Page 54 - _ 180314 Special Yucaipa GSA Packet

Flood Control District (6 sites), City of Yucaipa (4 sites), South Mountain Water Company (1
site), and private parties (2 sites). All thirteen investigation sites are located within an
approximately 3‐mile radius of downtown Yucaipa, California.

Figures 1 and 2 show the locations of the thirteen investigation sites. Areas of disturbance,
including footprints of proposed test infiltration basins and ingress/egress routes for heavy
machinery and support vehicles, are shown on the inset maps. Areas for temporary
stockpile of excavated soils and potential locations for optional onsite water storage tanks
are not currently shown, as water sources and onsite soil management requirements have
not yet been finalized.

The seven investigation sites shown on Figure 1 (adjacent to existing exploratory boreholes
EX‐1, EX‐2, EX‐3, EX‐4, EX‐5, EX‐6, and EX‐9) are located within stream channels (Wilson
Creek, Oak Glen Creek, and Yucaipa Creek) or existing storm detention basin facilities under
jurisdiction of SBCFCD. All seven sites are located on parcels owned by SBCFCD (highlighted
in red).

The six investigation sites shown on Figure 2 are owned by the City of Yucaipa (Tennessee
Street Basins, Chapman Heights Basins, and Dunlap Channel), South Mountain Water
Company (adjacent to exploratory borehole EX‐7), and private owners (adjacent to
exploratory boreholes EX‐10 and EX‐11) and are not under the jurisdiction of SBCFCD.

A summary of information for each investigation site (including the owner parcel
information, geographic coordinates, and directions to each site) is presented in Table 1.
Site investigation photos taken during the April 27, 2016 site reconnaissance are provided in
Appendix F.

1.2. INFILTRATION TEST METHODOLOGY

Each infiltration test will involve the temporary construction of a 30‐foot by 30‐foot test
1
infiltration basin , controlled discharge of water into the test basin, and monitoring of water
volume added and ponded water height over a 2‐week period. The construction of each test
infiltration basin will generally be accomplished using a backhoe loader and will involve
earthwork, temporary soils management, and backfilling and final grading. It is envisioned
that the test basins would either be excavated to either (a) 5 feet in depth with excavated
material stockpiled next to the basin (or acceptable location as determined by pertinent
permitting regulatory agencies), or (b) 2‐3 feet in depth with excavated native material used
to create shallow berms. For both methods, the design would allow for ponded water
depths of up to approximately 2‐3 feet with 1 to 2 feet of freeboard. The basin walls would

1 A 30‐foot by 30‐foot basin is recommended. However, a smaller test basin footprint (e.g., 20‐foot by
20‐foot) can be used to reduce water needs for sites where a direct water source is not available and
onsite water storage tanks(s) and trucking of water to the site is needed. While a smaller test basin
may increase the effect of subsurface horizontal flows on surface infiltration rates, infiltration test
results from smaller test basins can still provide meaningful results.

Final Infiltration Test Work Plan for
Thirteen Investigation Sites
Yucaipa Valley, CA 2 TODD GROUNDWATER

Yucaipa Groundwater Sustainability Agency - March 14, 2018 - Page 54 of 226