UNITE D STATE S ENVIRONMENTA L PROTECTIO N AGENC Y

REGIO N VII I

9 99 18th STREET - SUITE 500 DENVER , COLORAD O 80202-2466

8HWM-S R

370776

Ref:

ACTION MEMORANDUM

DATE :

SUBJECT :

FROM:

T O :

October 31, 1995

Request for Removal (Response ) Action at the California Gulch National Priorities Lis t Site , Leadville , Colorado: ACTION MEMORANDUM for a Time-Critical Removal Actio n for a Portion of Upper California Gulch, Operable Unit 4 of the Site .

S am Vance, 8HWM-SR

M ax H. Dodson Assistan t Regional Administrator Offic e of Ecosystems Protectio n

and Remediation

Final NPL Sit e ID # 29

CERCLIS ID # COD980717938

Category of Removal: Time Critical

ARSite Post-Decision T •'-'. - . P-^ FOI/ Work •rerforme' 1

"

File Plan tf 2,je> Keyword fV,'- ; l^

I . Purpose

Thi s Actio n Memorandum documents the Agency' s selection of a

removal (response) action described herein for Upper California Gulch (UCG), an area which has been contaminated

with tailings from historic mining and millin g operations. T he purpose of the proposed response action is to improve

the temporary system which is used to divert the flo w in Upper California Gulch to the Yak Tunnel Water Treatment Plant . Thi s system was installed pursuant to the Second Amendment to EPA Unilateral Administrative Order No. CERCLA- VIII-89-2 0 to conduct a treatabilit y study of OU 4 (UCG )

water. The system is designed to use excess treatment plant

capacit y to improve the quality of the discharge into

California Gulch downstream of the Yak Tunnel Water Treatment Plant .

T he Removal Actio n in UCG is consistent with the remedial

activities to be undertaken by EPA at OU 4. Final remedial

alternatives for all areas of OU 4 will be evaluated in the Feasibilit y Stud y (FS) an d Record of Decision (ROD) for OU 4. The ROD for OU 4 will ultimatel y determine whether

remedial actions beyond those response actions implemented

pursuant to this Actio n Memorandum are required. The

Printed on Recycled Paper
primary goal of this Removal Action is to reduce the risk to

the aquatic and terrestrial ecosystems by reducing the

release of contaminated material into the environment from UCG . T he Design Criteria for the diversion improvement are

outlined below:

O The structure will be temporary; expected

operatin g lif e is less than 5 years.

O Design and implementation of the diversion will be

consistent with any remediation at OU 4.

O Diversion of Upper California Gulch flow s to the Treatment Plant can be controlled.

O Sedimen t load from Upper California Gulch will be

reduced.

O The diversion embankment will be stabilized for

high flo w conditions.

O The existin g flume at CG-1, jus t upstream of the

diversion sediment pond, will remain in place

allowin g continued monitoring of UCG flows .

Removal alternatives to treat or otherwise directl y

remediate surface water or ground water in OU 4 have not

been evaluated in this Action Memorandum.

I I. California Gulch - Sit e Conditions an d Background

T he California Gulch Sit e was listed on the National Priorities Lis t on September 8, 1983. The Sit e is in a

mining area covering 16 1/2 square miles of a watershed

that drains along California Gulch to the Arkansas River. Startin g in 1859, the area was mined extensively for gold,

lead, silver, copper, zinc, and manganese. California Gulch

collect s runof f that drains numerous abandoned mines and

wastes from mining, millin g and smelting. Miners built the Yak Tunnel to drain water from the mine workings and to make

mineral exploration and development easier. Thi s tunnel

drains hundreds of miles of mine workings in its 4-mile

underground course and prior to installatio n of the Yak Tunnel Water Treatment Plant , discharged approximatel y 210

tons of various metals each year into California Gulch. Seventy-five known mill s dumped tailings into 5-6 miles of

drainages. Six impounded tailings dumps surround the Cit y

of Leadville . Many smelters, which are located around the

city, processed silver, lead and zinc at various times.
Heavy metal residues are present in much of the City . The Arkansas River which receives water from the California Gulch, has been classified as a recreational resource, and

is used heavily for irrigation, livestock watering, public

water supplie s and fisheries . Approximatel y 4,000 live in

nearby Leadville and Lake County (Se e Sit e Location Map - Figure 1) .

III . Upper California Gulch (UCG )

A. Background

A temporary diversion was constructed in California Gulch jus t above the Yak Tunnel Portal in 1993

pursuant to the Second Amendment to EPA' s UAO CERCLA N o. VIII-89-20 . It provided for the diversion of a

portion of UCG water to the Yak Tunnel Treatment Plan t

to conduct a treatabilit y study of the Yak Plant to

determine if its excess capacity could be used to treat U CG flows , including flow s from spring run-of f and

from periodic storm events. The 1993 study concluded

that the treatment plant could successfull y treat UCG water and remain in compliance with effluen t standards

set for the plant . Asarco continued to treat UCG water

during the 1994 and 1995 runof f seasons. High flow s

during the 1995 season overtopped the existing

diversion structure, and diversion of UCG water to the

treatment plan t was halted. Improvements to the

existing diversion structure are planned to continue

treating UCG water, as the treatment plant capacity

allows .

T he Yak Tunnel Water Treatment Plant was constructed to

treat discharge from the Yak Tunnel . The maximum

capacity of the treatment plant is approximatel y 1150

gallon s per minute (gpm) . The treatment plan t also

treats surface runof f and spring discharge that occur

at the treatment plan t site. Generally , peak flow s

emanating from the Yak Tunnel vary from 600 to 1100

gpm, but average yearly flow s are considerably less

than these peak limits . Combined plant site surface

runof f and spring discharge for the 1993 season was

well below the normal Yak Tunnel peak flows , at

approximatel y 450 gpm during the 1993 season.

T he shortfal l during average and peak flo w conditions

f or 1993 provided the treatment plan t with sufficien t

excess capacity to allow for treatment of at least a

portion of the UCG water. Typical peak flow s are in

t he range of 900 to 1500 gpm. Upper California Gulch

is generally dry except during spring runoff . Drawing
1 depict s the location of the diversion structure in

relation to the Yak Tunnel Water Treatment Plan, the Y ak Portal and other site features .

B. Sit e Characterization - Upper California Gulch

Characterization of the water qualit y in Upper California Gulch (UCG) was conducted in June of 1994. Five grab samples indicated the following:

Aluminum 11,200 to 21,500 ug/L

Arsenic 5 to 25 ug/L

Cadmium 120 to 240 ug/L

Copper 490 to 1,140 ug/L

Lead 247 to 1,240 ug/ L

Zinc 17,200 to 46,000 ug/ L

During the period Asarco was diverting and treating UCG flow s in the Yak Tunnel Water Treatment Plant , the

effluen t from the plant was monitored for compliance

with its permit limitations . No exceedences of the

permit limitation s occurred. For further information ,

refer to the "Upper California Gulch Treatabilit y Study , Sprin g 1994, (Jun e 1995). "

C. Other Action s to Date

T he response action proposed in this Action Memorandum

replaces and augments the temporary diversion

structures constructed i n 1993 pursuant to EPA' s Second Amendment to Administrative Order CERCLA-VIII-89-2 0

dated June 16, 1993.

D. Stat e and Local Authorities Roles

None.

I V. Threat s to Public Health or Welfar e or the Environment

If the diversion structure is not constructed, the sediment

a n d metals loadings from Upper California Gulch (UCG) to Lower California Gulch (OU 8) and the Arkansas River will

continue.
V. Endangerment Determination

Actual and/or threatened releases of hazardous substances

from the water in Upper California Gulch, if not addressed

by implementin g the removal action selected in this Actio n Memorandum, may present an endangerment to public health, or

welfare , or the environment. The release of significan t

quantities of contaminated materials will continue.

V I. Proposed Actions/Performance Standards/Estimated Cost s

A. Proposed Action s

1. Embankment Regrading

2. Spillwa y Construction

3. Sediment Pond Clean-out and Enlarging

4. Outlet and Drain Installatio n

5. Upstream Sediment/Debri s Control

6. Operation and Maintenance

These proposed actions are included in the attached Work Plan for Upper California Gulch Diversion Improvements, prepared b y Shepherd Mill , Inc. , Reference: SMI #01-253, dated October 9, 1995

B. Applicabl e or Relevant and Appropriat e Requirements

(ARARs)

1.0 Chemical Specifi c ARARs -

1.1 Clean Water Act - Sectio n 402 - NPDES/CDPE S

1 .2 Clean Water Act - Surfac e Water Qualit y Criteria (Stat e ARAR)

2 .0 Actio n Specifi c ARARs -

None.
3 .0 Location Specifi c ARARs -

3.1 Clean Water Act - Sectio n 404 - Dredge and Fil l

C. Performance Standards

The ARARs are being met through compliance with Performance Standards . The Performance Standards are

included in the Statement of Work and are summarized

below:

1. The designed and constructed response action shall

include provisions to ensure that there are no

visible emissions (dust ) during removal

activities.

2. The design shall contain requirements to ensure

that activities associated with this action shall

not adversely impact the operation of the Yak Tunnel Water Treatment Plant .

3. A long-term maintenance program may be implemented

if required by the Final Record of Decision for Operable Unit 4 (OU 4) to ensure the long-term

effectivenes s of the response action.

4. Operation and maintenance task shall be performed

as indicated in the Work Plan.

D. Projec t Schedule

T he response action is scheduled for completion during

t he 1995 field season.

E. Estimated Cost s

Thi s response action is being performed by Resurrection Mining Company.

VII. Expected Change in the Situatio n Should Actio n Be Delayed or N ot Taken

Should this removal action be delayed, or not taken, there

will remain potential risk of exposure to the public to

heavy metals contained in the sediments in runof f from Upper California Gulch and continued release of contaminated

sediments into California Gulch and the Arkansas River.
VIII . Outstandin g Polic y Issues

A Record of Decision will be issued selectin g the final

remedial action for Operable Unit 4 (OU 4) of this Sit e

afte r the response action selected in this Actio n Memorandum

is completed.

I X . Enforcement

Pursuant to the 1994 Consent Decree, Resurrection Mining Company has agreed to implement response actions for the OU 4 portion of the Site .

X. Recommendation

Thi s decision document represents the selected removal

action for the Upper California Gulch portion of OU 4 of the California Gulch Superfun d Site , in the Cit y of Leadville , County of Lake, Stat e of Colorado. It was developed in

accordance with CERCLA, as amended, and is not inconsistent

with the NCP. Thi s decision is based on the Administrative Record for the Site .

Condition s at Upper California Gulch meet the NCP Sectio n

300.415(b)(2 ) criteria for a removal and I recommend

approval of the proposed removal action.

APPROVAL

M ax H. Dodson Assistan t Regional Administrator Offic e of Ecosystems Protectio n

and Remediation

DISAPPROVA L

M ax H. Dodson Assistan t Regional Administrator Offic e of Ecosystems Protectio n

and Remediation
C O L\O R A D O

NOT TO SCALE

CALIFORNIA GULCH SUPERFUNb SITE

*••

l'H)jrt:t

664-OWO

RESWLOC.DWG

J.RAY

t)ntnm By: K.CONRATH

RESURRECTION MININ G COMPAN Y O N E UMtreO BAN K CENTE R 1700 LINCOLN STREE T DENVER. COLORADO •«<>)

Sralr

H/A

Dtltr

JUNE 1995

FIGURE 1

CALIFORNIA GULCH SITE

GENERAL LOCATION
SHEPHER D MILLE R

HCCRPORATe D SHEPHER D MILLE R

:NCCRPOFIATH D

•

/ A / /