Construction of the well pads and well drilling would be expected to increase noise levels at sensitive biological sites. The noise increase is inversely proportional to the distance between the source and receptor. Power plant operations would also increase noise level at sensitive biological sites but less than the increases associated with well pad construction and drilling. Although well pad construction would be noisier than well drilling and power plant operational noises, it is expected to be intermittent and of relatively short duration (about two weeks). Noise levels at the sensitive biological sites would be higher during well drilling than during power plant operations. The effects of noise on biological sensitive species is addressed in the biological resource section (see Section 3.3). Engineering or administrative measures should be considered as an alternative to moving a well pad location to reduce noise effects because a significant reduction (6 dB or more) of noise at a well pad would require very large changes in well pad location.

3.7.3.3.2 Unavoidable Adverse Impacts of the Proposed Action

Even with mitigation, noise levels at human receptor locations and sensitive biological sites would increase with the Project.

3.7.3.4 Alternative Power Plant Site A

3.7.3.4.1 Consequences of Alternative Power Plant Site A

Alternative Site A would locate the power plant site eastward about ¼-mile of the Proposed Action site. This would include only minor changes in well pad locations. Therefore, this section focuses only on the effects of the different power plant location. Relocation of the power plant would not affect noise produced by other Project operations at other locations, such as well pad construction noise or well drilling noise. Consequences of Construction and Operation Noise at Human Receptor Locations From Site A: As shown in Table 3.7.5, construction noise levels at the four human receptor locations are expected to increase with construction at the Alternative Site A power plant location rather than at the Proposed Action location. Noise levels are expected to be higher if the power plant is at the Alternative A location because the power plant would be at an elevation that is about 100 feet higher than the Proposed Action location (7,070 feet versus 6,970 feet). This higher elevation results in lower noise reductions due to terrain barriers. Thus, the estimated noise levels of the receptors are somewhat higher even though the distance is greater between the Alternative Site A location and any human receptor location than is the case with the Proposed Action power plant site. Noise levels estimated to result from the power plant operating at the Proposed Action site and the two Project Alternative locations are provided in Table 3.7.8. As presented in previous tables, the noise levels associated with power plant operations are lower than those from construction. The pattern of noise level increases at the human receptor locations is, on average, slightly higher for Alternative Site A than the Proposed Action and the rationale follows that described above for construction-related noise.

Power plant operational noise from the Alternative Site A location should not be audible at any of the human receptor locations because the noise levels are significantly less than ambient (See Table 3.7.1). By contrast, construction noise may be relatively more audible from Alternative Site A than from the Proposed Action site at three of the four receptor locations (the two residential locations and the campgrounds at Bullseye and Blanche Lakes); the exception is the campground on the north side of Medicine Lake. The increase in audibility does not exceed 10 dB. Impact 3.7.3.4-1: Hikers and other forest visitors within about ½-mile of areas of active surface disturbance would be able to hear Project construction activities. These sounds would be audible but visitors are expected to be transient and the adverse effects of Project construction noise would be temporary. Significance of the Impact: This impact is considered to be below the level of significance and no mitigation measures are required. Similarly, the noise levels estimated at any of the four receptor locations do not attain Leq = 54 dBA, which is considered the threshold for significance according to Siskiyou County. Impact 3.7.3.4-2: Under some worst case conditions, sound may be audible at some human receptor locations near Medicine Lake. In general, well drilling noise would be louder than operational noise from the power plant. The maximum projected noise levels would not exceed Siskiyou County’s noise limit (Leq = 54 dBA). Significance of the Impact: This impact is below the level of significance and no mitigation measures are required, but, the following other measure is provided to reduce the adverse effects of the impact. Other Measure 3.7.3.4-2a: Project Applicant shall erect temporary noise shields around portions of the drilling rig during well drilling to further reduce the noise effects on human receptors. Generally, noise shields would be needed on only those wells identified herein as being dominant (i.e., wells at well pads 73-13, 16-18, 87-13, 51-18 and 56-18). Other Measure 3.7.3.4-2b: The Project Applicant shall install “residential grade” mufflers on the noisiest well drilling equipment. Consequences of Construction and Operation Noise at Native American Vision Quest Sites From Site A: The estimated noise levels at the traditional cultural site location 17 and location 20 noise receptors during construction of the two nearest well pads and the Alternative Site A power plant site are shown in Table 3.7.11. The Table also provides estimates of the sound levels during the drilling of wells at the two nearest well pads to the receptor locations. The Table shows that the projected noise levels at location 17 are uniformly lower than those estimated for location 20. Noise levels due to construction are estimated to be at least 10 dBA higher than ambient and would be expected to be audible. Project noise levels at the traditional cultural site location 17 and location 20 receptor locations during power plant operations are also shown in Table 3.7.11. At location 17, the estimated noise levels are less than ambient levels regardless of the alternative power plant site selected. In contrast, noise levels would be more audible at location 20 from Alternative Power Plant Site A than from the proposed power plant site. Noise levels at the identified Native American vision quest sites would be higher during well drilling and construction than during power plant operations. The effects of noise at these sites is addressed in the Native American Values section (see Section 3.6.2.7). Consequences of Construction and Operation Noise on Sensitive Biological Species From Site A: Since terrain barriers were assumed not to be functioning for five of the six SBS receptor locations (SBS BS-5S-PYN is the exception), the changes in noise level at the various SBS locations reflect the changes in distance relative to the distance between the Project Alternative Power Plant Site A location and the SBS receptor locations. For example, the Proposed Action power plant site is farthest from SBS BS-2E-TB, and Alternative Site A is closer to that receptor. Therefore, as shown in Table 3.7.6, construction noise levels become louder as the power plant location moves from 39 dBA at the Proposed Action location to 41 dBA at Alternative Site A.

In contrast, the Proposed Action is nearest to SBS receptor location BS-4S-NSO, while Alternative Site A is farther from this SBS location. As shown in Table 3.7.9, power plant operational noise decreases as the power plant location moves from the Proposed Action location to the Project Alternative Power Plant Site A location. Alternative Site A is nearer to SBS receptor location BS-1E-NGH than are either the Proposed Action or the Alternative Site B power plant sites. Thus, as may be seen in both Tables 3.7.6 and 3.7.9, the noise levels during construction or when the power plant is operating are expected to be loudest when the power plant is located at Alternative Site A and quieter at either of the other two locations. The effects of the increases in Project-related construction and operation noise levels on some sensitive wildlife and wildlife habitat resulting from moving the power plant site from the Proposed Action location to the Alternative Site A location is discussed in Section 3.3.

3.7.3.4.2 Unavoidable Adverse Impacts of Alternative Power Plant Site A

Even with mitigation, noise levels at human receptor locations and sensitive biological sites would increase with the Project.

3.7.3.5 Alternative Power Plant Site B

Alternative Site B would locate the power plant site eastward about ½-mile of the Proposed Action site. This would include only minor changes in well pad locations. Only one new well pad (77-18), not provided for in the Proposed Action or Alternative Site A would be constructed if Alternative Site B is implemented. Therefore, this section primarily focuses only on the effects of the different power plant location. Relocation of the power plant should would not affect noise produced by other Project operations at other locations, such as well pad construction noise or well drilling noise. Consequences of Construction and Operation Noise at Human Receptor Locations From Site B: As shown in Table 3.7.5, construction noise levels at the four human receptor locations are expected to decrease with construction at the Alternative Site B power plant location rather than either the Proposed Action or Alternative Site A locations. The elevation of 7,050 feet for the Alternative Site B location is 20 feet lower than and slightly north of the Alternative Site A location. At this elevation and location, terrain barriers are more effective than at Alternative Site A and Alternative Site B is much farther from the human receptor locations than is the Proposed Action location. As a result, construction noise levels at Alternative Site B are shown in Table 3.7.5 to be lower than at either the Proposed Action or Alternative Site A locations. As is shown and explained in the table, the exception is at the campground at the north side of Medicine Lake, for which terrain does not produce an effective barrier. In addition, well pad 77-13 is unique to Alternative Site B and well pad construction noise may be audible at times at the campgrounds at Bullseye and Blanche Lakes. The increase in audibility does not exceed 10 dB, rather it is at the ambient level of 34 dBA. Impact 3.7.3.5-1: Hikers and other forest visitors within about ½-mile of areas of active surface disturbance would be able to hear Project construction activities. These sounds would be audible but visitors are expected to be transient and the adverse effects of Project construction noise would be temporary. Significance of the Impact: This impact is considered to be below the level of significance and no mitigation measures are required. Noise levels estimated to result from the power plant operating at the Proposed Action site and the two Project Alternative locations are provided in Table 3.7.8. As presented in previous tables, the noise levels associated with power plant operations are lower than those from construction. The pattern of noise level increases at the human receptor locations is slightly lower for Alternative Site B than either the Proposed Action or Alternative Site A and the rationale follows that described above for construction-related noise. Power plant operational noise from the Alternative Site B location should not be audible at any of the human receptor locations because the noise levels are significantly less than ambient (See Table 3.7.1).

Similarly, the noise levels estimated at any of the four human receptor locations do not attain Leq = 54 dBA, which is considered the threshold for significance according to Siskiyou County. Impact 3.7.3.5-2: Under some worst case conditions, sound may be audible at some human receptor locations near Medicine Lake. In general, well drilling noise would be louder than operational noise from the power plant. The maximum projected noise levels would not exceed Siskiyou County’s noise limit (Leq = 54 dBA). Significance of the Impact: This impact is below the level of significance and no mitigation measures are required, but, the following other measure is provided to reduce the adverse effects of the impact. Other Measure 3.7.3.5-2a: Project Applicant shall erect temporary noise shields around portions of the drilling rig during well drilling to further reduce the noise effects on human receptors. Generally, noise shields would be needed on only those wells identified herein as being dominant (i.e., wells at well pads 73-13, 16-18, 87-13, 51-18 and 56-18). Other Measure 3.7.3.5-2b: The Project Applicant shall install “residential grade” mufflers on the noisiest well drilling equipment. Consequences of Construction and Operation Noise at Native American Vision Quest Sites From Site B: The estimated noise levels at the traditional cultural site location 17 and location 20 receptors during construction of the two nearest well pads and the Alternative Site B power plant site are shown in Table 3.7.11. The Table also provides estimates of the sound levels during the drilling of wells at the two nearest well pads to the receptor locations. The Table shows that the projected noise levels at location 17 are uniformly lower than those estimated for location 20. Noise levels due to construction are estimated to be at least 10 dBA higher than ambient and would be expected to be audible. Project noise levels at the traditional cultural site location 17 and location 20 receptor locations during power plant operations are also shown in Table 3.7.11. At location 17, the estimated noise levels are less than ambient levels regardless of the alternative power plant site selected. In contrast, noise levels would be more audible at location 20 from Alternative Site B than from either the proposed power plant site or from Alternative Site A. Noise levels at the identified Native American vision quest sites would be higher during well drilling and construction than during power plant operations. The effects of noise at these sites is addressed in the Native American Values section (see Section 3.6.2.7). Consequences of Construction and Operation Noise on Sensitive Biological Species From Site B: Since terrain barriers were assumed not to be functioning for five of the six SBS receptor locations (SBS BS-5S-PYN is the exception), the changes in noise level at the various SBS locations reflect the changes in distance relative to the distance between the Project Alternative Power Plant Site B location and the SBS receptor locations. For example, the Proposed Action power plant site is farthest from SBS BS-2E-TB, and Alternative Site B is closest to that receptor. Therefore, as shown in Table 3.7.6, construction noise levels become louder as the power plant location moves from 39 dBA at the Proposed Action location to 43 dBA at Alternative Site B. In contrast, the Proposed Action is nearest to SBS receptor location BS-4S-NSO, while Alternative Site B is farthest from this SBS location. As shown in Table 3.7.9, power plant operational noise decreases as the power plant location moves from the Proposed Action location to the Project Alternative Power Plant Site B location. Alternative Site B is nearer to SBS receptor location BS-1E-NGH than the Proposed Action power plant site but further than the Alternative Site A power plant site. Thus, as may be seen in both Tables 3.7.6 and 3.7.9, the noise levels during construction or when the power plant is operating are expected to be generally quieter when the power plant is located at Alternative Site B than at either of the other two locations. The effects of Project-related construction and operation noise levels on some sensitive wildlife and wildlife habitat resulting from moving the power plant site from the Proposed Action location to the Alternative Site B location is discussed in Section 3.3.

3.7.3.5.1 Unavoidable Adverse Impacts of Alternative Power Plant Site B

Even with mitigation, noise levels at human receptor locations and sensitive biological sites would increase with the Project.

3.7.3.6 Alternative Transmission Line Routes

Previous Transmission Line Impact Assessment: As discussed in Section , 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 Noise 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 3-201 through 3-207, and 4-254 through 4-270 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). Under Fourmile Hill Project Alternatives 1 and 3, the construction and decommissioning of the three transmission line towers of line segment C1 nearest to residences in Tionesta, are expected to require less than one week for each phase. During this period, daytime noise levels from these activities are estimated to be about 61 dBA at the residence approximately 1,500 feet from the power lines. The noise level would be about 57 dBA at the residence farthest from the power lines. Noise levels at both residences would exceed Modoc County's 48 dBA limit ( 65 Ldn) for residential uses if that noise level was present over 24 hours. However, tower line construction and decommissioning are expected to require roughly 9 hours per day, and the average noise level over the 24-hour period is calculated to be Ldn = 53, which is well below the County's limit. Although the construction and decommissioning noise may be audible, it is expected to be of relatively short duration (about 1 week for each Project phase) and thus the impact on residents of Tionesta was determined to be below the level of significance (BLM et al. 1998). 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. The initial transmission line segments from the three alternative power plant sites (i.e., Proposed Action, Alternative Site A, and Alternative Site B) are approximately the same. Transmission line interconnection segment D1 goes north and west of Alcohol Crater from each of the alternative power plant sites to tie-in with the Fourmile Hill Geothermal Project utility corridor line segment A2. The D1/A2 line segments then comprise the proposed Telephone Flat Project Transmission Line Alternative Route 1 to the Northern Utility Corridor. Transmission line interconnection segment D2 goes east from each of the alternative power plant sites to tie-in with the Fourmile Hill Geothermal Project utility corridor line segment B2*. The D2/B2* line segments then comprise Telephone Flat Project Transmission Line Alternative Route 2 to the Northern Utility Corridor.

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

Route 1 would be a total of about 4.95 miles of transmission line of transmission line from the Proposed Action power plant site to the Northern Utility Corridor. Except for the differences attributable to the different distances of the alternative transmission line routes, there are no substantive additional adverse noise effects anticipated as a result of either of the Alternative Transmission Line Routes. Line Segment D1: Line segment D1 is located entirely within the Project wellfield area, and the effects for line segment D1 would be the same as those described for the Proposed Action. Line Segment A2: The noise effects of the construction, operation, and decommissioning the relevant transmission line segments comprising the alternative utility corridors were evaluated as part of the EIS/EIR prepared for the Fourmile Hill Project (BLM et al. 1998). The findings of that analysis for transmission line segments relevant to the Telephone Flat Project are incorporated by reference into this EIS/EIR. Noise impacts associated with line segment A2 are summarized below. Impact 3.7.3.6.1-1 (Fourmile Hill Impact described in Section 4.14.1): For the proposed transmission line, noise generated during project construction would potentially result in a short-term impact to forest users that may come in close proximity to the transmission line during construction. Construction activities would not exceed County noise standards for more than a week; this effect would occur only on a short-term basis. Operation of the proposed transmission line would not result in the generation of noise and therefore would not impact ambient noise levels in the forest. Routine maintenance activities, expected to occur twice a year, could produce temporary noise increases, likely to be much lower than construction noise levels. The occasional presence of vehicles and equipment to repair downed wires, damaged towers, or other facilities (associated with snow, wind, and other conditions) could also be present along the transmission line. Noise levels from such activities would likely be less than for construction, but could result in adverse effects on forest visitors using areas in close proximity to such line repairs. Similar to construction, decommissioning would potentially result in a short-term effect. Significance of the Impact: Noise impacts to forest users that may come in close proximity to the transmission line would be potentially significant during construction and decommissioning, but would be short-term in nature. No significant impacts would occur to sensitive receptors. The following other measures would further reduce impacts to sensitive receptors. Measure 3.7.3.6.1-1a (Fourmile Hill Measure 4.12.2a): The Project Applicant would use feasible noise controls on standard construction equipment to minimize potential noise effects to existing nearby residences. Impact tools would be shielded or shrouded when practicable, and equipment would have a muffled exhaust. Measure 3.7.3.6.1-1b (Fourmile Hill Measure 4.12.2c): The Project Applicant would implement site-specific measures to respond to complaints and minimize future disturbances of nearby residences. Such measures could include changing the location of stationary equipment, installing acoustic barriers around stationary construction noise sources, shutting off idling equipment, and rescheduling construction activity.

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

Route 2 would be a total of about 12.26 miles of transmission line from the Proposed Action power plant site to the Northern Utility Corridor. Except for the differences attributable to the different distances of the alternative transmission line routes, there are no substantive additional adverse noise effects anticipated as a result of either of the Alternative Transmission Line Routes. Line Segment D2: Line segment D2 is located entirely within the Project wellfield area, and the effects for line segment D2 would be the same as those described for the Proposed Action. Line Segment B2: The noise effects of the construction, operation, and decommissioning the relevant transmission line segments comprising the alternative utility corridors were evaluated as part of the EIS/EIR prepared for the Fourmile Hill Project (BLM et al. 1998). The findings of that analysis for transmission line segments relevant to the Telephone Flat Project are incorporated by reference into this EIS/EIR. Noise impacts associated with line segment B2 are summarized below. Except for the difference in transmission line length, the adverse effects of the Alternative Route 2 on noise and vibration resources would be similar to those described for Route 1. Impact 3.7.3.6.2-1 (Fourmile Hill Impact described in Section 4.14.1): For the proposed transmission line, noise generated during project construction would potentially result in a short-term impact to forest users that may come in close proximity to the transmission line during construction. Construction activities would not exceed County noise standards for more than a week; this effect would occur only on a short-term basis. Operation of the proposed transmission line would not result in the generation of noise and therefore would not impact ambient noise levels in the forest. Routine maintenance activities, expected to occur twice a year, could produce temporary noise increases, likely to be much lower than construction noise levels. The occasional presence of vehicles and equipment to repair downed wires, damaged towers, or other facilities (associated with snow, wind, and other conditions) could also be present along the transmission line. Noise levels from such activities would likely be less than for construction, but could result in adverse effects on forest visitors using areas in close proximity to such line repairs. Similar to construction, decommissioning would potentially result in a short-term effect. Significance of the Impact: Noise impacts to forest users that may come in close proximity to the transmission line would be potentially significant during construction and decommissioning, but would be short-term in nature. No significant impacts would occur to sensitive receptors. The following other measures would further reduce impacts to sensitive receptors. Measure 3.7.3.6.2-1a (Fourmile Hill Measure 4.12.2a): The Project Applicant would use feasible noise controls on standard construction equipment to minimize potential noise effects to existing nearby residences. Impact tools would be shielded or shrouded when practicable, and equipment would have a muffled exhaust. Measure 3.7.3.6.2-1b (Fourmile Hill Measure 4.12.2c): The Project Applicant would implement site-specific measures to respond to complaints and minimize future disturbances of nearby residences. Such measures could include changing the location of stationary equipment, installing acoustic barriers around stationary construction noise sources, shutting off idling equipment, and rescheduling construction activity.

3.7.3.6.3 Unavoidable Adverse Impacts of the Alternative Transmission Line Routes

Either of the Alternative Transmission Line Routes would result in increased construction, maintenance, and decommissioning noise effects. None of these noise effects is considered a significant impact.

3.7.3.7 No Action Alternative

3.7.3.7.1 Consequences of the No Action Alternative

If the Project is not constructed, Project-related changes in noise levels at both the human receptors and sensitive biological sites would not occur. However, noise levels may increase as a result of an expected expansion of recreational usage of the Medicine Lake facilities during both the summer and winter seasons.

3.7.3.7.2 Unavoidable Adverse Impacts of the No Action Alternative

There would be no unavoidable noise impacts as a result of the No Action Alternative.