W912DR18R0055_-_Attachment_BF_-FINAL_OU6_Bldg_151_SSDS_DesignREV1_6.12.18_combined.pdf.nhd3u0q.partial

G:\Projects\02118 USACE-Baltimore\201.0001 - DSCR\Tech Memos\Building 151\SSDS Design\Final\FINAL OU6 Bldg 151 SSDS Design_1.22.18.docx

Arcadis U.S., Inc.

824 Market Street

Suite 820

Wilmington

Delaware 19801

Tel 302 658 1718

Fax 302 658 2068

Page:

1/7

MEMO

To:

David Hufford, CHMM

Defense Logistics Agency

Copies:

From:

Carlo M. DiTullio (Carlo.DiTullio@arcadis.com)

Date: Arcadis Project No.:

22 January 2018 02118201.0001

Subject:

Final DSCR Building 151 Vapor Mitigation (Sub-Slab Depressurization) System Design

Attachments:

Figures 1 through 8: Draft Design Drawings

Table 1: Anticipated SSDS Effluent Concentrations

Table 2: Anticipated Friction Losses

Attachment 1: Design Approach Technical Memo

Attachment 2: Vapor Pin Installation SOP

This technical memorandum describes the design prepared for the installation of a sub-slab depressurization system (SSDS) within Building 151 located in the Operable Unit (OU) 6 area of concern at the Defense Supply Center Richmond (DSCR). The purpose of this system is to mitigate the potential for future vapor intrusion issues as described in the July 2016 Draft Subsurface Vapor Intrusion Monitoring Report, Building 151, prepared by the United States Army Corps of Engineers (USACE). Performance objectives and elements of the design package are discussed in this document, which has been prepared by Arcadis North America (Arcadis) under the USACE, Baltimore district Contract No. W912DR-13-D- 0016, Task Order No. 0001.

BACKGROUND AND PERFORMANCE OBJECTIVES

Building 151 is located within the portion of the installation occupied by the Virginia Army National Guard (VANG) and serves as their consolidated vehicle maintenance operations facility. The building consists of vehicle maintenance bays, sub-grade service pits, offices, a breakroom, toolroom and other facilities and arcadis.com G:\Projects\02118 USACE-Baltimore\201.0001 - DSCR\Tech Memos\Building 151\SSDS Design\Final\FINAL OU6 Bldg 151 SSDS Design_1.22.18.docx Page:

2/7

MEMO

is occupied by mechanics and supervisors during business hours. Building 151 is located within the OU6 area of concern, and samples of indoor air, sub slab vapor and outdoor air are collected every 3rd and 5th year in accordance with the ROD for OU6. USACE conducted sampling of indoor air, sub slab and outdoor air at Building 151 in February 2016; the results of which are presented in the above referenced July 2016 report from USACE. Currently, there is no complete vapor intrusion pathway; however, a vapor intrusion exposure pathway is potentially present under a portion of Building 151 near sub-slab monitoring points VMP173 and VMP161 where sub-slab concentrations of TCE are in exceedance of USEPA Regional Screening Levels for sub-slab soil vapor calculated using the USEPA vapor intrusion screening level calculator for commercial space. Monitoring point locations are shown on the attached Figure 1 for reference. The potential for a future exposure pathway exists in the portion of Building 151 that overlies these “hotspots” if a crack were to develop in the slab or the slab was penetrated in another way.

The overall objective of the SSDS is to mitigate the potential for future worker exposure to vapors originating from the OU6 groundwater plume in Building 151. The specific performance objectives of the SSDS include:

Mitigation of the risk of future vapor intrusion of volatile organic compounds (VOCs) into Building 151 from the OU6 groundwater plume, by inducing a negative pressure field directly beneath the slab of the building near vapor monitoring points VMP161 and VMP173. TCE concentrations were detected by USACE at these locations at 9,136 ug/m3 and 101 ug/m3, respectively which exceed the applicable screening level of 100 ug/m3. The area requiring mitigation is defined by the area encompassing these monitoring points, shown on Figure 1.

Guidance documents from the USEPA Region 5 (2010) indicate a pressure differential of -0.004 to -0.005 inches of water (iw) is sufficient to mitigate the vapor intrusion pathway. The VADEQ does not provide specific guidance on acceptable differential pressure for building mitigation. A conservative vacuum of 0.010 iw will be used as the design objective in the area requiring mitigation to ensure that under all building conditions (changes in barometric pressure, changes in heating and cooling set-points, doors open, doors closed, etc.) the minimum 0.004 iw is maintained during changes in barometric pressure, changes in heating and cooling set-points, when doors are closed, etc.

DESIGN PACKAGE ELEMENTS

SSDS Layout Overview

As discussed in the Design Approach Technical Memo (Attachment 1), the Building 151 SSDS design and installation will be conducted utilizing an adaptive design/build approach based on field testing. The design package was prepared based on what Arcadis believes to be the most likely outcome of the adaptive design process, utilizing two SSDS vacuum points connected to a single variable speed SSDS fan. Initially a single SSDS vacuum point, located inside of the break room will be installed and tested utilizing temporary vacuum test points (small holes drilled through the concrete floor) to determine the vacuum radius of influence (ROI) of the point. The layout of the SSDS system is shown in the attached Figure 1. Additional SSDS points may then be added as necessary during communication testing to achieve the performance objectives of 0.010 iw in the area requiring mitigation. These additional points (Vapor Pins) will be located in the southwestern most and southeastern most of the mitigation area, and an additional optional location inside the tool room.

G:\Projects\02118 USACE-Baltimore\201.0001 - DSCR\Tech Memos\Building 151\SSDS Design\Final\FINAL OU6 Bldg 151 SSDS Design_1.22.18.docx Page:

3/7

MEMO

The design package prepared assumes that the placement of these two SSDS vacuum points will be adequate to achieve the objectives; one vacuum point is located in the corner of the break room (inside of the main building, near the western wall), and one inside the tool room (outside of the main building).

These locations were chosen based on the assumption that the footer under the wall separating the tool room from the main building would prevent vacuum from propagating from one side to the other. However, testing will determine if vacuum from one point is sufficient to cover both areas, or if additional points are required to provide adequate vacuum to the area requiring mitigation. The fan shown in this design package is an OBAR 76SOE which has a potentiometer-controlled 350-watt motor that can be used to vary the fan speed to increase or lower the air flow as necessary to suit the number of vacuum points installed. The actual fan to be used for this system will be selected after completion of vacuum communication testing, done as part of the installation. The OBAR fan shown on the design drawings was selected for the purposes of sizing the piping and the electrical demand, as it is capable of supplying the necessary vacuum for up to 4 vacuum extraction points at maximum speed (16 iw maximum vacuum or 115 scfm maximum flow). This was done so that the installed infrastructure is expandable if more vacuum points are needed.

The conceptual layout of the SSDS system is shown in Figure 1. A conservative 40-foot (ft) ROI is assumed for each extraction point. The locations of the SSDS extraction points and vapor monitoring points shown on this figure are conceptual. More (or fewer) vacuum points may be necessary, and or the locations may need to shift depending on the outcome of the adaptive design testing as discussed above to provide adequate vacuum to the area requiring mitigation shown on Figure 1.

Vapor monitoring is included as part of the design approach. The design will use existing vapor monitoring points (VMPs) in Building 151 and in the break room. One additional new VMP in the tool room will be installed to monitor vacuum influence in this area. The design will recommend use of these VMPs to demonstrate vacuum influence of greater than the design objective of 0.010 iw.

SSDS Blower and Process Flow

The design includes a piping and instrumentation diagram (P&ID) as Figure 2. This P&ID drawing provides a diagram of the process flow and identification and specifications for all major components, instrumentation, as well as the materials of construction for the SSDS. As shown on the P&ID, the SSDS will include vacuum gauges that will display the applied vacuum at each vacuum point, and a low vacuum alarm light that will illuminate if the vacuum falls below the design level, indicating a fault with the SSDS equipment. The purpose of the P&ID as well as the detail drawings discussed below is to provide specifications for the major equipment, materials of construction, and the desired configuration to the installation contractor and the electrician.

SSDS Construction Details

Figures 3 and 5 of the design package are construction details drawings which provide the desired orientation of the equipment and design of the vacuum extraction points. Figure 3 shows the orientation of the radon mitigation-style fan installed outside of Building 151, above the roof of the tool room with the system discharge placed above the roofline and away from vents or windows on the building. It is anticipated that no vapor treatment devices will be necessary based on the soil vapor concentrations noted under the building. Table 1, included in this design package, shows the anticipated concentrations of TCE in soil vapor utilizing the concentrations detected in the most recent sub-slab soil vapor samples compared to VDEQ air permitting threshold. As shown on the Table 1, the anticipated concentration of TCE in the SSDS discharge is approximately 0.0012 lbs/hr. This is six orders of magnitude less than the

G:\Projects\02118 USACE-Baltimore\201.0001 - DSCR\Tech Memos\Building 151\SSDS Design\Final\FINAL OU6 Bldg 151 SSDS Design_1.22.18.docx Page:

4/7

MEMO

VDEQ air permit threshold of 22.8 lbs/hr. No air permit or carbon treatment of the SSDS discharge is required or planned as a result.

The construction details drawings include the following extraction point and SSDS details:

Extraction points will consist of a 12-inch (in) hole drilled through the slab with an open void (12 to 18 in radius) created beneath the slab by removing underlying materials with a trowel. Pea gravel will be used to backfill the hole.

Vertical extraction piping will consist of 4in Schedule 40 steel, transitioning to Schedule 40 PVC at about 5ft above the floor. The steel pipe at the base of the extraction points will be used to prevent points from being damaged by vehicle maintenance operations in Building 151.

Lateral conveyance piping will consist of 4in Schedule 40 PVC.

The piping has been sized based on the anticipated friction losses calculated in Table 2. As shown in the table, friction losses are negligible at the specified flow rate utilizing 4in pipe.

The fan will be located above the toolroom, with the discharge placed above the roofline and away from any vents, doors and windows.

The discharge pipe will end with a rain hat above the roofline of the building to keep out rain and debris.

Communication testing will also consist of a visual inspection of the design area, followed by measurement of the background differential pressure beneath the building with a micromanometer to determine the existing pressure to be overcome by the system vacuum.

The planned extraction point near the western wall of Building 151 is included in the design on Figures 4 and 5 which depict a typical vacuum point installation.

The tool room vacuum point (or any other additional extraction points) will be installed in the same mobilization, and located based on the results of communication testing utilizing the first extraction point.

All extraction points will be located, away from doorways, windows, and other spaces that require direct access.

Conveyance piping will be installed to maintain a slope that travels back towards the vacuum point in all areas. No low spots or traps will be permitted in the installation. This approach will prevent trapping of condensing water in the piping to reduce the amount of O&M needed and maximize performance and up-time.

Each vacuum point will also have an applied vacuum gauge, a low vacuum indicator light, a gate valve to shut-off or limit vacuum (may be necessary during testing), and a sample port to collect samples of extracted sub slab vapor.

The vacuum points will be constructed of schedule 40 steel at ground level, to about 5ft above the floor to protect them from damage due to vehicle maintenance operations in Building 151. The remainder of the installation above 5ft will be schedule 40 PVC.

All penetrations shown through walls must be caulked using Sika Flex 1A caulking. All penetrations through roofing must be sealed using roof-vent flashing with a high-performance rubber boot and sealer.

G:\Projects\02118 USACE-Baltimore\201.0001 - DSCR\Tech Memos\Building 151\SSDS Design\Final\FINAL OU6 Bldg 151 SSDS Design_1.22.18.docx Page:

5/7

MEMO

SSDS Electrical One Line Diagram

The electrical one-line drawing on Figures 6 through 8 provides the details, materials and specifications for the electrical portion of the installation. As shown on Figures 6 through 8, the SSDS fan will be connected to a dedicated breaker inside of an existing electric panel located inside of Building 151 on the Western wall near the tool room. A separate electric meter will be provided along with a shutoff switch.

While the SSDS fan itself will be located on the exterior wall of Building 151 above the tool room, the shutoff switch and electric meter will be located adjacent to the electric panel on the western wall of Building 151 at eye level. This will allow the system to be turned off from ground level for servicing, and will allow the DLA to track the SSDS electrical usage easily. The total electrical demand as well as the power requirements are provided on the one-line drawing.

Adaptive Design Approach and Communications Testing

As discussed in the design approach technical memo, an adaptive approach is necessary to fit the design to the specific characteristics of the sub-slab environment. Building foundations, slab construction, subsurface geology, and other features can limit vacuum influence. Therefore, communications testing is recommended as part of the adaptive design approach which will allow for additions and/or relocations of extraction points, and using the appropriate applied vacuum based on testing results. This approach involves conducting communications testing with the radon fan specified, and completing the installation during testing based on the results of the testing. The following is the testing approach to be utilized during the design/build of the SSDS for Building 151.

Communication testing steps:

Inspect floor slab in the Area Requiring Mitigation for any cracks or other penetrations through the slab. All cracks and penetrations should be sealed using Sika Flex 1A sealant.

Drill a 12in hole through the slab at the proposed extraction point near the break room location using a core drill.

Utilize existing vacuum monitoring points as available inside the building during the communication testing.

Install additional temporary sub-slab sample point(s) as needed to support communication testing.

Install temporary sample point(s) by drilling small holes (0.25 in diameter) through the slab, inserting tubing, and sealing around tubing with modeling clay. These temporary points should be distinguished as different from the permanent vapor monitoring points in the area.

Install the break room vacuum point as specified in the design, connect the SSDS fan to it temporarily at ground level using a 120 plug and heavy-duty extension cord, and operate at the maximum applied vacuum.

A PID should be used to monitor concentrations of VOCs in the breathing zone to ensure that VOCs are below 5ppmv in the breathing zone at all times during the test.

Use PID to monitor effluent air VOC concentrations during testing from the SSDS blower during testing.

G:\Projects\02118 USACE-Baltimore\201.0001 - DSCR\Tech Memos\Building 151\SSDS Design\Final\FINAL OU6 Bldg 151 SSDS Design_1.22.18.docx Page:

6/7

MEMO

Connect tubing from the temporary sub-slab sample point to the positive port of a micromanometer. Record the sub-slab pressure field extension reading, including the positive or negative sign.

o If a negative pressure of at least 0.010 iw is not obtained with the doors open) at each sub-slab sample point, identify areas that may need to be sealed. If possible, seal and repeat the test.

o If after sealing cracks, the desired negative pressure is not obtained at each sub-slab sample point, identify and install a second extraction point location closer to the area that was not being covered, and repeat the test utilizing the SSDS fan temporarily connected to the secondary extraction point.

After testing is complete, remove the tubing and clay from the temporary sub-slab sample point(s) and seal them using Sika Flex 1A sealant.

Complete the installation of the permanent SSDS including finishing the vacuum points(s), installing the risers, header pipes, permanent SSDS fan, and the remainder of the mitigation system.

This communication testing / adaptive design will determine if additional extraction points are necessary beyond the proposed two. A conference call will be held with the project team at the completion of the communication testing to apprise USACE and DLA of the recommended number of points and locations for the completion of the SSDS installation. It is anticipated that the communication testing and completion of the installation will accomplished in the same mobilization with no lag time between them.

Elements of the Final Design Package/As-Builts

Since the SSDS will be installed as part of the communications testing in an adaptive design approach, the final design will be an As-Built drawing package, prepared simply to document the completed installation. The final design package will contain the same elements from this draft design package, with any changes that were necessary as a result of the communication testing or to address comments from USACE or DLA.

Vacuum Monitoring

Vacuum monitoring at existing points and the installation of a new VMP in the tool room are included in the design. The following VMP installation specifics will be recommended and shown on Figure 5:

The VMP should be installed a minimum of 5ft from an exterior wall (10ft preferred). Location must be cleared for buried utilities.

The VMP should be assembled utilizing the same methods detailed and with the same materials specified in Attachment 2 (SOP for Vapor Pin Installation).

If present, carefully pull back carpet or vinyl flooring. Remove dirt and debris from concrete using a wire brush.

Install the Vapor Pin following the step by step instructions provided in Attachment 2.

When finished, place nickel-plated plug over hole to prevent debris from entering the hole. Clean concrete dust and debris from area using a shop vacuum or dust broom/pan and damp paper towel. Replace carpet or tile if present.

G:\Projects\02118 USACE-Baltimore\201.0001 - DSCR\Tech Memos\Building 151\SSDS Design\Final\FINAL OU6 Bldg 151 SSDS Design_1.22.18.docx Page:

7/7

MEMO

Wait at least 24-hours before using the new VMP.

The new and existing VMPs will be cited in the design for use in demonstrating the vacuum influence of the SSDS in the mitigation area. The design will provide recommendations for monitoring to confirm proper SSDS operation as part of routine O&M.

Verification Monitoring

One month after the successful installation of the SSDS, verification monitoring will be completed in the areas of the building that were mitigated to ensure that the SSDS is operating as intended. Vacuum will be monitored on VMP-161, VMP-162, VMP-173, and the new vapor pins installed in the tool room, using a micromanometer to verify that subslab pressure is less than the pressure above the slab. Results of the monitoring will be documented.

PAINT SHOP AND

PAINT BOOTH

LAUNDRY

OFFICE

H A

L L

VEHICLE

MAINTENANCE

BAYS

TRENCH

SUPPLIES/

REFERENCE

LIBRARY

SUPERVISOR

OFFICE

VMP172

VMP170

VMP171

SSDS EXTRACTION

POINT 2

OFFICE

(ASBESTOS

TILES)

SSDS FAN MOUNTED ON OUTSIDE WALL OF

TOOL ROOM. ATMOSPHERIC DISCHARGE

LOCATED ABOVE ROOFLINE OF TOOL ROOM

SSDS VACUUM

HEADER PIPING

HUNG FROM

CEILINGSSDS

EXTRACTION

POINT 1

NEW TOOL ROOM VAPOR

MONITORING POINT

B A

T H

R O

O M

U T

I L I T

Y

TOOL

ROOM

BREAK

ROOM

CP-1

0.003

CP-2

0.000-0.002

CP-3

0.008

CP-4

0.006

CP-5

0.000

CP-6

0.004

CP-7

0.008

CP-8

0.003

VMP173

0.015

VMP162

0.006

0.004

IN WC

0.007

VMP161

0.010

FIGURE

BUILDING 151 LAYOUT OF

SUB-SLAB DEPRESSURIZATION SYSTEM

I M

A G

E S

G

E P r o

A e r i a l j p g

P r o

A e r i a l j

P r o

A e r i a l j p g

X R

E F

S

P R

O J E

C T

N A

M

C I T

Y

M i l w a u k e e

W

I

D

V

G

R O

U P

E

N V

B

C

M c K e o u h

P

C

O p t

M R e q d

T

M

B r a v e r m a n

L

Y R

O p t O

N

O

F F

R

E F

C U s e r s c m c k e o u g h

O n e

D r i v e

A

R C

A D

I S

B o c s U

S A

C

A L

T I M

O R

E D

S C

R

P r o g r a m

O p t i m i z a t i o n

D

W G

F i g s

R d w

Y

O U

T

V

E D

A

D V

E R

S

L

C

H

G

E S

E T

U P

P

D F

O

T S

T Y

L E

T A

B L

E

B

L A

C K

G R

A Y

C

O

T T

E D

M

C K

E O

U G

H

C

A R

O L

NOTES:

1. AERIAL PHOTO SOURCED FROM GOOGLE EARTH PRO,

IMAGERY DATE APRIL 5, 2016.

2. INTERIOR BUILDING CONFIGURATION IS APPROXIMATE

AND IS BASED ON A FIGURE PROVIDED BY

USACE-BALTIMORE TITLED, "VI INVESTIGATION FOR

BUILDING 151 INDOOR AND OUTDOOR AIR, AND

SUB-SLAB VAPOR SAMPLES."

N

LEGEND

VAPOR MONITORING POINT

NEW TOOL ROOM VAPOR MONITORING

POINT

COMMUNICATION POINT (TEMPORARY)

VACUUM READINGS, INCH WC

BAY DOOR

AREA OF VACUUM INFLUENCE

GREATER THAN OR EQUAL TO 0.004

INCH WC, DASHED WHERE INFERRED

AREA REQUIRING MITIGATION

SUB-SLAB DEPRESSURIZATION

SYSTEM

DEFENSE SUPPLY CENTER

RICHMOND, VIRGINIA

BUILDING 151 SSDS DESIGN

0.003

PIPING AND INSTRUMENTATION

DIAGRAM

FIGURE

I M

A G

E S

X

R E

F S

P

R O

J E

C T

N A

M

C I T

Y

M i l w a u k e e

V

G

R O

U P

E

C

M c K e o u

C

O p

R e q

E

M o v s e s i

R O p t O

N

O

F F

R

E F

G E

N V

C A

D M i l w a u k e e A

C T

C o n s t r u c t i o n D e t a i l s d

Y O

U T

V

E D

A

D V

E R

M

S

T

E C

G

E S

E T

U P

P

D F

O

T S

T Y

L E

T A

B L E

B

L A

C K

G R

A Y

C

O

T T

E D

M

C K

E O

U G

H

C

A R

O L

DEFENSE SUPPLY CENTER

RICHMOND, VIRGINIA

CONSTRUCTION DETAILS -

SSDS FAN

FIGURE

I M

A G

E S

X

R E

F S

P

R O

J E

C T

N A

M

C I T

Y

M i l w a u k e e

V

G

R O

U P

E

C

M c K e o u

C

O p

R e q

E

M o v s e s i

R O p t O

N

O

F F

R

E F

G E

N V

C A

D M i l w a u k e e A

C T

C o n s t r u c t i o n D e t a i l s d

Y O

U T

V

E D

A

D V

E R

M

S

T

E C

G

E S

E T

U P

P

D F

O

T S

T Y

L E

T A

B L E

B

L A

C K

G R

A Y

C

O

T T

E D

M

C K

E O

U G

H

C

A R

O L

NOTES

1. SLOPE HORIZONTAL LEGS DOWN TOWARD SUB-SLAB

HOLE, TO PERMIT CONDENSATE DRAINAGE.

2. HORIZONTAL PIPING SHALL BE SUPPORTED A MINIMUM

OF EVERY 6 FEET.

NOT TO SCALE

DEFENSE SUPPLY CENTER

CONSTRUCTION DETAILS -

BREAK ROOM SSDS POINT

FIGURE

I M

A G

E S

X

R E

F S

P

R O

J E

C T

N A

M

C I T

Y

M i l w a u k e e

V

G

R O

U P

E

C

M c K e o u

C

O p

R e q

E

M o v s e s i

R O p t O

N

O

F F

R

E F

G E

N V

C A

D M i l w a u k e e A

C T

C o n s t r u c t i o n D e t a i l s d

Y O

U T

V

E D

A

D V

E R

M

S

T

E C

G

E S

E T

U P

P

D F

O

T S

T Y

L E

T A

B L E

B

L A

C K

G R

A Y

C

O

T T

E D

M

C K

E O

U G

H

C

A R

O L

NOTES

1. SLOPE HORIZONTAL PIPES DOWN TOWARD SUB-SLAB

HOLE, TO PERMIT CONDENSATE DRAINAGE.

2. HORIZONTAL PIPING SHALL BE SUPPORTED A MINIMUM

OF EVERY 6 FEET.

NOT TO SCALE

DEFENSE SUPPLY CENTER

CONSTRUCTION DETAIL

DEFENSE SUPPLY CENTER

RICHMOND, VIRGINIA

BUILDING 151 SSDS DESIGN

FIGURE

I M

A G

E S

X

R E

F S

P

R O

J E

C T

N A

M

C I T

Y

M i l w a u k e e

V

G

R O

U P

E

C

M c K e o u

C

O p

R e q

E

M o v s e s i

R O p t O

N

O

F F

R

E F

G E

N V

C A

D M i l w a u k e e A

C T

C o n s t r u c t i o n D e t a i l s d

Y O

U T

V

E D

A

D V

E R

M

S

T

E C

G

E S

E T

U P

P

D F

O

T S

T Y

L E

T A

B L E

B

L A

C K

G R

A Y

C

O

T T

E D

M

C K

E O

U G

H

C

A R

O L

NOT TO SCALE

TYPICAL VAPOR PIN MONITORING POINT DETAIL

TYPICAL EXTRACTION PIT DETAIL

Building 151 SSDS Draft Design Table 1

Estimated Stack Emissions Rate July 12, 2017

Conversions

1 L = 0.003 m3

1 m^3 = 35.3 ft3 Conversion Equations

1 g = 1000000 ug ug m3 g lbs ft3 min lbs

1 ounce = 28.35 g m3 ft3 ug g min hr hr

1 g = 0.0022 lbs lbs hrs ton tons hr year lbs year

1 ton = 2000 lb

1 hr = 60 min

1 year = 525600 min

1 year = 8760 hrs

Potential vapor influent concentration based on highest VMP soil vapor concentration

9136 ug/m3 TCE ‐ Highest Concentration in VMP 168

Flow Rate

35 cfm SSDS Fan

Stack Concentration Calculation TCE

0.001196 lbs/hr

0.005237 tons/year

=xx

Notes:

VDEQ Exemption for TCE 22.8 lbs/hr and 38 tons/yr x x = x x x

Table 2 - SSDS Lineloss Calcs Client: DLA/USACE prepared by: CMD checked by: CMD revised:

Site Name: DSCR - BLDG 151 RED = User Edit prep. date: 06/26/17 chk date: 06/30/17 rev. date:

Site Location: Richmond, VA

References: [1] Civil Engineering Reference Manual (CERM) 10th Edition, Lindeberg.

[2] Engineering Tool Box.com [3] http://www.harvel.com/pipepvc-sch40-80-dim.asp [4] Crane Valves (1988). Flow of Fluids through Valves, Fittings, and Pipe - Technical Paper 410; Crane Valves; Signal Hill, California; 1988

Equipment Information: General Notes Blower Make and Model: OBAR 76SOE Power Type: 120V Power Requirements: 2.9A

Assumptions:

Description Variable Value Unit Notes

See "Quick Ref - compressible flow" tab for additional assumptions

Target System Parameters Target ROI ROI 30 ft Target Flow Rate per well QWELL 58 scfm Flow thorugh conveyance pipe # of Operational Wells # 2 --- Total System Flow Rate QTOTAL 116 scfm Flow through manifold only, do not include bleed air!

Target Vacuum at Wellhead VWELL 3 in w.c Blower Inlet Vacuum VBLOWER 0.3684598 in Hg Blower Inlet Vacuum VBLOWER 5 in w.c Starting Vacuum Well Furthest from Compund VEP-1 45 ft

Blower Through Manifold Sum of Straight Pipe Lengths

Description L Value Unit Notes Blower to Manifold L1 10 ft 4 in 0.69566 "w.c./100 ft 0.069566 " w.c.

Manifold Length L2 1 ft 4 in 0.69566 "w.c./100 ft 0.006957 " w.c.

Manifold to ground L3 35 ft 4 in 0.69566 "w.c./100 ft 0.243483 " w.c.

SUM 46 ft SUM 0.32001 " w.c.

Sum of Fittings (Equivalent Length Method) [2] & [3]See Ref tab Quantity Description Le Value Unit Notes

4 90o Elbow, long sweep radius 2.5 10 ft 4 in 0.69566 "w.c./100 ft 0.069566 " w.c.

2 Open Gatevalve 0.6 1.2 ft 4 in 0.69566 "w.c./100 ft 0.008348 " w.c.

0 Union 0.29 0 ft 4 in 0.69566 "w.c./100 ft 0 " w.c.

1 Tee Flow - Branch 6 6 ft 4 in 0.69566 "w.c./100 ft 0.04174 " w.c.

0 Tee Flow - Run 1.7 0 ft 4 in 0.69566 "w.c./100 ft 0 " w.c.

0 Ball valve (full open) 1.58 0 ft 4 in 0.69566 "w.c./100 ft 0 " w.c.

Inlet Loss 0 " w.c.

SUM 17.2 ft SUM 0.11965 " w.c.

Treatment Compound Instrumentation + Pipe to Wellhead Sum of Straight Pipe Lengths

Description L Value Unit Notes Subgrade Conveyance L1 0 ft 4 in 0.20154 "w.c./100 ft 0 " w.c.

SUM 0 ft SUM 0 " w.c.

Sum of Fittings (Equivalent Length Method) [2] & [3]See Ref tab Quantity Description Le Value Unit Notes

0 Tee Flow - Branch 7 0 ft 4 in 0.20154 "w.c./100 ft 0 " w.c. @Manifold 0 Reducer (2/1) 1 0 ft 4 in 0.20154 "w.c./100 ft 0 " w.c.

0 Open Gatevalve 0.6 0 ft 4 in 0.20154 "w.c./100 ft 0 " w.c.

0 90o Elbow, long sweep radius 2.5 0 ft 4 in 0.20154 "w.c./100 ft 0 " w.c.

0 Union 0.29 0 ft 4 in 0.20154 "w.c./100 ft 0 " w.c.

0 Tee Flow - Branch 6 0 ft 4 in 0.20154 "w.c./100 ft 0 " w.c. @wellhead

0 " w.c.

SUM 0 ft SUM 0 " w.c.

TOTAL 0.4 " w.c.

Vacuum Available @ Wellhead 4.6 " w.c.

Pipe Size Friction Factor [4] Frictional Loss

Pipe Size Friction Factor [4] Frictional Loss

Pipe Size Friction Factor [4] Frictional Loss

Pipe Size Friction Factor [4]

Each run: 20ft H + 20ft V = 40 total ft in length. 58 scfm/3 i.w., 4" Sch 40

PVC

Pipe material approximated as Sch 40 2" nominal pipe. Actually Sch 40.

2" Sch 40 ID is 2.047, and 2" Sch 80 ID is 1.913.

1.5" Sch 40 ID is 1.59.

Frictional Loss

\\arcadis-us.com\officedata\Wilmington-DE\Project\02118201.0001 - DSCR\OU6 BLDG 151 SSDS\Workplan\DRAFT OU6 Bldg 151 SSDS Technical Memo.docx

Arcadis U.S., Inc.

824 Market Street

Suite 820

Wilmington

Delaware 19801

Tel 302 658 1718

Fax 302 658 2068

Page:

1/6

MEMO

To:

David Hufford, CHMM

Defense Logistics Agency

Copies:

From:

Carlo M. DiTullio (Carlo.DiTullio@arcadis.com)

Date: Arcadis Project No.:

April 6, 2017 02118201.0001

Subject:

DSCR Building 151 Vapor Mitigation (Sub-Slab Depressurization) System Design/Build Technical Memorandum (Rev. 1)

This technical memorandum describes the scope and methodology for the design and installation of a sub-slab depressurization system (SSDS) at Building 151 located in the Operable Unit (OU) 6 area of concern within the Defense Supply Center Richmond (DSCR). The purpose of this system is to mitigate the potential for future vapor intrusion issues as described in the July 2016 Draft Subsurface Vapor Intrusion Monitoring Report, Building 151, prepared by the United States Army Corps of Engineers (USACE). Performance objectives and the design approach are discussed in this document, which has been prepared by Arcadis North America (Arcadis) under the USACE, Baltimore district Contract No.

W912DR-13-D-0016, Task Order No. 0001.

BACKGROUND AND PERFORMANCE OBJECTIVES

Building 151 is located within the portion of the installation occupied by the Virginia National Guard (VANG) and serves as their consolidated vehicle maintenance operations facility. The building consists of vehicle maintenance bays, sub-grade service pits, offices, a breakroom, toolroom and other facilities and is occupied by mechanics and supervisors during business hours. Building 151 is located within the OU6 area of concern, and samples of indoor air, sub slab vapor and outdoor air are collected every 3rd and 5th year in accordance with the ROD for OU6. USACE conducted sampling of indoor air, sub slab and outdoor air at Building 151 in February 2016; the results of which are presented in the above referenced July 2016 report from USACE. Currently, there is no complete vapor intrusion pathway; however, a vapor intrusion exposure pathway is potentially present under a portion of Building 151 near sub-slab monitoring points

\\arcadis-us.com\officedata\Wilmington-DE\Project\02118201.0001 - DSCR\OU6 BLDG 151 SSDS\Workplan\DRAFT OU6 Bldg 151 SSDS Technical Memo.docx Page:

2/6

MEMO

VMP173 and VMP161(168) where sub-slab concentrations of TCE are in exceedance of the Virginia Department of Environmental Quality (VADEQ) Tier III sub-slab vapor screening level for commercial space. Monitoring point locations are shown on the attached Figure 1 for reference. The potential for a future exposure pathway exists in the potion of Building 151 that overlies these “hotspots” if a crack were to develop in the slab or the slab was penetrated in another way.

The overall objective of the SSDS is to mitigate the potential for future worker exposure to vapors originating from the OU6 groundwater plume in Building 151. The specific performance objectives of the SSDS include:

Mitigation of the risk of future vapor intrusion of volatile organic compounds (VOCs) into Building 151 from the OU6 groundwater plume, by inducing a negative pressure field directly beneath the slab of the building near vapor monitoring points VMP161(168) and VMP173. TCE concentrations were detected by USACE at these locations at 9,136 ug/m3 and 101 ug/m3, respectively which exceed the applicable screening level of 29 ug/m3.

Recent guidance documents from the New Jersey Department of Environmental Protection (NJDEP 2013), USEPA Region 5 (2010) and a draft guidance from the Pennsylvania Department of Environmental Protection (PADEP 2015) indicate a pressure differential of -0.004 to -0.005 inches of water (iw) is sufficient to mitigate the vapor intrusion pathway. The VADEQ does not provide specific guidance on acceptable differential pressure for building mitigation. A more conservative vacuum of 0.010 iw will be used as the design objective to ensure that under all building conditions (changes in barometric pressure, changes in heating and cooling set-points, doors open, doors closed, etc.) the minimum 0.004 iw is maintained.

PROPOSED DESIGN APPROACH

Design Overview

The proposed path forward involves an adaptive design/build approach based on field testing. Initially a single SSDS extraction point will be installed and tested utilizing temporary vacuum test points to determine the radius of influence (ROI) of the SSDS extraction point. Additional SSDS points may then added as necessary during communication testing to achieve the performance objective of at least 0.010 iw in the area requiring mitigation. The conceptual design prepared assumes that the placement of up to two SSDS extraction points near the western wall of Building 151 will be adequate to achieve the objectives; one inside the corner of the break room, near the western wall of Building 151, and one inside the tool room. It is assumed that the footer on the western wall would prevent vacuum from propagating from inside the breakroom to the tool room. The adaptive design/build approach may be utilized however, to determine if vacuum from one point is sufficient to cover both areas.

The conceptual layout of the SSDS system is shown in the attached Figure 2. The design assumes a 40 foot (ft) ROI for each extraction point, assuming that vacuum propagation is hindered by the footer. The locations of the SSDS extraction points and vapor monitoring points shown on this figure are conceptual.

More or less points may be necessary, and or the locations may need to shift depending on the outcome of the adaptive design testing.

The design will include a radon mitigation-style fan installed outside of Building 151, above the roof of the tool room with the system discharge placed above the roofline and away from vents or windows on the building. It is anticipated that no vapor treatment devices will be necessary based on the soil vapor concentrations noted under the building. A description of the anticipated concentrations will be provided

\\arcadis-us.com\officedata\Wilmington-DE\Project\02118201.0001 - DSCR\OU6 BLDG 151 SSDS\Workplan\DRAFT OU6 Bldg 151 SSDS Technical Memo.docx Page:

3/6

MEMO

with the draft design so that EPA and VADEQ can provide concurrence that an air discharge permit is not required. The design will determine estimated concentrations of TCE in the effluent of the SSDS and identify any necessary permits. The fan is proposed to be connected to a dedicated breaker on an electric panel located inside of Building 151 near the tool room, but a separate electric meter will be provided along with a disconnect switch for ease of service, and tracking electrical usage.

Vapor monitoring is included as part of the design approach. The design will use existing vapor monitoring points (VMPs) in Building 151 and in the break room, and an additional new VMP in the tool room, to monitor vacuum influence. The design will recommend use of these VMPs to demonstrate vacuum influence of greater than the design objective of 0.010 iw.

Extraction Point Installation and System Design

The proposed design will include the following extraction point and system design details:

The design will recommend visual inspection of the design area, followed by measurement of the background differential pressure beneath the building with a micromanometer to determine the existing pressure to be overcome by the system vacuum.

Locations of two planned extraction points will be near the western wall of Building 151, one on either side of the footer, and away from doorways, windows, and other spaces that require direct access.

Extraction points will consist of a 6 inch (in) hole drilled through the slab with an open void (6 to 18 in radius) created beneath the slab by removing underlying materials with a trowel. Pea gravel will be used to backfill the hole if necessary for concrete support, but an open hole will be used as possible to provide the least amount of friction losses.

Vertical extraction piping will consist of 3 to 4 in Schedule 40 PVC.

Lateral conveyance piping will consist of 4 to 6 in Schedule 40 PVC.

Radon mitigation-style fan will be sized to achieve required vacuum based on background differential pressure, calculated line losses, and on-site communication testing.

The fan will be located above the toolroom, with the discharge placed above the roofline and away from any vents, doors and windows.

The discharge pipe will end with a 90 degree sweep elbow aimed away from the structure to keep out rain and debris while minimizing friction losses.

Elements of the Draft Design Package

The following elements will be provided as the draft design package, prior to communication testing:

Site plan showing the layout of the proposed extraction point(s) and conveyance piping, and VMPs

Piping and instrumentation diagram showing the plumbing of the SSDS, equipment, controls and alarms

Construction detail drawing(s) for the vapor extraction points, blower, piping penetrations and manifold/header

\\arcadis-us.com\officedata\Wilmington-DE\Project\02118201.0001 - DSCR\OU6 BLDG 151 SSDS\Workplan\DRAFT OU6 Bldg 151 SSDS Technical Memo.docx Page:

4/6

MEMO

Electrical one line drawings showing the electrical connections, disconnect, panels, load schedules, etc.

Tables showing the design calculations showing the flow and vacuum necessary to overcome friction losses and provide clearing of entrained water, and the SSDS equipment selected based on these calculations.

Brief technical memo with the description of the SSDS design documents, as well as anticipated operation, maintenance and monitoring requirements of the SSDS system.

Bill of materials for major equipment to be sourced for the installation.

Draft permits necessary for installation and operation of the SSDS system, if necessary.

This draft design package will be provided to the USACE and DLA for review, then for review to the regulators. It is anticipated that this draft design document will be a 90% submittal, meaning that it will be a complete document needing only minor modifications based on the results of the communication testing, and comments from USACE, DLA and Regulators to complete the communications testing and SSDS installation. In keeping with the adaptive design approach, this draft design package will be utilized to contract the work, but are not intended to be final construction drawings (i.e. the contractor doing the work will conduct the communication testing as part of the installation and move suction or vacuum points as necessary to ensure adequate SSDS coverage, with the approval of the engineer).

Adaptive Design Approach and Communications Testing

This adaptive approach is necessary to fit the design to the specific characteristics of the sub-slab environment. Building foundations, slab construction, subsurface geology, and other features can limit vacuum influence. Therefore, communications testing is recommended as part of the adaptive design approach which will allow for additions and/or relocations of extraction points, and appropriate fan sizing based on testing results. This approach involves conducting communications testing with the radon fan specified in the draft design, and completing the installation during testing based on the results of the testing. The following is the testing approach utilized during the design/build of the SSDS for Building 151.

Communication testing steps:

Drill a 6-inch hole through the slab at the proposed extraction point location using a hammer drill.

Install temporary sub-slab sample point(s) on opposite side(s) of the slab by drilling small holes (0.25 in diameter) through the slab, inserting tubing, and sealing around tubing with modeling clay.

These temporary points should be distinguished as different from the permanent vapor monitoring points in the area.

Connect a radon fan temporarily wired with a grounded plug, and connected to a heavy duty, GFCI120v extension cord, directly to the suction point. The fan should then be started to start vacuum to the suction point. A PID should be used to monitor concentrations of VOCs in the discharge of the fan and in the breathing zone to ensure than VOCs are below 5ppmv in the breathing zone at all times during the test.

Connect tubing from the temporary sub-slab sample point to the positive port of a micromanometer. Record the sub-slab pressure field extension reading, including the positive or negative sign.

o If a negative pressure of at least 0.010 iw is not obtained at each sub-slab sample point, identify areas that may need to be sealed. If possible, seal and repeat the test.

\\arcadis-us.com\officedata\Wilmington-DE\Project\02118201.0001 - DSCR\OU6 BLDG 151 SSDS\Workplan\DRAFT OU6 Bldg 151 SSDS Technical Memo.docx Page:

5/6

MEMO

If after sealing the desired negative pressure is not obtained at each sub-slab sample point, identify a second extraction point location closer to the area that was not being covered, and repeat the test.

After testing is complete, remove the tubing and clay from the temporary sub-slab sample point(s) and complete the installation of the suction points, radon fan, header, and the remainder of the mitigation system.

This communication testing / adaptive design will determine if additional extraction points are necessary beyond the proposed two. A conference call will be held with the project team at the completion of the communication testing to apprise USACE and DLA of the recommended number of points and locations for the completion of the SSDS installation.

Elements of the Final Design Package/As-Builts

Since the SSDS will be installed as part of the communications testing in an adaptive design approach, the final design will be an As-Built drawing package, prepared simply to document the installation. The final design package will contain the same elements from the draft design package, with any edits that were necessary as a result of the communication testing or to address comments from USACE, DLA or the regulators.

Vacuum Monitoring

Vacuum monitoring at existing points and the installation of a new VMP in the tool room will be included in the design. The following VMP installation specifics will be recommended:

The VMP should be installed a minimum of 5 ft from an exterior wall (10 ft preferred). Location must be cleared for buried utilities.

The VMP should be assembled utilizing the same methods detailed and with the same materials specified in the June 2016 Final Technical Memorandum on Building 72 Vapor Intrusion Monitoring Point Installation, by Arcadis.

If present, carefully pull back carpet or vinyl flooring. Remove dirt and debris from concrete using a wire brush.

Using a hammer drill and a 1” drill bit, drill down to approximately 2” depth of the wider portion of the VMP. The top of the assembled VMP should sit slightly below the floor when completed. Clean concrete dust out of the hole with small shop vacuum, bottle brush, or finger.

Using a hammer drill with a 3/8" or 7/16" bit, drill through the concrete slab. Record approximate width of concrete slab, soil type (silt/clay/sand) and moisture content.

Clean concrete dust and soil from inside the hole with finger and damp paper towel. Do not use shop vacuum inside the hole once broken through the concrete. Moisten concrete inside of the hole for better grout adhesion.

Fit assembled VMP into hole ensuring the top of the plug is just below the floor surface. Minimize the time the hole is open to the atmosphere.

Mix a small amount of non-shrink grout with distilled water. Mixture should be the consistency of a milkshake. Pour the concrete into the hole around the VMP to the bottom of the plug. Use a small disposable stir stick to remove any potential air bubbles in the wet concrete.

\\arcadis-us.com\officedata\Wilmington-DE\Project\02118201.0001 - DSCR\OU6 BLDG 151 SSDS\Workplan\DRAFT OU6 Bldg 151 SSDS Technical Memo.docx Page:

6/6

MEMO

When finished, place nickel-plated plug over hole to prevent debris from entering the hole. Clean concrete dust and debris from area using a shop vacuum or dust broom/pan and damp paper towel. Replace carpet or tile if present.

Wait at least 24-hours before using the new VMP.

The new and existing VMPs will be cited in the design for use in demonstrating the vacuum influence of the SSDS in the mitigation area. The design will provide recommendations for monitoring to confirm proper SSDS operation as part of routine O&M.

BLD15101

BLD15103

VMP173

VMP161 (168)

BLD15108

BLD15105

VMP162 (169)

BLD15104

BLD15102

VMP171

VMP172

BLD15107

VMP170

BLD15106

FIGURE

DATE

DRAWN BY

20160807

EOW

ditullioc Callout

VMP173

101 ug/m3 of TCE Subslab ditullioc Callout

VMP161 (168)

9,136 ug/m3 of TCE Subslab ditullioc Text Box Only samples with results above the VADEQ Tier III sub-slab vapor RSL for commercial space are presented.

BLD15101

PAINT SHOP AND

PAINT BOOTH

TOOL

ROOM

LAUNDRY

OFFICE

H A

L L

VEHICLE

MAINTENANCE

BAYS

TRENCH

SUPPLIES/

REFERENCE

LIBRARY

SUPERVISOR

OFFICE

VPM172

VPM170

VPM171

VPM173

SSDS EXTRACTION

POINT 2

VPM161(168)

9,136

VPM162(169)

OFFICE

(ASBESTOS

TILES)

SSDS FAN MOUNTED OUTSIDE OF

BUILDING 151 ABOVE TOOL ROOM.

ATMOSPHERIC DISCHARGE

LOCATED ABOVE ROOFLINE

SSDS VACUUM

HEADER PIPING

HUNG FROM

CEILING

SSDS

EXTRACTION

POINT 1

PROPOSED TOOL

ROOM SUB SLAB

MONITORING POINT 1

BREAK

ROOM

B A

T H

R O

O M

U T

I L

I T

Y

FIGURE

BUILDING 151

CONCEPTUAL LAYOUT OF

SUB-SLAB DEPRESSURIZATION SYSTEM

DEFENSE SUPPLY CENTER RICHMOND

RICHMOND, VIRGINIA

VAPOR INTRUSION FOR BUILDING 151

I M

A G

E

P r o A e r i a l j

P r o A e r i a l j

P r o A e r i a l j e o c j p g

X R

E F

S

P R

O J E

C T

N A

M

C I T

Y

M i l w a u k e e

V

G

R O

U P

E

C

M c K e o u

C

O p

R e q

M

B r a v e r m

R O p t O

N

O

F F

R

E F

G E

N V

C A

D M i l w a u k e e A

C T

F i g s d

Y O

U T

V

E D

A

D V

E R

M

S

T

E C

G

E S

E T

U P

P

D F

O

T S

T Y

L E

T A

B L E

B

L A

C K

G R

A Y

C

O

T T

E D

M

C K

E O

U G

H

C

A R

O L

NOTES:

1. AERIAL PHOTO SOURCED FROM GOOGLE EARTH PRO,

IMAGERY DATE APRIL 5, 2016.

2. INTERIOR BUILDING CONFIGURATION IS APPROXIMATE

AND IS BASED ON A FIGURE PROVIDED BY

USACE-BALTIMORE TITLED, "VI INVESTIGATION FOR

BUILDING 151 INDOOR AND OUTDOOR AIR, AND

SUB-SLAB VAPOR SAMPLES."

3. ONLY SAMPLES EXCEEDING APPLICABLE SCREENING

VALUES ARE PRESENTED ON THE FIGURE.

N

LEGEND

OUTDOOR AIR SAMPLE

SUB-SLAB SAMPLE

BAY DOOR

RADIUS OF INFLUENCE, ESTIMATED

AT 40 FT.

TRICHLOROETHENE, IN MICROGRAMS

PER CUBIC METER (µg/m