EPA Re9'on 6 Announces Record of
Decision Amendment Proposed Plan
Environmental Protection f ^*
for Ground Water
North Cavalcade Street Superfund Site
Houston, Harris County, Texas July 2011
The U.S. Environmental Protection Agency (EPA) is issuing this Proposed Plan to recommend a change to the
ground water remedy selected in the 1988 Record of Decision (ROD) and, most recently, in the 2009 ROD
Amendment for the North Cavalcade Street Superfund Site ("Site"), located in Houston, Texas. This Proposed Plan
considers additional information developed since the 2009 ROD Amendment implemented the Remedial Action for
ground water (and soils). Whereas the two previous decision documents addressed, in particular, the ground water
source areas, this Proposed Plan addresses only the more mobile dissolved phase ground water ("ground water").
The following discussion considers the 1988 ROD, but primarily focuses on the changes to the current (2009 ROD
Amendment) remedy.
The North Cavalcade Street Superfund Site is a former wood treating site located in Houston, Texas, where shallow
ground water in two zones has been contaminated with dense non-aqueous phase liquids (DNAPL) and associated
dissolved phase contaminants. The primary source areas were addressed in the 1988 ROD and the 2009 ROD
Amendment when the remedies selected treatment for both the shallow sand and the interbedded clay/silt unit. The
1988 ROD selected a pump and treat remedy for the shallow sand and recovered over 8,000 gallons of creosote
product. The more recent 2009 Amendment selected In-Situ Stabilization (ISS) to solidify the two source areas in
place, but residual DNAPL and some isolated areas of free-phase DNAPL remain, along with the dissolved phase
contamination. Natural attenuation of the ground water contaminants and the lithologic characteristics of both
zones act to limit expansion of the dissolved contaminant plume. However, the EPA has concluded that it is
technically impracticable to restore the dissolved phase ground water because of the intermittent occurrence of
residual and free-phase DNAPL in the shallow aquifers. The ground water plume, associated with the interbedded
unit, will not be responsive to existing treatment technologies.
The EPA is issuing this Proposed Plan to recommend containment of the two ground water plumes associated with
the Site, as restoration goals will not be achievable throughout the dissolved phase ground water plumes. Further,
the Agency is recommending that ground water cleanup levels be waived for a designated area, referred to as the
Technical Impracticability (TI) Zone. The boundaries of the TI Zone include both onsite and offsite areas and
apply to both of the impacted shallow aquifers. Within the boundaries of the TI Zone, cleanup levels will be waived
for benzene, benzo(a)pyrene, and naphthalene.
The EPA Region 6, lead agency for the Site activities, with support from the Texas Commission on Environmental
Quality (TCEQ), is issuing this Proposed Plan to recommend the following alternate remedy for the North
Cavalcade Street Superfund Site:
Contain the contaminant plume through natural processes;
Waive the ground water cleanup levels within the Technical Impracticability (TI) Zone; Prevent exposure
to contaminated ground water above acceptable risk levels by implementing institutional controls to restrict
access to, or use of, contaminated water.
In addition, long-term monitoring will be continued to ensure that the plume is not expanding, and to verify areas of
increasing or decreasing contaminant concentrations within the TI Zone. If present, DNAPL will also be removed
in the impacted monitoring wells in the short-term.
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The EPA Region 6 office is the lead agency for the North Cavalcade Street Superfund Site, and is issuing the
Proposed Plan with support from the Texas Commission on Environmental Quality (TCEQ). TCEQ conducted the
ground water investigation in January 2004 to define the extent of deeper ground water contamination in the
interbedded unit, as well as provided technical support and review of the actions implemented by the 2009 ROD
Amendment. The EPA developed the alternate ground water remedy and proposed action in consult with TCEQ
and will request concurrence by the State of Texas after considering all information submitted during the 30-day
public comment period.
The proposal and selection of a remedy as an amendment to the 1988 ROD and the 2009 ROD Amendment is in
accordance with the National Oil and Hazardous Substance Contingency Plan (NCP) §300.435(c)(2)(ii)(A) through
(H). The actions proposed in this Plan are a continuation of those previous actions taken for the Site in accordance
with the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA or Superfund), 42
U.S.C. §9617(a) and 40 CFR Part 300. Issuance of the Plan will adhere to the public participation and
documentation procedures specified in NCP §300.825(a)(2); and CERCLA §117(a).
Community Participation
This Proposed Plan discusses information developed since the previous 2009 ROD Amendment, including the
results of the December 2010 and April 2011 sampling events. However, those documents that were key to
selection of the ground water remedy in 2009 are included in the Administrative Record for this Proposed Plan [i.e.
Supplemental Investigation for Remedy Evaluation (2005); Focused Feasibility Study (FFS)(2008)], as the
information applies also to the dissolved phase ground water. The EPA encourages the public to review these
documents in order to gain a more comprehensive understanding of the North Cavalcade Site and the evaluation of
the proposed alternate remedy. The EPA also encourages the public to participate in the decision-making process
for the North Cavalcade Site by providing comments on all aspects of the Administrative Record File including
those documents which have been added to amend the record and support the decisions proposed in this Plan.
The amended Administrative Record file, which contains complete documentation of the analysis, will be available
for public review starting on Friday, July 8, 2011, at the following information repositories:
Houston Public Library
Houston Metropolitan Research Center
500 McKinney
Houston, Texas 77002
Hours:
Monday, Tuesday, Thursday, 10:00 am-6:00pm
Wednesday, 10:00 am - 8:00pm
Saturday, 10:00am to 5:00pm
Closed on Fridays and Sundays
Texas Commission on Environmental Quality
Building E, Records Management, First Floor
12100 Park 35 Circle
Austin, Texas 78753
(512)239-2920
Hours: Monday - Friday - 8:00 am to 5:00pm
The Record of Decision Amendment Proposed Plan summarizing the basis for the EPA's analysis of the alternate
ground water remedy will also be available for public review on EPA's public web page:
http://www.epa.gov/earthlr6/6sf/6sf-decisiondocs.htm.
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A public meeting to receive comments will be held at the Carnegie Regional Library, located at 1050 Quitman
Street, Houston, Texas, on Tuesday, July 19, 2011, from 4:00 PM to 5:30 PM. The public is invited to comment on
this Proposed Plan to amend the Record of Decision. Final decisions regarding the remediation of the North
Cavalcade Street Superfund Site will only be made after public comments are considered.
The official public comment period begins on July 8,2011, and ends on August 6,2011. During the public
comment period, written comments may be submitted to:
Camille Hueni
Remedial Project Manager
EPA, Region 6 (6SF-RA)
1445 Ross Ave.; Suite 1200
Dallas, Texas 75202-2733
(214) 665-2231 or toll free (800) 533-3508
Written comments must be postmarked no later than August 6,2011.
The EPA, in consultation with the State of Texas, will select a final remedy for the North Cavalcade Site after the
public comment has ended and information submitted during this time has been reviewed and considered. EPA
will respond to all comments received during the public comment period in the Responsiveness Summary, which
will be attached to the amended Record of Decision. Both the Responsiveness Summary and the ROD Amendment
will be available to the public at the two repository locations noted above. Note that the final site remedy may be
different from the proposed remedy identified in this Proposed Plan based on comments, new information, or issues
received during the public comment period. Such changes or alterations of this Proposed Plan will be explained
and described in the ROD Amendment. The ROD Amendment will be signed by the Regional Administrator for
the EPA Region 6.
Site Name, Location, and Description
The North Cavalcade Street Superfund Site is a 21-acre property and former wood treating site located in Houston,
Harris County, Texas, about one mile southwest of the intersection of Loop 610 and U.S. Highway 59 (Figure I1).
The Site is located within a commercial/industrial corridor, just north of the downtown Houston, with residential
areas to the west (200 feet downgradient) and to the northeast (Figure 2). The wood treating facility was
established in 1946 and continued in operation until 1961, at which time the property was foreclosed. The property
subsequently was subdivided and sold. The southern 10 acres of the Site are now privately owned and occupied by
two commercial businesses.
The ground water contaminant source areas and dissolved phase plumes are located on the southern 10-acre portion
of the property. The two source areas correspond to the former operation area and waste pits (approximately a one-
acre area). The contamination in the lower interbedded dissolved phase plume ("ground water") has an associated
offsite ground water component. Contamination in the shallow sand ground water is limited to onsite.
The 1988 ROD identified the contaminants of concern (COCs) for ground water and soils which included
polycyclic aromatic hydrocarbons (PAHs), such as naphthalene, and volatile organic compounds (benzene,
ethylbenzene, toluene, and xylene) associated with the creosote-based operations. Metals were infrequently
detected above background in soils (chromium, copper, lead, zinc) below a ten foot depth and non-detect from
surface to ten feet. Metals were not detected in ground water, with the exception of a single detection of arsenic.
The ground water contaminants considered in this Proposed Plan are naphthalene, benzene, and benzo(a)pyrene.
Figures are provided at the end of the Proposed Plan text
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Site History of Contamination and Selected Remedy
The EPA proposed the North Cavalcade Street Site to the National Priorities List (NPL) on October 5, 1984
(49 Federal Register [FR] 40320), and added the site to the final list on June 10, 1986 (51 FR 21054). The original
ROD for the North Cavalcade Street Superfund Site was issued on June 28, 1988, and implemented a remedy to
address both contaminated soil and ground water. The pump and treat remedy for ground water removed an
estimated 8,000 gallons of product (creosote source) from the first shallow sand water-bearing unit. Later
investigations verified that contamination was also located in the underlying interbedded unit, a much siltier zone
that was not conducive to the pump and treat remedy.
In September 2009, the U. S. EPA re-selected the remedy for both ground water and soil for the Site in a ROD
Amendment. The 2009 remedy simultaneously addressed further control/reduction for the shallow sand and
interbedded ground water source areas, through the use of ISS of creosote dense non-aqueous phase liquid
(DNAPL) ground water source areas in the shallow sand and interbedded unit. Stabilization of the two source areas
found in the shallow sand and interbedded unit in the southern part of the Site in effect controls the source and
restricts further leaching of contaminants into the dissolved phase ground water. The stabilization is conceptually
illustrated in Figure 3. The 2009 remedy also included the construction of a permanent cap over an existing soil
containment cell, located in the northern half of the site. The remedy addressed two different parts of the site; the
soil, as located, is not a driver for the ground water contamination. A pre-final inspection of construction
completion of the ISS (and permanent soil cover) was completed in February 2011.
The nature and extent of contamination at the North Cavalcade Street site has been assessed through onsite and
offsite sampling of various environmental media beginning with the Remedial Investigation (RI) in 1987 and
continuing to present. Additional investigations in 1998 and 2000 were conducted to clarify the understanding of
the geologic framework at the site, to determine the extent of DNAPL contamination and remaining volumes, and
to support the improvement of the treatment system for further evaluation of the remedy.
In January 2004, the EPA and TCEQ completed additional fieldwork to further delineate the source area and
dissolved ground water plume for both the shallow sand and interbedded unit. Based on the information obtained in
this sampling effort, a Supplemental Investigation for Remedy Evaluation Report was completed in June 2005. As
the site transitioned into remedial design and remedial action to implement the revised remedy described by the
2009 ROD Amendment, temporary monitoring wells, installed and sampled as part of the 2004 fieldwork, were
replaced with permanent wells (in December 2010) suitable for use in long-term monitoring. The EPA also
performed additional subsurface investigations to verify previous conclusions about subsurface conditions. These
activities are described in two documents: (1) Technical Memorandum: Summary of Activities and Results, North
Cavalcade Street Remedial Design Data Collection, January 2011 (CH2M HILL, 201 la), and (2) Technical
Memorandum: Summary of Activities and Results, Ground Water Data Collection August 2010 through April 2011,
North Cavalcade Street Superfund Site Remedial Action (CH2M HILL, 201 Ib).
Lithology
The North Cavalcade Street Superfund Site is located in the Southeast Texas Coastal Plain. This region is
underlain with Holocene and Pleistocene deposits to a depth of approximately 2,400 feet. The Pecore Fault, a local
surficial fault, runs along the southern boundary of the site. Two cross-sections are provided to illustrate the
shallow geologic conditions that are relevant to remediation at the site (Figures 4 through 6).
The geology at the site generally consists of interbedded clays, silts, and sands of fluvial-deltaic in origin. The
lithology onsite consists of a well-developed fine-grained sand in the shallow sand and a thinner interbedded unit,
dominated by clays and silts. The shallow sand is encountered at a depth of approximately 10 to 15 feet below
ground surface (bgs) and is of consistent thickness (8-15 feet) across the site. The shallow sand is also thinner on
the south side of the Pecore fault. The shallow sand is underlain by a predominantly clay layer, approximately 5
feet thick. The interbedded unit lies beneath this clay layer, at a depth between 24 and 27 feet bgs; the base of the
interbedded unit generally occurs between 30 and 34 ft bgs. The interbedded unit is quite variable in composition
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and thickness, consisting of thin interbedded clay, silty clay/clayey silt, silt, and clayey sand, which thins
significantly west of the Site boundary. A contour map of the top of the regional clay that occurs below the
interbedded unit is illustrated in Figure 7, and the variable effective thickness of the interbedded unit is illustrated
in Figures 8 and 9.
Hydrogeology
The primary shallow water-bearing units at the site are the shallow sand and the underlying interbedded unit. Both
water-bearing zones are hydraulically connected in the eastern and northeastern sections of the southern half of the
site, but separate into two distinct zones downgradient to the west. Towards the west side of the site, the permeable
portion of the shallow sand becomes siltier; and the permeable part of the interbedded unit becomes thin and
eventually completely transitions to a clayey silt, 3 feet thick, that limits continued ground water flow to the west.
Both water-bearing zones are underlain by a thick regional clay, approximately 100 feet thick, which serves as a
barrier to downward ground water flow and the vertical migration of contaminants. The Pecore Fault, a local
feature, runs along the southern boundary of the site and may limit lateral ground water flow to the south, although
it can only be considered a partially sealing fault. The fault, however, is not expected to impact the implementation
or effectiveness of the proposed alternate remedy.
The potentiometric surface data from 2004 through 2010 consistently indicates ground water flow direction is to
the west for both the shallow sand and the interbedded. Although the ground water flow gradient is relatively flat
across the onsite and offsite areas, the potentiometric surface gradients for both units steepen to the west (offsite),
suggesting subsurface changes which may impede ground water flow to the west.
Nature and Extent of COCs
The degree and extent of benzene and naphthalene contaminated ground water are shown in Figures 10 through
13, based on post-stabilization data collected from the permanent monitoring network in December 2010. Contour
lines on these maps are based on the December dataset, as it is the most complete across the site. These figures also
include data, if collected, in 2009 and April 2011. Benzene and naphthalene are the most mobile of the Chemicals
of Concern (COCs) and define the western extent of contamination for the interbedded unit and the Site.
Benzo(a)pyrene, the third COC for the Site is non-detect for the shallow sand and detected at only two locations
(one onsite; one offsite) in the interbedded unit (Figures 14 and 15). Subsurface contamination at the Site is
present in the dissolved phase and residual DNAPL phase for the shallow sand and interbedded unit. There is
limited free-phase DNAPL in the interbedded unit.
The Remedial Action Objectives (RAOs), implemented under the 2009 ROD Amendment for ground water,
included preventing current and future use of shallow sand and interbedded unit ground water at concentrations
exceeding the Site cleanup levels. The cleanup levels were defined as 5 micrograms per liter (|ig/l) or parts per
billion (ppb) for benzene, 0.2 micrograms per liter (|ig/l) or ppb for benzo(a)pyrene, 1500 (ig/1 or ppb for
naphthalene onsite, and 490 (ig/1 or ppb for naphthalene offsite (EPA, 2009). Since benzene and naphthalene
concentrations are the drivers for remediation and the only COCs detected offsite, this discussion focuses on
benzene and naphthalene as the primary COCs.
The dissolved phase plume in the shallow sand, as indicated by COC concentrations greater than the detection
limits (defined by the non-detect, or ND, line on the figures), extends from the two source areas towards the west-
southwest with the direction of ground water flow. The majority of the shallow sand dissolved plume, at
concentrations greater than the cleanup levels, is located within the boundary of the site. Concentrations of
benzene in the shallow sand have not migrated offsite at concentrations greater than the cleanup up level of 5 (ig/1
except at one isolated new monitoring well location (MW-43S) where benzene was detected at 6.9 (ig/L (December
2010 result). This well was not sampled in the April 2011 sampling event. The isolation of this well from the
dissolved plume onsite is clearly demarked by a row of several wells with no concentrations above the cleanup
level. Similarly, the concentrations of naphthalene in the shallow sand have not migrated offsite at concentrations
greater than the cleanup level of 490 (ig/1.
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The dissolved phase plume in the interbedded unit is more extensive than in the shallow sand, as indicated by COC
concentrations greater than the cleanup level and extent of the plume, defined by the ND line on the figures. The
contaminant plume has migrated past the western boundary of the Site. The downgradient extent of benzene in the
interbedded zone, above the cleanup level, resides between Elysian Street and Hardy Street and does not appear to
cross the Pecore Fault along Cavalcade Street. Similarly, the downgradient extent of naphthalene, in excess of the
offsite cleanup level, is between Hardy Street and Elysian Street, with concentrations along Elysian Street ranging
up to a maximum 2,000 (ig/1 in monitoring well MW-46I (April 2011), dropping off to less than 15 (ig/1 in the next
block (the next downgradient well with a detection is MW-50I along Hardy Street, where 5.7 (ig/1 was detected in
December 2010 and 14 (ig/1 in April 2011). At MW-52I, located one block further west, 9 (ig/1 of naphthalene was
detected in December 2010, but was not detected in April 2011. These figures also show the extent of residual-
phase DNAPL in the shallow sand and interbedded unit. Also shown are the two areas corresponding to the
immediate source areas, with the highest potential for DNAPL. These were the areas stabilized in 2010. The
maximum DNAPL thickness in the shallow sand and interbedded unit was estimated in 2004 at approximately 5
feet and 3 feet thick, respectively.
No DNAPL was observed during drilling or sampling of the new monitoring wells at the site in
November/December 2010. However, during preparation for a yield test at new well MW-42I on April 13, 2011,
DNAPL was observed on the dedicated tubing and water level meter. As a result, the test at MW-42I was cancelled
and all permanent site monitor wells were checked for the presence of DNAPL. Four wells installed in
November/December 2010 were found to contain a measurable quantity of DNAPL during April 2011. The
observation of DNAPL in MW-33I, MW-42I, MW-57I, and MW-59I was unexpected based on observations during
drilling and well construction. In addition, the surrounding temporary wells had never indicated DNAPL
accumulation since their installation in 2004. However, the locations of these wells are within or adjacent to the
2004-defined extent of residual DNAPL in the interbedded unit, as presented on Figures 11,13, and 15. As part of
the proposed alternate remedy, DNAPL accumulations will be measured and recovered on a regular basis and
volumes noted. Overall trends will continue to be monitored in accordance with the long-term monitoring plan.
Of note, the leading edges of the benzene and naphthalene plumes in the interbedded unit are confined to less than
300 feet from the downgradient edge of the observed extent of DNAPL. The stability of the dissolved phase plume
suggests that the DNAPL footprint, the presumed source of the benzene and naphthalene, is also stable. This trend
has been observed since 2004, when temporary wells into the interbedded unit were first sampled.
Contaminant Transport
Lithologic and structural controls limit the mobility of contaminants at the site. The lateral mobility of
contaminants at the site is impeded by the change in lithology from the upgradient source locations to the most
offsite (westerly) locations within both the shallow sand and the interbedded unit. The downward migration of
contaminants is impeded by the underlying regional clay. The Pecore Fault may control expansion of the
contaminants to the south, although it can only be considered a partially sealing fault. The fault, however, will not
impact the implementation or effectiveness of the selected ground water remedy. Furthermore, dissolved COCs in
the shallow sand do not appear to have migrated offsite and remain confined near the source areas. The
interbedded unit is the primary concern for offsite migration of contaminants, but migration within it is also limited.
Exposure Pathways
Ground water used to supply water for domestic, industrial, and agricultural purposes is pumped from the Lower
Chicot and Evangeline aquifers. Both of these aquifers are confined and isolated from surface recharge. Public
water supply wells are screened in the Evangeline aquifer at depths greater than 600 feet below ground surface.
The closest water well to the impacted portions of the Site is located to the northwest approximately one-quarter
mile. Water from this well is for industrial use and well is screened from 200 to 210 feet in the upper Chicot
aquifer. (CH2M HILL, 2008).
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The shallow sand and the interbedded unit are not being used for sources of drinking water onsite or within a one-
mile radius of the site. Although a deep onsite aquifer is potentially useable as a public water supply source, onsite
and neighboring residents are served by the City of Houston water supply which originates from a deeper aquifer
10 miles from the site, or a surface water reservoir located over 20 miles from the site. In addition, the Houston-
Galveston Coastal Subsidence District requires notification and permits for the drilling of new ground water wells,
discouraging the use of private wells in those areas adequately served by the City of Houston municipal water
supply system (CH2M HILL, 2008). As a result, it is unlikely that there would be any receptors in the future.
A search was conducted to identify all water wells within a one and two mile radius of the North Cavalcade Street
site. A technical memorandum presenting the results of the well search is included in the Focused Feasibility Study
(CH2M HILL, 2008). Results of the water well search confirmed that no shallow water wells are located within
one to two miles of the North Cavalcade Street site. The closest water well is located approximately one-quarter
mile to the northwest (i.e. cross-gradient) of the site. Water from this well, screened from 200 to 210 feet in the
upper Chicot aquifer, is used for industrial purposes (CH2M HILL, 2008).
Vapor intrusion has also been considered as a potential exposure pathway at the site. The dissolved phase plume in
the shallow sand extends beneath and/or adjacent to the commercial buildings located on the western portion of the
site. To evaluate the potential for vapor intrusion, a screening evaluation was performed using the Johnson and
Ettinger model (EPA, 2009). The results of the modeling indicate that the highest concentrations in ground water
close to building footprints do not exceed screening levels. The modeling did not take into account biodegradation
of naphthalene, which would reduce the impact of vapor intrusion. As a result of not including biodegradation, the
modeling results should be considered overly conservative. The results of the evaluation concluded that vapor
intrusion is unlikely to be a potential exposure pathway at the site (EPA, 2009).
Comparison of the Previous Remedies and Proposed Alternate Remedy
Remedial Action Objectives (RAOs) are developed to consider the contaminants of concern (COCs), exposure
route(s), receptor(s), applicable federal and state standards, and anticipated future land use for the Site. The RAOs
developed in the 1988 Feasibility Study for soil and ground water at the site required that existing contamination be
removed and/or treated to ensure that human health and the environment are protected. As a point of comparison,
the following RAOs for ground water were established in the original 1988 ROD and the 2009 ROD Amendment
as follows:
Ground Water RAO (1988 ROD)
Removal and/or treatment of ground water containing concentrations exceeding Maximum Contaminant Levels
(MCLs) established under the Federal Safe Drinking Water Act.
As part of the 2008 Focused Feasibility Study, the original RAOs were reviewed for applicability with conditions at
the Site and revised accordingly. The revised RAOs for the Site again met the overall remedial goals of the original
RAOs of ensuring that human health and the environment are protected for ground water, as follows:
Ground Water RAOs (2009 ROD Amendment)
Prevent or minimize source area migration and contribution to the existing dissolved phase plume [source
control].
Prevent or minimize the potential that ground water contaminants from the shallow sand and interbedded
unit could impact deeper aquifers [prevent or minimize further migration of the plume}.
Prevent current and future use of the shallow sand and interbedded unit ground water impacted by past
site operations with ground water contaminants in excess of the site cleanup goals: 5 ppb for benzene, 0.2
ppb for benzo(a)pyrene, 1500 ppb for naphthalene onsite, and 490 ppb for naphthalene offsite) [prevent
human exposure to contaminated ground water above acceptable risk levels}.
Return ground water to its expected beneficial use wherever practicable [restoration}.
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Both the 1988 ROD and the 2009 ROD Amendment implemented treatment to control the contaminant DNAPL
source and prevent or minimize further migration of the contaminated ground water derived from the source areas.
The 1988 pump and treat remedy was implemented for the shallow sand only. The 2009 ROD Amendment
modified the cleanup levels for three creosote-related contaminants to meet the Safe Drinking Water Act (SOWA)
Maximum Contaminant Levels (MCL), or State standard: benzene (5 (ig/L or 5 ppb); benzo(a)pyrene (0.2 (ig/L or
0.2 ppb); and naphthalene (State standard - 1500 (ig/L or 1500 ppb for onsite/commercial; 490 (ig/L or 490 ppb for
offsite/residential). [Both the 1988 ROD and the 2009 ROD Amendment addressed the operable units for the Site:
OU1/OU3 for ground water; OU2 for soils. This Proposed Plan includes the final action for the OU1/OU3
dissolved phase ground water.]
The 1988 and 2009 RAOs which will be modified by this Proposed Plan are:
Prevent human exposure to contaminated ground water above acceptable risk levels; and
Return ground water to its expected beneficial use wherever practicable (restoration).
The proposed alternate remedy will prevent human exposure to contaminated ground water above acceptable risk
though the implementation of institutional controls (i.e. prevent the installation of new water supply wells into
impacted ground water). Ground water restoration will be replaced by containment of the contaminated
groundwater through natural processes or conditions. A TI Zone will be established, within which existing cleanup
levels will be waived. Long-term monitoring will be continued to ensure that the plume is not expanding and to
determine contaminant trends inside the TI Zone boundary. If present, DNAPL will be removed from the affected
monitoring wells in the short-term.
In addition, EPA is required to conduct a Site review every five years (Five-Year Review) to ensure that the
remedy continues to be protective of human health and the environment in instances where hazardous substances,
pollutants, or contaminants are left in place at concentrations that prevent unlimited use and unrestricted exposure.
The next Five-Year Review for the North Cavalcade Street Superfund Site is planned for completion in September
2013.
The EPA uses nine criteria to evaluate remedial alternatives for the cleanup of a release. These nine criteria are
categorized into three groups: threshold, balancing, and modifying. The threshold criteria must be met in order for
an alternative to be eligible for selection. The threshold criteria are overall protection of human health and the
environment and compliance with Applicable, Relevant and Appropriate Requirements (ARARs). The balancing
criteria are used to weigh major tradeoffs among alternatives. The five balancing criteria are long-term
effectiveness and permanence; reduction of toxicity, mobility or volume through treatment; short-term
effectiveness; implementability; and cost. The modifying criteria are state acceptance and community acceptance,
which are evaluated once the Proposed Plan public comment period is complete.
The TI waiver of cleanup levels, combined with containment of the contaminant plumes, is the alternate remedy
that is being considered because other active technologies are impracticable under the current Site conditions and a
Monitored Natural Attenuation remedy is limited by the presence of DNAPL. Therefore the remedy comparison
will be between the Monitored Natural Attenuation remedy presented in the 2009 Proposed Plan and the alternate
remedy presented in this Proposed Plan. The components of the proposed alternate remedy are:
Establishment of a TI Zone, as applied to both the shallow sand and interbedded contaminant plumes;
Waiver of cleanup levels within the specified TI Zone;
Implementation of Institutional Controls to restrict use of, or access to, contaminated ground water;
Short-term removal of DNAPL in impacted monitoring wells.
Table 1 provides a comparative analysis of the 2009 ROD Amendment recommendation for the dissolved ground
water phase and the alternate remedy in this Proposed Plan, under the nine-part criteria. The 2009 decision
document selected additional monitoring to support that natural attenuation would restore the contaminant plumes
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after ISS of two DNAPL source areas. The alternate remedy recommends the containment of the contaminant
plumes and the waiver of ARAR-based cleanup levels within a designated Technical Impracticability Zone.
Table 1: Nine Criteria Comparative Analysis
North Cavalcade Street Superfund Site
Evaluation Criteria
2009 ROD Amendment
Ground Water Remedy
2011 Proposed Ground Water Alternate
Remedy
Overall Protection of
Human Health and the
Environment
The 2009 remedy would be more
protective than the alternate remedy
because the natural attenuation
processes were expected to restore
the ground water to drinking water
quality after the DNAPL source was
removed. The estimated timeframe
for naphthalene to reach cleanup
goals in the offsite area was 100 years
after solidification of the entire
DNAPL source. Institutional controls
would be placed to restrict use or
access until cleanup goals were met.
The alternate remedy provides adequate
protection because the risk from exposure
to contaminated ground water will be
controlled through containment of the
ground water plume from natural processes
and lithologic restrictions to plume
migration. Proposed water well drilling
restrictions and monitoring will prevent
exposure to contaminated ground water
through use or access.
Compliance with
Applicable or Relevant and
Appropriate Requirements
("ARAR").
The 2009 ROD Amendment revised
cleanup levels based on MCLs for
benzene and benzo(a)pyrene, and on
a State standard for naphthalene, as
restoration goals for the dissolved
phase ground water.
The alternate remedy will not meet the
ARARs for the MCLs for benzene and
benzo(a)pyrene, or the State standard for
naphthalene, across the dissolved phase
ground water associated with the Site.
There is no technology capable of further
significant reduction of the contaminated
ground water beyond the two treatment
remedies implemented and completed for
the for the DNAPL source areas. The
limited amounts of free-phase NAPL , and
to some extent the residual phase, will
continue to contribute to dissolved phase
ground water contamination, where
present. The heterogeneity and clays/silts
of the interbedded unit will limit the
effectiveness of additional treatment. For
this reason, the MCLs for benzene and
benzo(a)pyrene, and the State standard for
naphthalene, will be waived because it is
technically impractical to meet these
standards with yet, another round of
treatment.
Long-term Effectiveness
and Permanence
The remedy (source stabilization;
earlier pump and treatment of the
shallow sand) and natural attenuation
(if validated) was expected to
permanently achieve the cleanup
The natural attenuation process has been
demonstrated for naphthalene and benzene
in the interbedded unit and is a key
contributor to maintaining overall plume
stability. However, where DNAPL may
-------
Evaluation Criteria
2009 ROD Amendment
Ground Water Remedy
2011 Proposed Ground Water Alternate
Remedy
levels with time. Verification of
cleanup trends would be documented
through long-term monitoring. [The
permanent network was installed in
December 2010.]
still remain, sourcing of contaminants to
ground water is expected to dominate the
natural attenuation process. Although
attenuation of the three COCs will continue
to decrease concentrations for parts of the
dissolved phase plume, the complete
restoration of the plume is not anticipated.
The contaminated ground water will be
monitored to confirm that the
contamination is not increasing or
migrating out of the proposed TI zone.
Because waste will remain on the site
above health-based levels, a formal review
to assess the protectiveness of the remedy
will be done every five years.
Reduction of Toxicity,
Mobility, or Volume of
Contaminants through
Treatment
There was a source stabilization
component of the 2009 selected
ground water remedy, that was
applied to two source areas that
impacted both the shallow sand and
the interbedded unit. A previous
pump and treat remedy implemented
by the 1988 ROD also recovered over
8,000 gallons of creosote DNAPL
from the shallow sand. The 2009
remedy implemented monitoring to
demonstrate natural attenuation for
the remaining dissolved phase plume.
Natural attenuation, after the two
source control/removals, was
expected to restore ground water to
the applicable MCLs or State
standard over time, for both the
shallow sand and interbedded unit, if
proven.
The alternate remedy does not include
treatment. Two previous treatment
remedies were applied to address the
DNAPL source. Pump and treat was the
initial remedy for the shallow sand only,
where the ground water plume is limited to
onsite and remaining residual DNAPL is
close to the stabilized source area.
The 2009 ROD Amendment again
addressed the source area; this time, for
both the shallow sand and the interbedded
unit. The alternate remedy addresses the
remaining dissolved phase ground water
only. Natural attenuation has been
demonstrated for the more mobile plume
associated with the interbedded unit and is,
along with lithologic limits, is limited
further expansion of the plume.
Attenuation is also expected to decrease
concentration (volumes) in those areas of
the plume where the process is not
competing with dissolution of remaining
DNAPL.
No further treatment is being planned as
the complexity of the interbedded zone, in
particular, limits the effectiveness of
available technologies.
Short-term Effectiveness
The 2009 ROD Amendment
implemented additional source
treatment; long-term monitoring will
document effectiveness over time for
No construction is required and no impact
over the short-term is expected to the areas
surrounding the site.
10
-------
Evaluation Criteria
2009 ROD Amendment
Ground Water Remedy
2011 Proposed Ground Water Alternate
Remedy
the dissolved phase plume. Long-
term monitoring will also
demonstrate the effectiveness of
natural attenuation over time.
Construction of the remedy was
completed with no impact to existing
infrastructure or the community.
Long-term ground water monitoring will
document containment (no further
migration) over time for both the shallow
sand and interbedded unit.
Implementability
Implementation of the 2009 ground
water remedy was successful. Natural
attenuation was demonstrated as an
ongoing process.
Implementation of the same pump
and treat technology or further
stabilization technology is technically
impracticable for the remaining
residual or isolated DNAPL, or for
the dissolved phase ground water,
particularly for the interbedded unit.
Annual monitoring costs range from
$60,000-$150,000.
Implementation of the institutional controls
(ICs) related to deed notices or restrictive
covenants will depend on individual
property owner's response to the proposed
requests. ICs will be placed to provide
notice of the presence of ground water
contamination. ICs will include provisions
to restrict access to maintain protectiveness
of the remedy (i.e. prevent contact with
contaminated ground water) and to protect
the physical components of the
construction (stabilized areas; monitoring
wells). The TI Zone will be registered
with the Texas Department of Licensing
and Regulation (TDLR) for the purpose of
issuing an advisory to area water well
drillers.
Cost
Annual monitoring costs range from
$60,000 - $200,000 based on frequency of
sampling, wells sampled, and parameters
(There are 68 permanent wells in the
monitoring network.) In particular,
monitoring will document continued
containment of contaminants to the TI
Zone.
State/Support Agency
Acceptance
The State of Texas, through the
TCEQ, concurred on the remedy
The TCEQ supports the proposed alternate
remedy.
Community Acceptance
The remedy was accepted by the
community
Community acceptance will be evaluated
after the public comment period ends and
will be described in the ROD Amendment.
Justification for a Technical Impracticability Waiver
Section 121(d) of CERCLA, 42 U.S.C. § 962l(d), andNCP § 300.430(f)(l)(ii)(B) require that remedial actions at
CERCLA sites at least attain legally applicable or relevant and appropriate Federal and State requirements,
standards, criteria, and limitations which are collectively referred to as ARARs, unless such ARARs are waived
under CERCLA section 121(d)(4), 42 U.S.C. § 9621(d)(4).
The cleanup levels for the Site's ground water are the drinking water MCLs for benzene and benzo(a)pyrene. The
MCLs are considered federal Applicable or Relevant and Appropriate Requirements (ARARs) for cleanup of the
ground water at the Site. Superfund regulations require that all cleanups meet ARARs or justify a waiver of the
11
-------
ARAR. A ground water cleanup level for naphthalene was implemented in the 2009 ROD Amendment, based on
the Texas Risk Reduction Program promulgated standards for residential and commercial/industrial exposure
scenarios. Although, there is no federal MCL for naphthalene, the State standard (as a cleanup level), is also being
waived within the TI Zone, in this Proposed Plan.
Portions of the two contaminant plumes are still expected to decrease in size and concentration through an ongoing
degradation process, particularly where there is no significant residual creosote, or DNAPL, in ground water. If
DNAPL is present, it will however continue to act as continuing source of contamination to the more mobile
dissolved phase ground water, at a rate exceeding natural degradation (or attenuation). As previously noted,
treatment has already been completed for both source areas. The remaining residual and limited occurrences of
DNAPL will be difficult to remove in the interbedded unit, where materials will be bound in the clay and silts.
The proposed TI Zone defines an area where cleanup levels are waived for benzene, benzo(a)pyrene, and
naphthalene, in both the shallow sand and the interbedded unit. The area definition, however, is driven by the
extent of naphthalene and benzene in the interbedded unit. Each contaminant plume map (Figures 10 through 15)
shows the outline (in green) of the proposed TI Zone, where cleanup levels will be waived. The TI Zone is defined
by geographical boundaries and is the same for contaminant plumes associated with the shallow sand and the
interbedded unit. The boundary allows for some fluctuation of contaminant concentrations, which will be
monitored over time. The 2009 ROD Amendment cleanup levels are included as a frame of reference for each
plume map. Contaminant concentrations cannot exceed the risk-based cleanup levels outside the designated TI
Zone boundary.
The Technical Impracticability of Ground Water Restoration (CH2M HILL, 2011) Technical Memorandum
(available in the Administrative Record for this Proposed Plan) provides more discussion on why restoration is no
longer a feasible option for the Site's contaminated ground water and provides the basis for the proposed waiver
and establishment of a TI Zone.
Summary
In summary, the EPA is issuing this Proposed Plan to waive the current cleanup levels as further treatment of the
dissolved phase ground water is technically impracticable. EPA, however, will continue to remove DNAPL from
the four monitoring wells in the short-term and also continue monitoring to document trends within the TI Waiver
Zone, including those associated with natural attenuation, the previous in-situ source stabilization, and plume
stability.
Glossary
Administrative Record - The body of documents available to the public associated with characterization and
remedy selection at a site.
Applicable or Relevant and Appropriate Requirements (ARARs) - The Federal and State environmental laws
that a selected remedy will meet. These requirements may vary among sites and alternatives.
Comprehensive Environmental Response, Compensation and Liability Act (CERCLA) - Also known as
Superfund. CERCLA is a Federal law passed in 1980 and modified in 1986 by the Superfund Amendments and
Reauthorization Act. This law provided broad Federal authority to respond directly to releases or threatened
releases of hazardous substances that may endanger public health or the environment. Under CERCLA, the EPA
can either pay for the site cleanup or take legal action to force parties responsible for site contamination to clean up
the site or pay back the Federal government for the cost of the cleanup.
Contaminant Plume - A column of contamination with measurable horizontal and vertical dimensions that is
suspended in and moves with ground water.
12
-------
Dense Non-aqueous Phase Liquids (DNAPL) - A DNAPL is an organic substance that is relatively insoluble in
water and denser than water. DNAPLs tend to sink vertically through sand and gravel aquifers to the underlying
layer.
Feasibility Study (FS) - Identifies and evaluates the appropriate technical approaches and treatment technologies
to address contamination at a site. The 2008 Focused Feasibility Study for the North Cavalcade Site evaluated the
proposed changes to the soil and ground water remedy selected in the 2009 Record of Decision Amendment.
Ground Water - Underground water that fills pores in soils or openings in rocks to the point of saturation.
Ground water is often used as a source of drinking water via municipal or domestic wells.
Ground Water Monitoring - Ongoing collection of ground water information about the environment that helps
gauge the effectiveness of a cleanup action.
Human Health Risk Assessment - A study that determines and evaluates risk that site contamination poses to
human health.
Institutional Controls - Actions, such as legal controls, that help minimize the potential for human exposure to
contamination by ensuring appropriate land use.
Safe Drinking Water Act Maximum Contaminant Level (SDWA MCL) - the maximum permissible level of a
contaminant in water that is delivered to any user of a public water system.
Micrograms per Liter (ug/L) - Is a measurement of concentration used to measure how many micrograms of a
contaminant are present in one liter of water. One ug/L is equal to 0.001 milligrams per liter (mg/L).
Milligrams per Liter (mg/L) - Is a measurement of concentration used to measure how many milligrams of a
contaminant are present in one liter of water. One mg/L is equal to 1000 micrograms per liter (ug/L).
Monitoring - ongoing collection of information about the environment that helps gauge the effectiveness
of a cleanup action. Ground water monitoring will continue at the North Cavalcade Street Superfund Site to
document trends in contaminant concentrations for both zones of interest.
Monitored Natural Attenuation (MNA) - refers to a ground water remedy that relies on natural processes to
cleanup or attenuate pollution and actively monitors these processes.
National Oil and Hazardous Substance Pollution Contingency Plan (NCP) - Regulations governing cleanups
under EPA's Superfund program.
National Priorities List (NPL) - EPA's list of the most serious uncontrolled or abandoned hazardous waste sites
identified for possible long-term remedial response.
Natural Attenuation - The processes in soil and ground water environments that act without human intervention
to reduce the mass, toxicity, mobility, volume, or concentrations of contaminants in those media. These in-situ
processes include biodegradation, dispersion, dilution, adsorption, volatilization, and chemical or biological
stabilization or destruction of contaminants.
Proposed Alternative - Final remedial alternative that meets NCP evaluation criteria and is supported by
regulatory agencies.
Remedial Action - Action(s) taken to correct or remediate contamination.
13
-------
Remedial Action Objectives (RAOs) - Remediation objectives for protection of human health and the
environment.
Record of Decision (ROD) - A formal document that is a consolidated source of information about a Superfund
site, the remedy selection process, and the selected remedy.
For more information, please contact:
Camille Hueni, Remedial Project Manager
U.S. EPA, Region 6
1445 Ross Ave. (6SF-RA)
Dallas, TX 75202
214-665-2231
800-533-3508 (toll free)
Hueni. Camille @epa. gov
June Hoey, Community Involvement Coordinator
U.S. EPA, Region 6
1445 Ross Ave. (6SF-TS)
Dallas, TX 75202
214-665-8522
800-533-3508 (toll free)
Hoev.Phyllis@epa.gov
David Bary, EPA Region 6 Press Office
U.S. EPA, Region 6
1445 Ross Ave. (6XA-CE)
Dallas, TX 75202
214-665-2208
800-887-6063 (toll free)
Bary.David@epa.gov
Marilyn Long, Project Manager
Texas Commission on Environmental Quality
MC-136
P.O. Box 13087
Austin, TX 78711
512-239-0761
Marilvn.Long@tceq .state.gov
14
-------
LEGEND
[_ Jsite Boundary
0.5
Miles
HOU \\HOLLISTER\PROJ\CAVALCADE\MAPFILES\NCRA VICINITY MAP ZOOM.MXD GTWIGG 6/14/2011 10:13:57 AM
FIGURE 1
Site Location Map
North Cavalcade Street Superfund Site
Remedial Action
Houston, Harris County, Texas
CH2IWIHILL
-------
Control District Eas ment
Onsite Commercial Buildings
Solidified Source Areas
LEGEND
iRailroad [_ Jsite Boundary
Stream 2'n"Situ Stabilization Areas
Streets
200
I
400
I
Feet
HOU \\HOLLISTER\PROJ\CAVALCADE\MAPFILES\NCRA SITEMAP NEW.MXD GTWIGG 6/22/2011 4:59:47 PM
FIGURE 2
Site Map
North Cavalcade Street Superfund Site
Remedial Action
Houston, Harris County, Texas
CH2MHILL
-------
WEST
TYPICAL
SHALLOW SAND
MONITOR WELL
FUTURETOLL
ROAD EXPANSION
-20
-40
-60
==,= ,==,= ,==,= ,====,= ,==,= ,==^- = ,==,= ,====,= ,==,= ,==, = DIRECTION OF GROUND , = ==,=
WATER FLOW
SHALLOW SAND
(interbedded sand and silt)
INTERBEDDED UNIT
(interbedded silt and clay)
EXTENT OF DISSOLVED CONTAMINATION
GROUND WATER
Q.
-------
MW-321
MW-32S
MW-281
MW-28S
MW-05
MW-571
MW-37S
MW-371
MWr53l
MW-53S
MW-41S
MW-411
i MW-38S
MW-38I
MW-45S
MW-45I
Northwest
_ V SW XB
Source Area
MW-33S
MW-331
MW-29S
MW-29I
MW-60S
MW-60I
MW-59I
MW-59S
MW-42S
^^^^m
MW-42I
MW-34I
MW-34S
MW-46S
MW-46I
MVVz39,S
MW-39I
MW-47S
MW-47I
JVIW-35S
MW-351
Cavalcade St
Approximate Location of
Pecore Fault Line
LEGEND
Permanent Monitor Well
In-Situ Stabilization Areas
] Approximate Extent of NAPL Product in the Interbedded Unit (2004 Data)
Residual Line-lnterbedded
FIGURE 4
Cross-Section Location Map
North Cavalcade Superfund Site
Remedial Action
Houston, Harris County, Texas
Approximate scale in feet
HOU \\HOLLISTER\PROJ\CAVALCADE\MAPFILES\2011 XSECTION LOCS.MXD FLONDON 6/27/2011 1:54:51 PM
CH2MHILL
-------
200
400
600
800
1.000
1.200
1.400
1.600
§
_gj
LJJ
SAND AND CLAY UNIT
SHALLOW SAND
10
200
400
600
800 1,000
Distance Along Baseline (ft)
1,200
1,400
1,600
15
10
1,800
VERTICAL SCALE: 1" = 6.9'
HORIZONTAL SCALE: 1" = 124.1'
VERTICAL EXAGGERATION = 18.Ox
Note:
The geologic interpretations on this map were generalized from and interpolated
between drilling points. Information on actual subsurface conditions exists only
at the specified locations. The actual subsurface conditions may differ from
those interpreted on this cross section.
U - Not detected above detection limit
J - Estimated value
COC Concentrations [|jg/L]
(analyzed Dec 2010)
Benzene
Napthalene
-p Top of Screen
_ Shallow Sand Water Level
(measured in December 2010)
_ Interbedded Unit Water Level
(measured in December 2010)
-L- Bottom of Screen
LITHOLOGY GRAPHICS
p3 Soil BfM Concrete
Silt
Fat Clay
Clayey Sand
I Silty Sand
Lean Clay
Poorly-Graded
I Sand
No Recovery
Asphalt
Fill
MW59*1
/V46S MW42S M' '
W46I MW4:
FIGURES
A-A' CROSS-SECTION
North Cavalcade Superfund Site
Houston, Texas
CH2MHILL
-------
100
150
200
250
300
350
400
450
500
§
_gj
LJJ
SAND AND CLAY UNIT
SHALLOW SAND
15
10
50
100
150
200
250
300
350
400
450
15
10
500
Distance Along Baseline (ft)
VERTICAL SCALE: 1" = 6.9'
HORIZONTAL SCALE: 1" = 34.5'
VERTICAL EXAGGERATION = 5.0x
Note:
The geologic interpretations on this map were generalized from and interpolated
between drilling points. Information on actual subsurface conditions exists only
at the specified locations. The actual subsurface conditions may differ from
those interpreted on this cross section.
U - Not detected above detection limit
J - Estimated value
COC Concentrations [|jg/L]
(analyzed Dec 2010)
Benzene
Napthalene
-p Top of Screen
_ Shallow Sand Water Level
(measured in December 2010)
_ Interbedded Unit Water Level
(measured in December 2010)
Bottom of Screen
LITHOLOGY GRAPHICS
Silt
Silty Sand
No Recovery
I Clayey Sand KxxlH Lean Clay
Fat Clay
Fill
I 'I Poorly-Graded
I: ' 'I Sand |
K0| Clayey Sand
I Silty Sand
Silty Sand
431
43S
MW/441
FIGURES
B-B' CROSS-SECTION
North Cavalcade Superfund Site
Houston, Texas
CH2MHILL
-------
Thickness
in Feet
11
Proposed Boundary of
Technical Impracticability Zone
490 ft Naphthaelene
Iso-Concentration Contour
C10-4, C9-5 C9-3
;D9-1 {$So^e'AreaD7f MW-55I
{£ MW-29I
Approximate Location of
Pecore Fault Line
LEGEND
^ Permanent Monitor Well
I Proposed Boundary of Technical Impracticability Zone
Naphthalene Iso-Concentration Contour- 490
Approximate Extent of Residual DNAPL in the Interbedded Unit
In-Situ Stabilization Areas
FIGURE 7
Top of Regional Clay Elevation
North Cavalcade Street Superfund Site
Remedial Action
Houston, Harris County, Texas
HOU \\HOLLISTER\PROJ\CAVALCADE\MAPFILES\RESULTS BAP SHALLOW 10-11.MXD FLONDON 6/29/2011 3:13:24 PM
CH2MHILL
-------
MW53I
i
I
10
MW32I
MW37I
MW41
MW46I
MW45I
MW49I
MI/V50I
MW4\8'
MW38I
MW29I
MW57I MW55I
I\|W28I
&l
MW36I
MW42I
IWV4S
MW6CM
MW37I
M\V35I
MW40I
MW31I
Easting
Northing
CH2MHILL
FIGURE 8
INTERBEDDED UNIT THICKNESS
North Cavalcade SuperFund Site
Houston, Texas
-------
Thickness
in Feet
Proposed Boundary of
Technical Impracticability Zone
490 ft Naphthaelene
Iso-Concentration Contour
Northwest
SourcVArea
MW-41J
3
MW-6'OI
__^_
Cavalcade! St
Approximate Location of
Pecore Fault Line
LEGEND
& Permanent Monitor Well
i 1
I I Proposed Boundary of Technical Impracticability Zone
1 foot contour interval
Naphthalene Iso-Concentration Contour- 490
Approximate Extent of Residual DNAPL in the Interbedded Unit
I In-Situ Stabilization Areas
FIGURE 9
Interbedded Unit Effective Thickness
North Cavalcade Street Superfund Site
Remedial Action
Houston, Harris County, Texas
HOU \\HOLLISTER\PROJ\CAVALCADE\MAPFILES\RESULTS BAP SHALLOW 10-11.MXD FLONDON 6/29/2011 8:55:00 AM
CH2MHILL
-------
TT
Proposed Boundary of
Technical Impracticability Zone I
Ul
OW-9
12/2010 0.15 j|
_Gajn_eS-St
MW-37S
12/2010 0.077 U
OW-2
12/20104.9 j|
/ Coastal
Casting
UPS
f490
ND'
MW-33S
12/20102210 = 1
MW-38S
12/20108.6 =
MW-03
2009 99.4 =
12/201012.8 =
Moody St
Q)
U)1
12
MW-60S
7201014.7 =
1
1
MW-42S
12/201019.5 =
\
\
\
>
MW-43S
12/201013 =
/
J
*
MW-38P
12/2010991 J
I
MW-59S L
12/20103.9 dF
1
k ft
MW-39S i
12/20102.6 J T
1
l| -
"1500
Northwest
Source Area
MW-29S
12/201012.1 = \.
JMW-02
] 12/2010 1530 J
-1500-
^Southeast .
Source Area\\
1MW-30S
] 12/2010 6560 JI
El Venado Foods
MW-35S
112/2010723 = 1
490:
MW-07
2009 260 =
112/2010 233 J
H7-1B
2009 10,400 =
110/201015000 =
Cavalcade St
OW-1
2009 2 U
10/201056 jl
OW-8
12/2010 0.078 U
NOTES:
NS - Not Sampled
U - Not detected at reported quantitation limit
J - Estimated value
L - Reported concentration is below the reported quantitation limit
= - Unqualified value above the contract required quantitation limit
* - MW-38S is screened at the top of the shallow sand, and
MW-38I is screened at the bottom of the shallow sand. Data from
MW-38I is used for contouring December 2010 data.
Naphthalene concentrations in micrograms per liter (ug/L).
Naphthalene data is analyzed by method 8270 (SVOC).
Contours based on 10/2010 and 12/2010 data only.
Approximate Location of
Pecore Fault Line
LEGEND
^ New Monitor Well
^P Offsite Well Where Naphthalene Concentration Exceeded 490 ppb
Well Where Naphthalene Concentration Exceeded 1500 ppb
Y//\ In-Situ Stabilization Areas
[Approximate Extent of DNAPL in the Shallow Sand (2004 Data) | j Proposed Boundary of Technical Impracticability Zone
Approximate Extent of Residual DNAPL in the Shallow Sand (2004 Data)
1 Naphthalene Iso-Concentration Contour ° 15° 3(
(Dashed Where Inferred) Feet
HOU \\HOLLISTER\PROJ\CAVALCADE\MAPFILES\RESULTS NAPHTHALENE SHALLOW 2009-10-11.MXD FLONDON 6/27/2011 1:57:11 PM
FIGURE 10
Dissolved Naphthalene in the Shallow
Sand (2009, 2010, 2011)
North Cavalcade Superfund Site
Remedial Action
Houston, Harris County, Texas
CH2MHILL
-------
Proposed Boundary of
Technical Impracticability Zone
MW-291
12/20105790 J
MW-53I
04/2011 5U
MW-55I
12/2010 696 J
MW-54I
12/20106940 J
Northwest
_ V SVS .'U
Source Area
MW-411
12/20102.2 J
04/2011 1.6LJ
MW-46I
12/2010 1070 J
04/2011 2000 =
MW-60I
12/2010 1660 J
04/2011 2.1 U
MW-30I
12/2010 12600 =
Southeast \
s'oufceArea1 1
r / / / y\ I v
MW-421
12/20103340 J
04/2011 9070 =
MW-58I
12/20108650 J
MW-59I
12/20104590 J
H7-2B
10/2010 17000 =
MW-39I
12/20106570 J
MW-43I
12/20103600 J
X. 104/2011 5630 =
MW-35I
12/2010 13600 =
Cavalcade St
MW-40I
J 12/20100.52 =
04/2011 5.1 U
MW-48I
12/2010 15.7 =
04/2011 5.3 U
NOTES:
NS - Not Sampled
U - Not detected at reported quantitation limit
J - Estimated value
L - Reported concentration is below the reported quantitation
= - Unqualified value above the contract required quantitation
* - MW-38I is screened at the bottom of the shallow sand and
data from this well is therefore shown on the shallow sand
plume contour maps.
Naphthalene concentrations in micrograms per liter (ug/L).
Naphthalene data is analyzed by method 8270 (SVOC).
Contours based on 10/2010 and 12/2010 data only.
Approximate Location of
Pecore Fault Line
Proposed Boundary of Technical Impracticability Zone
LEGEND
^ Permanent Monitor Well
Monitor Well Where DNAPL Accumulation Observed April 2011
Offsite Well Where Naphthalene Concentration Exceeded 490 ppb
Well Where Naphthalene Concentration Exceeded 1500 ppb
| In-Situ Stabilization Areas
Approximate Extent of DNAPL in the Interbedded Unit (2004 Data)
J Approximate Extent of Residual DNAPL in the Interbedded Unit
Naphthalene Iso-Concentration Contour
(Dashed Where Inferred)
HOU \\HOLLISTER\PROJ\CAVALCADE\MAPFILES\RESULTS NAPHTHALENE INTERBEDDED 09-10-11.MXD FLONDON 6/27/2011 1:59:16 PM
FIGURE 11
Dissolved Naphthalene in the Interbedded
Unit (2009, 2010, 2011)
North Cavalcade Street Superfund S/te
Remedial Action
Houston, Harris County, Texas
CH2MHILL
-------
Proposed Boundary of
Technical Impracticability Zone
Gaines_St
MW-07
>H2009 1.4 =
T \fl 12/2010 5.8
A
'' ^ \owT~
/ I 2009 1 U
1 / /MO/2010!
MW-43S _/ TTl
Approximate Location of
Pecore Fault Line
Cavalcade-St
NOTES:
NS - Not Sampled
U - Not detected at reported quantitation limit
J - Estimated value
L - Reported concentration is below the reported quantitation limit
= - Unqualified value above the contract required quantitation limit
* - MW-38S is screened at the top of the shallow sand, and
MW-38I is screened at the bottom of the shallow sand. Data from
MW-38I is used for contouring December 2010 data only.
Benzene concentrations in micrograms per liter (ug/L).
Contours based on 10/2010 and 12/2010 data only.
LEGEND
^ New Monitor Well
| Well Where Benzene Concentration Exceeded 5 ppb
\//\ In-Situ Stabilization Areas
i 1
I j Proposed Boundary of Technical Impracticability Zone
J Approximate Extent of DNAPL in the Shallow Sand (2004 Data)
Approximate Extent of Residual DNAPL in the Shallow Sand (2004 Data)
Benzene Iso-Concentration Contour
(Dashed Where Inferred)
HOU \\HOLLISTER\PROJ\CAVALCADE\MAPFILES\RESULTS BENZENE SHALLOW 2009-10-11.MXD FLONDON 6/27/2011 10:27:25 AM
FIGURE 12
Dissolved Benzene in the Shallow
Sand (2009, 2010, 2011)
North Cavalcade Street Superfund Site
Remedial Action
Houston, Harris County, Texas
CH2MHILL
-------
Proposed Boundary of
Technical Impracticability Zone
MW-371
12/2010 0.5 U
MW-55I
12/20104.3 J
_Gaines_St_
Northwest
SourcelArea
Southeast
Source^rea
MW-311
\'. \l 12/2010 0.5 U
MW-30I
12/2010678 =
MW-48I
12/2010 0.5 U
04/2011 0.5 U
MW-56I
12/2010281 =
Cavalcade St
MW-44I
12/2010 0.5 U
04/2011 0.5 U
MW-40I
12/2010 0.5 U
04/2011 0.5 U
NOTES:
NS - Not Sampled
U - Not detected at reported quantitation limit
J - Estimated value
L - Reported concentration is below the reported quantitation limit
= - Unqualified value above the contract required quantitation limit
* - MW-38I is screened at the bottom of the shallow sand and
data from this well is therefore shown on the shallow sand
plume contour maps.
Contours based on 10/2010 and 12/2010 data only.
Benzene concentrations in micrograms per liter (ug/L).
Approximate Location of
Pecore Fault Line
LEGEND
\ New Monitor Well
I Monitor Well Where DNAPL Accumulation Observed April 2011
Well Where Benzene Concentration Exceeded 5 ppb
Y//\ In-Situ Stabilization Areas
Approximate Extent of DNAPL in the Interbedded Unit (2004 Data) | | Proposed Boundary of Technical Impracticability Zone
] Approximate Extent of Residual DNAPL in the Interbedded Unit
^^ Benzene Iso-Concentration Contour
(Dashed Where Inferred)
HOU \\HOLLISTER\PROJ\CAVALCADE\MAPFILES\RESULTS BENZENE INTERBEDDED 2009-10-11.MXD FLONDON 6/27/2011 1:59:22 PM
FIGURE 13
Dissolved Benzene in the
Interbedded Unit (2009, 2010, 2011)
North Cavalcade Street Superfund Site
Remedial Action
Houston, Harris County, Texas
CH2MHILL
-------
Benzo(a)pyrene was not detected in any samples collected;
therefore no iso-concentration contour is shown
MW-32S
12/2010 0.066 U
Proposed Boundary of
Technical Impracticability Zone
MW-28S
12/20100.0.\8
[MW-33S
2/2010 0.066 UJ
MW-21 \
10/201 oo.oeAu
MW-54S
12/2010 0.066 U
MW-38S
12/2010 0.068 U
MW-29S I
12/2010 0.065VJJ
MW-38P
12/20100.071 U
MW-59S
12/2010 0.065 U
MW-42S
12/2010 0.065 U
Southeast
Source Area
12/2010 0.064 UJ
12/2010 0.065 UJ
IViVV-07
2D19 10 U
10A'010 0.069 U
MW-35S
12/2010 0.066 UJ
H7-1B
2009 25 U
10/2010 150U
OW-8 \
10/201 OC\067U
OW-1
2009 5 U
10/2010 5 U
Gavaleade St
NOTES:
NS- Not Sampled
U - Not detected at reported quantitation limit
J - Estimated value
L - Reported concentration is below the reported quantitation limit
= - Unqualified value above the contract required quantitation limit
* - MW-38S is screened at the top of the shallow sand, and
MW-38I is screened at the bottom of the shallow sand
MW-38I is used for contouring December 2010 data.
BaP concentrations in micrograms per liter (ug/L)
If BaP data were analyzed under both SVOC and SIM
analysis, SIM data is shown. SIM analysis performed if SVOC
anlaysis was "non-detect".
SIM analysis was not included in 04/2010 samples.
Approximate Location of
Pecore Fault Line
LEGEND
\ Permanent Monitor Well
4) Well Where BaP Concentration Exceeded 0.2 ppb
\//\ In-Situ Stabilization Areas
_j Proposed Boundary of Technical Impracticability Zone
| Approximate Extent of DNAPL in the Shallow Sand (2004 Data)
Approximate Extent of Residual DNAPL in the Shallow Sand (2004 Data)
1 BaP Iso-Concentration Contour
(Dashed Where Inferred)
HOU \\HOLLISTER\PROJ\CAVALCADE\MAPFILES\RESULTS BAP SHALLOW 10-11.MXD FLONDON 6/27/2011 2:00:48 PM
FIGURE 14
Benzo(a)Pyrene in the Shallow
Unit (2009, 2010, 2011)
North Cavalcade Street Superfund Site
Remedial Action
Houston, Harris County, Texas
CH2MHILL
-------
Proposed Boundary of
Technical Impracticability Zone
MW-551
12/2010 0.065 U
MW-54I
12/2010 0.066 UJ
MW-33I
12/2010 0.066 UJ
Northwest
_ v s\y.'»
Source Area
MW-58I
12/2010 0.066 UJ
12/2010 0.068 UJ
12/2010 0.065 UJ
MW-56I
12/2010 0.065 UJ
MW-59I
12/2010 0.066 U
MW-49I
12/2010 0.067 U
04/2011 5U
Southeast ..
rt' ' / A ' V
Source Area \
12/2010 0.066 UJ
MW-34I
12/2010 0.065 UJ
MW-30I
12/20100.39 =
MW-311
12/2010 0.067 UJ
MW-35I
12/2010 0.065 UJ
MW-47I
12/2010 0.068 U
04/2011 5U
MW-48I
12/2010 0.064 UJ
04/2011 5.3 U
MW-511
12/2010 0.066 UJ
04/2011 5U
Cavalcade St
NOTES:
NS - Not Sampled
U - Not detected at reported quantitation limit
J - Estimated value
L- Reported concentration is below the reported quantitation limit
= - Unqualified value above the contract required quantitation limit
* - MW-38I is screened at the bottom of the shallow sand and
data from this well is therefore shown on the shallow sand
plume contour maps.
Contours based on 10/2010 and 12/2010 data only.
BaP concentrations in micrograms per liter (ug/L).
If BaP data were analyzed under both SVOC and SIM
analysis, SIM data is shown. SIM analysis performed if SVOC
anlaysis was "non-detect".
SIM analysis was not included in 04/2010 samples.
Approximate Location of
Pecore Fault Line
LEGEND
^ Permanent Monitor Well
p- Monitor Well Where DNAPL Accumulation Observed April 2011
Well Where BaP Concentration Exceeded 0.2 ppb
In-Situ Stabilization Areas
I Approximate Extent of DNAPL in the Interbedded Unit (2004 Data)
Approximate Extent of Residual DNAPL in the Interbedded Unit
^^ BaP Iso-Concentration Contour
(Dashed Where Inferred)
| | Proposed Boundary of Technical Impracticability Zone
HOU \\HOLLISTER\PROJ\CAVALCADE\MAPFILES\RESULTS BAP INTERBEDDED 10-11.MXD FLONDON 6/27/2011 2:02:35 PM
FIGURE 15
Benzo(a)Pyrene in the Interbedded
Unit (2009, 2010, 2011)
North Cavalcade Super/one/ Site
Remedial Action
Houston, Harris County, Texas
CH2MHILL
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