Leavitt & Associates Engineers, Inc. completes a new gold ore
processing plant for the Golden Eagle Mine owned and operated by Greyhound
Mining & Milling, Inc. The Golden Eagle Mine is located on Blacks Creek Road
east of Interstate 84 in Ada County, Idaho. Leavitt’s scope included civil
engineering of the mine site design, structural engineering for the mill
building and plant facilities, geotechnical engineering for the soils and
foundations, environmental engineering and permitting, building permit
acquisition and material testing and special inspection of construction.
The Golden Eagle Mine is an underground operation which was originally
patented in 1914. Dan Yanke and his sons have owned and operated the mine
since 1984.
The new processing plant includes an outside crushing and screening circuit
and an indoor mill grinding, classification, concentration and products
circuit. The facility is scheduled to begin operations in the spring of
2010. The mill will operate 24 hours each day, Monday through Friday. The
mill will be shut down during the winter months. Approximately 50 tons of
ore will be processed per day and 10,000 tons per year yielding
approximately 1,000 ounces of gold per year.
The existing mine site was revised to add the new mill building and material
handling equipment. The mine site plan was updated to show the existing
facilities and the new site additions. New site access, mine roads and
parking areas were added. A new crusher was added to reduce the size of the
ore to be processed. Material handling receiving hoppers, belt conveyors,
screens and transfers were added to carry the material through the outdoor
crusher circuit and deliver the ore to the processing plant. A new 250 KW
diesel generator with a 2,000 gallon diesel tank was added to provide
crusher circuit power. A new tailings pond and mine dewater and storm
retention pond was added. The storm water retention plan was developed and
designed to manage on site storm drainage and runoff.
The processing plant uses the gravity separation and the froth flotation
process which is an old and proven technology. The mine uses no cyanide or
mercury in the ore processing. The mill building is constructed on a slope
to aid the gravity separation and flotation process. This arrangement
reduces the requirements for pumps and the power required to run them.
The mill building is a 3,128 square feet and 30 feet high engineered metal
building. The plant processing equipment is founded on heavy concrete
foundations designed to resist the heavy equipment processing loads and
vibrations. The mill building houses a 70 ton fine ore bin, a 7’ Diameter by
4’ Conical Ball Mill, a 6’ Diameter by 4’ Round Ball Mill, Roche spiral
concentrator(s), a Gemini shaker table, a 6-cell Denver Flotation Machine
and the control room.
Leavitt coordinated response to Ada County Development Services’ questions
and requests for additional information for the Master Site Plan and
Accessory Use Permit application.
Leavitt designed the mill building, and equipment access and foundations.
Building permits and plan review approvals were coordinated and obtained by
Leavitt & Associates from Ada County Development Services, Ada County
Engineer, Ada County Highway District, the Idaho State Fire Marshal, Central
District Health Department, DEQ, and EPA.
Environmental engineering and permitting included development of the
Emergency Response Plan and Spill Prevention Countermeasures and Contingency
(SPCC Plan) Plan. The SPCC Plan is designed in accordance with good
engineering practice to implement the Environmental Protection Agency (EPA)
rules to manage delivery and storage of diesel fuel.
The Golden Eagle Mine Dust Prevention and Control Plan was designed with
progressive control strategies to manage fugitive dust emissions in
accordance with DEQ rules. Procedures, control strategies, and control
strategy limit triggers were developed to operate the facility per IDAPA
58.01. A Daily Inspection Checklist, monitoring and recordkeeping procedures
were developed. An Odor Management Plan was waived by DEQ based on the
findings and recommendation of Leavitt & Associates.
Water sampling and testing of the mine well drinking water and mine
dewatering pond water was completed to verify and satisfy Department of
Environmental Quality (DEQ) and EPA water quality standards. Water samples
were tested for Nitrates, Nitrites, Arsenic and coli forms.
Leavitt prepared and submitted the application and submittal documents to
DEQ for Permit to Construct – Exemption (PTC-Exemption). The diesel
generator emission calculations demonstrated compliance with the
requirements for a PTC-Exemption and showed that the facility emissions were
below regulatory concern.
The Storm Water Pollution Prevention Plan (SWPPP) was designed to implement
Best Management Practices (BMPs) for erosion and sediment control, site
stabilization, good housekeeping and the Construction Site Inspection
Checklist to manage storm water runoff and control during construction.
Leavitt & Associates Engineers, Inc. has a mining engineer on staff and
provides plant facilities, mine design and engineering solutions and
services throughout the western states.
