ENVIRON ENVIRONMENT & HEALTH

Mr. Heath Smith Federal On-Scene Coordinator U.S. Environmental Protection Agency 212 Little Bussen Drive Fenton, Missouri 63026

RE: Work Plan for Confirmatory Indoor Air Monitoring and Residential Sump Water Sampling SV Land LLC 611 East Seventh Street Washington, Missouri

Dear Mr. Smith:

Ramboll Environ US Corporation (Ramboll Environ) is submitting this Work Plan to the United States Environmental Protection Agency Region 7 (USEPA), on behalf of SV Land LLC, to perform confirmatory indoor air monitoring at two residences identified as Lots 153 and 176 in Washington, Missouri (the attached figure depicts the location of Lots 153 and 176). This Work Plan includes a brief background discussion, scope of work and schedule.

BACKGROUND DISCUSSION

SV Land LLC commenced investigation and monitoring at the former Sporlan Valve facility located at 611 East Seventh Street in 2006. SV Land LLC enrolled the Sporlan Valve site in the Missouri Department of Natural Resources (MDNR) Missouri Voluntary Cleanup-Program (VCP) in late 2007 after trichloroethene (TCE) groundwater impacts were characterized as potentially migrating off-site to the south towards residential properties. SV Land LLC was accepted into the VCP on February 15, 2008. SV Land LLC performed various investigations, demolished the former site building, continued groundwater monitoring at the facility and continued down-gradient groundwater and sub-slab vapor monitoring at residential properties (to assess vapor intrusion) with oversight from the VCP through April 2014. SV Land LLC withdrew from the VCP in April 2014 due to a technical issue unrelated to vapor intrusion; however, SV Land LLC committed to continue to perform annual groundwater and subslab vapor monitoring to continue assessment of vapor intrusion at residential properties. On April 15, 2015, SV Land LLC published the Annual Groundwater and Subslab Vapor Monitoring Report for the site. The subslab vapor results for the residential properties were below the residential risk based criteria published by the MDNR and utilized by the VCP [risk based criteria published in the Missouri Risk Based Corrective Action Guidance Document (MRBCA)].

Date September 29, 2015

Ramboll Environ 1807 Park 270 Drive Suite 320 St. Louis, MO 63146 USA

T +1 314 590 2950 F +1 314 590 2951 www.ramboll-enviroh.com

40497685

in inn 1/4

Superfund

ENVIRON

The MDNR Superfund Program performed an investigation without SV Land LLC's involvement between July 14 and 16, 2015 to assess vapor intrusion at residential properties. The MDNR investigation included sub-slab vapor, indoor air and basement sump water sampling at select residential properties where access was granted within the 600 blocks of East Seventh and Eighth Streets (residential properties south of the former Sporlan Valve facility). The MDNR compared the results of the July 2015 investigation with the USEPA Regional Screening Levels. On August 24, 2015, MDNR provided the results of the investigation to USEPA and SV Land LLC.

As a result of the MDNR sampling effort, two properties designated as Lots 153 and 176 were characterized with potential complete exposure pathways regarding vapor intrusion based upon the USEPA Regional Screening Levels (for reference, the results of MDNR's July 2015 investigation were below the MRBCA residential risk based criteria). SV Land LLC arranged for installation of subslab vapor mitigation systems at Lots 153 and 176 on September 10 and 16, 2015, respectively, based upon the results of the MDNR investigation. Lots 153 and 176 are depicted on the attached figure prepared by the MDNR.

This proposed confirmation sampling effort at Lots 153 and 176 includes collection of indoor air samples in the basement and main floor for both residences, a background air sample collected simultaneously while the indoor air samples are collected, collection of one replicate indoor air sample to assess laboratory quality assurance, and collection of basement sump water samples in each residence if water is present in the respective sumps.

We previously discussed performance of sampling at Lot 193; however, since this is a confirmatory sampling effort to assess the performance of the sub-slab vapor mitigation systems, sampling at Lot 193 will be addressed along with the other future tasks outlined in your September 17, 2015 Path Forward e-mail.

SCOPE OF WORK

Indoor air samples will be collected from the main living space and from the basement at Lots 153 and 176. Indoor air samples will be collected using 6L Summa canisters equipped with a laboratory supplied calibrated valve to facilitate collection of a sample during an approximate 24 hour sampling interval. The Summa canisters will be positioned to collect samples from the breathing zone level. At one location, a replicate sample will be collected by placing two Summa canisters next to each other and collecting these samples simultaneously. A background air sample will be collected from an exterior location to assess ambient air conditions during the sampling event. The background sample will be positioned at a secure, up-wind location of the respective exhaust points for the subslab vapor mitigation systems. A total of six 6L Summa canisters will be used during this sampling event.

The primary contaminants of concern for the vapor intrusion pathway have been established based upon the monitoring performed at the site and consist of TCE and degradation byproducts 1,1-dichloroethene (1,1-DCE), cis- and trans-1,2-dichloroethene (cis-l,2-DCE and trans-l,2-DCE), and vinyl chloride (VC). The air samples will be analyzed for these five volatile organic compounds (VOCs) by modified EPA Method TO-15 (SIM). The method detection limits for this analytical method are sufficient to facilitate assessment of the data in comparison to

2/4

UiULLfl! ENVIRON

the USEPA Regional Screening Levels. Laboratory analytical reporting limits may be modified based upon the laboratory analysis of the actual samples.

Certified clean Summa canisters will be obtained from and the laboratory analysis of the Summa canisters will be performed by Eurofins Air Toxics Inc. in Folsom, California. Summa canisters will be relinquished to the laboratory using standard chain-of-custody procedures.

If water is present in the respective residential basement sumps, a water sample will be collected from the respective sumps, if accessible. The sump water samples will be analyzed for VOCs using Method 8260. The sump water samples will be submitted to Teklab, Inc. in Collinsville, Illinois for analysis using standard chain-of-custody procedures.

Any investigation derived waste (limited to latex gloves) is expected to exhibit little if any impacts and will be disposed appropriately as a solid waste.

SCHEDULE

Ramboll Environ will contact the property owners and tenants for Lots 153 and 176 to schedule a convenient day for sampling to occur. We are attempting to schedule the sampling during the week of October 19, 2015 and we will update USEPA as we progress with scheduling the subject sampling. The field sampling event is expected to require two days to complete (i.e. one day to start sample collection using the Summa canisters and the next day to retrieve the Summa canisters). Laboratory turnaround for analysis of air and sump water samples will be approximately two weeks.

Ramboll Environ will prepare a letter summary report providing the results of the confirmatory monitoring event within three weeks of receipt of the laboratory data. The laboratory results presented in the letter summary report will be compared with the USEPA Regional Screening Levels. Separate letter reports will be prepared and provided to the respective property owners providing the results of the sampling for their respective properties.

-ooOoo-

3/4

Q3MQ££D ENVIRON

If you have any questions or need additional information, please feel free to call me.

Michael F. Ellis, PE Principal

D +1 314 590 2967 M +1 314 229 5617 mellis@environcorp.com

cc: Steven J. Poplawski, Bryan Cave LLP Kristen Nazar - USEPA Dan Nicoski - USEPA David Hoefer - USEPA Scott Hayes - USEPA

LIST OF FIGURES

Figure 1: MDNR Vapor Intrusion Map

Sincerely,

4/4

ENVIRON

FIGURE 1

MDNR Vapor Intrusion Map

Vapor Intrusion Sampling Results Sampling Conducted July 14-16, 2015

Sporlan Valve Washington, MO

Legend | | Location ID Number

• SporlanParcel

All VOCs < Reporting Limit

VOCs > Reporting Limits but < Screening Levels

VOCs between Screening Level and Action Limit

I VOCs > Action Limit

Created on August 17. 2015 by Michael Stroh. This map is located at M Supcrlund Sporlan SamplcRcsultsMup mxd

Base Map: Satellite Imagery Basemap. 2014.

Data Sources: ESRI

Although data sets used to create this map have been compiled by the Missouri Department of Natural Resources, no warranty, expressed or implied, is made by the department as to the accuracy of the data and related materials. The act of distribution shall not constitute any such w arranty. and no responsibility is assumed by the department in the use of these data or related mate rials.

Missouri Department of

Natural Resources

Division of Environmental Quality

Hazardous Waste Program