Page 26 - Yucaipa Sustainable Groundwater Management Agency - Yucaipa SGMA
P. 26

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
   21   22   23   24   25   26   27   28   29   30   31