Addendum to the Final Environmental Impact Report
Silver Lake Reservoir Complex Storage Replacement Project SCH # 2003081133
Los Angeles Department of Water and Power Environmental Affairs 111 North Hope Street, Room 1044 Los Angeles, California 90012
December 2013
Silver Lake Reservoir Complex Storage Replacement Project
Table of Contents
Section 1 Introduction 1.1 Purpose of the Addendum ...... 1 1.2 Project Overview ...... 2 1.3 Approved Bypass Pipeline Alignment ...... 2 1.4 Reconsideration of In-Reservoir Pipeline Alignment ...... 20
Section 2 Environmental Impact Assessment 2.1 Land Use ...... 33 2.2 Earth Resources ...... 34 2.3 Water Resources ...... 35 2.4 Biological Resources ...... 35 2.5 Cultural Resources ...... 37 2.6 Paleontological Resources ...... 38 2.7 Traffic and Transportation ...... 38 2.8 Noise ...... 40 2.9 Air Quality ...... 41 2.10 Public Services and Utilities ...... 42 2.11 Hazardous Materials ...... 43 2.12 Visual Resources ...... 44 2.13 Other Environmental Issues ...... 45
List of Figures
Figure 1 Approved Bypass Pipeline Alignment ...... 4 Figure 2 Refined Bypass Pipeline Tunneling Alignment ...... 7 Figure 3 Redesdale North Tunneling Shaft ...... 10 Figure 4 Redesdale South Tunneling Shaft ...... 13 Figure 5 Putnam Tunneling Shaft ...... 15 Figure 6 In-Reservoir Pipeline Alignment ...... 22 Figure 7 Work Areas 1 and 2 ...... 25 Figure 8 Work Area 3 ...... 26
List of Tables
Table 1 Bypass Pipeline Tunneling Alignment Construction Activities ...... 18 Table 2 In-Reservoir Pipeline Alignment Construction Activities ...... 30
December 2013 Page i Table of Contents
Acronyms and Abbreviations
CEQA California Environmental Quality Act DB decibel DBA a-weighted decibel EIR Environmental Impact Report EPBM earth pressure balance machine LADWP Los Angeles Department of Water and Power Leq community equivalent noise level MG million gallons NOx nitrogen oxides O3 ozone PM2.5 particulate matter less than 2.5 microns in diameter PM10 particulate matter less than 10 microns in diameter PSI pounds per square inch SCAQMD South Coast Air Quality Management District SLRC Silver Lake Reservoir Complex
Page ii Silver Lake Reservoir Complex Storage Replacement Project
SECTION 1 INTRODUCTION
1.1 Purpose of the Addendum
This addendum to the previously certified Environmental Impact Report (EIR) for the Los Angeles Department of Water and Power (LADWP) Silver Lake Reservoir Complex Storage Replacement Project (SCH # 2003081133) has been prepared in accordance with California Environmental Quality Act (CEQA) Guidelines Section 15164 to revise the certified EIR to accurately reflect the changes or additions to the project, changes in conditions under which the project is undertaken, or to add new information. In accordance with CEQA Guidelines Section 15162, changes to the approved project addressed in this addendum would not result in new significant environmental effects or a substantial increase in the severity of previously identified significant effects, as discussed herein.
The Final EIR for the Silver Lake Reservoir Complex Storage Replacement Project was certified by the City of Los Angeles Board of Water and Power Commissioners on May 16, 2006, concurrent with approval of the project (Certified EIR). A Notice of Determination for the project approval was filed with the State Clearinghouse and the Los Angeles County Clerk’s office on May 18, 2006. The approved project in the Certified EIR will remove Silver Lake and Ivanhoe Reservoirs from the LADWP potable water distribution system and relocate the water storage function provided by the Silver Lake Reservoir Complex (SLRC) to the former Headworks Spreading Grounds site, where a new 110-million gallon (MG) buried storage reservoir is currently under construction. The Certified EIR found the proposed project to have significant but mitigable environmental impacts to Earth Resources (Chapter 4), Water Resources (Chapter 5), Biological Resources (Chapter 6), Cultural Resources (Chapter 7), and Paleontologic Resources (Chapter 8). Impacts to Traffic and Transportation (Chapter 9), Noise (Chapter 10), and Air Quality (Chapter 11) would be significant and unavoidable even after incorporation of feasible mitigation measures. A Statement of Overriding Considerations was adopted for these unavoidable impacts. Less than significant impacts to Land Use (Chapter 3), Public Services and Utilities (Chapter 12), Hazardous Materials (Chapter 13), and Visual Resources (Chapter 14) were identified in the Certified EIR.
Since the initial project approval, the engineering design for the project has proceeded, establishing a more refined concept for the physical and procedural aspects of project construction than was available at the time of the preparation and consideration of the Certified EIR. Further, it has been determined that a different alignment for an interconnecting pipeline between the River Supply Conduit and the Silver Lake Outlet Line, a component of the project as described and analyzed in the Certified EIR, can be feasibly implemented that would reduce the duration of construction within public roadways and the associated community disruption. Instead of constructing a tunnel beneath West Silver Lake Drive adjacent to the SLRC, the interconnecting pipeline would be located primarily within the SLRC, including within Silver Lake Reservoir, as explained in detail below.
In deciding whether a subsequent or supplemental EIR is necessary or if an addendum is appropriate, the standard of review is whether the record as a whole contains substantial evidence to support a determination that the changes in the project or its circumstances are substantial enough to make major modifications to the EIR due to the involvement of new significant environmental effects or a substantial increase in the severity of previously identified significant effects.
December 2013 Page 1 Introduction
The SLRC in-reservoir pipeline alignment has not altered the fundamental objectives of the project as reflected in the Certified EIR. The project would still relocate the SLRC water storage to the Headworks Spreading Grounds site. Long-term project operations are not anticipated to change from what was considered in the Certified EIR. However, based on additional site investigations and more extensive design development, it has been determined that implementation of the interconnecting pipeline would result in changes to the construction phase of activities within and adjacent to the SLRC. In accordance with CEQA, the nature and extent of these changes must be considered in the context of the Certified EIR conclusions regarding project-related environmental impacts to determine if they might create new significant impacts that were not identified in the Certified EIR or substantial increases in the severity of significant impacts that were identified in the Certified EIR. LADWP has developed the in-reservoir alignment for the interconnecting pipeline to minimize community disruption and the associated impacts by reducing the extent and duration of construction within public roadways. As discussed herein, the proposed modifications to the project design would not result in new environmental impacts or increase the severity of previously identified environmental impacts. The following sections provide additional detail regarding the proposed modifications and findings.
1.2 Project Overview
As a component of the Silver Lake Reservoir Complex Storage Replacement Project, the reservoir complex will be removed from service as a treated drinking water storage facility, but both Silver Lake and Ivanhoe Reservoirs will continue to be filled with non-potable water. The drinking water storage function of the reservoir complex will be replaced by a new reservoir at the Headworks Spreading Grounds site in Griffith Park. However, because it will not contain potable water, the SLRC will no longer provide a physical link, as it currently does, between the River Supply Conduit (a trunk line that currently supplies drinking water to the SLRC at the north end of Ivanhoe Reservoir) and the Silver Lake Outlet Line (a trunk line that currently supplies water from the SLRC to large areas of the City of Los Angeles south of Silver Lake). Therefore, as described in the Certified EIR, it is necessary to construct a new potable water pipeline to provide a connection between the terminus of the River Supply Conduit and the start of the Silver Lake Outlet Line, which are separated by approximately 1 mile. The recently reconstructed River Supply Conduit terminates north of Ivanhoe Reservoir near the intersection of West Silver Lake Drive and Armstrong Avenue. The Silver Lake Outlet Line commences south of Silver Lake Reservoir, where West Silver Lake Drive turns from eastbound to southbound near the Silver Lake Recreation Center.
1.3 Approved Bypass Pipeline Tunneling Alignment
Background
As described in the Certified EIR, the interconnecting pipeline would follow an alignment that physically bypasses both Ivanhoe and Silver Lake Reservoirs, rather than an alignment that would route the line through the SLRC. This bypass alignment was chosen primarily because at the time the EIR was certified in 2006, both Silver Lake and Ivanhoe Reservoirs were still active treated drinking water storage facilities providing service to a large area of the City. This was at a time when several of the largest uncovered drinking water reservoirs, including Upper and Lower Hollywood, Encino, and Lower Stone Canyon Reservoirs, had recently been permanently removed from service in order to comply with the conditions of the 1989 Surface Water Treatment Rule. The removal of these four reservoirs from service eliminated approximately 8
Page 2 Silver Lake Reservoir Complex Storage Replacement Project billion gallons of treated water from the LADWP in-City storage system, placing greater reliance on the fewer remaining storage facilities, including the SLRC, to meet fluctuations in demand for drinking water and provide emergency supplies within local service areas. Both Silver Lake and Ivanhoe Reservoirs were eventually planned for removal from service as part of the replacement project involving the construction of the Headworks Reservoir, but the LADWP water supply and consumption models at the time of the Certified EIR indicated that both reservoirs were necessary to meet anticipated peak demand until the completion of the Headworks Reservoir and the new interconnecting pipeline between the River Supply Conduit and the Silver Lake Outlet Line.
Although Silver Lake Reservoir was actually removed from service in 2008, ahead of the anticipated schedule, this was based on emergency circumstances related to the potential health effects of the unexpected and previously unobserved formation of bromate (a potentially toxic and carcinogenic chemical compound) in the reservoir. However, this situation was not foreseen at the time when the bypass alignment was identified in the Certified EIR as the preferred option to interconnect the River Supply Conduit and the Silver Lake Outlet Line. To resolve the concerns related to bromate formation, there was no practical solution related to Silver Lake Reservoir other than removing it from service, especially considering the relatively short-term remaining period of operation for the reservoir before it was to be permanently shut down as a treated drinking water facility. To maintain the crucial interconnection between the River Supply Conduit and the Silver Lake Outlet Line, Ivanhoe Reservoir has remained in service. However, to control the formation of bromate (which generally occurs when naturally occurring bromide contained in source water interacts with chlorine in the presence of sunlight), Ivanhoe Reservoir was covered with shade balls, which was a solution considered not appropriate for Silver Lake Reservoir, given its relatively short projected service life and that its surface area is over 10 times that of Ivanhoe Reservoir. Based on the success of expanded water conservation programs in the City of Los Angeles that were not factored into earlier demand models utilized at the time of the Certified EIR, Ivanhoe Reservoir has proven adequate on an interim basis to meet the peak demand for water from the SLRC. Since it was considered necessary at the time that Silver Lake and Ivanhoe Reservoirs remain filled and fully operational, construction of the interconnecting pipeline within the reservoirs was not deemed a feasible option.
Pipeline Tunneling Concept
To provide suitable access to the new pipeline for future maintenance and to minimize direct impacts to private property, the bypass alignment would necessarily need to be located within public roadways. The most direct route within roadways between the terminus of the reconstructed River Supply Conduit and the beginning of the Silver Lake Outlet Line was determined to generally follow West Silver Lake Drive. However, to maintain adequate system operating pressure based on the planning assumptions at the time, the bypass pipeline would need to be located at a depth below the surface level of the roadway that would make a conventional open-trench method of installation infeasible. Therefore, the only viable means to install the pipeline along the length of West Silver Lake Drive was by tunneling (see Figure 1).
December 2013 Page 3
Silver Lake Reservoir Complex Storage Replacement Project
In order to minimize the number of sharp turns in the pipeline, which are more difficult to achieve with tunneling and require more frequent openings at the street surface for the pipe installation at each turning point, the bypass pipeline tunneling alignment was established as follows:
From the terminus of the River Supply Conduit on West Silver Lake Drive, south along West Silver Lake Drive to a point approximately 200 feet south of Balmer Drive, parallel with a northeasterly extension of Redesdale Avenue (which does not actually intersect West Silver Lake Drive at this location); then southwesterly along Redesdale Avenue to the intersection of West Silver Lake Drive and Redesdale Avenue, about 125 feet south of Castle Street; and then southeasterly along West Silver Lake Drive to the start of the Silver Lake Outlet Line.
Tunneling has the advantage of minimizing the continuous disruption at the roadway surface that characterizes a conventional open-trench method of pipeline construction. In general, it also entails the movement of a lower volume of soil, since the excavation involves boring a tunnel only as wide as the outside diameter of the pipe or tunnel lining itself rather than the larger cut required for open trench construction. However, in order to excavate the tunnel, open pits (or shafts) are required at the surface to provide access at the tunnel beginning and end points and at major turning points in the pipeline alignment. Depending on the width, depth, and number of shafts required for a tunneling project, the volume of excavated material could increase substantially. Also, these shafts generally need to remain open in the same location for extended periods during construction, whereas the surface disturbance associated with open- trench construction, while potentially more extensive, generally moves along the pathway of the pipeline as pipe segments are installed and the road is restored. However, if the open-trench construction involves a lengthy portion of a single street (as would be the case on West Silver Lake Drive for the approved bypass pipeline tunneling alignment), the disruptions to traffic on the street could be considered continuous regardless of the fact that construction would occur in a series of smaller sequential segments.
The method of tunneling considered in the Certified EIR was to employ a relatively small diameter micro-tunneling machine located at the leading edge of the pipeline, which would be continually extended by pipe sections that would be fed from behind at the entry shaft and pushed forward through the tunnel by a large hydraulic jack. Excavated material (or muck) would be transported back to the entry shaft through the tunnel in haul carts, which would be lifted from the shaft and emptied at the surface, where the muck would be loaded into trucks and hauled away. In the Certified EIR, an entry shaft containing the hydraulic jacking equipment would be located on West Silver Lake Drive near Putnam Street; this shaft location is heretofore referred to as the Putnam Shaft. From the Putnam Shaft, the tunneling and pipe jacking would proceed south along West Silver Lake Drive to the point parallel with a northeasterly extension of Redesdale Avenue, where a receiving shaft would be located in West Silver Lake Drive; this shaft location is heretofore referred to as the Redesdale North Shaft. A second entry shaft would be located at the intersection of West Silver Lake Drive and Redesdale Avenue, about 125 feet south of Castle Street; this shaft is heretofore referred to as the Redesdale South Shaft. From the Redesdale South Shaft, tunneling and pipe jacking would proceed northeasterly along Redesdale Avenue to the Redesdale North Shaft, where the pipe would be joined to the pipe that had been jacked from the Putnam Shaft. From the Redesdale South Shaft to the connection with the Silver Lake Outlet Line, located about 250 feet to the southeast, the new pipeline would be constructed by means of trenching rather than tunneling because it could be installed at shallower depths in this segment and still maintain the necessary operating
December 2013 Page 5 Introduction pressure. Similarly, from the Putnam Shaft northward to the connection with the River Supply Conduit, the pipe would be constructed by means of trenching. In addition to the installation of the bypass pipeline, the project as described in the Certified EIR includes the construction of a regulator station near the Silver Lake Recreation Center and a pressure relief station located 0.25 miles south of the SLRC.
Refinement of Bypass Pipeline Tunneling Concept
Based on additional engineering analysis and design development that have occurred in preparation for project construction since certification of the Silver Lake Reservoir Complex Storage Replacement Project EIR, the original tunneling concept described above has been refined. Further geotechnical investigations of subsurface soil conditions have indicated that the pipeline would need to be installed at depths beneath the surface elevation of West Silver Lake Drive ranging from 40 to 95 feet, which is deeper than originally expected. This depth of installation and the anticipated soil and groundwater conditions would require the use of a larger-diameter tunnel boring machine known as an earth pressure balance machine (EPBM), which is designed to protect the interior of the tunnel and support the tunnel face in soft ground and/or in locations where groundwater intrusion may be an issue. The EPBM would be used to cut a 10-foot diameter tunnel to accommodate a precast concrete segmental tunnel lining, within which a 66-inch diameter welded steel pipe would be installed to conduct water.
The rotating cutter head of the EPBM would be pushed forward by thrust cylinders that are internal to the machine, pushing off the last completed tunnel lining ring, rather than being driven forward by pipe sections being jacked into the tunnel from the entry shaft. The segmental concrete tunnel lining would be installed within a protected shield area of the EPBM located behind the cutter head. The lining would be composed of individual segments, several of which would be required to complete the entire circumference of a lining ring. Muck would be transferred through the cutter head and out of the tunnel by means of a screw conveyor, conveyor belt, and haul carts, which would carry the muck to the entry shaft and be lifted by a crane to the surface, where the muck would be transferred to a holding area, from which it would be loaded into trucks and hauled away. After the tunnel between the shafts was completed, the welded steel pipe would be installed, with individual 20-foot long pipe sections transported into the tunnel by a self-propelled pipe carrier and welded to the preceding section of pipe. Conceptual plans for the required entry and receiving shafts and the associated construction zones at the surface of West Silver Lake Drive have been prepared based on this refinement in the tunneling approach and further design development for the interconnecting pipeline (see Figure 2 for the overall concept plan). The primary construction zones and activities are described below.
Page 6
Source: LADWP 2013
0 5 01Miles Figure 2
Refined Bypass Pipeline Tunneling Alignment I Introduction
Prior to initiating actual construction work related to the interconnecting pipeline, Ivanhoe Reservoir will be removed from service as a drinking water storage facility in late 2014, consistent with deadlines established by the California Department of Public Health related compliance with the federal Long-Term 2 Enhanced Surface Water Treatment Rule. This will be possible because the first phase of Headworks Reservoir will also be complete in late 2014, providing sufficient storage capacity to replace Ivanhoe Reservoir. The water from Headworks Reservoir will be temporarily routed through Rowena Pump Station and via an alternate distribution pathway until the completion of the new interconnecting pipeline at the SLRC (this temporary routing will be adequate on an interim basis but would not provide the required capacity, reliability, or system redundancy on a long-term basis). In order to take Ivanhoe Reservoir out of service, the shade ball cover currently on the reservoir will be removed. The reservoir will then be drained, first through normal consumption until the water level reaches the lower limit of the normal operating range, below which water will be pumped from Ivanhoe Reservoir into Silver Lake Reservoir. Once the reservoir is drained, the inlet to the reservoir will be severed and the outlet to the drinking water distribution system will be modified to prevent future cross-contamination from the non-potable water that will be stored in the reservoir. The reservoir will then be refilled, but the shade balls will not be redeployed. Ivanhoe will remain an open reservoir containing non-potable water.
Redesdale North Shaft
The use of the EPBM requires a shaft large enough to assemble and launch the machine and accommodate construction activities such as the transfer of the lining ring segments into the tunnel, the transfer of the muck out of the tunnel and the shaft, the transfer of the welded steel pipe segments into the tunnel, and tunnel grouting. Based on the space necessary to accommodate these activities, as well as the fact that tunneling would need to occur in two directions at the sharp turning point of the pipeline on West Silver Lake Drive (at the Redesdale North Shaft) and that a larger shaft would therefore be required in order to install the pipe elbow at this turning point, it has been determined that a single tunnel entry shaft at Redesdale North would be more appropriate in terms of limiting impacts rather than, as had been described in the Certified EIR, creating two separate entry shafts at Putnam and Redesdale South, where the size of the shafts, as well as the activities associated with launching the EPBM and tunneling, could result in complete closures of West Silver Lake Drive at these locations during extended portions of construction. Therefore, the Redesdale North Shaft would be used to launch the EPBM to tunnel both southward to the Redesdale South Shaft and northward to the Putnam Shaft.
To accommodate the assembly and launch of the EPBM and the other activities associated with tunneling, the Redesdale North Shaft would be circular in shape, about 40 feet in diameter, and about 95 feet deep. Excavating and stabilizing the shaft would require the use of heavy equipment within the shaft, extensive shoring, a cast-in-place concrete floor, and a cast-in-place concrete perimeter retaining wall for the entire depth of the shaft. In order to accomplish this excavation and stabilization task, lower the EPBM components into the shaft, lower and remove the pipe carrier and other equipment, and lift the muck haul carts, a 100-ton crawler crane would be stationed adjacent to the shaft throughout construction of the shaft and tunnel. Shaft and tunnel muck would be removed by the crane and placed in a temporary walled holding area at the surface, from which it would be continually loaded by an excavator into dump trucks and hauled off site. During the construction of the shaft itself, major disruptions to traffic on West Silver Lake Drive would occur, including lengthy closures of the roadway necessitated by safety concerns related to crane operations.
Page 8 Silver Lake Reservoir Complex Storage Replacement Project
During the actual tunneling process, precast concrete tunnel lining ring segments would be continually delivered to the site on flatbed trucks, offloaded by a separate 50-ton truck-mounted crane to a staging location near the shaft, and then lowered by the crane into the shaft as required to complete the tunnel lining rings. During the installation of the welded steel pipeline within the tunnel, pipe segments would be continually delivered to the site on flatbed trucks, offloaded by the 50-ton truck-mounted crane to a staging location, and then lowered by the crane into the shaft as required. Other support functions required within the Redesdale North construction zone would include offices and tunneling apparatus control rooms, shops, parts storage buildings, water storage tanks and groundwater settlement tanks, generators, grout mixer units, tunnel ventilation equipment, and miscellaneous storage areas.
To contain these various functions, the construction zone for the Redesdale North Shaft would extend from Balmer Drive on the north for approximately 600 feet southward along the west side of West Silver Lake Drive, as shown in Figure 3. The construction zone would be approximately 25 feet wide, extending eastward from the inner edge of the sidewalk located along the west side of West Silver Lake Drive. Through pedestrian access along the west side of the street would be unavailable during construction; however, sidewalk access would be maintained to the single-family residence fronting West Silver Lake Drive, just south of Balmer Drive.
The location of this construction site is not only necessary to support the activities at the Redesdale North Shaft, it also has the advantage of directly fronting a minimum number of residences on West Silver Lake Drive, and it would not block any driveway access. To accommodate this construction zone and still allow for the passage of vehicular traffic along West Silver Lake Drive, the roadway would first need to be widened to the east to maintain a single travel lane in each direction. However, no parking lane, as currently exists along the west side of West Silver Lake Drive, would be available along the length of the construction zone on either side of the street. The roadway widening would require removing the existing sidewalk along the east side of the street, but room for a new sidewalk would be provided by moving the existing reservoir complex property boundary fence eastward to the top of the actual side wall of Silver Lake Reservoir. The construction zone would be fenced, and a K-rail barrier would be placed along the edge adjacent to West Silver Lake Drive. Several vehicle entrances to the construction zone from West Silver Lake Drive would be provided.
Although West Silver Lake Drive adjacent to the Redesdale North construction zone would be reconfigured to continue to provide one travel lane in each direction, the tunnel entry shaft would nonetheless extend into the southbound lane due to the size and shape of the shaft. During the initial excavation of the shaft, this would require the closure of the southbound lane until a temporary bridge structure could be erected to span the shaft in the area where it intrudes into the traffic lane. This bridge would remain throughout the period of construction involving the shaft to allow for vehicle passage. However, due to potential hazards related to construction activity, sharp curves, and impeded sightlines, speed limits in the area of the Redesdale North construction zone would be reduced.
December 2013 Page 9 Source: LADWP 2013 Figure 3 I NOT TO SCALE Redesdale North Tunneling Shaft Silver Lake Reservoir Complex Storage Replacement Project
In addition, during construction, the boom from both the 100-ton crawler crane and the 50-ton truck-mounted crane would need to swing out over the traffic lanes to perform some operations because the steep slope located along the west edge of the construction zone would limit the range of the booms’ movement. As discussed above, for the 100-ton crawler crane, these operations would include supporting the excavation and stabilization of the shaft, lowering and removing the EPBM components and other equipment into the shaft, and lifting the muck haul carts from the shaft. For the 50-ton truck-mounted crane, these operations would involve offloading tunnel lining ring segments and pipe sections from trucks and lowering them into the shaft as needed. When these activities were actually occurring, traffic in both directions on West Silver Lake Drive adjacent to the construction zone, as well as pedestrian traffic on the sidewalk on the east side of the road, would need to be temporarily halted because of the potential safety hazard to motorists and pedestrians. As discussed above, the Redesdale North Shaft would be used to launch the EPBM and excavate both the tunnel southward to the Redesdale South Shaft and the tunnel northward to the Putnam Shaft. The activities involving the cranes at the Redesdale North Shaft, including the site preparation and shaft construction, would take place continually over approximately a 2.5-year period, throughout which frequent and potentially lengthy disruptions to traffic on West Silver Lake Drive would occur during construction hours, which, as discussed in the Certified EIR, may take place Mondays through Saturdays.
Redesdale South Shaft
Because it would not be used to launch the EPBM, remove material related to tunnel excavation, or install the tunnel lining, the Redesdale South Shaft would not need to support the same type and level of construction activity as the Redesdale North Shaft. It would serve as a receiving shaft for the EPBM that would have originated at the Redesdale North Shaft. The EPBM would be lifted from the shaft by a 100-ton crawler crane, disassembled, and transported back to the Redesdale North Shaft to initiate the tunneling to the Putnam Shaft. Since all materials related to the actual tunneling between the Redesdale North Shaft and the Redesdale South Shaft would originate at the north shaft, no delivery of tunneling materials would occur at the south shaft. However, since tunneling activities from the Redesdale North Shaft to the Putnam Shaft would be initiated immediately after the completion of the tunnel to the Redesdale South Shaft, space would be limited in the north shaft. Therefore, the actual welded steel pipe between the Redesdale North and South Shafts would probably be installed from the south shaft concurrently with the tunneling between Redesdale North and Putman. In this manner, the overall length of construction could be minimized compared to conducting all tunneling and pipe installation activities sequentially from only North Redesdale. The pipeline would also make a sharp turn to the southeast at the Redesdale South Shaft and rise in elevation to continue on to the connection with the Silver Lake Outlet Line.
To accommodate these various activities and spatial requirements, the shaft would be circular in shape, about 30 feet in diameter, and about 40 feet deep. As at the Redesdale North Shaft, excavating and stabilizing the shaft would require the use of heavy equipment within the shaft, extensive shoring, a cast-in-place concrete floor, and a cast-in-place concrete perimeter retaining wall for the entire depth of the shaft. A 50-ton truck-mounted crane would be used to support the excavation and stabilization of the shaft, lower and remove the pipe carrier and other equipment, and lower pipe segments into the shaft. Shaft muck would be placed in a temporary walled holding area at the surface, from which it would be loaded by an excavator into dump trucks and hauled off site. During the construction of the shaft itself, major disruptions to traffic on West Silver Lake Drive would occur, including lengthy closures of the roadway necessitated by safety concerns related to crane operations.
December 2013 Page 11 Introduction
During the installation of the welded steel pipeline within the tunnel, pipe segments would be continually delivered to the site on flatbed trucks, offloaded by the crane, and lowered into the shaft, with individual pipe sections transported into the tunnel by the self-propelled pipe carrier and welded to the preceding section of pipe. The Redesdale South construction zone would also support the pipeline installation from the shaft, located at the northeast corner of West Silver Lake Drive and Redesdale Avenue, to the beginning of the Silver Lake Outlet Line, located about 250 feet to the southeast. As discussed above, this segment of the pipeline would be constructed by means of an open trench because it could be installed at shallower depths compared to the tunneling segments.
To contain these functions, the Redesdale South construction zone would extend approximately 275 feet along West Silver Lake Drive to the east of Redesdale Avenue, as shown in Figure 4. The construction zone would be about 30 feet wide and, to avoid damage to existing mature trees located in the Silver Lake Recreation Center property, would extend southward from the curb along the north side of West Silver Lake Drive. The construction zone would be fenced, and a K-rail barrier would be placed along the edge adjacent to West Silver Lake Drive. The street would be narrowed to a single traffic lane adjacent to the Redesdale South construction zone, which would generally require a detour for either eastbound or westbound traffic throughout construction, which is expected to last nearly 3 years, including the open-trench pipeline installation connecting to the Silver Lake Outlet Line and supporting the construction of a regulator station (see below). In addition, similar to the conditions at the Redesdale North Shaft, the boom from the cranes must swing out over the traffic lanes to perform operations because the mature trees located immediately north of the shaft would limit the range of the boom’s movement. As discussed above, these operations would include supporting the excavation and stabilization of the shaft, retrieving the EPBM from the shaft, and offloading pipe sections from trucks and lowering them into the shaft. When these activities were actually occurring, traffic on West Silver Lake Drive adjacent to the construction zone would need to be temporarily halted because of the potential safety hazard to motorists.
After completion of the pipeline installation (including both the tunneling and open trench activities), the Redesdale South construction zone would continue to be used to support the construction of the regulator station, which is necessary to control water pressure at the Silver Lake Outlet Line. The regulator station and associated pipelines would occupy a footprint of approximately 30 feet by 45 feet in the lawn of the Silver Lake Recreation Center, north of the bypass line near its connection to the Silver Lake Outlet Line. In relation to the bypass pipeline alignment, no other location for the regulator station would be feasible because of the depth of the pipeline in the tunnel as it passes adjacent to other open areas of the SLRC bordering West Silver Lake Drive. The station would be buried below grade, and construction would require relatively substantial excavation work and concrete deliveries. The construction of the regulator station, as described in the Certified EIR, would take approximately 6 to 9 months to complete.
Page 12 Source: LADWP 2013 Figure 4 I NOT TO SCALE Redesdale South Tunneling Shaft Introduction
Putnam Shaft
The Putnam Shaft would function as a receiving shaft for the EPBM that would have originated at the Redesdale North Shaft. The EPBM would be lifted from the shaft by a 100-ton crawler crane, disassembled, and transported off site since the project tunneling activity would be complete. Since all materials related to the tunneling between the Redesdale North Shaft and the Putnam Shaft would originate at the Redesdale North Shaft, no delivery of tunneling materials would occur at the Putnam Shaft. In addition, the welded steel pipe between the Redesdale North and Putnam Shafts would be installed from the Redesdale North Shaft, where individual pipe sections would be transported into the tunnel by the self-propelled pipe carrier and welded to the preceding section of pipe. The pipeline would rise in elevation at the Putnam Shaft to continue on to the connection with the River Supply Conduit in Armstrong Avenue.
Because the Putnam Shaft supports no tunneling activities (other than the retrieval of the EPBM) and relatively minor pipeline installation activities, it would be smaller than either the Redesdale North or Redesdale South Shafts, and it would be rectangular in shape at about 20 feet by 30 feet, running longitudinally in the direction of the pipeline and the roadway. However, the Putnam Shaft would be 70 feet deep, and, as at the Redesdale North and Redesdale South Shafts, excavation and stabilization of the shaft would require the use of heavy equipment within the shaft, extensive shoring, a cast-in-place concrete floor, and a cast-in-place concrete perimeter retaining wall for the entire depth of the shaft. A 50-ton truck-mounted crane would be used to support the excavation and stabilization of the shaft and lower pipe segments and required equipment into the shaft. Shaft muck would be placed in a temporary walled holding area at the surface, from which it would be loaded by an excavator into dump trucks and hauled off site. During the construction of the shaft itself, major disruptions to traffic on West Silver Lake Drive would occur, including lengthy closures of the roadway necessitated by safety concerns related to crane operations.
To contain these functions, the Putnam Shaft construction zone would extend from Armstrong Avenue on the north approximately 350 feet southward along the east side of West Silver Lake Drive, as shown in Figure 5. The site would be about 25 feet wide, extending westward from the curb on the east side of the street. This would leave enough road width to maintain a single travel lane in each direction, but no parking lanes, as currently exist on both sides of West Silver Lake Drive, would be available along the length of the construction zone. In addition, three to four private driveways would be blocked for certain periods during construction. The construction zone would be fenced, and a K-rail barrier would be placed along the edge adjacent to West Silver Lake Drive. Construction activities at the Putnam Shaft area would last approximately 2 years, including connecting to the River Supply Conduit in Armstrong Avenue.
Similar to the conditions at the Redesdale North and Redesdale South Shafts, the boom from the cranes must swing out over the traffic lanes to perform operations to avoid swinging over residential properties located to the east of the construction zone. As discussed above, these operations would include supporting the excavation and stabilization of the shaft, retrieving the EPBM from the shaft, and offloading pipe sections from trucks and lowering them into the shaft. While these activities would be of a shorter total duration at the Putnam Shaft than at the Redesdale North or South Shafts, when they were actually occurring, traffic in both directions on West Silver Lake Drive adjacent to the construction zone would need to be temporarily halted because of the potential safety hazard to motorists.
Page 14 Source: LADWP 2013 Figure 5 I NOT TO SCALE Putnam Tunneling Shaft Introduction
In addition to the construction activities related to the tunneling shaft itself, the Putnam construction zone would also support the pipeline installation from the shaft northward approximately 225 feet to the connection to the River Supply Conduit. As discussed above, this segment of the pipeline would be constructed by means of an open trench because compared to the tunneling segments it would be installed at a shallower depth of about 30 feet. Because of the depth of excavation required and the necessary shoring activities, this open trench installation would take up to 6 months, occurring after the completion of tunneling activities at the site. Due to the location of the River Supply Conduit along the northern side of Armstrong Avenue and the depth of the excavation, the roadway may be narrowed to a single lane of through traffic for several months during the hours of construction. However, it is anticipated that the open trench would be covered with steel plates to allow for the passage of traffic during hours when construction would not be occurring.
Shaft Closures
After completion of the pipeline installation from the Redesdale North Shaft to the Putnam Shaft, the pipe segments connecting the two tunnel reaches (i.e., Redesdale North to Redesdale South and Redesdale North to Putnam) would be installed at the Redesdale North Shaft. After this connection is made, all equipment would be removed from the shaft, the upper 8 feet of the perimeter concrete retaining wall would be removed, and the shaft would be backfilled with soil- cement slurry to completely fill voids and provide an essentially non-compressive mass. The construction zone facilities, equipment, and barriers would be removed, the pavement restored, and West Silver Lake Drive and the adjacent sidewalks returned to their original alignments.
After completion of the connection to the River Supply Conduit, the upper 8 feet of the perimeter retaining wall at the Putnam Shaft would be removed, and the shaft would be backfilled with soil-cement slurry. The construction zone equipment and barriers would be removed and the pavement restored. After completion of the connection to the Silver Lake Outlet Line, the upper 8 feet of the perimeter retaining wall at the Redesdale South Shaft would be removed, and the shaft would be backfilled with soil-cement slurry. However, portions of the South Redesdale Shaft construction zone would continue to support the construction of the regulator station located in the lawn of the Silver Lake Recreation Center (see Figure 4). After completion of the regulator station, the construction zone equipment and barriers would be removed and the pavement restored.
Pressure Relief Station
In addition to the above facilities, which would be located generally adjacent to the SLRC, a relief station, as described in the Certified EIR, would be constructed south of the SLRC to release water in the case of excess buildup of pressure in the Silver Lake Outlet Line. This station would be necessary because the open-air reservoirs in the SLRC, which would be entirely bypassed by the new pipeline, would no longer function, as they currently do, to relieve excess pressure that may occur in the distribution system. The station would be located at the intersection of West Silver Lake Drive and Silver Lake Boulevard, approximately 0.25 miles south of the SLRC, where water could be diverted into an existing storm drain if required during an excess pressure event. The station would include a vault buried in Silver Lake Boulevard and the installation of approximately 100 feet of 12-inch diameter pipe, which would be constructed by open-trench method, crossing Silver Lake Boulevard. Construction of the relief station would take approximately 2 months, which would occur concurrently with construction of the bypass pipeline.
Page 16 Silver Lake Reservoir Complex Storage Replacement Project
Construction Activities and Sequencing
The bypass pipeline tunneling alignment, including the construction of the regulator station at the Silver Lake Recreation Center and the pressure relief station south of the SLRC, would take a total of approximately 3 years to complete. The basic nature and sequence of activities, some of which would overlap in time, would include:
Construction of the Redesdale North, Redesdale South, and Putnam Shafts and construction zones Tunneling with the EPBM, including the installation of the precast tunnel lining, from the Redesdale North Shaft to the Redesdale South Shaft Retrieval of the EPBM at the Redesdale South Shaft and return of the EPBM to the Redesdale North Shaft Installation of the welded steel pipe from the Redesdale South Shaft to the Redesdale North Shaft Tunneling with the EPBM, including the installation of the precast tunnel lining, from the Redesdale North Shaft to the Putnam Shaft Installation of the welded steel pipe from the Redesdale North Shaft to the Putnam Shaft Open-trench installation of the pipe from the Putnam Shaft to the terminus of the River Supply Conduit in Armstrong Avenue, including the connection of the lines Open-trench installation of the pipe from the Redesdale South Shaft to the beginning of the Silver Lake Outlet Line, including the connection of the lines Construction of the pressure regulator station near the Silver Lake Recreation Center Construction of the pressure relief station at the intersection of West Silver Lake Drive and Silver Lake Boulevard
Table 1 below indicates the basic construction activities, in approximate sequential order, for the bypass pipeline tunneling alignment, including a preliminary estimate of the start month and the duration of the activities.
December 2013 Page 17 Introduction
Table 1 Bypass Pipeline Tunneling Alignment Construction Activities START DURATION ACTIVITY MONTH (months) Mobilization, including equipment mobilization, materials acquisition, 1 8 and project staging areas Redesdale North Shaft site preparation, including: West Silver Lake Drive widening Construction zone fencing and barriers Support facilities construction 2 10 Shaft overburden and rock excavation Shaft cast-in-place floor slab and retaining wall Tunneling plant and EPBM assembly
Redesdale South Shaft site preparation, including: Construction zone fencing and barriers Support facilities construction 3 4 Shaft overburden and rock excavation Shaft cast-in-place floor slab and retaining wall
Putman Shaft site preparation, including: Construction zone fencing and barriers Support facilities construction 9 4 Shaft overburden and rock excavation Shaft cast-in-place floor slab and retaining wall
Redesdale North to Redesdale South tunnel excavation 12 2 Retrieval of EPBM from Redesdale South; disassembly of EPBM; 14 2 transport of EPBM to Redesdale North; reassembly of EPBM Redesdale South to Redesdale North pipeline installation 14 2 Redesdale North to Putnam tunnel excavation 16 5 Redesdale South shaft piping installation; shaft closure 16 4 Retrieval of EPBM at Putnam; disassembly of EPBM; transport of 21 1 EPBM off site Redesdale North to Putnam pipeline installation 21 5 Redesdale South open trench installation pipeline to Silver Lake 25 3 Outlet Line Redesdale North Shaft plant removal; shaft piping installation; shaft 26 2 closure; site restoration Putnam shaft piping installation; connection to River Supply Conduit; 27 6 shaft closure; site restoration Regulator Station at Silver Lake Recreation Center; site restoration 28 8 Pressure Relief Station at West Silver Lake Drive and Silver Lake 34 2 Boulevard Demobilization 36 1
Page 18 Silver Lake Reservoir Complex Storage Replacement Project
Construction Quantities
The bypass line tunnel construction described above would entail the excavation of a tunnel approximately 4,900 feet in length, including about 1,200 feet between the Redesdale North Shaft and the Redesdale South Shaft, and 3,700 feet between the Redesdale North Shaft and the Putnam Shaft. The tunnel would include a 10-foot diameter precast concrete lining, within which a 66-inch diameter welded steel pipe would be installed. The bypass pipeline tunneling alignment would also involve about 250 feet of conventional open-trench pipe installation between the Redesdale South Shaft and the start of the Silver Lake Outlet Line and about 225 feet of open-trench pipe installation between the Putnam Shaft and the terminus of the River Supply Conduit at Armstrong Avenue. Additionally, about 100 feet of open trench pipe installation would occur from West Silver Lake Drive across Silver Lake Boulevard for the pressure relief station.
This work would generate a total of about 41,450 cubic yards of excavated material, all of which would be hauled by trucks to an off-site disposal facility. About 26,000 cubic yards of concrete or slurry, which would be delivered by truck, would be required for structures (e.g., retaining walls), thrust block encasements, slurry backfills, and other purposes.
About 15,200 one-way truck trips would be required throughout construction to deliver and remove construction equipment and support facilities, deliver material and components, deliver concrete and slurry, and haul away excavated material, with each inbound and each outbound trip counted as a one-way trip. The number of truck trips per day would vary substantially during the project, depending on the type, number, and duration of activities occurring in a given period. Based on a preliminary breakdown of the construction schedule and tasks, the number of daily peak truck trips would range between about 75 and 80 for about a 1-month period. The lengthiest peak period involving relatively substantial truck traffic would be during the tunneling between the North Redesdale Shaft and the Putman Shaft, when an average of about 45 daily truck trips would occur over a consecutive 5-month period.
The number of pieces of operating equipment (i.e., cranes, excavators, generators, etc., but excluding trucks, which are accounted for separately under truck trips) would also vary during construction, depending on the type, number, and duration of activities occurring in a given period. Based on a preliminary breakdown of the construction schedule and tasks, the daily peak number of on-site operating equipment would be about 40 for a 1-month period during the simultaneous excavation of the tunnel between the North Redesdale Shaft and the South Redesdale Shaft and the excavation of the Putnam Shaft. Outside of this peak period, the number of pieces of on-site equipment would be fewer than 30 per day.
The number of construction personnel on site would likewise vary during construction, depending on the type, number, and duration of activities occurring in a given period. Based on a preliminary breakdown of the construction schedule and tasks, the daily peak number of personnel would be for about a 1-month period during the simultaneous excavation of the tunnel between the North Redesdale Shaft and the South Redesdale Shaft and the excavation of the Putnam Shaft, when an average of about 35 personnel would be on site each day. Outside of this peak period, the number of on-site personnel would be 30 or fewer per day.
December 2013 Page 19 Introduction
1.4 Reconsideration of In-Reservoir Pipeline Alignment
Background
Based on the magnitude of the construction effort described above related to tunneling for the bypass pipeline, a number of factors have contributed to a reconsideration of the potential to route the interconnecting pipeline between the River Supply Conduit and the Silver Lake Outlet Line through, rather than around, the SLRC. The most important of these factors is that since the approval of the bypass pipeline tunneling alignment in 2006, Silver Lake Reservoir has been removed from service as a drinking water storage facility to prevent the formation of bromate in the water supply. Although Silver Lake Reservoir remains filled with non-potable water, it no longer provides a physical link between the River Supply Conduit and the Silver Lake Outlet Line, as it did when the bypass pipeline was originally proposed and studied in the Certified EIR. This physical link is currently provided solely via Ivanhoe Reservoir, which is supplied by the River Supply Conduit and connected to the Silver Lake Outlet Line via a separate pipeline. Although the loss of Silver Lake Reservoir has reduced local storage capacity that had been utilized to meet daily fluctuations in demand and provide water during emergency shortages, based on expanded water conservation programs, Ivanhoe Reservoir (which has been covered with shade balls to curtail the formation of bromate) provides the capability to respond to most circumstances on an interim basis during construction of the Headworks Reservoir, which will permanently replace the storage function of the SLRC. The physical isolation of Silver Lake Reservoir from the drinking water system and the resultant lack of dependence on the reservoir for drinking water supply and distribution have now created a situation under which the reservoir could be drained to allow for construction of the pipeline within the reservoir without compromising the operational integrity of the system.
The assumptions regarding the minimum acceptable operating pressure for the interconnecting pipeline have also changed since the Certified EIR was prepared. In addition to being a critical factor relative to the delivery of water through the transmission system, the operating pressure of a pipeline also functions as a force against the intrusion of contaminants that could potentially penetrate the pipeline through small openings. During early project planning stages, a pressure of 10 pounds per square inch (psi) reflected a highly conservative assumption in relation to California Department of Public Health requirements for the protection of drinking water mainlines from the intrusion of contaminants. This assumption regarding minimum pressure was a primary factor in the selection of the tunneling (rather than trenching) approach to the pipeline construction because of the depth of installation to achieve the minimum pressure. However, California Department of Public Health requirements can actually be met at pressures as low as 5 psi. A 5 psi pressure requirement allows for a depth of installation that would make trenching (rather than tunneling) feasible within certain limits of the proposed bypass line alignment. South of Hawick Street, adjacent to the northwest corner of Silver Lake Reservoir, the depth of installation required to maintain 5 psi could not be feasibly achieved by means of trenching, and tunneling would be required. However, north of Hawick Street, trenching would represent a feasible means for pipeline installation while still maintaining minimum operational pressure in the line. In addition, the required minimum pressure could also be achieved with relatively minimal trenching within Silver Lake Reservoir itself because of the lower elevation of the reservoir floor.
While cross-contamination of the water supply associated with placing the pipeline within a reservoir containing non-potable water is a potential concern, several characteristics of the proposed pipeline would essentially eliminate the potential for cross-contamination. The use of welded steel pipe with welded joints, as is proposed for the project, would largely eliminate
Page 20 Silver Lake Reservoir Complex Storage Replacement Project potential seepage points. The steel pipe used throughout the project would also have a cement mortar outer coating and inner lining that would strengthen the pipe and provide an additional barrier of separation. Furthermore, the sections of pipeline that would be located within the reservoir would also be nested within an outer welded steel pipe sleeve that would in turn be encased in concrete. The use of these multiple barriers of separation would prevent cross- contamination of drinking water contained within a pipeline located in a reservoir containing non- potable water, even under circumstances when water pressure in the line was temporarily reduced below normal minimum values.
While the removal of Silver Lake Reservoir from service and a reevaluation of the operating pressure requirements for the interconnecting pipeline have provided an opportunity, from an operational perspective, to reconsider an alternative alignment that routes the pipeline through the SLRC, recent developments related to pipeline construction in the Silver Lake community have also prompted this reconsideration. The construction of the Lower Reach River Supply Conduit Unit 4 (which is the southernmost link of the trunk line that will transport water from the Headworks Reservoir in Griffith Park to the vicinity of the SLRC) created substantial controversy in the Silver Lake community related to traffic disruption, pedestrian safety, air pollution, noise, and temporary loss of access to property. In light of the concerns associated with the construction of the River Supply Conduit and the magnitude of the construction effort for the bypass pipeline tunneling alignment (together with the changes to the operational conditions that had previously influenced the selection of the tunneling approach), LADWP has endeavored to explore an alternative means to achieve the required pipeline interconnection between the River Supply Conduit and the Silver Lake Outlet Line.
Therefore, the intent of an alternative alignment would be to minimize, to the extent possible, construction activity within public roadways; the quantity of earthwork, equipment, and truck trips; and the duration of construction. An alignment that would route the pipeline within Silver Lake Reservoir would achieve these objectives by minimizing in-street construction and reducing the magnitude and duration of construction. Some construction within public roadways would still be required to extend a pipeline from the terminus of the River Supply Conduit in Armstrong Avenue to the SLRC, but routing the line through Silver Lake Reservoir would help minimize the extent of construction activities in public roadways and the general magnitude of the construction effort. In order to reach Silver Lake Reservoir from the River Supply Conduit, the pipeline would still need to be routed within West Silver Lake Drive between Armstrong Avenue and the northwest corner of the reservoir, where the line could turn eastward, away from the road and into the reservoir, as shown in Figure 6.
Even though some in-street construction would still be required, the in-reservoir pipeline alignment would nonetheless help minimize the extent and magnitude of disruption to local roadways when compared to an alignment that entirely bypasses the reservoir by means of tunneling. This approach would also generally help reduce the total volume of excavation, the number of truck trips, and the overall duration of construction. The in-reservoir pipeline alignment alternative would require temporarily draining Silver Lake Reservoir during construction. However, based on outreach by LADWP, public opinion in the surrounding community is generally supportive of temporarily draining the reservoir as a means of limiting the magnitude and duration of construction and the extent of disruption on local roadways.
December 2013 Page 21 Source: LADWP 2013 Figure 6 In-Reservoir Pipeline Alignment
I Silver Lake Reservoir Complex Storage Replacement Project
In-Reservoir Pipeline Alignment
Open-trench pipeline construction does not require launching or receiving shafts or the long- term use of stationary construction zones necessary to support the various activities associated with tunneling. An open-trench installation is instead characterized by construction activities at the surface that move forward along the pathway of the pipeline as sections of pipe are installed. The general process for open-trench construction in a roadway involves a number of sequential steps. First, the roadway adjacent to the defined construction zone would be reconfigured and/or restriped, as appropriate, to allow for continued safe passage of vehicles during construction. The construction zone would then be segregated from the roadway and sidewalk with fencing and, adjacent to the traffic lanes, with a K-rail barrier. I-beam piles, which would be used to support the shoring system required to stabilize the trench side walls, would be placed in predrilled holes located along the perimeter of the area to be trenched, and the pavement would be saw cut along the perimeter to provide a clean edge. The road pavement within the trench area would then be demolished with an excavator, and the debris would be loaded into dump trucks to be hauled off site. The trench would then be excavated, which would include the installation of a vertical shoring system to provide stability as the trench is progressively deepened. The excavated material would be loaded into dump trucks and hauled off site.
Once a trench of sufficient length has been excavated, welded steel pipe sections would be delivered to the site on a flatbed truck and offloaded to be placed in the trench. A 40-foot long section of welded steel pipe would be lowered into the trench and welded to the preceding pipe section. When several sections of pipe have been installed, the shoring structures supporting the trench adjacent to the pipe would be removed and the trench would be backfilled with soil- cement slurry to quickly and completely fill voids and provide an essentially non-compressive mass in the trench. This would occur at the same time that trenching and pipe installation work would continue in the forward areas of the trench. A temporary bulkhead structure would be placed across the trench to contain the slurry so that it does not interfere with continued construction in the forward portions of the trench. The entire process of installing three to four sections of pipe, including backfilling of the trench, would take approximately 10 to 15 work days to complete. This method of continually backfilling the trench once a portion of the pipeline is complete helps limit the size of the active construction area and the extent of open trench at a given time. After completion of the pipeline installation in the defined construction zone, including the removal of the shoring structures and the backfilling of the trench, the fence and the traffic barriers would be removed, and the roadway within the construction zone would be repaved and restriped as necessary. Based on this construction process, the required depth of installation for the interconnecting pipeline, and an analysis of the site conditions on West Silver Lake Drive, preliminary plans for the trenching operations and the supporting construction zones have been developed.
The construction for the in-reservoir pipeline alignment would be subdivided into three primary work areas, as shown in Figures 7 and 8. Work Area 1 would extend along the east side of West Silver Lake Drive from Armstrong Avenue on the north to approximately Tesla Avenue on the south. Work Area 2 would extend along the east side of West Silver Lake Drive from Tesla Avenue on the north to approximately 300 feet north of Hawick Street, adjacent to the northwest corner of Silver Lake Reservoir. Work Area 3 would encompass an area contained essentially within the SLRC and primarily within Silver Lake Reservoir itself, extending southward along the west side of the reservoir and terminating just north of the reservoir dam. As currently planned, the work within these areas would proceed as described below. While the exact sequencing of
December 2013 Page 23 Introduction the work between the different zones may change, the general type and extent of work and the construction processes required in each zone would remain basically as described.
Prior to initiating actual construction work related to the interconnecting pipeline, Ivanhoe Reservoir will be removed from service as a drinking water storage facility in late 2014, as described above under the bypass pipeline tunneling alignment. After removal from service, it will remain an open reservoir containing non-potable water. Silver Lake Reservoir would then be drained to facilitate construction of the pipeline. The water in Silver Lake Reservoir would be pumped into Ivanhoe Reservoir to refill Ivanhoe Reservoir following removal of the shade balls and the severing and/or modifications of the reservoir inlet and outlet. Water that would not be pumped into Ivanhoe Reservoir would be drained, depending on water quality, into the storm system or sewer system. It would take approximately 3 months for the reservoir to be completely drained and dried out prior to the start of construction.
Work Area 1
Once the reservoir was drained and dried out, work is anticipated to begin simultaneously in Work Areas 1 and 3. Work Area 1 would be approximately 28 feet wide, extending westward from the face of the curb located along the east side of West Silver Lake Drive. This would leave enough road width to maintain a single vehicle travel lane in each direction. However, no parking lanes, as currently exist on both sides of West Silver Lake Drive, would be available along the length of the construction zone. Work Area 1 would front eight residential driveways on the east side of the street, but vehicular access to the driveways would generally be maintained throughout construction since a limited segment of trench would be open at a given time. Even in instances where an open trench fronted a driveway, access would normally be maintained with steel plates spanning the trench.
From an existing vault located in West Silver Lake Drive near Armstrong Avenue, an approximately 8.5-foot wide trench would be excavated and shored to install pipe connecting to the River Supply Conduit, which is located along the northern side of Armstrong Avenue. This trench would be approximately 30-feet deep and 100-feet long. Because of the depth of excavation required and the necessary shoring activities, this open trench installation would take up to 6 months. This installation north of the vault would be similar to that which would occur under the bypass pipeline tunneling alignment discussed above.
Southward of the vault, an approximately 8.5-foot wide trench would also be excavated and shored. The trench would need to be up to about 30 feet deep where the new pipeline would connect to the existing vault structure. However, the elevation of the pipe would rise within a short distance of this connection, and the trench within the remainder of Work Area 1 would generally be less than 15 feet deep. The trenching and pipe installation work south of the vault would occur concurrently with the work north of the vault to minimize the total length of construction in Work Area 1.
As the trench was excavated, the material would be loaded into dump trucks parked adjacent to the trench within the fenced construction zone and hauled via West Silver Lake Drive into Silver Lake Reservoir (which would have been drained), where it would be spread on the bottom of the reservoir. After all the pipe had been installed and the trench backfilled in Work Area 1, the construction zone barriers would be removed, and the pavement would be restored. The total duration of construction in Work Area 1 is anticipated to last approximately 6 months, including the repaving of the roadway.
Page 24 Source: LADWP 2013 Figure 7 Work Areas 1 and 2
I Source: LADWP 2013 Figure 8 Work Area 3
I Silver Lake Reservoir Complex Storage Replacement Project
Work Area 2
After completion of the pipe installation in Work Area 1 and restoration of the construction zone, work is anticipated to begin in Work Area 2. The width of the roadway between the existing curbs narrows from approximately 50 feet in Work Area 1 to approximately 38 feet in Work Area 2. In order to provide adequate width within the construction zone to complete the trenching and pipe installation, the remaining roadway would not be wide enough to accommodate two-way traffic. Therefore, throughout construction in Work Area 2, which would last approximately 4 months, vehicle traffic north of Hawick Street would be limited to a one-way northbound configuration. This one-way configuration would continue northward to Armstrong Avenue to prevent detours of southbound traffic around Work Area 2 through the adjoining residential neighborhoods. No parking lane, as currently exists on the west side of West Silver Lake Drive, would be available along the length of Work Area 2 during construction; on-street parking would be again available north of Tesla after the completion of construction in Work Area 1. During construction in Work Area 2, the walkway along the east side of West Silver Lake Drive would need to be temporarily removed. Pedestrian traffic in this area would be detoured during construction to the existing maintenance road along the west side of Ivanhoe Reservoir before being diverted back to Tesla Avenue near its intersection with West Silver Lake Drive (see Figure 7). Because it would run adjacent to the SLRC along the east side of West Silver Lake Drive, Work Area 2 would not directly interfere with any driveways along the west side of the street.
Beginning at the north end of Work Area 2, an approximately 8.5-foot wide trench would be excavated and shored, continuing from the pipeline installation in Work Area 1. The trench would range from approximately 15 feet deep at the north end to 25 feet deep at the south end, where the pipeline would turn into the reservoir property. Similar to the construction in Work Area 1, as the trench was excavated, the material would be loaded into trucks parked adjacent to the trench within the fence line and hauled directly from the construction zone into Silver Lake Reservoir, where it would be spread on the bottom of the reservoir. In this manner, no on-road truck trips would be required in relation to hauling in Work Area 2.
At the south end of Work Area 2, the pipeline would be joined to the pipeline that had been previously installed in Work Area 3 (see below). After all the pipe had been installed and the trench backfilled in Work Area 2, the construction zone barriers would be removed, and the road pavement and walkway along the east side of the street would be restored. The total duration of construction in Work Area 2 is anticipated to last approximately 4 months. The total time for in- street construction under the open-trench alignment would be approximately 10 months. The entirety of West Silver Lake Drive would then be open to traffic with two travel lanes in each direction and on-street parking as currently exists.
Work Area 3
At the same time work was initiated in West Silver Lake Drive, work would also begin in Work Area 3, where the new pipeline would turn eastward from West Silver Lake Drive into the SLRC. Similar to the work within Work Areas 1 and 2, the new pipeline would be installed by means of trenching, but in the lawn area between West Silver Lake Drive and Silver Lake Reservoir rather than in the roadway. The regulator station, which, as discussed above, is necessary to control water pressure at the Silver Lake Outlet Line, would be located adjacent to the pipeline where it enters the west side of the reservoir. During trenching, the walkway on the east side of the street would be severed, but pedestrian traffic would be detoured around the trenching operations in a manner that continuous access along West Silver Lake Drive would be
December 2013 Page 27 Introduction maintained (including the temporary redirection of pedestrians along the Ivanhoe Reservoir maintenance road during work in Work Area 2).
Beginning at the north end of the construction zone, an approximately 8.5-foot wide trench would be excavated and shored in the lawn area of the SLRC. The trench would be approximately 25 feet deep. As the trench was excavated, the material would be loaded into dump trucks and transported via the existing Silver Lake Reservoir maintenance road into the reservoir and stockpiled until needed for backfilling the trench. In this manner, no on-road truck trips would be required in relation to hauling in Work Area 3. The initial pipe section would be joined to the final pipe section installed in Work Area 2 (see above). The trench crossing the lawn from West Silver Lake Drive to Silver Lake Reservoir would be approximately 150 feet in length, which would entail approximately 4 pipe segments.
After entering the reservoir, the pipeline installation would continue southward along the west side of the reservoir. A relatively minor amount of trenching work (an average of about 10-feet in depth) would be required to install the pipe in the reservoir to maintain an appropriate slope in relation to the transmission of water in the pipeline and the interconnection to the Silver Lake Outlet Line. The soil excavated during the pipe installation within the reservoir would be spread on the floor of the reservoir and would not therefore require transport off site. As discussed above, the welded steel pipeline actually installed within Silver Lake Reservoir would be nested within an outer welded steel pipe sleeve that would in turn be encased in concrete to provide additional barriers of separation to prevent cross-contamination of the drinking water supply from the non-potable water stored in the reservoir. The interconnection to the Silver Lake Outlet Line would occur at the south end of the reservoir via an existing pipeline that passes beneath the reservoir dam, rather than within West Silver Lake Drive, as would be required under the bypass pipeline tunneling alignment. The total duration of the pipeline installation in Silver Lake Reservoir, including demobilization of the staging areas in the reservoir, is anticipated to last approximately 9 months, at which time the reservoir would be refilled. It would take about one month to completely refill the reservoir to pre-construction levels.
Pressure Regulator and Pressure Relief Station
After the completion of the pipeline installation in the lawn area between West Silver Lake Drive and Silver Lake Reservoir, work would begin building the regulator station. Unlike the approved bypass pipeline tunneling alignment, under which no potential locations for the regulator station exist other than the lawn of the Silver Lake Recreation Center, the in-reservoir pipeline alignment provides an opportunity to locate the regulator station within the SLRC property, thereby avoiding the recreation center property. The regulator station would be located in the lawn area and on the reservoir embankment in the northwest corner of Silver Lake Reservoir, as shown in Figure 8. This location also provides an opportunity to collocate the required pressure relief station with the regulator station, from which water could be released directly to the reservoir if necessary during an excess pressure event. This collocation would eliminate the construction of the relief station at the intersection of West Silver Lake Drive and Silver Lake Boulevard, as would be required under the approved bypass pipeline tunneling alignment discussed above. (Under the bypass pipeline tunneling alignment, the relief station could not be similarly collocated with the regulator station at the Silver Lake Recreation Center because the release of water into the reservoir in the event of excess buildup of pressure could not be achieved without pumping.)
The regulator station would be buried below grade level where it would be located within the lawn area. The material excavated for the regulator station would be spread within Silver Lake
Page 28 Silver Lake Reservoir Complex Storage Replacement Project
Reservoir. The excavation for the regulator station and the construction and sealing of the primary structure would occur within the timeframe of the pipe installation in the reservoir itself. This would allow for the reservoir to be refilled once the in-reservoir pipeline was complete, even though work on the interior of the regulator station would continue for several more months. Following completion of construction of the regulator station, the lawn area between West Silver Lake Drive and Silver Lake Reservoir disturbed during construction would be revegetated. Construction activity for the regulator station would take place entirely within the SLRC. The duration of construction for the regulator station, including excavation, the construction of the concrete structure, the installation of equipment, and pipeline connections, is anticipated to last approximately 12 months. Silver Lake Reservoir is expected to be completely drained for approximately 12 months.
Construction Activities and Sequencing
The in-reservoir pipeline alignment, including the construction of the regulator/relief station, would take a total of approximately 18 months to complete. The basic nature of activities, some of which would overlap in time, would include:
Draining of Silver Lake Reservoir Trenching and installation of the pipeline along West Silver Lake Drive from the River Supply Conduit (in Armstrong Avenue) to Tesla Avenue (Work Area 1) Trenching and installation of the pipeline within the SLRC property between West Silver Lake Drive and the Silver Lake Reservoir (Work Area 3A) Excavation for and construction of pressure regulator/relief station primary structure (Work Area 3A) Trenching and installation of the pipeline, including concrete-encased double-walled welded steel pipe, within Silver Lake Reservoir and connection to Silver Lake Outlet line via existing pipeline at south end of reservoir (Work Area 3B) Trenching and installation of the pipeline along West Silver Lake Drive from Tesla Avenue to the turning point into the reservoir complex, approximately 300 feet north of Hawick Street (Work Area 2) Refilling of Silver Lake Reservoir Installation of equipment and pipeline connections at pressure regulator/relief station
Table 2 below indicates the basic construction activities, in approximate sequential order, for the in-reservoir pipeline alignment, including a preliminary estimate of the start month and the duration of the activities.
December 2013 Page 29 Introduction
Table 2 In-Reservoir Pipeline Alignment Construction Activities START DURATION ACTIVITY MONTH (months) Drain Silver Lake Reservoir and mobilization, including equipment 1 3 mobilization and materials acquisition Trench and install pipeline in Work Area 1 4 6 Trench and install pipeline in Work Area 3A 4 2 Pressure regulator/relief station in Work Area 3A 6 12 Trench and install pipeline in Work Area 3B (within Silver Lake 4 9 Reservoir) Trench and install pipeline in Work Area 2 10 4 Refill Silver Lake Reservoir 13 1 Demobilization 18 1
Construction Quantities
The in-reservoir pipeline alignment described above would entail the installation of approximately 4,600 feet of 66-inch diameter welded steel pipe. This would include about 1,600 feet of in-road trenching on West Silver Lake Drive between Armstrong Avenue and the northwest end of Silver Lake Reservoir, and about 3,000 feet of pipeline within the SLRC, including about 150 feet of trenching outside the reservoir and 2,850 feet of pipeline trenching within the reservoir.
This work would generate a total of about 27,450 cubic yards of excavated material. All this material would be temporarily stockpiled within the drained Silver Lake Reservoir to be used as backfill material or would be permanently spread on the reservoir bottom. About 7,500 cubic yards of soil-cement slurry, which would be delivered by truck, would be required for backfilling the trenches, and about 550 cubic yards of concrete would be required for the regulator station structure.
To deliver and remove construction equipment and support facilities, deliver material and components, deliver concrete and slurry, and haul away excavated material, about 4,500 one- way truck trips would be required throughout construction, with each inbound and each outbound trip counted as a one-way trip. The number of truck trips per day would vary during construction, depending on the type and duration of activities occurring in a given period. Based on a preliminary breakdown of the construction schedule and tasks, the daily peak number of truck trips would reach about 30 for a 10-month period when the work in Work Areas 1 or 2 would be conducted simultaneously with the work in Work Area 3. Outside of this peak period, on-road trucks trips would generally average about 2 per day.
The number of pieces of operating equipment (e.g., cranes, excavators, generators, on-site dump trucks, but excluding on-road trucks, which are accounted for separately under truck trips) would also vary throughout construction of the project, depending on the type and duration of activities occurring in a given period. Based on a preliminary breakdown of the construction schedule and tasks, the daily peak number of pieces of on-site operating equipment would be about 16 for the 10-month period when the work in Work Areas 1 or 2 would be conducted
Page 30 Silver Lake Reservoir Complex Storage Replacement Project simultaneously with the work in Work Area 3. Outside of this peak period, the number of pieces of on-site daily operating equipment would average about 8.
The peak of on-site construction personnel would also occur during the 10-month period when the work in Work Areas 1 or 2 would be conducted simultaneously with the work in Work Area 3, during which an average of about 50 personnel would be present each day. Outside of this peak period, on-site personnel would average about 25 per day.
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Page 32 Silver Lake Reservoir Complex Storage Replacement Project
SECTION 2 ENVIRONMENTAL IMPACT ASSESSMENT
2.1 Land Use
The SLRC is located in the community of Silver Lake and consists of LADWP-owned Silver Lake and Ivanhoe Reservoirs and related facilities. The SLRC is approximately 127 acres in size, including 101 acres occupied by LADWP facilities, primarily Silver Lake and Ivanhoe Reservoirs, 2 acres leased to the City of Los Angeles Department of Recreation and Parks for the Silver Lake Recreation Center and dog park south of the Silver Lake Reservoir Dam, and 1 acre occupied by the Silver Lake neighborhood nursery school. The SLRC is zoned OS and is designated Open Space (OS) in the City’s General Plan Land Use Element. The project site is part of the Silver Lake-Echo Park Community Plan.
Construction of the bypass pipeline tunneling alignment described in the Certified EIR would be consistent with the OS land use designation for the SLRC. Construction activities would include launching and receiving pits in West Silver Lake Drive for the bypass tunnel, open trench construction at Armstrong Avenue and West Silver Lake Drive and on West Silver Lake Drive near the Silver Lake Recreation Center, and ground disturbance for the regulator station in the grassy area south of the Silver Lake Reservoir Dam, also near the Silver Lake Recreation Center. In addition, approximately 100 feet of open trench construction would be necessary at the intersection of West Silver Lake Drive and Silver Lake Boulevard for a pressure relief station. Due to the temporary nature of construction activities, the Certified EIR concluded that construction of the bypass pipeline tunneling alignment would not conflict with existing land uses at the site, disrupt or divide the physical arrangement of an existing community, or conflict with adopted environmental goals or policies contained in applicable plans. Although construction of the regulator station would temporarily restrict public access to a portion of the Silver Lake Recreation Center property, the Certified EIR concluded that the impact to recreation would not be significant because of the short-term duration of construction activities.
The Certified EIR concluded that long-term operation of the bypass pipeline tunneling alignment, which would consist of subterranean structures, would be consistent with historical and current uses of the SLRC for water supply and distribution. Therefore, project operation would not conflict with existing land uses or disrupt or divide the physical arrangement of the Silver Lake community. Further, it would have the beneficial impact of allowing Silver Lake and Ivanhoe Reservoirs to remain open reservoirs in perpetuity, which would be consistent with the Open Space (OS) land use designation of the SLRC. Additionally, during operation, the SLRC would remain capable of meeting the recreation goals identified in the General Plan and the Silver Lake-Echo Park Community Plan, and no elements of the bypass line tunnel and regulator station would prevent future recreational use in and around the SLRC.
Similarly, construction of the in-reservoir pipeline alignment addressed in this addendum would not conflict with existing land uses at the site, disrupt or divide the physical arrangement of an existing community, or conflict with adopted environmental goals or policies contained in applicable plans. Under the in-reservoir pipeline alignment, construction activities would take place mostly within the SLRC property boundaries. Although it would temporarily require that Silver Lake Reservoir be drained, this approach would minimize disruption to West Silver Lake Drive. It would also reduce the overall duration of construction by half, from about 36 months to about 18 months. Under the in-reservoir pipeline alignment, the regulator station would be located in the northwest corner of the Silver Lake Reservoir embankment, which is not currently
December 2013 Page 33 Introduction open to public access, and construction activities for the regulator station would not temporarily restrict public access to the Silver Lake Recreation Center property. Pedestrian access around the SLRC property would be maintained throughout construction. Implementation of the in- reservoir pipeline alignment would accomplish the community’s long-term goal of retaining Silver Lake and Ivanhoe Reservoirs as permanent open non-potable reservoirs. Additionally, during operation, the SLRC would remain capable of meeting the recreation goals identified in the General Plan and the Silver Lake-Echo Park Community Plan, and no elements of the in- reservoir pipeline alignment would prevent future recreational use in and around the SLRC. Therefore, the land use impacts of the in-reservoir pipeline alignment would be no greater than those described in the Certified EIR.
2.2 Earth Resources
The SLRC lies within the lower elevations of the Santa Monica Mountains, northwest of downtown Los Angeles. Soils at the SLRC generally consist of silty and sandy fill materials and quaternary alluvium to a depth of approximately 40 to 43 feet below ground surface. Groundwater was encountered at a depth of approximately 25 feet below ground surface. The SLRC is not mapped as an Alquist-Priolo Special Study Fault Zone; however, several small faults were exposed during the excavation and grading for the renovated dam for Silver Lake Reservoir in 1975 and 1976. One is a north-northeast trending, 350-foot-long fault with approximately 7 feet of offset along the outlet line near the western dam abutment. The second is an approximately 100-foot-long fault that was mapped approximately 50 feet southeast of the intersection of Redesdale Drive and West Silver Lake Drive. Additionally, West Silver Lake Drive is mapped as a liquefaction zone, and there is a landslide hazard zone mapped near the intersection of West Silver Lake Drive and Redesdale Drive.
Due to the presence of mapped geologic hazards in locations where the bypass pipeline tunneling alignment would be constructed, the Certified EIR concluded significant impacts would occur related to earth resources, and mitigation measures are required to be implemented. Specifically, ground disturbing activities would create soil erosion and runoff sedimentation, and the Redesdale North Tunneling Shaft would be subject to seismic hazards. With implementation of mitigation, the Certified EIR concluded that the impacts of the bypass pipeline tunneling alignment would be reduced to a less than significant level.
The Certified EIR concluded that long-term operation of the bypass pipeline tunneling alignment would not impact earth resources because the facilities would be constructed to comply with the City’s seismic safety standards.
Consistent with the Certified EIR, construction of the in-reservoir pipeline alignment addressed in this addendum would also create soil erosion and runoff sedimentation during ground disturbing activities. Therefore, the in-reservoir pipeline alignment would be required to implement mitigation measure ER-1 from the Certified EIR. However, construction of the in- reservoir pipeline alignment would not involve the use of the Redesdale North Tunneling Shaft. Trenching activity would occur farther north along West Silver Lake Drive outside of this geologic hazard zone. Therefore, implementation of mitigation measure ER-2 would not be required for the in-reservoir pipeline alignment to reduce impacts of seismic hazards to a less than significant level. During operation, similar to the bypass pipeline tunneling alignment, normal operation of the in-reservoir pipeline alignment at the SLRC would not impact earth resources. Therefore, the earth resources impacts of the in-reservoir pipeline alignment would be no greater than those described in the Certified EIR.
Page 34 Silver Lake Reservoir Complex Storage Replacement Project
2.3 Water Resources
The SLRC stores treated drinking water from the Los Angeles Aqueducts, Colorado River, State Water Project, and local water wells. Water is conveyed to the SLRC via the River Supply Conduit. The water stored in the SLRC is part of the citywide water distribution system that currently serves the potable and emergency water supply demands of portions of central and east Los Angeles. Both reservoirs in the SLRC have steep concrete banks, and there is no shoreline or emergent vegetation. Silver Lake Reservoir has soil over most of the reservoir bottom. Ivanhoe Reservoir has a concrete bottom. There are no fish or vegetation within either reservoir. Surface water resources at the SLRC consist of episodic storm water runoff caused by precipitation. However, to protect the quality of the water contained within the SLRC, the reservoirs themselves were constructed and situated so that precipitation that falls outside the reservoirs is routed away from the reservoirs by surface drains located on the east and west sides of each reservoir.
The Certified EIR concluded that short-term impacts to surface water quality could occur during the construction phase of the bypass pipeline tunneling alignment due to storm water runoff from the construction sites. The impact would be reduced to a less than significant level with implementation of mitigation, which would include preparation and implementation of a Storm Water Pollution Prevention Plan. There would be no water quality or groundwater supply impacts associated with the conversion of the SLRC from drinking water storage to open non- potable reservoirs.
During operations, the bypass line tunnel facilities would be located below ground. They would not be exposed to storm water, and, therefore, would not adversely impact storm water runoff or water quality. The Certified EIR also concluded that the impact to groundwater would be less than significant as there would be a nominal change in impervious surface area by locating most of the facilities within developed areas, primarily within West Silver Lake Drive. Silver Lake and Ivanhoe Reservoirs would remain as open non-potable water reservoirs after completion of construction of the project, and the water within these reservoirs would no longer be treated. The Certified EIR concluded that algae growth could occur that would change the appearance of the water within the reservoirs. However, there would be no impact to water quality because these reservoirs would no longer store treated drinking water.
Consistent with the Certified EIR, construction of the in-reservoir pipeline alignment addressed in this addendum would also create storm water runoff from the construction sites that could impact water quality. Therefore, the in-reservoir pipeline alignment would be required to implement mitigation measure WR-1 from the Certified EIR. Similarly, there would be no long- term water quality or groundwater impacts associated with the conversion of the SLRC from drinking water storage to open non-potable reservoirs under the in-reservoir pipeline alignment. Consistent with the Certified EIR, although algae growth could occur within the reservoirs that would periodically change the appearance of the water, this would create a less than significant impact to water quality. Therefore, the water resources impacts of the in-reservoir pipeline alignment would be no greater than those described in the Certified EIR.
2.4 Biological Resources
The SLRC is located in the hilly residential neighborhoods of the Silver Lake community. Surrounding land uses include residential and limited commercial functions. There is no natural land cover in the vicinity of the SLRC. Ornamental landscaped vegetation is common within and
December 2013 Page 35 Introduction around the SLRC. However, the Silver Lake Recreation Center property supports landscaped areas with some native trees, including western sycamore (Platanus racemosa). Ornamental landscaped vegetation supports a number of species of avian wildlife adapted to urban conditions. These include house finch (Carpodacus mexicanus), American crow (Corvus brachyrhynchos), common raven (Corvus corax), and northern mockingbird (Mimus polyglottos). In addition, ornamental trees may support nesting species, including nesting raptors such as red-tailed hawk (Buteo jamaicensis). Great blue herons (Ardea Herodias) are known to nest in ornamental trees on the northwest side of Silver Lake Reservoir. The open water within the SLRC is also known to attract ruddy duck (Oxyura jamaicensis), eared grebe (Podiceps nigricollis), and bufflehead (Bucephala albeola). Canada goose (Branta canadensis) and gulls (Larus spp.) have also been observed using the SLRC. These bird species do not forage at SLRC because there is a lack of aquatic species in the reservoirs.
The Certified EIR concluded that there would be no direct impact to or loss of native vegetation communities or special status plant species during construction of the bypass pipeline tunneling alignment because construction activities would occur within existing roadways, ornamentally landscaped areas, or other developed areas. The Certified EIR concluded that impacts to common wildlife species would be minimized through implementation of Best Management Practices during the construction phase. Impacts to sensitive mammal species (bats) would be reduced to a less than significant level through implementation of mitigation measure BR-5. Additionally, impacts to nesting bird species would be reduced to a less than significant level through implementation of mitigation measure BR-4 to comply with the Migratory Bird Treaty Act.
No impacts were identified in the Certified EIR during long-term operations at the SLRC as Silver Lake and Ivanhoe Reservoirs would remain open water bodies, and the bypass line tunnel facilities would be located below ground.
Similar to the Certified EIR, the construction phase of the in-reservoir pipeline alignment addressed in this addendum has the potential to indirectly impact nesting bird species and bat species using the SLRC. Under this in-reservoir pipeline alignment, construction would occur primarily within the SLRC, including mostly within Silver Lake Reservoir itself. Trenching activities within West Silver Lake Drive would not directly impact either habitat or species. However, trenching would occur within the lawn area between West Silver Lake Drive and Silver Lake Reservoir, and the regulator station would also be constructed in this area. LADWP would avoid tree removal to the greatest extent possible by working in open areas of lawn and using the embankment of Silver Lake Reservoir, rather than vegetated areas, as the location for the regulator station. However, indirect impacts to nesting bird species and sensitive mammal species could occur depending on the timing of construction activity due to noise produced by construction equipment in close proximity to nesting and roosting sites. As described in the Certified EIR, such impacts would be reduced to a less than significant level with implementation of Best Management Practices and mitigation measures BR-4 and BR-5. Further, the shorter duration of construction for the in-reservoir pipeline alignment (18 months compared to 36 months), commencing construction outside of the bird nesting season, and limiting the draining of Silver Lake Reservoir to one bird nesting season would reduce the amount of time wildlife would be exposed to noise and other construction effects. As part of the in-reservoir pipeline alignment, Silver Lake Reservoir would be drained for approximately 12 months during the construction period in order to install a portion of the pipeline within the reservoir. Silver Lake Reservoir has manmade edges and does not contain aquatic vegetation or wildlife species. Therefore, the reservoir is not a food source for waterfowl present at the SLRC. By temporarily draining the reservoir during construction, there would be no direct impact
Page 36 Silver Lake Reservoir Complex Storage Replacement Project to waterfowl. As concluded in the Certified EIR, no impacts to biological resources would occur during long-term operations. Therefore, the biological resources impacts of the in-reservoir pipeline alignment would be no greater than those described in the Certified EIR.
2.5 Cultural Resources
Silver Lake and Ivanhoe Reservoirs were designated City Historic-Cultural Monument No. 422 in March 1989. The nomination refers specifically to only the reservoirs and dams, noting their importance in the growth of the City and to its water system. The SLRC and the surrounding area has experienced extensive ground disturbance from past and ongoing municipal and residential development, construction of underground utilities, and road infrastructure improvements. No archaeological sites or resources have been encountered during previous excavation projects, and no archaeological sites or resources are expected to exist within or adjacent to the SLRC.
During construction of the bypass pipeline tunneling alignment, the Certified EIR concluded that construction staging and ground disturbing activities within the SLRC would temporarily significantly impact the historic setting of Silver Lake and Ivanhoe Reservoirs. The impact would be reduced to a less than significant level with implementation of mitigation measure CR-2. Additionally, although the potential to encounter archaeological resources is considered low, implementation of mitigation measure CR-1, which requires compliance with CEQA Guidelines Section 15064.5, would ensure a less than significant impact.
The Certified EIR concluded that there would be no long-term impacts to cultural resources during operation of the bypass pipeline tunneling alignment because the facilities would be located below ground and the SLRC would maintain its existing appearance following completion of construction. Additionally, the change in function of Silver Lake and Ivanhoe Reservoirs would not alter the appearance or general condition of the SLRC, and no impact to historic resources would occur.
Similar to the bypass pipeline tunneling alignment, the construction phase of the in-reservoir pipeline alignment addressed in this addendum would temporarily impact the historic setting of Silver Lake and Ivanhoe Reservoirs. Under the in-reservoir pipeline alignment, most construction activity would take place within the SLRC. As concluded in the Certified EIR, the impact to historic resources would be reduced to a less than significant level with implementation of mitigation measure CR-2. Unlike the bypass pipeline tunneling alignment, no tree removal is anticipated as part of the in-reservoir pipeline alignment to construct the regulator station along the west embankment of Silver Lake Reservoir. Therefore, fewer landscape features would be disturbed. Any ground disturbing activities have the potential to uncover previously unknown archaeological resources, even though the probability of encountering unknown resources is considered low. Similar to the bypass pipeline tunneling alignment, implementation of mitigation measure CR-1 would reduce the impact to archaeological resources to a less than significant level. As concluded in the Certified EIR, no impacts to cultural resources would occur during long-term operations because all facilities would be located below ground or within Silver Lake Reservoir. Therefore, the cultural resources impacts of the in-reservoir pipeline alignment would be no greater than those described in the Certified EIR.
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2.6 Paleontologic Resources
Geologic mapping of the SLRC indicates that the site periphery is underlain by two late Cenozoic rock units, including the sandstone facies of middle to late Miocene marine Monterey Formation and late Pleistocene to Holocene alluvium. Boring for the bypass pipeline tunneling alignment would pass through the Monterey Formation and possibly alluvium. Excavation for the Redesdale North Shaft and the Putnam Shaft would encounter alluvium, but would also encounter the Monterey Formation at depth. Excavation for the Redesdale South Shaft and the regulator station would primarily encounter artificial fill, but might encounter alluvium and/or the Monterey Formation at depth. The occurrence of a number of previously recorded fossil localities near the SLRC suggests that there is a high potential for additional similar, scientifically important fossil remains being encountered by earth-moving activities in the sandstone facies of the Monterey Formation and alluvium.
The Certified EIR concluded that ground disturbance and earthwork movement associated with the bypass pipeline tunneling alignment construction would significantly impact paleontologic resources due to the potential for these to occur in alluvium greater than 5 feet below ground surface and at any depth in the Monterey Formation. The impact would be reduced to a less than significant level with implementation of mitigation measures PR-1 and PR-3.
During long-term operations, the Certified EIR concluded that there would be no impact to paleontologic resources as no additional ground disturbing activities would occur.
The depth of construction would be shallower under the in-reservoir pipeline alignment addressed in this addendum compared to the depth of construction for the bypass pipeline tunneling alignment. However, construction of the in-reservoir pipeline alignment would still potentially encounter paleontologic resources through disturbance of the Monterey Formation and alluvium. Consistent with the Certified EIR, the construction impacts to paleontologic resources would be reduced to a less than significant level with implementation of mitigation measures PR-1 and PR-3. As concluded in the Certified EIR, no impacts to paleontologic resources would occur during long-term operations. Therefore, the paleontologic resources impacts of the in-reservoir pipeline alignment would be no greater than those described in the Certified EIR.
2.7 Transportation and Traffic
Under the bypass pipeline tunneling alignment, a pipeline would be tunneled beneath West Silver Lake Drive using launching and receiving pits located within West Silver Lake Drive. West Silver Lake Drive is a generally north-south roadway. It provides two travel lanes (one lane in each direction) and local access to the surrounding residential neighborhood. Parking is allowed on the western portion of the roadway and is prohibited on the eastern portion along the SLRC property boundary.
The traffic analysis in the Certified EIR measured existing traffic volumes and projected future traffic volumes at five nearby study intersections. The traffic analysis determined that there would be approximately 130 daily passenger car equivalent truck trips during the peak phase of construction combined with approximately 37 personnel vehicle trips during the morning and evening peak traffic period. This would result in approximately 53 total vehicle trips occurring during the morning and evening peak periods of traffic. When these trips were added to existing and future traffic conditions, the Certified EIR concluded that construction of the bypass pipeline
Page 38 Silver Lake Reservoir Complex Storage Replacement Project tunneling alignment would create a significant impact at two study intersections: Silver Lake Boulevard/Van Pelt Avenue and Riverside Drive/Fletcher Drive.
The Certified EIR also concluded that construction activity associated with the bypass pipeline tunneling alignment would create significant traffic impacts on West Silver Lake Drive due to the intermittent closures of lanes during the 36-month construction period, the elimination of on- street parking in the area of the launching and receiving pits, and one-way traffic configuration for the Redesdale South Shaft and regulator station. Implementation of mitigation measures TT- 2 and TT-3 would be required. However, even after mitigation, the Certified EIR concluded that the short-term impacts to transportation and traffic would be significant and unavoidable.
There would be no additional vehicle traffic associated with long-term operation of the bypass pipeline tunneling alignment. Therefore, the Certified EIR concluded that there would be no long-term transportation and traffic impacts.
During the peak phase of construction of the in-reservoir pipeline alignment addressed in this addendum, it is anticipated that there would be approximately 75 daily passenger car equivalent truck trips combined with approximately 50 personnel vehicle trips during the morning and evening peak traffic period, resulting in approximately 59 total vehicle trips occurring during the morning and evening peak periods of traffic. Therefore, as with the bypass pipeline tunneling alignment, construction of the in-reservoir pipeline alignment would create a short-term impact at the intersections of Silver Lake Boulevard/Van Pelt Avenue and Riverside Drive/Fletcher Drive.
Construction within West Silver Lake Drive under the in-reservoir pipeline alignment would take place primarily between Armstrong Avenue and the northwest corner of Silver Lake reservoir, about 300 feet north of Hawick Street. The open-trench construction at the intersection of West Silver Lake Drive and Silver Lake Boulevard that would occur under the bypass pipeline tunneling alignment would be eliminated under the in-reservoir pipeline alignment. Compared to the bypass pipeline tunneling alignment, which would result in the intermittent closures of portions of West Silver Lake Drive for approximately 3 years, the construction of the in-reservoir pipeline alignment would affect the block of West Silver Lake Drive between Armstrong Avenue and Tesla Avenue for approximately 6 months, then the block between Tesla Avenue and the northwest corner of Silver Lake reservoir for approximately 4 months. It would be possible to maintain a lane of traffic in each direction on West Silver Lake Drive between Armstrong Avenue and Tesla Avenue during construction in Work Area 1. A one-way traffic configuration to maintain northbound traffic on West Silver Lake Drive would be required between Hawick Street and Armstrong Avenue during construction in Work Area 2 for an approximate 4-month period. Parking would also be removed for the 10-month period during which in-road trenching would occur. Therefore, in-road construction of the in-reservoir pipeline alignment would still create significant roadway segment impacts on West Silver Lake Drive. Implementation of mitigation measures TT-2 and TT-3 would be required to reduce traffic impacts of the in-reservoir pipeline alignment. However, even after mitigation, as concluded in the Certified EIR, the short-term impacts to transportation and traffic would be significant and unavoidable. As concluded in the Certified EIR, there would be no transportation and traffic impacts during long-term operations because no additional vehicle trips would be generated. Therefore, the transportation and traffic impacts of the in-reservoir pipeline alignment would be no greater than those described in the Certified EIR.
December 2013 Page 39 Introduction
2.8 Noise
Ambient noise in the vicinity of the SLRC is characterized by local traffic and occasional residential activities, such as lawn mowers and leaf blowers. Operation of the reservoirs does not generate noise because the pumps and other machinery are located inside structures or are adequately muffled. Noise levels in the project vicinity range from 50.0 to 70.4 community equivalent noise level (Leq) in decibels (dB).
LADWP would comply with the City’s Noise Ordinance during construction. The Noise Ordinance limits the hours of construction to between 7:00 a.m. and 9:00 p.m. Monday through Friday, and between 8:00 a.m. and 6:00 p.m. on Saturdays. Construction noise is not permitted on Sundays or federal holidays. Even with compliance with the Noise Ordinance, noise generated by construction equipment under the bypass pipeline tunneling alignment would increase the existing ambient noise levels by more than 5 A-weighted decibels (dBA). Construction equipment noise would exceed 95 dBA at the Redesdale North Shaft and Putnam Shaft locations on West Silver Lake Drive. According to the Certified EIR, the construction noise impact would be significant, and implementation of mitigation measure N-2 is required. However, due to the nature of the construction activities, it would not be feasible to erect noise barriers around the shaft locations. Therefore, the Certified EIR concluded that construction noise levels would remain significant and unavoidable.
During project operations, the regulator station would be expected to generate noise levels of 60 dBA. The Certified EIR concluded that noise levels would increase over existing ambient by more than 5 dBA. Due to the proximity of the regulator station to nearby residential uses and the Silver Lake Recreation Center property, the impact would be significant, and implementation of mitigation measure N-3 is required. With implementation of insulation and equipment mufflers, the operational noise impacts of the regulator station would be reduced to a less than significant level.
The in-reservoir pipeline alignment addressed in this addendum would move most construction activity from West Silver Lake Drive to within the SLRC property boundaries. Due to the distance of construction activity from sensitive receptors, noise levels experienced by many nearby residential uses and other sensitive receptors would be reduced compared to the bypass pipeline tunneling alignment. However, the in-reservoir pipeline alignment would still involve construction within West Silver Lake Drive. Trenching would occur along West Silver Lake Drive in a progressive manner generally beginning in the block between Armstrong Avenue and Tesla Avenue and then would move south to the block between Tesla Avenue and the turn into the SLRC about 300 feet north of Hawick Street. Construction in the roadway would take a total of approximately 10 months compared to approximately 3 years of in-road construction activities for the bypass pipeline tunneling alignment. Nonetheless, noise from in-roadway construction activities would still affect residential uses located less than 500 feet from the construction site. During trenching, the loudest construction equipment would generate noise levels up to 89 dBA, which would create a significant impact at nearby receptors. Mitigation measure N-2 would reduce the noise disturbance, but there would still be a significant increase in noise levels compared to existing ambient conditions. Similar to the bypass pipeline tunneling alignment, it would not be possible to erect a noise barrier entirely around Work Areas 1 and 2 due to the need to access the construction site by construction vehicles. However, construction noise barriers would be installed where feasible and applicable to reduce short-term construction noise. Nonetheless, short-term noise impacts would be significant and unavoidable, even with implementation of mitigation. During operation of the in-reservoir pipeline alignment, noise would only be expected to be generated by the regulator station. Under the in-reservoir pipeline
Page 40 Silver Lake Reservoir Complex Storage Replacement Project alignment, the regulator station would be moved farther away from the closest sensitive receptor. Nonetheless, insulation and muffling of the equipment would still be required per mitigation measure N-3 from the Certified EIR to reduce noise to a less than significant level. Therefore, the noise impacts of the in-reservoir pipeline alignment would be no greater than those described in the Certified EIR.
2.9 Air Quality
The SLRC is located in Los Angeles County, which is part of the South Coast Air Basin. Air quality in the region is regulated by the South Coast Air Quality Management District (SCAQMD). The South Coast Air Basin has been designated nonattainment for ozone (O3), particulate matter less than 10 microns in diameter (PM10), and particulate matter less than 2.5 microns in diameter (PM2.5).
Construction activity has the potential to generate pollutants from the use of heavy construction equipment, ground disturbing activities, and construction-related vehicle trips. Regional pollutant emissions were calculated for construction of the bypass pipeline tunneling alignment. According to the Certified EIR, maximum regional pollutant emissions of nitrogen oxides (NOx) and PM10 would exceed the SCAQMD daily thresholds of significance. Construction of the regulator station would also generate maximum daily emissions of NOx and PM10 in excess of SCAQMD daily thresholds of significance. Additionally, the combined construction emissions at the Headworks Spreading Grounds and SLRC sites would result in a significant cumulative regional air quality emissions impact. Even with compliance with SCAQMD Rule 403 (Fugitive Dust) and implementation of mitigation measure AQ-1, the project-level and cumulative construction impacts of the bypass pipeline tunneling alignment would remain significant and unavoidable.
There would be no additional vehicle traffic or construction activity associated with long-term operation of the facilities at the SLRC. Therefore, the Certified EIR concluded that there would be no operational air quality impact.
Construction of the in-reservoir pipeline alignment addressed in this addendum would also generate emissions associated with the use of heavy construction equipment, ground disturbing activities, and construction-related delivery trucks. Compared to the Certified EIR, similar types and numbers of construction equipment would be used, and the number of construction personnel would not vary substantially. However, the duration of construction and, therefore, the overall hours of equipment operation would be reduced. Construction of the in-reservoir pipeline alignment would be completed in approximately 18 months compared to 36 months for the bypass pipeline tunneling alignment. The volume of excavated material would be substantially reduced under the in-reservoir pipeline alignment compared to the bypass pipeline tunneling alignment (27,450 cubic yards versus 41,450 cubic yards). The in-reservoir pipeline alignment would drain Silver Lake Reservoir during trenching of the pipeline and use the reservoir to temporarily stockpile excavated materials and dispose of excess soils. Although it would expose the bottom of Silver Lake Reservoir, the number of on-road construction vehicle trips would be reduced. In order to minimize impacts associated with fugitive dust, LADWP would comply with SCAQMD Rule 403, similar to the Certified EIR. This would include implementing the following Best Available Control Technologies:
December 2013 Page 41 Introduction
1) Water shall be applied to exposed surfaces at least two times per day to prevent generation of dust plumes. 2) The construction contractor shall utilize at least one of the following measures at each vehicle egress from the project site to a paved public road: a. Install a pad consisting of washed gravel maintained in clean condition to a depth of at least six inches and extending at least 30 feet wide and at least 50 feet long; b. Pave the surface extending at least 100 feet and at least 20 feet wide; c. Utilize a wheel shaker/wheel spreading device consisting of raised dividers at least 24 feet long and 10 feet wide to remove bulk material from tires and vehicle undercarriages; or d. Install a wheel washing system to remove bulk material from tires and vehicle undercarriages. 3) All haul trucks hauling soil, sand, and other loose materials shall be covered (e.g., with tarps or other enclosures that would reduce fugitive dust emissions). 4) Construction activity on exposed or unpaved dirt surfaces shall be suspended when wind speed exceeds 25 miles per hour. 5) Ground cover in disturbed areas shall be replaced in a timely fashion when work is completed in the area. 6) A community liaison shall be identified concerning on-site construction activity including resolution of issues related to PM10 generation. 7) Non-toxic soil stabilizers shall be applied according to manufacturers’ specifications to all inactive construction areas (previously graded areas inactive for ten days or more). 8) Traffic speeds on all unpaved roads shall be limited to 15 mph or less. 9) Streets shall be swept at the end of the day if visible soil is carried onto adjacent public paved roads. If feasible, water sweepers with reclaimed water shall be used. 10) Stockpiles shall be covered or otherwise stabilized
LADWP has also committed to additional watering using water trucks, paving haul routes within the reservoir, and installing gravel in staging areas within the reservoir to further minimize air quality impacts.
Compliance with Rule 403 would reduce emissions of PM10 and PM2.5 by approximately 60 percent. Nonetheless, as concluded in the Certified EIR, even with compliance with SCAQMD Rule 403 and implementation of mitigation measure AQ-1 and LADWP’s construction commitments, the project-level and cumulative construction air quality impacts would remain significant and unavoidable. There would be no additional vehicle traffic or construction activity associated with long-term operation of the facilities at the SLRC. Therefore, as concluded in the Certified EIR, there would be no long-term operational air quality impact. Therefore, the air quality impacts of the in-reservoir pipeline alignment would be no greater than those described in the Certified EIR.
2.10 Public Services and Utilities
The City of Los Angeles Fire Department provides fire and emergency medical services (paramedic/rescue) to the SLRC primarily via Fire Station 56, located at 2759 Rowena Avenue. Police protection for the SLRC is provided by the Northeast Community Police Station, located at 3353 San Fernando Road. Community facilities in the vicinity of the SLRC include the Silver Lake Recreation Center and a dog park, both located south of the Silver Lake Reservoir Dam, and a community nursery school that is located in the northeast corner of the SLRC. Utilities in
Page 42 Silver Lake Reservoir Complex Storage Replacement Project the vicinity of the SLRC include a Southern California Gas pipeline, telephone lines, cable lines, City of Los Angeles sewer line and storm drain, and LADWP water pipelines and power lines.
The Certified EIR concluded that neither in-street construction for the bypass pipeline tunneling alignment nor additional traffic from construction activities would interfere with emergency response plans or emergency evacuation plans; nor would these activities diminish the ability of police, fire, and emergency medical service personnel to respond to emergencies. The facilities would be constructed using local labor; therefore, there would be no population growth that would require additional staffing or equipment for emergency services. Neither the dog park nor the nursery school would be impacted by construction activities at the SLRC. Users of the Silver Lake Recreation Center may be temporarily inconvenienced by construction of the regulator station, but construction of a replacement recreation facility or expansion of an existing facility would not be required. Further, construction activities at the SLRC would not result in service interruptions or otherwise adversely affect existing utilities. The Certified EIR concluded that construction impacts to public services and utilities would be less than significant, and no mitigation measures are required.
During long-term operation of the bypass pipeline tunneling alignment, all facilities would be located below ground. The facilities would be operated and maintained by existing LADWP staff; therefore, there would be no population growth that would require additional staffing or equipment for emergency services, the expansion or construction of new public facilities, or the extension of area utilities. The Certified EIR concluded that there would no long-term operational impact to public services and facilities.
Similar to the bypass pipeline tunneling alignment, construction of the in-reservoir pipeline alignment addressed in this addendum would not interfere with emergency response plans or emergency evacuation plans; nor would these activities diminish the ability of police, fire, and emergency medical service personnel to respond to emergencies. Unlike the bypass pipeline tunneling alignment, no road closures are anticipated during trenching activities along West Silver Lake Drive. There would be no population growth that would require additional staffing or equipment for emergency services. Further, construction activities at the SLRC would not result in service interruptions or otherwise adversely affect existing utilities. Unlike the bypass pipeline tunneling alignment, construction of the in-reservoir pipeline alignment would not occur within the Silver Lake Recreation Center property. LADWP would install a temporary detour of the walking path along the west side of Ivanhoe Reservoir to maintain pedestrian access during construction activities. Therefore, there would be construction impacts to public facilities. As concluded in the Certified EIR, the impacts to public services and utilities during construction of the in-reservoir pipeline alignment would be less than significant. Consistent with the Certified EIR, there would be no long-term impacts to public services and utilities during operations. Therefore, the impacts to public services and utilities of the in-reservoir pipeline alignment would be no greater than those described in the Certified EIR.
2.11 Hazards and Hazardous Materials
The SLRC is located in the community of Silver Lake and consists of LADWP-owned Silver Lake and Ivanhoe Reservoirs and related facilities. The SLRC site and immediate vicinity are not identified on any hazardous waste site or waste generator lists.
During construction of the bypass pipeline tunneling alignment, no acutely hazardous materials would be used or generated. There are no known hazardous materials sites located within or adjacent to the SLRC that would require remediation as part of construction. Relatively small
December 2013 Page 43 Introduction quantities of non-acutely hazardous materials would be used during construction. These include typical construction products, such as gasoline, diesel fuel, motor oil, hydraulic fluid, solvents, cleaners, sealants, welding flux, and various lubricants. These materials would be handled in accordance with local and state regulations, and would not pose a hazard to the public. Therefore, the Certified EIR concluded that the short-term impact associated with hazards and hazardous materials would be less than significant.
During operation of the facilities at the SLRC, no new or additional hazardous materials would be used or stored on site. Therefore, the Certified EIR concluded that the long-term impact associated with hazards and hazardous materials would be less than significant.
Similar to the bypass pipeline tunneling alignment, construction of the in-reservoir pipeline alignment addressed in this addendum would use some non-acutely hazardous materials. These materials would be handled in accordance with local and state regulations and would not pose a hazard to the public. Therefore, the construction impact would be less than significant. Operation of the in-reservoir pipeline alignment would not use or generate hazardous materials, and the impact would be less than significant. Therefore, the impacts of hazards and hazardous materials of the in-reservoir pipeline alignment would be no greater than those described in the Certified EIR.
2.12 Visual Resources
The most visually prominent element of the SLRC is the large, open Silver Lake Reservoir. Ivanhoe Reservoir is a smaller, open, concrete-lined reservoir located at the north end of Silver Lake Reservoir. As mentioned above, Ivanhoe Reservoir is currently temporarily covered with shade balls.1 Other key visual features of the SLRC include a grove of large eucalyptus trees located on the west side of Silver Lake Reservoir; a large, natural-appearing area located on the east side of the SLRC accommodating a collection of small structures and service yards that support the LADWP operations; a small area fronting on Tesla Avenue at the north end of the SLRC that is used by a neighborhood nursery school; a 2-acre strip of land in front of the Silver Lake Reservoir Dam that is leased to the Los Angeles Department of Recreation and Parks and accommodates a recreation center, basketball courts, and a dog park; and other landscaped areas used for passive recreation. Except for the area leased to the Department of Recreation and Parks, the entire SLRC is surrounded by an 8-foot tall chain-link fence topped with barbed wire, and public access (other than to the nursery school property) is not permitted. The SLRC is separated from the surrounding development by public roads.
Construction of the bypass pipeline tunneling alignment would occur adjacent to the SLRC in West Silver Lake Drive and in the Silver Lake Recreation Center property south of Silver Lake Reservoir Dam. Construction activity would be visible at close range to recreational users and motorists traveling along West Silver Lake Drive and other nearby streets that offer views into the SLRC. The presence of the construction activities related to the development of these facilities would add a visually contrasting and disruptive element to views in the immediately surrounding area and would lead to a decrease in the overall level of visual quality. The
1 Per the compliance deadlines agreed to by LADWP and the California Department of Public Health, LADWP is required to remove Ivanhoe Reservoir from service as a treated water facility by November 2014. This removal would entail severing the inlet and outlet connections for the reservoir as well as removing the shade balls from the reservoir. Removal of the shade balls will occur prior to the start of construction of the in-reservoir pipeline alignment.
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Certified EIR concluded that these effects would be temporary and the areas that would be disturbed by the construction activities would be restored to their original appearance. Therefore, the impact would be less than significant.
Under the bypass pipeline tunneling alignment, Ivanhoe and Silver Lake Reservoirs would cease to function as reservoirs for storage of treated drinking water. In the long-term, the reservoirs would remain in place as open non-potable reservoirs. Water levels in the reservoirs would be maintained to within their historic operating range, but the reservoirs would be disconnected from the LADWP water distribution system. The only long-term alteration in the visible appearance of these reservoirs that may occur as a result of these changes is a change in water color due to the growth of algae. However, the Certified EIR concluded that the impact would not be significant.
Construction of the in-reservoir pipeline alignment addressed in this addendum would involve construction activities within West Silver Lake Drive, in the grove of eucalyptus trees on the west side of Silver Lake Reservoir, and within Silver Lake Reservoir. The reservoir would be drained for a period of approximately 12 months. The duration of construction for the in- reservoir pipeline alignment would be approximately 18 months compared to 36 months for the bypass pipeline tunneling alignment. Construction activities and the empty reservoir would be visible at close range to recreational users and motorists traveling along West Silver Lake Drive and other nearby streets that offer views into the SLRC. Views would also be available from some adjacent residences. These effects would be temporary. Following completion of pipeline installation within Silver Lake Reservoir, the reservoir would be refilled and the view would be returned to its existing condition. Trenching activity within West Silver Lake Drive is expected to be completed within 10 months of the start of construction, at which point the disturbed portions of the roadway would be repaved and restriped. Following trenching activity and construction of the regulator station, the landscaping within the eucalyptus grove would be restored. Unlike the bypass tunneling alignment, no trees are anticipated to be removed during construction of the in-reservoir pipeline alignment. Due to the short-term nature of the disturbance and the restoration of the original view, the visual impact of construction would be less than significant. Long-term operation of the in-reservoir pipeline alignment would not involve any above ground structures. During operations, Silver Lake and Ivanhoe Reservoirs would be operated as permanent open non-potable reservoirs, and the visual impact would be less than significant. Therefore, the impacts to visual resources of the in-reservoir pipeline alignment would be no greater than those described in the Certified EIR.
2.13 Other Environmental Issue Areas
Growth Inducement
During construction of the bypass pipeline tunneling alignment, a relatively large number of construction workers would be needed. The workers are generally anticipated to live and work in the Los Angeles region, resulting in a less than significant impact on the permanent increase of population, housing, geographic distribution, and supply-demand relationships. Therefore, the Certified EIR concluded that the bypass pipeline tunneling alignment would not be growth- inducing.
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The bypass pipeline tunneling alignment was proposed in response to updated water quality regulations. Implementation of the bypass pipeline tunneling alignment would not add to the amount of water available to the service area or the ability of LADWP to serve such water. Therefore, the Certified EIR concluded that long-term implementation would not induce growth.
Similar to the bypass pipeline tunneling alignment, the in-reservoir pipeline alignment addressed in this addendum would need a relatively large number of construction workers who would be anticipated to live and work in the Los Angeles region. Therefore, no permanent population increase would occur as a result of the in-reservoir pipeline alignment. Similar to the bypass pipeline tunneling alignment, long-term operation of the in-reservoir pipeline alignment would not affect the amount of water available to the service area or LADWP’s ability to serve such water. Therefore, the growth-inducing effects of the in-reservoir pipeline alignment would be no greater than those described in the Certified EIR.
Significant Irreversible Environmental Effects
The Certified EIR concluded that materials and energy necessary to implement the bypass pipeline tunneling alignment would be irreversibly committed. The construction of the facilities would require the commitment of construction materials including concrete, pipe, asphalt, and other materials. The construction of these facilities would also require the commitment of gasoline, diesel fuel, refined oil, electrical energy, and water. The Certified EIR concluded that these impacts would not be significant because sufficient quantities of these resources exist in the region.
Operation of the bypass pipeline tunneling project would not require the use of additional natural resources beyond existing circumstances. Operation of the regulator station would require electricity and gas, but the use of these materials and energy would be minimal. Therefore, the Certified EIR concluded that the impact would not be significant.
Similar to the bypass pipeline tunneling alignment, the in-reservoir pipeline alignment addressed in this addendum would irreversibly commit materials and energy during construction. However, the impact would be less than significant because sufficient quantities of these resources exist in the region. During long-term operations, similar to the bypass pipeline tunneling alignment, minimal electricity and gas would be required to operate the regulator station. As concluded in the Certified EIR, the operational impact would not be significant. Therefore, the impacts associated significant irreversible environmental effects of the in-reservoir pipeline alignment would be no greater than those described in the Certified EIR.
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