REMEDIATION SYSTEM EVALUATION
SELMA PRESSURE TREATING SUPERFUND SITE
SELMA, CALIFORNIA
Report of the Remediation System Evaluation,
Site Visit Conducted at the Selma Pressure Treating Superfund Site
November 7-8, 2001
Final Report Submitted to Region 9
January 31,2002
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NOTICE
Work described herein was performed by GeoTrans, Inc. (GeoTrans) and the United States Army Corps
of Engineers (USAGE) for the U.S. Environmental Protection Agency (U.S. EPA). Work conducted by
GeoTrans, including preparation of this report, was performed under Dynamac Contract No. 68-C-99-
256, Subcontract No. 91517. Mention of trade names or commercial products does not constitute
endorsement or recommendation for use.
This document (EPA 542-R-02-008u) may be downloaded from EPA's Technology Innovation Office
website at www.epa.gov/tio or www.cluin.org/rse.
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EXECUTIVE SUMMARY
The Selma Pressure Treating site is located 15 miles south of Fresno, adjacent to the city limits of Selma,
California and has subsurface contamination from a former wood treating facility. The site occupies
approximately 40 acres, including the 14-acre former wood treating and storage facility and a 26-acre
neighboring vineyard. Zoned for heavy use, the site is located in a transition zone between agricultural,
residential, and industrial areas. Drippings from the former wood treating processes have led to both soil
and groundwater contamination beneath the former facilities. The primary contaminant of concern is
chromium, predominantly found as hexavalent chromium, its more mobile state. Remedial investigations of
the contamination began in 1984, and by 1991 soil cleanup activities had started. Approximately 18,000
cubic yards of contaminated soil have been addressed, and an additional contaminated soil will be
addressed in the future.
A pump and treat system began operation in September 1998 to address the chromium contamination in
groundwater. The system consists of seven extraction wells, a treatment plant that removes chromium
through a co-precipitation process, and discharge of treated water to onsite percolation ponds.
A Remediation System Evaluation (RSE) was conducted on the system in November 2001. A RSE
involves a team of expert hydrogeologists and engineers, independent of the site, conducting a third-party
review of site operations. The evaluation includes reviewing site documents, visiting the site for up to 1.5
days, and compiling a report that includes recommendations to improve the system.
The RSE team found the site managers and contractor committed to system optimization and cost-effective
operation. Recommendations made by the RSE team to improve system effectiveness include the
following:
An analysis of the capture zone provided by the extraction system should be conducted to
determine if site-related groundwater contamination is adequately contained. This analysis should
consist of the following three items:
The plume boundaries, both horizontal and vertical, should be clearly delineated and
plotted for each sampling event. From these plume maps, target capture zones should be
determined. Trend analyses of chromium concentrations in each sampled well on an
annual basis would also give an indication of the progress of the remedy.
The water level measurements that are collected during each sampling event should be
used to develop potentiometric surface maps. From these maps groundwater flow
directions and estimated capture zones may be determined and compared to the target
capture zones drawn from the plume maps. Analyses of the historical and future
potentiometric surface maps will provide site hydrogeologists with better insight into
groundwater flow beneath the site
The groundwater flow model used to analyze the capture zone during system design should
be updated and recalibrated using historical water level measurements. In addition,
improved estimates of natural recharge and recharge from the percolation ponds should be
determined and used in modeling efforts. Once the model has been recalibrated, it should
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be used for particle tracking to provide estimates of the extraction system capture zone in
both vertical and horizontal directions.
The groundwater flow model can also be used to optimize the extraction system by relocating wells
or adjusting pumping rates. When the optimized extraction system is selected and implemented,
water level measurements from the regularly scheduled sampling events should be used to
recalibrate and update the groundwater flow model. Eventually, the groundwater flow model
should be able to reproduce water levels measured during the various pumping scenarios
implemented at the site.
A contingency plan should be developed in case contaminant concentrations above MCLs are
detected in nearby residential wells.
These recommendations might require approximately $39,000 in capital costs and might increase annual
costs by approximately $7,000 per year.
The only recommendation to reduce life-cycle cost is to delist the sludge generated from the groundwater
treatment plant. The sludge from the plant is currently listed as hazardous waste from a wood treating
facility thereby requiring it to be disposed of as hazardous waste. The sludge is generated from
groundwater treatment, passes TCLP testing, and should be delisted so that it can be disposed of as
nonhazardous waste. Implementing this recommendation to reduce costs may result in savings during
operations and maintenance and could offset initial investments and costs associated with recommendations
for enhanced system effectiveness and technical improvement.
Finally, the RSE team provides additional recommendations regarding site close out, including developing
an exit strategy and addressing the remaining soil contamination.
A summary of recommendations, including estimated costs and/or savings associated with those
recommendations is presented in Section 7.0 of the report.
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PREFACE
This report was prepared as part of a project conducted by the United States Environmental Protection
Agency (USEPA) Technology Innovation Office (TIO) and Office of Emergency and Remedial Response
(OERR). The objective of this project is to conduct Remediation System Evaluations (RSEs) of pump-
and-treat systems at Superfund sites that are "Fund-lead" (i.e., financed by USEPA). RSEs are to be
conducted for up to two systems in each EPA Region with the exception of Regions 4 and 5, which already
had similar evaluations in a pilot project.
The following organizations are implementing this project.
Organization
Key Contact
Contact Information
USEPA Technology Innovation
Office
(USEPA TIO)
Kathy Yager
11 Technology Drive (ECA/OEME)
North Chelmsford, MA 01863
phone: 617-918-8362
fax: 617-918-8427
yager.kathleen@epa.gov
USEPA Office of Emergency and
Remedial Response
(OERR)
Paul Nadeau
1200 Pennsylvania Avenue, NW
Washington, DC 20460
Mail Code 5201G
phone: 703-603-8794
fax:703-603-9112
nadeau.paul@epa.gov
GeoTrans, Inc.
(Contractor to USEPA TIO)
Doug Sutton
GeoTrans, Inc.
2 Paragon Way
Freehold, NJ 07728
(732) 409-0344
Fax: (732) 409-3020
dsutton@geotransinc.com
Army Corp of Engineers:
Hazardous, Toxic, and Radioactive
Waste Center of Expertise
(USAGE HTRW CX)
Dave Becker
12565 W. Center Road
Omaha, NE 68144-3869
(402) 697-2655
Fax: (402) 691-2673
dave j .becker@nwd02 .usace .army .mil
in
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The project team is grateful for the help provided by the following EPA Project Liaisons.
Region 1
Region 2
Region 3
Region 4
Region 5
Darryl Luce and Larry Brill
Diana Curt
Kathy Davies
Kay Wischkaemper
Dion Novak
Region 6
Region 7
Region 8
Region 9
Region 10
Vincent Malott
Mary Peterson
Armando Saenz and
Herb Levine
Bernie Zavala
Richard Muza
They were vital in selecting the Fund-lead pump and treat systems to be evaluated and facilitating
communication between the project team and the Remedial Project Managers (RPM's).
IV
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TABLE OF CONTENTS
EXECUTIVE SUMMARY i
PREFACE iii
TABLE OF CONTENTS v
1.0 INTRODUCTION 1
1.1 PURPOSE 1
1.2 TEAM COMPOSITION 1
1.3 DOCUMENTS REVIEWED 2
1.4 PERSONS CONTACTED 2
1.5 SITE LOCATION, HISTORY, AND CHARACTERISTICS 3
1.5.1 LOCATION 3
1.5.2 POTENTIAL SOURCES 3
1.5.3 HYDROGEOLOGIC SETTING 3
1.5.4 DESCRIPTION OF GROUND WATER PLUME 4
2.0 SYSTEM DESCRIPTION 5
2.1 SYSTEM OVERVIEW 5
2.2 EXTRACTION SYSTEM 5
2.3 TREATMENT SYSTEM 5
2.4 MONITORING PROGRAM 6
3.0 SYSTEM OBJECTIVES, PERFORMANCE AND CLOSURE CRITERIA 7
3.1 CURRENT SYSTEM OBJECTIVES AND CLOSURE CRITERIA 7
3.2 TREATMENT PLANT OPERATION GOALS 7
4.0 FINDINGS AND OBSERVATIONS FROM THE RSE SITE VISIT 8
4.1 FINDINGS 8
4.2 SUBSURFACE PERFORMANCE AND RESPONSE 8
4.2.1 WATER LEVELS 8
4.2.2 CAPTURE ZONES 8
4.2.3 CONTAMINANT LEVELS 9
4.3 COMPONENT PERFORMANCE 10
4.3.1 WELL PUMPS AND TRANSDUCERS 10
4.3.2 EQUALIZATION TANK 10
4.3.3 REACTOR 10
4.3.4 FLASH Mix AND FLOCCULATION TANKS 11
4.3.5 CLARIFIER 11
4.3.6 SOLIDS HOLDING TANK/FILTER PRESS 11
4.3.7 FlLTERFEED TANK 11
4.3.8 MULTIMEDIA FILTERS 11
4.3.9 EFFLUENT TANK (FINAL PH ADJUSTMENT) 11
4.3.10 SYSTEM CONTROLS 11
4.4 COMPONENTS OR PROCESSES THAT ACCOUNT FOR MAJORITY OF MONTHLY COSTS 12
4.4.1 UTILITIES 12
4.4.2 NON-UTILITY CONSUMABLES AND DISPOSAL Cos 12
4.4.3 LABOR 13
4.4.4 CHEMICAL ANALYSIS 13
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4.5 RECURRING PROBLEMS OR ISSUES 13
4.6 REGULATORY COMPLIANCE 13
4.7 TREATMENT PROCESS EXCURSIONS AND UPSETS, ACCIDENTAL CONTAMINANT/REAGENT RELEASES . 13
4.8 SAFETY RECORD 13
5.0 EFFECTIVENESS OF THE SYSTEM TO PROTECT HUMAN HEALTH AND THE ENVIRONMENT . 14
5.1 GROUND WATER 14
5.2 SURFACE WATER 14
5.3 AIR 14
5.4 SOILS 14
5.5 WETLANDS AND SEDIMENTS 14
6.0 RECOMMENDATIONS 15
6.1 RECOMMENDED STUDIES TO ENSURE EFFECTIVENESS 15
6. .1 REGULARLY ANALYZE DATA AND CAPTURE ZONES AND REPORT RESULTS 15
6. .1.1 UPDATE CONTAMINANT PLUME MAPS AND ANALYZE TRENDS IN CONCENTRATIONS 15
6. .1.2 ANALYZE WATER LEVEL MEASUREMENTS AND DEVELOP POTENTIOMETRIC SURFACE MAPS . 16
6. .1.3 RECALIBRATE THE GROUNDWATER FLOW MODEL AND USE SIMULATIONS FOR CAPTURE ZONE
ANALYSES 16
6. .2 USE MODEL SIMULATIONS TO OPTIMIZE LOCATIONS FOR NEW EXTRACTION WELLS 18
6. .3 DEVELOP A CONTINGENCY PLAN FOR EXCEEDENCES IN LOCAL GROUNDWATER WELLS .... 18
6.2 RECOMMENDED CHANGES TO REDUCE COSTS 18
6.2.1 DISPOSE OF SLUDGE AS NON-HAZARDOUS WASTE 18
6.3 MODIFICATIONS INTENDED FOR TECHNICAL IMPROVEMENT 19
6.3.1 REPAIRLEAKS INTHEPLANT 19
6.4 MODIFICATIONS INTENDED TO GAIN SITE CLOSE-OUT 19
6.4.1 DEVELOP AND EXIT STRATEGY 19
6.4.2 ADDRESS ONSITE SOIL CONTAMINATION 19
7.0 SUMMARY 20
List of Tables
Table 7-1. Cost summary table
List of Figures
Figure 1-1. Site layout showing the extent of contamination and locations of the monitoring, extraction, and
residential wells
Figure 4-1. Site layout showing the approximate locations of extraction wells in the proposed extraction
system
Figure 6-1. Model simulation from the original capture zone analysis suggesting capture of the plume in the
absence of recharge from the percolation ponds
Figure 6-2. Model simulation from the original capture zone analysis suggesting capture of the plume in the
presence of recharge from the percolation ponds
VI
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1.0 INTRODUCTION
1.1 PURPOSE
In the OSWER Directive No. 9200.0-33, Transmittal of Final FYOO - FY01 Superfund Reforms Strategy,
dated July 7,2000, the Office of Solid Waste and Emergency Response outlined a commitment to optimize
Fund-lead pump-and-treat systems. To fulfill this commitment, the US Environmental Protection Agency
(USEPA) Technology Innovation Office (TIO) and Office of Emergency and Remedial Response (OERR),
through a nationwide project, is assisting the ten EPA Regions in evaluating their Fund-lead operating
pump-and-treat systems. This nationwide project is a continuation of a demonstration project in which the
Fund-lead pump-and-treat systems in Regions 4 and 5 were screened and two sites from each of the two
Regions were evaluated. It is also part of a larger effort by TIO to provide USEPA Regions with various
means for optimization, including screening tools for identifying sites likely to benefit from optimization
and computer modeling optimization tools for pump and treat systems.
This nationwide project identifies all Fund-lead pump-and-treat systems in EPA Regions 1 through 3 and 6
through 10, collects and reports baseline cost and performance data, and evaluates up to two sites per
Region. The site evaluations are conducted by EPA-TIO contractors, GeoTrans, Inc. and the United States
Army Corps of Engineers (USAGE), using a process called a Remediation System Evaluation (RSE),
which was developed by USAGE. The RSE process is meant to evaluate performance and effectiveness (as
required under the NCP, i.e., and "five-year" review), identify cost savings through changes in operation
and technology, assure clear and realistic remediation goals and an exit strategy, and verify adequate
maintenance of Government owned equipment.
The Selma Pressure Treating Superfund Site was chosen based on initial screening of the pump-and-treat
systems managed by USEPA Region 9 as well as discussions with the EPA Remedal Project Manager for
the site and the Superfund Reform Initiative Project Liaison for that Region. This site has high operation
costs relative to the cost of an RSE and a long projected operating life. This report provides a brief
background on the site and current operations, a summary of the observations made during a site visit, and
recommendations for changes and additional studies. The cost impacts of the recommendations are also
discussed.
A report on the overall results from the RSEs conducted for this system and other Fund-lead P&T systems
throughout the nation will also be prepared and will identify lessons learned and typical costs savings.
1.2 TEAM COMPOSITION
The team conducting the RSE consisted of the following individuals:
Frank Bales, Chemical Engineer, USAGE, Kansas City District
Todd Hagemeyer, Hydrogeologist, GeoTrans, Inc.
Peter Rich, Civil and Environmental Engineer, GeoTrans, Inc.
Doug Sutton, Water Resources Engineer, GeoTrans, Inc.
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1.3
DOCUMENTS REVIEWED
Author
US EPA
US EPA
US EPA
US EPA
IT Corp.
IT Corp.
IT Corp.
IT Corp.
IT Corp.
Geomatrix Consultants, Inc
Geomatrix Consultants, Inc
IT Corp.
US EPA
IT Corp.
Date
September 1988
October 1993
April 1997
January 22, 1998
February 1999-July 2001
May 1999
January 1999
October 2000
March 2001
April 17, 2001
July 2001
August 2001
September 2001
October 2001
Title
Record of Decision
Record of Decision Explanation of
Significant Differences
Record of Decision Explaination of
Significant Differences
1-page excerpt from Request for Proposal
#116
Groundwater Monitoring Reports
Operations and Maintenance Manual
Remedial Action Design Drawings
Draft Final Report, Selma Pressure Treating
Superfund Site
Report for Monitor Well Sampling
Focused Feasibility Study Report, Final
Document, Selma Pressure Treating
Superfund Site
First Five Year Review
APCL Analytical Report
Memorandum for First Five Year Review
Monitoring Well Data
1.4
PERSONS CONTACTED
The following individuals were present for the site visit:
Wally Shaheen, Project Manager, U.S. Army Corps of Engineers, Rapid Response Program
Cleet Carlton, Project Geologist, IT Corp.
Mike Toepfer, Plant Operator, IT Corp.
Larry Hudson, Project Manager, IT Corp. Project Manager
Chris Sherman, Hazardous Substances Engineer, California Dept. of Toxic Substances Control
Tom Kremer, Remedial Project Manager, US EPA Region 9
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1.5 SITE LOCATION, HISTORY, AND CHARACTERISTICS
1.5.1 LOCATION
The Selma Pressure Treating site is located 15 miles south of Fresno, adjacent to the city limits of Selma,
California and addresses subsurface contamination from a former wood treating facility. The site occupies
approximately 40 acres, including the 14-acre former wood treating and storage facility and a 26-acre
neighboring vineyard. Zoned for heavy use, the site is located in a transition zone between agricultural,
residential, and industrial areas. A business named Upright Scaffolding and a small transmission repair
shop both border the site to the north and residences border the site to the east. Highway 99 cuts through
the center of the site as shown in Figure 1-1, residences lie to the east of the site, and vineyards and other
farm area border the site to the south and west.
1.5.2 POTENTIAL SOURCES
Wood treating operations began at the site in 1936. The treating process originally involved the use of
pentachlorophenol (PCP) and oil, but the associated treating facility was replaced by a pressure treating
facility that used chemicals including fluor-chromium-arsenate-phenol, chromated copper arsenate, PCP,
copper-8-quinolinolate, LST concentrate, Woodtox 140 RTU, and Heavy Oil Penta 5% solution. The
operating area and wood storage area were paved with asphalt in 1982; the asphalt remains in place.
Wood treating activities were suspended in 1994, and all structures from the site were removed with the
exception of the concrete drip pad and other concrete foundations in the stormwater runoff area. Drippings
from the former treatment processes have led to both soil and groundwater contamination beneath the
former facilities. The primary contaminant of concern is chromium, predominantly found as hexavalent
chromium, its more mobile state.
Remedial investigations of the contamination began in 1984, and by 1991 soil cleanup activities had
started. Approximately 13,000 cubic yards of soil were excavated, fixed, placed in an onsite impoundment
area, and capped. Additionally, further investigations led to excavation of an additional 5,000 cubic yards
of contaminated soil. This soil is currently stockpiled onsite under temporary cover for eventual disposal.
Approximately 21,000 cubic yards of soil, affected by the contaminants of concern at levels above cleanup
standards, remain at depths of up to five feet below ground surface. In addition, 30,000 cubic yards of soil
that exceeds cleanup standards have been estimated to lie as much as 25 feet below grade. Remedial
alternatives for these areas of concern are under consideration. Until these areas are remediated, they may
act as continuing sources of groundwater contamination.
1.5.3 HYDROGEOLOGIC SETTING
The site is located in the Central Valley of California, which is filled primarily with fluvial deposits. The
ground surface is approximately 300 feet above mean sea level (MSL) and is essentially flat. Sand, silt,
and clay in the form of discontinuous lenses result in significant heterogeneity at the site and preferential
pathways for the transport of contamination. The water table is approximately 30 feet below ground
surface (bgs) and is relatively flat. A gradient of 0.0015 feet per foot directs groundwater to the southwest.
As summarized in the October 2000 Draft Final Report, for modeling purposes, hydraulic conductivities at
the site were estimated to range from 1 foot per day (for areas with silt and clay) to 100 feet per day for
(areas with sand). The actual range, however, is likely much broader.
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Recharge to the site is estimated at approximately 10 inches per year of infiltration. Additional recharge is
also provided by the discharge of treated water to the onsite percolation ponds and by the infiltration of
stormwater from the neighboring Upright Scaffolding facility. Dudley Pond is the nearest surface water
body to the site, and it is located approximately 1.5 miles to the west.
1.5.4 DESCRIPTION OF GROUND WATER PLUME
The groundwater plume, as illustrated in Figure 1-1, stretches from the former wood treating area to
approximately 2,500 feet downgradient to the southwest and is approximately 1,000 feet wide. The plume
extends approximately 50 feet below the water table, but due geologic heterogeneity (preferential
pathways), the distribution is uneven. At approximately 1,600 feet downgradient from the source area, the
plume splits into two separate, but parallel plumes as if an area of low hydraulic conductivity exists
between them. Based on the July 2001 sampling event, the highest concentrations of chromium within the
plume were found in monitoring well R23-I (6280 ug/L total chromium and 6020 ug/L hexavalent
chromium).
In general, chromium concentrations in groundwater are highest near the former wood treating facility in
the areas around EW-1 (and EW-la), R23, and R23I. The highest chromium concentration in R23 (total
depth of 40 feet below ground surface) was observed during the first sampling event in February 1999.
Since then, the concentration has consistently decreased, despite the measured fluctuations in the water
table elevation. On the other hand, chromium concentrations in R23I (adjacent to, but beneath R23) have
increased.
Although soil contamination at depth could serve as a source of dissolved groundwater contamination due
to rising water levels, this cannot be easily confirmed with the present data because limited groundwater
data exists prior to February 1999 and limited soil data exists for chromium. Another, more likely,
scenario for transport of chromium from the soil to the groundwater is percolation of water from the
surface through the chromium-contaminated vadose zone to the saturated zone.
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2.0 SYSTEM DESCRIPTION
2.1
SYSTEM OVERVIEW
The original ROD signed in 1988 required that groundwater be extracted from 25 wells at 50 feet deep at a
cumulative rate of 1,040 gallons per minute (gpm); however, an Explanation of Significant Differences
(BSD) signed in 1993 reduced the required pumping to 250 gpm from 7 wells up to 70 feet deep with the
ability to expand the capacity of the plant. A second BSD signed in 1997 allowed discharge of the treated
effluent to percolation ponds to recharge water to the aquifer. The current system, which began operation
on September 29, 1998, meets the specifications of the 1993 and 1997 ESDs
2.2
EXTRACTION SYSTEM
The extraction system originally included 8 wells. However, one well (EW-3B) has been shut down due to
a low yield and very low contaminant concentrations. In addition, wells EW-1 and EW-2 (originally placed
to protect residential wells to the east) were replaced in February 2000 with EW-la and EW-2a, which are
both shallow wells positioned for improved recovery of contamination. Analysis by the site team suggest
that moving these extraction wells does not pose added risk to the residential wells originally protected by
them. The well locations (both the original wells and the new locations) are presented in Figure 1-1. The
pumping rates and screened intervals for all of extraction wells are provided in a table in Section 4.3.1 of
this report..
2.3
TREATMENT SYSTEM
The treatment system is located inside of a prefabricated building on a concrete pad and utilizes the
UNIPURE Process Technology. The process consists of an equalization tank, mixing tank/reactor, flash
mixer, clarifier, filter feed tank, multi-media filter, pH adjustment, and discharge to one of two recharge
basins. Solids from the clarifier are held in sludge thickening tanks and then run through a filter press.
The system operates at a rate of 220 gpm including both extracted water and water recycled through the
treatment system. The anticipated design influent (as listed in a 1-page excerpt from the 1998 request for
proposal) and the actual influent obtained from sampling in August 2001 are in the following table for
comparison. The data suggests that the influent concentrations for chromium are within the design criteria
but that the concentrations of some other constituents of the influent are not within the design criteria. The
system effluent has consistently met effluent discharge criteria.
Contaminant
Arsenic
Hexavalent Chromium
Total Chromium
Copper
Alkalinity as CaCO3
Design Influent Concentration
<10 ug/L
50-1, 100 ug/L
50-1, 100 ug/L
<50 ug/L
150-250 mg/L
Actual Influent Concentrations Aug. 2001
<5ug/L
406 ug/L
448 ug/L
24.1 ug/L
390 mg/L
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Contaminant
Chloride
Nitrate as Nitrogen
Sulfate as SO4
Phosphorous
Calcium
Iron
Magnesium
Manganese
Potassium
Sodium
pH
Total Suspended Solids
Total Dissolved Solids
Design Influent Concentration
45-60 mg/L
8-10 mg/L
60-90 mg/L
<0.3 mg/L
60-120 mg/L
<20 mg/L
10-40 mg/L
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3.1
3.0 SYSTEM OBJECTIVES, PERFORMANCE AND CLOSURE
CRITERIA
CURRENT SYSTEM OBJECTIVES AND CLOSURE CRITERIA
The current system is operating based on the 1988 ROD and two subsequent ESDs in 1993 and 1997. The
objective of the pump and treat system is to extract contaminated groundwater, treat it to MCLs and return
it to the aquifer via infiltration. Neither the ROD nor ESDs explicitly state whether the objective is to
restore the aquifer to MCLs or to contain the plume. As stated in the first Five-Year Review, an BSD is
required to clearly define the objective of the existing pump and treat system.
3.2
TREATMENT PLANT OPERATION GOALS
The effluent or discharge goals are stated in the ROD and ESDs. The following table includes the current
effluent discharge standards for some of the constituents of the extracted water.
Contaminant
Arsenic
Hexavalent Chromium
Total Chromium
pH
Total Suspended Solids
Total Dissolved Solids
Concentration
<50 ug/1
not detected
<50 mg/1
6.5-7.5
<20 mg/1
< 1,200 mg/1
* the "not detected" criteria for hexavalent chromium is self-imposed by the plant operators and is regularly
achieved given a detection level of 50 ug/L. The actual discharge criteria is more lenient.
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4.0 FINDINGS AND OBSERVATIONS FROM THE RSE SITE VISIT
4.1 FINDINGS
The RSE team found an extremely well maintained and functional facility. The system is not only well
maintained but is staffed by a conscientious and competent operator and team of managers. The
observations and recommendations given below are not intended to imply a deficiency in the work of the
designers, operators or site managers but are offered as constructive suggestions in the best interest of the
EPA and the public. These recommendations have the benefit of several years of operating data
unavailable to designers or site managers.
4.2 SUBSURFACE PERFORMANCE AND RESPONSE
4.2.1 WATER LEVELS
Although water levels are collected three times per year, they are not used to generate potentiometric
surface maps. Therefore, detailed analysis of these water levels is difficult within the scope of an RSE. In
general, water level measurements support the flow of groundwater to the southwest. There is little
evidence of a vertical gradient as measured by water levels in piezometer clusters, with the exception of
R24 and R24I, which indicate a downward gradient. However, this lack of evidence does not conclusively
show that groundwater and contamination do not travel vertically within the aquifer. Preferential pathways
may exist in areas (such as the area surrounding R24 and R24I) that transport groundwater and
contamination vertically. Mounding from infiltration from the percolation ponds is difficult to discern but
may be indicated by a relatively high water level in R22.
4.2.2 CAPTURE ZONES
Due to the high degree of heterogeneity at the site and the various influences on groundwater flow
(percolation ponds, extraction wells, residential wells, etc.) a capture zone analysis with water level
measurements alone would likely be inconclusive. Although there are a number of piezometers at the site
screened at various elevations, there may be an insufficient number to adequately resolve groundwater flow
for the purpose of analyzing a capture zone. Nevertheless, potentiometric surface maps based on the water
level measurements would likely be useful in understanding groundwater flow underlying the site during
various times of the year. For example, water levels and the potentiometric surface maps could provide
additional information as to the effects of recharge on groundwater flow. For a more thorough capture
zone analysis, groundwater flow modeling and particle tracking are likely necessary.
Capture zones at the site are not analyzed on a regular basis; however, a capture zone analysis was
conducted as part of the design of the extraction system and is included in the October 2000 Draft Final
Report. A 3-layer model generated with the parameters mentioned in section 1.5.3 of this report as well as
other information indicated capture of the plume by the seven extraction wells. Flow fields from the
groundwater flow model were used to track particles between the percolation ponds and the extraction
wells. Analysis by the model suggests that, despite recharging treated extracted water through the
percolation ponds, the plume is captured. In fact, the analysis suggests that flushing of the aquifer in the
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area of the plume is increased such that time to remediation could be accelerated because less water is
pulled from the surrounding cleaner portions of the aquifer. This may, in fact, be the case as
concentrations in EW-7 have decreased since installation and remained clean ever since, which suggests
that upgradient wells may have decreased or eliminated the transport of chromium toward that well.
However, the particle tracking analysis does not appear to track particles in the various model layers,
leaving open to question, the degree of capture vertically. Also, the model was only calibrated with one
round of water level measurements, the accuracy of the model and its predictions could be called into
question if variations in recharge and water levels are significant.
4.2.3
CONTAMINANT LEVELS
With a few exceptions near the source area, contaminant levels in piezometers across the site have
remained relatively constant with some fluctuation but no consistent increase or decrease. Three of the
exceptions are summarized in the following table.
Well
R23
R23I
R25
Depth to Bottom of Well
(feet below ground surface)
-40
-60
-40
February 1999 hexavalent
chromium concentration
(ug/L)
30,400
414
1,450
July 2001 hexavalent
chromium concentration
(ug/L)
1,780
6,020
180
As shown in Figure 1-1, R23 and R23I are adjacent to each other and are near former extraction well
EW-1 and current extraction well EW-la. Both extraction wells are screened between 45 and 60 feet below
ground surface. The decrease of chromium in R23 and R23I may result from pumping water from EW-1
or EW-la, treating it, and discharging the treated water through the percolation ponds. A possible
explanation follows:
In extracting groundwater, EW-1 and/or EW-la pull water from surrounding horizontal and vertical areas.
A capture zone analysis conducted as part of the system design (later discussed in Section 6.1.1.3 and
depicted in Figure 6-2) indicates that treated water from the percolation ponds was likely captured by EW-
1. Because EW-la is located closer to the ponds than the former EW-1, EW-la also likely captures treated
water from the percolation ponds. As this treated water migrates from the shallow zone below the
percolation ponds toward EW-1 or EW-la, it may serve to dilute the water sampled in R23, a relatively
shallow monitoring well. However, because R23I is deeper than R23, the treated water from the
percolation ponds may not reach it. Rather, contaminated water from other surrounding areas may pass
through R23I as it travels toward the extraction well resulting in an increase in chromium concentrations in
R23I.
Due to the proximity of EW-2 and EW-2a to R25, the decrease in concentrations in R25 may be attributed
to the extraction of groundwater from EW-2 prior to February 2000 and EW-2a after February 2000.
Contaminant levels in the influent (and each of the extraction wells) have remained relatively constant over
time (with the exception of a small increase due to the new locations of EW-1 and EW-2 to EW-la and
EW-2a). The influent concentration in August 2001 was 448 ug/L total chromium, which corresponds to a
chromium mass loading to the treatment plant of approximately 1 pound per day.
-------
4.3
COMPONENT PERFORMANCE
4.3.1
WELL PUMPS AND TRANSDUCERS
The maximum extraction rate for the system is currently around 200 gpm.. The flow through the plant is 220
gpm including all recycle streams. The well names, screened intervals, chromium concentrations, and flow
rates are provided in the following table.
Well
EW-la (new location)
EW-2a (new location)
EW-3A
EW-3B (shutdown)
EW-4
EW-5
EW-6
EW-7
Total
Screen Interval
(feet below surface)
45-60
35-45
45-100
105-125
60-95
121-136
47-87
55-85
Chromium
Concentration (ug/1)
2800
470
250
10
330
190
140
10
Flowrate (gpm)
25
20
35
0
50
25
25
14
194
The site managers are planning to possibly shutdown EW-7 and relocate some of the other extraction wells to
improve contaminant recovery. The proposed well relocations are depicted in Figure 4-1. Monitoring from
EW-7 will likely continue to confirm shutdown of the well is appropriate.
4.3.2
EQUALIZATION TANK
The equalization tank is designed to blend contaminated groundwater and recycle streams to produce a
homogeneous feed to the plant. Centrifugal pumps driven by variable speed drives maintain a selected setpoint
in the equalization tank.
4.3.3
REACTOR
Both pH adjustment and chemical oxidation-reduction reactions occur in this vessel. As part of the UNIPURE
Process Technology, chromium is reduced and iron is oxidized for later co-precipitation in the clarifier.
Ferrous Chloride is added to provide the necessary concentration of Fe+2 for the desired reaction. Sodium
hydroxide is then added to control pH and air is sparged to rapidly oxidize the iron to Fe+3 and reduce the
chromium from Cr+6 to Cr+3. The reaction vessel is well mixed via baffles and injection of air. The iron
precipitates out of the solution with the chromium. The chromium is occluded in the iron solids due to its close
association with the iron prior to its precipitation.
Chromium not removed by occlusion is removed by adsorption to the ferric iron solids. From the reactor, the
process water is transferred to the flash tank.
10
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4.3.4 FLASH Mix AND FLOCCULATION TANKS
The flash mix and flocculation tanks are located immediately prior to the clarifier. An anionic polymer is added
to the process water with a high speed mixer so that the iron solids produced in the reactor can be coagulated
in the flocculation tank. The flocculation tank allows a five minute retention time with a slow speed mixer to
form larger solids (floe) that settle more easily in the clarifier.
4.3.5 CLARIFIER
The clarifier contains lamella plates which enhance collection of the iron solids. The solids settle and fall to
the bottom of the clarifier. Air operated diaphragm pumps are utilized to both recycle the solids to the reactor
as well as transfer solids to the sludge holding tanks. The process water flows over the top of the clarifier weir
into the filter feed tank. The clarifier plates are cleaned once per month.
4.3.6 SOLIDS HOLDING TANK/FILTER PRESS
The sludge holding tanks are used to hold and thicken clarifier solids (approximately 4 cubic yards of
dewatered filter cake are generated per week) until they are processed through the filter press for dewatering.
These tanks have conical bottoms to allow easy removal of the solid contents. Solids from the filter press are
disposed of as a hazardous waste, due to F-032 and F-035 designations, despite easily passing TCLP testing.
Filter press filtrate and decant water from the sludge holding tanks are recycled to the equalization tank.
4.3.7 FILTER FEED TANK
The filter feed tank is used to hold clarified process water that will be treated via the multimedia filters to
remove remaining solids prior to discharge.
4.3.8 MULTIMEDIA FILTERS
The multimedia filters are backwashed whenever the pressure drop exceeds 18 psi or within 72 hours,
whichever occurs first. The standard operation has been to backwash two or three times per day for
approximately one and a half minutes each time. Backwash water is discharged to the sludge holding tanks.
4.3.9 EFFLUENT TANK (FINAL pH ADJUSTMENT)
The effluent tank contains a mixer and allows the addition of sulfuric acid for final pH adjustment. The tank
is emptied to the recharge basins via variable speed driven pumps. The effluent flow is measured and also
contains an inline, continuous hexavalent chromium analyzer, 1024 Analyzer from Scientific Instruments.
4.3.10 SYSTEM CONTROLS
The system has an autodialer and emergency stop switches for plant safety. The system operator is contacted
for any stoppage to operations which may occur for a number of reasons including alarms for power outages,
a high floor sump level, or a high chrome level in the effluent as determined by a continuous chrome analyzer.
The control system is currently not set to restart at the prior settings. The alarms sound infrequently, with
power outages the main reason for system shutdown.
11
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4.4 COMPONENTS OR PROCESSES THAT ACCOUNT FOR MAJORITY OF
MONTHLY COSTS
The following table provides average monthly costs associated with the routine operation and maintenance of
the Selma Pressure Treating site. The values were obtained by averaging the monthly expenses from three
months of operation within the past year.
Plant Operator $4,100
IT Project management and administration $2,500
Total Chemicals: $3,350
Polymer $550
Ferrous chloride $1,225
Caustic $1,000
Sulfuric acid $425
Chromium meter chemicals $150
Influent/Effluent Analysis $460
Groundwater Sampling/Analysis $2,000 ($8,000 per 4 months)
Utilities (electric and telephone) $3,600
Relocate Rolloff bins on site $850
Trans and dispose filter cake $1,050
Pickup rental and gasoline $1,000
Misc Repair Parts $1,000
Storage Container $75
O&M subtotal cost $19,985
IT fee, 7% $1,400
IT Subtotal Cost $21,385
USAGE fee, 11% $2,350
Average cost per month $23,735
4.4.1 UTILITIES
The current electrical usage is as expected. The electrical bills demonstrate an average monthly costs of
approximately $3,500 per month. There are no oversized motors or equipment onsite with the exception of the
effluent discharge pumps, which, if necessary, could be used to pump effluent to an alternate discharge point.
4.4.2 NON-UTILITY CONSUMABLES AND DISPOSAL COST
Disposal of generated sludge (approximately 4 cubic yards per week) costs about $ 1,000 per month on average.
The sludge passes all TCLP criteria; however, it is disposed as hazardous due to F-032 and F-035 designations
as wastes from a wood treating facility. The costs for chemicals used in the plant are reasonable considering
12
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plant operations. The system operator and engineer have reduced chemical consumption; however, to further
reduce chemical additions could lead to increased chromium concentrations in the effluent.
4.4.3 LABOR
The plant is maintained by a single full time operator, 40 hours per week. The site is also supported by a
project manager and geologist.
4.4.4 CHEMICAL ANALYSIS
The analyses performed for routine monitoring utilize a Hach kit for chromium, which has proven cost-effective
and accurate. Samples from the monitoring wells, the residential wells, and the influent and effluent are
analyzed offsite.
4.5 RECURRING PROBLEMS OR ISSUES
There have been no major recurring problems with operating the plant. During the RSE, a feed pump was
leaking and required repair. In an isolated incident, the treatment plant was burglarized. Items, including site
binders and reports, were stolen. A security system has since been installed at the plant.
4.6 REGULATORY COMPLIANCE
The system has maintain an efficient operation while attaining all discharge requirements.
4.7 TREATMENT PROCESS EXCURSIONS AND UPSETS, ACCIDENTAL
CONTAMINANT/REAGENT RELEASES
No process excursions and upsets were noted. The ferrous chloride tank emptied due to corrosion of fittings,
but the spilled liquid was contained by the berm. The corrosion has been addressed and no other leaks have
occurred.
4.8 SAFETY RECORD
No safety issues were identified.
13
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5.0 EFFECTIVENESS OF THE SYSTEM TO PROTECT HUMAN
HEALTH AND THE ENVIRONMENT
5.1 GROUND WATER
Residential and irrigation wells (irrigation wells are rarely used) are located down and cross gradient of the
plume and could become impacted if groundwater is not adequately contained. The capture zones have not
been analyzed since design of the original extraction system, and it is questionable if the original capture zone
adequately addressed vertical capture of the plume. In addition, recharge from the percolation ponds may
reduce the capacity of the extraction system to capture the plume. The closest municipal well is located
approximately 0.25 miles upgradient and is screened in a deeper aquifer than that impacted by site-related
contamination.
5.2 SURFACE WATER
Dudley Pond is the nearest surface water body to the site, and it is located approximately 1.5 miles to the west.
Impacts to this water body are not expected.
5.3 AIR
No air emissions are notable from this plant.
5.4 SOILS
A separate Record of Decision is currently being developed regarding site soils remaining. Contamination at
depth and at the surface remains. The remedy from this new ROD is anticipated to be implemented in fiscal
year 2003.
5.5 WETLANDS AND SEDIMENTS
No wetlands or sediments are at risk to site-related contamination.
14
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6.0 RECOMMENDATIONS
Cost estimates provided have levels of certainty comparable to those done for CERCLA Feasibility
Studies (-307+50%), and these cost estimates have been prepared in a manner consistent with EPA
540-R-00-002, A Guide to Developing and Documenting Cost Estimates During the Feasibility Study, July
2000.
6.1 RECOMMENDED STUDIES TO ENSURE EFFECTIVENESS
6.1.1 REGULARLY ANALYZE DATA AND CAPTURE ZONES AND REPORT RESULTS
The capture zone of the extraction system should be analyzed to confirm containment of site-related
contamination. Such an analysis should involve the following items:
an update of the plume boundaries,
analysis of the measured water levels and development of potentiometric surfaces, and
recalibration of and simulations with the site groundwater flow model.
Based on the results of the capture zone analysis, the extraction system and/or discharge system may require
modification to improve capture of the plume.
6.1.1.1 UPDATE CONTAMINANT PLUME MAPS AND ANALYZE TRENDS IN CONCENTRATIONS
The first step of conducting a capture zone analysis is to determine the portion of the plume targeted for
capture. In the case of the Selma site, it may be sufficient to capture all portions of the plume greater than the
MCL for chromium (50 ug/L). Groundwater sampling events that include sampling of approximately 40 wells
or piezometers are conducted every four months and provide updated information on the extent of the
contamination in the shallow, intermediate, and deep zones of the aquifer. Although site hydrogeologists are
working with this data, updated plume maps are not being generated. Rather, a generic plume map is
repeatedly used in the reports and no analysis is provided.
Updated plume maps should be generated for each sampling round so that trends in the plume shape can be
tracked overtime. Although natural fluctuations in the concentrations may result in a plume shape that differs
for each event, a noticeable trend may become apparent. Such a trend may indicate shrinking of the plume or
migration in one direction or another. Once accurate plume maps have been developed, the target capture zone
(perhaps the 50 ug/L contours) can be determined. This target capture would then serve as the basis for
capture zone analyses conducted with water levels and groundwater flow modeling.
On an annual basis, trend analyses of the concentrations in the sampled wells and the plume maps should be
conducted. These analyses will help site managers determine the effectiveness of the remedy and the likelihood
of achieving the objectives. A description of these analyses along with the historical data should be included
in one of the groundwater sampling reports each year.
15
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Creating plume maps based on historical sampling events (approximately 10 events) and analyzing trends in
chromium concentration over time should cost approximately $7,000 given that a base map already exists and
historical data is readily available in a spreadsheet. An additional $3,000 may be required for reporting the
historical data, plume maps, and trend analysis in the next groundwater sampling report. To provide site
managers with updated information in the future, plume maps should be generated for each sampling event and
provided in the associated report, and trend analyses should be conducted on an annual basis and included in
one of the regular groundwater sampling reports along with the historical groundwater quality data for the site.
These tasks may require an additional $3,000 per year.
6.1.1.2 ANALYZE WATER LEVEL MEASUREMENTS AND DEVELOP POTENTIOMETRIC SURFACE
MAPS
Water level measurements provide direct information regarding groundwater flow and are indispensable for
understanding groundwater flow at a site. Water levels at the Selma site are currently collected every four
months; however, analyses of these measurements and development of potentiometric surface maps are not
evident from reviewing the sampling reports. Water levels measured throughout the history of system operation
should be processed, analyzed, and used to develop potentiometric surfaces. Variations in pumping or recharge
should be reflected in the potentiometric surfaces and should give site hydrogeologists additional insight into
groundwater flow at the site.
These potentiometric surfaces can also be used for a preliminary capture zone analysis. General groundwater
flow directions throughout the site can be determined from the interpreted hydraulic gradient, and flow paths
that are directed into extraction wells will help interpret the capture zone. Then, once updated plume maps and
target capture zones are obtained for the historical chromium concentrations, site hydrogeologists can overlay
the interpreted capture zones with the target capture zones to determine the degree of capture. However, as
stated in Section 4.2.2 of this report, the number of piezometers at the site may not provide adequate resolution
of the flow field for capture zone analyses without the aid of a groundwater flow model. Thus, these water
levels and potentiometric surfaces should also be used to calibrate and update the groundwater flow model.
The model, in turn, would be used to estimate the degree of capture based on principles of groundwater flow
and the available data (please refer to Section 6.1.1.3 for more information on this step.)
A capture zone analysis should be conducted and reported on a regular basis, perhaps for each sampling event
until the variation capture is better understood. In addition, on an annual basis, hydrogeological data for the
site should be updated, analyzed, and included in one of the groundwater sampling reports, preferably the same
report that would include the analyses of groundwater concentrations recommended in Section 6.1.1.1.
Organizing the data, producing the potentiometric surface maps for the historical data, and analyzing the data
will likely require approximately $7,000 (costs of modeling are provided in Section 6.1.13). An additional
$3,000 may be required to include the data and the analyses in the next groundwater sampling report.
Conducting similar tasks on a regular basis with newly collected data may require an additional $4,000 per
year.
6.1.1.3 RECALIBRATE THE GROUNDWATER FLOW MODEL AND USE SIMULATIONS FOR
CAPTURE ZONE ANALYSES
The site managers already have a groundwater flow model that was used for a capture zone analysis prior to
installation of the original extraction system. This model provides an excellent framework for further capture
zone analyses and for simulations to aid in site management decisions. However, the model should be
recalibrated with water level measurements taken over the history of system operation to improve the accuracy
16
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and reliability of the model. An accurate model should be able to reproduce the water levels obtained from
measurements for a variety of pumping and recharge scenarios at the site, including pumping from the old and
new locations of EW-1 and EW-2 and pumping during different seasons. The model used by the site managers
reportedly reproduced, with reasonable accuracy, the water levels from the December 1997 sampling event.
Now that additional rounds of water levels have been collected, the existing model can be made more robust.
Once accurate flow fields are obtained, particle tracking can be conducted to ensure that particles from the
contaminated cells in the model domain (as determined from updated plume maps) are captured by the
extraction system. It is importantto note that reverse particle tracking, as was done in the original capture zone
analysis will not give a thorough evaluation of capture in a heterogeneous, three-dimensional model. The
reverse particle tracking method only employed the release of 8 particles per well at a single elevation and
tracked them backward to outline the capture zone. A more thorough analysis would involve the release of
particles from each cell in each layer that coincides with the target capture zone. Furthermore, the release of
particles from various elevations within a cell should be tested because the vertical component of flow at this
particular site could be significant, especially with pumping from different elevations. Particles should also
be color coded based on which wells capture them to better identify the capture zones of each well.
On a more general note, a capture zone analysis should demonstrate that water flow through the impacted area
is captured by the extraction wells. According to the particle tracking from the existing model shown in Figure
6-1, particles in the background flow field (upgradient of the extraction wells) traveled at approximately 200
to 300 feet per year. Removing the effect of porosity, this translates to a Darcy velocity of approximately 100
feet per year. The model domain is 3,000 feet wide, and it appears from Figure 6-1 that the extraction system
capture zone is also approximately 3,000 feet wide. The thickness of the three layers varied across the domain,
but on average, it appears that a saturated thickness of 100 feet is fairly representative. Assuming that half
of the formation has a significantly lower hydraulic conductivity than the other portions, the majority of
groundwater flow of 200 to 300 feet per year may be occurring only through effectively half of the cross-
sectional area of the model domain and flow through other portions may be significantly less. Following this
assumption about the formation, the above Darcy velocity should be reduced by half from 100 feet per year
to 50 feet per year. Thus, groundwater flow into the model domain and to be captured by the extraction system
is approximately
50ft 7.48 gal. 1 year 1 day
3,000 ft x 100 ftx x -fx y x = 213 gpm
year ft3 365 days 1440mm. 5F
This simple calculation, although based on crude estimates, suggests that the extraction system extracts
approximately the same amount of groundwater as is flowing from upgradient. If the recharge provided by
the percolation ponds is included, then the width of the capture zone decreases, which is consistent with another
model simulation (depicted in Figure 6-2) conducted as part of the original capture zone analysis. The degree
to which the capture zone narrows, however, will be dependent on the amount of recharge provided by the
percolation ponds or by natural recharge. The amount of recharge from the ponds likely varies with the seasons
because more water in the ponds will evaporate in the summer than in the winter, and the amount of natural
recharge will also vary based on the seasons potential increases may occur in the winter with the rainy season
or in the summer during irrigation. The recharge rate through the percolation ponds that was used in the
original capture zone analysis should be reviewed and the model should be used to determine how sensitive
capture is to that recharge rate. In addition, estimates of the amount of recharge should be obtained. This
could, perhaps, be accomplished by taking the discharge rate from the treatment plant and accounting for
potential evaporation. If the potential evaporation is not known, then it could be measured through simple
studies with evaporation pans.
17
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If the estimated recharge rate (either natural or through the ponds) exceeds the rate that can be captured as
determined by the model, then efforts may be required to reduce the amount of water being recharged. This
could be addressed by increasing evaporation of the discharged water through spraying, discharging treated
water to both ponds at the same time, or otherwise increasing the areal extent of the ponds.
Recalibrating the model based on historical water sampling events will likely cost approximately $5,000.
Conducting particle tracking simulations and associated capture zone analyses for various pumping and
recharge scenarios will likely cost an additional $5,000. The cost of estimating the evaporation potential and
the amount of water recharging to the aquifer from the percolation ponds should be negligible and included in
the above costs.
6.1.2 USE MODEL SIMULATIONS TO OPTIMIZE LOCATIONS FOR NEW EXTRACTION WELLS
The site managers are considering relocating some of the extraction wells to improve capture and
simultaneously increase contaminant recovery rates. The proposed relocations are noted in Figure 4-1.
Although these locations make sense conceptually, verifying these proposed locations and screening intervals
with the model would be beneficial.
Once the extraction wells are installed and a new pumping regime is established, water levels should be
measured, interpreted, and used to improve the model calibration. An accurate model would be able to
adequately reproduce the measured water levels for the two previous pumping scenarios (EW-1 and EW-2
original locations) and this new pumping scenario.
Running simulations to determine the optimal locations and screening intervals, in addition to recalibrating the
model to include the new pumping would cost approximately $4,000.
6.1.3 DEVELOP A CONTINGENCY PLAN FOR EXCEEDENCES INLOCAL GROUNDWATER WELLS
A contingency plan should be developed that outlines a course of action to be taken if local irrigation or
residential wells show an exceedence in site related compounds. This plan may include providing bottled water
and/or could involve adjusting the pumping rates of the various extraction wells to improve capture and
contaminant recovery in the area of the exceedence. This contingency plan should take into account the site
managers' knowledge of the Selma area and should be documented. Development and documentation of a
contingency plan may cost $5,000. However, costs to implement the plan, if necessary, would be higher and
dependent on the extent of contamination and the availability of alternative resources.
6.2 RECOMMENDED CHANGES TO REDUCE COSTS
6.2.1 DISPOSE OF SLUDGE AS NON-HAZARDOUS WASTE
The sludge generated by the treatment plant is currently listed as hazardous waste based on F-032 and F-035
designations, which are consistent with waste generated from wood treating facilities. However, the current
facility is a groundwater treatment system and is not a wood treating facility. Therefore, the waste designation
should be changed. The sludge passes TCLP testing indicating it will not act as a source of groundwater
contamination; therefore, the waste should be disposed of as non-hazardous. Current waste transfer and
disposal costs are approximately $12,600 per year. This cost would likely be reduced by half if this
recommendation is implemented.
18
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6.3 MODIFICATIONS INTENDED FOR TECHNICAL IMPROVEMENT
6.3.1 REPAIR LEAKS IN THE PLANT
A leak from a transfer pump was noted during the RSE site visit. The leak was contained and not alarming;
however, the repair should be performed.
6.4 MODIFICATIONS INTENDED TO GAIN SITE CLOSE-OUT
6.4.1 DEVELOP AND EXIT STRATEGY
The ROD states groundwater cleanup as the site objective with cleanup levels set at the more stringent of
federal and state MCLs. Developing an exit strategy based on this objective will provide a framework for
making future decisions at the site, including determining when cleanup is reached and the system can be shut
down. The site managers have already reached a point where an exit strategy would be useful. EW-7 has had
chromium concentrations below the cleanup level since operation began, and site managers are deciding
whether or not to shutdown or relocate the well. An exit strategy that specified, for example, four or eight
quarters of chromium concentrations below cleanup levels, would have given site managers criteria to help
them decide the appropriateness of shutting down or relocating the well. An exit strategy that provides a clear
framework for shutting down individual wells or the system as a whole should be developed. In addition, this
strategy should also include other steps necessary for achieving site closure, such as addressing the soil
contamination.
6.4.2 ADDRESS ONSITE SOIL CONTAMINATION
Previous investigations of soil contamination as summarized in the April 2001 Focused Feasibility Study
focused primarily on pentachlorophenol (PCP), arsenic, and dioxin/furans as the contaminants of concern.
PCP contamination as high as 92 mg/kg was found as deep as 25 feet in one 80 foot by 80 foot area of the site,
but soil contamination, in general, was predominantly located near the surface.
Despite soil contamination with these constituents, the only contaminant of concern detected above cleanup
levels in groundwater has been chromium. Limited data are available in the ROD for chromium contamination
of the soil with concentrations exceeding 800 mg/kg near the surface. The highest chromium concentration
detected beneath the surface was 31 mg/kg at a depth of 1 to 2.5 feet.
Soil contamination, particularly near the surface should be addressed to reduce exposure. Historical data
indicates that soil has not acted as a continuing source of groundwater contamination of PCP, arsenic, or
dioxin/furan. The soil should be more thoroughly investigated for chromium contamination to determine if it
is acting as a continuing source of chromium contamination of the groundwater and a remedy should be
designed accordingly. No cost is provided for this recommendation as site managers have already begun
considering alternatives.
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7.0 SUMMARY
In general, the RSE team found a well-operated and cost-effective pump and treat system. In addition,
decreasing chromium concentrations in two monitoring wells the highly impacted zone of the aquifer suggest
that the pump and treat system is having a positive impact on reducing the maximum concentrations measured
when system operation began.
The observations and recommendations mentioned are not intended to imply a deficiency in the work of either
the designers or operators but are offered as constructive suggestions in the best interest of the EPA and the
public. These recommendations have the obvious benefit of the operational data unavailable to the original
designers.
Several recommendations are made to enhance system effectiveness that predominantly focus on the analyzing
the capture zone of the extraction system. The only recommendation to reduce cost includes delisting the
sludge generated from the treatment system and disposing of it as non-hazardous waste. The only
recommendation for technical improvement involves fixing a leaking pump. Finally, the recommendations
regarding site closure include developing an exit strategy and addressing remaining soil contamination.
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Table 7-1. Cost Summary Table
Recommendation
6.1.1 Analyze Capture Zones
for Current Extraction System
6.1.1.1 Update contaminant
plume maps and analyze
trends in concentrations
6.1.1.2 Analyze level
measurements and develop
potentiometric surface maps
6.1.1.3 Recalibrate the
groundwater flow model
and use simulations for
capture zone analyses
6.1.2 Use model simulations to
optimize locations for new
extraction wells
6.1.3 Develop a contingency
plan for exceedences in local
groundwater wells
6.2. 1 Dispose of sludge as non-
hazardous
6.3. 1 Repair leaks in the plant
6.4.1 Develop an exit strategy
for the site
6.4.2 Address remaining soil
contamination
Reason
Effectiveness
Effectiveness
Effectiveness
Reduce Cost
Technical
Improvement
Gain Closeout
Gain Closeout
Additional
Capital
Costs
($)
$10,000
$10,000
$10,000
$4,000
$5,000
$0
$200
Not
Quantified
Not
Quantified
Estimated
Change in
Annual
Costs
($/yr)
$3,000
$4,000
$0
$0
$0
($6,300)
$0
Not
Quantified
Not
Quantified
Estimated Change
In Lifecycle Costs
($)*
$58,400
$74,600
$10,000
$4,000
$5,000
($101,700)
$200
Not
Quantified
Not
Quantified
Costs in parentheses imply cost reductions.
* assumes 30 years of operation with a discount rate of 0% (i.e., no discounting)
** assumes 30 years of operation with a discount rate of 5% and no discounting in the first year
21
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FIGURES
-------
FIGURE 1-1. SITE LAYOUT SHOWING THE MONITORING, EXTRACTION, AND RESIDENTIAL WELLS AND THE EXTENT OF CONTAMINATION IN THE
SHALLOW, INTERMEDIATE, AND DEEP ZONES
.RW-66
R23I
! ;
| \
|
PERCOLATION
PONDS
"\.
' \
' "x.
' X
LEGEND
MONITORING WELL
RESIDENTIAL WELL
EXTRACTION WELL
EXTRACTION WELL NO LONGER USED
AREA OF REMAINING SOIL CONTAMINATION
AND PROPOSED CAP
_ _ 50 ug/L CHROMIUM
ZONE
50 ug/L CHROMIUM
ZONE
_ _ 50 ug/L CHROMIUM
ZONE
THE SHALLOW
THE INTERMEDIATE
THE DEEP
RESIDENTIAL
AREA
0 600
SCALE IN FEET
1200
(Note: This figure is based on plume maps provided by IT site hydrogeologist and Figure 4-1 from the Selma Pressure Treating Site, Report for Monitoring Well
Sampling, July 2001, IT.)
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FIGURE 4-1. SITE LAYOUT SHOWING THE APPROXIMATE LOCATIONS OF EXTRACTION WELLS IN THE PROPOSED EXTRACTION SYSTEM.
.RW-66
CURRENT EW-1A
EW-1D
R23I'
JR23S
. V
! ;
| \
|
PERCOLATION
PONDS
"\.
' \
' "x.
' X
LEGEND
ฎ MONITORING WELL
A RESIDENTIAL WELL
PROPOSED EXTRACTION WELL LOCATION
V//\ AREA OE REMAINING SOIL CONTAMINATION
tzzZI AND PROPOSED CAP
50 ug/L CHROMIUM IN THE SHALLOW
ZONE
50 ug/L CHROMIUM IN THE INTERMEDIATE
ZONE
50 ug/L CHROMIUM IN THE DEEP
ZONE
RESIDENTIAL
AREA
0 600
SCALE IN FEET
1200
(Note: This figure is based on plume maps provided by IT site hydrogeologist and Figure 4-1 from the Selma Pressure Treating Site, Report for Monitoring Well
Sampling, July 2001, IT.)
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FIGURE 6-1. MODEL SIMULATION FROM THE ORIGINAL CAPTURE ZONE ANALYSIS SUGGESTING CAPTURE OF THE PLUME IN THE ABSENCE OF
RECHARGE FROM THE PERCOLATION PONDS
: -
..' " - ' :
,- '
.;
i . . . ,
<* i .' .
'&
m
:
7*
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FIGURE 6-2. MODEL SIMULATION FROM THE ORIGINAL CAPTURE ZONE ANALYSIS SUGGESTING CAPTURE OF THE PLUME IN THE PRESENCE
OF RECHARGE FROM THE PERCOLATION PONDS
I
I
-
(Note: This figure is Figure 4.4.4-2 from the Draft Final Report, IT Corp., October 2000.)
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Solid Waste and
Emergency Response
(5102G)
542-R-02-008U
October 2002
vwwv.clu-in.org/rse
www.epa.gov/tio
U.S. EPA National Service Center
for Environmental Publications
P.O. Box 42419
Cincinnati, OH 45242-2419
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