I-10 Twin Peaks Traffic Interchange, Environmental Assessment

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Affected Environment and Environmental Impacts October 2005 locations is proposed; therefore, widening the openings in the soil cement bank protection is proposed also. • Channels along Twin Peaks Road and Linda Vista Boulevard east of I-10 – Constructing a new channel along the north side of Twin Peaks Road is proposed. The proposed drainage improvements would provide higher capacity drainage structures under I-10 and its frontage roads and new facilities under Twin Peaks Road and Linda Vista Boulevard. As a result, the stormwater predicted to flow over I-10 and the westbound frontage road during high rainfall events would be routed under the roadways. The stormwater runoff that currently flows over the surface of El Camino de Mañana and Linda Vista Boulevard would be routed under the roadways in pipes and culverts. This system would protect the roadway structure and remove runoff from the paths of vehicles. The proposed improvements would improve overall drainage patterns; therefore, land uses near the project area would benefit from the additional capacity of the drainage structures. Mitigation The preferred alternative would improve drainage in the project area and would alter existing surface water drainage patterns into the Santa Cruz River. To prevent materials from entering the Santa Cruz River and its tributaries during construction, the contractor shall take precautions to prevent construction materials from being introduced into washes in accordance with Arizona Department of Transportation’s Standard Specifications for Road and Bridge Construction Section 104.09 (2000 Edition) and the Water Quality Standards in Title 18, Chapter 11 of the Arizona Administrative Code as administered by ADEQ. Excess waste material and construction debris would be disposed of at sites supplied by the contractor in accordance with Arizona Department of Transportation’s Standard Specifications for Road and Bridge Construction Section 107.11 Protection and Restoration of Property and Landscape (2000 Edition). Disposal shall be made at either municipal landfills approved under Title D of the Resource Conservation and Recovery Act (RCRA), construction debris landfills approved under Article 3 of the Arizona Revised Statutes 49-241 (Aquifer Protection Permit) administered by the ADEQ, or inert landfills. Conclusion The preferred alternative would widen the low flow channel of the Santa Cruz River to compensate for the roadway and bridge embankment fill placed within the high flow Santa Cruz River channel. The proposed drainage improvements would provide higher capacity drainage structures under I-10 and its frontage roads and new facilities under Twin Peaks Road and Linda Vista Boulevard. As a result, the stormwater predicted to flow over I-10, the westbound frontage road, El Camino Interstate 10 Traffic Interchange at Twin Peaks/Linda Vista 4-12 Project No.: NH-010-D (AIW) TRACS No.: 10 PM 236 H5838 01D
Affected Environment and Environmental Impacts October 2005 de Mañana, and Linda Vista Boulevard during high rainfall events would be routed under the roadways; therefore, land uses near the project area would benefit from the additional capacity of the drainage structures and runoff would be removed from the paths of vehicles. Ground Water Existing Conditions The aquifer underlying the Tucson metropolitan area is designated as the Tucson Active Management Area (AMA). This is a designation given to aquifers in areas where groundwater pumping is most severe (primarily urban and agricultural areas). Because these areas are most susceptible to depletion of water resources, they are carefully managed by the Arizona Department of Water Resources (ADWR) to ensure water supply resources for future use. Water levels continue to decrease in the Tucson AMA; however, these decreases have been mitigated by the use of Colorado River water to recharge the aquifers underlying the basin. Depths to groundwater in the Tucson AMA vary substantially depending on land surface elevations and proximity to natural drainage areas. According to the Preliminary Initial Site Assessment (PISA) prepared for this project, groundwater elevations in the study area are relatively shallow, typically less than 100 feet below ground surface. Groundwater conditions in the study area are affected by intermittent, but occasionally large, surface water flows in the Santa Cruz River. Surface water flows recharge the groundwater system in the vicinity of the Santa Cruz River as water infiltrates through the Santa Cruz River channel sediments to the underlying aquifer. Santa Cruz River channel recharge in the Upper Santa Cruz Valley Sub-basin is estimated at 31,000 acre-feet per year. Infiltration of treated effluent discharged to the Santa Cruz River from Pima County's regional wastewater treatment plants is not a component of this natural recharge estimate. Impacts No Build Alternative Under the no build alternative, no impacts to ground water would occur. Preferred Alternative Groundwater would not be encountered for the majority of proposed roadway construction activities. Roadway construction efforts would require relatively shallow ground surface disturbance on higher elevations and, therefore, would not encounter groundwater. Construction activities likely to encounter groundwater are those involving the construction of the new twin bridges over the Santa Cruz River. For construction of the bridges, groundwater would be encountered, especially during the preparation for and placement of bridge piers and abutments. Interstate 10 Traffic Interchange at Twin Peaks/Linda Vista 4-13 Project No.: NH-010-D (AIW) TRACS No.: 10 PM 236 H5838 01D
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Interstate 10 Traffic Interchange a
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Draft Environmental Assessment Octo
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Mitigation Measures October 2005
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Conclusion October 2005 Interstate
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Bibliography October 2005 CHAPTER 8
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Bibliography October 2005 Tetra Tec
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I-10 Twin Peaks Traffic Interchange, Environmental Assessment

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