\ r UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

REGION I

J.F. KENNEDY FEDERAL BUILDING, BOSTON, MAIIACHUSEnS 0220S-2211

December 13, 1989

James Roqers Silresim Site Trust Suite f 129 83 Parkhurst Road P.O. Box 2100 Chelmsford, MA 01824

Re: Third Draft Remedial Investigation,EPA final comments

Please find attached EPA's comments on the third Draft Remedial Investigation (RI) report, submitted to EPA in September, 1989.

As you will find, our comments are minor. EPA would like to meet with you December 13 to discuss and agree upon these comments for incorporation into the final report. If the agreed upon comments are adequately addressed, EPA will then approve (in writing) the ,....._ Silresim RI for subsequent public release.

I The meeting has been scheduled for December 13, 10 AM, in the first floor conference room at 90 Canal Street.

Sincerely,

/1 t'.Jtu ~~~t ~ Leslie McVickar Silresim Remedial Project Manager

Enclosure

cc: Marc)aret Leshen, CT Superfund Section Chief Nar:-cy Bettinger, MA DIP Helen Waldorf, MA DEP Tia Conway, ORC John Zannos, HydrologistSarah Levinson, Risk Assessment SpecialistCharlie Lindberg, GZA

SILRESIH BPA COKKZNTS ON THIRD DRAFT REMEDIAL INVESTIGATION (t/89)

1 • Pq. 42, Tran~aissivityz It should be noted that where a flow thickness of 30 feet has been utilized as an avera9e for this calculation, the saturated thickness can be as much as 90 feet in certain portions of the Site.

2. Pq. 41, first full paraa Please note here that additional data on deep flow is forth~omin9.

.. 3. Pq. 47, 5.50 or Table 5-4z Please provide the calculations and input parameters (hydraulic 9radient, K, cross sectional area, etc.) for determinin9 dischar9e for each flow tube, either in the text or table. ·

4. Pq. 11, sectioD 1.431 Please note that the effects of DNAPL have not been incorporated into the model, and that the saturated thickness is assumed to be 30 feet (if accurate).

5. Pq. 133, 5tb paraz It is incorrect to state that "the magnitude of the adverse effect will be proportional to the sum of the ratios of the subthreshold exposures to acceptableexposures". The hazard index is not a measurement of the

,- magnitude of the adverse effect (the effect is not alwaysproportional to the dose). This point is an important concept of the risk assessment, therefore this statement should be revised (e.9. "the higher the hazard index, the greater the potentialadverse non-carcinogenic effect will occur").

1. Pq. 147,-aist Suamaryz Numerous risks were estimated usingthe linearized multi-stage model which has been approved by EPA for low doses. At high dose levels, such as was predicted for several exposure scenarios at the Site, this model breaks down and the one-hit model should technically be used to estimate risk (i.e. when risk levels exceed l/100). the one-hit equation for high carcinogenic risk levels is:

Risk • 1 - exp (- exposure x carcinogenic potency)

(where exposure is expressed as an average daily intake mg/kg/dayand the carcinogenic potency factor is expressed in (mg/k9/day) ·t)

Because EPA did not previously make note of this equation, and the inclusion of these calculations would not chan9e the conclusions of the risk assessment, it will suffice to state that any risk from the Site in excess of l/100 should be interpretedwith extreme caution, as the appropriate model for these risks was not utilized. We do feel, however, that this is an important point to note.

7. Table 1-11 Please include discharge values for each flow

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a. Table 7-CI Please indicate whether this table refers to data from the sur(ace waters of East Pond or River Meadow Brook.

t. Table 1-111 There is an error in the reporting of nickel as a Group A compound via the oral route of exposure. It should be listed as a Group D compound for this pathway of exposure.

10. Table 7-251 The age of the person having this exposure is identified as 18-65 years, whereas the exposure duration is cited as 70 years. This is inconsistent. Please delete or revise.

11. Table 7-so, Toxicity Valueaa Our last set of comments (f C9) indicat~d that it was not appropriate to use the AIC for lead of 1.4 ·x 10· mg/kgjday, because this is based on an old value. It doesn't appear that this comment has been addressed. Additionally, it appears that the evaluation of the risks posedby lead in the tables that follow have been dropped entirely.This is a major limitation which should be addressed.

12. Table 7-30 ' 7-311 These tables have not identified relevant toxicity values for trichloroethylene, PCBs, arsenic, methylene chloride, 2-butanone and possibly others. This is important because without them, risk estimates for relevant carcinogenic and non-carcinogenic effects via the inhalation and ingestion pathways cannot be generated (and have not). This needs to be done.

13. ~iqure 1-311 Please modify this figure so that each flow tube begins at the center of the mound (see attached diagram).

14. ~iqure 1-37 and Pg. 111 Although the 84" sewer is likely to be acting as a discharge point, the data (Figure 6-19) does not show that it is completely capturing the plume. Please include a reference to this in the text.

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U.S. FISH AND WILDL.IFE SERVICE

Ralph Pill Harketpla~e, 4th Floor

TO:

FRQ\1:

SUBJECT:

22 Bridqe Strflet Concord, New llampshire 03301-4901

Ms. Leslie ~ickar, IUM, ~ 10, 1989 Silresim Site, Lowell, MA

Kenneth carr, USflolS

Revised Draft RI for Sllresim

We have reviewed the 5ept:.eutler 1989 ReVised Dl:isft RI for the Sllresiln SUper1\ud Site in IDwell, Massachusetts, as requested. Fran our perspective, SCJDe of the JIX:ISt hlportant infoimatioo in the RI will be provided in an ad:Serdum that will ackb:ess the OJnOemS previously ~ by tn\A. Until :those data axe available, we camat prav"ide a definitive critique of the Revised Draft. However, we can ackb:ess several plints withcut the data that will be forthcanin:;J in the addentum. .. One area of iDproYement in the Revised Draft is the qualitative diSOJSSioo of terrestrial and acpltic habitats oo and adjacent to the site. '11le site is clearly physically inpacted by industrial, cxmnercial and residential activities that severely restrict the ares's wildlife habitat value. '1he limited habitat oo and imnediately adjacent to the site significantly reduces the potential for present or future adverse illpacts of the site to fish and wildlife resources. However, off-site fish and wildlife resources cculd be adversely affected by contaminants that may have migrated fran the site. \tlile we expect the fort:hc:anirq adden:!um to partially ackb:ess this issue, it is illp>rtant to note that the potential effects of a · site do not necessarily end at the site boundaries, especially when surface streams or rivers axe involved. If downstream depositiooal areas have received contaminants fran the site, they may nqrlre remediation.

Please provide us with a copy of the proposed addendum when it beoanes available.

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