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County engineers: stormwater on Ocotillo Road follows historic ravines; gravel pit appears to detain, not divert, runoff
Summary
Engineering staff told the Board of Supervisors that contour maps and lidar show ravines that carry stormwater to Desert Rose and across Ocotillo Road; the gravel pit near the ridge appears to retain stormwater rather than increasing flow across the road, and the wash does not meet the county's 500 cubic-feet-per-second regulatory threshold.
Cochise County engineers told supervisors that recent inspections and contour mapping indicate stormwater in the Ocotillo Road area follows longstanding ravines and that the excavated pit on the ridge is retaining stormwater rather than increasing flows across Ocotillo Road.
Jackie Watkins, the county engineer, showed supervisors contour maps based on 2020 LiDAR and explained the location of two principal ravines upstream of property owner Michael (Mr.) Durham’s house. Watkins said the disturbed area at the pit is about 800 feet to the property line and roughly 1,000 feet to Ravine Number 1, and she described the pit footprint and elevations on the county’s maps.
“The bottom of the pit is 35 36. So this pit here is 14 feet deep,” Watkins said during the presentation, adding that the pit’s low area is roughly two acres and that much of the disturbed acreage is retained in the pit. “So that's about 50%. So there's less water flowing off that property today than there would have been in 1980 prior to any development on the property.”
Watkins told the board that the washes in the area do not exceed the county’s threshold for formal flood-control jurisdiction. She cited the county standard that the board regulates only watercourses that are either FEMA-designated floodplains or that exceed 500 cubic feet per second. “These washes do not have over 500 cubic feet per second,” she said.
Chairman Crosby and other supervisors pressed staff on whether the pit or berms had altered flow paths. Watkins said the berms at the pit’s north edge do not divert water out of its natural drainage path and that the drainage continues toward the established ravines and across Ocotillo Road to the San Pedro River watershed.
Staff acknowledged significant local erosion and “head cutting” in the wash near Durham’s property; Watkins said that head-cut erosion and private property alterations are civil matters between neighbors unless they create flow in a regulated watercourse. “If stormwater is less than the regulatory flood, the county doesn't get involved. It is a civil matter between the property owners,” she said, and added that property owners may agree among themselves to correct localized changes.
Ending: Supervisors and staff agreed to continue field visits and hold another public meeting for neighbors to respond to the engineering analysis; there was no county enforcement action announced at the work session.
