NM 532 Curve Correction Project - New Mexico Department of ...

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NM 532 Curve Correction Project Environmental Assessment Figure 3.3 Photograph of Last Curve. 4.0 AFFECTED ENVIRONMENT This section describes the existing environmental conditions in the project area, evaluates the impacts of the proposed action, and suggests mitigation measures for any environmental impacts that cannot be avoided. The No-Build Alternative does not meet the project need, and in general, has little effect on most components of the existing environment. Drainage structures would continue to become silted in with reduced effective drainage. The ability of the roadway to serve local residents may decrease as roadway conditions deteriorate. The remainder of this section evaluates the Recommended Build Alternative described in Section 3.0. 4.1 General Project Setting The Recommended Build Alternative project area is located in Lincoln County, New Mexico (see Figures 1.1 and 1.2). The project area covers approximately 10.0 acres with approximately 6 acres of vegetation disturbance proposed. NMDOT has a permitted right-of-way within the Lincoln National Forest. 4.2 Landforms and Geology Existing Conditions – Volcanic activity created many of the geologic and topographic features of the Sierra Blanca region. Sierra Blanca is a composite volcano that erupted about 35 million years ago (Chronic, 1987). The NM 532 Project Area is located in the Sacramento Section of the Basin and Range Physiographic Province (Williams, 1986). Elevation ranges from 7319 feet above mean sea level (amsl) at the NM 48 / NM 532 junction to 10,080 feet along NM 532 between Windy Point and Ski Apache Ski Area. Principal geologic formations in the project area are Middle Tertiary volcanic rocks and Tertiary intrusive rocks (New Mexico Bureau of Geology and Mineral Resources, 2003). Potential Effects and Mitigation Measures – Correcting design deficiencies would be costly because of steep slopes and uneven topography. As with the No Build Alternative, steep grades and sharp curves March 2013 9 CN 2101140
NM 532 Curve Correction Project Environmental Assessment create challenging driving conditions. Along the existing alignment, the average grade of 8% would remain the same except for minor modifications at curves. Extensive cut and fill construction activities would be completed to correct curve geometrics, roadway grade, and slope stability conditions at the Texas Turn, Axle Bend Curve, and Last Curve. Rock or slope protection would be used to create a stabilized rock-cut face only if unstable rock is encountered. Rock would be excavated mechanically without the use of explosives. RSS wall with rock-filled baskets would be installed at the curves. Less long-term maintenance would be required. 4.3 Soils Existing Conditions – Soils in the NM 532 Project Area are not well mapped. In general, the soils range from deeper alluvial soils in valley bottoms to shallower, rocky soils on mountains side and ridge tops. Because of the steeps slopes in many areas, the soils are subject to erosion, slippage, and landslides when vegetation is removed. Potential Effects and Mitigation Measures – During construction activities, soil excavation and disturbance would occur. Approximately 10 acres would be affected. A Stormwater Pollution Prevention Plan (SWPPP) containing Best Management Practices (BMPs) to reduce erosion would be prepared prior to construction. Slope stabilization and drainage improvements would improve water quality through the reduction of erosion and sediment transport. 4.4 Surface and Ground Water Existing Conditions – The NM 532 Project Area is located within the Eagle Creek and Rio Ruidoso watersheds of the Hondo basin. The North Fork of the Rio Ruidoso has headwaters in the western part of the project area. Eagle Creek, south of NM 532, is a tributary of the Rio Ruidoso, which empties into the Rio Hondo near the town of Hondo. A few drainage crossings may be jurisdictional waters subject to Section 404 permits. Stream flows in Eagle Creek below South Fork can range from less than 1000 acrefeet to 4000 acre-feet per year (Donohoe, 2004). Development is increasing the demand for surface and ground water in the Ruidoso area. The 100-year floodplains are not well mapped in this area (Federal Insurance Administration, 1977). The project area has an upland location and flooding is not a concern. Potential Effects and Mitigation Measures – Reconstruction of the curves would correct drainage issues at those locations; however, the existing drainage problems at other sections along NM 532 would persist. Construction at Last Curve would not involve modification to the existing drainage culvert or work within the Rio Ruidoso. Under current design, Section 404 permitting from the U.S. Army Corps of Engineers (USACE) and Section 401 permitting from the New Mexico Environment Department (NMED) would not be necessary. Wetlands at Last Curve are discussed under wetlands in the next section. Since the area of disturbance exceeds one acre, the construction contractor will prepare a SWPPP as part of obtaining coverage under a National Pollutant Discharge Elimination System (NPDES) general construction activity permit. The SWPPP will include BMPs to minimize soil erosion and sediment transport including mitigation measures to protect water quality. Temporary erosion and sediment control plans will be included in the plan sets. Slope stabilization and drainage improvements would improve water quality through the reduction of erosion and sediment transport. 4.5 Wetlands Existing Conditions – Wetlands are identified by vegetation, soil, and hydrologic indicators diagnostic of wetland conditions as defined in the 1987 Corps of Engineers Wetland Delineation Manual (USACE, 1987). Wetlands are present outside of the project area at Last Curve. Potential Effects and Mitigation Measures – No wetlands are present at Texas Turn or Axle Bend Curve, but wetlands are adjacent to Last Curve. Construction activities will avoid the wetlands at Last Curve. Temporary fencing will be constructed around the wetlands to keep construction activities away from the wetlands. March 2013 10 CN 2101140
Page 1 and 2: Notice of Environmental Assessment
Page 4 and 5: TABLE OF CONTENTS 1.0 SUMMARY .....
Page 6 and 7: NM 532 Curve Correction Project Env
Page 8 and 9: Texas Turn MP 6.89-7.05 Last Curve
Page 10 and 11: San Juan Rio Arriba Taos Colfax Uni
Page 26 and 27: VICINITY MAP LEGEND INTENT SCALES V
Page 28 and 29: ℄ NM-532 PROPOSED RSS WALL LEFT S
Page 30 and 31: TYPICAL GEOGRID COVERAGE TYPICAL RS
Page 32 and 33: FACING UNIT REINFORCED SOIL SLOPE D
Page 34 and 35: NM 532 VICINITY MAP NTS Δ LEGEND E
Page 36 and 37: NM 532 VICINITY MAP NTS Δ LAST CUR
Page 38 and 39: From: To: Subject: Date: Wallace, L
Page 40 and 41: NEW MEXICO ENVIRONMENT DEPARTMENT O
Page 42: parties involved in the project to
Page 46 and 47: Bibliography Banks, P.E. undated. B

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