This talk will present the soup to nuts approach to specific alignment analysis performed for the State Route 62/Morongo Pass project.
California State Route 62 begins in the Coachella Valley in Riverside County, cuts north through the Little San Bernardino Mountains, then east through the Yucca Valley and Twentynine Palms, north of Joshua Tree National Park to the Arizona border. This alignment bisects the Sand to Snow National Monument and managed Conservation lands and Preserves. Several special-status species and large mammals occur in this area ranging from desert bighorn sheep and mountain lion to desert tortoise. Our study area includes the western portion from the Coachella Valley floor, up the Morongo Grade, through the Morongo Valley and up to the crest of the Yucca Grade. This is an approximate 12-mile study area that experiences traffic volumes between 21,000 and 26,000 Annual Average Daily Trips.
To better understand the movement patterns and risk to local large and focal species, the team reviewed existing connectivity modeling, but refined our evaluation to examine this smaller segment in greater detail. To that end, we reviewed Wildlife Vehicle Collision (WVC) data from various sources, performed WVC, track, and game camera studies and modeled light and noise effects at various crossing locations. WVC data identified hotspots in the Morongo Valley where there were limited available crossing structures and hardscape likely contributed to the vulnerability. Camera data was collected at eight structures and six nearby habitat areas between early 2019 and early 2020. Cameras captured images of a wide range of species including desert tortoise, desert bighorn sheep, black bear, mountain lion. Track data substantiated the presence of focal species in the study area.
A variety of constraints were identified, which included structure deficiencies, crossing structure gaps, human use at key areas, varying highway median heights, light and noise impacts, and adjacent land use/ownership. Importantly, it was determined that there was a significant pinch-point for desert bighorn sheep within the Morongo Grade portion. Following the analysis, the team provided recommendations that included a variety of site-specific measures, including overpasses at two locations, coordination with the local flood control agency to manage their structures in a mutually beneficial manner, strategic placement of fencing and barriers, and structure modifications to reduce noise and light effects.