Sheldon Mine Tailings Sheldon Mine Tailings Pile Cap & Drainage Pile Cap & Drainage

EnhancementsEnhancementsMarch 6, 2013March 6, 2013

Dan Shane, US EPA R9 FOSCDan Shane, US EPA R9 FOSCGrace Ma, US EPA CICGrace Ma, US EPA CIC

Brian Milton, START ContractorBrian Milton, START Contractor

OutlineOutline Overview of Sheldon Mine Overview of Sheldon Mine

sitesite Site drainage improvementsSite drainage improvements Vegetative cap systemVegetative cap system Construction methodsConstruction methods Traffic impactsTraffic impacts Questions???Questions???

Overview-Overview-Why are we here?Why are we here?

Existing cap is failing, allowing Existing cap is failing, allowing tailings high in Arsenic (As) and tailings high in Arsenic (As) and Lead (Pb), and other toxic heavy Lead (Pb), and other toxic heavy metals to migrate. metals to migrate.

Acid Mine Drainage (AMD) can Acid Mine Drainage (AMD) can leach to groundwater or surface leach to groundwater or surface waterwater

Fugitive dust can be a health Fugitive dust can be a health hazard to humans and wildlifehazard to humans and wildlife

Runoff can impact water quality in Runoff can impact water quality in Lynx Creek, Lynx Lake, and in Lynx Creek, Lynx Lake, and in down-gradient water wells.down-gradient water wells.

Overview-Overview-What will the EPA do What will the EPA do

about it?about it? Site drainage improvements to route Site drainage improvements to route clean water around the Tailings Pile. --clean water around the Tailings Pile. --Reduces or eliminates contaminated Reduces or eliminates contaminated surface runoff and impacts to surface runoff and impacts to groundwatergroundwater

Vegetative Cap constructed of natural Vegetative Cap constructed of natural materials (wood mulch, soil, and organic materials (wood mulch, soil, and organic compost)compost)-Prevents fugitive dust emissions and -Prevents fugitive dust emissions and reduces impacts to groundwater and reduces impacts to groundwater and surface water from infiltration and surface water from infiltration and generation of AMDgeneration of AMD

Coordination of activities with USFS, Coordination of activities with USFS, AZDEQ, SHPO, Yavapai County, Walker AZDEQ, SHPO, Yavapai County, Walker FD, City of Prescott, and Tribal Nations FD, City of Prescott, and Tribal Nations

Overview-Overview-What are the impacts What are the impacts

to local residents?to local residents? Likely to have temporary road Likely to have temporary road

closures and delays and closures and delays and alternate routes near site alternate routes near site

Heavy equipment at site and Heavy equipment at site and trucks on Walker Road-trucks on Walker Road-increased noise during increased noise during business hours.business hours.

Dust emissions on dirt roads Dust emissions on dirt roads and during excavation and during excavation

5-6 week project duration5-6 week project duration

Overview-Overview-What will the EPA do to What will the EPA do to mitigate these impacts?mitigate these impacts? Command Post Command Post

communication center communication center (phones and radios)(phones and radios)

Periodic fact sheets and Periodic fact sheets and website will provide website will provide updated info on projectupdated info on project

EPA OSC at the site and EPA OSC at the site and available to help available to help

Overview-Overview-What will the EPA do to What will the EPA do to mitigate these impacts?mitigate these impacts?

Hire a local traffic safety Hire a local traffic safety consultant to develop a traffic consultant to develop a traffic control plancontrol plan

Road signs and flaggers will help Road signs and flaggers will help direct traffic through work zonedirect traffic through work zone

Dust suppression w/water trucks Dust suppression w/water trucks Gorilla Snot – non-toxic glue Gorilla Snot – non-toxic glue

Conduct air monitoring to ensure Conduct air monitoring to ensure dust emissions are at safe levelsdust emissions are at safe levels

Traffic Control and Road Traffic Control and Road CrossingsCrossings

Temporary traffic delays and road closuresTemporary traffic delays and road closures Import of materials will likely mean temporary delays from Import of materials will likely mean temporary delays from

~7:30 am-5:30 pm on Walker Road between FD and Site ~7:30 am-5:30 pm on Walker Road between FD and Site for 10-15 days during construction.for 10-15 days during construction.

Heavy equipment and truck traffic on Eagle Road which Heavy equipment and truck traffic on Eagle Road which borders the site will cause temporary delays for 4-6 weeks.borders the site will cause temporary delays for 4-6 weeks.

Culvert pipe installation work on Walker Rd near New Culvert pipe installation work on Walker Rd near New Strike Ln may mean complete road closure for 7-9 hours Strike Ln may mean complete road closure for 7-9 hours one day in May, 2013. EPA will ensure that ambulances one day in May, 2013. EPA will ensure that ambulances and fire trucks will be able to pass over trench on steel and fire trucks will be able to pass over trench on steel road crossing plates. road crossing plates.

EPA will work with the Walker FD and County PW to notify EPA will work with the Walker FD and County PW to notify residents in advance of any major road delay or temporary residents in advance of any major road delay or temporary road closure that may impact residents and to lessen the road closure that may impact residents and to lessen the impact as much as possible. impact as much as possible.

Traffic Control PlanTraffic Control Plan

EPA is working with County EPA is working with County PW and traffic safety PW and traffic safety company to design a plan to company to design a plan to direct traffic on Walker Rddirect traffic on Walker Rd

Residents should avoid Residents should avoid driving on Walker Rd driving on Walker Rd between hours 7:30 am – between hours 7:30 am – 5:30 pm due to potential 5:30 pm due to potential delaysdelays

Vicinity MapVicinity Map

SHELDON TAILINGS PILE

SHELDON ROAD

E. WALKER ROAD

To Prescott 8 Miles.

BackgroundBackground

1863-1959: Active copper, gold, silver, and 1863-1959: Active copper, gold, silver, and lead mine.lead mine.

1975-6: Partial Site restoration by University 1975-6: Partial Site restoration by University of Arizona School of Renewable Natural of Arizona School of Renewable Natural Resources and the U.S. Forest Service.Resources and the U.S. Forest Service.

1999: Environmental Investigation of mine 1999: Environmental Investigation of mine sites in the Lynx Creek and Hassayampa Creek sites in the Lynx Creek and Hassayampa Creek watersheds (EPA, USFS, USFWS, ADEQ, watersheds (EPA, USFS, USFWS, ADEQ, ADHS, AG&F). Surface water, soil, sediment ADHS, AG&F). Surface water, soil, sediment and tailings samples were collected throughout and tailings samples were collected throughout the watershed. the watershed.

Background (cont)Background (cont)

2004 -2005: Sediment, water, crayfish, and fish 2004 -2005: Sediment, water, crayfish, and fish were collected from Lynx Creek and Lynx Lake were collected from Lynx Creek and Lynx Lake (USFWS and EPA). Heavy metals contamination (USFWS and EPA). Heavy metals contamination was found in water and sediments from Lynx was found in water and sediments from Lynx Creek; crayfish, carp and catfish had elevated Creek; crayfish, carp and catfish had elevated concentrations.concentrations.

2005: EPA Removal Assessment. Surface and 2005: EPA Removal Assessment. Surface and subsurface soils and water were collected at subsurface soils and water were collected at Sheldon. Elevated levels of As and Pb detected in Sheldon. Elevated levels of As and Pb detected in soil samples. Low pH (acidic) water high in soil samples. Low pH (acidic) water high in metals were detected.metals were detected.

Background (cont) Background (cont)

2012: Additional sampling and 2012: Additional sampling and investigation of soil and sediment. investigation of soil and sediment. Drainage areas downstream of TP Drainage areas downstream of TP identified as having high Pb and As identified as having high Pb and As concentrations. concentrations.

2013: Removal Action to remediate 2013: Removal Action to remediate Tailings Pile and contaminated Tailings Pile and contaminated sediments in drainage channel.sediments in drainage channel.

Tailings PileTailings Pile

Tailings PileTailings Pile

Why is there a Problem?Why is there a Problem? Loss of cover due to erosion allows exposure of Loss of cover due to erosion allows exposure of

pyritic (high iron and sulfide) mine waste to pyritic (high iron and sulfide) mine waste to oxygen and water.oxygen and water. Metal sulfide minerals are oxidized and dissolve Metal sulfide minerals are oxidized and dissolve

into water. Acid generation occurs resulting in into water. Acid generation occurs resulting in increased metal mobility and increased acidity increased metal mobility and increased acidity (lowered pH)(lowered pH)

Contaminated runoff to Lynx Creek and Contaminated runoff to Lynx Creek and groundwatergroundwater

Fugitive dustFugitive dust Direct contactDirect contact

Remedial ActionsRemedial Actions Site Drainage ImprovementsSite Drainage Improvements

GradingGrading French drain system with lined trenches to French drain system with lined trenches to

reroute clean surface water around mine reroute clean surface water around mine wastewaste

Vegetative CapVegetative Cap Barrier to direct exposure and fugitive dustBarrier to direct exposure and fugitive dust Reduction of storm water infiltration to Reduction of storm water infiltration to

minimize Acid Mine Drainage (AMD)minimize Acid Mine Drainage (AMD) Excavation and removal of contaminated Excavation and removal of contaminated

sediments in stream channelsediments in stream channel

Site Drainage Site Drainage ImprovementsImprovements

Grade site to remove areas of Grade site to remove areas of ponding.ponding.

Install French Drain system Install French Drain system around the perimeter of the around the perimeter of the tailings pile.tailings pile.

Diverts surface water around the Diverts surface water around the tailings pile to natural drainage.tailings pile to natural drainage.

Minimizes water available for acid Minimizes water available for acid mine drainage.mine drainage.

Evapotranspiration Covers-How do they work?

Isolate contaminants and keep them in place to prevent spread of contaminated materials

- Typically constructed by placing 2- to 10-foot-thick layer of fine-grained soil over contaminated material

- Native grass, shurbs, small trees that form extensive root systems are planted in the soil

- Soil-plant layer of an ET cover slows downward movement of rainwater and snowmelt and promotes storage of water

- Stored water will either evaporate or transpire which keeps water from seeping into contaminated material

- ET covers are commonly used in dry climates where there is little rainfall

- ET covers can be used to cover tailings piles to prevent or reduce acid mine drainage

The Vegetative CapThe Vegetative Cap

Purpose –Designed to create a Purpose –Designed to create a physical barrier between the waste physical barrier between the waste and the environment to prevent and the environment to prevent uncontrolled release of contaminationuncontrolled release of contamination

Acts as a “sponge” to hold water until Acts as a “sponge” to hold water until it can evaporate, or be used by plantsit can evaporate, or be used by plants

Additionally the vegetation on the Additionally the vegetation on the surface helps prevent erosion and surface helps prevent erosion and reduces water infiltration, minimizing reduces water infiltration, minimizing acid mine drainage.acid mine drainage.

The Vegetative CapThe Vegetative Cap The CAP:The CAP:

Organic mulch lower layer that isolates contaminated Organic mulch lower layer that isolates contaminated mine waste, slowly releases N and P, holds water, and mine waste, slowly releases N and P, holds water, and helps plants grow long-termhelps plants grow long-term

Upper vegetated layer that acts as a spongeUpper vegetated layer that acts as a sponge Special blend of available borrow soil and organic Special blend of available borrow soil and organic

fertilizerfertilizer Good growth media for establishing plantsGood growth media for establishing plants Plant uptake, transpiration and evaporation help Plant uptake, transpiration and evaporation help

prevent water infiltration into tailings and the prevent water infiltration into tailings and the generation and migration of AMD from the repositorygeneration and migration of AMD from the repository

Multiple layers work together to seal in waste, Multiple layers work together to seal in waste, store water, prevent erosion, and limit AMD store water, prevent erosion, and limit AMD generationgeneration

Vegetative CapVegetative Cap

Erosion ControlErosion Control Hydroseeding of vegetative cap to reduce Hydroseeding of vegetative cap to reduce

erosion due to rainfall.erosion due to rainfall. Install fiber rolls around culverts and Install fiber rolls around culverts and

across all vegetated slopes.across all vegetated slopes. Reduce loss of topsoil and sediment Reduce loss of topsoil and sediment

loading to waterways.loading to waterways. Reduce erosion due to rainfall.Reduce erosion due to rainfall. Blown Straw on surface to reduce Blown Straw on surface to reduce

impact energy of rainfall.impact energy of rainfall.

Import Quantities Approximately 3,300 cubic yards (cy) of

Borrow Soil available at no cost from USFS. Located ~6 miles from the site off of Walker Road

Approximately 1,100 cy of composted wood mulch available at no cost from Sun Dog Ranch Road Transfer Station

Approximately 225 cy of Exceptional Quality Class A sterile biosolid compost

LOTS OF TRUCKING (approx. 500 loads)

Project Summary

US EPA to improve drainage and restore cap at Sheldon Tailings Pile beginning ~4/15 to limit or prevent contaminated soil, surface water, and groundwater from migrating offsite

Temporary alternate routes and road closures possible for 3-6 weeks ~4/15-late May

Project completion date ~ June 1 Improvements expected to last >30 years.

Questions???Questions???

Eagle Road Crossing Eagle Road Crossing (plan view)(plan view)

Eagle Road Crossing Eagle Road Crossing (section)(section)

Walker Road Crossing Walker Road Crossing (plan view)(plan view)

Walker Road Crossing Walker Road Crossing (section)(section)

French Drain SystemFrench Drain System

Slotted pipe laid near surface to Slotted pipe laid near surface to capture and transport surface water.capture and transport surface water.

Tailings Pile Grading Tailings Pile Grading PlanPlan

A Few DefinitionsA Few Definitions

Wood Mulch – yard waste from local transfer Wood Mulch – yard waste from local transfer station.station.

Borrow Soil – imported soil used as fill in the Borrow Soil – imported soil used as fill in the vegetative cap.vegetative cap.

Class A Biosolids – Typically a composted Class A Biosolids – Typically a composted organic byproduct from a wastewater organic byproduct from a wastewater treatment plant. Class A (or Exceptional treatment plant. Class A (or Exceptional Quality) biosolids are tested and meet State Quality) biosolids are tested and meet State and Federal Standards.and Federal Standards.

Hydroseed – a grass planting slurry sprayed Hydroseed – a grass planting slurry sprayed on surface made up of mulch and grass seed.on surface made up of mulch and grass seed.

Definitions (cont.)Definitions (cont.)

Concrete Cloth – is a flexible concrete Concrete Cloth – is a flexible concrete impregnated fabric, that hardens on impregnated fabric, that hardens on hydration to form a thin, durable, water hydration to form a thin, durable, water proof concrete layer.proof concrete layer.

Riprap - rock used to armour streambeds, Riprap - rock used to armour streambeds, bridge abutments, and other shoreline bridge abutments, and other shoreline structures against scour by water.structures against scour by water.

HDPE – High Density Polyethylene, a HDPE – High Density Polyethylene, a rugged, chemically resistant piping rugged, chemically resistant piping material.material.