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The construction of each test infiltration basin was accomplished using a backhoe loader
and involved earthwork, temporary soils management, and backfilling and final grading.
With the exception of one test, basins were excavated to 5 feet below ground surface (feet‐
bgs) with excavated material stockpiled next to the basin. Native material was used to
create shallow berms for one test at the Oak Glen Creek Basins to test the infiltration
through undisturbed sediment at the ground surface. Ponded water depths typically ranged
from 2.5 and 3.0 feet.
Test basins were constructed with an approximate 1‐to‐1 horizontal‐to‐vertical slope on one
sidewall for public safety. At the completion of infiltration testing, each test basin was
backfilled with the excavated material, and the site was returned to its original, pre‐
disturbed grade.
General mobilization, testing, and demobilization tasks at each investigation site are
summarized below:
Excavation of a test recharge basin at each site;
Movement and staging of vehicles and heavy equipment along access routes and in
vicinity of infiltration test basin;
Temporary storage of excavated soils adjacent to the test basin;
Installation of construction fencing to ensure public safety and prevent vandalism of
water hoses and flow control equipment;
Placement of traffic‐rated ramps (to protect fire hose crossing public roads,
driveways, and/or sidewalks) and traffic‐control signs to direct vehicular and
pedestrian traffic;
Discharge of water into the test basin up to 14 days;
Backfilling the test basin with excavated material to return the site to pre‐disturbed
grade.
2.3. WATER SOURCE, FLOW CONTROL, AND TELEMETRY SYSTEM
Average vertical infiltration rates at each site ranged from less than 1 feet per day (feet/day)
up to approximately 50 feet/day. This equated to test water needs ranging from less than 5
gallons per minute (gpm) up to 200 gpm. Higher infiltration rates occurred in basins
underlain by a thick deposit of coarse‐grained vadose zone sediments (e.g., within existing
larger flood control facilities, Oak Glen Creek Basins, and Wildwood Creek). Lower
infiltration rates occurred in test basins underlain by finer‐grained sediments.
To accommodate the potentially broad range of test water needs, a direct connection to a
local fire hydrant owned by either Yucaipa Valley Water District (YVWD), South Mesa Water
company (SMWC), or Western Heights Water Company (WHWC) was used to supply test
water for each infiltration test. The use of a hydrant precluded the need for onsite water
storage and provided adequate positive pressure in the water conveyance system to
maintain flows into the basin required to achieve constant‐head conditions. Water retailers
include YVWD, SMWC, and WHWC.
Infiltration Testing at Eleven
Investigation Sites in the Yucaipa
Basin, Yucaipa Valley, CA 6 TODD GROUNDWATER
Yucaipa Sustainable Groundwater Management Agency - January 23, 2019 - Page 25 of 137