Flat Top Mine

All POL/SITREP's for this site Flat Top Mine
Ludlow, SD - EPA Region VIII
Printer Friendly  |   PDF
Flat Top Mine - Removal Polrep

Region VIII

Subject: POLREP #5
Flat Top Mine
Ludlow, SD
Latitude: 45.8456780 Longitude: -103.3678530

From: Shun-Ping Chau, OSC
Date: 6/17/2014
Reporting Period: 06/11/2014 to 09/24/2014

1. Introduction
  1.1 Background
Site Number: 08RW    Contract Number:  
D.O. Number:      Action Memo Date:  
Response Authority: CERCLA    Response Type: Time-Critical
Response Lead: EPA    Incident Category: Removal Action
NPL Status: Non NPL    Operable Unit:
Mobilization Date: 10/1/2012    Start Date: 10/1/2012
Demob Date:      Completion Date:  
ERNS No.:    State Notification:
FPN#:    Reimbursable Account #:

1.1.1 Incident Category

Time-critical removal.

1.1.2 Site Description

The Flat Top Mine Site is northeast of the town of Ludlow, Harding County, South Dakota.  Uranium mining activities occurred around Ludlow in the North Cave Hills, South Cave Hills and Flint Buttes from the late 1950s to 1964 under the General Mining Laws and Public Law 357, which did not require any restoration.  The North Cave Hills and South Cave Hills are part of the Custer National Forest and subsequently owned by the United States Forest Service (USFS).  

Flat Top Mine is located in the Flint Buttes and is currently on private ranch land.    There have been two previous studies by the South Dakota School of Mines and Technology and the Oglala Lakota College around 2006 and 2007, but no clean-up activities have occurred at the Flat Top Mine. Location

The Site is located northeast of the town of Ludlow, in Harding County, South Dakota.  Mining activities in the 1950s affected almost 1,000 acres of land in the region.  The remnants of Flat Top Mine consist of a water filled pit approximately 1,200 ft by 500 ft. A series of smaller pits, test pits and trenches are currently located within approximately 10,000 acres of undeveloped land used for cattle and sheep ranching but also includes some residential structures. Description of Threat

Uranium, arsenic, vanadium and molybdenum, defined by CERCLA Section 101(14) as hazardous substances, are naturally occurring in the Flint Buttes area.  Previous mining activities removed the vegetation and top soil cover in certain areas and left large piles of waste materials and open pits that collect surface water.  Many of the waste material piles have been covered with vegetation, but humans, livestock and wild animals are exposed to higher than background levels of these hazardous substances found in water which collects in open pits.

1.1.3 Preliminary Removal Assessment/Removal Site Inspection Results

Site assessment work conducted in 2009 and 2011 showed that the highest concentration of contamination occurs at and around an old mine pit that is now the largest pond on the north side of an old highwall, approximately 0.5 miles north of the town of Ludlow.  Uranium was detected in soil sediments with concentrations up to 770 parts per million (ppm) and in surface water with concentrations up to 558 micrograms per liter (µg/L). EPA sets the safe drinking water standard for humans at 30 µg/L, and guidelines from several agricultural extension offices recommend a maximum concentration of 200 µg/L for livestock.    Other elements of concern with elevated levels in the surface water were arsenic with concentrations ranging from 457 to 536 µg/L, vanadium with concentrations ranging from 73 to 258 µg/L, and molybdenum with concentrations ranging from 894 to 1,730 µg/L.  The guidelines for livestock drinking water recommend a maximum arsenic concentration of 200 to 500 µg/L, maximum vanadium concentration of up to100 µg/L, and maximum molybdenum concentration of 300 to 500 µg/L.



2. Current Activities
  2.1 Operations Section
    2.1.1 Narrative

Planned removal action includes treating water from the largest mine pit at the Site, returning the treated water to its original use as livestock drinking water and/or pasture irrigation, backfilling and re-vegetating the pit, and drilling wells to replace the livestock water supply.

2.1.2 Response Actions to Date

In addition to activties described in prevrious reports, between May 5 and May 15, 2013 approximately 85,000 cubic yards of tailings were placed to backfill the old mine pit and contoured to minimize water pooling.  Soil from undisturbed areas was used to create a cap to improve the success of revegetation efforts.  Hydroseeding has taken place and straw bales and bats have been placed for erosion control.

The top layer of soil was screened with XRF, and 10 five-point composite samples were taken to confirm that the levels of arsenic and uranium were within limits acceptable for pasture.  Human exposure to the soils will be very limited.

2.1.3 Enforcement Activities, Identity of Potentially Responsible Parties (PRPs)

2.1.4 Progress Metrics

Waste Stream Medium Quantity Manifest # Treatment Disposal

  2.2 Planning Section
    2.2.1 Anticipated Activities

A heavy rain storm appeared immediately after hydroseeding, washed away a large amount of seeds, and created scouring and other erosional issues.  A second round of grading and seeding is planned in summer/fall 2014. Planned Response Activities

Site reconnaisance was conducted in June 2014 to access the state of revegetation and the extent of erosion due to an exceptionally harsh winter.

Grading and additional erosional control measures will be undertaken in summer/fall 2014.  Efforts will also be made to stabilize the access road to the site.  Because of funding and timing issues, re-seeding will not occur until 2015.

2.2.2 Issues

Availability of additional funding will be crucial to additonal work required to make the removal efforts more permanent.

  2.3 Logistics Section
    No information available at this time.

  2.4 Finance Section
    No information available at this time.

  2.5 Other Command Staff
    No information available at this time.

3. Participating Entities
  No information available at this time.

4. Personnel On Site
  1 EPA toxicologist/health physicist, 1 EPA engineer, 1 EPA OSC

5. Definition of Terms
  No information available at this time.

6. Additional sources of information
  No information available at this time.

7. Situational Reference Materials
  No information available at this time.