UNITE D STATE S ENVIRONMENTA L PROTECTIO N AGENC Y

REGIO N VII I

9 99 18th STREE T - SUITE 500

DENVER , COLORAD O 80202-2466

"" 044S3O

NOV I 9 I992 Re£: 8HWM

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S R

 ADMINISTRATIVE RECORD

M s . An n Veigal , Projec t Manager 3-^' ^

Morrison Knudsen Corporation

Environmental Services Group

7100 East Belleview Avenue, Suite 300

Englewood, Colorado 80111

R E: EPA Comments on the.Responsiveness Summary For The Interim Draf t Lead.and Zinc Sla g Pile Remedial Investigatio n Reports , California Gulch NPL Sit e

Dear Ms. Veigal:

T he U.S . Environmental Protection Agency (EPA ) has reviewed

t he Responsiveness Summary for the Draf t Lead and Zinc Slag Pile Remedial Investigatio n (RI ) Reports. The comments listed below

reflec t discussions at the October 30, 1992, monthly meeting. One issue that needed to be addressed was the process for

incorporating the results of the metal speciation work into the

various remedial investigation reports. It i s EPA' s positio n

that every RI report that is submitted will serve as a standalone document describing the results of a particular RI

activity. Therefore , the Lead and Zinc RI Reports should be

resubmitted as final documents prior to receipt of metal

speciation results.

E PA COMMENT S ON RESPONSIVENES S SUMMARY FOR INTERI M DRAFT REPORT

F O R LEAD AND.ZIN C SLAG PILES :

Lead Sla g Pile RI Report

1. Response to General Comment No. 2 and Specifi c Comment No.15 ; Since inclusion.of data from other Sit e remedial

investigations (i.e. , hydrogeology, surface water,

residential soils , etc. ) is not within the scope of the

slag RI reports, then inclusion of results from the

metal speciatio n report are also considered out of this

scope. It i s EPA' s understanding that the Final RI

report would be distributed prior to obtaining the

metal speciatio n results. In the event that the

speciatio n results change conclusions that were derived

from the RI results , an addendum wil l be added to the RI report.

Printed on Recycled Paper
2. Response to General Comment No. 3: It is unlikely that the

subslag soil will be considered as background. Therefore , the inference that the soils could be

indicative of background conditions or that the subslag

results may be useful during background geochemistry

evaluation is not appropriate for inclusion in this RI

report. I t is'SlPA' s understanding that Morrison- Knudsen will coordinate with the authors of the Pre- Mining Geochemistry Work Plan to address this issue

further.

3. Response to General Comment No. 7; The Stat e and EPA remain

concerned with the process that was used to determine

maximum windspeeds at the site. The Stat e mentioned a study that was conducted at the East Helen a Sit e that

has potential applicatio n at California Gulch. EPA

assumes that CDH will follo w up with M-K on this issue.

4. Response to General Comment No. 8 and Specifi c Comment Nos .

46. 53. and 63; EPA accepts that the column leach test

results are the best estimates available and that the

number of cycles was predetermined in the work plan. However, lead concentrations were increasing at the end

of the column leach tests. Therefore , these estimates

cannot arbitrarily be considered as lower bounds. Furthermore, for the same reason one cannot assume that

potential maximum loading has been achieved, regardless

of whether or not the column leach tests hypotheticall y

overestimated metals leaching from the slag under field

conditions.

ZINC SLAG PIL E RI REPORT

1. Response to General Comment No. 7; Refer to Response N o. 3. above, pertaining to the Lead Slag Report.

2. Response to Page 6-4. Summary of Verificatio n of the Conceptual Model (Responsiveness Summary Page No. 17) ; An emission rate of 0.00 appears questionable. Thi s

equation should be verified for appropriateness and a

more applicable emission rate substituted, if one is

found.
If you have any questions regarding these comments, fee l

free to call me at (303 ) 293-1529.

Sincerely,

Denise Link Remedial Projec t Manager

cc: Russ Alien , CDH Bill Fieselman , Jacobs Engineering Nancy Mangone, EPA-ORC Kathlee n Snead, D&RGW Railroad