Guam and CNMI Military Relocation (2012 Roadmap Adjustments) SEIS Draft April 2014 5.2 NAVAL MAGAZINE (EAST/WEST) LIVE-FIRE TRAINING RANGE COMPLEX – ALTERNATIVE 2 Under Alternative 2, the proposed development of a live-fire training range complex would occur at NAVMAG East/West. Details about this alternative are provided in Section 2.5.4.2 and the proposed site is illustrated in Figure 2.5-3. 5.2.1 Geological and Soil Resources 5.2.1.1 Affected Environment The affected environment for the HG Range at Andersen South would be the same as described under Alternative 1 in Section 5.1.1.1 of this SEIS. The affected environment for geological and soil resources associated with Alternative 2 is consistent with the affected environment description in the 2010 Final EIS (Volume 2, Chapter 3: Geological and Soil Resources, Section 3.1.5 South, pages 3-26 to 3-28), which is summarized below for reference. The proposed reduction in the number of relocating Marines and dependents under the 2012 Roadmap Adjustments does not alter the description of the affected environment for geological and soil resources, but it would reduce some potential impacts to geological and soil resources that were determined to be less than significant or mitigated to less than significant in the 2010 Final EIS, as described in the analysis of environmental consequences for Alternative 2 below. Alternative 2 would be located in a topographically rugged, hilly-to-mountainous area in the south-central part of Guam. Within the proposed project footprint, elevations range from approximately 200 feet (61 m) above MSL along the northeastern extent to approximately 520 feet (158 m) MSL along the southern extent of the footprint. To the northwest of the proposed Alternative 2 footprint is Fena Valley Reservoir, and to the west is Mount Almagosa. The proposed Alternative 2 footprint is underlain by volcanic bedrock. One known minor bedrock fault crosses the footprint and there are multiple others (including one major) in the surrounding area (Figure 5.2.1-1). The soils of Guam are described in the 2010 Final EIS (Volume 2, Chapter 3: Geological and Soil Resources, Section 3.1.1.3 Geologic Units, Figure 3.1-4 and Table 3.1-1, pages 3-8 to 3-9). Three soil groups cover the majority of the footprint: Ylig clay, Togcha-Akina silty clay, and Akina Badland Association (Figure 5.2.1-2). Depth and drainage capacity of these soil groups vary from very shallow to very deep, and well drained to poorly drained (Young 1988). The Agfayan Clay, Akina-Atate-Silty Clay, and Akina Silty Clay cover the remainder of the footprint. For the latter three groups as a whole, runoff is medium to rapid, and the water erosion hazard is moderate to severe (Young 1988). The three dominant soil types in the proposed Alternative 2 footprint are considered limited agriculturally-productive soils because of the elevated acidity of these soils. However, these soils support production of watermelons and pineapples (Young 1988). Prime farmland soils, as defined by the USDA, are soils best suited to producing food, seed, forage, fiber and oilseed crops, favorable for economic production and sustained high yield, with minimal inputs of energy and resulting in least damage to the environment (Young 1988). The Togcha component of the Togcha-Akina silty clay group meets the requirements for prime farmland when irrigated (Young 1988). 5-95 Legend Area of Detail DoD Property on Guam LFTRC Alternative 2 Impacted Area Philippine Sea Geologic Features: Observed and Inferred Major Faults & Fault Zones Observed and Inferred Minor Faults & Fault Zones Depression/Sinkhole Landslide Potential: Moderate Pacific Ocean Moderate to High High Fena Valley Liquefaction 1 " = 18 Miles Geologic Classes: Reservoir Alluvium, Beach/Reef Deposits, and Artificial Fill Old Limestone MRFR Volcanic Units NAVMAG KD Rifle 5-96 KD Pistol MPMG NSSA Access Road 0 0.4 0.8 Figure 5.2.1-1 Miles Geologic Features in the Vicinity of ¤ Kilometers Sources: COMNAV Marianas 2008; GovGuam 2008; 0 0.4 0.8 NAVMAG (East/West) LFTRC Alternative 2 NAVFAC Pacific 2013; WERI 2001 100 200 Legend Area of Detail 100 on Guam 400 LFTRC Alternative 2 Impacted Area 300 100 500 200 DoD Property Philippine Sea 200 Contour (100-ft Interval) 700 700 Soil Classes: 100 100 100 Agfayan Clay Agfayan-Akina Association 300 Agfayan-Akina-Rock Outcrop 200 200 200 100 Pacific Ocean Akina Silty Clay 200 Akina-Atate Association 900 Fena Valley 300 300 100 700 0 0 Akina-Atate Silty Clay 1 1 " = 18 Miles Akina-Badland Association Reservoir 400 Urban Land Complex 400 Chacha Clay 400 400 MRFR 200 Inarajan Clay 900 200 Pulantat Clay 200 Ritidian-Rock Outcrop Complex 400 400 Togcha-Akina Silty Clay 900 400 Ylig Clay NAVMAG 400 800 300 KD Rifle 5-97 300 500 300 KD Pistol 500 900 400 200 MPMG 900 NSSA 900 300300 300 300 700 800 400 300 200 300 700 400 400 300 700 500 500 500 400 500 500 Access Road 300 300 400 400 500 700 400 0 0.4 0.8 Figure 5.2.1-2 Miles Kilometers Soils in the Vicinity of ¤ 0 0.4 0.8 NAVMAG (East/West) LFTRC Alternative 2 Sources: NAVFAC Pacific 2013; NRCS 2006 Guam and CNMI Military Relocation (2012 Roadmap Adjustments) SEIS Draft April 2014 With respect to geologic hazards (see Section 3.1.1.1) there is one major bedrock fault mapped within the Alternative 2 footprint. The overall likelihood for landslides to occur is considered high due to many areas combining steep slopes with soils vulnerable to slipping in seismic events (see Figure 5.2.1-1). The maximum reported tsunami waves height reached on Guam was approximately 11.5 feet (3.5 m) in an 1849 tsunami event. The area proposed for development of Alternative 2 is located away from the coastline and above the elevation susceptible to tsunamis. The Alternative 2 footprint is not subject to liquefaction because it is underlain by consolidated volcanic bedrock (see Figure 5.2.1-1). There are no preliminary identified topographic features that may contain sinkholes in the volcanic bedrock underlying the Alternative 2 footprint. 5.2.1.2 Environmental Consequences Construction Construction impacts associated with the HG Range at Andersen South would be similar to those described under Alternative 1 in Section 5.1.1.2 of this SEIS. Construction of the new ranges, range support building, roads, bridges, and related infrastructure associated with Alternative 2 would include clearing, grubbing and grading, and excavation (cut) and filling, and stream rerouting. Earthwork would include 1,246,720 yd3 (953,186 m3) of cut (excavation) and 1,254,698 yd3 (959,286 m3) of fill, with a net of 7,981 yd3 (6,102 m3) of fill. Alternative 2 would involve the least volume of excavation of any of the action alternatives. Within the Alternative 2 footprint, there are 30-feet (10-m) differences in elevation in the areas planned for construction of the MPMG and MRF ranges. There would be substantial changes to surface elevation for construction of the MPMG and MRF ranges. However, at the other four LFTRC alternatives, the locations proposed for the MPMG Range have greater elevation differences than at Alternative 2. For example, at Alternative 2, 30-feet (10-m) high slopes would be leveled with about 942,500 yd3 and (725,000 m3) of cut and 910,000 yd3 (700,000 m3) of fill. To build the MPMG Range at Alternative 1, 60-foot and 30-foot high (20- and 30- m) slopes would be leveled over the 1,000 m (0.5 mile) length of the range. Nearly the same amount of fill and 2.5 times as much cut would be needed. Because the elevation changes at Alternative 2 are smaller than those of the other alternatives, less excavation, filling and contouring would occur at Alternative 2 so there would be less alteration of the surrounding landscape than at the other four alternatives. Therefore, Alternative 2 is expected to have a less than significant direct, long-term impact on topography. There is a potential for increased erosion, compaction, and soil loss from physical disturbance caused by construction activity and changes to existing topography. However, project design and construction would incorporate engineering controls as BMPs to minimize erosion, as required by 22 GAR Chapter 10 Guam Soil Erosion and Sediment Control Regulations. Examples of such engineering controls include: Use of drainage diversion and control to direct runoff away from the disturbed area. Use of benches or terraces and drainage control on cut or fill slopes higher than 15 feet (5 m) to minimize erosion on slope faces. For each project, limit the size of the unstabilized disturbed areas to less than 20 acres (8 ha) during construction. Planning earth-moving operations for periods of low rainfall to minimize exposure of disturbed soil to potential runoff. Re-vegetating and permanently stabilizing disturbed areas as soon as possible. 5-98 Guam and CNMI Military Relocation (2012 Roadmap Adjustments) SEIS Draft April 2014 Engineering project slopes in consideration of soil and geological conditions to avoid and minimize erosion. Compliance with the DoD Program-level SWPPP for construction, in addition to individual project SWPPPs during construction to reduce the potential for erosion, runoff, sedimentation, and stormwater pollutant loading. In addition, construction activities associated with Alternative 2 would comply with the Construction General Permit. Potential construction-specific stormwater BMPs would be implemented in compliance with the Construction General Permit as listed in Section 4.1.2-2. Construction-specific stormwater BMPs would provide erosion and sediment control during the construction period, generally by employing on- site measures that reduce the flow of stormwater and minimize the transport of soils and sediment off-site.