Bureau of Remediation & Waste Management Technical Guideline for The Investigation of Utility Pole Storage Areas February 2021

Utility poles (aka telephone poles, power poles) are used to support overhead electric and other lines. These utility poles are typically made of and, over time, have been treated with a variety of preservatives to make them resistant to rot and insects. Utility pole storage sites have been located throughout the state. Utility poles are stored in racks that are commonly called ‘pole brows’. The brows have traditionally been made of treated utility poles and have historically been located over bare . Newer brows may be paved, with a containment berm and wood chips to absorb drippings from the stored utility poles. Dripping and leaching of preservatives from treated utility poles stored in pole brows, over time, can result in significant contamination in underlying soils. The suite of potential contaminants of concern in pole brow areas makes them fairly unique and requires special consideration when investigating these areas for risk assessment and remedial planning.

General Conceptual Site Model

Potential contaminants of concern (PCOCs) in utility pole storage brows are directly related to the various preservatives used to treat utility poles. tar , pentachlorophenol (PCP) and chromated arsenicals/chromated arsenate (CCA) have been the primary wood preservatives applied to utility poles. The production of PCP typically results in byproducts of polychlorinated dibenzo-p-dioxins (dioxins). The PCP is applied with a solvent, most commonly diesel. CCA is a water-soluble pesticide. Potential contaminants of concern related to these preservatives are:

- Pentachlorophenol - Polychlorinated dibenzo-p-dioxins - Petroleum related compounds - Polycyclic aromatic hydrocarbons - Arsenic - Copper - Chromium (including hexavalent chromium)

Dripping and leaching of preservatives from the treated utility poles to bare soil can result in significant concentrations of contaminants. Soil in contact with the pole brow structure will likely contain elevated levels of contaminants. The majority of these contaminants are not anticipated to be highly mobile in the environment and have been found to be primarily located in the near- surface soils (0-4 feet) in most of the utility brow areas investigated. However, the presence of significant petroleum contamination or other site-specific conditions, can result in increased mobilization of contaminants. Erosion due to runoff from pole brow areas can result in contamination outside of the brow extents.

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Investigation Approach

Utility pole storage sites often have more than one pole storage brow. Depending on the layout, construction and age of the brows it may be appropriate to treat multiple brows as one investigation area or it may be best to investigate each brow separately. For risk assessment purposes, it may be appropriate to consider several pole brow areas as a single exposure unit. Areas adjacent to the pole brows that warrant investigation should, in most cases, be investigated as a separate area(s). See the Maine Remedial Action Guidelines (RAGs), Attachment B for details on conducting a site-specific risk assessment. DEP prefers that Incremental Sample Methodology (ISM), be used for risk assessment and -remediation confirmation at pole storage brow sites. Refer to Maine DEP SOP RWM-DR-015: Incremental Sample Methodology for Site Investigation and Assessment. Waste disposal characterization should be conducted in accordance with the license requirements of the disposal/receiving facility.

Unless there is strong supporting documentation that rules out a PCOC at a specific site, initial site characterization should include testing for all PCOCs. If results of the initial site characterization confidently rule out a PCOC as being present at the site, the PCOC list may be updated for subsequent sample events.

An alternative dioxin characterization approach using concentrations of the single compound 1,2,3,4,6,7,8-HpCDD to estimate dioxin TEQs has been approved by the DEP and employed at several utility pole storage sites. This approach was evaluated in 2020 using data from several previously investigated utility pole storage sites. Appendix A of this document includes a detailed discussion of the approach and the full evaluation. The method uses a linear regression equation to calculate an estimated dioxin TEQ based on a measured 1,2,3,4,6,7,8-HpCDD concentration. While there appears to be a very good correlation between the dioxin TEQ and 1,2,3,4,6,7,8-HpCDD concentration for some sites, evaluation of data from other sites indicate a level of uncertainty. Consequently, this method may not be appropriate for evaluating future exposure risk for residential development or risk to sensitive populations (schools, nursing homes, child-care facilities). If this approach is proposed for a site, it is recommended that initial site characterization include testing for the full suite of dioxins so a site-specific comparison of the dioxin TEQ to the 1,2,3,6,7,8-HpCDD concentration can be made to evaluate the validity of the approach.

Test Methods

Contaminant(s) of Concern Suggested Analytical Test Method(s) Pentachlorophenol (PCP) Method 8270D/E, Method 8151A, Method 4010A (screening only) Extractable Petroleum Hydrocarbons (EPH) MA DEP EPH 04-2.1 Dioxins EPA 1613, Method 8290A, Method 4025 (screening only) Metals (As, Cr, Cu) Method 6010D, Method 6020B Hexavalent Chromium (CrVI) Method 7196A Polycyclic Aromatic Hydrocarbons (PAHs) Method 8270D/E

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Data Interpretation and Evaluation

Analytical results should be interpreted and evaluated in accordance with the Maine Remedial Action Guidelines (RAGs): https://www.maine.gov/dep/spills/publications/guidance/index.html.

Dioxin

Dioxin risk is evaluated relative to a single dioxin compound, 2,3,7,8-TCDD. For a given sample point, compound specific Toxicity Equivalence Factors (TEFs) are applied to analytical results for individual dioxins and the results are summed to get a total dioxin Toxic Equivalent (TEQ). This TEQ is compared to the applicable 2,3,7,8-TCDD RAGs. The TEFs to be used are those recommended in the EPA Regional Screening Levels (RSLs) - User’s Guide, section 2.3.5 Toxicity Equivalence Factors: https://www.epa.gov/risk/regional-screening-levels-rsls-users- guide - toxicity.

See Appendix A: Alternative HpCDD Dioxin Evaluation Approach, for a discussion of using concentration data for the single dioxin compound 1,2,3,4,6,7,8-HpCDD for estimating total dioxin TEQ.

Chromium

This guidance recommends analysis for both total chromium and hexavalent chromium. There are risk-based RAGs for trivalent chromium (Cr III) and hexavalent chromium (Cr VI), but no RAGs for total chromium. The Cr VI analytical results should be compared directly to the applicable Cr VI RAGs and the total chromium result minus the Cr VI result should be compared to the Cr III RAGs.

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Appendix A: Alternative HpCDD Dioxin Evaluation Approach

The Maine DEP has approved an approach employed at several utility pole storage sites using concentrations of the single compound 1,2,3,4,6,7,8-HpCDD to estimate dioxin TEQs. This approach was evaluated by the Department in 2020 using data from several previously investigated sites. The method uses a linear regression equation to calculate an estimated TEQ based on a measured 1,2,3,4,6,7,8-HpCDD concentration. The following linear regression equation was proposed for use at a pole storage site in 2020 and is based on data from three previously investigated pole yard sites. The R2 value for this equation is 0.9961, indicating very good correlation with the actual data from the three sites.

Log (TEQ) = 0.9637*Log(1,2,3,4,6,7,8-HpCDD)-1.3723

This equation was compared to linear regression equations from six previously investigated utility pole storage sites (Lewiston, Yarmouth, Belfast, Augusta, Brunswick and Farmington). The following plot shows the plotted linear regression equations for each site along with the above equation (labeled ‘Bridgton’).

The plot shows a relatively tight spread between the site-specific equations and fairly good agreement from site to site. R2 values for each of the site-specific linear regression equations are in the range of 0.99 to 0.95, indicating very strong agreement with the actual analytical data.

To test the proposed method, the Department applied the equation to real data from two pole yard investigation sites (Brunswick and Farmington). The following tables compare TEQs calculated from site analytical data (Analytical TEQ) and TEQs estimated based on the

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1,2,3,4,6,7,8-HpCDD concentration (Estimated TEQ). All concentrations in the tables are in units of ng/kg.

Brunswick Farmington 1,2,3,4,6,7,8- Analytical Estimated 1,2,3,4,6,7,8- Analytical Estimated HpCDD TEQ TEQ % Diff HpCDD TEQ TEQ % Diff 29 0.70 1.09 -55 67 60.37 2.44 96 51 1.25 1.88 -50 73 143.43 2.65 98 60 1.36 2.19 -61 130 5.08 4.62 9 180 8.75 6.33 28 340 11.43 11.68 -2 190 6.20 6.66 -7 1200 47.76 39.36 18 200 5.44 7.00 -29 1600 47.36 51.94 -10 220 7.83 7.68 2 1600 47.75 51.94 -9 230 6.30 8.01 -27 1700 54.99 55.07 0 250 8.83 8.68 2 1700 56.88 55.07 3 410 14.60 13.98 4 2400 83.13 76.77 8 430 13.08 14.64 -12 2600 76.35 82.93 -9 470 18.87 15.95 15 3000 84.78 95.19 -12 560 20.81 18.89 9 3700 107.33 116.51 -9 560 17.47 18.89 -8 3700 140.80 116.51 17 670 19.67 22.45 -14 4000 112.97 125.60 -11 690 23.22 23.09 1 5900 162.08 182.67 -13 700 28.20 23.42 17 7000 204.53 215.39 -5 740 26.29 24.70 6 20000 576.68 592.38 -3 1000 30.35 33.02 -9 1400 46.35 45.67 1 1400 41.86 45.67 -9 1500 50.16 48.81 3 1500 52.61 48.81 7 1800 58.95 58.18 1 2900 99.44 92.13 7 3200 109.29 101.30 7 4400 150.81 137.69 9

These tables show that, in general, the difference between the analytical TEQ and the estimated TEQ is less than 20% and often less than 10%. However, there are some samples where the estimated TEQ is clearly not representative of the analytical TEQ. In most cases where the method does not accurately estimate the analytical TEQ, the estimated TEQ is significantly larger than the analytical TEQ and; therefore, is overly conservative. For these data sets, the estimated TEQ underestimates the analytical TEQ by greater than 10%, approximately 15% of the time. The estimated TEQ underestimates the analytical by greater than 20%, approximately 7% of the time.

Looking at the site specific regression equations for the Brunswick, Farmington, Lewiston and Augusta sites, and the proposed method equation (Bridgton), a 1,2,3,4,6,7,8-HpCDD concentration that would trigger an estimated TEQ at or just above the 2018 Residential Soil

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RAG for TCDD shows relatively good agreement. The Augusta equation exceeds the RAG at the lowest 1,2,3,4,6,7,8-HpCDD concentration (~1,600 ng/kg) and the Farmington and proposed Bridgton equations exceed the RAG at the highest 1,2,3,4,6,7,8-HpCDD concentration (2,050 ng/kg). This difference of 450 ng/kg between the equations represents a difference in the estimated TEQ of approximately 15 ng/kg.

Based on this assessment, the conclusion is that this method of estimating TEQs in soil using 1,2,3,4,6,7,8-HpCDD analytical concentration data, at utility pole storage sites, appears to be appropriate for soil assessment and for post-remediation confirmation in most cases. Given the observed variability in correlation at some sites, this method may not be appropriate for evaluating future exposure risk for residential development or risk to sensitive populations (schools, nursing homes, child-care facilities). If this approach is proposed for a site, it is recommended that initial site characterization include testing for the full suite of dioxins so a site-specific comparison of the dioxin TEQ to the 1,2,3,6,7,8-HpCDD concentration can be made to evaluate the validity of the approach.

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