Medicine Lake basin is located at the summit of Medicine Lake Highlands which is a broad shield volcano about 20 miles (32 km) wide. The initial shield reached an estimated height of 2,500 feet (762 m). Subsequent collapse of the summit formed a caldera 6 miles (10 km) long by 4 miles (6 km) wide, with a rim 500 feet (152 m) below the former summit. Ring fractures around the edges of the caldera served as conduits for andesitic lava that flowed into the caldera, building up a rampart of volcanoes which obscure the boundaries of the original caldera and form Medicine Lake Basin (Weiss 1997, Evans and Zucca 1988). The approximate location of the original caldera is shown on Figure 3.2.7. Major and minor faults are visible throughout the Medicine Lake Volcano, many of which have the generally north-south alignment that is predominant regionally (Weiss 1977). Many fissures, vents, craters, and cinder cones show a clear linear alignment and also coincide with the circular rampart surrounding the Medicine Lake Basin. Weiss (1997) identified two hydrologic units within the Medicine Lake Highlands: the shallow groundwater system that occurs only within the Medicine Lake Highlands; and the geothermal reservoir. The shallow groundwater system is a perched system that occurs at an elevation approximately 3,300 feet (1,000 m) higher than the elevation of the regional groundwater system of the Modoc Plateau. The water source for the shallow groundwater system is infiltration of precipitation (primarily winter snow). The geothermal reservoir is separated from the shallow groundwater by a thick sequence of non-porous highly altered volcanic rocks (see Section 3.2.2.1). Evidence for the thick impermeable cap rock includes lithologic logs from temperature gradient and deep exploration wells and temperature gradient data. Well locations and groundwater elevations from the shallow wells, temperature gradient holes, and deep geothermal exploration wells are shown in Figure 3.2.2. Groundwater flow directions are also shown. Groundwater elevations are highest in the center of the Medicine Lake Highlands with flow moving radially away from the center. Water quality analyses are available for only one shallow well in the Medicine Lake Basin as shown in Table 3.2.9. The water in the CEGC Water Well is considered good quality water with a low TDS concentration of only 37 ppm and other measured constituent concentrations well within drinking water standards. Water quality of the geothermal reservoir is discussed in Section 3.2.2.3.

Table 3.2.9: Chemical Characteristics of Groundwater Sampled from the CEGC Water Well

Constituent (ppm)	Analysis
Calcium	4.5
Magnesium	2.3
Sodium	3.3
Potassium	3
Chloride	1.2
Sulfate	<1.0
Nitrate	<0.2
Total Dissolved Solids	37
Silica	27
Hardness	22
Electrical Conductivity (µmhos)	57
Well located at T43N, R3E, Section 1, dddd Source: Weiss 1997

Data for other wells within the Medicine Lake Highlands are shown in Table 3.2.10. Data in this table include the depths of the wells, depths of screened intervals, depths to groundwater, and elevations of groundwater. Eight of the wells are geothermal exploration holes, with total depths ranging from 1,997-2,968 feet (609-905 m), that were used to measure temperature gradients and later perforated to measure groundwater levels. Five of the wells in Table 3.2.10 are shallow, with depths ranging from 14 feet (4 m) to 535 feet (163 m). Depth to shallow groundwater at the Phillips Well, which is located at the north edge of the area of the Proposed Action, is 98 feet (30 m).

3.2.2.6 Regional Hydrology

The Medicine Lake Volcano is a composite shield volcano, 15 miles (24 km) in diameter, located on the western margin of the Modoc Plateau and 33 miles (53 km) east of Mount Shasta. The highly faulted region around Medicine Lake Volcano is a transition zone between the Cascade volcanic arc and the Basin and Range province to the east (Donnelly-Nolan 1988). Medicine Lake Volcano is located within an oblique, right-slip, pull-apart graben connecting the Klamath (or Tule Lake) graben with the Fall River (or McArthur) graben (Personal Communication — Thomas L.T. Grose, Geologist, Colorado School of Mines; September 16, 1998). In the area between the Medicine Lake Highlands and Mount Shasta, there are east-northeast to west-southwest trending Quaternary high angle vent and dike alignments (Personal Communication — Bob Christiansen, USGS; September 21, 1998). This feature has been referred to as the Vulcan Lineament (Ciancanelli 1983). It is possible that the vents and dikes, aligned nearly perpendicular to the regional groundwater flow direction, could act as barriers to groundwater flow from the north. To the west of Medicine Lake Highlands, the Vulcan Lineament may form a subsurface block to north-south water movement between Mount Shasta and the Medicine Lake Highlands. To the east of Medicine Lake Highlands, there is no subsurface block and groundwater flows from north to south (Weiss 1997).

Beginning approximately 4 miles (6 km) to the southwest of Medicine Lake, a lava flow known as the Giant Crater Lava Flow extends 27 miles (43 km) to the southeast. At the south end of the lava flow, the Fall River Springs emanate from the lava flow and flow at a rate of approximately 1,421 cubic feet per second (cfs) (40,244 liters per second) (Rose et al. 1996). To the south of the Fall River Springs, the Fall River Valley is located in a graben bounded by stepped northwest-southeast trending normal faults and a northwest-southeast trending horst (Weiss 1997; Grose 1996; and Rose et al. 1996).

3.2.2.6.1 Regional Surface Water

Medicine Lake Crater is a Hydrologic Subarea of the Pit River Hydrologic Unit, which is part of the Central Valley Basin. The Medicine Lake Subarea encompasses the Medicine Lake basin and the area to the south, including Medicine Lake, Little Medicine Lake, and Arnica Sink. Within the Medicine Lake Crater Subarea, surface drainage is generally to the south (RWQCB 1994). Although most surface water in Medicine Lake Basin flows toward the Lake but infiltrates before reaching the Lake, any surface water that does leave the basin flows to the south. Surface water drainage basins in the Medicine Lake regional area are shown in Figure 3.2.8. Both in the Medicine Lake Highlands and in the Modoc Plateau, the occurrence of surface waters is sparse due to the highly permeable surface rocks. The closest major surface water body to the Medicine Lake Highlands is Tule Lake, located approximately 20 miles (32 km) due north. To the south, the start of the first major tributary in the region, the Little Tule River, is located approximately 33 miles (53 km) from Medicine Lake (Weiss 1997). Table 3.2.11 shows the location and water quality data for various springs, lakes, and rivers in the region surrounding Medicine Lake Highlands. Figure 3.2.5 shows the locations of the surface water features. The springs occur about 10 miles (16 km) south, 16 miles (26 km) southeast, and 10 miles (16 km) west of Medicine Lake. No springs are found north of the Lake except for one seep at Lava Beds National Monument. The Fall River springs, one of the largest spring groups in the United States, are located 32 miles (51 km) south-southeast of Medicine Lake. The estimated flow rate of the spring group flowing out of the south end of the Giant Crater Lava Flow is approximately 1,421 cfs (40,244 liters per second) (Rose et al. 1996). Davisson and Rose (1997) studied the isotopic signatures of the Fall River Springs and springs in the Medicine Lake Highlands. They found that, despite expected elevation effects, the variations in oxygen isotopic signatures of precipitation from the entire Medicine Lake Volcano and Giant Crater lava field is no more than about 1 per mil.2 Davisson and Rose also indicated that the highest elevation regions of Medicine Lake Volcano (i.e., Medicine Lake Basin) do not receive a sufficient amount of annual precipitation to sustain all the Fall River Springs flow. The flow volumes require that the entire area encompassing Medicine Lake Volcano and the Giant Crater lava field must have enhanced permeability (fractures and lava tubes) that promotes the recharge of most of the annual precipitation and focuses groundwater transport south to the Fall River Springs. The amount of precipitation received by the Medicine Lake Volcano and Giant Crater Lava Field areas together is sufficient to recharge the Fall River Springs (Hydrodynamics Group 1997a). Other potential recharge areas for the Fall River Springs have been suggested (Weiss 1997) including the Tule Lake-Klamath Lake area, the northwest extension of the Fall River Graben, and the Vulcan Lineament-Caribou Wilderness Area. The chemical variation of the Fall River Springs is further evidence of their widespread source area. Thompson and Chappell (1984) reported that the Fall River Springs have calcium-magnesium bicarbonate waters in the springs on the east and west sides of the Fall River Valley and sodium bicarbonate waters in springs in the middle of the Valley, indicating that the waters do not all derive from the same source. Recent data also support this chemical variation (Mariner et al. 1998). Isotopic ratios can provide clues as to source areas for spring waters. Deuterium/chloride isotopic ratios in the Fall River Springs indicate that the spring water does not have a geothermal source (Mariner et al. 1998). Deuterium and oxygen-18 isotopic values in the Fall River Springs, however, indicate that water that recharged the shallow groundwater in Medicine Lake Basin could contribute to the springs, although the data do not prove the contribution (Mariner et al. 1998).

3.2.2.6.2 Regional Groundwater

Three hydrologic units have been identified in the Medicine Lake Highlands and the surrounding region (Weiss 1997): Hydrologic Unit No. 1: Medicine Lake Highlands Volcanic Massif Groundwater occurs in the young volcanic rocks of the Medicine Lake Highlands as a perched water system above the geothermal reservoir and the Modoc Plateau regional groundwater aquifer. Recharge to this hydrologic unit is through infiltration of precipitation into very porous surface volcanic rocks; Hydrologic Unit No. 2: Modoc Plateau The Modoc Plateau contains mostly volcanic rocks with some lake sediments in local areas. The main hydrologic units in the region are located within Pliocene to Recent lava flows (Weiss 1997). These younger basalt flows are highly fractured and porous with many interconnected lava tubes, making them very permeable. The shallow groundwater flowing through these volcanic rocks is unconfined. Groundwater also occurs in localized lake sediments in the Tule Lake area and the Fall River Mills area; Hydrologic Unit No. 3: Medicine Lake Highlands Geothermal Reservoir The Medicine Lake Highlands Geothermal Reservoir is described in Section 3.2.2.1. Recharge to the geothermal reservoir is believed to be from deep groundwater from the Modoc Plateau aquifer. The regional groundwater flow direction in the Modoc Plateau aquifer is from north to south (Weiss 1997). The thickness of the water bearing units in the Modoc Plateau varies considerably. In the Tule Lake region, high quality groundwater occurs between the depths of 150 and 2,700 feet bgs (46 and 823 m bgs). In the Fall River Mills area, good quality groundwater only occurs to an approximate depth of 400 feet bgs (122 m bgs) (Weiss 1997). Data for selected wells located in the regional area surrounding the area of the Proposed Action are presented in Table 3.2.12, with locations shown on Figure 3.2.2. Water levels in these wells, together with the water level data from wells in the Medicine Lake Highlands, indicate that groundwater moves radially away from the summit area of the Medicine Lake Volcano, and that regional groundwater flow is from north to south (see Figure 3.2.2). Water quality analyses from shallow groundwater wells in the Telephone Flat Project regional area are shown in Table 3.2.13. The wells all show good quality water with low TDS concentrations and other constituents within standard drinking water levels.

3.2.3 Environmental Consequences

In this section, the environmental consequences of the Proposed Action are discussed, along with the consequences of each the other Project Alternatives and the No Action Alternative.

3.2.3.1 Significance Criteria

This section discusses key issues related to the proposed Project and lists the significance criteria used in this analysis. The key hydrology issues identified and evaluated in this section relate to the effects of the Project on water quality and quantity in the Medicine Lake area, as well as regional water quality and quantity. Specific concerns related to hydrology that have been identified as key issues and were described in Section 1.10.3.3. These include: Concern that geothermal development in the Medicine Lake Highlands may affect groundwater resources and adversely impact the quality or quantity of flow observed in the Fall River headwater springs group. These springs support threatened and endangered aquatic and riparian habitat, support a highly regarded sports fishery, contribute to hydroelectric power downstream of the springs, and provide a substantial portion of the recharge to Shasta Lake. Concern that geothermal development would compete for limited groundwater resources in the Medicine Lake Basin, particularly during drought conditions. Concern that unintentional releases via wells, pipelines, or spills could impact the quality of surface and groundwater.

Effects of the Project on water resources would be considered significant if the Project would result in: Substantial depletion or degradation of groundwater resources; Reduction of the volume of water to surface water bodies in the area; Contamination of a public water supply; Substantial interference with groundwater recharge; Unnecessary depletion of geothermal resources; or Well blowouts or other geothermal hazards.

3.2.3.2 Assessment Methodology

Activities associated with the proposed Project were evaluated to assess their impacts to surface water and groundwater resources. Water use associated with the proposed Project activities was estimated and compared to estimates of the amount of available groundwater and surface water and the rate of groundwater and surface water recharge. Project activities were also evaluated with respect to the potential for degradation of surface water or groundwater quality as a result of potential Project-related spills, releases, fluid production and injection, and air emissions.

3.2.3.3 Proposed Action

3.2.3.3.1 Environmental Consequences of the Proposed Action

The effects of the Proposed Action include the effects of water use; the effects of geothermal fluid production and injection on water quantity; the effects of increased surface runoff; the effects of flooding; the effects of geothermal drilling, production, and injection on water quality; the effects of air emissions on water quality; the effects of sanitary waste on water quality; the effects of chemical and hazardous material spills on water quality; the effects on the life expectancy of the geothermal resource; the effects of injection on reservoir characteristics; and the effects on regional thermal features. Effects of Water Use: The projected water consumption for the Proposed Action construction, operation, and decommissioning phases is shown in Table 2.2.8. Construction Water for drilling and construction activity would be trucked or piped from two existing wells in the Arnica Sink area currently used by CEGC and Modoc National Forest. Groundwater would be used for dust abatement on unpaved roads and during construction activities. Approximately 15.3-24.5 ac-ft/yr would be used for dust abatement and other construction activities. Compared to the evapotranspiration-corrected annualized average groundwater recharge into the Medicine Lake Basin (estimated to be approximately 23,123 ac-ft/yr; Weiss 1997) the water used for dust abatement and other construction activities would account for less than one percent. Groundwater consumption for construction and construction-related activities would have a small effect on local groundwater availability and would have no effect on local surface waters, including Medicine Lake and Paynes Springs, or the regional groundwater system. If recharge were reduced during drought, the percentage of recharge used for Project activities would be higher, but still would not be expected to be significant compared to the amount of recharge. Additional water use required during the construction period includes about 0.6 acre-ft for fire protection storage (likely to be a one time only requirement), and about 4.0 acre-ft for domestic water use (non-drinking water). Impact 3.2.3.3-1: Construction and construction-related activities would consume approximately 15.3-24.5 ac-ft/yr of groundwater from the shallow aquifer for dust abatement and up to 4.6 ac-ft/yr for fire protection and domestic uses. Significance of the Impact: This impact is considered less than significant and no mitigation measures are required.

Table 3.2.13: Chemical Characteristics of the Groundwater in Regional Wells

Constituent (ppm)	Pumice Stone Well	Lost Iron Well	Hambone Well	LBNM NPS Well a
Location:	T43N,R2E,14,acd	T42N,R2E,28	T41N,R3E,31	T45N,R4E,28,aaa
Calcium	3.1	4.3	6.9	3
Magnesium	0.56	1.6	5.7	0.9
Sodium	1.3	1.3	2.8	26
Potassium	1.2	6.3	1	1.8
Carbonate	0	0	0	0
Bicarbonate	13.9	31.2	48.5	89
Chloride	<1.8	<1.8	<1.8	11
Sulfate	<5.0	<5.0	<5.0	3
Nitrate	<0.4	0.9	0.4	0.6
Iron	<0.05	19.6	<0.05	0
Manganese	<0.01	1.4	0.03	NR
Copper	<0.01	<0.01	<0.01	NR
Total Dissolved Solids	36	64	88	150
Boron	<0.01	<0.01	<0.01	0.3
Silica	16	19	23	49
Hardness	10.1	17.3	40.7	36
Electrical Conductivity (µmhos)	32	64	95	185
pH (pH Units)	6.3	6.4	7.1	7.8
Resistivity	312.5	156.2	105.3	NR
Delta Oxygen 18 (per mil)	-12.93	-10.74	-12.58	NR
Delta Deuterium (per mil)	-95,-96	-92	-96	NR
Source:	Cosens-Gallinatti 1984	Cosens-Gallinatti 1984	Cosens-Gallinatti 1984	Weiss 1997
a LBNM NPS Well is Lava Beds National Monument National Park Service Well

According to the geothermal development drilling schedule, 6 wells would be drilled in the first year, 5 wells in the second year, and 2 wells in the third year. In the fourth to fiftieth year, up to 12 additional wells may be drilled (Weiss 1997). Water consumption during drilling operations is projected to be about 9,000 gallons of water per day for exploratory and production test wells, with up to 40,000 gallons per day used when drilling fluid circulation is lost (Weiss 1997). Each well is expected to take from 45-90 days to complete. Conservatively assuming 90 days to complete, with 10 of those days spent fighting lost circulation, each well would require about 1,120,000 gallons (3.44 acre-ft). The evapotranspiration-corrected annualized average groundwater recharge into the Medicine Lake Basin is estimated to be approximately 23,123 ac-ft/yr. Given the projected drilling water consumption rates, drilling water usage would be less than 1 percent of the annualized estimated local shallow groundwater recharge even in the first year when 6 wells would be drilled. The maximum shallow groundwater consumption (6,720,000 gallons or 20.6 acre-ft) would occur the first year. Withdrawal of 6.7 million gallons of water from the shallow aquifer would have a temporary, adverse effect on local groundwater resources and no effect on local surface water resources, including Medicine Lake and Paynes Springs. Because the shallow groundwater system in the Medicine Lake Highlands is a perched system that is not connected to the regional groundwater system, pumpage from the shallow groundwater system would have no effect on the regional groundwater system. Even if recharge were reduced during drought, the percentage of recharge used for Project activities would be higher, but still would not be expected to be significant compared to the total amount of recharge. Impact 3.2.3.3-2: Geothermal well drilling operations for the Project would consume approximately 20.6 acre-ft of groundwater during the first year of construction and lesser amounts in subsequent construction or well drilling years. Significance of the Impact: This impact is considered less than significant and no mitigation measures are required. The combined total use of groundwater from the shallow aquifer for the first year of construction and well drilling activities would be approximately 49.8 acre-ft, the maximum amount of groundwater consumption of any one-year period of the Project. This annual water use is less than 1 percent of the annualized average groundwater recharge into Medicine Lake Basin. Groundwater consumption for the construction period would have a small effect on local groundwater availability and would have no effect on the local surface water system and no effect on the regional groundwater system. If recharge were reduced during drought, the percentage of recharge used for Project activities would be higher, but would be expected to be small compared to the amount of recharge. Impact 3.2.3.3-3: The combined total of groundwater consumption for geothermal well drilling operations and construction-related uses for the Project would be about 49.8 ac-ft/yr during the first year of construction and lesser amounts in subsequent construction or well drilling years. Significance of the Impact: This impact is considered less than significant and no mitigation measures are required, but the following other measures are provided to reduce the adverse effects of the impact. Other Measure 3.2.3.3-3a: The Project Applicant, CEGC, has submitted a proposed hydrology monitoring plan to the BLM. The Project Applicant shall implement the approved monitoring plan in coordination with hydrologic monitoring which may be required for the proposed Fourmile Hill Geothermal Project and in conformance with the monitoring requirements of the BLM and USFS. The proposed hydrology monitoring plan includes, but is not limited to the following: Collection of baseline water level and water quality data; Monitoring of water levels in wells; Monitoring lake stages; and Monitoring well, spring, and lake water quality. Other Measure 3.2.3.3-3b: Groundwater pumping rates shall be reduced if monitoring detects potentially significant adverse effects to water availability, and these effects can be attributed to Project pumping of local groundwater. Other Measure 3.2.3.3-3c: In the event that damage to private groundwater well(s) can be reasonably attributed to excessive pumping of the shallow groundwater by the Project, Project Applicant shall repair the damage to the private well(s) and modify Project operations to prevent further well damage.

Operations Water from the shallow groundwater wells in Arnica Sink would be used to initially charge the power plant cooling towers (approximately 0.7 acre-ft). After initial charging, makeup water to replace evaporative cooling tower losses would come from geothermal production fluid steam condensate. Periodic recharge, or partial recharge, of the cooling tower could be required after a maintenance shutdown and is expected to occur less than twice per year with an estimated water usage of 1.2 ac-ft/yr. Water from the shallow groundwater wells would also be used for domestic use at the power plant site (approximately 4.0 ac-ft/yr). Drilling of production and injection wells would continue during the operations period. According to the geothermal development drilling schedule (Weiss 1997), 5 wells would be drilled in the second year of the Project (first year of operations), and 2 wells in the third year. In the fourth to fiftieth year, up to 12 additional wells may be drilled. Water consumption for well drilling during operations would be about 17.2 ac-ft during the second year of well drilling (first year of operations); and 6.9 acre-ft the third year; and collectively, a total of about 41.2 ac-ft over a 46-year period extending from the fourth to fiftieth years of operations of makeup wells (i.e., 1,120,000 gal per well for up to 12 makeup wells). Total water usage for well drilling during the operations period would average 1.3 ac-ft/yr. Use of shallow groundwater for the power plant and well drilling combined during operations would total approximately 6.5 ac-ft/yr. Compared to the evapotranspiration-corrected annualized average groundwater recharge into the Medicine Lake Basin, the water used for power plant operations, domestic use, and well drilling during operations (6.5 ac-ft/yr) would be less than 1 percent (0.028%) of the total recharge. Groundwater consumption for the Project would have a small effect on local groundwater availability and would have no effect on local surface water including Medicine Lake and Paynes Springs and no effect on the regional groundwater system. If recharge were reduced during drought, the percentage of recharge used for Project activities would be higher, but would be expected to be small compared to the amount of recharge. Impact 3.2.3.3-4: The Project would consume approximately 6.5 ac-ft/yr of groundwater from the shallow aquifer during the operations phase. Significance of the Impact: This impact is considered less than significant and no mitigation measures are required, but the following other measure is provided to reduce the adverse effects of the impact. Other Measure 3.2.3.3-4: When feasible, geothermal production water would be used to meet well drilling water requirements, thus reducing the amount of water required from the shallow aquifer. Decommissioning There would be no additional wells drilled during decommissioning. Therefore, groundwater would be used for domestic uses only (approximately 4.0 ac-ft/yr). Compared to the evapotranspiration- corrected annualized average groundwater recharge into the Medicine Lake Basin, the water required for domestic use during decommissioning is considered negligible. There would be a small effect on local groundwater availability and no effect on local surface water or on the regional groundwater system. If recharge were reduced during drought, the percentage of recharge used for Project activities would be higher, but would be expected to be small compared to the amount of recharge. Impact 3.2.3.3-5: Domestic water use during decommissioning would consume approximately 4.0 ac-ft/yr from the shallow aquifer. Significance of the Impact: This impact is considered less than significant and no mitigation measures are required. Effects of Geothermal Fluid Production and Injection on Water Quantity: During the first 2 years of well field operations, approximately 9 flow tests would be conducted on 6 different well pads. During years 3-53, a maximum of 2 well tests per year would be conducted. The first 2 well flow tests are scheduled to be 30 days in duration. Subsequent tests are scheduled to be 15-day tests except for one, 90-day, resource test in the second year of well field development and one, three-day, well work over once every 2 years. The planned well tests would proceed according to the venting schedule shown in Table 3.2.14. The net loss of geothermal fluid from the geothermal reservoir during well testing was calculated using the venting schedule shown in Table 3.2.14 and the following assumptions:

Mass flow at 100% flow rate: 367,000 lb/hr NCG content: 512 ppm by weight in reservoir H2S content: 3.6% of NCG TDS: 2,500 ppm Enthalpy: 470 BTU/lb Average elevation in wellfield: 6,900 ft Atmospheric pressure: 11.4 psia Of the 367,000 lb/hr mass flow, approximately 25 percent is steam. Approximately 95 percent of the steam fraction would be lost to the atmosphere. The remainder of the geothermal fluid produced would be injected into the geothermal reservoir. The net loss of geothermal fluid during well testing is shown in Table 3.2.15 for the Construction and Operation phases of the Project. No well testing would occur during Decommissioning. Construction During construction of well pads, blasting may be required at certain locations to achieve a level surface. Although the effects of blasting would not likely travel far within the bedrock of the Project wellfield, it is possible that effects could occur within the shallow aquifer. The effects could alter production of shallow groundwater wells. Since blasting would not be used unless necessary, effects from blasting have a low probability of occurrence. Impact 3.2.3.3-6: Blasting during well pad construction would have a low probability of adversely affecting the production of private water wells. Significance of the Impact: This impact is considered less than significant and no mitigation measures are required, but the following other measure is provided to reduce the adverse effects of the impact. Other Measure 3.2.3.3-6: The blast hole pattern and detonation timing used for any necessary blasting for the Project shall be planned in a manner such that the principal direction of the shock waves from the explosive blast will be directed away from the private water wells in the area. During the construction phase of the proposed Project, geothermal production wells would be drilled and tested. During testing, the net loss of geothermal fluid from the geothermal reservoir would be about 52.6 ac-ft/yr. Subsurface information indicates there is a thick (up to 1,400-foot) unit of hydrothermally altered rhyolite-dacite at the top of the geothermal reservoir, which acts as an impermeable barrier separating the shallow groundwater system from the geothermal system. Therefore, the net loss of fluid from the geothermal reservoir would not have any effect on water quantity in the local shallow groundwater system or the local surface water system, including Medicine Lake or Paynes Springs. It is likely that the geothermal reservoir receives recharge from the deep, regional groundwater system but there is no evidence for the opposite effect — leakage from the geothermal reservoir to the regional groundwater system. The possibility exists that a net loss of fluid volume in the geothermal reservoir would be replaced by water from the deep, regional groundwater system. Since there is no data on whether or not the regional groundwater contributes to flow in the Fall River Springs, it is not known how, or even if, a loss of water from the deep, regional groundwater system would affect flow in the springs. As a worse case scenario, if a net loss of 52.6 ac-ft/yr from the geothermal reservoir caused a loss of 52.6 ac-ft/yr from the regional groundwater system, which in turn caused a loss of 52.6 ac-ft/yr (0.072 cfs) from the Fall River Springs group, the amount of lost flow (0.072 cfs would only be 0.005 percent of the total projected flow (1,421 cfs) from the springs group. Impact 3.2.3.3-7: During the construction phase of the proposed Project, production and injection of geothermal fluids during well testing would result in a net loss of approximately 16,358 lb/hr (0.072 cfs) from the geothermal reservoir. If the geothermal reservoir, the regional groundwater system, and the Fall River Springs are all interconnected, then a maximum net loss of up to 0.072 cfs could occur from the Fall River Springs group, less than 0.005 percent of the projected flow from the Springs group. Significance of the Impact: This impact is considered less than significant and no mitigation measures are required.

Table 3.2.14: Projected Well Test Venting Schedule

Test Duration	Well Test Venting Schedule
30-day venting	15 days at 50%	13 days at 75%	2 days at 100%
15-day venting	7 days at 50%	6 days at 75%	2 days at 100%
90-day resource test	90 days at 75%
3-day work over test	3 days at 75%
Source: Personal Communication — Dave McClain, D.W. McClain & Associates Corp.; December 18, 1997

Table 3.2.15: Net Loss of Geothermal Fluid During Well Testing

Project Time Period	Well Testing Scheduled	Net Loss of Geothermal Fluid
		lbs/hr	gal/yr	ac-ft/yr	cfs
Construction (Year 1)	2 30-day tests 3 15-day tests	16,358	17,149,561	52.6	0.072
Operations (Year 2)	4 15-day tests 1 90-day test	25,671	26,913,549	82.6	0.11
Operations (Year 3-53)	2 15-day tests per year 1 3-day test every 2 yrs	5,046	5,290,022	16.2	0.022
Source: Dave McClain, D.W. McClain & Associates Corp., written communication, December 18, 1997 Assumptions: 367,000 lb/hr mass flow at 100% production 512 ppm NCG 3.6% by wt of NCG = H2S 2500 ppm TDS 470 BTU/lb enthalpy average elevation = 6,900 ft atmospheric pressure = 11.4 psia

Operation During the operation phase of the proposed Project, approximately 3,298,310 lb/hr of geothermal fluids would be produced from production wells and approximately 2,724,116 lb/hr would be injected back into the geothermal reservoir (Weiss 1997). The difference between production volume and injection volume is a net loss of approximately 574,194 lb/hr (2.56 cfs) or 17.4 percent of the fluid mass produced. Additional wells would be drilled and tested during the operations period. Well testing would result in a net loss of 25,671 lb/hr during the first year of operations (the second year of well field development) and 5,046 lb/hr for subsequent years of operations. The maximum loss of geothermal fluid (599,865 lb/hr or 2.67 cfs) would occur during the first year of operations (574,194 lb/hr from production and 25,671 lb/hr from well testing). As a worst case scenario, even if the loss of 599,865 lb/hr (1,942 ac-ft/yr, 2.67 cfs) from the geothermal reservoir caused a loss of 1,942 ac-ft/yr from the regional groundwater system, which in turn caused a loss of 1,942 ac-ft/yr (2.67 cfs) from the Fall River Springs, this maximum amount of lost flow (2.67 cfs) would be only about 0.19 percent (i.e., about one-fifth of one percent) of the total projected flow (1,421 cfs) from the Springs group.

Impact 3.2.3.3-8: During the operation phase of the proposed Project, production and injection of geothermal fluids would result in a net loss of approximately 599,865 lb/hr (2.67 cfs) from the geothermal reservoir. If the geothermal reservoir, the regional groundwater system, and the Fall River Springs group are all hydrologically interconnected, a net loss of up to 2.67 cfs could occur in the springs. Significance of the Impact: This impact is considered less than significant and no mitigation measures are required, but the following other measure is provided to reduce the adverse effects of the impact. Other Measure 3.2.3.3-8: If hydrologic monitoring detects adverse effects to water quantity or quality and these effects can be reasonably demonstrated to have been caused by Project production or injection of geothermal fluids, the Project Applicant shall make appropriate changes to wellfield production and injection operations to remedy the observed adverse effects. Decommissioning During decommissioning of the proposed Project, no geothermal fluids would be produced or injected and there would be no effect on quantity of water in local or regional surface water or groundwater supplies. Effects of Increased Surface Runoff: Construction During the construction phase of the proposed Project, the area of disturbed surface would increase. Most disturbance would decrease infiltration of storm water and increase surface water runoff. Types of disturbance would include removal of vegetation and soils, compaction of soil materials, paving, and construction of buildings. Table 3.2.16 summarizes the areas that could have increased surface water runoff due to alterations in infiltration capacity resulting from Project activities. Grading for construction of the power plant, well pads, transmission line tie-in structures, and roads has the potential to increase erosion of existing channels or create new channels, decrease the amount of surface water infiltration, and increase surface water runoff amounts. Construction activities associated with the proposed Project would use best management practices to minimize impacts. At the power plant and well pads, berms, culverts, and storm drains would be used to prevent water ponding and to direct runoff to natural drainage channels. The accidental creation of new drainage channels would be minimized. In addition to management practices for controlling runoff during construction, surface water runoff quantities would be minimized by the rapid infiltration rates of undisturbed soils in the proposed Project wellfield. The occurrence of surface water runoff is limited to times of high rainfall or high snowmelt rates. Impact 3.2.3.3-9: During the construction phase the area of disturbance would increase. Infiltration of storm water would decrease and surface water runoff would increase, leading to potential increases in erosion and decreases in infiltration of surface water. Significance of the Impact: This impact is considered less than significant and no mitigation measures are required, but the following other measures are provided to reduce the adverse effects of the impact. Other Measure 3.2.3.3-9a: The Project Applicant shall reclaim all disturbed areas that will not be used after completion of the construction phase in conformance with USFS requirements. Other Measure 3.2.3.3-9b: The Project Applicant shall manage excess runoff by temporarily storing runoff fluid in well pad sumps or by injecting it into the geothermal system via injection wells. Operation During the operational phase, storm runoff from the power plant equipment areas and equipment drains would flow to storm drains and injection. Storm runoff from well pads would be channeled into the well pad sumps and then periodically pumped into injection wells for disposal. All other surface water runoff would be the same as during construction, and therefore not significant. Infiltration rates to the shallow aquifer would be reduced due to injection of the diverted water into the geothermal reservoir. The power plant equipment areas and well pads cover a relatively small portion of the total Project wellfield (0.01%).

Table 3.2.16: Maximum Areas of Surface Disturbance Contributing to Potential Increased Surface Water Runoff

Locations of Potential Surface Disturbance	Maximum Area of Disturbance (acres)
	Proposed Action	Alternative Site A	Alternative Site B
Power Plant Site and Well Pads	76.2	77.8	87.9
Wellfield Roads	27.6	27.6	28.4
Pipeline Corridors	69.4	68.2	66.9
Total Wellfield and Power Planta	173.2	173.6	183.2
Transmission Line Segment D1 Option Right-of-Wayb	15.5	19.0	22.8
Transmission Line Segment D2 Option Right-of-Wayb	17.3	11.5	7.3
Alternative Route 1 Right-of-Way (Segments D1 + A2)b	60.0	63.5	67.3
Alternative Route 2 Right-of-Way (Segments D2 + B2*)b	148.6	142.8	138.5
a Assumes all well pads, internal access roads and power plant sites, but it does not include the transmission line right-of-way b Assumes 100-foot right-of-way

Impact 3.2.3.3-10: During the operation phase, recharge to the shallow aquifer would be reduced due to injection of surface water runoff into the geothermal reservoir. Significance of the Impact: This impact is considered less than significant and no mitigation measures are required, but the following other measure is provided to reduce the adverse effects of the impact. Other Measure 3.2.3.3-10: The Project Applicant shall place drains or energy dissipaters at intervals along new roads to allow runoff to exit the roadbed and percolate into native soils. Decommissioning During decommissioning all Project facilities would be dismantled. All disturbed areas would be reseeded and re-contoured approximately to pre-Project topography where necessary and as directed by the USFS. These activities would reduce surface runoff and therefore would have a beneficial effect. Effects of Flooding: Construction Surface disturbance during construction activities such as grading could result in minor changes in surface water drainage patterns. Construction of Project facilities and access roads would include the use of culverts and berms to direct drainage and avoid localized flooding. These measures, along with the high permeability of soils in the Project wellfield would ensure that no localized flooding would occur. No construction activities for the proposed Project would occur within a 100-year flood plain, and there would be no impact on people or property from flooding as a result of the construction phase of the proposed Project. Operation During the operation phase, Project activities would not affect drainage or flooding patterns. Minor changes in surface drainage patterns created during construction would continue through the operational phase. As described above, these changes would not result in localized flooding. There would be no impact on people or property from flooding as a result of the operation phase of the proposed Project.

Decommissioning During decommissioning, the Project wellfield would be returned to pre-Project conditions as much as possible. These activities would return some surface drainages to their original state and would not result in any localized flooding. There would be no impact on people or property from flooding as a result of decommissioning the proposed Project. Effects of Geothermal Drilling, Production, and Injection on Water Quality: Construction During construction, drilling operations are not expected to have an adverse effect on water quality. Drilling fluids are used to lubricate the drill bit, stabilize the hole, and remove drill cuttings. When the drill bit hits permeable rocks drilling fluids may be lost to the rock formation. Excessive loss of fluids could result in localized changes to water quality. These changes would be adverse, but the proposed drilling fluids would be composed of non-toxic constituents that would cause minimal water quality degradation. Impact 3.2.3.3-11: During drilling operations, drilling fluids may be lost to the rock formation when the drill bit encounters permeable rocks. Significance of the Impact: This impact is considered less than significant and no mitigation measures are required. During drilling, liquid wastes that are returned from the drill column include water, non-toxic drilling additives, rock cuttings, and once the geothermal reservoir is intercepted – geothermal fluid. These liquid wastes would be directed to the well pad sump and could potentially leak from the sumps, infiltrate to the shallow groundwater and degrade the quality of the groundwater. The sumps would be constructed and maintained to have a permeability of less than 10-6 cm/sec. Each liquid-holding sump would have a capacity adequate to hold the expected volumes of fluids to be produced during short-term flow tests and well start-up and work over operations. Bentonite is a common drilling mud additive which would provide additional clay to the liner of the sumps and further reduce the potential for leakage from the sumps. For these reasons, it is unlikely that substantial leakage would occur from the well pad sumps to the shallow aquifer. Impact 3.2.3.3-12: During drilling, liquid wastes from drilling operations would be directed to the well pad sumps and could potentially leak from the sumps and degrade the shallow groundwater. Significance of the Impact: This impact is considered less than significant and no mitigation measures are required. During drilling of wells, there is a potential that geothermal fluids could enter the wellbore and mix with shallow groundwater before casing is installed. The likelihood of this would be reduced by proper well construction technique. Similarly, during drilling, drilling mud or geothermal fluids could accidently be spilled into intermittent surface water drainages if a well blowout were to occur. The use of blowout prevention equipment on wellheads during drilling would reduce the likelihood of blowouts occurring. The Project wells would be designed and constructed in conformance with Geothermal Resource Operational Order No. 2, applicable to well drilling and completion requirements, and approved by the BLM before the Project wells are drilled. Conformance with applicable well drilling and completion requirements would prevent mixing of the geothermal fluids with the shallow groundwater and keep the wells under control preventing well blowouts. These potentially adverse effects are not anticipated from the Project. Operation During the operation phase, impacts to water quality of surface water or groundwater in the shallow aquifer would not be expected during normal production and injection practices. The injected fluids would be released to the geothermal reservoir, which is not connected to the shallow groundwater system. However, impacts could occur during the operation phase due to mixing of the geothermal fluid in the shallow groundwater aquifer through damaged well casings or accidental discharge of geothermal fluids to the surface. Proper construction techniques for production and geothermal wells including cementing and sealing the casing would prevent mixing of geothermal and shallow aquifer water. Effects to local water quality could occur if the well casings failed. These effects would not be significant due to the localized nature and low probability of occurrence. Accidental discharge of geothermal liquids to surface drainages could occur due to blowouts during drilling, leaking piping or wellheads, and overflow from well sumps. The closest perennial water bodies to the proposed Project wellfield are Medicine Lake, Paynes Springs, Blanche Lake, and Bullseye Lake. Of these, only Paynes Springs is directly downgradient for surface water drainage from the Project. However, because the infiltration rate of soils in the Project wellfield is moderate to very rapid, it is likely that accidental discharges would percolate into the subsurface and would be absorbed in the unsaturated zone before reaching the shallow groundwater or Paynes Springs. Any breaks causing accidental discharges would be repaired immediately reducing the likelihood that any discharge water would reach Paynes Springs. Therefore, there is only a small, but finite, potential that an accidental discharge of geothermal fluid from the Project operations would affect local surface water or groundwater quality.

Impact 3.2.3.3-13: Mixing of the geothermal fluid in the shallow groundwater aquifer could occur due to damaged well casings or accidental discharge of geothermal fluids to the surface. There is only a small potential that an accidental discharge of geothermal fluids would affect local surface water or groundwater quality. Significance of the Impact: The potential for this impact is considered less than significant and no mitigation measures are required, but the following other measure is provided to reduce the potential for adverse effects of the impact. Other Measure 3.2.3.3-13: The Project Applicant shall prepare an Emergency Release Contingency Plan which defines the control and restoration measures to be implemented in the event of a well blowout, sump overflow, or pipeline rupture. Regionally, surface water flows south from Medicine Lake Basin and groundwater flows radially out from Medicine Lake Highlands and then south. In the proposed Project wellfield, groundwater flows to the southeast. Due to these regional flow constraints, no impacts to regional surface water or groundwater quality would be expected to the west, north, or east of the proposed Project wellfield. Due to the moderate to very rapid infiltration rates in the porous volcanic soils in the Medicine Lake Highlands, it is very unlikely that any surface discharge would leave the local area before infiltrating. If impacts to the water quality of the shallow aquifer from the proposed geothermal development do occur, there could potentially be impacts to groundwater and/or springs to the south of Medicine Lake Highlands. As discussed above, the flow volumes at the Fall River Springs group require that the entire area encompassing Medicine Lake Volcano and the Giant Crater lava field must have enhanced permeability (fractures and lava tubes) that promotes the recharge of most of the annual precipitation and focuses groundwater transport south to the Fall River Springs. Because the recharge to the springs comes from such a large geographic area, any impacts to water quality of the local shallow groundwater in the proposed Project wellfield would be diluted during mixing with regional recharge water, ensuring that any affects on water quality to the Fall River Springs group would unlikely be detectable above natural variation in water quality. Groundwater modeling completed by the Hydrodynamics Group (1997b) supports the idea that dilution would occur. The Hydrodynamics Group model showed that a hypothetical contaminant introduced into the groundwater in the Medicine Lake area would move to the Fall River Springs area quickly, but it would be diluted to 3 percent or less of initial concentration. Decommissioning During decommissioning, no drilling, production, or injection activities would occur and no other activities that could potentially degrade water quality would occur. Therefore, the decommissioning phase would not affect surface water or groundwater quality. Effects of Air Emissions on Water Quality: Construction, Operation, and Decommissioning During construction of the proposed Project, fugitive dust would be generated by construction and drilling activities. The prevailing wind direction at Medicine Lake is from the southwest (USFS 1991, USFS 1994). Fugitive dust would migrate downwind from the Project site to the northeast. The closest perennial surface water features to the northeast of the proposed Project site are several streams more than 10 miles away, and Clear Lake Reservoir more than 20 miles away. Fugitive dust would be expected to settle out of the atmosphere before reaching any of these water bodies. Therefore, no adverse effects on surface water from dust deposition from power plant and well field construction are expected. Well testing emissions (steam and water droplets) would be short-term and would fall out on and near the well pads. Therefore, well testing is unlikely to cause water quality effects. During the operational phase of the proposed Project, air emissions would be released from the cooling tower and plant silencers. These emissions would include gases such as water vapor and noncondensable gases, and water droplets. The water droplets would contain dissolved and suspended solids, including trace amounts of heavy metals. The largest droplets would fall to the ground close to the power plant and cooling tower where they are produced. The smallest droplets could evaporate, causing the suspended and dissolved solids they contain to form aerosol particles which would be dispersed over a wide area (see Section 3.4).

The potential for air emissions to affect the quality of water at nearby lakes would be a function of lake distance from the power plant, the composition of the transported material, and the frequency of the wind blowing in the direction of the lakes. The closest perennial lakes to the Telephone Flat Geothermal Project wellfield are Bullseye Lake and Blanche Lake approximately 1¼ miles (2.01 km) southwest of the proposed power plant site and Medicine Lake approximately 1½ miles (2.4 km) west-northwest of the proposed power plant site. Most deposition of particles from air emissions from power plant cooling towers occurs within 1,640 feet (500 m) of the cooling tower (Houck 1997c; provided as Appendix J and clarified by Appendix O). No perennial lakes occur within 1,640 feet (500 m) of the proposed power plant site. The prevailing wind in the Project vicinity is out of the northwest with an average wind speed of 3.4 mph (1.5 m/s) (Houck 1997c) making the likelihood of deposition in Medicine Lake very small. The likelihood of deposition in Blanche and Bullseye lakes would also be low due to the prevailing northwesterly wind direction. Based on computer modeling, the chemical composition of water droplets resulting from cooling tower air emissions is expected to be 800 ppm salts (80% sodium chloride, 20% sodium sulfate), 3 ppm boron, with trace amounts of arsenic, mercury, biocide, and biodispersant (Houck 1997c). The deposition rate of boron at a distance of 1,188 ft (362 m) from the cooling tower is predicted to be 0.14 lbs/acre/yr, which is well below the rate of 60 lbs/acre/yr that is known to cause vegetation stress (Houck 1997c). The constituents that occur in trace amounts would not have high enough concentrations to impact water quality. For instance, the average background atmospheric mercury level is about three times higher than the maximum mercury level predicted from air emissions. However, because mercury can bioaccumulate in fish providing the primary exposure pathway for humans, and because Medicine and Bullseye lakes are heavily used for recreational fishing, computer modeling was completed to predict the mercury concentrations in the water in Medicine and Bullseye Lakes (Houck and Phillips 1997f; provided as Appendix N and clarified by Appendix O). The modeling showed that even assuming higher mercury concentrations in air emissions than expected, concentrations of mercury would be only 2.2×10-6 mg/l in Medicine Lake and 2.8×10-6 mg/l in Bullseye Lake. These concentrations would be approximately 1000 times lower than the California primary drinking water standard of 2.0×10-3 mg/l for mercury (22 CCR §64431 et seq.) and would also be lower than the EPA recommended criteria (1.2×10-5 mg/l) for the protection of freshwater aquatic life. The conservative assumptions used in the mercury deposition modeling were subsequently re-evaluated by Houck in a more refined assessment of the projected deposition of mercury from the proposed Project and the impact on the lakes in the vicinity of the Project (see Appendix P). The refined assessment resulted in a lower estimated increase in the mercury concentrations of Medicine Lake and Bullseye Lake of 0.03 parts per trillion (3.0×10-8 mg/l) and 0.02 parts per trillion (2.0×10-8 mg/l), respectively (Houck 1998). Thus, the modeling results show that air emissions from the proposed Telephone Flat Geothermal Project would have a negligible effect on mercury concentrations in the water of Medicine and Bullseye Lakes (Houck and Phillips 1997f). During decommissioning activities fugitive dust would result from vehicles and equipment used to remove facilities and undertake site reclamation. For the same reasons as described for the construction phase, there would be a negligible potential for adverse effects on water quality from air emissions during decommissioning. Effects of Sanitary Waste on Water Quality: Construction, Operation, and Decommissioning During the construction phase of the proposed Project, portable toilets would be installed near where crews are working throughout the plant site, along the pipeline route, and along the transmission line corridor. Sanitary wastes from the toilets would be pumped by a licensed commercial septic tank pumping service and disposed of at an appropriate off-site location. There would be no impacts to local or regional groundwater or surface water quality from sanitary wastes during the construction phase of the Project. During the operation phase, the power plant would have a sanitary system consisting of a septic system for 12 people in an 8-hour shift. The outflow from the septic tank would drain to an underground leach field. The leach field would be constructed and the septic tank would be maintained according to accepted standards. Depth to groundwater at each of the Project Alternative power plant sites is projected to exceed 300 feet below the surface. Therefore, there would be no impacts to local or regional groundwater or surface water quality from sanitary wastes during the operation phase of the Project.

During decommissioning, the septic system at the power plant would continue to be maintained and used. In addition, portable toilets would be placed around the Project wellfield and transmission lines as needed in the locations of work crews. For the same reasons as discussed under the construction and operation phases, there would be no impacts to local or regional groundwater or surface water quality from sanitary wastes during decommissioning of the proposed Project. Effects of Chemical and Hazardous Material Spills on Water Quality: Construction, Operation, and Decommissioning During all phases of the Proposed Action, potentially hazardous materials would be used and stored on-site including diesel fuel, lubricating fluids, anti-scaling and anti-corrosion chemicals, sulfuric acid, hydrochloric acid, liquid propane, inhibited insulating mineral oil, and various maintenance and cleaning supplies (paints, oils, solvents, and cleaning compounds). All fluids used in drilling would be formulated from non-toxic components as defined by the EPA. The storage, dispensing, and use of hazardous material would be in accordance with the applicable county, state, and federal guidelines. All tanks containing potentially hazardous materials would be constructed above ground and would include secondary containment such as a bermed area draining to a sump equipped with a low point valve that would normally be closed. The secondary containment would have a capacity equal to 100-150 percent of the total tank capacity. Spilled material would be confined within the secondary containment until collection and disposal at the appropriate facility. Precipitation normally falling and collecting in the secondary containment, if uncontaminated, would be directed to one of the well pad sumps for eventual injection into the geothermal reservoir. For the reasons stated above, adverse effects to water quality are not likely from the storage, dispensing, and use of hazardous materials by the Project. The guidelines governing their storage, dispensing, and use would reduce the likelihood of a spill which could potentially impact water quality of surface water or the shallow aquifer. Because of planned control practices, spills of chemical or hazardous materials are not expected to affect surface water or groundwater quality. Effects on Regional Thermal Features: Construction, Operation, and Decommissioning Compared to the total volume of the geothermal reservoir, only a small amount of geothermal fluid (16,358 lbs/hr or 0.072 cfs) would be removed from the reservoir during the construction phase. Withdrawal of this small portion of the reservoir would not affect any local or regional geothermal feature. Operation of the proposed Project would involve a net loss of 599,865 lb/hr (2.67 cfs) of geothermal fluids in the reservoir and would include injection of spent fluids at reduced temperatures back into the reservoir. These activities could potentially affect any other thermal features that share the same geothermal reservoir. The only known surface thermal feature in the Medicine Lake Highlands is the Hot Spot which is located on the northwest flank of Glass Mountain. The Hot Spot is not considered a significant thermal feature. It was earlier thought to be a pair of fumarole vents that emit gases heated by the geothermal resource in the KGRA. However, more recent information indicates the Hot Spot is not connected to the geothermal system but exists as a result of meteoric water seeping into the earth and being heated in a zone of shallow hot rock. This theory is consistent with the findings of a recent analysis of gases sampled from the fumarole. The Hot Spot gas sample contained only about one percent carbon dioxide, much less than would be expected from a geothermal vent in the area, and was predominantly water vapor and heated air (Personal Communication—Robert H. Mariner, USGS; March 6, 1998). As the Hot Spot is not believed to be directly connected to the geothermal system, there should be no effect on the fumarolic-like emissions observed at the Hot Spot as a result of Project activities. Another thermal feature within the region surrounding Medicine Lake Highlands is Little Hot Springs which is located approximately 25 miles southeast of Medicine Lake at the southeastern edge of the Whitehorse Mountains. These springs occur along northwest-southeast trending Basin and Range style faulting (Leivas et al. 1981) and are not related to the Glass Mountain KGRA geothermal system. Therefore, Little Hot Springs would not be affected by the Project.

During decommissioning, no geothermal fluids would be withdrawn from the geothermal reservoir. Therefore there would be no effect on local or regional thermal features. Effects of Geothermal Development on Geothermal Resource Depletion: “Geothermal resources” means the natural heat of the earth, and it is classified as a renewable energy resource by statute (National Energy Policy Act of 1992, Title XII; Pacific Northwest Electric Power Planning and Conservation Act of 1980, ((P.L. 96-501) §3(16)). The geothermal fluids that would be produced through the Project wells would be the means by which this heat energy would be extracted from the earth and delivered to the power plant to be converted to electricity. Typically, nearly all of the heat in a geothermal reservoir is contained in the rock, with comparatively little contained in the geothermal fluid, and the Glass Mountain KGRA reservoir is presumed to be no different. Although the Project would remove and consume some heat energy from the geothermal reservoir, the heat energy in the rock in the geothermal reservoir is enormous, and the total heat energy in the Medicine Lake volcano area is essentially inexhaustible in practical terms. However, how quickly the spent fluids injected back into the geothermal reservoir, and other fluids that may flow into the geothermal reservoir, would be able move through, and extract sufficient heat from, the rock that could then be produced and used by the Project or future geothermal projects cannot be estimated with any degree of confidence from the information currently available. In an optimum situation, the proposed geothermal operations would reach essentially a steady state where the rate of production of heat from the geothermal reservoir through the wells would equal the rate at which the geothermal fluids could extract heat from the geothermal reservoir, that would also equal the rate at which heat from the surrounding rock would enter the geothermal reservoir. However, geothermal resource production and utilization operations in other areas suggest that it is likely that the rate of geothermal heat production from the geothermal reservoir would exceed the rate at which the fluids would be able to extract more heat from the rock. Thus, the temperature of the produced geothermal fluids would slowly decrease over time until the continued commercial operation of the Project is no longer economically viable, and the Project would typically discontinue operations and move to the decommissioning phase. CEGC believes that at the proposed rate of geothermal heat production, the geothermal reservoir would be able to support Project operations for at least 50 years. Over an extended period of time following the end of Project operations, perhaps as long as several hundred years, the remaining heat in the geothermal reservoir rock, as well as the magmatic heat from the Medicine Lake volcano area, would “renew” the geothermal system into a commercially suitable geothermal resource. The temporary “depletion” of the commercially viable geothermal resource in the Project geothermal reservoir and wellfield would not be expected to have any substantive effect on the regional geothermal resources, but may somewhat limit the quantity of commercial geothermal resources that could be produced from neighboring geothermal leases.

3.2.3.3.2 Unavoidable Adverse Effects of the Proposed Action

After implementation of other measures to reduce the adverse effects of the proposed Project, unavoidable adverse effects of the Proposed Action on hydrologic and geothermal resources would include a maximum net loss of approximately 599,865 lb/hr (2.67 cfs) of geothermal fluid from the geothermal reservoir; a maximum use of 16.2 million gallons per year (49.8 ac-ft/yr) of water from the shallow aquifer; and an increase in surface water runoff from surface compacted areas and areas with reduced vegetation.

3.2.3.4 Alternative Power Plant Site A

The Alternative Power Plant Site A Project Alternative is approximately the same as the Proposed Action except that the power plant location is farther east. The effects of the Alternative Site A project on hydrologic and geothermal resources would be about the same as for the Proposed Action. There would be less than a 1 percent increase in the maximum area of surface disturbance in the wellfield resulting from the Alternative Site A Project Alternative compared to the Proposed Action. The discussion of the effects of the Proposed Action is brought forward to this section by reference. The following is a list of the impacts, statement of significance, and relevant mitigation or other measures numbered to reflect this Project Alternative. Impact 3.2.3.4-1: Construction and construction-related activities would consume approximately 15.3-24.5 ac-ft/yr of groundwater from the shallow aquifer for dust abatement and up to 4.6 ac-ft/yr for fire protection and domestic uses. Significance of the Impact: This impact is considered less than significant and no mitigation measures are required. Impact 3.2.3.4-2: Geothermal well drilling operations for the Project would consume approximately 20.6 acre-ft of groundwater during the first year of construction and lesser amounts in subsequent construction or well drilling years. Significance of the Impact: This impact is considered less than significant and no mitigation measures are required. Impact 3.2.3.4-3: The combined total of groundwater consumption for geothermal well drilling operations and construction-related uses for the Project would be about 49.8 ac-ft/yr during the first year of construction and lesser amounts in subsequent construction or well drilling years. Significance of the Impact: This impact is considered less than significant and no mitigation measures are required, but the following other measure are provided to reduce the adverse effects of the impact. Other Measure 3.2.3.4-3a: The Project Applicant, CEGC, has submitted a proposed hydrology monitoring plan to the BLM. The Project Applicant shall implement the approved monitoring plan in coordination with hydrologic monitoring which may be required for the proposed Fourmile Hill Geothermal Project and in conformance with the monitoring requirements of the BLM and USFS. The proposed hydrology monitoring plan includes, but is not limited to the following: Collection of baseline water level and water quality data; Monitoring of water levels in wells; Monitoring lake stages; and Monitoring well, spring, and lake water quality. Other Measure 3.2.3.4-3b: Groundwater pumping rates shall be reduced if monitoring detects potentially significant adverse effects to water availability, and these effects can be attributed to Project pumping of local groundwater. Other Measure 3.2.3.4-3c: In the event that damage to private groundwater well(s) can be reasonably attributed to excessive pumping of the shallow groundwater by the Project, Project Applicant shall repair the damage to the private well(s) and modify Project operations to prevent further well damage. Impact 3.2.3.4-4: The Project would consume approximately 6.5 ac-ft/yr of groundwater from the shallow aquifer during the operations phase. Significance of the Impact: This impact is considered less than significant and no mitigation measures are required, but the following other measure is provided to reduce the adverse effects of the impact. Other Measure 3.2.3.4-4: When feasible, geothermal production water would be used to meet well drilling water requirements, thus reducing the amount of water required from the shallow aquifer. Impact 3.2.3.4-5: Domestic water use during decommissioning would consume approximately 4.0 ac-ft/yr from the shallow aquifer. Significance of the Impact: This impact is considered less than significant and no mitigation measures are required. Impact 3.2.3.4-6: Blasting during well pad construction would have a low probability of adversely affecting the production of private water wells. Significance of the Impact: This impact is considered less than significant and no mitigation measures are required, but the following other measure is provided to reduce the adverse effects of the impact. Other Measure 3.2.3.4-6: The blast hole pattern and detonation timing used for any necessary blasting for the Project shall be planned in a manner such that the principal direction of the shock waves from the explosive blast will be directed away from the private water wells in the area.

Impact 3.2.3.4-7: During the construction phase of the proposed Project, production and injection of geothermal fluids during well testing would result in a net loss of approximately 16,358 lb/hr (0.072 cfs) from the geothermal reservoir. If the geothermal reservoir, the regional groundwater system, and the Fall River Springs are all interconnected, then a maximum net loss of up to 0.072 cfs could occur from the Fall River Springs group, less than 0.005 percent of the projected flow from the Springs group. Significance of the Impact: This impact is considered less than significant and no mitigation measures are required. Impact 3.2.3.4-8: During the operation phase of the proposed Project, production and injection of geothermal fluids would result in a net loss of approximately 599,865 lb/hr (2.67 cfs) from the geothermal reservoir. If the geothermal reservoir, the regional groundwater system, and the Fall River Springs group are all hydrologically interconnected, a net loss of up to 2.67 cfs could occur in the springs. Significance of the Impact: This impact is considered less than significant and no mitigation measures are required, but the following other measure is provided to reduce the adverse effects of the impact. Other Measure 3.2.3.4-8: If hydrologic monitoring detects adverse effects to water quantity or quality and these effects can be reasonably demonstrated to have been caused by Project production or injection of geothermal fluids, the Project Applicant shall make appropriate changes to wellfield production and injection operations to remedy the observed adverse effects. Impact 3.2.3.4-9: During the construction phase the area of disturbance would increase. Infiltration of storm water would decrease and surface water runoff would increase, leading to potential increases in erosion and decreases in infiltration of surface water. Significance of the Impact: This impact is considered less than significant and no mitigation measures are required, but the following other measures are provided to reduce the adverse effects of the impact. Other Measure 3.2.3.4-9a: The Project Applicant shall reclaim all disturbed areas that will not be used after completion of the construction phase in conformance with USFS requirements. Other Measure 3.2.3.4-9b: The Project Applicant shall manage excess runoff by temporarily storing runoff fluid in well pad sumps or by injecting it into the geothermal system via injection wells. Impact 3.2.3.4-10: During the operation phase, recharge to the shallow aquifer would be reduced due to injection of surface water runoff into the geothermal reservoir. Significance of the Impact: This impact is considered less than significant and no mitigation measures are required, but the following other measure is provided to reduce the adverse effects of the impact. Other Measure 3.2.3.4-10: The Project Applicant shall place drains or energy dissipaters at intervals along new roads to allow runoff to exit the roadbed and percolate into native soils. Impact 3.2.3.4-11: During drilling operations, drilling fluids may be lost to the rock formation when the drill bit encounters permeable rocks. Significance of the Impact: This impact is considered less than significant and no mitigation measures are required. Impact 3.2.3.4-12: During drilling, liquid wastes from drilling operations would be directed to the well pad sumps and could potentially leak from the sumps and degrade the shallow groundwater. Significance of the Impact: This impact is considered less than significant and no mitigation measures are required. Impact 3.2.3.4-13: Mixing of the geothermal fluid in the shallow groundwater aquifer could occur due to damaged well casings or accidental discharge of geothermal fluids to the surface. There is only a small potential that an accidental discharge of geothermal fluids would affect local surface water or groundwater quality.

Significance of the Impact: The potential for this impact is considered less than significant and no mitigation measures are required, but the following other measure is provided to reduce the potential for adverse effects of the impact. Other Measure 3.2.3.4-13: The Project Applicant shall prepare an Emergency Release Contingency Plan which defines the control and restoration measures to be implemented in the event of a well blowout, sump overflow, or pipeline rupture.

3.2.3.4.1 Unavoidable Adverse Effects of Alternative Power Plant Site A

After implementation of other measures to reduce the adverse effects of the proposed Project, unavoidable adverse effects of Alternative Site A on hydrologic and geothermal resources would include a maximum net loss of approximately 599,865 lb/hr (2.67 cfs) of geothermal fluid from the geothermal reservoir; a maximum use of 16.2 million gallons per year (49.8 ac-ft/yr) of water from the shallow aquifer; and an increase in surface water runoff from surface compacted areas and areas with reduced vegetation.

3.2.3.5 Alternative Power Plant Site B

The Alternative Power Plant Site B Project Alternative is approximately the same as the Proposed Action except that the power plant location is farther east. However, Alternative Site B is expected to require an approximately 30 percent increase in the number of wells, and a projected 30 percent increase in geothermal fluid produced, over the life of the Project to support the parasitic power losses resulting from increased distance of the power plant site from the production wellfield. In addition, there would be about a 9 percent increase in the maximum total area of surface disturbance expected in the wellfield area over the life of the Alternative Site B Project Alternative compared to the Proposed Action. The effects of the Alternative Site B project on hydrologic and geothermal resources would be about the same as for the Proposed Action. The discussion of the effects of the Proposed Action is brought forward to this section by reference. The following is a list of the impacts, statement of significance, and relevant mitigation or other measures numbered to reflect this Project Alternative. Impact 3.2.3.5-1: Construction and construction-related activities would consume approximately 15.3-24.5 ac-ft/yr of groundwater from the shallow aquifer for dust abatement and up to 4.6 ac-ft/yr for fire protection and domestic uses. Significance of the Impact: This impact is considered less than significant and no mitigation measures are required. Impact 3.2.3.5-2: Geothermal well drilling operations for the Project would consume approximately 20.6 acre-ft of groundwater during the first year of construction and lesser amounts in subsequent construction or well drilling years. Significance of the Impact: This impact is considered less than significant and no mitigation measures are required. Impact 3.2.3.5-3: The combined total of groundwater consumption for geothermal well drilling operations and construction-related uses for the Project would be about 49.8 ac-ft/yr during the first year of construction and lesser amounts in subsequent construction or well drilling years. Significance of the Impact: This impact is considered less than significant and no mitigation measures are required, but the following other measure are provided to reduce the adverse effects of the impact. Other Measure 3.2.3.5-3a: The Project Applicant, CEGC, has submitted a proposed hydrology monitoring plan to the BLM. The Project Applicant shall implement the approved monitoring plan in coordination with hydrologic monitoring which may be required for the proposed Fourmile Hill Geothermal Project and in conformance with the monitoring requirements of the BLM and USFS. The proposed hydrology monitoring plan includes, but is not limited to the following: Collection of baseline water level and water quality data; Monitoring of water levels in wells; Monitoring lake stages; and Monitoring well, spring, and lake water quality. Other Measure 3.2.3.5-3b: Groundwater pumping rates shall be reduced if monitoring detects potentially significant adverse effects to water availability, and these effects can be attributed to Project pumping of local groundwater.

Other Measure 3.2.3.5-3c: In the event that damage to private groundwater well(s) can be reasonably attributed to excessive pumping of the shallow groundwater by the Project, Project Applicant shall repair the damage to the private well(s) and modify Project operations to prevent further well damage. Impact 3.2.3.5-4: The Project would consume approximately 6.5 ac-ft/yr of groundwater from the shallow aquifer during the operations phase. Significance of the Impact: This impact is considered less than significant and no mitigation measures are required, but the following other measure is provided to reduce the adverse effects of the impact. Other Measure 3.2.3.5-4: When feasible, geothermal production water would be used to meet well drilling water requirements, thus reducing the amount of water required from the shallow aquifer. Impact 3.2.3.5-5: Domestic water use during decommissioning would consume approximately 4.0 ac-ft/yr from the shallow aquifer. Significance of the Impact: This impact is considered less than significant and no mitigation measures are required. Impact 3.2.3.5-6: Blasting during well pad construction would have a low probability of adversely affecting the production of private water wells. Significance of the Impact: This impact is considered less than significant and no mitigation measures are required, but the following other measure is provided to reduce the adverse effects of the impact. Other Measure 3.2.3.5-6: The blast hole pattern and detonation timing used for any necessary blasting for the Project shall be planned in a manner such that the principal direction of the shock waves from the explosive blast will be directed away from the private water wells in the area. Impact 3.2.3.5-7: During the construction phase of the proposed Project, production and injection of geothermal fluids during well testing would result in a net loss of approximately 16,358 lb/hr (0.072 cfs) from the geothermal reservoir. If the geothermal reservoir, the regional groundwater system, and the Fall River Springs are all interconnected, then a maximum net loss of up to 0.072 cfs could occur from the Fall River Springs group, less than 0.005 percent of the projected flow from the Springs group. Significance of the Impact: This impact is considered less than significant and no mitigation measures are required. Impact 3.2.3.5-8: During the operation phase of the proposed Project, production and injection of geothermal fluids would result in a net loss of approximately 779,825 lb/hr (3.47 cfs) from the geothermal reservoir. If the geothermal reservoir, the regional groundwater system, and the Fall River Springs group are all hydrologically interconnected, a net loss of up to 3.47 cfs could occur in the springs. Significance of the Impact: This impact is considered less than significant and no mitigation measures are required, but the following other measure is provided to reduce the adverse effects of the impact. Other Measure 3.2.3.5-8: If hydrologic monitoring detects adverse effects to water quantity or quality and these effects can be reasonably demonstrated to have been caused by Project production or injection of geothermal fluids, the Project Applicant shall make appropriate changes to wellfield production and injection operations to remedy the observed adverse effects. Impact 3.2.3.5-9: During the construction phase the area of disturbance would increase. Infiltration of storm water would decrease and surface water runoff would increase, leading to potential increases in erosion and decreases in infiltration of surface water. Significance of the Impact: This impact is considered less than significant and no mitigation measures are required, but the following other measures are provided to reduce the adverse effects of the impact.

Other Measure 3.2.3.5-9a: The Project Applicant shall reclaim all disturbed areas that will not be used after completion of the construction phase in conformance with USFS requirements. Other Measure 3.2.3.5-9b: The Project Applicant shall manage excess runoff by temporarily storing runoff fluid in well pad sumps or by injecting it into the geothermal system via injection wells. Impact 3.2.3.5-10: During the operation phase, recharge to the shallow aquifer would be reduced due to injection of surface water runoff into the geothermal reservoir. Significance of the Impact: This impact is considered less than significant and no mitigation measures are required, but the following other measure is provided to reduce the adverse effects of the impact. Other Measure 3.2.3.5-10: The Project Applicant shall place drains or energy dissipaters at intervals along new roads to allow runoff to exit the roadbed and percolate into native soils. Impact 3.2.3.5-11: During drilling operations, drilling fluids may be lost to the rock formation when the drill bit encounters permeable rocks. Significance of the Impact: This impact is considered less than significant and no mitigation measures are required. Impact 3.2.3.5-12: During drilling, liquid wastes from drilling operations would be directed to the well pad sumps and could potentially leak from the sumps and degrade the shallow groundwater. Significance of the Impact: This impact is considered less than significant and no mitigation measures are required. Impact 3.2.3.5-13: Mixing of the geothermal fluid in the shallow groundwater aquifer could occur due to damaged well casings or accidental discharge of geothermal fluids to the surface. There is only a small potential that an accidental discharge of geothermal fluids would affect local surface water or groundwater quality. Significance of the Impact: The potential for this impact is considered less than significant and no mitigation measures are required, but the following other measure is provided to reduce the potential for adverse effects of the impact. Other Measure 3.2.3.5-13: The Project Applicant shall prepare an Emergency Release Contingency Plan which defines the control and restoration measures to be implemented in the event of a well blowout, sump overflow, or pipeline rupture.

3.2.3.5.1 Unavoidable Adverse Effects of Alternative Power Plant Site B

After implementation of other measures to reduce the adverse effects of the proposed Project, unavoidable adverse effects of Alternative Site B on hydrologic and geothermal resources would include a maximum net loss of approximately 779,825 lb/hr (3.47 cfs) of geothermal fluid from the geothermal reservoir; a maximum use of 16.2 million gallons per year (49.8 ac-ft/yr) of water from the shallow aquifer; and an increase in surface water runoff from surface compacted areas and areas with reduced vegetation.

3.2.3.6 Alternative Transmission Line Routes

Previous Transmission Line Impact Assessment: As discussed in Section 2.2.5, the transmission line originating at the Telephone Flat Project power plant site would be routed to interconnect with a transmission line located within one of the six alternative utility corridors evaluated in the Fourmile Hill Project EIS/EIR to be selected by the agencies as the preferred utility corridor between the Medicine Lake Highlands and the existing BPA Malin-Warner transmission line (BLM et al. 1998). The Fourmile Hill Project EIS/EIR evaluated seven different possible line segments (segments A1, A2, A3, B1, B2, C1 and C2) which could be used in different combinations to comprise the preferred utility corridor. Only five of these line segments (A2, B1, B2, C1 and C2) could possibly be used by the Telephone Flat Project, and the Hydrologic and Geothermal Resources analysis from the Fourmile Hill Project EIS/EIR of the five line segments which could be potentially used by the Telephone Flat Project are incorporated by reference into this EIS/EIR (see pages 3-14 through 3-51, and 4-19 through 4-50 of the Fourmile Hill Project EIS/EIR; BLM et al. 1998). The findings of the earlier assessment are also summarized in Exhibit 4 of this EIS/EIR (See Table S-5, pages S-30 to S-36, in Exhibit 4). Telephone Flat Project Route Alternatives:

If the agencies select one of the Fourmile Hill Project utility corridor alternatives which route through the Medicine Lake basin in close proximity to the Telephone Flat Project (i.e., Alternatives 1 through 4), then the Telephone Flat Project would construct either line segment D1 (if Alternatives 1 or 2 is selected) or line segment D2 (if Alternatives 3 or 4 is selected), and no specific agency decision on transmission line route alternatives would need to be made for the Telephone Flat Project. However, if the Northern Utility Corridor for the Fourmile Hill Project (i.e., Alternatives 5 or 6) is selected as the agency-preferred utility corridor, then a second decision for the Telephone Flat Project would need to be made with respect to how to interconnect the Telephone Flat Project transmission line with the Northern Utility Corridor. Two alternative Telephone Flat Project transmission line routes (Route 1 and Route 2) are being considered for transporting power generated from the Telephone Flat Project power plant site to the Northern Utility Corridor.

3.2.3.6.1 Environmental Consequences of Route 1 (Line Segments D1 + A2)

The Telephone Flat Project Alternative Transmission Line Route 1 (4.95-5.55 miles) consists of an initial 1.28- to 1.88-mile line segment D1 and a 3.67-mile utility corridor line segment A2. Line segment D1 proceeds northward from the Telephone Flat Project power plant site and joins the origin of line segment A2 at the western tip of Glass Mountain. Line segment A2 proceeds northeast from this point until it joins the Northern Utility Corridor at the origin of line segment B1 south of Indian Butte. Line Segment D1: There are no perennial surface water resources within the right-of-way planning corridors for line segment D1. A surface depression exists north of Alcohol Crater in which water is seasonally ponded, but the D1 planning corridor does not go through this area. Construction, operation and decommissioning of the initial transmission line interconnection segment D1 from any of the three power plant site alternatives would not be expected to have any adverse effects on water quality or quantity. Line Segment A2: Line segment A2 was the subject of earlier environmental analysis as part of the Fourmile Hill Project EIS/EIR (BLM et al. 1998). That analysis is incorporated by reference into this EIS/EIR, and the findings of that analysis are summarized below and amended to be consistent with the statement of impact and significance formatting of this EIS/EIR. Impact 3.2.3.6.1-1 (Fourmile Hill Impact described in Section 4.3.3): Construction of the transmission line would impact surface runoff through clearing along the right-of-way and construction of new unpaved roads. Vegetation would be selectively removed along the transmission line corridor and sites cleared for construction of transmission line structures. Grading might be required at some transmission line structure sites. The removal of vegetation and localized compaction of soils would lead to increased runoff and could potentially result in localized erosion. Although construction of the transmission line could result in increased runoff rates, most soils along the proposed transmission line route and access roads are characterized by rapid infiltration rates. These soils would be sufficiently permeable so that any excess runoff would percolate into the subsurface a short distance downstream from the transmission line corridor or access roads. For the decommissioning phase, areas disturbed and graded by the proposed project would be reseeded and recontoured to essentially pre-project topography, where necessary and as directed by USFS. These activities would reduce any project impact to surface runoff rates. Significance of the Impact: Construction of the transmission line would not significantly increase surface runoff. The increase in surface runoff during the operational phase would be adverse, but not significant for the same reasons as the construction phase. Although the effects of increased runoff would not be significant, the following measures would help control runoff. Measures to reduce soil erosion would also reduce the potential for surface runoff. These measures are described in Section 3.1.3.6.1. Measure 3.2.3.6.1-1 (Fourmile Hill Measures 4.3.3a, 4.3.3c-4.3.3e): The following measures would help control surface runoff: The Project Applicant shall reseed, as recommended by USFS, all disturbed areas that will not be used (such as cut and fill slopes) after completion of the construction phase. The Project Applicant shall place drains or energy dissipaters at intervals along new access roads to allow water greater opportunities to exit the roadbed and percolate into the native soils, and prevent the discharge of large volumes of runoff at a few points along the road. The Project Applicant shall monitor new non-bladed roads for impacts to vegetation and increased runoff and erosion. If substantial impacts occur, the Project Applicant shall implement corrective action. These corrective measures could include construction of energy dissipaters, berms or culverts, or other appropriate runoff diversion structures. The Project Applicant shall seed and plant as recommended by USFS the area of the transmission line right-of-way disturbed during construction with low-growing native plants to provide soil stabilization. Seeding and planting shall occur before the next growing season after construction. Native plants that naturally revegetate (such as resprouting shrubs) should be utilized to the fullest extent possible. This mitigation measure shall be consistent with Fourmile Hill Measure 4.7.1d.

Impact 3.2.3.6.1-2 (Fourmile Hill Impact described in Section 4.3.4): Construction of the proposed transmission line could result in minor changes in surface drainage patterns. Construction of the transmission line and access roads would include the use of culverts and berms to direct drainage and avoid localized flooding. These measures combined with the high permeability of the project vicinity soils would ensure that no localized flooding would occur. No construction activities for the transmission line would take place within a 100-year flood plain. During decommissioning, the transmission line area would be returned, as much as possible, to pre-project conditions. The activities would return some surface drainage to their original state and would not result in any localized flooding. Significance of the Impact: No localized flooding would occur. There would be no impact on people or property from flooding as a result of the transmission line. Impact 3.2.3.6.1-2 (Fourmile Hill Impact described in Section 4.3.5): Line segment A2 of the transmission line would cross three identified intermittent streams. Construction of transmission line structures or access roads within streambeds could cause increased scour and erosion within stream channels. In addition, transmission line structures and access roads could be damaged by erosion if these facilities are constructed within streambeds. Construction activities which require vehicles to cross streambeds would also cause erosion within the streambed and on the bank. Line segment A2 would also cross associated Riparian Reserves. During the operational phase of the project, maintenance along the transmission line may require vehicles to cross intermittent stream channels. Vehicle traffic could result in temporarily increased erosion within the channel and along the bank. During decommissioning of the project, removal of the transmission line and associated structures may require vehicles to cross intermittent stream channels. Vehicle traffic could result in increased erosion within the channel and along the bank. Significance of the Impact: This impact was found to be potentially significant. The following mitigation measures are recommended to reduce the effects of the proposed transmission line Segment A2 to a less than significant level. Measure 3.2.3.6.1-2a (Fourmile Hill Measure 4.3.5a): The Project Applicant shall not site transmission line structures and access roads within Riparian Reserve areas, as delineated by the USFS. For streams located outside of Riparian Reserve areas, the Project Applicant shall not site transmission line structures and access roads (except road crossings) within 100 feet of intermittent stream channels. Measure 3.2.3.6.1-2b (Fourmile Hill Measure 4.3.5b): The Project Applicant shall ensure vehicular traffic in intermittent stream channels is minimized.

3.2.3.6.2 Environmental Consequences of Route 2 (Line Segments D2 + B2*)

The Telephone Flat Project Alternative Transmission Line Route 2 (11.43-12.26 miles) consists of an initial 0.6- to 1.43-mile line segment D2 and a 10.83-mile utility corridor line segment B2*. Line segment D2 proceeds eastward from the Telephone Flat Project power plant site and joins line segment B2 southwest of Red Shale Butte. Line segment B2* is that portion of the earlier proposed line segment B2 which originates at the terminus of line segment D2. Line segment B2* avoids the Glass Mountain Glass Flow Area as it continues southeast from its origin with line segment D2. Line segment B2* proceeds eastward south of Red Shale Butte before proceeding northeast to connect with the Northern Utility Corridor at the origin of line segment C1 or C2. Line Segment D2: There are no perennial surface water resources within the right-of-way planning corridors for line segment D2. Construction, operation and decommissioning of the initial transmission line interconnection segment D2 from any of the three power plant site alternatives would not be expected to have any adverse effects on water quality or quantity. Line Segment B2: Line segment B2 was the subject of earlier environmental analysis as part of the Fourmile Hill Project EIS/EIR (BLM et al. 1998). That analysis is incorporated by reference into this EIS/EIR, and the findings of that analysis are summarized below and amended to be consistent with the statement of impact and significance formatting of this EIS/EIR. Impact 3.2.3.6.2-1 (Fourmile Hill Impact described in Section 4.3.3): Construction of the transmission line would impact surface runoff through clearing along the right-of-way and construction of new unpaved roads. Vegetation would be selectively removed along the transmission line corridor and sites cleared for construction of transmission line structures. Grading might be required at some transmission line structure sites. The removal of vegetation and localized compaction of soils would lead to increased runoff and could potentially result in localized erosion. Although construction of the transmission line could result in increased runoff rates, most soils along the proposed transmission line route and access roads are characterized by rapid infiltration rates. These soils would be sufficiently permeable so that any excess runoff would percolate into the subsurface a short distance downstream from the transmission line corridor or access roads. For the decommissioning phase, areas disturbed and graded by the proposed project would be reseeded and recontoured to essentially pre-project topography, where necessary and as directed by USFS. These activities would reduce any project impact to surface runoff rates. Significance of the Impact: Construction of the transmission line would not significantly increase surface runoff. The increase in surface runoff during the operational phase would be adverse, but not significant for the same reasons as the construction phase. Although the effects of increased runoff would not be significant, the following measures would help control runoff. Measures to reduce soil erosion would also reduce the potential for surface runoff. These measures are described in Section . Measure 3.2.3.6.2-1 (Fourmile Hill Measures 4.3.3a, 4.3.3c-4.3.3e): The following measures would help control surface runoff: The Project Applicant shall reseed, as recommended by USFS, all disturbed areas that will not be used (such as cut and fill slopes) after completion of the construction phase. The Project Applicant shall place drains or energy dissipaters at intervals along new access roads to allow water greater opportunities to exit the roadbed and percolate into the native soils, and prevent the discharge of large volumes of runoff at a few points along the road. The Project Applicant shall monitor new non-bladed roads for impacts to vegetation and increased runoff and erosion. If substantial impacts occur, the Project Applicant shall implement corrective action. These corrective measures could include construction of energy dissipaters, berms or culverts, or other appropriate runoff diversion structures. The Project Applicant shall seed and plant as recommended by USFS the area of the transmission line right-of-way disturbed during construction with low-growing native plants to provide soil stabilization. Seeding and planting shall occur before the next growing season after construction. Native plants that naturally revegetate (such as resprouting shrubs) should be utilized to the fullest extent possible. This mitigation measure shall be consistent with Fourmile Hill Measure 4.7.1d. Impact 3.2.3.6.2-2 (Fourmile Hill Impact described in Section 4.3.4): Construction of the proposed transmission line could result in minor changes in surface drainage patterns. Construction of the transmission line and access roads would include the use of culverts and berms to direct drainage and avoid localized flooding. These measures combined with the high permeability of the project vicinity soils would ensure that no localized flooding would occur. No construction activities for the transmission line would take place within a 100-year flood plain. During decommissioning, the transmission line area would be returned, as much as possible, to pre-project conditions. The activities would return some surface drainage to their original state and would not result in any localized flooding.

Significance of the Impact: No localized flooding would occur. There would be no impact on people or property from flooding as a result of the transmission line. Impact 3.2.3.6.2-2 (Fourmile Hill Impact described for Alternative 3): Line segment B2 would cross two intermittent streams located just south of Red Shale Butte and approximately two miles southeast of Lyon’s Peak. Significance of the Impact: This impact was found to be potentially significant. The following mitigation measures are recommended to reduce the effects of the proposed transmission line segment B2 to a less than significant level. Measure 3.2.3.6.2-2a (Fourmile Hill Measure 4.3.5a): The Project Applicant shall not site transmission line structures and access roads within Riparian Reserve areas, as delineated by the USFS. For streams located outside of Riparian Reserve areas, the Project Applicant shall not site transmission line structures and access roads (except road crossings) within 100 feet of intermittent stream channels. Measure 3.2.3.6.2-2b (Fourmile Hill Measure 4.3.5b): The Project Applicant shall ensure vehicular traffic in intermittent stream channels is minimized.

3.2.3.6.3 Unavoidable Adverse Effects of Alternative Transmission Line Routes

No unavoidable adverse effects on water resources are anticipated from either of the Alternative Transmission Line Routes.

3.2.3.7 No Action Alternative

Under the No Action Alternative the Project would not be constructed.

3.2.3.7.1 Consequences of the No Action Alternative

There would be no impact on hydrologic or geothermal resources under the No Action Alternative.

3.2.3.7.2 Unavoidable Impacts of the No Action Alternative

No unavoidable adverse impacts to hydrologic or geothermal resources would result from the No Action Alternative.