Site Update 6/3/24:
- On May 23, Cascade County notified EPA that a culverted crossing installed on Carpenter Creek road last fall was damaged by runoff after a heavy precipitation event. An EPA recon crew visited the location that evening to assess the situation and develop an initial repair plan. EPA mobilized a larger crew to the site on May 28 to begin repairs. Initial assessments indicate that pieces of rip rap rock were dislodged, allowing water to get behind the rock and causing the damage. The culvert and crossing are structurally sound.
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As of June 3, EPA repaired the crossing
with concrete and rebuilt rip rap surrounding the culvert. The last remaining work is to remove the molds/forms
used to pour the concrete and fill in any gaps. The team filled a pothole in the road and recompacted the
road with new road base. Additional work, beyond removing the concrete forms and filling the gaps, is not planned at this time.
Background:
On May 31, 2023 the
EPA Remedial Project Manager and Montana DEQ Project Officer visited the site
and observed runoff from the road above the adit during a high intensity rain
event. Observations around the adit suggested that large amounts of sediment
and debris were being deposited in front of the adit and that the adit was
filling with water and there was potential for an uncontrolled release. The
USFS District Ranger also called the EPA Remedial Project Manager to state that
Carpenter Creek and Belt Creek were muddy. EPA, Montana DEQ and US Forest
Service staff visited the site on June 14 and again on June 21, 2023. Each
visit coincided with a precipitation event. There was observable runoff
on the road above the adit and the area surrounding the adit. During the 2023
high spring runoff a large volume of water from the hill drained through the
gulley, resulting in erosion and mudslides.
This Site is located
within Operable Unit 3 (OU3) of the Carpenter-Snow Creek Mining District
Superfund Site, near the Town of Neihart, Cascade County, Montana. This
emergency removal action will address severe erosional damage to the area
around and down-drainage of the Silver Dyke Mine adit caused by a high level of
snowmelt followed by extremely heavy rains in Spring 2023. The high flow runs
down the gulley, eroding large cuts into the waste rock below the adit. After
drainage control measures above the adit are complete, the removal will focus
on removing waste rock that is in the flow path below the adit; installing a
series of control ponds to regulate surge flows from the adit and drainage and
repair two downstream tailings impoundments damaged by high water events.
