During the evaluation process, alternatives with fatal flaws were eliminated. At this point, specific design concept alternatives for the improvements are being developed. These alternatives will be evaluated and compared to select a recommended alternative that minimizes environmental impacts and meets the project objectives and engineering constraints. Back to Top Engineering Features Between the Santa Maria River and Wickenburg, the existing two-lane roadway traverses mostly undeveloped Lower Sonoran Desert, crossing the alluvial fan of the Date Creek Mountains. Surface soils in this area are fairly erodible and underlain with shallow cemented soils, together with granite and basaltic rock formations.
Drainages cross the corridor generally from northeast to southwest in well-defined arroyos.
Wash and Date Creek dominate the watershed and are currently bridged by US 93. The existing roadway, constructed between 1958 and 1964, is characterized by good horizontal alignment and rolling to flat vertical alignment, climbing into and out of the Santa Maria, Date Creek, and Wickenburg valleys. Along this segment, design concept alternatives will incorporate independent, divided highway alignments to best fit the terrain, avoid geotechnical problems, minimize earthwork, mitigate drainage problems, and result in the least impact to the natural environment. The existing roadway can generally be retained and reconstructed for one direction of travel. The new lanes will be situated on either side of the existing roadway, depending on drainage, terrain, and other factors.