HomeMy WebLinkAboutWSA-WVWD_CactusBasins-RWQCB-20160204EDMUND G. BROWN JR.
GOVERNOR
~ M~TTHEW RooRJauez · 1.. ~ ~ SECRETARY FOR
.,...., ENVIRONMENTAL PROTECTION .
--------------------··---------------------------------------··---··--------------~-----------------··---·
Santa Ana Regional Water Quality Control Board
February 8, 2016
Mr. Thomas J. Crowley, PE
General Manager
West Valley Water District
855 West Base Line Road
P.O. Box 920
. Rialto, CA 92377
(tcrowley@wvwd:org)
COMMENTS ON WEST VALLEY WATER DISTRICT'S TECHNICAL MEMORANDUM
REGARDING THE PROPOSED LONG-TERM PERMIT FOR DISCHARGE OF TREATED
GROUNDWATER INTO THE SAN BERNARDINO FLOOD CONTROL DISTRICT'S CACTUS
. BASINS #1 AND #2
Dear Mr. Crowley:
We have reviewed the above referenced Technical Memor9ndum (TM), dated January 27,
2016; which was prepared by the West Valley Water District (WVWD), and the "Flow and Solute
Transport rylodel Calibration of the Rialto-Colton Basin Groundwater Model" (Model Report),
dated December 1, 2015, which was prepared by your consultant, Geoscience. The TM is an
update to WVWD's October 2012 TM, and provides further technical analysis in response to the
concern by the San Bernardino County Flood Control District (SBCFCD) that WVWD's proposed
long-term use of the SBCFCD's Cactus Basins #1 and #2 for the discharge of treated
groundwater may adversely affect the movement of a perchlorate and trichloroethylene
contaminant plume that is present in the groundwater that underlies the basins. WVWD states
that Geoscience's Model Report is a consolidation and comparison of various model r~ns of
different groundwater models that have been developed over the past decade, and in
collaboration among the San Bernardino Valley Municipal Water District, WVWD, the. Goodrich
Corporation, the cities of Rialto and Colton, USEPA, CH2MHill consultants and the U.S.
Geological Survey.
Based on the modeling results, the data from previous discharges to Cactus Basins #1, #2, and
field measurements of groundwater elevation, WVWD and Geoscience conclude that:
1. "There is no significant change in the size of the geographic footprint of the perchlorate .
plumes with-or without recharge at the Cactus Basins; but concentrations are decreased
from dilution;" ·
2. "Water levels increased up to 2-ft in the vicinity of the recharge ponds as a result of
recharge versus no recharge. Water levels due to recharge were imperceptible elsewhere in
the Basin;"
WILLI!>.!~ RUH, (HAIR I KURT V. BERCHTOLD, EXECUTIVE OFFICER
c'") RECYCLED PAPER
I
Mr. Thomas Crowley -2-February 8, 2016
\
3. "The model predictive results show no anticipated significant groundwater contamination
impacts from the proposed Project, suggesting that no additional mitigation measures are
rieeded beyond those that have been previously planned and are in place."
We·have evaluated the groundwater treatment system design, a'nd the proposal for monthly and
quarterly discharges of the treated groundwater .into Cactus Basins #1 and #2 at a rate of 4
cubic feet per second, totaling 128 acre-feet per year. We have reviewed the data and
calculations in the attachments to WVWD's Technical Memorandum. WVWD states that the two
downgradient municipal supply wells ·(Rialto #6 and WVWD #11) .that are being pumped (to
generate water for the treatment and subsequent discharge to Cactus Basin #2) will capture the
· majority of any localized recharge that may result from percolation of the clean, treated water
into Cactus Basins #1 and #2. · ·
Monitoring data (USGS Cluster Well 1 S/5W-3A) indicate that the shallow groundwater
· underlying the Cactus Basins is not impacted by the perchlorate and trichloroethylene plume,
and that the plume is first present at a depth of about 1 00 feet below the groundwater table.
Based on the percolation data and infiltration calculations and the depth of the plume below the
groundwater table, we do not believe that the limited volume and the anticipated intermittent
occurrence of the discharge to the two basins will adversely impact the movement of the
perchlorate plume.
If you have any questions, please call Ann Sturdivant at (951) 782-4904, or send email to
ann.sturdivant@waterboards.ca.gov, or you may contact me at (951) 782-3286 or by e-mail at
kurt. berchtold@waterboards. ca.g ov ..
Sincerely,
Kurt V. Berchtold
Executive Officer
cc: Wayne Praskins, U.~. EPA Region IX (praskins.wayne@epa.gov)
WVWD_Cactus.:_Basins_02-04-2016