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Results of infiltration testing indicate that the site is not suitable for recharge. The average
infiltration rate from constant‐head testing is only 0.1 feet/day (based on stabilized rates
observed after 4 days of testing), which is verified by measured infiltration rates from the
falling‐head test (0.18 to 0.19 feet/day).

Full‐scale basin initial and long‐term infiltration rates are predicted to be less than 0.1
feet/day.

Development of a recharge facility and any additional investigations are not recommended
at this site.

3.1.3. Chapman Heights Basin

A synopsis of the infiltration testing completed at the Chapman Heights Basin is shown on
Figure 4. As shown on Figure 1, and similar to the Tennessee Street Basin site, this site is
located north of the Western Heights Subbasin, the northwestern boundary which generally
coincides with the Western Heights Fault. Despite its upgradient location relative to the
Western Heights Subbasin and Western Heights Fault, the site is favorably located if
recharge water can migrate below regional clay layers in the Western Heights Subbasin and
replenish aquifers that support local groundwater production. No exploratory borings were
drilled in 2014 near this site, and depth to groundwater is unknown.

Results of infiltration testing indicate that the site is suitable for recharge. The average
infiltration rate from constant‐head testing is 10.2 feet/day (based on stabilized rates
observed after approximately 9 days of testing), which is generally verified by measured
infiltration rates from the falling‐head test (7.3 to 9.5 feet/day). The cause of the slight
decline in infiltration rate after Day 10 is unknown, it but does not appear to be significant.

A full‐scale basin initial infiltration rate is predicted at 5.1 feet/day, and a full‐scale long‐
term infiltration rate is predicted at 2.5 feet/day.

Pilot‐scale infiltration testing involving installation of monitoring wells north and south of
the Western Heights Fault is recommended, if the size of a potential full‐scale recharge
project is significantly larger than the existing storm detention basin.

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3.1.4. 10 Street and avenue E (EX‐7)
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A synopsis of the infiltration testing completed at the 10 Street and Avenue E Basin is
shown on Figure 5. As shown on Figure 1, this site straddles the Western Heights and
Calimesa Subbasin boundary, which coincides with the northeast‐trending Chicken Hills
Fault. The potential value of this site for recharge is contingent on the hydraulic connection
between the Calimesa Subbasin and the Western Heights Subbasin across the Chicken Hill
Fault. The relative location and proximity of the site to several mapped traces of the Chicken
Hills Fault to the west/northwest indicate that groundwater replenishment benefits may be
limited to the downgradient portion of the Calimesa Basin. Exploratory boring EX‐7 was
drilled in 2014 south of Avenue E and the test site. Depth to groundwater was measured at

Infiltration Testing at Eleven
Investigation Sites in the Yucaipa
Basin, Yucaipa Valley, CA 14 TODD GROUNDWATER

Yucaipa Sustainable Groundwater Management Agency - January 23, 2019 - Page 33 of 137