Page 32 - Yucaipa Sustainable Groundwater Management Agency - Yucaipa SGMA

It is recognized that in a homogeneous and unbounded vadose zone, measured infiltration
rates for a field‐scale test basin will be higher than infiltration rates for a full‐scale basin due
to a greater contribution of horizontal flow beneath the field‐scale test basin. Additionally,
physical clogging of a recharge basin is likely to reduce infiltration rates over time. These
factors were considered to predict initial and long‐term infiltration rates at each
investigation site for a full‐scale basin, as shown below in Table 3. Assumptions used to
develop these estimates are described in more detail below.

Table 3
Estimated Initial and Long‐Term Infiltration Rates for a Full‐Scale Basin

Constant‐Head
Estimated Full‐Scale
Adjacent Field‐Scale
Infiltration Rate
Test Site Exploratory Infiltration Rate
Boring Average Initial a Long‐Term b
(ft/d) (ft/d) (ft/d)
Tennessee Street Basins 10.8 5.4 2.7
Dunlap Channel 0.1 0.1 0.03
Chapman Heights Basin 10.2 5.1 2.5
10th Street and Avenue E EX‐7 12.7 6.4 3.2
Wildwood Creek at California Street EX‐5 3.5 1.7 0.9
Wilson Creek Basins EX‐1 7.4 3.7 1.8
City of Yucaipa at California Street EX‐5 16.0 8.0 4.0
Wilson Creek III EX‐3 52.0 26.0 13.0
Oak Glen Creek Basins ‐ Excavated EX‐2 21.0 10.5 5.2
Wildwood Creek Basins EX‐4 39.0 19.5 9.8
Oak Glen Creek Basins ‐ Bermed EX‐2 5.6 2.8 2.8
Oak Glen Creek at Western Heights EX‐9 1.4 0.7 0.4
a ‐ Initial Full‐Scale Infiltration Rate is estimated to be 50 percent of average constant‐head
infiltration rate from field‐scale testing to account for decreased horizontal flow component
in full‐scale test basin.
b ‐ Long‐Term Full‐Scale Infiltration Rate is estimated to be 50 percent of the Initial Full‐
Scale Infiltration Rate to account for expected physical clogging of the basin bottom from
SWP water. For "Oak Glen Creek Basins (EX‐2) ‐ Bermed", long‐term infiltration rate is the
same as initial full‐scale infiltration rate, because the basin bottom is already significantly
clogged. Actual long‐term rates will be dependent on the specific site recharge goal and
implementation of a basin maintenance plan.

The degree to which field‐scale infiltration rates may overestimate full‐scale basin
infiltration rates is dependent on the relative difference in basin sizes. The future recharge
basin area at each investigation site is currently unknown, and site‐specific consideration
was outside the scope of this study. For this study, a uniform factor of 50 percent is applied
to infiltration rates from field‐scale infiltration tests to predict infiltration rates in a full‐scale

Infiltration Testing at Eleven
Investigation Sites in the Yucaipa
Basin, Yucaipa Valley, CA 11 TODD GROUNDWATER

Yucaipa Sustainable Groundwater Management Agency - January 23, 2019 - Page 30 of 137