Page 57 - _ 180314 Special Yucaipa GSA Packet

either have an approximate 1‐to‐1 horizontal‐to‐vertical slope and/or include a 2‐foot wide
ledge at 2.5 feet depth for public safety. At the completion of infiltration testing, each test
basin would be backfilled with the excavated material, and the site would be returned to its
original, pre‐disturbed grade. Due to the presence of shallow fine‐grained sediments
observed (Geoscience, 2014), it is recommended that the test infiltration basin depth be
increased to approximately 10 feet at the Oak Glen Creek Basins (EX‐2) site.

Tests conducted 14 days are expected to yield sufficient data to estimate the long‐term
infiltration capacity at each site. Based on our experience in areas with no significant vertical
or horizontal flow barriers, recharge rates are typically higher for the first few days of testing
but begin to decrease and eventually asymptote at a long‐term rate after several days. If
recharge rates asymptote prior to 14 days, testing may be halted. Potential costs savings
from a shortened test may result from less test water used and/or less site visits required by
the contractor to check on operation of equipment. However, a recommended fixed weekly
schedule (see Section 3) would limit potential cost savings on equipment rental costs.

Ground disturbing activities associated with infiltration testing are summarized below. In
general, these activities include:

 Excavation of a test recharge basin at each site (30’ x 30’ x 5’ deep);
 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;
 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.

1.3. SITE SECURITY AND FENCING

Several investigation sites are located on undeveloped land and natural drainages that are
easily accessible by the public. While some of the investigation sites are located within gated
parcels, it is recommended that each infiltration test basin be secured with temporary
construction fencing to ensure public safety and prevent vandalism of water hoses and flow
control equipment.

1.4. TRAFFIC CONTROL AND SIGNAGE

Traffic‐rated ramps should be used to protect fire hose crossing public roads, driveways,
and/or sidewalks. Traffic cones and caution signs should be placed to direct vehicular traffic
over the ramp and foot traffic onto the sidewalk around the ramp. Discussion with the City’s
traffic engineering department is needed to understand whether “sidewalk closed” signs are
required or ADA requirements must be met explicitly on a site‐by‐site basis.

Cones and a blinking barricade are recommended to direct any foot/bicycle traffic over
traffic ramps crossing sidewalks. Signage will be placed approximately 200 feet away on

Final Infiltration Test Work Plan for
Thirteen Investigation Sites
Yucaipa Valley, CA 4 TODD GROUNDWATER

Yucaipa Groundwater Sustainability Agency - March 14, 2018 - Page 56 of 226