NM 532 Curve Correction Project - New Mexico Department of ...
NM 532 Curve Correction Project - New Mexico Department of ... NM 532 Curve Correction Project - New Mexico Department of ...
NM 532 Curve Correction Project Environmental Assessment 3.0 ALTERNATIVES CONSIDERED This section discusses the alternatives under consideration for meeting the project purpose and need. The alternatives were developed and refined during the development of preliminary project concepts and plans. The Recommended Build Alternative was carried through the environmental analysis discussed in Section 4.0 of this document. 3.1 Alternatives Considered but Eliminated from Further Consideration New roadway alternatives were considered but eliminated because of their high costs, challenging constructability, and potential for substantial environmental damage with construction in active stream channels and undisturbed habitat (Smith, 2008). Construction of a gondola is still considered a viable alternative, but no funding for a gondola is expected to be identified or available within the foreseeable future. 3.2 No-Build Alternative Under the No Build Alternative, roadway improvements would not be constructed. Sharp curves would not be modified. The roadway would not be reconstructed. No guardrail would be added. Safety concerns related to the sharp curves and steep drop-offs without guardrail would continue. NMDOT would continue to implement a high level of maintenance in order to keep NM 532 functional. The average annual maintenance cost for the curves has been approximately $6,000. 3.3 Recommended Build Alternative Roadway The existing roadway would be reconstructed from the BIA 21 / Eagle Lakes intersection at MP 0.0 to the Ski Apache entrance at MP 12.0. The design speed would be 40 mph. Sharp curves and steep grade sections would have a 20-35 mph design speed. The posted speed limit would be 35 mph and 15-30 mph at sharp curves and steep grades. The typical section would consist of two 11-foot travel lanes, two 3- foot paved shoulders, and two 2.5-foot tapers. In some areas, additional fill would be excavated off-site and placed for the proposed typical section. RSS walls, guardrail, and signage would be installed in some sections. Curves The following three curves are proposed for extensive reconstruction: Texas Turn at MP 6.89-7.05, Axle Bend Curve at MP 8.21-8.37, and Last Curve at MP 11.86-11.95 (see Figures 3.1-3.3). Work would entail increasing the curve radii and correcting the curve grades. At each curve, a retained soil system (RSS) wall would be constructed using additional native fill. The RSS would consist of a geo-grid embankment constructed at a 0.5:1 slope with rock-filled baskets for the wall face. Perforated drainpipes and subsurface drain outlets would be installed as part of the RSS wall. Guardrail would be installed at the top of the embankment. Energy dissipaters or other similar slope protection measures would be installed in areas where drainage has caused severe erosion. On the upslope side of Axle Bend Curve, some rock would be excavated and removed. No blasting would occur. Rock or slope protection would be used to create a stabilized rock-cut face only if unstable rock is encountered. Paved parking areas/pull offs would be constructed at Texas Turn and Last Curve. Drainage Drainage structures would be repaired to improve drainage at Last Curve, and rip-rap would be installed in some areas. At the three curves, perforated drainpipes and subsurface drain outlets would be installed as part of the RSS wall. March 2013 7 CN 2101140
NM 532 Curve Correction Project Environmental Assessment Right-of-way NMDOT would continue to utilize its U.S. Forest Service permitted right-of-way along NM 532. No additional right-of-way would be needed at the curves. Construction and Sequencing The reconstruction of the three curves would be constructed in a single phase. Construction would begin in 2013. Figure 3.1 Photograph of Texas Turn. Figure 3.2 Photograph of Axle Bend Curve. March 2013 8 CN 2101140
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- Page 26 and 27: VICINITY MAP LEGEND INTENT SCALES V
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- Page 30 and 31: TYPICAL GEOGRID COVERAGE TYPICAL RS
- Page 32 and 33: FACING UNIT REINFORCED SOIL SLOPE D
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- Page 38 and 39: From: To: Subject: Date: Wallace, L
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<strong>NM</strong> <strong>532</strong> <strong>Curve</strong> <strong>Correction</strong> <strong>Project</strong> Environmental Assessment<br />
3.0 ALTERNATIVES CONSIDERED<br />
This section discusses the alternatives under consideration for meeting the project purpose and need. The<br />
alternatives were developed and refined during the development <strong>of</strong> preliminary project concepts and<br />
plans. The Recommended Build Alternative was carried through the environmental analysis discussed in<br />
Section 4.0 <strong>of</strong> this document.<br />
3.1 Alternatives Considered but Eliminated from Further Consideration<br />
<strong>New</strong> roadway alternatives were considered but eliminated because <strong>of</strong> their high costs, challenging<br />
constructability, and potential for substantial environmental damage with construction in active stream<br />
channels and undisturbed habitat (Smith, 2008). Construction <strong>of</strong> a gondola is still considered a viable<br />
alternative, but no funding for a gondola is expected to be identified or available within the foreseeable<br />
future.<br />
3.2 No-Build Alternative<br />
Under the No Build Alternative, roadway improvements would not be constructed. Sharp curves would<br />
not be modified. The roadway would not be reconstructed. No guardrail would be added. Safety<br />
concerns related to the sharp curves and steep drop-<strong>of</strong>fs without guardrail would continue. <strong>NM</strong>DOT<br />
would continue to implement a high level <strong>of</strong> maintenance in order to keep <strong>NM</strong> <strong>532</strong> functional. The<br />
average annual maintenance cost for the curves has been approximately $6,000.<br />
3.3 Recommended Build Alternative<br />
Roadway<br />
The existing roadway would be reconstructed from the BIA 21 / Eagle Lakes intersection at MP 0.0 to the<br />
Ski Apache entrance at MP 12.0. The design speed would be 40 mph. Sharp curves and steep grade<br />
sections would have a 20-35 mph design speed. The posted speed limit would be 35 mph and 15-30 mph<br />
at sharp curves and steep grades. The typical section would consist <strong>of</strong> two 11-foot travel lanes, two 3-<br />
foot paved shoulders, and two 2.5-foot tapers. In some areas, additional fill would be excavated <strong>of</strong>f-site<br />
and placed for the proposed typical section. RSS walls, guardrail, and signage would be installed in<br />
some sections.<br />
<strong>Curve</strong>s<br />
The following three curves are proposed for extensive reconstruction: Texas Turn at MP 6.89-7.05, Axle<br />
Bend <strong>Curve</strong> at MP 8.21-8.37, and Last <strong>Curve</strong> at MP 11.86-11.95 (see Figures 3.1-3.3). Work would<br />
entail increasing the curve radii and correcting the curve grades. At each curve, a retained soil system<br />
(RSS) wall would be constructed using additional native fill. The RSS would consist <strong>of</strong> a geo-grid<br />
embankment constructed at a 0.5:1 slope with rock-filled baskets for the wall face. Perforated drainpipes<br />
and subsurface drain outlets would be installed as part <strong>of</strong> the RSS wall. Guardrail would be installed at<br />
the top <strong>of</strong> the embankment. Energy dissipaters or other similar slope protection measures would be<br />
installed in areas where drainage has caused severe erosion. On the upslope side <strong>of</strong> Axle Bend <strong>Curve</strong>,<br />
some rock would be excavated and removed. No blasting would occur. Rock or slope protection would<br />
be used to create a stabilized rock-cut face only if unstable rock is encountered. Paved parking areas/pull<br />
<strong>of</strong>fs would be constructed at Texas Turn and Last <strong>Curve</strong>.<br />
Drainage<br />
Drainage structures would be repaired to improve drainage at Last <strong>Curve</strong>, and rip-rap would be installed<br />
in some areas. At the three curves, perforated drainpipes and subsurface drain outlets would be installed<br />
as part <strong>of</strong> the RSS wall.<br />
March 2013 7 CN 2101140
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