circles. The reasons for this conclusion are that impacts to sites such as these have generally been adequately mitigated for projects approved since the implementation federal and State environmental and cultural preservation laws; many of the identified cumulative projects are separated by large distances; and these cultural resources are relatively plentiful in the area of cumulative analysis. The cumulative effects of the loss of other types of prehistoric resources,
however, would be considered significant. Specifically, the cumulative effects
of these projects on highly sensitive, sacred, or scientifically valuable
resources such as sacred mountains, trails, rock art, major habitation sites,
cremation and burial areas, and geoglyphs have been adverse when taken together,
even if impacts to specific individual projects were mitigated at a project-specific
level. The data provided in Table 5.1 support the conclusion that the Imperial Project would increase the cumulative adverse impact on key types of cultural resource sites. Nearly every cultural resource report found one (1) or more of the following cultural resource feature types within the individual project areas of potential effect: geoglyphs, intaglios, petroglyphs, rock rings, trails, or trail shrines. Archaeological recordation of such features is rarely adequate to document their loss, and archaeological methods have not been developed that adequately place many of these types of cultural features in a cultural context that permits their informational and historic values to be recovered. Numerous of these same cultural feature types would be destroyed by the Project. Additionally, the data in Table 5.1 support the perspective of the Quechan that recent projects have resulted in significant cumulative effects upon sites of high value to their contemporary heritage and future cultural survival. Thus, implementation of the Project, taken together with past, current, and reasonably foreseeable future projects would contribute to the already significant cumulative effects to cultural resources.
5.3.5. Visual ResourcesEach of the identified cumulative projects are located, at least in part, on or adjacent to public lands administered by the BLM within the CDCA. However, except for the immediately adjacent Mesquite Mine and Mesquite Regional Landfill, no more than one of the cumulative assessment projects is visible from any important viewing location at any one time within the cumulative impact study area. Because there is no cumulative increase or combined visual impact from the multiple cumulative projects, the cumulative effects of these projects on visual resources would be below the level of significance. 5.3.6. NoiseThe individual cumulative projects generate noise which would be audible outside the respective project areas. However, the respective cumulative project areas are each located at great enough distances (approximately five (5) to ten (10) miles) from the next nearest project or concentrated use that although particularly loud noises (such as blasting) may be audible between those cumulative project areas located closest to each other, other noises should not be audible, and the sound levels would not typically be intrusive. With the implementation of typical project-specific mitigation measures, the identified cumulative projects would not result in a significant cumulative noise impact. 5.3.7. RecreationThere are no unique recreational resources within the cumulative assessment area which are threatened with disruption or elimination through any of the cumulative projects. Dispersed recreational opportunities are those principally available on the public lands located within the cumulative impact area, and there are approximately 4.4 million acres of BLM Class L lands in the CDCA which are also generally available for these dispersed recreation activities. Given the availability of large areas with similar, although not identical, opportunities for dispersed recreation, the cumulative effects on recreation resources would be below the level of significance.
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