Page 42 - Yucaipa Sustainable Groundwater Management Agency - Yucaipa SGMA

Very low infiltration rates associated with fine‐grained vadose zone sediments were
measured at the Oak Glen Creek at Western Heights and Dunlap Channel sites (predicted
long‐term rates of 0.4 and 0.03 feet/day). A further complication and challenge of operating
an in‐channel recharge facility is the need for potentially frequent basin maintenance to
remove debris associated with storm events that may further reduce surface infiltration
rates.

Calimesa/Oak Glen Subbasins

The City of Yucaipa at California Street site appears to provide the best combination of
infiltration capacity (predicted long‐term rate of 4.0 feet/day) and location from a
hydrogeologic perspective. The site is favorably located upgradient of key production wells
in the Calimesa Subbasin and is underlain by coarse‐grained deposits that should allow for
uninhibited vertical migration of recharge water to the underlying water table (342 ft‐bgs in
2014). The site is also located a significant distance from geologic faults that form most of
the boundaries of the Calimesa Subbasin.

The Wildwood Creek Basins provides a high infiltration capacity (predicted long‐term rate of
9.8 feet/day). The site is located in the Oak Glen Creek Subbasin upgradient of aquifers in
the Calimesa Subbasin relied upon for groundwater production. The site is underlain by
highly permeable deposits that should allow for uninhibited vertical migration of recharge
water to the underlying water table. Available vadose zone storage may be limited by the
existing depth to water of approximately 100 feet‐bgs. The degree to which recharge water
can flow across the South Mesa Barrier into the Calimesa Subbasin is a critical knowledge
gap that requires further investigation and/or evaluation.

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The 10 Street at Avenue E site appears to provide a good infiltration capacity (predicted
long‐term rate of 3.2 feet/day). Clay sediments found in nearby exploratory borehole EX‐7
(south of Avenue E outside of the channel) down to 25 feet‐bgs were not encountered
during test basin excavation. Despite having good infiltration capacity, the site is poorly
located adjacent to and east of the Chicken Hill Fault in the Calimesa Subbasin. The potential
value of this site for recharge is contingent on potential benefits this site can provide to the
Western Heights Subbasin. Water level differences of approximately 300 feet across the
Chicken Hill Fault indicate that the hydraulic connection between the site and Western
Heights Subbasin is expected to be poor. However, further investigation and/or evaluation is
needed to confirm this interpretation.

Low infiltration rates associated with shallow fine‐grained sediments were measured at the
Wildwood Creek at California Street site (predicted long‐term rate of 0.9 feet/day). Similar
to the challenges identified for the two channel sites in the Western Heights Subbasin,
operating an in‐channel recharge facility could potentially frequent basin maintenance to
remove debris associated with storm events.

Infiltration Testing at Eleven
Investigation Sites in the Yucaipa
Basin, Yucaipa Valley, CA 21 TODD GROUNDWATER

Yucaipa Sustainable Groundwater Management Agency - January 23, 2019 - Page 40 of 137