&EPA
United States
Environmental Protection
Agency
Grand Plaza Site Investigation Using
the Triad Approach and Evaluation
of Vapor Intrusion
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EPA/540/R-07/002
September 2006
Grand Plaza Site Investigation Using the Triad
Approach and Evaluation of
Vapor Intrusion
National Risk Management Research Laboratory
Office of Research and Development
U.S. Environmental Protection Agency
Cincinnati, Ohio 45268
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Notice
The information in this document has been funded by the U.S. Environmental Protection Agency (USEPA) under
Contract Number 68-C-00-186 to Environmental Quality Management (EQM), Inc. and EQM's subcontractor, URS
Corporation. It has been subjected to the Agency's peer and administrative review and has been approved for
publication as an EPA document. Mention of trade names or commercial products does not constitute endorsement
or recommendation for use.
11
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Foreword
The U.S. Environmental Protection Agency (EPA) is charged by Congress with protecting the Nation's land, air,
and water resources. Under a mandate of national environmental laws, the Agency strives to formulate and
implement actions leading to a compatible balance between human activities and the ability to natural systems to
support and nurture life. To meet this mandate, EPA's research program is providing data and technical support for
solving environmental problems today and building a science knowledge base necessary to manage our ecological
resources wisely, understand how pollutants affect our health, and prevent or reduce environmental risks in the
future.
The Natural Risk Management Research Laboratory (NRMRL) is the Agency's center for investigation of
technological and management approaches for preventing and reducing risks from pollution that threaten human
health and the environment. The focus of the Laboratory's research program is on methods and their cost-
effectiveness for prevention and control of pollution to air, land, water, and subsurface resources; protection of water
quality in public water systems; remediation of contaminated sites, sediments and ground water; prevention and
control of indoor air pollution; and restoration of ecosystems. NRMRI collaborates with both public and private
sector partners to foster technologies that reduce the cost of compliance and to anticipate emerging problems.
NRMRL's research provides solutions to environmental problems by developing and promoting technologies that
protect and improve the environment; advancing scientific and engineering information to support regulatory and
policy decisions; and providing the technical support and information transfer to ensure implementation of
environmental regulations and strategies at the national, state, and community levels.
This publication has been produced as part of the Laboratory's strategic long-term research plan. It is published and
made available by EPA's Office of Research and Development to assist the user community and to link researchers
with their clients.
Sally C. Gutierrez, Director
National Risk Management Research Laboratory
ill
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Abstract
This document provides a detailed report about a field study conducted by EQM/URS on behalf of EPA/NRMRL to
characterize the subsurface contamination of volatile organic compounds (VOCs) at a Brownfield commercial site.
The TRIAD approach was implemented to characterize the extent of soil, groundwater, and soil gas contamination.
These data were used to assess impact on indoor air due to vapor intrusion. Seventy-seven soil samples, twenty-
eight groundwater samples, and ten soil-gas samples were collected from Geoprobe™ borings and analyzed on-site
by USEPA Method SW-846 8265 direct sampling ion trap mass spectrometry (DSTIMS). Additional SW-8260b
and TO-15 analyses were performed on approximately 10% of the samples by off-site laboratories.
Tetrachloroethylene (PCE), trichloroethylene (TCE) and cis-l,2-dichloroethylene (DCE) were detected in all media
with PCE as the prevalent compound.
The on-site analyses for PCE were 22% higher than the off-site analyses for methanol extracts from soil samples.
For the shallow soil-gas samples, the on-site results for PCE agreed with the off-site analyses within about one order
of magnitude for the sample pairs where PCE was present at concentrations >10 ppbv. The off-site results for the
sub-slab soil-gas samples were several orders of magnitude higher than the on-site results, perhaps due to limitations
in the on-site sampling and analytical approach at these high concentrations. The geology was interpreted from the
boreholes and logs from previously drilled groundwater monitoring wells. All data indicated that there was a small
PCE hot spot that was roughly 40 ft by 40 ft (12m by 12m). The hot spot was shallow (less than 10 feet [3m] below
ground surface [bgs]) on top of a low permeability clay under the southwestern edge of the building where a
drycleaner was once located.
Canister samples of indoor air were collected in April and August of 2005. The results were compared with shallow
soil-gas and sub-slab soil-gas results to assess the impact of this contamination on the indoor air. PCE
concentrations in the five indoor air samples ranged from 3.7 to 16 ppbv, with four of five results between 10 and 16
ppbv. For comparison, the ambient air contained 0.11 ppbv. The six samples of shallow soil-gas collected at a
depth of 5 feet (1.5m) bgs directly within or near the building had from 3 9 to 780 ppbv of PCE. The highest of the
three sub-slab soil-gas samples had 2,600,000 ppbv of PCE. The time-averaged indoor air concentration of 12 ppbv
corresponds to a cancer risk of 2E-05 based on an inhalation unit risk (IUR) of 3.0E-06 per |J.g/m3 and an
occupational exposure scenario of 8 hr/day, 5 day/week, 50 week/yr for 25 years.
The productivity of the aquifer was evaluated at several monitoring wells using two methods: slug test and a
constant discharge test. The results of both types of tests demonstrate that site well yields are significantly greater
than the 150 gallons per day criterion used by the Texas Commission on Environmental Quality (TCEQ) to
differentiate between Class 2 (potential) and Class 3 (non-potential) groundwater resources. Therefore, the shallow
groundwater zone at this site is designated a Class 2 groundwater resource.
IV
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Contents
Notice ii
Foreword iii
Abstract iv
Acronyms, Abbreviations, and Symbols ix
Acknowledgements xii
Executive Summary ES-1
1.0 Introduction 1
2.0 Site Description 2
2.1 Site History 2
2.2 Previous Site Investigations 2
2.3 Site Geology and Hydrogeology 6
3.0 Technical Approach 8
3.1 Schedule of Field Activities 8
3.2 Study Design 8
3.2.1 Site Characterization 8
3.2.2 Second Round of Air Monitoring 11
3.2.3 Installation of Groundwater Monitoring Wells 11
3.2.4 Slug Tests 11
3.2.5 Design of Control System 11
3.3 Sampling Procedures 12
3.3.1 Sample Collection for On-Site Analyses 12
3.3.2 Sample Collection for Off-Site Analyses 14
3.4 Analytical Procedures 15
3.5 Sample Handling and Chain of Custody Procedures 16
4.0 Results 17
4.1 On-Site Analytical Results for Site Characterization 17
4.1.1 Groundwater 17
4.1.2 Soil 17
4.1.3 On-Site Soil Gas 17
4.2 Results of Off-Site Analysis of Groundwater 17
4.3 Results of Slug Tests 20
4.4 Evaluation of Vapor Intrusion 20
4.4.1 Off-Site Analysis of Soil Gas 20
4.4.2 Off-Site Analysis of Indoor and Ambient Air Samples 20
4.4.3 Design of Control System 20
4.5 Health and Safety 20
4.6 Waste Disposal 20
4.7 Results of Quality Control (QC) Checks 20
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5.0
7.0
Contents (continued)
Discussion Results 37
5.1 Site Characterization 37
5.1.1 Groundwater 37
5.1.2 Soil 42
5.1.3 On-Site Soil-Gas 55
5.2 Evaluation of Vapor Intrusion 55
5.2.1 Off-Site Analysis of Soil-Gas 55
5.2.2 Off-Site Analysis of Indoor and Ambient Air Samples 56
5.2.3 Tracer Gas Tests 56
5.2.4 Evaluation of Vapor Intrusion 57
6.0 Specifications for Control System for Grand Plaza Site 60
6.1 Location 60
6.2 Site Specific Conditions 60
6.3 Active Soil Depressurization System 60
6.3.1 Depressurization Fan 61
6.3.2 Pipe and Fittings 61
6.3.3 Suction Point 62
6.3.4 Sealing 62
6.3.5 Asbestos Containing Materials 62
6.3.6 Excavation and Rapair 62
6.3.7 Painting 63
6.3.8 Labeling Requirements 63
6.4 Figures and Details 63
References 78
Appendix A Drilling Logs for Ten Groundwater Monitoring Wells
Appendix B Field Data Sheets for Groundwater Monitoring
Appendix C Field Data Sheets for Soil-Gas Sampling
Appendix D Analytical Report from Kemron for Groundwater Samples from October 2005
Appendix E Analytical Report from Kemron for Groundwater Samples from December 2005
Appendix F Results of Slug Tests for Groundwater Monitoring Wells
Appendix G Analytical Report from Air Toxics for Soil-Gas Samples
Appendix H Analytical Report from Air Toxics for Air Samples Collected in April 2005
Appendix I Analytical Report from Air Toxics for Air Samples Collected in August 2005
Appendix J Site Inspection Report for Design of Control System
Appendix K Analytical Report from Kemron for Soil Extract Samples
VI
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Tables
3-1 Schedule of Field Activities 10
3-2 Primary Compounds of Interest 10
3-3 Summary of Sampling Methods 12
3-4 Canister Samples for Off-Site Analysis During April Sampling Event 14
3-5 Summary of Sampling and Analytical Methods for VOCs 16
4-1 Results of On-Site Analysis of Groundwater Samples 21
4-2 Results of On-Site Analysis of Soil Samples 22
4-3 Results of On-Site Analysis of Soil-Gas Samples 26
4-4 Results of Off-Site Analysis of Groundwater Samples Collected in October 2005 27
4-5 Results of Off-Site Analysis of Groundwater Samples Collected in December 2005 28
4-6 Results of On-Site Monitoring of Groundwater Samples Collected in October 2005 29
4-7 Results of Off-Site Monitoring of Groundwater Samples for MNA Parameters 30
4-8 Results of Off-Site Monitoring of MW-9 Sample for Selected Parameters 30
4-9 Results of Off-Site Analysis of Soil-Gas Samples Collected in April 2005 31
4-10 Comparison of Results for Shallow and Sub-Slab Soil-Gas Samples Collected in April 2005 31
4-11 Results of Off-Site VOC Analysis of Indoor Air and Ambient Air Samples
for April 2005 32
4-12 Results of Off-Site VOC Analysis of Indoor Air Samples for August 2005 32
4-13 Results of Off-Site Tracer Gas Analysis of Indoor Air Samples for August 2005 33
4-14 Results of On-Site Duplicate Analysis of Groundwater Sample 33
4-15 Results of On-Site Duplicate Analysis of Soil Samples 34
4-16 Comparison of On-Site and Off-Site Analysis of Soil Samples 34
4-17 Comparison of On-Site and Off-Site Analysis of Soil-Gas Samples 35
4-18 Results of Off-Site VOC Analysis of Groundwater QC Samples 36
4-19 Results of Off-Site Analysis of Groundwater QC Samples for MNA Parameters 36
5-1 PCE and TCE in Groundwater Over Time 41
Vll
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Figures
ES-1 3-D Plot of Subsurface PCE Contamination in Soil ES-2
2-1 Front View of Former Dry Cleaning Facility 3
2-2 Back View of Former Dry Cleaning Facility 3
2-3 Front Room of Former Dry Cleaning Facility 4
2-4 Dining Area Adjacent to Former Dry Cleaning Facility 4
2-5 Fry Room at Former Dry Cleaning Facility 5
2-6 Back Room at Former Dry Cleaning Facility 5
3-1 Sample Location Map 9
3-2 Large Direct-Push Rig 8
3-3 Dolly Rig 11
3-4 Sub-Slab and Indoor Air Sampling Locations 13
4-1 Depth to Bedrock 18
4-2 Geologic Cross-Section A-A' 19
5-1 Groundwater Isoconcentration Contour (PCE ug/L) 38
5-2 Groundwater Isoconcentration Contour (TCE ug/L) 39
5-3 Groundwater Isoconcentration Contour (DCE ug/L) 40
5-4 Soil Isoconcentration Contours (PCE ug/kg 0-1 ft) 43
5-5 Soil Isoconcentration Contours (PCE ug/kg 1-10 ft) 44
5-6 Soil Isoconcentration Contours (PCE ug/kg >10 ft) 45
5-7 Soil Isoconcentration Contours (TCE ug/kg 0-1 ft) 46
5-8 Soil Isoconcentration Contours (TCE ug/kg 1-10 ft) 47
5-9 Soil Isoconcentration Contours (TCE ug/kg >10 ft) 48
5-10 Soil Isoconcentration Contours (DCE ug/kg 0-1 ft) 49
5-11 Soil Isoconcentration Contours (DCE ug/kg 1-10 ft) 50
5-12 Soil Isoconcentration Contours (DCE ug/kg >10 ft) 51
5-13 3-D PCE Plume Based on Soil Data 52
5-14 3-D TCE Plume Based on Soil Data 53
5-15 3-D DCE Plume Based on Soil Data 54
6-1 Installation Schematic 64
6-2 Location of Suction Points 65
6-3 Pictorial Indication of System Locations and Details 66
6-4 Detail 1 Suction Pif 67
6-5 Detail 2 Vent Discharge 68
Vlll
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Acronyms, Abbreviations, and Symbols
a
ACH
bgs
BSA
°C
cfm
cm
CVC
DCB
DCE
Dec
DL
DSITMS
dup
BCD
EPA
ESA
ft
ft2
g
GC
gpd
gpm
He
Hg
H20
hr
HVAC
in.
IUR
Kg
Alpha (attenuation factor)
Alpha based on soil-gas data
Air changes per hour (hr"1)
Below ground surface
Brownfields Site Assessment
Degrees Celsius
Cubic feet per minute
Centimeter
Colorado Vintage Companies
Dichlorobenzene
Dichloroethylene
December
Detection limit
Direct sampling ion trap mass spectrometry
Duplicate
Electron capture detector
Environmental Protection Agency
Environmental site assessment
Feet
Square feet
Gram
Gas chromatography
Gallons per day
Gallons per minute
Helium
Mercury
Water
Hour
Heating, ventilation, and air conditioning
Inches
Inhalation unit risk
Kilogram
IX
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Acronyms, Abbreviations, and Symbols (continued)
L Liter
m Meter
m2 Square meters
m3 Cubic meters
MCL Maximum contaminant level
min Minute
mL Milliliters
MNA Monitored natural attenuation
MPS Multi-probe system
MSD Municipal Setting Designation
mV Millivolt
MW Monitoring well
ND Not detected
NIST National Institute of Standards and Technology
O2 Oxygen
Oct October
ORP Oxidation reduction potential
OSHA Occupational Safety and Health Administration
AP Pressure differential
pa Pascal (unit of pressure)
PCE Tetrachloroethylene
PCL Protective concentration levels
PID Photo-ionization detector
ppbv Part-per-billion on a volume basis
ppm Part-per-million
PRT Post-run tubing
PVC Polyvinyl chloride
Qeidg Ventilation air flow rate for building
QC Quality control
QSoii Vapor intrusion flow rate into building
RPD Relative percent difference
|j,S/cm Micro-siemens per centimeter
SB Soil boring
SF6 Sulfur hexafluoride
SIM Selective ion mode
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Acronyms, Abbreviations, and Symbols (continued)
SVOCs Semi-volatile organic compounds
TCE Trichloroethylene
TCEQ Texas Commission on Environmental Quality
TDS Total dissolved solids
TO Toxic organic
TRRP Texas risk reduction program
TX Texas
|j,g Micrograms
|j,g/m3 Micrograms per cubic meter
US United States
V Volt
VC Vinyl chloride
VI Vapor intrusion
VOCs Volatile organic compounds
XBidg Tracer gas concentration in indoor air
Xtrace,. Tracer gas concentration at source
YSI Yellow Springs Instrument
XI
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Acknowledgments
This report was prepared under the direction of Dr. Michelle Simon, the U.S. Environmental Protection Agency
(EPA) Superfund Innovative Technology Evaluation (SITE) project manager at the National Risk Management
Research Laboratory (NRMRL) in Cincinnati, Ohio. The work was performed under Field Evaluation and
Technical Support (FEATS) Contract No. 68-C-00-186. The prime contractor was Environmental Quality
Management (EQM); Mr. Robb Amick served as the Program Manager. This report was prepared by Mr. Bart
Eklund, Mr. Robert Schafer, and Mr. Derek Peacock of URS Corporation under subcontract to EQM. Mr. Doug
Kladder of Colorado Vintage Companies prepared Section 6 of the report.
The fieldwork was performed by the following individuals. From URS, Messers. Bart Eklund (Project Manager),
Eric Anderson (Chemist), Derek Peacock (Engineer), Robert Schafer (Geologist), Robert Smith (Geologist), and
Mark Sollman (Geologist). From Tri-Corders, Dr. William Davis (Chemist). From Colorado Vintage Companies,
Mr. Doug Kladder (Engineer).
The cooperation and participation of the following people are gratefully acknowledged: Ms. Ann Grimes of the City
of Dallas, Office of Economic Development, Brownfields Program; Mr. Mark Obeso, Assistant Director, City of
Dallas Housing Department; and Mr. Mike Frew, Texas Commission on Environmental Quality, Brownfields
Coordinator.
xil
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Executive Summary
The U.S. Environmental Protection Agency (U.S.
EPA) undertook a project to characterize subsurface
contamination and evaluate the potential for vapor
intrusion (VI) at the Grand Plaza Shopping Center in
Dallas, Texas. There is subsurface contamination of
chlorinated solvents beneath the southwest end of the
building, where a dry cleaning was once located. In
recent years, a series of restaurants have occupied the
space.
The site investigation built upon several past
Brownfield Site Assessments (BSAs) previously
completed at the site. Based on the past work, it was
known that groundwater and shallow soil in the
vicinity of the former dry cleaner is impacted by
tetrachloroethylene (PCE), trichloroethylene (TCE),
and cis-l,2-dichlorothylene (DCE). The
concentrations of metals and SVOCs were below the
applicable regulatory levels in both soil and
groundwater samples and therefore were no longer
considered chemicals of concern for the property.
First, an intensive site characterization effort was
performed. A Triad approach was used; i.e., real-
time or rapid response analytical data were used on-
site to reach decisions. The general approach for site
characterization was to collect soil, groundwater, and
soil-gas samples using direct-push equipment - from
both inside and outside of the building - and analyze
the samples on-site using EPA Method 8265, direct
sampling ion trap mass spectrometry (DSITMS).
Analytical run times of approximately three minutes
per sample allowed low ppb-level data to be
generated at a rapid rate. Approximately 10% of all
samples were also analyzed by off-site laboratories.
Drilling logs from the study area generally record the
presence of silty clay deposits from 0 to 20 ft (0 to
6m) bgs, and fine- to coarse-grained sand deposits
from 20 ft (6m) bgs to bedrock, the depth to which is
highly variable within the area. The depth to bedrock
varies from less than 20 ft (6m) bgs in the
northeastern portion of the study area, to greater than
70 ft (30m) bgs in the northwestern portion of the
study area. Within the study area, shallow
groundwater is present at a depth of approximately
30 ft (9m) bgs within the sandy deposits of the
terrace alluvium.
The site characterization effort indicated that the
subsurface contamination was largely confined to a
small area beneath the former dry cleaning business.
All soil samples from outside the building were <0.4
ppm for all compounds. Contamination was detected
in all borings down to a depth of 20 ft (6m) bgs. Soil
samples from underneath the building contained up to
3.4 ppm of PCE, 2.3 ppm of TCE, and 6.4 ppm of
DCE. The soil data for PCE are plotted in Figure
ES-1. All groundwater concentrations outside the
building were <0.1 ppm and all groundwater
concentrations beneath the building were <0.4 ppm.
The groundwater and soil data sets suggest that the
PCE has undergone substantial degradation to TCE
and DCE. No vinyl chloride (VC), however, was
detected. In addition, benzene and toluene were not
detected.
Aquifer production tests conducted at MW-7, MW-9,
and MW-10 demonstrated well yields of 1,400 to
20,000 gpd (5,300 to 75,700 L/day) that are greater
than the 150 gpd (570 L/day) criterion. Therefore,
the groundwater at this site is designated Class 2
according to Texas regulatory guidance.
Shallow soil-gas samples were collected at six
locations at a depth of 5 ft (1.5m) bgs and three sub-
slab soil-gas samples also were collected. PCE in the
shallow soil gas ranged from 0.039 to 0.71 ppmv.
TCE concentrations were similar to the PCE
concentrations, whereas DCE tended to be higher (up
to 29 ppmv). The presence of TCE, DCE, and VC is
additional evidence that the PCE has been degraded.
Soil-gas data at the site indicate a surprisingly large
degree of spatial variability. The gas-phase
subsurface contamination was found to exist in one
relatively small "hot spot". The data suggest that the
contamination has largely remained in place under
the slab near its release point with only limited
vertical and lateral transport.
ES-1
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w
¥
to
l«atna
V
URS
to M9*g PCE isoe«x«nlr*(ioo
Grand Avenue Plaza
3103 Grand Avenue
Figure ES-1
3-D PCE Plums
Based on April 2005
Soil Data
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In conjunction with the site characterization,
additional fieldwork was performed to evaluate vapor
intrusion at the site. PCE was detected in multiple
indoor air samples at about 12 ppbv (83 |J.g/m3).
Ambient air contained only 0.11 ppbv of PCE and
does not appear to have been a significant source of
this compound in the indoor air. The building
ventilation rate was determined using a tracer gas.
The measured values of 1 to 2 ACH at the Grand
Plaza site appear to be relatively low for a restaurant,
but are much higher than the default value of 0.25
ACH in the US EPA November 2002 guidance,
which is based on the 10th percentile for single
residence buildings.
The ratio of indoor air to soil-gas concentrations is
often evaluated in vapor intrusion studies. This ratio
typically is called the attenuation factor or a.
Published values of aSG tend to be O.001. The EPA
default aSG value for screening purposes currently is
0.1, but is expected to decrease to 0.02 when the
2002 EPA guidance is revised sometime in 2007.
The three sub-slab soil-gas samples had 18,000,000;
26,000; and 59,000 |ag/m3 of PCE. The three indoor
air samples had 85, 68, and 96 |J.g/m3, for a mean of
83 |J.g/m3. Therefore, aSG = 5.3xlO"6 using the
maximum values and aSG = 1.4xlO"5 using the
average values. The values of aSG for other
compounds detected in the sub-slab soil-gas are also
in the 10"6 range using the maximum values.
The risk from inhalation of PCE at this site is
conservatively estimated to be 2xlO"5, based on an
inhalation unit risk for PCE of 3.0xlO"6 per |J.g/m3
and a 25-year occupational exposure scenario. The
estimated risk falls within the IxlO"4 to IxlO"6 risk
management range and there is no requirement for
mitigation of vapor intrusion at this site based on
State standards. A control system was designed as
part of this study but ultimately was deemed to be not
necessary. Future steps to achieve site closure are
expected to involve seeking a Municipal Setting
Designation (MSD) or a deed restriction for the site.
The results for this site have several implications for
the standard regulatory approach for evaluating vapor
intrusion. One, field investigations at sites with
surface releases should include measurements in
surface soil layers. Groundwater, soil, and soil-gas
measurements at depth may not identify the
maximum concentrations present at the site. The
study illustrates the extreme spatial variability that is
sometimes found in the subsurface at contaminated
sites. Two, the use of mean values instead of
maximum values may still be very conservative when
soil-gas measurements are used to estimate indoor air
concentrations using an aSG of 0.1 or 0.02. Three,
the U.S. EPA defaults for parameters such as Qsoii,
Qeidg, and AP may be very conservative for a given
site. Site-specific measurements can readily be
performed to provide more accurate estimates for
these parameters instead of relying on default values.
ES-3
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SECTION 1
INTRODUCTION
The U.S. Environmental Protection Agency (U.S.
EPA) undertook a project to characterize subsurface
contamination and evaluate the potential for vapor
intrusion (VI) at the Grand Plaza Shopping Center in
Dallas, Texas. There is subsurface contamination of
chlorinated solvents beneath the southwest end of the
building, where a dry cleaning business was once
located. URS Corporation (URS), under contract to
EQM, directed the on-site activities.
The work was performed in two phases during 2005.
During Phase I of the project, soil, groundwater, soil-
gas, and indoor air samples were collected to
characterize the extent of subsurface contamination at
the site and evaluate the potential for vapors to enter
the structure. The majority of analyses were
performed on site using a mobile laboratory, with
additional analyses performed off site to confirm and
complement the on-site data. During Phase II of the
project, additional indoor air measurements were
performed and a system to control the vapors was
designed.
The goals for the project were to:
1. Characterize the three-dimensional aspects of the
chlorinated soil, groundwater, and soil-gas
plume;
2. Determine the productivity of the local shallow
aquifer;
3. Collect sub-slab soil-gas and indoor air data and
use these data to evaluate vapor intrusion at the
site; and
4. Design an active control system to limit vapor
intrusion at the site.
The site characterization work was more thorough
than is often the case at vapor intrusion sites.
Therefore, the study provides a useful case study for
this type of work.
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SECTION 2
SITE DESCRIPTION
The site history is summarized below followed by a
summary of previous site investigations and a short
description of the geology and hydrology in the local
area.
2.1 Site History
The area that was studied lies within a 26,189 ft2
(2,433 m2) single-story retail facility (strip mall)
constructed in 1966 and its adjoining parking lot.
The site is located at 3103 Grand Avenue in Dallas,
Texas. It is in the South Dallas/Fair Park community
about one mile south of the Texas Fairgrounds and
the Cotton Bowl. The neighborhood is low income
and economically underdeveloped.
The strip mall has spaces for nine to ten tenants. A
combined Laundromat and dry cleaning business
originally occupied the southwestern-most portion of
the strip mall in a space that was roughly 30 ft by 70
ft (9m by 21m). The front and back views of the
former dry cleaning business are shown in Figures 2-
1 and 2-2.
Only limited information is available about the
former dry cleaning business. The certificate of
occupancy for Baccus Cleaners is dated October 3,
1966. The application to operate a dry cleaning
establishment is dated April 8, 1970. The facility
was categorized as a Class IV dry cleaning plant and
authorized to store up to 50 gallons (190 L) of
inflammable volatiles. A building permit for June
25, 1971 indicates that the site housed a coin-
operated laundry with 30 washing machines and 15
dryers. An undated building plan indicates that two
dry cleaning machines were located near the front,
right corner of the business. A sump was located
near the back of the business about 6 ft (2m) in from
the back wall. The dry cleaning operation is believed
to have operated from 1970 through 1986.
A series of restaurants later occupied the space that
once housed the dry cleaning business. In recent
years, a restaurant occupied both the former
drycleaner space and the adjacent space, with a
combined area of roughly 60 ft by 70 ft (18m by
21m). The two halves were connected via two
French doors along an internal wall near the front of
the building. The two spaces are shown in Figures 2-
3 and 2-4 (a schematic is given in Section 3, Figure
3-4). At the time of the first phase of this study,
neither space was occupied and the doors between
them were open, allowing air to move freely between
the two spaces. At the time of the second phase of
this study, a new restaurant was operating in the 30 ft
by 70 ft (9m by 21m) space that once housed the dry
cleaning business and the adjacent space was
unoccupied and closed off from the restaurant. The
former dry cleaning facility currently is divided into
three main rooms. The front room shown in Figure
2-3 provides public access to restaurant customers.
The middle room or "fry room" has a large exhaust
hood where food is prepared. The back room has a
walk-in refrigerator and is used for dishwashing and
storage. The back room also contains a small office
partitioned off from the rest of the space. The fry
room is shown in Figure 2-5 and the back room is
shown in Figure 2-6.
2.2 Previous Site Investigations
The Grand Plaza Shopping Center was purchased in
1989 by a non-profit organization. The City of
Dallas Brownfields Program provided a Phase I
Environmental Site Assessment (ESA) for the
property in 2001 as part of the process to secure
funding for building improvements. The ESA
identified several environmental concerns:
• On-site dry cleaning business in operation until
1986;
• Lumber treating plant in the 1950's in operation
adjacent to the property; and
• Underground gasoline storage tank at the lumber
yard that occupied the adjacent property in the
1950's.
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Figure 2-1. Front View of Former Dry Cleaning Facility
Figure 2-2. Back View of Former Dry Cleaning Facility
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Figure 2-3. Front Room of Former Dry Cleaning Facility
Figure 2-4. Dining Area Adjacent to Former Dry Cleaning Facility
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Figure 2-5. Fry Room at Former Dry Cleaning Facility
Figure 2-6. Back Room at Former Dry Cleaning Facility
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A Brownfields Site Assessment (BSA) was
conducted by Leigh Engineering in April 2002 under
the Voluntary Cleanup Program (VCP) of the Texas
Commission on Environmental Quality (TCEQ).
Based on the initial findings, a second BSA was
conducted by Leigh Engineering in August 2002.
During the first BSA, four groundwater monitoring
wells were installed and 22 soil samples were
collected from seven soil boring locations (well
locations are shown in Section 3, Figure 3-1).
Samples were analyzed for metals, volatile organic
compounds (VOCs), and semi-volatile organic
compounds (SVOCs). During the second BSA, a
fifth downgradient monitoring well (MW-5) was
installed. Subsequently, all five monitoring wells
were sampled, a soil-gas sample was collected
beneath the slab of the former dry cleaner, and a
database search was conducted to identify any water
wells within a 1/2-mile (800m) radius of the site.
The first four monitoring wells were installed to
depths of roughly 35 ft to 60 ft (10.7m to 18.3m)
below ground surface (bgs). The depth to
groundwater was determined to be between 28 and
35 ft (8.5 to 10.7m) bgs with an apparent gradient
sloping from west to east across the site. The
bedrock elevations were between 73 and 68 ft (22.2
and 30.7m) bgs.
Analytical results from four of the groundwater
monitoring wells (i.e., MW-1, -2, -4, and -5)
indicated that the groundwater in the vicinity of the
former dry cleaner was impacted by
tetrachloroethylene (PCE), trichloroethylene (TCE),
and/or cis-l,2-dichlorothylene (DCE).1
Contaminants were not detected in the monitoring
well farthest away from the former dry cleaner
(MW-3).
Soil borings 1 through 4 were advanced to 14.5 to 15
feet (4.4 to 4.6m) through the concrete slab in the
former dry cleaning facility using direct push
technology. Soil borings 5 through 7 were advanced
east and south of the dry cleaning facility to 15 feet
(4.6m) using a hollow stem auger drilling. Shallow
soil samples collected from the four borings beneath
the floor of the former dry cleaner at depths of 2 feet
(0.6m) and 4.5-6.5 ft (1.4 to 2.0m) contained PCE,
1 Compared with Texas Risk Reduction Program (TRRP)
Tier 1 Protective Concentration Levels (PCLs) for a 0.5-
acre source area, commercial setting, and drinking water
scenario.
TCE, and/or DCE. The highest concentrations were
in the vicinity of SB-2 between 2.5 and 4.5 ft (0.76
and 1.4m).
Soil samples were also collected during the
installation of the on-site monitoring wells. The
samples were mostly non-detect, but PCE, TCE, and
DCE were detected at low ppm-levels in shallow
soils at some locations.
The concentrations of metals and SVOCs were below
the applicable regulatory levels in both soil and
groundwater samples and therefore were not
considered chemicals of concern at the property. No
water wells were located within a 1/2-mile (800m)
radius of the site according to the database report.
Samples were collected from the five existing
groundwater monitoring wells in July 2003 and
analyzed for VOCs. Three additional groundwater
monitoring wells (MW-6 through -8) were installed
by URS in April 2004 and groundwater samples were
collected at all eight wells in May 2004 and analyzed
for VOCs. The 2004 results were similar to the
results obtained in 2003 for the five existing wells.
PCE, TCE, and cis-l,2-DCE were detected in the
three new wells at concentrations slightly above the
residential Protective Concentration Levels (PCLs).
2.3 Site Geology and Hydrogeology
During the Cretaceous period of the Mesozoic era,
transgression and regression of the sea across north-
central Texas deposited sediments on top of flat-lying
Paleozoic age strata. Near the end of the Cretaceous
period, regional uplift tilted the layers of sediment
toward the east as seas withdrew toward the Gulf of
Mexico. Subsequent transgression and regression of
the sea deposited sediments of Tertiary and
Quaternary age further to the east, as streams eroded
the exposed land to the west and deposited terrace
and alluvial sediments there (Nordstrom, 1982).
At the Grand Plaza Shopping Center, Quaternary age
terrace alluvium (or soils formed therein) is exposed
at ground surface, or lies beneath pavement and
backfill material in this urban area. Regionally, these
sediments are comprised of heterogeneous or
interbedded gravel, sand, silt, and clay mixtures.
Thickness of the alluvium is highly variable, but
deposits are usually less than 75 ft (23m) thick
(Nordstrom, 1982). Drilling logs from the study area
generally record the presence of silty clay deposits
-------
from 0 to 20 ft (0 to 6m) bgs, and fine- to coarse-
grained sand deposits from 20 ft (6m) bgs to bedrock,
the depth to which is highly variable within the area.
The competent bedrock, which is unconformably
overlain by the terrace alluvium, consists of
Cretaceous age Austin Group deposits. Regionally,
the Austin Group is comprised of chalk, limestone,
marl, clay, and sand deposits. Sometimes referred to
collectively as the Austin chalk, the Austin Group
deposits can be up to 700 ft (200m) thick
(Nordstrom, 1982). Drilling within the study area
has penetrated only the first few inches of bedrock,
so the nature of the Austin Group deposits there has
not been defined in detail. However, one drilling log
from the area describes the bedrock surface as light
gray clayey silt, presumably weathered limestone or
marl, that is calcareous (evidenced by its
effervescence in hydrochloric acid), dry to damp, and
hard. The depth to bedrock varies from less than 20
ft (6m) bgs in the northeastern portion of the study
area, to approximately 75 ft (23m) bgs in the
northwestern portion of the study area.
The terrace alluvium and Austin Group deposits are
known regionally to produce only small quantities of
groundwater. The important aquifers of the region
are the Woodbine Group and the Twin Mountains
Formation of the Trinity Group (Nordstrom, 1982).
Like the Austin Group, both of these aquifers are
Cretaceous in age. Other Cretaceous age
stratagraphic units separate the Austin Group from
the deeper aquifers, and the aquifers from one
another. Beneath the study area, the depth to the
Woodbine Group is approximately 850 ft (260m)
bgs, and the depth to the Twin Mountains Formation
is approximately 2,550 ft (780m) bgs (Nordstrom,
1982).
Within the study area, shallow groundwater is present
at a depth of approximately 30 ft (9m) bgs within the
sandy deposits of the terrace alluvium. The bedrock
beneath the alluvium presumably forms a hydrologic
barrier beneath the study area, but its influence on
local groundwater flow has yet to be determined.
The bedrock surface forms a trough that slopes to the
northwest and west, but the apparent direction of
groundwater flow, based on groundwater monitoring
wells in the area, is to the east.
-------
SECTION 3
TECHNICAL APPROACH
This section contains a description of the technical
approach that was employed during the study. The
schedule of field activities and study design are
presented below, followed by brief summaries of the
sampling, analytical, and sample handling
procedures.
3.1
Schedule of Field Activities
The chronology of on-site events is shown in Table
3-1. All field activities were performed in the year
2005.
3.2 Study Design
The general sampling strategies employed during the
initial site characterization work and the second
round of indoor air sampling are described below.
The approach used to install two additional
groundwater monitoring wells, perform slug tests,
and design a control system also are described.
3.2.1 Site Characterization
Target compounds were selected based on existing
soil, groundwater, and soil-gas data collected in past
site characterization efforts undertaken by TCEQ.
The on-site monitoring addressed the six compounds
shown in Table 3-2. PCE is a commonly used dry
cleaning fluid and it is the primary compound of
interest at this site. TCE, DCE, and vinyl chloride
(VC) are thought to be present at the site due to
anaerobic degradation of PCE. For the off-site
analyses, the applicable standard target analyte list
for each analytical method was employed, which
included additional compounds beyond those shown
in Table 3-2.
A sampling array was established over the site with
spacing outside the building of roughly 33 ft by 33 ft
(10m by 10m) and spacing inside the building of
roughly 10 ft by 10 ft (3m by 3m). The sampling
array is shown in Figure 3-1. The sampling array
included eight rows of sampling points: A through H.
Row "A" was behind the back of the building and
Row "H" was along Grand Avenue. The potential
sampling locations on each row were numbered from
low to high in the southwest to northeast direction
(i.e., sampling locations Al, Bl, Cl, etc. were along
the southwest property boundary). Additional rows
of potential sampling locations were established
inside the building (e.g., Rows "M" through "S").
The sampling array included more potential locations
than were actually sampled.
Direct-push drill rigs were used to collect samples. A
66DT unit mounted on a flat-bed truck was used
outside the building and a dolly probe was used
Figure 3-2. Large Direct-Push Rig
indoors. The two rigs are shown in Figures 3-2 and
3-3. Drilling was performed by ESN South of
Corpus Christi, Texas under the supervision of two
URS geologists. The drillers decontaminated non-
dedicated sample equipment with soap and water and
used high-pressure washers for large equipment. A
Triad approach was used (USEPA, 2003a)(ITRC,
-------
+ *
*' «
-f -*•
+ + +
MW*
* * l*sa> *
"' K ° ^A " . ""
A
•
Soil BonaQ LKB&m
DPT Sample Location
Modiiunns i'rtjll LpMl^in
-------
Table 3-1. Schedule of Field Activities
Date
April 11 -15
August 29
August 29 - 30
August 3 1
October 11
October 20 -21
December 13-14
December 13-14
Activity
Collect soil, groundwater, and soil-gas sampling and use on-site analysis to
characterize site. Collect indoor air and soil-gas samples for off-site analysis.
Install groundwater monitoring well MW-9.
Perform second round of indoor air sampling.
Inspect site for design of control system.
Install groundwater monitoring well MW-10.
Collect groundwater samples from 9 o f 10 monitoring wells (no sample
be obtained from MW-2).
could
Collect groundwater samples from MW-2, -9, and -10.
Perform slug tests at MW-7, -9, and -10.
Table 3-2. Primary Compounds of Interest
Compound
Tetrachloroethylene
Trichloroethylene
1 ,2-Dichloroethylene
Vinyl Chloride
Benzene
Toluene
CAS#
127-18-4
79-01-6
156-59-2
156-60-5
75-01-4
71-43-2
108-88-3
Synonyms
PCE, Perk,
perchloroethylene
TCE
cis-l,2-DCE
trans-l,2-DCE
VC, chloroethene
~
~
Molecular
Weight
165.8
131.4
96.9
62.5
78.1
92.1
Conversion Factor
for Air Samples
1 ppb = 6.78 |ag/m3
1 ppb = 5.37 |ag/m3
1 ppb = 3.97 |ag/m3
1 ppb = 2.56 |ag/m3
lppb = 3.19|ag/m3
1 ppb = 3.77 |ag/m3
2003). In this approach, real-time or rapid response
analytical data is used on-site to reach decisions. The
intent is to characterize the site with as few
mobilizations as possible, so the on-site analytical
capabilities are very important to the success of the
approach. In this study, soil, groundwater, and soil-
gas samples were collected using direct-push
equipment and the samples were analyzed on-site.
Analytical results were plotted at the site as they
The US EPA TRIAD approach is described at the
following websites:
http://www.epa.gov/tio/triad/
http://www.clu-in.org/download/char/2004triadfactsheeta.pdf
became available and used to make decisions about
where to collect additional samples.
The depth to bedrock was obtained at 33 locations
where probes were pushed, plus at eight existing
monitoring wells near the building. Groundwater
samples were obtained from five locations beneath
the building and 23 locations outside the building. A
total of 77 discrete soil samples were collected from
15 locations: 20 samples from four locations outside
the building and 57 samples from 11 locations within
the building. All soil samples were collected within
or very near the building. Soil gas sampling was
attempted at 24 locations. The general approach for
evaluating vapor intrusion was to collect time-
integrated soil-gas and indoor air samples in
10
-------
Figure 3-3. Dolly Rig
evacuated, stainless-steel canisters for off-site TO-15
analyses.
3.2.2 Second Round of Air Monitoring
Based on the results of the initial site
characterization, additional samples were collected to
evaluate the potential for vapor intrusion. Indoor air
samples were collected at two locations during the
first round of sampling and at one location during the
second round of sampling. The analyses were
performed off-site.
Tracer gas tests were performed in conjunction with
the second round of indoor air sampling. Pure sulfur
hexafluoride (SF6) was introduced into the sub-slab
to verify that vapor intrusion was occurring. Pure
helium was released within the building to measure
the air exchange rate for the building. Measurement
of helium inside the structure was performed to allow
calculation of the ventilation air flowrate (Qsidg)
using the ratio technique. Under steady-state
conditions, the dilution of the tracer gas is equal to
the ratio of the building ventilation and the tracer gas
release rate:
: V
^Mracer
(Eq. 3-1)
Where:
Qsidg = ventilation air flowrate,
XBidg = tracer gas concentration in indoor air,
Qtracer = tracer gas release rate, and
Xtracer = tracer gas concentration at source.
Qtracer and Xtiace!: were known, and XBidg was measured
in the field.
3.2.3 Installation of Groundwater
Monitoring Wells
Two groundwater monitoring wells (MW-9 and
MW-10) were installed in addition to the eight wells
that already were present at the site. Hollow-stem
auger drilling was used to advance boreholes and
install threaded 2-in. (5 cm) diameter schedule-40
PVC casing, 0.010-in. (0.025 cm) factory-slotted
PVC screen, and a threaded end cap. The annulus
space around each well screen was filled with 20 x
40 mesh silica filter sand to a minimum of 2 ft (0.6m)
above the top of the screen. The sand pack was
sealed from the overlying annulus space with
hydrated 3/8-in. (1 cm) bentonite pellets installed to
just below ground surface. Wells were completed at
ground surface with a flush-mounted 8-in. (20 cm)
diameter manway housed within a concrete pad.
The drilling was performed by Groundwater
Monitoring of Grand Prairie, Texas under the
supervision of a URS geologist. One well (MW-10)
was installed down-gradient of the former
drycleaning facility along Medill Street near its
intersection with Grand Avenue. This location was
selected to help delineate the existing groundwater
plume and was expected to be free of contamination.
The second well (MW-9) was installed adjacent to
the existing monitoring well, MW-8. The depth to
bedrock in this area is approximately 76 ft (23m) bgs
whereas MW-8 extends to only about 50 ft (15m)
bgs. MW-9 was installed to extend to the top of the
bedrock. Drilling logs for all ten monitoring wells are
given in Appendix A.
3.2.4 Slug Tests
Slug tests were performed at MW-5, MW-7, and
MW-9 using four and six ft (1.2 and 1.8m) long
slugs constructed of 1-in. (2.5 cm) diameter PVC
pipe filled with clean gravel and sealed with water-
tight caps. The rise and fall of the water level during
each test was measured using a pressure transducer.
The slug test data was used to calculate approximate
11
-------
hydraulic conductivity values, which were converted
into approximate well yield values using TCEQ
Regulatory Guidance document RG-366/TRRP-8
(TCEQ, 2003). In addition to the TCEQ guidance,
the methodology for slug testing presented in Butler,
et al. (1996) was consulted for designing, conducting,
and evaluating the tests. The data were plotted using
AQTESOLV™ software.
The tests were conducted to determine if the aquifer
production rate was above or below 150 gallons per
day (gpd)(570 L/day), which is the regulatory
boundary between Class 2 and Class 3 aquifers in
Texas (TCEQ, 2003).
3.2.5 Design of Control System
A building inspection was performed by Doug
Kladder of Colorado Vintage Companies (CVC).
The concrete slab was checked for subterranean
beams or other barriers to gas flow via a sound check
using a rubber mallet. Holes were drilled through the
slab at various locations and the differential pressure
between the building and the soil was measured using
an Infiltec DMI model digital micromanometer
(http://www.infiltec.com). To determine the gas
permeability of the sub-slab fill material, a vacuum
was applied at a central hole and the pressure
differential was measured at various lateral distances.
3.3 Sampling Procedures
The sampling methods used in this study are
summarized in Table 3-3. Field data sheets for the
roundwater sampling for off-site analysis are given as
Appendix B. Field data sheets for soil-gas sampling
for both on-site and off-site analysis are given as
Appendix C. Sub-slab and indoor air sampling
locations are shown in Figure 3-4.
3.3.1 Sample Collection for
Analyses
On-Site
Groundwater, soil, and shallow soil-gas samples were
collected for on-site analyses and used to characterize
the subsurface contamination at the site.
Groundwater
One-inch (2.5 cm) PVC was driven to depth and
groundwater recovered by applying suction to YA in.
(0.64 cm) polyethylene tubing. All groundwater
samples were unfiltered, grab samples.
Soil Samples
Soil samples were collected with 2 in. by 3 ft (0.05
by 0.9m) split spoon samplers lined with clear
acetate. Soil cores were visually examined and
screened using a portable photo-ionization detector
(PID). The meters were calibrated daily according to
manufacturer's instructions. All soil samples were
grab samples of approximately 5g collected from
cores at discrete depths using disposable EnCore
samplers and placed in laboratory-supplied vials.
Sampling was intentionally biased towards soils with
relatively high levels of VOCs based on visual
observation and the PID measurements.
Table 3-3. Summary of Sampling Methods
Analysis
Location
On-Site
Off-Site
Medium
Groundwater
Soil
Soil-Gas
Groundwater
Soil
Sub-Slab and Shallow Soil-Gas
Indoor and Ambient Air
Sampling Method
Direct Push / Grab
Direct Push /Grab
Direct Push /Sorbent Trap
Low flow / Micropurge
Direct Push /Grab
Canister
Canister
12
-------
Exhaust
Hood
20.9m
Fry
Room
SS-4
X
• R-2
Back Room
• A
,0-1
xSS-3
®IA-3
IA-1
Front Room
X
SS-1
P4 IA-2
N-4,
SS-2
Continuation
of Strip Mall
D3
D4
Dining
Area
Ambient air sample
Key
• - Soil-gas sampling location
X - Sub-slab soil-gas sampling location
®- Air sampling location
A.- Helium tracer release point
• - Pressure-differential measurement location
Figure 3-4. Sub-Slab and Indoor Air Sampling Locations
Soil Gas
Soil-gas samples were collected at a depth of five ft
(1.5m) below ground surface [bgs] using Geoprobe
Post Run Tubing (PRT). The probe was driven to the
desired depth and the rod pulled back from the
disposable drive tip. A ten ft (3m) length of YA in.
(0.64 cm) polyethylene tubing was fed down the
middle of the rod and turned counter-clockwise until
the PRT adapter screwed into the point holder. The
probes were left in place for a minimum of 30
minutes and the lines purged of three void volumes
before the start of sample collection. The soil-gas
samples generally were collected by drawing sample
air through a sorbent tube for 15 minutes at a flow
rate of 1.0 L/min.
Rotometers were used to control the flow rate of
sample air during collection of soil-gas samples using
sorbent tubes. The multipoint calibrations of the
rotometers using NIST-traceable flow devices were
completed at the URS Austin laboratory, prior to
deployment to the field. Using these calibration data,
sample flows were calculated.
13
-------
Soil gas sampling was attempted at 24 locations, but
samples were obtained at only 10 of these locations.
The remaining 14 locations had high resistance to
soil-gas flow and no sample could be obtained.
Sample collection was not attempted at locations
where there was no detectable reduction in pressure
over a 15-minute period after inducing a vacuum of
15 in. (38 cm) Hg.
3.3.2 Sample Collection for Off-Site
Analyses
Groundwater, soil, shallow soil-gas samples, indoor
air, and ambient air samples were collected for off-
site analyses. The canister samples collected during
the first sampling event are summarized in Table 3-4.
All canister samples were two-hour time-integrated
samples collected in 6-L evacuated, stainless-steel
canisters.
Groundwater
Samples were collected from the 10 permanent
groundwater monitoring wells at the site. The two
new wells were developed prior to sampling. Wells
were purged and groundwater samples were collected
from each well using a 12V submersible pump and
the low-flow sampling (micropurge) technique.
Water quality parameters collected included
temperature, pH, specific conductivity, turbidity,
oxidation-reduction potential, and dissolved oxygen.
Stabilization of all water quality parameters was
achieved and documented prior to sample collection.
During sample collection, groundwater was pumped
directly into pre-preserved sample containers. Field
personnel donned a new pair of disposable nitrile
gloves prior to collecting each sample. Immediately
following sample collection, sample containers were
stored on ice in coolers. All sample containers were
repacked on fresh ice prior to being shipped.
Pumps and tubing were decontaminated in a plastic
tub filled with a mixture of Liquinox soap and water,
and rinsed in a plastic tub of clean water. The pump
was operated within each tub to ensure the circulation
of soap and water inside of the pump housing and
tubing during the cleaning process.
Soil Samples
Extracts from three soil samples analyzed on-site
were sent off-site for confirmatory analysis. Extracts
were used rather than soil to minimize the variability
in the starting material used by analysts at each
location.
Soil Gas
Soil-gas samples were collected at two depths.
Shallow soil-gas samples were collected at six
locations at a depth of 5 ft (1.5m) below the ground
surface (bgs): four locations inside the building and
two locations just outside the building. At the inside
locations, sub-slab soil-gas samples also were
collected by drilling through the floor and collecting
soil gas from immediately beneath the concrete slab.
The shallow soil-gas samples were collected using
the Geoprobe Post Run Tubing (PRT) system
described above. Canister samples were collected
after the collection of sorbent tube samples.
The sub-slab soil-gas probes consisted of a 1A in.
(0.64 cm) swagelok union connected to a 4 in. (10
cm) length of stainless steel tubing that extended to
near the bottom of the slab A 2 in. (5 cm) deep
starter hole was drilled using a hammer drill and a
7/8 in. (2.2 cm) bit. The hole was continued down
through the slab using a 5/16 in. (0.79 cm) bit. The
probes were sealed using quick-dry, expanding
cement. The probes were left in place for a minimum
of 30 minutes and lines purged of three void volumes
before the start of sample collection. A 2 ft (0.6m)
length polyethylene of tubing was used to connect the
canister to the sub-slab probe.
Table 3-4. Canister Samples for Off-Site Analysis During April Sampling Event
Type
Indoor Air
Sub-Slab Soil-Gas
Soil-Gas
Ambient Air
Locations
2
4
4
1
Comments
2-hr integrated samples collected at breathing zone height
Samples collected from immediately beneath the building slab
Samples collected from 5 ft (1.5m) depth near sub-slab
sampling locations
For comparison with indoor air results
14
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Differential pressure measurements were made at
each soil-gas sampling location using a Dwyer
magnehelic gauge (http://www.dwyer-inst.com)
capable of reading to the nearest 0.005 in. H2O (1
Pa).3
Indoor Air
Two rounds of indoor air samples were collected: the
first round in April 2005 and the second in August
2005. During the April sampling event, samples
were collected at two locations: one location within
the former dry cleaner business and one location
within the adjacent "dining room" area that is
connected to the former dry cleaner business (see
Figures 2-3 and 2-4). Samples were collected at
breathing zone height: four to five ft (1.2 to 1.5m)
above floor level. The building HVAC system was
not in use, nor had it been used in the days before
sampling. External building doors were kept closed
during sampling; the building has no windows that
can be opened. An ambient air sample was collected
just outside the building, concurrent with the indoor
air samples.
During the August sampling event, indoor air was
collected at breathing zone height within the middle
section of the restaurant (i.e., "fry room"). The
building HVAC system was operational and in use at
that time. External building doors were kept closed
during sampling.
Tracer gas tests were performed in conjunction with
the second round of indoor air sampling. Pure sulfur
hexafluoride (SF6) was introduced into the sub-slab at
a rate of 0.0025 L/min for about 24 hours prior to
sampling to verify that vapor intrusion was occurring.
No attempt was made to measure the average sub-
slab concentration of SF6. Pure helium was released
within the building at a rate of 3 L/min for about 24
hours prior to sampling to measure the air exchange
rate for the building. During the tracer tests, air
mixing within the building space was enhanced using
two box fans. Rotometers were used during the
August sampling event to control the rate of tracer
gas releases. The multipoint calibrations of the
rotometers using NIST-traceable flow devices were
completed at the URS Austin laboratory, prior to
deployment to the field. Using these calibration data,
gas flows were calculated.
A grab sample was collected prior to the release of
any tracer gases to document the background levels
of SF6 and He within the building. A two-hour time-
integrated indoor air sample was collected
approximately 24 hours after the tracer releases were
started. Three additional grab samples were collected
at hourly intervals after the time-integrated sample
was collected to look at short-term temporal
variability.
3.4 Analytical Procedures
The analytical methods used in this study are
summarized in Table 3-5. During the first phase of
work, groundwater, soil, and soil-gas samples were
analyzed on-site using EPA Method 8265, direct
sampling ion trap mass spectrometry (DSITMS)(US
EPA, 2002). The on-site analyses were performed by
Dr. William Davis of Tri-Corders (http://www.tri-
corders.com/).
Groundwater, confirmatory soil samples, and waste
samples were analyzed for VOCs by SW-846 Method
8260 at Kemron's analytical laboratory in Marietta,
Ohio. In addition, groundwater samples were
analyzed by Kemron for monitored natural
attenuation (MNA) parameters: chloride, nitrate,
sulfate, ferrous ion, and methane, ethane, and ethene.
Field personnel measured dissolved oxygen, redox
potential, etc. of groundwater samples in the field
using an YSI 55 MPS instrument or equivalent.
Soil gas and air samples were analyzed off-site at Air
Toxics Ltd's analytical laboratory in Folsom, CA.
VOCs were determined by US EPA Method TO-15
(US EPA, 1999). Soil-gas samples were analyzed in
full-scan mode. The indoor air and ambient air
samples were analyzed by Selective Ion Mode (SIM)
to achieve better analytical sensitivity. The primary
compound of interest was PCE, which is a widely-
used dry cleaning solvent. The common degradation
products of PCE also were included as target
analytes: TCE, DCE, and VC.
Helium was analyzed by ASTM Method D-1946; the
reporting limit was approximately 0.01%. SF6 was
analyzed by gas chromatography with an electron
capture detector (GC-ECD). The reporting limit for
SF6 was approximately 0.2 ppbv.
One atmosphere (atm) = 1013 millibars (mbar) = 101,300
Pascals (Pa) = 29.9 inches of mercury (in. Hg) = 1033
centimeters of water (cm H2O) = 760 Torr. One Pa = 10
g/cm-sec2 = 0.010 cm H2O = 0.0040 in. H2O.
15
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3.5 Sample Handling and Chain of
Custody Procedures
Similar handling procedures were employed for both
the liquid and indoor air samples. Upon completion
of the collection of each field sample, the samples
were labeled with the following information:
• ID number;
• Project name
• Sampling location;
• Sampler; and
• Date & time of sample collection.
The samples were logged into a field notebook. At
the end of the sampling effort, the samples were
packed and shipped to the off-site analytical
laboratory. All samples submitted to the laboratory
were documented on a chain-of-custody form that
accompanied the shipment of samples from the field
to the lab. The samples and other field
documentation records were shipped by FedEx
overnight service.
Groundwater and Soil Extract Samples
Sample containers were completely filled with
minimal air-filled headspace. Samples were stored
and shipped at approximately 4°C.
Air Samples
Canister pressures were checked in the field prior to
sampling. Post-sampling pressures also were
checked. Canister samples do not require
refrigeration or any special handling techniques
during shipping, but the canister valves must be
securely closed (finger-tight only), Swagelok plugs
firmly attached, and the canisters packed in shipping
crates provided by the laboratory.
Sample identification for canister samples followed
this general protocol:
GP-IAX-MMDDYY-R-001
Where:
GP
XXX
MMDDYY =
R
001
identifies the project as the
Grand Plaza site;
identifies the sampling location
(e.g., IA-1);
Month, Day, Year;
Sample type—R for routine; and
Sequential sample number.
Table 3-5. Summary of Sampling and Analytical Methods for VOCs
Medium
Groundwater
Soil
Soil-Gas
Air
Analysis
Location
On-Site
Off-Site
On-Site
Off-Site
On-Site
Off-Site
Off-Site
Analyte
VOCs
VOCs
Chloride
Nitrate
Sulfate
Ferrous Ion
Methane, Ethane, Ethene
VOCs
VOCs
VOCs
VOCs
VOCs
SF6 (Tracer Gas)
Helium (Tracer Gas)
Analytical Method
EPA Method 8265 (DSITMS)
EPA Method 8260
SW846 Method 9056
SW846 Method 9056
SW846 Method 9056
SMS 500
RSK175
EPA Method 8265
EPA Method 8260
EPA Method 8265
EPA TO- 15 full-scan
EPATO-15SIMs
GC-ECD
ASTMD-1946
16
-------
SECTION 4
RESULTS
The on-site analytical data for the site
characterization effort are presented below, followed
by the data for the groundwater sampling, the slug
tests, and the vapor intrusion study. A summary of
results for the health & safety and waste
characterization & disposal efforts also is given.
4.1 On-Site Analytical Results for Site
Characterization
4.1.1 Groundwater
The results of the on-site analysis of groundwater
samples are shown in Table 4-1 (all tables are given
at the end of the section). The applicable State
standards are included in the table for comparison
purposes. Groundwater samples were collected at 28
locations. Five samples were collected from within
the building, four of which were collected adjacent to
soil boring ("SB") locations from a previous
investigation. Twenty-three samples were collected
from the sampling array outside the building. Sample
collection was attempted at five additional locations
where bedrock was relatively shallow, but no
groundwater could be obtained at these locations.
The depth to bedrock was measured at all 33
locations where probes were pushed and at the eight
existing monitoring wells. The depth to bedrock is
plotted in Figure 4-1.
4.1.2 Soil
The results of the on-site analysis of soil samples are
shown in Table 4-2. The applicable State standards
are included in the table for comparison purposes. A
total of 77 samples were collected from 15 locations
within or very near the building. Fifty-seven samples
were collected from 11 locations within the building
and 20 samples were collected from four locations
outside the building. The results are shown in Table
4-2. The samples marked "SB" were collected at the
four locations where soil borings were collected
during previous studies at the site. A cross-section of
the site showing sub-surface geological features is
shown in Figure 4-2.
4.1.3 On-Site Soil Gas
The results of the on-site analysis of soil-gas samples
are shown in Table 4-3. Sampling was attempted at
24 locations, but samples were obtained at only 10 of
these locations. The remaining 14 locations had high
resistance to soil-gas flow and no sample could be
obtained. Presumably, this was due to the clayey
nature of the surface soils. In addition to the soil-gas
samples at 5 ft (1.5m) depth, soil-gas samples were
collected at the four sub-slab soil-gas sampling
locations. These data also are shown in Table 4-3.
4.2 Results of Off-Site Analysis of
Groundwater
Groundwater samples were collected from nine of the
ten wells on October 20-21, 2005. No sample could
be obtained from MW-2 due to insufficient water
volume within the well. The samples were analyzed
off-site by EPA Method 8260 for a list of 66 target
compounds. The full analytical reports for the
October VOC groundwater samples are given in
Appendix D. Eight VOCs were detected in one or
more of the samples; these results are summarized in
Table 4-4. The applicable State standards are
included in the table for comparison purposes.
Samples were collected again for VOCs from three of
the groundwater monitoring wells on December 13-
14, 2005. The full analytical reports for the
December VOC groundwater samples are given in
Appendix E. Eleven VOCs were detected in one or
more of the samples; these results are summarized in
Table 4-5.
17
-------
00
-------
Grand Plaza Stopping Cenief
3103 Grand Av*nue
Dallas. T
-------
The groundwater was monitored in the field for pH,
conductivity, and various other parameters. These
results are given in Table 4-6. The groundwater
samples collected in October also were analyzed for
monitored natural attenuation (MNA) parameters.
The MNA results are given in Appendix D and
summarized in Table 4-7.
The groundwater sample collected in October from
MW-9 was analyzed for various elements and for
semi-volatile organic compounds (SVOCs). These
results are given in Appendix D and summarized in
Table 4-8.
4.3 Results of Slug Tests
Tests were performed at three wells (MW-7, MW-9,
and MW-10) to estimate hydraulic conductivity. The
results are given in Appendix F.
4.4 Evaluation of Vapor Intrusion
4.4.1 Off-Site Analysis of Soil-Gas
Shallow soil-gas samples were collected from a depth
of 5 ft (1.5m) bgs at six locations: two locations just
outside the building and four locations beneath the
building. Sub-slab soil-gas samples were collected at
three locations. Sampling was attempted at a fourth
sub-slab location (SSI), but no sample could be
obtained. A duplicate sample (i.e., sequential
duplicate) was collected at location SS3.
The results for selected compounds are shown in
Table 4-9. The full analytical reports for the off-site
analysis of soil-gas samples are given as Appendix G.
Each sub-slab sample was collected in close
proximity to a shallow soil-gas sample. The
comparison of the shallow and sub-slab soil-gas data
is shown in Table 4-10.
4.4.2 Off-Site Analysis of Indoor and
Ambient Air Samples
Two indoor air samples and one outdoor ambient air
sample were collected during April 2005. The full
analytical reports for the off-site analysis of these air
samples are given as Appendix H. The results for
these samples are summarized in Table 4-11.
Additional indoor air samples were collected during
August 2005 to further evaluate vapor intrusion. The
full analytical reports for the off-site analysis of these
air samples are given as Appendix I. The results for
these samples are summarized in Tables 4-12 and
4-13. Sample GP-101 was collected prior to the
release of any tracer gas to determine the background
levels of the tracer gases in the indoor air. The
remaining samples were collected after the tracer
gases had been continuously released for the previous
24 hours.
4.4.3 Design of Control System
The site inspection report from the design engineer is
given as Appendix J. The specifications for the
control system are given in Section 6.0.
4.5 Health & Safety
There were no OSHA recordable injuries for this
project. There were no reports of near misses or
minor injuries requiring First Aid. There were no
incidents where drilling breached underground utility
lines.
4.6 Waste Disposal
Samples of waste liquid and soil were collected by
URS personnel and analyzed by the same off-site
laboratory that analyzed groundwater and soil
samples. All materials were found to be non-
hazardous. Wastes were transported and disposed of
by Environmental Industries, LP of Piano, Texas.
4.7 Results of Quality Control (QC)
Checks
Duplicate groundwater samples from seven locations
were analyzed on-site. These results are shown in
Table 4-14.
Duplicate soil samples for two depths at one location
were analyzed on-site. These results are shown in
Table 4-15. Aliquots of the water extracts for three
soil samples were analyzed by the off-site laboratory
for confirmatory purposes. The full analytical report
for these analyses is included as Appendix K. The
comparison of the on-site and off-site analytical
results is shown in Table 4-16.
Soil gas samples from seven locations were analyzed
both on-site and off-site. The comparison of the
analytical results for PCE is shown in Table 4-17.
The results for QC samples for the groundwater
sampling are given in Tables 4-18 and 4-19. The full
analytical reports for these samples may be found in
Appendices D and E.
20
-------
Table 4-1. Results of On-Site Analysis of Groundwater Samples
Sampling Location
Concentration (ng/L)
PCE
TCE
DCE
Vinyl Chloride
Benzene
Toluene
Sampling Array Outside the Building
A2
A3
A4
A5
A9
Bl
C2
Dl
D2
D5
E4
F3
F7
G2
G4
G5
H2
H3
H4
H5
H7
H9
Hll
1.4
7.5
62
<5.4
<5.4
<2.9
89.5
<2.9
67.2
<2.8
135
40
<5.4
2.9
15.3
68.3
<5.4
37.9
2
2.8
<2.8
9.9
1.1
<3.9
1.4
12
<3.9
<3.9
<1.5
32.7
<1.5
13
<2.9
19.3
0.8
<3.9
<2.9
<1.5
7.6
<3.9
4
<1.5
<3.9
<2.9
1.6
1
3.9
4.2
85.3
<2
<2
<4.4
146
<4.4
30.6
<3.9
87.2
3.6
<2
<3.9
<4.4
40.2
<2
15.1
<4.4
3.2
<3.9
7.3
<3.9
<2
<4
<4
<2
<2
<4.4
<4
<4.4
<4
<4
<4.4
<4.4
<2
<4
<4.4
<4.4
<2
<4
<4.4
<2
<4
<2
<4
<2.7
<2.7
<2.7
<2.7
<2.7
<3.1
<2.7
<3.1
<2.7
<2.7
<3.1
<3.1
<2.7
<2.7
<3.1
<3.1
<2.7
<2.7
<3.1
<2.7
<2.7
<2.7
<2.7
<3.1
<3.6
<3.6
<3.1
<3.1
<3.1
<3.6
<3.1
<3.6
<3.6
<3.1
<3.1
<3.1
<3.6
<3.1
<3.1
<3.1
<3.6
<3.1
<3.1
<3.6
<3.1
<3.6
Additional Locations Within Building
03
SB01
SB02
SB03
SB04
155
8.9
15.8
130
15.3
37.6
2.9
5.3
21.7
1
364
124
176
119
19.2
<4.4
<2
<2
<2
<4
<3.1
<2.7
<2.7
<2.7
<2.7
<3.1
<3.1
<3.1
<3.1
<3.6
Regulatory Standards"
TCEQ PCLs
550,000
270,000
14,000,000 (cis)
6,100
85,000
11,000,000
a Texas Risk Reduction Program (TRRP) Tier 1 Protective Concentration Levels (PCLs) for the inhalation pathway at a 0.5-acre source area, commercial
setting (AirGWinh_v).
-------
Table 4-2. Results of On-Site Analysis of Soil Samples
Sampling Location
Concentration (|o,g/Kg)
PCE
TCE
DCE
Vinyl Chloride
Benzene
Toluene
Sampling Array Outside the Building
B2 - 1 ft
B2 - 5 ft
B2 - 10 ft
B2 - 15 ft
B2 - 20 ft
D2 - 1 ft
D2 - 5 ft
D2 - 10 ft
D2 - 15 ft
D2 - 20 ft
D3 - 5 ft
D3 - 10 ft
D3 - 15 ft
D3 - 17 ft
D3 - 20 ft
D4 - 1 ft
D4 - 5 ft
D4 - 10 ft
D4 - 15 ft
D4 - 20 ft
<10.8
<10.8
29.9
37.4
14.5
<11.9
0.0
95.9
122
102
<10.8
10.7
316
14.4
160
<10.8
<10.8
170
46.7
88.1
<11.2
<11.2
<11.2
5.5
<11.2
<6.2
6.7
22.9
10.8
<6.2
<11.2
34.4
52.8
0.0
14.9
<11.2
<11.2
15.6
22.8
7.6
<14.7
<14.7
<14.7
<14.7
<14.7
<17.6
81.7
45.8
50.2
<17.6
130
52.3
0.0
0.0
45.3
<14.7
<14.7
<14.7
<14.7
<14.7
<15.2
<15.2
<15.2
<15.2
<15.2
<17.9
<17.9
<17.9
<17.9
<17.9
<15.2
<15.2
<15.2
<15.2
<15.2
<15.2
<15.2
<15.2
<15.2
<15.2
<10.4
<10.4
<10.4
<10.4
<10.4
<12.4
<12.4
<12.4
<12.4
<12.4
<10.4
<10.4
<10.4
<10.4
<10.4
<10.4
<10.4
<10.4
<10.4
<10.4
<13.7
<13.7
<13.7
<13.7
<13.7
<12.6
<12.6
<12.6
<12.6
<12.6
<13.7
<13.7
<13.7
<13.7
<13.7
<13.7
<13.7
<13.7
<13.7
<13.7
to
to
-------
Table 4-2. Results of On-Site Analysis of Soil Samples (continued)
Sampling Location
Concentration (|o,g/Kg)
PCE
TCE
DCE
Vinyl Chloride
Benzene
Toluene
Sampling Locations Within the Building
M3 - 6 ft
M3 - 10 ft
M3 - 13 ft
N2 - 1 ft
N2 - 4 ft
N2 - 9 ft
N2 - 12 ft
N2 - 16 ft
N2 - 23 ft
N2 - 28 ft
N6 - 0.5 ft
N6 - 3 ft
N6 - 6 ft
N6 - 13 ft
O3 - 0.5 ft
O3-3.5ft
03 - 7 ft
O3 - 10 ft
O3 - 16 ft
O3-21ft
O3 - 27.5 ft
O3 -33.5ft
O3 - 38 ft
18.6
122
164
3,440
878
1,200
1,290
603
461
522
<11.9
<11.9
<11.9
52.0
1,770
<10.8
140
291
204
342
114
130
51.6
<6.2
<6.2
2.0
249
77.4
263
220
62.3
28.9
40.7
<6.2
<6.2
<6.2
<6.2
100
<11.2
102
70.6
32.4
38.5
16.4
18.6
<11.2
155
261
223
2,670
6,390
2,090
1,630
654
429
449
<17.6
<17.6
<17.6
18.3
<14.7
275
818
509
285
318
161
190
26.9
<17.9
<17.9
<17.9
<17.9
<17.9
<17.9
<17.9
<17.9
<17.9
<17.9
<17.9
<17.9
<17.9
<17.9
<15.2
<15.2
<15.2
<15.2
<15.2
<15.2
<15.2
<15.2
<15.2
<12.4
<12.4
<12.4
<12.4
<12.4
<12.4
<12.4
<12.4
<12.4
<12.4
<12.4
<12.4
<12.4
<12.4
<10.4
<10.4
<10.4
<10.4
<10.4
<10.4
<10.4
<10.4
<10.4
<12.6
<12.6
<12.6
<12.6
<12.6
<12.6
<12.6
<12.6
<12.6
<12.6
<12.6
<12.6
<12.6
<12.6
<13.7
<13.7
<13.7
<13.7
<13.7
<13.7
<13.7
<13.7
<13.7
to
-------
Table 4-2. Results of On-Site Analysis of Soil Samples (continued)
Sampling Location
Concentration (|o,g/Kg)
PCE
TCE
DCE
Vinyl Chloride
Benzene
Toluene
Sampling Locations Within the Building (contd.)
PI - 0.5 ft
PI - 1 ft
PI -4 ft
PI - 7.5 ft
PI -10.5 ft
P4 - 0.5 ft
P4-1.2ft
P4 - 6 ft
P4 - 12.5 ft
P4 - 17.5 ft
P4 - 20.5 ft
Ql - 3 ft
Ql - 9 ft
Ql - 12.5 ft
Ql -18.5ft
Ql-22ft
Ql-25ft
Ql - 27.5 ft
Rl - 0.5 ft
Rl-3.5ft
Rl - 6.5 ft
Rl - 10 ft
Rl - 15 ft
1,540
69.4
219
511
543
387
90.0
38.1
129
174
126
1,100
785
500
336
<11.9
90.2
158
75.6
<11.9
<11.9
<11.9
24.1
190
10.2
30.2
68.0
60.6
24.3
19.5
<11.2
18.2
23.0
14.2
2,320
513
206
73.3
<6.2
<6.2
3.7
<6.2
<6.2
<6.2
<6.2
<6.2
<17.6
269
250
499
524
146
39.4
<14.7
99.9
177
119
1,340
899
659
313
<17.6
59.6
83.7
<17.6
<17.6
<17.6
<17.6
<17.6
<17.9
<17.9
<17.9
<17.9
<17.9
<15.2
<15.2
<15.2
<15.2
<15.2
<15.2
<17.9
<17.9
<17.9
<17.9
<17.9
<17.9
<17.9
<17.9
<17.9
<17.9
<17.9
<17.9
<12.4
<12.4
<12.4
<12.4
<12.4
<10.4
<10.4
<10.4
<10.4
<10.4
<10.4
<12.4
<12.4
<12.4
<12.4
<12.4
<12.4
<12.4
<12.4
<12.4
<12.4
<12.4
<12.4
<12.6
<12.6
<12.6
<12.6
<12.6
<13.7
<13.7
<13.7
<13.7
<13.7
<13.7
<12.6
<12.6
<12.6
<12.6
<12.6
<12.6
<12.6
<12.6
<12.6
<12.6
<12.6
<12.6
to
-------
Table 4-2. Results of On-Site Analysis of Soil Samples (continued)
Sampling Location
Concentration (|o,g/Kg)
PCE
TCE
DCE
Vinyl Chloride
Benzene
Toluene
Sampling Locations Within the Building (contd.)
R2 - 0.5 ft
R2 - 3 ft
R2 - 9 ft
R2 - 15.5 ft
R2 - 20.5 ft
R2 - 22.5 ft
R5 - 1 ft
R5 - 6 ft
SB3 - 3 ft
SB3 - 6 ft
SB3 - 10 ft
870
<10.8
37.7
255
51.8
39.2
<11.9
17.7
<11.9
58.1
71.9
134
<11.2
<11.2
33.8
9.6
6.5
<6.2
9.5
<6.2
3.5
6.6
<14.7
<14.7
63.7
142
44.1
28.6
<17.6
13.0
<17.6
19.5
26.7
<15.2
<15.2
<15.2
<15.2
<15.2
<15.2
<17.9
<17.9
<17.9
<17.9
<17.9
<10.4
<10.4
<10.4
<10.4
<10.4
<10.4
<12.4
<12.4
<12.4
<12.4
<12.4
<13.7
<13.7
<13.7
<13.7
<13.7
<13.7
<12.6
<12.6
<12.6
<12.6
<12.6
Regulatory Standards"
TCEQ PCLs
1,000,000
350,000
17,000,000
68,000
77,000
110,000,000
to
a Texas Risk Reduction Program (TRRP) Tier 1 Protective Concentration Levels (PCLs) for the inhalation pathway at a 0.5-acre source area, commercial
setting (
-------
Table 4-3. Results of On-Site Analysis of Soil-Gas Samples
Sampling Location
Concentration (ppbv)
PCE
TCE
DCE
Vinyl Chloride
Benzene
Toluene
Soil-Gas Samples at 5 ft bgsa
C-2
D-3
D-4
D-8
M-3
P-4
Q-l
R-l
R-2
<0.3
<0.4
0.2
<0.3
11
3.8
60
<1
160
<0.4
<0.6
0.2
0.4
0.6
O.4
O.4
<1
0.4
O.5
O.8
0.2
0.5
0.8
O.5
O.5
<2
0.5
O.8
<1
0.4
0.8
<1
O.8
O.8
<3
0.8
O.6
O.9
0.3
0.6
0.9
O.6
O.6
<2
0.6
O.5
O.8
0.3
0.5
0.8
O.5
O.5
<2
0.5
Sub-Slab Soil-Gas Samples'1
SS-1
SS-1BC
SS-3
SS-3 dup
SS-3 dup
SS-3 dup
SS-4
3,700
4,200
140
120
88
100
35
0.6
O.4
O.4
O.4
0.4
0.4
0.2
0.8
O.5
O.5
O.5
0.5
0.5
0.2
<1
O.8
O.8
O.8
0.8
0.8
0.4
0.9
O.6
O.6
O.6
0.6
0.6
0.3
0.8
O.5
O.5
O.5
0.5
0.5
0.3
to
a No sample was obtained at the following locations due to high vacuum/no flow in the sampling system: B2, D2, D5, D6, E8, F3, H8, Ml, N4, N6, O3, P6,
Q3, andR5.
b No sample was obtained at location SS-2 due to high vacuum/no flow in the sampling system.
c Location SS-1B was 2 ft from location SS-1
-------
Table 4-4. Results of Off-Site Analysis of Groundwater Samples Collected in October 2005
Sampling
Location
MW-1
MW-2
MW-3
MW-4
MW-5
MW-6
MW-7
MW-8
MW-9
MW-10
Measured Concentration (|4.g/L)
PCE
184
~
4.64
105
25.4
83.3
9.57
12.8
1.15
16.0
TCE
22.2
~
2.16
11.5
3.61
25.0
1.77
1.80
4.42
4.49
Cis-l,2-DCE
140
~
1.29
59.0
1.51
45.7
0.271
0.588
0.344
2.81
Trans-1,2-
DCE
ND
~
ND
0.511
ND
0.54
ND
ND
ND
ND
Chloroform
0.95
~
ND
1.20
0.738
0.267
0.889
1.20
0.501
0.505
Methylene
Chloride
ND
~
ND
ND
ND
ND
ND
ND
0.367
ND
1,4-DCB
ND
~
0.374
0.357
0.457
0.229
0.318
0.487
0.659
0.224
Freon 11
ND
~
ND
0.828
0.877
0.385
1.03
0.626
12.5
0.511
Regulatory Standards"
TCEQ PCLs
550,000
270,000
23,000,000
14,000,000
33,000
2,100,000
37,000,000
5,700,000
to
DCB = Dichlorobenzene
DCE = Dichloroethylene
ND = Not Detected
a Texas Risk Reduction Program (TRRP) Tier 1 Protective Concentration Levels (PCLs) for the inhalation pathway at a 0.5-acre source area, commercial
setting (AirGWinh.v).
-------
Table 4-5. Results of Off-Site Analysis of Groundwater Samples Collected in December 2005
Sampling
Location
MW-2
MW-9
MW-10
Measured Concentration (|ig/L)
PCE
408
0.513
21.9
TCE
60.3
3.99
5.18
Cis-l,2-DCE
133
0.421
3.11
Trans-1,2-
DCE
1.04
ND
ND
Chloroform
0.939
0.433
0.524
Methylene
Chloride
ND
ND
ND
1,4-DCB
0.442
0.158
ND
Freon 11
0.389
8.62
0.412
Regulatory Standards1
TCEQ PCLs
550,000
270,000
23,000,000
14,000,000
33,000
2,100,000
37,000,000
5,700,000
to
oo
Sampling
Location
MW-2
MW-9
MW-10
Measured Concentration (ng/L)
Benzene
0.181
ND
ND
Toluene
0.329
ND
ND
1,2-DCA
ND
0.370
ND
Acetone
8.48
ND
ND
Regulatory Standards"
TCEQ PCLs
85,000
110,000,000
55,000
350,000,000
DCA = Dichloroethane
DCB = Dichlorobenzene
DCE = Dichloroethylene
ND = Not Detected
a Texas Risk Reduction Program (TRRP) Tier 1 Protective Concentration Levels (PCLs) for the inhalation pathway at a 0.5-acre source area, commercial
setting (AirGWinh_v).
-------
Table 4-6. Results of On-Site Monitoring of Groundwater Samples Collected in October 2005
Sampling
Location
MW-1
MW-2
MW-3
MW-4
MW-5
MW-6
MW-7
MW-8
MW-9
MW-10
Last Reading in Series Take at Each Well
pH
6.9
~
7.0
6.9
6.9
7.0
6.9
6.9
7.2
7.0
Temperature
(°C)
24
~
26
22
26
24
25
22
22
25
Conductivity
(US/cm)
12
-
11
12
12
11
11
12
10
11
Dissolved O2
(mg/L)
1.0
~
0.3
0.7
0.6
0.2
2.1
0.5
0.2
0.3
ORP
(mV)
47
~
149
52
160
-138
75
77
-83
-149
TDS
(g/L)
7.7
~
7.3
7.6
7.7
7.0
7.3
7.5
6.4
7.5
Depth to Water
(ft)
28.9
~
31.7
29.2
33.1
33.9
32.2
30.6
31.0
33.7
to
VO
O2 = Oxygen
ORP = Oxidation reduction potential
TDS = Total dissolved solids
-------
Table 4-7. Results of Off-Site Monitoring of Groundwater Samples for MNA Parameters
Sampling
Location
MW-1
MW-2
MW-3
MW-1
MW-5
MW-6
MW-7
MW-8
MW-9
MW-10
Chloride
(mg/L)
50.5
~
44.9
50.8
45.3
47.2
51.4
52.2
49.3
50.5
Nitrate
(mg/L)
5.46
~
3.02
5.28
5.30
1.40
5.73
5.06
3.10
3.89
Sulfate
(mg/L)
103
~
94.6
104
105
90.4
98.6
103
60.8
95.5
Iron
(mg/L)
0.0273
-
0.205
0.0434
0.0365
0.194
0.04
0.02
3.10
0.071
Methane
(Hg/L)
1.22
~
159
0.482
396
89.4
0.707
0.458
70.4
19.8
Ethane
(Hg/L)
0.25
~
0.25
0.25
O.25
O.25
O.25
0.25
0.25
0.25
Ethene
(Hg/L)
0.25
~
0.519
0.25
1.94
0.492
O.25
0.25
1.90
0.25
Table 4-8. Results of Off-Site Monitoring of MW-9 Sample for Selected Parameters
Analyte
Silver
Arsenic
Barium
Cadmium
Chromium
Copper
Lead
Selenium
Zinc
Mercury
SVOCs
MW-9 Result
(mg/L)
O.005
0.0405
0.311
0.0025
0.0182
0.00522
0.00983
O.005
0.0243
0.0001
ND
U.S. EPA MCL
(mg/L)
0.10
0.010
2
0.005
0.1
1.3
0.015
0.05
5
0.002
-
Comment
No EPA MCL. Value shown is secondary standard.
Measured value exceeds the MCL for drinking water
No EPA MCL. Value shown is secondary standard.
Non-detect for all 65 target compounds. Typical DL was 2.6 |J.g/L.
-------
Table 4-9. Results of Off-Site Analysis of Soil-Gas Samples Collected in April 2005
Sampling Location
Concentration (ppbv)
PCE
TCE
Cis-l,2-DCE
Vinyl Chloride
Benzene
Toluene
Shallow Soil-Gas
D3 - 5 ft
D4 - 5 ft
N4 - 5 ft
P4 - 5 ft
Ql - 5 ft
R2 - 5 ft
39
50
<130
180
780
710
27
18
<130
20
670
100
520
45
29,000
170
1,400
1,200
13
3.8
10,000
69
98
1,500
<4.5
3.0
<130
1.2
<4.3
<7.8
13
5.5
<130
4.6
<4.3
<7.8
Sub-Slab Soil-Gas
SS-2
SS-3
SS-3 dup
SS-4
3,900
2,600,000
2,200,000
8,600
530
170,000
140,000
1,100
860
340,000
290,000
310
<18
<1 1,000
<9,800
<41
<18
<1 1,000
<9,800
<41
<18
<1 1,000
<9,800
500
Table 4-10. Comparison of Results for Shallow and Sub-Slab Soil-Gas Samples Collected in April 2005
Sampling Location
N4 - 5 ft
SS-2
Ql - 5 ft
SS-3
R2 - 5 ft
SS-4
Concentration (ppbv)
PCE
<130
3,900
780
2,600,000
710
8,600
TCE
<130
530
670
170,000
100
1,100
Cis-l,2-DCE
29,000
860
1,400
340,000
1,200
310
Vinyl Chloride
10,000
<18
98
<1 1,000
1,500
<41
Benzene
<130
<18
<4.3
<1 1,000
<7.8
<41
Toluene
<130
<18
<4.3
<1 1,000
<7.8
500
-------
Table 4-11. Results of Off-Site VOC Analysis of Indoor Air and Ambient Air Samples for April 2005
Sampling Location
Indoor - 1
(Restaurant)
Indoor - 2 (Dining
Area)
Ambient Air
Concentration (ppbv)
PCE
13
10
0.11
TCE
0.65
0.52
0.036
Cis-l,2-DCE
1.6
1.1
0.036
Vinyl Chloride
O.019
O.018
0.018
Trans-l,2-DCE
O.019
O.018
0.018
1,1-DCE
O.019
O.018
0.018
Note: All samples were two-hour integrated samples.
Table 4-12. Results of Off-Site VOC Analysis of Indoor Air Samples for August 2005
Sample ID
GP-104
GP-105
GP-106
Concentration (ppbv)
PCE
3.7
16
14
TCE
0.16
0.67
0.64
Cis-l,2-DCE
0.26
1.2
1.1
Vinyl Chloride
O.014
O.014
O.020
Trans-l,2-DCE
O.014
O.014
O.020
1,1-DCE
O.014
O.014
O.020
oo
to
-------
Table 4-13. Results of Off-Site Tracer Gas Analysis of Indoor Air Samples for August 2005
Sample ID
GP-101
GP-102
GP-103
GP-104
GP-105
GP-106
Sampling Date
Aug29
AugSO
AugSO
AugSO
AugSO
AugSO
Sampling Time
0815-0816
0829-0830
0827- 1027
1129- 1130
1255- 1256
1405 - 1408
Helium
(%)
<0.014
0.057
<0.020
<0.014
0.033
0.033
SF6
(ppbv)
<0.27
0.78
0.57
0.55
1.3
2.4
Table 4-14. Results of On-Site Duplicate Analysis of Groundwater Samples
Sampling Location
A2
A2Dup
A3
A3Dup
G5
G5Dup
H9
H9Dup
SB01
SB01 Dup
SB03
SB03 Dup
SB04
SB04 Dup
Concentration (u.g/L)
PCE
1.4
<5.4
7.5
7.2
68.3
81.1
9.9
5.5
8.9
7.5
130
114
15.3
12.3
TCE
<3.9
<3.9
1.4
2
7.6
10.7
1.6
<3.9
2.9
4.2
21.7
20.5
1
1.5
DCE
3.9
2.5
4.2
4.3
40.2
49.9
7.3
3.6
124
143
119
105
19.2
18.7
Vinyl Chloride
<2
<2
<4
<4
<4.4
<4.4
<2
<2
<2
<2
<2
<2
<4
<4
Benzene
<2.7
<2.7
<2.7
<2.7
<3.1
<3.1
<2.7
<2.7
<2.7
<2.7
<2.7
<2.7
<2.7
<2.7
Toluene
<3.1
<3.1
<3.6
<3.6
<3.1
<3.1
<3.1
<3.1
<3.1
<3.1
<3.1
<3.1
<3.6
<3.6
-------
Table 4-15. Results of On-Site Duplicate Analysis of Soil Samples
Sampling Location
Rl - 0.5 ft
Rl-0.5ftdup
Rl - 15 ft
Rl-15ftdup
Concentration (jag/Kg)
PCE
75.6
47.6
24.1
40.8
TCE
<6.2
<6.2
<6.2
<6.2
DCE
<17.6
<17.6
<17.6
<17.6
Vinyl Chloride
<17.9
<17.9
<17.9
<17.9
Benzene
<12.4
<12.4
<12.4
<12.4
Toluene
<12.6
<12.6
<12.6
<12.6
Table 4-16. Comparison of On-Site and Off-Site Analysis of Soil Samples
Sampling
Location
SB3 - 10 ft
SB3 - 10 ft
SB3 - 10 ft dup
R5 - 1 ft
R5 - 1 ft
Rl-0.5ft
Rl- 0.5 ft dup
Rl-0.5ft
Laboratory
On-site
Off-site
Off-site
RPD
On-site
Off-site
On-site
On-site
Off-site
RPD
Concentration (jig/Kg)
PCE
71.9
58.8
59.5
-22.4%
<11.9
<11
75.6
47.6
50.6
-21.7%
TCE
6.6
10.8
<11
39.1%
<6.2
<11
<6.2
<6.2
<11
DCE
26.7
13.8
10.0
-93.6%
<17.6
<11
<17.6
<17.6
<11
Vinyl Chloride
<17.9
<11
<11
<17.9
<11
<17.9
<17.9
<11
Benzene
<12.4
<5
<5
<12.4
<5
<12.4
<12.4
<5
Toluene
<12.6
<11
<11
<12.6
<11
<12.6
<12.6
<11
-------
Table 4-17. Comparison of On-Site and Off-Site Analysis of Soil-Gas Samples
Sampling
Location
D3 - 5 ft
D3 - 5 ft
D4 - 5 ft
D4 - 5 ft
P4 - 5 ft
P4 - 5 ft
Ql - 5 ft
Ql - 5 ft
R2-5ft
R2 - 5 ft
SS3 - subslab
SS3 - subslab
SS4 - subslab
SS4 - subslab
Laboratory
On-site
Off-site
RPD
On-site
Off-site
RPD
On-site
Off-site
RPD
On-site
Off-site
RPD
On-site
Off-site
RPD
On-site
Off-site
RPD
On-site
Off-site
RPD
Concentration (|o,g/m3)
PCE
<0.4
39
NC
O.2
50
NC
3.8
180
99%
60
780
92%
160
710
77%
140
2,600,000
100%
35
8,600
100%
TCE
0.6
27
NC
O.2
18
NC
0.4
20
NC
0.4
670
NC
O.4
100
NC
0.4
170,000
NC
0.2
1,100
NC
DCE
0.8
520
NC
O.2
45
NC
0.5
170
NC
0.5
1,400
NC
O.5
1,200
NC
0.5
340,000
NC
0.2
310
NC
Vinyl Chloride
<1
13
NC
O.4
3.8
NC
0.8
69
NC
0.8
98
NC
O.8
1,500
NC
0.8
<1 1,000
NC
0.4
<41
NC
Benzene
0.9
<4.5
NC
O.3
3.0
NC
0.6
1.2
NC
0.6
<4.3
NC
O.6
<7.8
NC
0.6
<1 1,000
NC
0.3
<41
NC
Toluene
0.8
13
NC
O.3
5.5
NC
0.5
4.6
NC
0.5
<4.3
NC
O.5
<7.8
NC
0.5
<1 1,000
NC
0.3
500
NC
NC = Not calculated
-------
Table 4-18. Results of Off-Site VOC Analysis of Groundwater QC Samples
Sampling
Location
Measured Concentration (|4.g/L)
PCE
TCE
Cis-l,2-DCE
Trans-1,2-
DCE
Chloroform
Methylene
Chloride
1,4-DCB
Freon 11
October 2005 Sampling Event
MW-4
MW-4 dup
Trip Blank
Equipment
Blank3
105
101
ND
0.68
11.5
10.9
ND
0.292
59.0
55.7
ND
ND
0.511
0.415
ND
ND
1.20
1.19
ND
ND
ND
ND
ND
ND
0.357
0.358
ND
ND
0.828
0.868
ND
ND
December 2005 Sampling Event
MW-9b
MW-9 dupb
Trip Blank
0.513
0.475
ND
3.99
3.82
ND
0.421
0.468
ND
ND
ND
ND
0.433
0.468
ND
ND
ND
0.346
0.158
0.209
ND
8.62
7.90
ND
DCB = Dichlorobenzene
DCE = Dichloroethylene
ND = Not Detected
a Carbon disulfide also was detected in the equipment blank at 0.917 |ag/L.
b Samples also contained 1,2-dichloroethane at 0.370 and 0.404 (dup) M-g/L.
Table 4-19. Results of Off-Site Analysis of Groundwater QC Samples for MNA Parameters
Sampling
Location
MW-4
MW-4 dup
Chloride
(mg/L)
50.8
51.2
Nitrate
(mg/L)
5.28
5.08
Sulfate
(mg/L)
104
103
Iron
(mg/L)
0.0434
0.0342
Methane
(Hg/L)
0.482
0.565
Ethane
(Kig/L)
O.25
<0.25
Ethene
(Kig/L)
O.25
O.25
-------
SECTION 5
DISCUSSION OF RESULTS
Site characterization results are discussed below,
followed by an evaluation of vapor intrusion for this
site. Review of the analytical data sets indicates that
the systems were within control and that the internal
quality control checks performed by each laboratory
generally were acceptable. The data are considered
to be valid and defensible, with the possible
exception of the on-site soil-gas data, as discussed
later in this section.
5.1 Site Characterization
Groundwater, soil, and soil-gas samples were
collected to characterize the current levels of
contamination at the site. These results are discussed
below.
The depth to bedrock was obtained for all 33
locations where probes were pushed plus the eight
existing monitoring wells. The results are depicted in
Figure 4-1. The depth to bedrock drops from roughly
35 ft (llm) bgs along Grand Avenue to >70 ft (21m)
bgs behind the building. No depths greater than 70 ft
(21m) could be obtained using the available direct-
push equipment and this limited the ability to
delineate the bedrock for most of Row "A."
5.1.1 Groundwater
The on-site analytical results for groundwater data
are plotted for PCE, TCE, and DCE in Figures 5-1,
5-2, and 5-3, respectively. The on-site analytical
method could not distinguish between the cis- and
trans- forms of DCE. The plots show that the highest
concentrations of the target VOCs lie directly beneath
the 60 ft by 70 ft (18 by 21m) southwest end of the
strip mall, where the dry cleaner facility once
operated. Some contamination has migrated towards
Grand Avenue (e.g., locations G5 and H2). There
also is some evidence of contamination behind the
building (see data for location A4).
All VOC concentrations beneath the building are
<0.4 ppm, while all concentrations outside the
building are <0.1 ppm. All measured VOC
concentrations are far below applicable state
standards. The data indicate that the PCE has
undergone substantial degradation to TCE and DCE,
but no vinyl chloride was detected. In addition,
benzene and toluene were not detected. Duplicate
samples were analyzed on-site for seven locations.
The results generally are within +25% and are almost
always within a factor of 2x.
The results for PCE and TCE for the last four rounds
of groundwater monitoring (i.e., July 2003-
December 2005) are shown in Table 5-1. The results
indicate that the groundwater concentrations at the
site generally are stable. Seven of the wells had very
similar concentrations from sampling event to
sampling event. The highest variability in sequential
results occurred at MW-4, where TCE and PCE
concentrations varied by as much as an order of
magnitude. MW-6 and MW-7 also exhibited
variability to some extent. PCE and TCE
concentrations showed a gradual increase over three
sampling events at MW-1.
The productivity of the shallow groundwater zone at
Grand Plaza was evaluated at site monitoring wells
using two methods: slug tests and a constant
discharge test. Data from slug tests at two wells
(MW-7 and MW-9) were used to estimate hydraulic
conductivity values, which were subsequently
converted into well yield values expressed in gallons
per day (gpd). The constant discharge test
(conducted at MW-10) allowed a direct measurement
of minimum well yield, which was compared to the
slug test results.
The tests were performed in accordance with state
regulatory guidance (TCEQ, 2003), and duplicating
select methodologies described by Butler, et. al.
37
-------
oo
-------
VO
-------
-------
Table 5-1. PCE and TCE in Groundwater Over Time
Sampling
Location
MW-1
MW-2
MW-3
MW-4
MW-5
MW-6
MW-7
MW-8
MW-9
MW-10
Tetrachloroethylene (|J.g/L)
Dec 2005
~
408
~
~
~
~
~
~
0.513
21.9
Oct 2005
184
~
4.64
105
25.4
83.3
9.57
12.8
1.15
16.0
May 2004
160
710
4.4
430
28
15
6.0
6.30
~
-
July 2003
144
767
4.22
35.5
26.3
~
~
~
~
-
Trichloroethylene (|J.g/L)
Dec 2005
~
60.3
~
~
~
~
~
~
3.99
5.18
Oct 2005
22.2
~
2.16
11.5
3.61
25.0
1.77
1.80
4.42
4.49
May 2004
18
72
2.1
35
3.2
5.1
1.6
1.5
~
-
July 2003
14.8
76.9
2.37
3.96
3.32
~
~
~
~
-
-" = No sample collected
-------
(1996). Slug tests were performed as many as six
times at each well in order to evaluate the
reproducibility of the data. It was noted, particularly
at MW-7, that "skin effects" within the well sand
filter pack may have evolved during repeated testing,
diminishing well recharge over time. The first two
tests conducted at MW-7 yielded calculated hydraulic
conductivities of approximately 140 and 200 ft/day
(43 and 61 m/day), corresponding to calculated well
yields of approximately 11,000 and 15,000 gal/day
(42,000 and 57,000 L/day). The fifth and final test
yielded a significantly lower calculated hydraulic
conductivity of approximately 6.8 ft/day (2.1 m/day),
corresponding to a calculated well yield of
approximately 660 gpd (2,500 L/day). These
presumed skin effects apparently were not as
significant at MW-9. The first two tests conducted at
MW-9 yielded calculated hydraulic conductivities of
approximately 2.6 and 3.3 ft/day (0.80 and 1.0
m/day) corresponding to calculated well yields of
approximately 16,000 and 20,000 gpd (61,000 and
76,000 L/day). The sixth and final test yielded a
slightly lower calculated hydraulic conductivity of
approximately 2.0 ft/day (0.6 m/day), corresponding
to a calculated well yield of approximately 13,000
gpd (49,000 L/day). Note that calculated well yields
are similar for both wells even though calculated
hydraulic conductivity at MW-7 is two orders of
magnitude greater than at MW-9. This occurs in
calculation as a result of the saturated thickness of the
aquifer at each location. The saturated thickness at
MW-7 is approximately 5 ft (1.5m), versus 44 ft
(13m) at MW-9.
A constant discharge test was conducted at MW-10,
allowing a direct measurement of minimum well
yield. During the test, an electronic water level
indicator was used to measure the water level in
MW-10 while a 12V submersible pump was operated
at its maximum pumping rate, which was
approximately 1 gallon per minute (3.8 L/min).
Upon activation of the pump, 0.3 ft (9 cm) of
drawdown occurred almost instantaneously.
Thereafter, the water level remained constant as the
pump discharged continuously for approximately 18
minutes, until the test was terminated. Extrapolated,
the rate of discharge corresponds to a minimum well
yield of approximately 1,400 gpd (5,300 L/day).
The results of both types of tests demonstrate that site
well yields are significantly greater than 150 gpd
(570 L/day), which is the threshold for Class 2 / Class
3 groundwater designation according to TCEQ
Guidance Document RG-366/TRRP-8 (TCEQ,
2003). Therefore, the shallow groundwater zone at
Grand Plaza is designated Class 2.
5.1.2 Soil
The on-site analytical results for soils are plotted for
PCE in Figures 5-4, 5-5, and 5-6 for depths of 0-1 ft,
1-10 ft, and >10 ft (0-0.3, 0.3-3, and >3m),
respectively. Similar plots are shown in Figures 5-7
through 5-9 for TCE and in Figures 5-10 through
5-12 for DCE. As previously noted, the on-site
analytical method could not distinguish between the
cis- and trans- forms of DCE. The plots indicate that
the areas of higher contamination are relatively
limited in size. Three-dimensional representations of
the data are shown in Figures 5-13, 5-14, and 5-15
for PCE, TCE, and DCE, respectively.
All samples from outside the building were <0.4 ppm
for all VOCs. Contamination was detected in all
borings down to a depth of 20 ft (6m) bgs. Soil
samples collected from beneath the building
contained up to 3.4 ppm of PCE, 2.3 ppm of TCE,
and 6.4 ppm of DCE. All measured VOC
concentrations are far below applicable state
standards. As with the groundwater samples, the data
suggest that degradation of the PCE has occurred.
Vinyl chloride, benzene, and toluene were not
detected in any of the soil samples.
The highest concentrations of target VOCs generally
occur near the surface and the concentrations tend to
decrease below 12 ft (3.7m) bgs. However,
concentrations >0.1 ppm were detected down to 20 ft
(6m) at some locations (e.g., N2, PI, P4, and Ql).
Contamination levels above 1 ppm for individual
compounds are present to depths of at least 12 ft
(3.7m) and contamination levels above 0.5 ppm are
present to depths of at least 28 ft (8.5m)(see data for
N2).
Duplicate samples were analyzed for two depths at
one location. Only PCE was detected in these
samples and the results for the duplicates agree to
within a factor of 2x.
Aliquots of water extracts from three soil samples
were analyzed by an off-site laboratory for
confirmatory purposes. For the four data pairs where
the compounds were detected in both the on-site and
off-site analyses, the average relative percent
difference (RPD) was 44% (based on the absolute
values of the individual RPDs).
42
-------
Legend
II Bysldmg
[1^1) Paved Ar&a
ND N0E Delected
Soil Soring Location
DPT Sample Location
Monitoring Well Location
URS
GWC/AUS
G^and Plaza Shopping Center
3103 Grand Avenue
P.ailas...Texas
Figure 5-4
Soil Isoconcentratson Contours.
(PCE pg/kg 0-1 ft)
Based on April 2005 Data
43
-------
Legend
I 1 Building
I | Paved Area
NO Nol Detected
MS Nol Sampled
Soil Boring Location
DPT Sample Location
Monitoring Well Location
URS
WOO Amoergten BIWj
Auslm TX 78T29
PFione (512)454-4797
Fax 1512)419-5474
GWC/AUS
Grand Plaza Shopping Center
3103 Grand Avenue
Figure 5-5
Soil Isoconcenlralion Contours
(PCEug/kg1-10fl)
Based on April 2005 Dala
44
-------
;
-.-
Leoertd
F 1 Building
[ | Paved Area
NO Not Delected
NS No) Sampled
Soil Boring Location
DPT Sample Location
Monitoring Well Location
URS
94QO Ambprg*n Blvd
Ausim TX 78729
Prione (51?) 454-4797
GWC/AUS
Grand Plaza Shopping Center
3103 Grand Avenue
Dallas. Texas
Figure 5-6
Soil IsQconcentration Contours
{PCE Mg/kg>10ft)
Based on April 2005 Data
45
-------
>
Legend
I I Building
I I Paved Area
NO Nol Delected
NS Nol Sampled
Soil Boring Location
DPT Sample Localion
Monitoring Well Location
URS
9400 Ambergfen Btvd
Aosln TX 78729
Phon* (S1J|*54U797
Fax {512)419-5474
GWC/AUS
Grand Plaza Shopping Center
3103 Grand Avenue
Dallas Texas
Figure 5-7
Soil Isoconcentration Contours
(TCE ug*g 0-1 ft)
Based on April 2005 Data
46
-------
Legend
I I Building A Soil Bonng Location
I I Paved Area Jg DPT Sample Localion
NO No! Delected
NS Noi Sampled
•V Monitormg Well Location
URS
9400 Am&ergten SW
Auslm TX 78729
Phone )51?|4&4J79
F»X (512)419-5474
GWC/AUS
Grand Plaza Shopping Center
3103 Grand Avenue
Texas
Figure 5-8
Soil Isoconcentralion Contours
(TCEpg/kg 1-10ft)
Based on April 2005 Data
47
-------
Legend
I I Budding A Son Bonng Location
I I Paved Area Jg DPT Sample Location
NO Not Delected ^ .
V Monitoring Well Location
NS Not Sampled
URS
9400 Am&ergten SW
Auslm TX 78729
Phone )51?|4&4J79
F« (512)419-5474
GWC/AUS
Grand Plaza Shopping Center
3103 Grand Avenue
Dallas. Texas
Figure 5-9
Soil laDconcentralion Contours
(TCE M9/kg>10ft)
Based on April 2005 Data
48
-------
Legend
I I Building
I I Paved Ares
NO Not Dsleeled
US Nol Sampled
Soil Bonng Location
DPT Sample Localion
Monitoring Well Location
URS
Bfvd
AuBlm. TX 78729
Phone (512)454-4797
Fax (512|416-S474
GWC/AUS
nd Plaza Shopping Ce
3101 Grand Avn-r
Dallas. Texas
Figure 5-10
Soil IsoconcentraKon Contours
(DCE pg/kg 0-1 ft)
Based on April 2005 Data
49
-------
Legend
I I Building
I I Paved Ares
NO Not Dsleeled
US Nol Sampled
Soil Bonng Location
DPT Sample Localion
Monitoring Well Location
URS
3400 Ambergien E. -1
AuBlm. TX 78729
Phone (512)454-4797
Fax (512)419-5474
GWC/AUS
nd Plaza Shopping Ce
3101 Grand Avn-r
Dallas. Texas
Figure 5-11
Soil tsoconcenlralion Contours
(DCEug/kg1-10ft)
Based on April 2005 Data
50
-------
Legend
I I Building
I I Paved Ares
NO Not Dsleeled
US Nol Sampled
Soil Bonng Location
DPT Sample Localion
Monitoring Well Location
URS
Bfvd
AuBlm. TX 78729
Phone (512)454-4797
Fax (512|416-S474
GWC/AUS
nd Plaza Shopping
3101 Grand Avn-r
Dallas. Texas
Figure 5-12
Soil tsoconcentration Contours
(DCEug/kg>10ft)
Based on April 2005 Data
51
-------
to
100 po^O PCE Isooonoenlratioo
ims
Grand Avenue Plaza
31 CO Grand Avenue
: i •:• ' •• -
Figure 5-13
3d PCE Plume
Based on April 2005
Soil Data
-------
\
Ltatnd
100 ugtojTCE l»c«n««ntia(iflo
'0 ug&o ICE teoc«K«*ation
URS
LflB CfvinBttn
HO) Ajre«^«ri fl?.d
Aunn T.mt JS7JO
Grand Avenue Plaza
31 DO Grand Avenue
: . •:- ' •• -
WTr: S»? ?7, JD06 |nff*h: | J J_[j[ jirra.ii*^
^FlgureTlT
3-D TCE Plume
Based on April 2005
Soil Data
1
-------
\
Ltatnd
1000 ugrttg DCE tnxttK*rtrtt>»
100 M9*9DCE (soMoeentralion
URS
LflB CfvinBttn
HO) Ajre«^«ri Ri.d
Aunn T.mt JS7JO
Grand Avenue Plaza
31 DO Grand Avenue
: . •:- ' •• -
WTr: S»? ?7, JD06 |nff*h: | J J_[j[ jirra.ii*^
^FlgureTl^^
3-D DCE Plume
Based on April 2005
Soil Data
1
-------
5.1.3 On-Site Soil-Gas
Soil-gas samples were obtained at a depth of 5 ft
(1.5m) bgs from 10 locations and analyzed on-site.
In addition to the shallow soil-gas samples, soil-gas
samples were collected at the four sub-slab soil-gas
sampling locations. Only PCE was detected in the
soil-gas samples at 5 ft (1.5m) depth; all other
compounds were non-detect (ND). No PCE was
detected in the soil-gas samples collected outside the
building or in two of the six soil-gas samples at 5 ft
(1.5m) bgs under the building. The highest
concentration was 1,110 |J.g/m3 (7.5 ppmv) at location
R2.
The on-site analysis of the sub-slab soil-gas samples
showed relatively high concentrations of PCE at all
four locations where samples were obtained. All
other compounds were ND. The measured
concentrations for PCE were:
• SSI = 25,300 |ag/m3 (172 ppmv);
• SS1B = 28,200 |ag/m3 (191 ppmv);
• SS3 = 920 |ag/m3 (6.2 ppmv); and
• SS4 = 239 |ag/m3 (1.6 ppmv).
The sub-slab sampling locations are shown in Figure
3-4. On the sampling array, Location SSI was near
N3, in the area where the dry cleaning machines once
were located. Location SS1B was two ft from SSI
and was used after SSI became resistant to flow.
Location SS2 was between N4 and N5 on the
sampling array shown in Figure 3-1. Location SS3
was between P2 and Q2, and Location SS4 was near
S2.
Samples SSI and SS1B were collected sufficiently
close together to be considered duplicate samples.
The RPD for this sample pair is 11%. Four
sequential samples were collected at location SS3 (a
regular sample and three replicates). The replicate
samples showed somewhat lower concentrations than
the regular sample: -8%, -35%, and -23%.
Given the high concentrations that were detected, the
on-site analysis could have relied upon a direct
injection approach rather than the use of sorbent
tubes. The on-site soil-gas data exhibit a consistent
low bias compared with the off-site analytical results.
One possibility is that the sorbent material may have
become saturated with VOCs. Overall, the on-site
soil-gas data are believed to be less accurate than the
on-site groundwater and soil data.
5.2 Evaluation of Vapor Intrusion
The off-site analytical results for soil-gas, indoor air
samples, and tracer gas tests are discussed below,
followed by a discussion of the potential for vapor
intrusion at this site.
5.2.1 Off-Site Analysis of Soil Gas
Shallow soil-gas samples were collected at at a depth
of 5 ft (1.5m) bgs from six locations and three sub-
slab soil-gas samples were collected. The PCE in the
shallow soil gas ranged from 0.039 to 0.71 ppmv.
The TCE concentrations were similar to the PCE
concentrations, whereas the DCE tended to be higher
(up to 29 ppmv). The presence of TCE, DCE, and
VC is additional evidence that the PCE has degraded
in the past.
In addition to the compounds shown in Table 4-9,
one or more of the samples contained hexane, trans-
1,2-DCE, m/p-xylene, or 2,2,4-trimethylpentane.
The amount of trans-l,2-DCE was generally <10% of
the amount of cis-l,2-DCE. The concentration of
2,2,4-trimethylpentane (iso-octane) ranged from 0.14
to 1.7 ppmv in the shallow soil-gas samples.
Gasoline releases are the most likely source of this
compound. Some samples also showed traces of
compounds thought to be laboratory artifacts (i.e.,
ethanol, acetone, or methyl-ethyl ketone [MEK]).
The sub-slab soil-gas data exhibited considerable
spatial variability. For example, two of the three sub-
slab soil-gas samples had PCE concentrations
between 3 and 9 ppmv, whereas the third sample had
2,600 ppmv of PCE (0.26%)(18,000,000 |ag/m3).
This sample was collected from the middle of the
restaurant and also had significant concentrations of
TCE and cis-l,2-DCE. The off-site data for PCE are
consistently higher than the on-site analytical results
for the same location. The off-site data should be
considered more representative of site conditions.
The sub-slab samples were each collected adjacent to
a shallow soil-gas sample. The comparison of the
shallow and sub-slab soil-gas data is shown in Table
4-10. The comparison generally shows that the PCE
concentrations are highest immediately beneath the
slab. The maximum measured values for shallow
soil-gas and sub-slab soil-gas did not coincide
spatially.
No physical barriers to vapor transport were found in
the examination of the building slab based on the
sound checks. Pressure differential measurements
55
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made under induced vacuum indicated that the fill
directly underneath the slab is amenable to vapor
flow. While drilling holes in the slab it was found
that the slab is only about 4 in. (10 cm) thick in
places. Tile floor covering precluded a thorough
examination of the slab for cracks.
Soil gas data at the site indicate that chemical
concentrations vary spatially, decreasing significantly
with distance from a small "hot spot". The data
suggest that the contamination has largely remained
in place under the slab near its release point with only
limited vertical and lateral transport. The lack of gas-
phase lateral migration within the fill material
directly beneath the slab is somewhat surprising,
given the decades of time that the contamination has
been in place and the expected rates of diffusion in
the air-filled pore spaces beneath the slab.
conditions between the two sampling events. As
previously discussed, during the first round of
sampling, the space was unoccupied and the HVAC
system was not in use during the sampling event nor
during the preceding days. During the second round
of sampling, the HVAC system was in regular use.
As shown in Table 4-12, a grab sample was collected
about 24 hours prior to the second round of sampling
at a time when the building HVAC system had been
operating at a high rate overnight. This sample had
only about 25% of the PCE, TCE, and cis-DCE of the
samples detected in the time-integrated samples
collected the following day. This suggests that there
can be significant short-term temporal variability in
indoor VOC concentrations at this site.
5.2.3 Tracer Gas Tests
5.2.2 Off-Site Analysis of Indoor and
Ambient Air Samples
Two indoor air samples and one outdoor ambient air
sample were collected during the first round of
sampling. PCE was detected in the indoor air
samples at concentrations of 10 to 13 ppbv. TCE was
detected at 0.52 to 0.65 ppbv and cis-l,2-DCE was
detected at 1.1 to 1.6 ppbv. The ambient air sample
had low levels of PCE (0.11 ppbv), but the ambient
air does not appear to be a significant source of the
compounds detected in the indoor air samples.
The measured indoor air concentrations may have
been biased high due to two factors. One, the drilling
through the floor in the days preceding air sampling
likely created a pathway for subsurface vapors to
enter the building. The exposed soil cores in the
room also may have been an emissions source. Two,
the HVAC system was not operating for at least 12
hours prior to the start of the indoor air sampling, so
dilution of any emissions would have been minimal.
Based on the results of the initial site
characterization, additional samples were collected to
evaluate the potential for vapor intrusion. As shown
in Tables 4-11 and 4-12, indoor air samples were
collected at two locations during the first round of
sampling and at one location during the second round
of sampling. The results for the two rounds of
sampling showed similar levels of VOCs in the
indoor air.
Overall, PCE was detected in the indoor air at about
12 ppbv (83 |J.g/m3). The agreement among the
indoor air samples is good, despite the difference in
Neither helium nor SF6 was detected in the indoor air
prior to the tracer gas releases. The time-integrated
sample collected 24 hours later had <0.020% helium.
Using equation 3-1 and the helium release rate of
0.18 m3 hr"1, the ventilation rate within the restaurant
portion of the building (QBidg) is estimated to be >900
m3 hr"1. The restaurant area has a footprint of 184 m2
and a volume of 481 m3. Therefore, the building air
exchange rate is estimated to be >1.9 air changes per
hour (ACH).
Four grab samples also were collected after the tracer
gas release was initiated and helium was detected in
three of the four samples, with values ranging from
<0.014% to 0.057%. The variability may be due to
incomplete mixing in the indoor air space as
evidenced by the variability between the helium and
SF6 concentrations. The variability also is thought to
reflect changes in the actual ventilation rate as the
HVAC system and fry-station exhaust hood turned on
and off. The experimental design did not address
measurements of the building ventilation as a
function of exhaust hood use. Real-time
measurements of helium concentration should be
included in any future, similar studies. The average
helium concentration was 0.031% if the detection
limit is substituted for the non-detect values. This
yields a ventilation rate of 573 m3 hr"1 and 1.2 ACH.
The time-integrated measurement of SF6 was 0.57
ppbv and two grab samples collected during the same
time frame had similar results. The detection of SF6
within the building confirms that vapor intrusion is
occurring. Two additional measurements of SF6 were
made after use began of the fry-station exhaust hood.
The hood increased the pressure differential between
56
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the building and soil and thereby is believed to have
increased the rate of QSOii. The threefold increase in
concentration reflects an increase in QsoU of >3, if the
exhaust hood increased the building ventilation rate.
Pressure differential measurements were made to
confirm the effect of the fry-station exhaust hood.
Two holes were drilled through the slab 15 to 30 ft (5
to 10m) from the exhaust hood and the building
pressure differential was measured with the exhaust
hood off and again with the exhaust hood on. The
measurement locations are shown in Figure 3-4. The
use of the exhaust hood changed the building
pressure differential from +0.002 to -0.003 in. H2O at
one location and from +0.001 to -0.006 in. H2O at
the second location. The positive sign indicates that
air flow is from the interior space into the subsoil,
whereas a negative sign indicates that air flow is from
the subsurface. So, the effect of the exhaust fan was
to switch the soil-gas flow from positive to negative.
The magnitude of this effect was about 1.5 Pa. For
comparison, the US EPA guidance assumes a
continuous building pressure differential (AP) of 4 Pa
(EPA, November 2002).
The measurements of pressure differential at the three
sub-slab sampling locations during April 2005 were
all non-detect (<0.005 in. H2O). As previously noted,
the HVAC system and exhaust hood were not in
regular use at the time.
5.2.4 Evaluation of Vapor Intrusion
Vapor intrusion (VI) is the migration of gas-phase
chemicals from the subsurface into buildings or other
structures. It is only in the last few years that vapor
intrusion of VOCs has become a general issue for
sites with subsurface contamination due to petroleum
fuels or chlorinated solvents. Federal guidance has
been published (US EPA, November 2002), as well
as guidance by various State Agencies (Eklund, et al.,
2006).
Vapor intrusion studies typically address the potential
risk from chronic exposure to very low
concentrations of potential carcinogens. It is the
incremental increase in indoor air concentration that
is the issue, not the absolute concentration itself.
Given the typical background levels of VOCs in
houses and office buildings, it often is difficult or
impossible to measure vapor intrusion directly using
indoor air measurements. Therefore, alternative
evaluation approaches are often employed. A
standard modeling approach is available (Johnson and
Ettinger, 1991)(US EPA, 2003b), but there are
concerns that the model may be too conservative for
some scenarios or that the model can be misused.
Most current guidance emphasizes evaluating vapor
intrusion using soil-gas measurements made near the
buildings of interest.
The ratio of indoor air to soil-gas concentrations is
often evaluated in vapor intrusion studies. This ratio
typically is called the attenuation factor or a.
Published values of a tend to be <0.001. In other
words, the soil gas is diluted by a factor of > 1,000
inside a building. The EPA default a value for
screening purposes currently is 0.1, but is expected to
decrease to 0.02 when the 2002 EPA guidance is
revised sometime in 2007.
It is typical practice to use the maximum subsurface
value rather than the mean or median value when
calculating a for a given site. The three sub-slab
soil-gas samples had 18,000,000; 26,000; and 59,000
|ag/m3 of PCE. The three indoor air samples had 85,
68, and 96 |J.g/m3, for a mean of 83 |J.g/m3.
Therefore, a = 5.3xlO"6 using the maximum values
and a = 1.4xlO"5 using the average values. The
values of a for other compounds detected in the sub-
slab soil-gas are also in the 10"6 range using the
maximum values. These results are not
unreasonable. In another study, one of the authors
has measured attenuation coefficients of roughly
IxlO"5 in multiple buildings with decades-old surface
spills and localized high concentrations of
chlorinated solvents in the sub-slab soil gas (Rehage,
et al., 2006).
The sub-slab monitoring locations were biased
towards areas of suspected contamination. So, the
average value calculated from the three sub-slab
measurements is thought to be biased high from the
"true" value. Given the very high degree of
subsurface spatial variability in the concentration of
PCE and other VOCs, the average value is essentially
equal the maximum value divided by the number of
measurements («). Increasing n would likely lead to
a linear decrease in a calculated from average values,
unless a 2nd "hot spot" were found.
The concentration of VOCs in the subsurface should
be relatively stable, whereas the indoor air
concentration was found to vary by about a factor of
4x over a one-day period. Given that a is a simple
ratio of the two, it also would vary by this same
factor of 4x. This short-term temporal variability is
thought to be due to changes in the pressure
57
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differential between the building and the subsurface.
When the exhaust fan in the restaurant is off, there is
little or no pressure-driven airflow of vapors into the
building. When the exhaust fan is on, there is a
driving force for vapor intrusion.
The US EPA and others are compiling data, but there
are relatively few published values for a in the open
literature. Fischer, et al. (1996) measured
hydrocarbons found in gasoline in ambient air, indoor
air, and soil gas at two depths. They report
attenuation coefficients from 4.0xlO~4 to 1.9xlO~3.
They also used an SF6 tracer gas and reported an
attenuation coefficient of 2.5xlO~4 with no forced
pressurization. Olson and Corsi (2001) used an SF6
tracer at two houses in New Jersey and reported
attenuation coefficients ranging from 5.52xlO"5 to
1.7xlO"4. Johnson, et al. (1999) suggested an upper
limit of about IxlO"3 for a. Elsewhere, Johnson
(2002) suggested a reasonable range for a of IxlO"4
to IxlO"2 for screening purposes. Our data show a
lower a than of these published values. This is
significant given that the gas-phase contamination
was present immediately beneath the building slab
and the building slab is relatively thin and old.
The absolute concentrations of PCE measured in this
study are high relative to typical indoor air
concentrations in houses and offices, which are
reported to be 0.14 and 0.47 ppbv, respectively
(Hodgson and Levin, 2003). The measured values
are not high, however, compared with measurements
made in apartments or condominiums located in the
same building as dry cleaners. PCE values up to
197,000 |J.g/m3 have been reported, with median
values well above 1,000 |ag/m3 in several studies (US
EPA, 1998).
The air exchange rate for buildings varies widely.
The US EPA (1997) evaluated data from several
thousand houses and found a geometric mean of 0.46
ACH with a 90th percentile value of 1.26 ACH.
Office buildings typically are designed to have 15
cfin per person of ventilation, which results in a value
of about 1 ACH. The US EPA (Persily and Gorfain,
2004) measured ventilation at 369 office buildings
and found a median of 0.98 ACH. Slightly higher
ventilation rates per person are recommended for
restaurants, which yields design values of roughly 5
ACH given the higher density of persons in
restaurants compared with offices. Measurement
data for restaurants are relatively limited. One study
of nine Florida restaurants reported an average of 3.8
ACH (Cummings, et al., 1997). The measured values
of 1 to 2 ACH at the Grand Plaza site appear to be
relatively low for a restaurant, but are much higher
than the default value of 0.25 ACH in the US EPA
November 2002 guidance, which is based on the 10th
percentile for single residence buildings.
Assuming a steady-state mass balance, the emission
rate of PCE into the building was 0.086 g/hr based on
a ventilation rate of 1.9 ACH and the concurrent
indoor air measurement. QsoU = 0.082 L/min based
on the "hot spot" PCE concentration of 0.26%. The
total volume of soil gas entering the building is
almost certainly higher than this value, which
represents only the rate of contaminated soil gas
entering the building. EPA's default value for soil-
gas infiltration is 5 L/min for a residential structure
with a 100m2 footprint. Normalizing the Grand Plaza
value to this footprint yields QsoU = 0.044 L/min,
which is 0.9% of the EPA default value.
The inhalation unit risk (IUR) for PCE is usually
given as 3.0E-06 per ug/m3. For a IxlO"5 risk, the
resulting concentration is 0.00001/3.OxlO"6 = 3.33
M-g/m3. This number reflects a continuous 70-yr
exposure and is then adjusted for the assumed
exposure scenario. If the usual occupational
exposure scenario of 8 hr/day, 5 day/week, 50
week/yr for 25 years is assumed, the IxlO"5 risk level
is 41 |ag/m3. Therefore, average measured value of
PCE at this site yields an estimated risk of 2xlO"5.
Risks above IxlO"4 generally are considered
unacceptable and risks below IxlO"6 are considered
to be insignificant. The assumed exposure scenario is
conservative for this site given the turnover of
businesses at this location.
The installation of a sub-slab depressurization system
for this site was considered and a design was
prepared. There is, however, no regulatory
requirement for such a system. Representatives from
the City of Dallas, with input from TCEQ, elected not
to install a system at this time. It is recognized that
controls would be required in some other
jurisdictions based on the measured concentrations of
VOCs, such as PCE, in the indoor air and/or in the
sub-slab soil gas.
The results for this site have several implications for
the standard regulatory approach for evaluating vapor
intrusion. One, field investigations at sites with
surface releases should include measurements in
surface soil layers. Groundwater, soil, and soil-gas
measurements at depth may not identify the
maximum concentrations present at the site. This
58
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study illustrates the extreme spatial variability
sometimes found in the subsurface at contaminated
sites. Two, the use of mean values instead of
maximum values may still be very conservative when
soil-gas measurements are used to estimate indoor air
concentrations using an a of 0.1 or 0.02. Three, the
US EPA defaults for parameters such as Qsoii, QBidg,
and AP may be very conservative for a given site.
Site-specific measurements can readily be performed
to provide more accurate estimates for these
parameters instead of relying on default values.
59
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SECTION 6
SPECIFICATIONS FOR CONTROL SYSTEM
FOR GRAND PLAZA SITE
6.1 Location
These specifications are for the installation of an
active soil depressurization systems at the Grand
Plaza site. As discussed elsewhere in this report, it
was ultimately decided not to install the system at
this time.
6.2 Site Specific Conditions
These specifications are based upon a limited
investigation of the site and therefore certain
installation details will need to be verified by the
installer at the time of bid or installation, as follows:
• The discharge of the system is to be at least 10
feet (3m) from any air intakes or openings into to
the building, including those which are mounted
on the roof (roof access was not available during
inspection). If the locations indicated for the
systems does not allow for this separation, the
discharge points may be rerouted to allow for
such a separation.
• The suction point locations may be within plus
or minus 2 feet (0.6 m) from the locations
indicated on the drawings to allow for
interference avoidance.
• Underground and underslab utility lines were not
definitively located during investigation.
Contractor to request such locates by the local
utility company, with specific attention to the
potential location of a gas line near the location
of the chicken fryer.
• Contractor to prime and paint all exterior and
exposed components of the system using a
primer and paint color acceptable to the client.
• Installation to be done in a manner that does not
interfere with the operation of the business
within the unit that these systems are to be
installed upon.
• Two active soil depressurizations are called out.
Each system is to be independent of the other. At
the option of the client, these systems may be
installed concurrently or sequentially as dictated
within the request for bid documentation.
• System to be installed in accordance with US
EPA Radon mitigation Standards EPA 402-R-
93-078, October 1993 (Revised April 1994)
available at
http://www.epa.gov/radon/pubs/mitstds.html.
• These specifications are provided as guidance for
installation. Where there is a conflict between
these specifications and local building codes, the
local building codes shall prevail. Furthermore,
the competency of the contractor is one of the
basis for selection and therefore it is expected
that if the contractor will identify interferences or
more optimal approaches and make appropriate
suggestions to the client in a manner that does
not conflict with the intent of the system.
• It is assumed that any building permits shall be
obtained by the contractor as needed for this
work in accordance with local regulations.
• It is also assumed that any air pollution permits
that may be needed for this system(s) shall be the
responsibility of the client, rather than the
contractor.
• Fan location and enclosures: It is suggested that
the fans and their enclosures be located as close
to the roofline as possible to avoid impact of
exterior parking space. Consequently, it is
suggested that the fan enclosures be inverted to
allow for vent piping to be as close to the wall as
possible.
• Where asphalt must be removed for installation
of suction points, the asphalt shall be repaired.
6.3. Active Soil Depressurization
System
The systems to be installed shall be designed to
extract soil gases from beneath the foundation and
exhaust them to a location above the roofline of the.
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structure and at a location where soil gases will not
re-enter the building
6.3.1 Depressurization Fan
Fans to be capable of delivering a minimum of 190
cubic feet per minute (5.4 nrVmin) at 1.0 inches (2.5
cm) of water column differential pressure. Fans to be
rated for exterior use in a hot, humid climate, as will
as conveyance of moist, non-combustible air.
Fan systems to be: PDS MI 220 system as
manufactured by professional Discount Supply
(www.pdsradon.com) matched with Fantech HP-
220 fan, or approved equivalent.
Fans casings to have 6-inch (15 cm) intake and
discharges
Power: 120 volt, 60 Hz, 150 watt
Fan to be matched with performance indicator to
provide indication of current draw as a means to
indicate continued fan operation.
Number required: two (2)
Fan Power Supply
Electrical power is to be routed to the indicator panel
and fan in accordance with the local electrical codes
and in conformance with the existing electrical
service within the subject building.
Power for the system indicator is to be supplied from
the same circuit that supplies power for the fan.
Existing circuits may be utilized, if the addition of
the system in addition to current use would not
exceed 80% of the circuit capacity.
Fan Orientation and Connection
• Fan shall be positioned in the vent pipe system in
a vertical manner.
• Fan is to be secured to the vent pipe system on
both inlet and outlet connections with flexible
connectors secured by stainless steel hose clamps
to facilitate removal.
• Fans shall not be glued or otherwise permanently
attached to the pipe system.
Fan Enclosure
The fan is to be housed in an enclosure designed to
protect it from wind and physical abuse. Enclosure is
to consist of a wall mounted base plate and cover.
Material of construction is to be water-resistant ABS
plastic. Fan enclosure to be FH-89 fan housing as
manufactured by RCI, 511 Industrial Drive, Carmel
Indiana (317) 846-7486 or approved equivalent.
Enclosure is to be primed and painted with two coats
of cover in a color to match the exterior color scheme
as is reasonably achievable.
System Performance Indicator
• Each system will have a performance indicator
mounted as indicated in the Figures.
• Indicator to be as specified in Section 6.3.1.
• Electrical power for the system indicator is to be
supplied from the same circuit that supplies
power for the fan. Power to be routed in
compliance with local electrical codes.
• Affixed to the power indicator shall be a label
detailing the system ID number (i.e., SP-1, SP-2,
etc.). The number of the circuit breaker
providing power to the ASD system and the
panel ID # is to be written on inside of
performance indicator box.
• Indicator to be adjusted to "Green" zone after fan
has been activated and system installation is
complete. Power draw is also to be measured
(current x voltage) and provided to client at
conclusion of work.
6.3.2 Pipe and Fittings
Vent pipe to be as follows:
Construction
Size
Schedule:
Primed and painted?
Fittings
PVC or ABS ASTMD-1785
4-inch nominal
80
Yes
Solvent welded (except mechanical
connection to fan
Routing
In addition to normal practices for running plumbing
lines as though it were soil vents, the pipe shall not
be configured such that there would be any
accumulation of moisture within pipe. Pipe to have a
positive slope back to the suction point of no less
than 1/8 - inch per foot (0.3 cm per 30 cm).
Pipe Supports
Pipe supports shall be used to secure the piping
system. At a minimum pipe supports shall be applied
every 2 meters in vertical runs and every 1.5-meter in
horizontal runs. Pipe supports are to be applied as
noted on the drawings with a minimum of pipe
supports near the suction point and at the discharge,
with the fan being independently supported within
the enclosure.
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All pipe supports are to be made of non-corrosive
material such as stainless steel or galvanized steel.
Pipe supports to be a channel and clamp system such
as Unistrut or approved equivalent.
Vent Discharge
Location
The discharge of the system shall be oriented either
vertically or at a 45-degree angle away from the
building and in a location where the discharged
gasses may not enter any building or adjacent
building openings. In addition to this, the discharge
shall be:
• At least 10 feet (3 m) above exterior grade
• At least 10 feet (3 m) away from a passive
opening into the building that is less than 2 feet
or 60 cm below the exhaust point as measured on
a horizontal plane, and 25 feet (7.6 m) away
from active air intakes for building mechanical
systems.
• At least 10 feet (3 m) from any opening into an
adjacent building or public access or easement.
Note that the distance requirements from the point of
discharge to the building opening or mechanical
system intake is to be measured either directly
between the two points or to be the sum of
measurements made around intervening obstacles
such as building corners.
Discharge Screen
A screen constructed of stainless steel or galvanized
metal shall be installed in the discharge after the
system has been activated for at least five minutes to
clear any residual debris. See Figures.
A UV and weather resistant label shall be affixed to
the discharge pipe reading: CA UTION Soil Gas Vent
- Do not tamper or disturb.
6.3.3 Suction Point
The suction point is to be installed as depicted in the
Figures, with the following additional comments:
• Prior to coring holes through concrete surfaces, a
rebar locator for ferrous materials is to be used to
locate a pathway where rebar will not be cut or
there will be a minimal impact. Where re-bar is
nicked or cut, the exposed portion of the re-bar is
to be protected by a material designed to prevent
corrosion of rebar, such as 3M Scotchkote
413/215/PC or approved equivalent.
• A minimum of 1.5 cubic feet (42 L) of soil is to
be dug out from suction point, beneath the slab.
Excavation should be upwards to the bottom of
the slab to preclude of soil from falling into
suction point.
• Suction point piping to be well sealed to inside
of concrete core as indicated in the figure to
assure an airtight seal.
• A rigid pipe support is to be installed as close to
the suction point as possible to maintain the
integrity of the seal.
6.3.4 Sealing
Backer Rod and Sealing of Suction Point
Where suction piping penetrates a wall, a positive
seal is to be made that is also flexible. A minimum of
2 wraps of closed cell backer rod, is to be used and of
sufficient diameter to provide a compression fit
between the inside of the core and the outside of the
pipe. External portion of connection to have an
elastomeric polyurethane caulk, such as Sonolastic
NP-I, Geocel21OO or approved equivalent and is to
be applied to a minimum depth of 1-inch.
Caulking Concrete
Efforts shall be made to identify leak points where
either interior or exterior air is being drawn down to
the sub-grade due to the negative pressures created
by the ASD system. This can be identified by non-
thermal smoke. Said openings are to be caulked using
an elastomeric polyurethane such as Sonolastic NP-1,
Geocel 2100 or approved equivalent.
6.3.5 Asbestos Containing Materials
Contractor is to take appropriate precautions when
drilling through building materials that may be
suspected of containing asbestos. If any suspected
asbestos containing materials are encountered, the
material is not be disturbed and the client is to be
notified, prior to continuing work that would disturb
suspected asbestos containing material.
6.3.6 Excavation and Repair
Where excavation and or demolition is required the
area is to be secured and appropriate safety measures
are to be taken both during and after hours to protect
the public.
Where excavation or demolition of concrete
sidewalks, planters, tile, etc. is required, said area is
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to be restored as close as reasonably possible to its
original condition.
6.3.7 Painting
All pipe, fan shroud covers, conduit, etc. shall be
painted to match exterior color scheme. Plastic
components are to be primed with an appropriate
primer for the base material to be painted. A
sufficient number of surface coatings are to be
applied to fully cover the component. All system
components will be painted in accordance with client
specifications.
6.3.8 Labeling Requirements
Labels listed below are to be of suitable material for
environment they will be located. Labels located
outdoors are to be resistant to UV and weather
damage.
ASD System
At least one label shall be affixed to the mitigation
system in all locations where vent pipe is visible.
Label is to read: CAUTION Soil Gas Vent - Do not
tamper or disturb.
Circuit breaker
The circuit within the building power panel from
which the ASD fan power supply is obtained is to be
labeled "Soil Vent System".
Performance Indicator
The number of the circuit breaker providing power to
the ASD system is to be labeled on inside of each
performance indicator box.
6.4 Figures and Details
The following non-scaled figures and details are
provided as guidances for installation:
Figure 6-1: Installation Schematic
Figure 6-2: Location of Suction Points
Figure 6-3: Pictorial Indication of System Locations
& Details
Figure 6-4: Detail 1 Suction Pit
Figure 6-5: Detail 2 Vent Discharge
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Stand-off bracket for discharge
Roof
Unistrut channel, or
equivalent, pipe support
anchored to wall.
Terminate discharge a minimum of 12
inches above roof line.
Locate at least 10 feet from any
mechanical air intake on roof
Install screen on discharge See Detail 2
Mount fan within Rt I enclosure.
Enclosure comes with transition box.
Mount fan in enclosure near roof line.
Invert cover to allow suction piping to be
to wall.
Slot cover at top to allow it to slip around
discharge pipe.
Piping and fittings to be 4-inch schedule 80,
PVC both below and above the fan.
ASTM D-l785. Joints to be solvent welded.
All exposed components, including piping to
be primed and pointed to match existing
building exterior color scheme.
Buck 111 I and compact excavation
Repair asphalt uhere disturbed
Suction Point
See Detail I
Excavate pit up to bottom of floor slab
Remove minimum of 3 cu. ft. of soil from behind
foundation wall.
Figure 6-1. Installation Schematic
64
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Side
SP-1
SP-2
-22 feet
o
-22 feet
.it:
o
CD
Other Units
Feet
D 8 12
Figure 6-2. Location of Suction Points
65
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SP-1
Locate fan systems up hiyh i-n building.
Piping to be schedule 80 PVC for durability.
Horizontal cores through foundation wall.
Asphalt to be cut to allow access for core rigs and replaced.
Pipe and shroud lo tv primed and painted.
Suction point locations can be moved 2 feet either direction from point noted to
avoid obstructions.
Discharge points to Ix 10 feet from rooftop air intakes.
• (.'ore hori/onkillv through
foundation wall,
• Avoid re-bar-patch if nicked or
damaged
• Patch asphalt, if disturbed.
• Location can be -+• 2 feet from
specified location
Locale performance indicators on
wall adjacent to circuit panel.
Utilize existing circuit if not
overloaded, otherwise install new
circuit (fans rated for 150 watts
each).
System Performance Indicator
One per fan
Could be mounted externally i
desired.
Matched to fan
See specifications
Figure 6-3. Pictorial Indication of System Locations and Details
66
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Compact every 6 in
•.'.Ik-ii l •,!•. k !'il I n r.-
Figure 6-4. Detail 1 Suction Pit
Notes:
• Location of core should be such that upper edge of hole is as close as possible to the bottom of the slab.
Excavate if necessary.
• Locate in accordance with general location shown on plan drawing, avoiding
• sub grade utilities (call for utility locates and applicable digging permits)
• Use core bit to cut hole - Do not chip out. Core 6-inch diameter hole through concrete wall.
• Use re-bar locator to avoid rebar where possible. REPAIR KNICKED OR DAMAGED REBAR with 3M
Scothkote 413/215 PC or equivalent.
• Excavate out a minimum of 1.5 cu. ft. of soil. Soil must be removed up to underside of slab.
• Insert vent pipe through hole extending at least 2 inches into excavated pit.
• Seal pipe to inside of core with a minimum of two wraps of 1 -inch backer rod. Seal outer portion of pipe to wall
with polyurethane caulk with a minimum depth of linch.
• Back fill hole, stopping at 6 in depths to compact soil.
• Replace asphalt where it was removed to facilitate coring of wall.
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4-inch \ 4-incl
1 i- inch slainless
sleel screen
1'il in heiween pipe
and inlornul should
Figure 6-5. Detail 2 Vent Discharge
68
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SECTION 7
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