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1 Document Separator DSO00 Document ID Number 38839

2 l innesot Po Oution Control gency 520 Lafayetle Road North I SLPauI, MN I I [ TTY I June 18, 2010 Ms. LeeAnn Thomas Manager Environmental Accrual - US Safety & Environmental Services Canadian Pacific 501 Marquette Avenue S., Suite 1525 Minneapolis, MN RE: Dworsky (D~vorsky-McFar and) S te, St. Anthony Blvd. and MN H\vy 47, Minneapolis MPCA Project Number VP7570 MDA Case File Number Monitored Natural Attenuation and Plume Stability Demonstration Plan Dear Ms. Thomas: The Minnesota Pollution Control Agency (MPCA) staffin the Voluntary Investigation and Cleanup (VIC) Program and the Minnesota Department of Agriculture (MDA) staff in the lncidenl Response Unit have reviewed the "Monitored Natural Attenuation and Plume Stability Demonslration Plan, McFarland-Dworsky Barrel Site" (the MNA Plan), prepared by Barr Engineering Company (Barr), dated October The MNA Plan pertains to the former McFarland wood-lreating and Dworsky Barrel drum-reconditioning site located on the northcentral portion of the Soo Line Shoreham Yard rail yard facility south of St. Anthony Boulevard and west of Central Avenue in Minneapolis (the Site). Regulatory oversight is provided jointly by both the MPCA VIC Program and the MDA Incident Response Unit of the Pesticide and Fertilizer Managemen! Division. This letter has been prepared to present joint MPCA and MDA review cmnments ou the MNA Plan. Site soil investigations and soil respouse actions conducted in 2005 and 2007 are discussed in other Site documents. The primary compounds of concern (COCs) lhat were addressed by the soil response actions were semi-volatile organic (SVOCs) associated with historic ~vood-treating activities at the Site. "Dissimilar soil" (i.e., dioxins and furans) contamination was also identified :rod addressed by the soil response actions. The MNA Plan was prepared to evaluate Site groundwater conditions and provide recommendations for future ground~vater monitoring activities. The COCs for the groundwater at the Site are chlorinated volatile organic compounds (VOCs) associated with the hisloric drum reconditioning and storage activities and naphthalene associated wilh the historic McFarland wood treating activities. Other SVOCs, although they comprised the majority of the soil contamination that was remediated, have not been identified in groundwater above drinking water criteria. The relevant drinking water criteria for the COCs at the Site are the Minnesota Department of Health (MDH) Health Risk Limits (HRLs). St. Paul [ Braiaerd [ Detroit Lakes ] Duluth I Mankato [ Marshall [ Rochester [ Willmar [ Printed on 100,6 post-consumer recycled pape~

3 Ms. LeeAnn Thomas Page 2 June 18, 2010 The two current monitoring wells at the Site are MW-202 and MW01-03-I; well MW-201 was abandoned in 2005 in order to complete soil excavation activities. Othi~r wells which have been used to historically monitor grotmdwater at or near the Site include the upgradient wells MW01-02-T and MW-107; the side- to down-gradient xvell MW-301 (CS), and the downgradient well MW01-04-T. All \veils are shallow water table wells (approximately 40 feet deep) except well MW01-03-I which is of intermediate depth (78.5 feet). The measured hydraulic gradient of the shallow aquifer at the Site aod surrounding area is relatively fiat ranging from to feet/lbot. Most typically the hydraulic gradient is to the south-southeast although some sampling events have identified a northward gradient. VOCs exceeding their respective MDH HRLs have been detected in wells MW-201 and MW These compounds inclade tetrachloroethene (PCE); trichloroethylene (TCE.); l,l,2- trichloroethane (1,1,2-TCA); 1,2-dichloroethane (1,2-DCA): and vinyl chloride (VC). Well MW , installed in 2001 also has consistently identified 1,1.2-TCA, 1,2-DCA, TCE and VC above their respective relevant MDH criteria. Naphthalene concentrations in well MW-202, were historically more elevated, hoxvever, concentrations have since decreased below the MDH HRL. The MNA Plan notes that the concentrations of these compounds have remained relatively stable since sampling was initiated in The VOCs and the naphthalene likely originated, respectively, from the Site s historical drum reconditioning and wood treating activities. Well MW01-04-T, installed in the downgradient direction, has detected VOCs at low concentrations but not at concentrations exceeding their respective HRLs and naphthalene has not been detected. Similarly, the side- to down-gradient well, MW-301(CS), has not detected VOCs or SVOCs at concentrations exceeding their respective drinking water criteria. Wells MW-202 and MW were sampled in March 2008 for dioxins and furans to determine if these compounds were present in either the shallow or intermediate Site monitoring wells along the downgradient edge of the soil excavation area. The calculated tetrachlorodibenzo-p-dioxin.(tcdd) equivalents from the samples \vere two orders of magnitude lower than the relevant groundwater criteria of 30 picograms per liter. Based on these results and the high sorptive capacity and low solubility of dioxins, these compounds are not considered COCs for groundwater. Mann-Kenda!l statistics were conducted to evaluate the concentration trend for the groundwater COCs for each of the Site monitoring wells using data collected through the spring of All results indicated either a stable or decreasing trend. The MNA Plan provides an evaluation of contamination trends using a groundwater transport model and concludes, using the Mississippi River as a hypothetical downgradient receptor, that groundxvater contamination from the Site, if it reached the river, would be significantly belo\v any relevant surface water criteria.

4 Ms. LeeAnn Thomas Page 3 June 18, 2010 The MNA Plan recommends that one additional monitoring event be conducted lbr wells MW- 202, MW01-04-T, and MW01-03-I during the spring o1"2010. The MNA Plan recommends that these sampling results be reevalaated using Mann-Kendall analysis and that no fi~rther groundwater monitoring be required if these additional results supporl stable or decreasing trends for the groundwaler COCs. The MNA Plan is hereby approved subject to the modifications provided in Attachment B. Please also note the standard disclaimers in Attachment A. If you have questions regarding this letter please contact either Andrew Nichols at or.robert Anderson at Sincerely, Andrew Nichols Project Manager VIC and Emergency Response Section Remediation Division Project Manager Agronomy and Plant Protection Division Minnesota Department of Agriculture RIVlJ/RA:j mp Attachments cc: Kevin Eisen, Barr Engineering Gayle Bonneville, Shoreham Area Advisory Committee Tom Frame, City of Minneapolis

5 ATTACHMENT A DISCLAIMERS Dworsky Barrel (Dworsky-McFarlmld) Site MPCA Project Number VP7570 MDA Case File Nu~nber I. Reservation of Authorities The MPCA Commissioner reserves the authority to take any appropriate actions with respect to any release, tlu eatened release, or other conditions at the Site. The MPCA Commissioner also reserves the authority to take such actions if the voluntary party does not proceed in the manner described in this letter or if actions taken or omitted by the voluntary party with respect to lhe Site contribote to any release or threatened release, or create an imminent and substantial danger to public health and welfare. 2. No MPCA Assumption of Liability The MPCA, its Commissioner and staffdo not assume any liability for any release, threatened release or other conditions at the Site or for any actions taken or omitted by the voluntary party with regard to the release, threatened release, or other conditions at the Site, whether the actions taken or omitted are in accordance with this letter or otherwise. 3. Letter Based on Current Intbnnation All stalements, conclusions and representations in this letter are based upon infommtion known to the MPCA Commissioner and staffat the time this letter was issued. The MPCA Commissioner and staff reserve the authority to modify or rescind any such statement, conclusion or representation and to take any appropriate action under his authority if the MPCA Commissioner or staffacquires information afler issuance of this letter that provides a basis for such modification or action. 4. Disclaimer Regarding Use or Development of the Property The MPCA, its Commissioner and staffdo not warrant that the Site is suitable or appropriate for any particular use. 5. Disclaimer Regarding Investigative or Response Action at the Property Nothing in this letter is intended to authorize any response action under Minn. Stat. 115B, 17, subd. 12. Page 1 of l

6 ATTACHMENT B MODIFICATIONS AND COMMENTS Dworsky (Dworsky-McFarland) Site MPCA Project Number VP7570 MDA Case File Number Section 2.3 mentions that MW01-03-T was installed aloag with MW The CP database has no record of MW01-03-T, and therefore this perhaps should have read MW01-04-T. Also, please nole the Barr reference for 2008c referenced in the title heading for Sectioa 2.9 does not exist, but refers to the Barr 2008b reference dated May 13, Tile Mama-Kendall analysis was conducted using a spreadsheet developed by the Indiana Department of Environmental Management (IDEM). Please note that this spreadsheet evaluation ases a set number of sample points (e.g., 0-8 Quarter; 5-12 Quarter: 9-16 Quarter Evaltmtions, etc.) and if sample results are not entered for an analysis period, the spreadsheet algorilhm interprets tbat as a zero and can provide an incorrect trend conclusion. If sampling data for a particular analysis period is incomplete, it should be noted that there is insufficient data to evaluale a trend using this spreadsheet. As an alternative, consider using a different statistical package or conduct the trend evalnatioa manually using a spreadsheet and the probabilily table. Alternatively, Jr you have more than l0 sample points, it is recommended that you consult the normal approximation as described in Section of the USEPA QA-G-9 updale, available at USEPA s Cleanup Information (CLU-IN) website at f/rio/past /g9-fiaal.pd f. The MNA Plan uses a grotmdwater model to evalnate whether tile groandwaler plume at the Site could result in impacts above the sarface water chronic standards at Ihe Mississippi River aad concludes that the predicted concentrations would not pose a risk to the Mississippi River. While Ihe M PCA stall" agree with this conclusion, the evaluation of groundwater conditions at the Site may have sufficient downgradient control as to make this evaluation unnecessary. VOCs have not been detected at couccntrations above their respective drinking water criteria in the waler lable wells located downgradient from the Site (wells MW-301(CS), MW01-04-T, and MW T). As a result, the MPCA caa conclude that the Site groundwater plmne at tile water table is limited in extent and is contained onsite. However, the plume extentaad stabili.ty in the intermediate depth portion of the shallow aquifer is not as well defined. The most recent results for well MW show detections of 1,1,2-TCA; 1,2-DCA; TCE and VC above their respective MDH HRLs. The MPCA staffrecommend that the wells used to evaluate the potential migration of the intermediate depth plume impacts be expanded to include MW and all appropriate facility-wide monitoring locations dowagradient of the Site. The M PCA staff will coasider proposals for termination of Site monitoring after additional sampling results have been evaluated using the Mann-Kendall analysis as proposed in Section 8.3 of the MNA Plan and the facility-wide groundwater monitoring trends are evaluated with modeling as appropriate to provide more support that the VOC contamination present in MW has not migrated signi ficaatly from the Site. I f this cannot be determined the M PCA slaff may request lhat anot her inlermediate depth monitoring well be installed or a push-probe advanced to confirm plume stability. As part of subsequent rbporting, please check for tile most carrent MDH drinking water criteria which can be found at The USEPA MCLs and other federal criteria along with the recommended state criteria can be found at: ht~p://w\vw.pca.state.mn.us/index.php/waste/waste-and-c~eannp/c~eaat~p-pr~grams-andtopics/topics/risk-bascd-site-evalaatiou-process-guidance-docun~euts.htn~l