September 11,

James Rogers

suite t 129 P.O. Chelmsford,

Re:

Dear Mr.

will Alternatives

meet,

Thank you.

Sincerely,

cc:

UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

REGION I

J.F. KENNEDY FEDERAL BUILDING, BOSTON, MASSACHUSETTS 02203·2211

1990

Silresim Site Trust 83 Parkhurst Road

Box 2100 Massachusetts 01824

Draft Comments on Revised Silresim FS-2

Rogers:

Attached please find EPA's draft comments on the revised Silresim deliverable FS-2 submitted July 13, 1990. Please note that EPA

not be requiring another revision of the screening of for this Site. However, we do expect that our

comments will be addressed for future deliverable&.

If you have any questions regarding our concerns, or would like to please contact me at (617) 573-9689.

!. • 1 , (_ __ _.. ~. { /Lt V;. Leslie McVickar Silresim Remedial Project Manager

Margar t Lesh n, CT Sup rfund S ction Chi f Ruthann Sh rm n, EPA ORC Rich rd Will y, EPA Hvrlrnl~i ~

Sarah Levinson, EPA Ri k As ssm nt Sp ciali t Evelyn Tap ni, MA DEP sua n Cooke, Goodwin Proct r & Ho r Charlie Lindb rg, GZA Bill Swanson, CD

SILRESIM EPA COKMEHTS ON THE REVISED PS-2

/ SEPTEMBER, 1990

1. Paqe 2, last para: Please qualify this statement by adding an additional statement onto the end, such as: "The discussion of groundwater cleanup goals presented herein focuses primaril the shallow overburden at the Silresim S

2. Paqe 4, second para: In the last sentence it is stated that the "more-likely scenario is considered to represent a more realistic evaluation of potential site risks" however it is alternately appropriate to indicate that it is "more-likely"because of the use of average concentrations.

3. Paqe s, second bullet: The statement in parenthesis should be eliminated. Ingestion of contaminated groundwater is a future pathway of concern, and no qualification is necessary or appropriate in Section 2.11, Protection of Human Health. You have included your opinion that this is an unlikely exposure scenario on page 13 under Section 2. 31, and elsewhere (page 9). It is unnecessary to repeat your recommendations anywhere else in this document.

Please keep in mind that if it should take 30+ years to remediate the site, as is you contend, the industrial nature of the area may have changed by that time. Also, the argument of low groundwater yield has not been properly developed. We do not know what the groundwater yield is for this area , therefore it is not certain that a single residence or small commercial/industrial establishment cannot be supported . Pl ase see comment numb r 7.

4. Paqe s, second main para:

a) Typo; "Based on the most r c nt water . . . "

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6. Paqe 7, second full para: In the last sentence please substitute "some protection" with ~~d.UYiii1flP~t§P.~:¢.'#!9.ti!1 ·

7. Paqe 9 1 first para:

a) Again, we do not know what the groundwater yield is. It is inferred that we have this information. If you are to continue with the non-potable water argument, you need to use some sort of scientific method (using current data such as permeabilities, well diameter, screen size, depth etc.) to support your premise that the aquifer is too unproductive to yield enough water for a single residence or small industrial or commercial operation.

Also, the appropriate place to voice your opinion regarding the non-potable water issue is on page 13, under Cleanup Options and

sentence in this with Recommended Cleanup Goals. Therefore lease ce the second

84 11b) It is believed that the sewers, especially the sewer are intercepting contaminated groundwater flow. One undiscussed possibility is discharge into the granular backfill materials in the sewer trench, acting as a "french drain". Has the possibility of contaminant migration along the sewer trench been considered?

I If it is agreed that this is a concern, the FS should briefly~ address this.

a. Paqe 13, last line on page: Please indicate that the cond,ominium units on Maple Street are also being sold as commercial units.

9. Page 14, third full para: Your dilution factors look about right, however please explain how you came up with them (i.e. include a brief explanation found in the RI).

10. Paqe 15: Both dioxin and PCB's are listed under the semi­volatile organics category. They should each be listed as separate categories.

11. Page 15, dioxin: In this paragraph you indicate that the health-based goal for potential carcinogenic effects is 0.000023 mg/kg. However in Figure 2-3 the note indicates that the risk based goal is 0 . 0023 mg/ kg. Please correct. Also, please eliminate the reference to Love C nal.

12. Page 16, PCBS: Wher as sites wh r non-r sidential our assumption i ha childr n com into contac wi h h oils. Q •

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th TSCA l

should be based on residential exposure. EPA 1 s newest pol icy indicates that a 1 ppm cleanup goal reflects a protective,quantifiable concentration for residential use soils. Because lower concentrations are not generally quantifiable, it is not necessary to evaluate the health based level of .46 ppm against the alternatives. This level should be the only one utilized in the evaluation of the remedial alternatives. Please see Attachment I.

13. Paqe 16, PAHsa Your recommended goal for cPAHs is 50 mgjkg, which is considerably higher than the health based goal of •31 mg/kg. Because PAHs cannot be strictly implicated as the source of this contamination, it is acceptable to look at background concentrations in developing cleanup goals.

we believe that the background data collected from the off-site areas of Silresim are much more representative of background for the Site than the information gathered via the literature study. Therefore, please use only the actual data gathered specifically for the purpose of determining background for the Site (Oct/Nov 1989) to develop a background cleanup level for both cPAHs and total PAHs. Please calculate the average concentration, as opposed to using the highest reported concentration. This background level should be the only level utilized in the evaluation of the remedial alternatives.

14. Page 18, arsenic: Because arsenic is a naturally occurring element in the soils, it is appropriate to establish a cleanup level based on background for the Silresim area, as opposed to utilizing the health based goal. Similar to PAHs, please calculate an average concentration from the data collected during the October/November 1989 background sampling effort. This background level should be the only level utilized in the evaluation of the remedial alternatives.

15. Page 19, lead:

a) Please provide a reference here to Figure 2-7 which illustrates the extent of lead contaminated soils exceeding the risk based goal of 2,500 mg/kg.

b) In the third paragraph it is stated that based on background information a cleanup level of 500 mg/kg is recommended, however, Figure 2-8 refers to a 500-1,000 mg/kg range. Do the areas on Figure 2-8 represent an exceedence of a lead level of 500 or 1000 ppm? I assume that it represents the 500 ppm, and that the legend needs to be corrected.

16. Page 20, last line: Please add a statement or reference to explain why there is no figur tor semi-VOCs or or PCBs exceeding th cl anup goals at River H adow Brook.

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18. Paqe 26, first full para: If 30 shallow wells at 0.5 to 0.75 gpm will yield between 15 to 22.5 gpm in total, then that leaves 5 to 7.5 gpm for the rock wells. The flow component for the deep wells is missing. Please include this information.

19. Paqe 33, Coat Evaluation: Please make note of the cost of importing soil for both the cap and to fill in those areas where contaminated soils would be excavated (and consolidated with on­site soils). The cost could be substantial and may factor into the final selection of an alternative.

20. Paqe 38, first full para: A volume increase of ·30% to 60% for solidification/stabilization seems somewhat extreme. Also, is there some reason why in-situ solidification/stabilization has not been considered or discussed in FS-2? Please address.

_) 21. Paqe 45/46, Section s. 62: In your evaluation of sc alternatives not employing in-situ vacuum extraction, you have expressed concern regarding the potential for serious VOC emissions during excavation. One possible solution, that has not been discussed, is a technique that has been utilized at the McKin Site. At McKin, 4.5 foot diameter caisson augers were used to excavate VOC contaminated soil to control volatilization. Following treatment for VOCs, soil could be stabilized and replaced in the auger holes. If the holes are augured in an alternating sequence, the s olidified treated material is self-supporting and works to prevent collapse of the material when subsequent holes are augured. Pleas valuate.

22. Paqe 46, second para: To minimize the volume of scrubber wat r r quiring tr atment, the water could be recycled rather than us d one through. Please evaluate.

23. laqe 52, last para: In the sixth line it appears that an unn c as ry word app rs , "· •. limited number of semi- and non-vol organic compounds would ... " Please correct.

2t. Paqe ss, tbird p ra: Pleas include the second parenthesis.

Th r ar ix HM lt rnatives (not five).

~(I) 01-4:zr I-4:;Q ZITI 1-4(1)(1)1-4 -I :I :;o ~0 -IX 1-411'1 <:I 11'11-4

0 :;o~ mr n · on :;oo o:;o,

FIGUBES

26. Figure 2-3 ' 2-4: These figures are not consistent. The volume of soils exceeding both the health based level and the TSCA levels for PCBs appears to be very similar. Please explain why, in many cases, the zone of PCB contamination exceeding the less stringent cleanup goal (Fig. 2-4) of 10 mg/kg is larger and/or does not overlap the same zones on Figure 2-3 that refer to the extent of PCB contamination exceeding the more stringent goal of .46 mg/kg? It looks as though two different people may have developed these diagrams, which leads me to wonder how arbitrary the methods were in establishing the zones requiring remediation.

TABLES

27. Tela 2-2:

a) MCLG's have recently been proposed for a new set of compounds. Some of these newly proposed MCLG's are indicator compounds for Silresim. Please see Attachment II and incorporate.

28. Tele 2-7: Lead, under Pol icy and Other should read 500, instead of 500-1000.

2t. Table 7-1 and 7-2: Please expand these tables for FS-3 to include a column to list advantages/disadvantages for each alternative.

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