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Infiltration Test Results

Note: Flow rates into the basin averaged 18.16 to 18.31 gpm
(below minimum threshold of digital paddle meter);
thus infiltration rates were calculated based on
meter readings approximately every two to three days.
A B

E

A. Initial excavation of test infiltration basin
B. Flow control skid and temporary fencing
C. Post-infiltration potholing to evaluate
C subsurface moisture conditions
D. Dry soil conditions below shallow silt layer
occuring at 10-12 feet below the channel
E. Test in progress (Day 1)

DRY SOIL (SILT)
10-12 FEET BELOW
CHANNEL BOTTOM

C D

Conclusions:
Test Start Aug-06-2018
- Results of infiltration testing indicate that the site (within the channel) is not suitable for recharge.
Test End Aug-20-2018 - Full-scale basin initial infiltration rates (based on 50% of measured field-scale testing infiltration
Basin Dimensions (L x W) (ft) 41 x 21 10th Street and Avenue E rates) are estimated at 1.7 feet/day. Long-term infiltration rates (based on 50% of full-scale basin initial
Test Site infiltration rates) are estimated at 0.9 feet/day.
Average Water Height (ft) 2.5
" ) - Low infiltration rates appear to be due to low-permeability clayey silt layer, the top of which occurs
2
Infiltrating Area Basin Bottom (ft ) 960 at 10-12 feet depth. Dry soil conditions were observed below the clayey silt layer at end of testing.
2
Infiltrating Area Basin Bottom + Walls (ft ) 1,270 Hydrant - No fine-grained deposits were identified in EX-5 above 94 feet-bgs; fine-grained material appears
Total Water Added (gallons) 270,060 to be associated with sediment load from natural stormflows.
Boring
Total Water Added (acre-feet) 0.8 EX-5 Recommendations:
High (ft/d) 4 X Y - Near-surface coarse-grained sediments found in Wildwood Creek at California Street, appear to have
Infiltration Rate limited thickness and are underlain by a fine-grained matrix associated with natural stormflows,
Low (ft/d) 2.94
(Constant-Head) which limit infiltration significantly.
Average (ft/d) 3.5 - No additional actions are recommended at this site.
Infiltration Rate High (ft/d) 3.07
(Falling-Head) Low (ft/d) 2.4 ´ Figure 6
Full-Scale Basin Est. Initial Infiltration Rate (ft/d) 1.7 0 400 Feet Wildwood Creek
Full-Scale Basin Est. Long-Term Infiltration Rate (ft/d) 0.9 at California Street

Yucaipa Sustainable Groundwater Management Agency - January 23, 2019 - Page 50 of 137