HomeMy WebLinkAboutProp 1 PCE Plume Characterization Project - Planning Project OutlinePCE Plume Characterization Project
City of San Luis Obispo
PLANNING PROJECT
PROJECT COMPLETION DATE
December 30, 2022
PROJECT COSTS
Prop 1 GWGP Funds: $1,996,575
Local Cost Share: $231,317
TOTAL PROJECT COST: $2,227,892
PROJECT PURPOSE
The primary purpose of the City of San
Luis Obispo’s PCE Plume Characterization
Project is to conduct a remedial
investigation and feasibility study to
characterize the PCE plume and evaluate
and develop alternatives for the clean-up
(e.g., treatment) and prevention of PCE
contamination in drinking water wells in
the San Luis Valley area of the Basin.
PROJECT SCOPE
The project scope included preparation of a
Work Plan to gather existing background
data on the plume and prepare a plan to
obtain additional groundwater and soil data
to fill gaps in the plume understanding.
Based on the Work Plan recommendations,
four existing wells were evaluated, and
exploratory borings were drilled, sampled
(soil and groundwater), and tested at 30
locations at various depths. The resulting
data was used to prepare a Remedial
Investigation Report which delineated the
current understanding of the basin
properties and the plume extents. Using the
Remedial Investigation Report findings, a
flow-based groundwater model was
prepared and used to identify potential
extraction wells for treatment of pumped
water. A Feasibility Study was prepared using
the flow and capture information from the
groundwater model to evaluate potential
well head treatment for PCE removal to
allow use of the treated water in the City’s
drinking water system. The community was
kept up to date on the project through
updates to the City’s webpage,
advertisements, and a public meeting.
CONTACT
Nick Teague
City of San Luis Obispo Public Utilities
Water Resources Program Manager
879 Morro Street, San Luis Obispo, CA 93401
nteague@slocity.org
805.781.7217
ACKNOWLEDGEMENTS
Water Systems Consulting, Inc.
Cleath-Harris Geologists
BESST Inc.
Gregg Drilling
BENEFITS
• The PCE plume was better
delineated and PCE
concentration contours were
mapped.
• A groundwater flow model was
prepared showing potential
capture areas and locations for
3extraction wells
• Treatment options for
extraction wells were
evaluated, with granular
activated carbon being the
preferred option.
• Extraction wells look feasible
for plume treatment with a
future implementation project.
LESSONS LEARNED
• Needed to account for RWQCB
sampling requirements, which
added sonic boring, removed
soil vapor, and required
revision of the WP which
slowed down exploratory
boring and increased the
project budget.
• Caltrans encroachment permits
became a critical path item, and
Caltrans’ jurisdiction extended
further than originally
anticipated, need to coordinate
with Caltrans earlier.
• Analytical laboratories are
operating at capacity right now
which extended time required
to obtain results, need to build
in allowance for laboratory
delays.
• Exploratory borings required
night work in many locations in
the City because of traffic
closure limitations which
increased staffing needs for
observation. In the future, need
to be aware of special working
hour limitations.
NEXT STEPS
The next steps in this Project, which has
applied for Prop 1 Round 3 funding, will be
siting and installing a monitoring well network,
creating a fate and transport groundwater
model to verify the initial treatment
recommendations followed by implementation
of the recommended pump and treat systems
to remove PCE from the plume affecting the
San Luis Valley area of the Basin.