Carter G. Woodson_2015-01-29 2nd Woodson Indoor VI Report-OCR

SUMMARY REPORT OF SECOND INDOOR AIR SAMPLING FOR
VAPOR INTRUSION EXPOSURE ASSESSMENT
CARTER G. WOODSON SCHOOL
MIDDLE SCHOOL BUILDING
420 GOLDFLOSS STREET
WINSTON-SALEM, NORTH CAROLINA

Prepared For:

Ms. Ruth Hopkins School Administrator
Carter G. Woodson School
420 Goldfloss Street
Winston-Salem, North Carolina 27127
Ms. Hazel M. Mack
President
Challenges of the Twenty-First Century, Inc.
420 Goldfloss Street
Winston-Salem, North Carolina 27127
Prepared By:

Mid-Atlantic Associates, Inc.
409 Rogers View Court Raleigh, North Carolina 27610

January 29, 2015

SUMMARY REPORT OF SECOND INDOOR AIR SAMPLING FOR
VAPOR INTRUSION EXPOSURE ASSESSMENT
CARTER G. WOODSON SCHOOL
MIDDLE SCHOOL BUILDING
420 GOLDFLOSS STREET
WINSTON-SALEM, NORTH CAROLINA

January 29, 2015
Mid-Atlantic Project No. 000R2592.02

Prepared for: Prepared by:
Ms. Ruth Hopkins MID-ATLANTIC ASSOCIATES, INC.
School Administrator
Carter G. Woodson School
420 Goldfloss Street
Winston-Salem, North Carolina 27127 William Service
Ms. Hazel M. Mack Senior Environmental Toxicologist
President
Challenges of the Twenty-First Century, Inc.
420 Goldfloss Street Winston-Salem, North Carolina 27127
Daniel H. Nielsen, P.E.
Principal Engineer

TABLE OF CONTENTS

1.0 SUMMARY ............................................................................................................ 1

2.0 PROJECT INFORMATION ................................................................................... 1

3.0 AIR SAMPLING .................................................................................................... 1

4.0 RESULTS .............................................................................................................. 2

DRAWINGS
Drawing 1 – Topographic Site Map
Drawing 2 - Air Sample Location Map

TABLE
Table – Vapor Intrusion Exposure Assessment – December 30, 2014

APPENDICES

Appendix A - Meteorological Data - December 30, 2014 Appendix B - Laboratory Results and Chain-of-Custody Form
Appendix C – Report of First Round Indoor Air Sampling

1.0 SUMMARY
On December 30, 2014, Mid-Atlantic Associates, Inc. (Mid-Atlantic) collected indoor air
samples at the Carter G. Woodson (Woodson) Middle School. The Woodson School
site has been entered into the North Carolina Department of Environment and Natural
Resources, Division of Waste Management (NCDWM), Brownfields Program as an
eligible Brownfields Project as of September 4, 2014. Sampling was conducted as a follow-up to vapor intrusion sampling conducted at the school on July 11, 2014; results
of which are contained in a report dated August 7, 2014 (attached in Appendix C).
Sampling methods, locations and laboratory analysis for the December 2014 sampling
were summarized in an Indoor Air Sampling Workplan dated October 30, 2014 and are
identical for the July 2014 and December 2014 sampling events. The work plan was approved by Sharon Eckard of the Brownfields Program on November 6, 2014.

Tetrachloroethylene (PCE), trichloroethylene (TCE), and trichlorofluoromethane had
been identified as contaminants of concern (COC) in groundwater and in soil vapor on
the site. Indoor air was sampled for those analytes and results are compared to the residential indoor air screening levels established by NCDWM.

There were no exceedances of residential indoor air screening levels in any of the six
indoor air samples collected in this sampling event. Trichlorofluoromethane and PCE concentrations detected were at least an order of magnitude less than the NCDWM indoor air screening levels for all samples. Trichloroethylene was not detected in any of
the indoor air samples. Similarly, there were no exceedances of NCDWM screening
levels in the July, 2014 indoor air sampling event.

2.0 PROJECT INFORMATION

In a “Phase II Environmental Site Assessment” conducted by Hart & Hickman, dated May
16, 2014, PCE and TCE were detected in groundwater monitoring wells in the vicinity of the Woodson Middle School building in concentrations that exceeded the NCDWM Residential Vapor Intrusion Screening Levels for groundwater (January and June 2014
versions). On June 13, 2014 the EI Group, Inc. conducted a “Limited Phase II
Environmental Site Assessment” at the school and reported groundwater concentrations of
PCE in excess of the DWM vapor intrusion screening limits for PCE in the vicinity of the Middle School. Sub-slab soil gas samples collected for the same report at the Middle School showed soil vapor concentrations of PCE in excess of the DWM residential vapor
intrusion screening level.

Trichlorofluoromethane (Freon) was detected in two of the EI Group Phase II soil gas samples but not at concentrations that exceeded residential soil gas screening levels.

3.0 AIR SAMPLING

On December 30, 2014, six indoor air samples were collected in the Middle School building and one outdoor air (background) air sample was collected upwind of the Middle
Summary Report for Vapor Intrusion Exposure Assessment January 29, 2015
Carter G. Woodson Middle School Building Page 2
Winston Salem, North Carolina

School building (Drawing 2). Samples were analyzed for the site COCs – PCE, TCE, and trichlorofluoromethane.

The indoor and outdoor air samples were obtained using seven 6-liter evacuated Summa
canisters fitted with 8-hour flow regulators. Each of the samples was collected over an
approximate 8-hour sampling period at breathing zone height of approximately four feet. Sampling locations were selected, in part, so that results would be obtained from each
area of the building that is served by a separate heating, ventilating, and air conditioning
(HVAC) system. Sample locations are as shown in Drawing 2.

In order to approximate worst-case vapor intrusion circumstances, the following conditions were in place during sampling:

 The building was unoccupied and remained closed (including operation of doors
and windows) throughout the sampling period.
 Sampling was conducted during winter the high temperature (37 °F) was lower than
the average low temperature for that date (48°F) (see attached Meteorological
Data) in Appendix A.
 HVAC systems were operated in heating mode throughout the sampling period.

Samples were analyzed using U.S. Environmental Protection Agency (EPA) Compendium
Method TO-15. Only chemicals of concern were analyzed for and reported as
recommended in DWM Vapor Intrusion Guidance (April 2014). Tetrachloroethylene was selected as an analyte because groundwater samples and a soil gas sample
concentration exceeded DWM residential vapor intrusion screening levels (Hart &
Hickman, and EI Group Phase II reports). Trichloroethylene was selected for analysis
because it was detected in groundwater at concentrations that exceeded DWM residential
vapor intrusion screening levels (Hart & Hickman report only). Trichlorofluoromethane was not detected in groundwater or soil gas at concentrations that exceeded DWM residential
vapor intrusion screening limits in either of the Phase II reports. However, because
trichlorofluoromethane was detected in groundwater in both Phase II reports and was
detected in soil gas in the EI Phase II report, it was selected as an indoor analyte for this
sampling event.

4.0 RESULTS

Vapor sample results are summarized in Table 1. Results are compared to the NCDWM “Residential Vapor Intrusion Screening Levels (June 2104)” for indoor air which use a target cancer risk (TCR) = 1.0E-06 and a non-cancer target hazard quotient (THQ) = 0.2.

None of the indoor air samples collected had concentrations of target analytes that
exceeded NCDWM vapor intrusion screening levels for indoor air in residential environments at target cancer risk TCR = 1.0E-06 or target hazard quotient THQ = 0.2.
Summary Report for Vapor Intrusion Exposure Assessment January 29, 2015
Carter G. Woodson Middle School Building Page 3
Winston Salem, North Carolina

Low levels of trichlorofluoromethane and PCE were detected in each of the indoor
samples. Trichloroethylene was not detected in any of the samples collected. All of the
results for PCE and trichlorofluoromethane were at least one order of magnitude less than
the NCDWM vapor intrusion screening levels. The results for TCE were below the
laboratory analytical method detection limit (MDL) for all six indoor samples. The MDL for TCE (0.057 ug/m3) is approximately 13% of the NCDWM vapor intrusion screening level
for TCE (0.417 ug/m3).

DRAWINGS

´
TOPOGRAPHIC SITE MAPCARTER G. WOODSON SCHOOL420 & 437 GOLDFLOSS STREETWINSTON-SALEM, NORTH CAROLINA
DRAWN BY:DATE:
ENG. CHECK:
JOB NO:
APPROVAL:
DRAFTCHECK:GIS NO:
DWG NO:
REFERENCES:SCALE:
DAVIE
FORSYTH GUILFORD
DAVIDSON
STOKES
YADKIN
SURRY
RANDOLPH
ROCKINGHAM
ROWAN §¨¦I85
§¨¦I40
§¨¦I73
§¨¦I40 F
AREA SHOWN WITHINFORSYTH COUNTY
JANUARY 2015
000R2592.02
02G-R2592.02-11
1. WINSTON-SALEM EAST, NC DIGITAL RASTER GRAPHIC, USGS. SCANNED FROM 1:24,000-SCALE WINSTON-SALEM EAST, NC TOPOGRAPHIC MAP, PUBLISHED 1997, USGS.2. INSET MAP DIGITAL DATA FROM 2002 NATIONAL TRANSPORTATION ATLAS, BUREAU OF TRANSPORTATION STATISTICS, WASHINGTON, D.C.3. PROPERTY BOUNDARY DATA FROM FORSYTH COUNTY GIS.
CONTOUR INTERVAL = 10 FEET
0 2,000 4,0001,000 Feet
SITE
1:24,000
#0
#0 #0
#0
#0
#0
#0A-7
A-3
A-2 A-1
A-4A-5
A-6
´
AIR SAMPLE LOCATION MAPCARTER G. WOODSON SCHOOL420 & 437 GOLDFLOSS STREETWINSTON-SALEM, NORTH CAROLINA
DRAWN BY:
DRAFT CHECK BY:
ENGINEER CHECK BY:APPROVED BY:
DATE: DECEMBER, 30 2014
JOB NO.: 000R2592.01
GIS NO.: 03G-R2592.01-2
DRAWING NO.: 2
REFERENCE: PARCEL AND ROAD GIS DATA FROM FORSYTH COUNTY GIS. 2012 AERIAL IMAGERY FROM NC CGIA. MID-ATLANTIC FIELD NOTES.
#0 AIR SAMPLE LOCATIONAPPROXIMATE INDOOR FLOORPLAN 40 0 4020 Feet
LABORATORY
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APPENDIX A

METEOROLOGICAL DATA
DECEMBER 30, 2014
Woodson School Indoor Air Sampling
Meterological Data
Weather History for Winston-Salem, NC
Tuesday, December 30, 2014
Temperature
Mean Temperature
Max Temperature
Min Temperature
Degree Days
Heating Degree Days
Moisture
Dew Point
Average Humidity
Maximum Humidity
Minimum Humidity
Precipitation
Precipitation
Sea Level Pressure
Sea Level Pressure
Wind
Wind Speed
Max Wind Speed
Max Gust Speed
Visibility
Events
Actual
34 °F
37 °F
30 °F
32
31 °F
86
93
73
0.07 in
30.34 in
7 mph (NE)
12 mph
18mph
Smiles
Rain
Averages and records for this station are not official NWS values.
Average
48 °F
30 °F
Record
76 °F (1981
10 °F (19T
-()
Click here for data from the nearest station with official NWS data (KGSO).
T =Trace of Precipitation, MM= Missing Value Source: NWS Daily Summary
F Temperab.ire DetM Point .l\verage Higi1/Lcw~ c
:~ 30
25
20
midnight1
-------------------~ ; ~---~~~----~---~--~~~~~~~~ .1
-4
I I I I I .7
2 3 4 5 6 7 3 9 10 11 noon 2 3 4 5 6 7 3 9 10 11
in Hg Barometric Pressure hPa
30 .5 ~ ~ 1033 30 .4 ----------------------1029
""0., --------------------------------10?6 .J . .J ~....__~ ..
~~:~ ~ I I I I I I I I I I I I I I I I I I I ~~~:
midnight 1 2 3 4 5 6 7 3 9 10 ll noon 1 2 3 4 5 6 7 8 9 10 11
mph \.f~lncl Speecl '1Jlilml Gust
25.0 ~ 20.0
15.0
10 0 ------/""--. ,,...,.---__ .--.... . ~ ---...,_,.....-.../ ~ -----------......... ____ /"·-...... ____ 5·0
I I I I I I I I I I I I I I I ~------;--,-.... 0.0
j ij
,_ 0
midnight 1 2 3 4 5 6 7 8 9 10 11 noon 1 2 3 4 5 6 7 8 9 ·10 ·11
:~Ht ~Ulnd Dir (cleg)
... .. . . . . . . .. . j
0.0 .. I ., ·, I •, I •, ,
micfnight1 2 3 4 5 6 7 3 9 10 11 noon 2 3 4 5 6 7 3 9 10 1~lfmtlilr
Reference: Weather Underground (Weatherunderground.com)
http://www.wunderground.com/history/airport/KINT/2014/12/30/DailyHistory.html?req_city=NA&r
eq_state=NA&req_statename=NA

APPENDIX B

LABORATORY RESULTS AND
CHAIN-OF-CUSTODY FORM
39 Spruce Street * East Longmeadow, MA 01028 * FAX [phone] * TEL. [phone]
Page 1 of 18 15A0046_1 Contest_Final_IHSB_MDL_DUAL 01 08 15 1603
39 Spruce Street * East Longmeadow, MA 01028 * FAX [phone] * TEL. [phone]
Page 2 of 18 15A0046_1 Contest_Final_IHSB_MDL_DUAL 01 08 15 1603
39 Spruce Street * East Longmeadow, MA 01028 * FAX [phone] * TEL. [phone]
Page 3 of 18 15A0046_1 Contest_Final_IHSB_MDL_DUAL 01 08 15 1603
39 Spruce Street * East Longmeadow, MA 01028 * FAX [phone] * TEL. [phone]
Page 4 of 18 15A0046_1 Contest_Final_IHSB_MDL_DUAL 01 08 15 1603
39 Spruce Street * East Longmeadow, MA 01028 * FAX [phone] * TEL. [phone]
Page 5 of 18 15A0046_1 Contest_Final_IHSB_MDL_DUAL 01 08 15 1603
39 Spruce Street * East Longmeadow, MA 01028 * FAX [phone] * TEL. [phone]
Page 6 of 18 15A0046_1 Contest_Final_IHSB_MDL_DUAL 01 08 15 1603
39 Spruce Street * East Longmeadow, MA 01028 * FAX [phone] * TEL. [phone]
Page 7 of 18 15A0046_1 Contest_Final_IHSB_MDL_DUAL 01 08 15 1603
39 Spruce Street * East Longmeadow, MA 01028 * FAX [phone] * TEL. [phone]
Page 8 of 18 15A0046_1 Contest_Final_IHSB_MDL_DUAL 01 08 15 1603
39 Spruce Street * East Longmeadow, MA 01028 * FAX [phone] * TEL. [phone]
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39 Spruce Street * East Longmeadow, MA 01028 * FAX [phone] * TEL. [phone]
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39 Spruce Street * East Longmeadow, MA 01028 * FAX [phone] * TEL. [phone]
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39 Spruce Street * East Longmeadow, MA 01028 * FAX [phone] * TEL. [phone]
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39 Spruce Street * East Longmeadow, MA 01028 * FAX [phone] * TEL. [phone]
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39 Spruce Street * East Longmeadow, MA 01028 * FAX [phone] * TEL. [phone]
Page 14 of 18 15A0046_1 Contest_Final_IHSB_MDL_DUAL 01 08 15 1603
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Page 2 of 2
Login Sample Receipt Checklist
(Rejection Criteria Listing -Using Sample Acceptance Policy)
Any False statement will be brought to the attention of Client
Question
1) The coolers'/boxes' custody seal, if present, is intact.
2) The cooler or samples do not appear to have been
compromised or tampered with.
3) Samples were received on ice.
4) Cooler Temperature is acceptable.
5) Cooler Temperature is recorded.
6) COG is filled out in ink and legible.
7) COG is filled out with all pertinent information.
8) Field Sampler's name present on COG.
9) Samples are received within Holding Time.
10) Sample containers have legible labels.
11) Containers/media are not broken or leaking and valves
and caps are closed tightly.
12) Sample collection date/times are provided.
13) Appropriate sample/media containers are used.
14) There is sufficient volume for all requsted
analyses, including any requested MS/MSDs.
15) Trip blanks provided if applicable.
Doc #278 Rev. 5 October 2014
Answer (True/False)
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Date/Time:\\£\\ S-
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APPENDIX C

REPORT OF FIRST ROUND INDOOR AIR SAMPLING
SUMMARY
Elevated levels of chemicals were recently discovered in groundwater and soil gas at
the Carter G. Woodson (Woodson) Middle School. Tetrachloroethylene (PCE), and
trichloroethylene (TCE) exceed residential screening levels established by the North
Carolina Department of Environment and Natural Resources, Division of Waste
Management (NCDWM). Trichlorofluoromethane was repeatedly detected in soil gas
and water samples, although at concentrations below screening levels. Vapor intrusion
guidance from NCDWM recommends that indoor air sampling be conducted to measure
indoor exposure from constituents of concern (COCs) when screening levels are
exceeded. As a result, Woodson School administrators and officers of Challenges of the
Twenty-First Century, Inc. (the owner of the property) contacted Mid-Atlantic
Associates, Inc. (Mid-Atlantic) to collect indoor air samples in the Woodson Middle
School. On July 11, 2014, six indoor air samples were collected for analysis of PCE,
TCE, and trichlorofluoromethane.
There were no exceedances of residential indoor air screening levels in the air samples
for the detected COCs. TCE was not detected in any of the samples. The NCDWM
residential screening level for PCE is 8.34 micrograms per cubic meter (ug/m3). Indoor
PCE concentrations ranged from 0.16 to 0.38 ug/m3 (less than 2% of the screening
level). The residential indoor air screening level for trichlorofluoromethane is 146 ug/m3.
Trichlorofluoromethane concentrations ranged from 1.5 to 1.6 ug/m3 (approximately 1 %
of the screening level). The levels were very similar to levels of PCE (20 ug/m3) and
trichlorofluomethane (1.3 ug/m3) detected in outdoor, ambient air at the middle school.
Based on the findings of the indoor air sampling in comparison to current NCDWM
guidance for vapor intrusion, elevated levels of PCE, TCE and trichlorofluoromethane in
groundwater and soil vapor at the Woodson Middle School grounds do not pose
unacceptable risk to building occupants by the vapor intrusion pathway.
PROJECT INFORMATION
In a "Phase II Environmental Site Assessment" conducted by Hart & Hickman, dated May
16, 2014, PCE and TCE were detected in groundwater monitoring wells in the vicinity of
the Woodson Middle School building in concentrations that exceeded the NCDWM
Residential Vapor Intrusion Screening Levels for groundwater (January and June 2014
versions). On June 13, 2014 the El Group, Inc. conducted a "Limited Phase II
Environmental Site Assessment" at the school and reported groundwater concentrations of
PCE in excess of the DWM vapor intrusion screening limits for PCE in the vicinity of the
Middle School. Sub-slab soil gas samples collected for the same report at the Middle
School showed soil vapor concentrations of PCE in excess of the DWM residential vapor
intrusion screening level.
Trichlorofluoromethane (Freon) was detected in two of the El Group Phase II soil gas
samples but not at concentrations that exceeded residential soil gas screening levels.
The April 2014 "Vapor Intrusion Guidelines" published by NCDWM recommend indoor air
sampling if groundwater and/or soil gas concentrations exceed the applicable screening
levels. Mid-Atlantic has prepared this indoor air sampling report for a vapor intrusion
Summary Report for Vapor Intrusion Exposure Assessment
Carter G. Woodson Middle School Building
Winston Salem, North Carolina
August 7, 2014
Page2
exposure assessment that was conducted on July 11, 2014 at the Carter G. Woodson
Middle School building located at 420 Goldfloss Street, Winston Salem, NC (Drawing 1 ).
BUILDING ASSESSMENT
On July 7, 2014, in preparation for indoor air sampling, the Woodson Middle School
building was assessed by Mid-Atlantic with the following objectives:
• Identifying indoor sources of air contaminants that could influence sampling results,
• Documenting that worst-case vapor intrusion conditions were established in the
building prior to and during sampling; and
• Qualitatively assessing the susceptibility of the building to soil gas intrusion.
The Woodson Middle School building has approximately 16,000 square feet of floor space
(Photographs 1 and 2). Each classroom in the building has at least one operable window
(see Photograph 3). The building gymnasium (Photograph 4) is served by four roof-
mounted HVAC systems. The classroom and office areas of the building are served by
four zoned HVAC systems located in the building attic (Photograph 5). Each of the
systems has mechanically-provided outdoor air ventilation that serves to pressurize the
building relative to the outdoors. The building foundation is slab-on-grade. The building
slab and flooring appear to be in good condition with no visible cracking.
Cleaning supply rooms, restrooms, the school science and computer laboratories, and the
school kitchen were inspected in order to identify consumer products, cleaning supplies,
laboratory supplies or other products that could contain chemicals that were identified for
indoor air sampling (PCE, TCE and trichlorofluoromethane). There were no products or
materials identified in the building that contained any of these chemicals. Scheduled
cleaning and maintenance of the HVAC systems that serve the building was postponed
until after indoor air sampling was completed.
Several characteristics of the building and mechanical systems suggest that the building
has a relatively low susceptibility to vapor intrusion and that the building sub-slab to indoor
attenuation factor is likely to be lower (i.e., greater attenuation provided) than the default
sub-slab to indoor air attenuation factor (AF=0.03) used to calculate residential sub-slab
soil gas screening values. Some of those building characteristics include:
• HVAC systems with mechanical provision of outdoor air that serves to pressurize
occupied building space.
• Commercial slab-on-grade construction.
• Relatively young building age with flooring and slab in good condition.
• Large building volume per building footprint relative to residential buildings.
Summary Report for Vapor Intrusion Exposure Assessment
Carter G. Woodson Middle School Building
Winston Salem, North Carolina
AIR SAMPLING
August 7, 2014
Page3
On July 11, 2014, six indoor air samples were collected in the Middle School building and
one outdoor air (background) air sample was collected upwind of the Middle School
building (Drawing 2). Samples were analyzed for the site COCs -PCE, TCE, and
trichlorofluoromethane.
The indoor and outdoor air samples were obtained using seven 6-liter evacuated Summa
canisters fitted with 8-hour flow regulators. Each of the samples was collected over an
approximate 8-hour sampling period at breathing zone height of approximately four feet.
Sampling locations were selected, in part, so that results would be obtained from each
area of the building that is served by a separate heating, ventilating, and air conditioning
(HVAC) system. Sample locations are as shown in Drawing 2.
In order to approximate worst-case vapor intrusion conditions, the following conditions
were in place during sampling:
• The building was unoccupied and remained closed (including operation of doors
and windows) for at least four days prior to sampling and throughout the sampling
period.
• Sampling was conducted in mid-summer on a day when the high temperature (89.6
°F) was greater than the average high temperature for that date (84 °F) (see
attached Meteorological Data).
• HVAC systems were operated in cooling mode at least four days prior to and
throughout the sampling period.
Samples were analyzed using U.S. Environmental Protection Agency (EPA) Compendium
Method T0-15. Only chemicals of concern were analyzed for and reported as
recommended in DWM Vapor Intrusion Guidance (April 2014). Tetrachloroethylene was
selected as an analyte because groundwater samples and a soil gas sample
concentration exceeded DWM residential vapor intrusion screening levels (Hart &
Hickman, and El Group Phase II reports). Trichloroethylene was selected for analysis
because it was detected in groundwater at concentrations that exceeded DWM residential
vapor intrusion screening levels (Hart & Hickman report only). Trichlorofluoromethane was
not detected in groundwater or soil gas at concentrations that exceeded DWM residential
vapor intrusion screening limits in either of the Phase II reports. However, because
trichlorofluoromethane was detected in groundwater in both Phase II reports and was
detected in soil gas in the El Phase II report, it was selected as an indoor analyte for this
sampling event.
Summary Report for Vapor Intrusion Exposure Assessment
Carter G. Woodson Middle School Building
Winston Salem, North Carolina
RESULTS
Air Sampling
August 7, 2014
Page4
Vapor sample results are summarized in Table 1. Results are compared to the NCDWM
"Residential Vapor Intrusion Screening Levels (June 2104)" for indoor air which use a
target cancer risk (TCR) = 1.0E-06 and a non-cancer target hazard quotient (THQ) = 0.2.
None of the samples collected had concentrations of target analytes that exceeded
NCDWM vapor intrusion screening levels for indoor air in residential environments at
target cancer risk TCR = 1.0E-06 or target hazard quotient THQ = 0.2. Low levels of
trichlorofluoromethane and PCE were detected in each of the samples (including the
background sample collected from outdoor air). Trichloroethylene was not detected in any
of the samples collected. Sample A-2 (Gaines Class) had the highest PCE and
trichlorofluoromethane concentrations detected. For sample A-2, the cumulative non-
cancer hazard index (assuming similar critical health effects of both compounds detected)
is Hl=0.01 which is approximately one percent of the target Hazard Index of 1. The sum
cancer risk for sample A-2 is 3.SE-08, which is between one and two orders of magnitude
lower than the target cancer risk of 1.0E-06. The levels of PCE and trichlorofluoromethane
found in indoor air were very similar to the levels detected in outdoor air.
CONCLUSIONS AND RECOMMENDATIONS
Results of the sampling indicate that indoor air concentrations from vapor intrusion at the
Woodson Middle School building are considerably lower than the NCDWM residential
screening levels for vapor intrusion. The highest concentrations detected in indoor air
samples are less than 2% of the screening level concentration for the corresponding
compound.
Indoor air concentrations of target analytes are similar throughout the school and outdoors.
The mean indoor concentration for PCE was 0.27 ug/m3 and the outdoor concentration
was 0.20 ug/m3. The mean indoor concentration for trichlorofluoromethane was 1.6 ug/m3
and the outdoor concentration was 1.3 ug/m3.
Although concentrations of indoor air contaminants, from either subsurface or indoor
sources, can be expected to vary considerably over time, the multiple lines of evidence
from this study indicate that that vapor intrusion is unlikely to present unacceptable
exposure risk in the Woodson Middle School building.
TABLES
Mid Atlantic
Engineering & Environmental Solutions
DRAWINGS
Mid Atlantic
Engineering & Envir-onmental Solutions
PHOTOGRAPHS
Mid Atlantic
Engineering & Environmental Solutions
1. Middle School Building (Exterior -North Elevation)
2. Middle School Building (Exterior -South Elevation)
Mid Atlantic
Engineering & Environmental Solutio ns
3. Classroom Interior Showing Operable Window
4. Middle School Gymnasium
Mid Atlantic
Engineering & Environmental Solutions
5. Middle School Attic (Showing One of Four Zoned Air Handling Units)
Mid Atlantic
Engineering & Environmental Solutio ns
METEOROLOGICAL DATA
JULY 11, 2014
Mid Atlantic
Engineering & Environmental Solutions