Page 20 - Yucaipa Sustainable Groundwater Management Agency - Yucaipa SGMA

1. INTRODUCTION

The San Bernardino Valley Municipal Water District (Valley District) and its partner agencies
are evaluating the feasibility of recharging State Water Project (SWP) water and recycled
water and enhancing local stormwater capture in the Yucaipa Basin. Successful
management of the Yucaipa Basin conjunctively with available surface water supplies will
increase the basin safe yield to meet projected groundwater demands and help to achieve
sustainability goals and management criteria to be established in the Yucaipa Basin
Groundwater Sustainability Plan (GSP).

In March 2018, Valley District contracted Todd Groundwater to perform infiltration tests at
(up to) thirteen sites in the Yucaipa Basin. Infiltration testing represents an important step in
evaluating site recharge capacity and feasibility. Short‐term tests using field‐scale test basins
were selected to balance the need to test a reasonably‐sized area at each investigation site,
while considering the substantial number of sites and water delivery constraints of local fire
hydrants used for test water. Combined with the current understanding of the basin
hydrogeologic conditions, infiltration test results were used to satisfy the following project
objectives:

 Confirm site infiltration capacity and recharge suitability. Favorable conditions are
characterized by (1) predominantly coarse‐grained (sand/gravel) vadose zone
lithology that allow unhindered vertical migration of recharge water to the water
table; (2) sufficient depth to water and horizontal distance from vertical hydraulic
barriers (e.g., faults) to accommodate future recharge mounding; and (3) an
upgradient location relative to groundwater production areas/pumping depressions

 Develop planning‐level estimates of long‐term infiltration rates to support future
evaluation and design of recharge facilities to optimize groundwater water level,
storage, and safe yield and water quality benefits in the Yucaipa Basin

 Recommend additional field investigations (e.g., monitoring well construction and
pilot scale testing) to address remaining knowledge gaps at high‐priority
investigation sites

Guidelines for implementation of infiltration testing were developed in a Work Plan
developed by Todd Groundwater (Todd, 2017). Due to the inability to gain access to one
privately‐owned site (Garden Air Creek) and the de‐prioritization of a second site due to its
th
downgradient location in the Yucaipa Basin (Wildwood Creek at 6 Street), infiltration
testing was conducted at only eleven of the original thirteen investigation sites included in
the Work Plan. Two infiltration tests were conducted at the Oak Glen Creek Basins to assess
the significance of surficial low‐permeability sediments on infiltration rates. Accordingly, a
total of twelve infiltration tests were completed.

This report describes the infiltration test methods, activities, and results. Calculated
infiltration rates are presented along with preliminary estimates of long‐term infiltration

Infiltration Testing at Eleven
Investigation Sites in the Yucaipa
Basin, Yucaipa Valley, CA 1 TODD GROUNDWATER

Yucaipa Sustainable Groundwater Management Agency - January 23, 2019 - Page 20 of 137