UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

REGION VIII

999 18th STREET - SUITE 500 ^ DOCUlTient ID

DENVER, COLORADO 80202-2466 &K':!?.S.,,imiiiiiiiiiiilll\llllllllllllll

2038092

FINAL POLLUTION REPORT

Midvale Slag OU2

Abandoned Wells

I. HEADING

Date:

Subject:

From:

To:

POLREP No,

2/3/97

Midvale Slag NPL Site

Mike Zimmerman, OSC _

Anne Spencer, EPA Headqu'art'ers

Emergency Response

FINAL POLREP - #2

(OU2) Abandoned Wells

II. BACKGROUND

Site No.:

CERCLIS No:

Response Authority:

State Notification:

Action Memorandum:

Start Date:

Completion Date:

71

UTD081834277

CERCLA

UDEQ Notified

07/26/96

10/3/96

11/8/96

III. SITE INFORMATION

A. Incident Category

Time-Critical, NPL

B. Site Description

1. Site Description

The entire Midvale Slag site consists of about 530

acres; OU2 covers about 200 acres of the Site. A smelter

operated on OU2 from 1897 until 1958. Over the years,, it

changed from a copper to a lead smelting facility, producing

gold/lead/silver bullion from sulfide ores. Five wells were

installed on OU2 in 1936 in the Deep Principal Aquifer for

the purpose of supplying water to the smelter. During the

demolition of the smelter in 1960, the surface casings of

Primed on Recycled Paper
the wells were damaged and several of the well heads were

covered with demolition materials. It appears chat the

wells remained in an unprotected condition for many years,

making it likely that surface water and windblown smelter

waste materials entered the casings.

2. Description of Threat

As a result of damaged/deteriorated surface casing of 5

wells on the OU2 site, surface water and windblown smelter

waste materials have entered the wells, and they now show

elevated concentrations of several metals, especially barium

and cadmium. Since there are abundant concentrations of

lead, arsenic, copper, silver, chromium, and zinc in the

slag, dross, and baghouse dust found on the Site from

previous smelter operations, it is possible that addition

metals could migrate into the wells in the future. Because

these wells may be acting as conduits for contamination to

the underlying aquifer, they will be abandoned and plugged.

C. Site Evaluation Results

During the EE/CA field investigation in 1993, the surface

casings for these 5 former water-supply wells were located. Two

of the wells were sampled and showed elevated concentrations

greater than the Maximum Contaminant Level (MCL) for total and

dissolved barium and cadmium. These elevated concentrations

might be accounted for by surface water infiltration due to

severely deteriorated well casings at the surface.

IV. RESPONSE INFORMATION

A. Situation

1. Current Situation

On October 3, 1996, the EPA ERCS Contractor mobilized

to the Site to begin the plugging and abandonment of the

five (5) wells. The well stems on the nine (9) monitoring

wells will be removed and the wells will be plugged and

abandoned. When this is completed it will remove a conduit

for contamination and an obstacle to future remediation.

2. Final Disposition

The plastic casing from the nine (9) monitoring wells

has been removed or "drilled up" during reentry drilling,

and the holes have been completely filled with a cementbentonite mixture. The removed plastic pile and cement

pads-short casings used for surface protection from the

monitoring wells are staged on-site.
Four of the five deeper (±350') water supply wells were

over-drilled with an overshot - i.e., a larger diameter

drill string with cutting teeth welded on the bottom joint.

The fifth well, which is located only a few feet from the

fourth, had been previously plugged and abandoned - the top

of the cement plug was encountered at 128' . Only 120' of

original casing was recovered from all four wells and it was

found to be badly corroded. The recovered pipe is also

staged on-site near the monitoring well's debris. The four

holes were completely filled with approximately 100 sacks of

the cement-bentonite mixture per well.

V. Cost Information

The costs to date are $113,260.49. The cost may increase

slightly after a survey verification of all well locations.
REGION Vm STATE AGENCY RRT CONTACTS

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If you have questions or a problem receiving this POLREP,

please call me at (303)312-6944. Thank you.

Steve Gunderson

Richard Bardsley

Tom EUerhoff

Jim Green

Doug Friez

Jeff Burgess

Leland Baron

Richard Smith

Neil Taylor

Dee EU Fifield

Lawrence Robinson

John Heller

Vern Schmit

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POLREP DISTRIBUTION LOG

Midvale Slag - Abandoned Wells

OSC' Mike Zimmerman

Polrep it Date Sent # nf Copies

1-Init. 11-14-96