Phoenix Park Mill Tailings

The Phoenix Park Mill Tailings site consists of two separate ponds containing mill tailings.  Below the lower tailings pond is a decant structure consisting of a concrete bunker and flow valve.  The preferred reclamation method for the Phoenix Park Mill Tailings is to cap in-place. 

Prior to earthwork, the pipe leading from the lower tailings pond and the decant bunker must be sealed by filling the upper end with one bag of sand and cement mix or refusal.  The concrete mixture must have a high slump (6-8”).  The concrete bunker must be removed and the concrete placed inside the lower tailings pond.  Following removal of the bunker, the decant pipe must have a cap welded onto the end.  The cap must be welded continuously around the pipe.  Once the cap is welded, the bunker area must be graded to conform to the surrounding topography. 

The mill tailings in the upper pond have been measured to be approximately 4-5 feet in depth.  These tailings will be graded into the lower pond after removing and stockpiling the embankment between the ponds.  The top one foot of the soil material underlying the mill tailings will also be removed and placed on top of the consolidated mill tailings.  Approximately 3,200 cubic yards of mill tailings and underlying soil must be moved.

Following consolidation of the mill tailings, the embankments will be graded into the ponds.  The final graded surface must have positive drainage from the site.  The material must also be graded to the top of the existing cuts on the western side of the ponds.  Trees on the east side of the ponds must not be disturbed.  The soil in the east embankment must be removed using an excavator or other piece of equipment that will not disturb the trees adjacent to the embankment.  There are areas in the embankment that currently do not support vegetation.  In general, these areas are lighter in color and contain more rock.  The light colored, rocky materials must be placed over the consolidated mill tailings and/or at least one foot below the final fill surface.  The remaining soil material must then be placed over the light colored material.  The estimated volume of material in the embankments that must be moved is 8,200 cubic yards.

Following regrading, a berm must be constructed along the road adjacent to the ponds to direct drainage away from the regraded surface.  The berm must be a minimum of two feet in height with 2h:1v side slopes.  As an alternative, a combination berm and ditch can be constructed.  The ditch must be a minimum of one foot in depth and the berm must be one foot in height.  The side slopes of the ditch and berm must be a minimum of 2h:1v.

Following all earthwork, the entire disturbed area must be revegetated according to the attached Revegetation Specifications.

Gormax Mine

The mine drainage from the Gormax Mine currently flows over the top of the mine waste pile, and infiltrates through the pile.  Based upon analysis of this pile, the mine drainage probably leaches additional metal from the mine waste.  A diversion ditch a minimum of two feet in depth with minimum side slopes of 2h:1v must be constructed to divert the drainage to the north side of the mine waste pile.  In addition, the drainage from the access road has been observed to flow onto the waste pile.  To prevent this, a swale one foot in depth with 8h:1v side slopes must be constructed to divert the water to the south side of the waste pile.  The material removed to create the swale must be placed on the pile.  Any disturbed areas must be revegetated according to the attached Revegetation Specifications.

The Gormax waste rock pile is partially vegetated.  To reduce erosion and leaching of metals from the waste pile, the outslope of the pile will be revegetated.  The outslope of the pile is at the angle of repose.  The entire outslope will be seeded, fertilized, and mulched following the Revegetation Specifications.  Following seed and fertilizer application, the surface must be hand raked to cover the seed.  Mulch must be crimped into the waste rock by hand methods.

Phoenix Mine

The waste rock pile of the Phoenix Mine is located in an ephemeral drainage.  There is visual evidence that the pile has eroded following thunderstorms.  The outslopes of the mine waste are at the angle of repose, and the natural slopes are also very steep.  Some access improvement will be necessary.

The drainage will be diverted to south side of the waste rock pile by the construction of a diversion ditch.  The diversion ditch will be approximately 175 feet long and will divert run-on drainage to the south onto a vegetated slope. 

The diversion ditch must be a final depth of three feet with 2h:1v side slopes and a bottom width of two feet.  The ditch will have to be over-excavated to allow placement of riprap.  Riprap must be a minimum of one foot in diameter in its smallest dimension.  The riprap must be placed over filter fabric.  The filter fabric must extend a minimum of 6” beyond the top of the ditch.  Riprap must be placed close together to minimize spaces between the individual rocks.  Some hand placement will be necessary.  All the spaces between rocks must be filled with soil excavated from the ditch. 

The inlet to the ditch must extend a minimum of 8 feet to both sides of the existing drainage.  Riprap a minimum of one foot in diameter in its smallest dimension must be placed in an area 10 feet wide and 10 feet long below the outlet as an energy dissipater and to allow the drainage to spread out over the vegetated slope below.

Any disturbed areas must be revegetated according to the attached Revegetation Specifications.

Midwest Mine

Reclamation at the Midwest Mine will include consolidation and capping of the scattered mine waste, and miscellaneous hydrologic controls.  The road adjacent to the mine leading to East Willow Creek also contains some mine waste.  This area will be covered with fines from the excavated disposal area after lime application.  There are several buildings and a trestle at the mine that must not be damaged by construction.

Approximately 2,100 cubic yards of mine waste will be deposited in a trench/cut located near the collapsed portal of the mine.  The trench must be excavated, and the excavated material must be stockpiled in a location designated by the PROJECT MANAGER.  The trench shall extend from the ventilation building to approximately 50 feet east of the portal structure.  The ventilation building will be demolished or moved to facilitate construction of the disposal area.  Care must be taken during construction to not damage the exposed portion of the portal structure and the core shack.  A mine closure monument is located north of the ventilation building at a backfilled portal.  This monument must be removed and replaced following placement of the mine waste and soil cap.

The PROJECT MANAGER will stake the boundaries of the disposal area.  It is estimated that approximately 1,400 cubic yards of material will be removed in the disposal area.  The disposal area will be excavated to the existing level of the bench between the buildings.  A small portion of the excavated material will be place in a pond on the east side of the Nelson/East Willow Creek road across from the lower bench of waste rock.  The entire area between the ventilation building and the portal structure can be excavated. However, the portion from the portal structure, east, must be excavated as a trench.  The cut slope shall not have a slope steeper than 1h:2v.  A portion of the partially collapsed, timbered entry will be excavated.  This will expose the underground workings.  The underground workings must be backfilled with mine waste for a minimum of 15 feet from the north boundary of the excavation.

Following excavation of the disposal area, approximately 2,100 cubic yards of mine waste will be consolidated in the excavated area.  Approximately 900 cubic yards will be moved from the lower bench and1,200 cubic yards from the middle bench.  The mine waste at the trestle area will not be moved.  Approximately 100 cubic yards of mine waste located adjacent to Nelson Creek will be consolidated with the mine waste under the trestle to reduce the slopes.  It is acceptable to construct the disposal area in stages to reduce double handling of the cover material.  The mine waste must be capped with a minimum of two feet of excavated soil.  The fill height/final grade must conform to the adjacent existing undisturbed slopes.  Any excess material excavated from the disposal area must be spread evenly throughout the mine waste removal area.

Approximately 1 acre of disturbed area will be revegetated per the attached Revegetation Specifications.  Limestone will be added to the mine waste disposal area and the undisturbed mine waste to reduce metals leaching from the site.  Approximately 40 tons of minus 40 mesh limestone with a minimum of 90% CaCO₃ equivalent will be uniformly spread over the removal area and the exposed mine waste prior to topsoil placement.  Limestone must be spread inside the track/trestle by hand methods.

Approximately 400 feet of roadway was constructed with mine waste from the Midwest Mine.  Hydrated lime or cement kiln dust must be placed on the road surface, and then the lime/kiln dust must be covered with fine material excavated from the disposal area.  Five tons of cement kiln dust or 2.5 tons of hydrated lime is required.  The lime/kiln dust must be covered with six inches of soil material.  The lime/kiln dust must be wetted prior to application of the soil material.

Park Regent Mine

Reclamation at the Park Regent Mine will consist of consolidation of the mine waste, capping or liming of the surface, and diverting run-on water around the pile.  Currently, acid-forming mine waste is spread over a large area.  There is a vegetation kill zone covering in excess of ¼ acre below the waste pile.  The Park Regent mine is a stop on the Bachelor Tour Route.

Approximately 1,000 cubic yards of waste is scattered on the east side of the main pile.  This waste must be consolidated with the main pile in a triangular area on the east side.  In addition, approximately 1,200 cubic yards of waste on the north end can be consolidated to reduce the footprint of the site.  A small amount of the waste can be placed inside the capped, collapsed shaft.  The entire consolidated waste pile must be graded to provide for positive drainage, but must be done in a manner that maintains the historic flavor of the site.  The consolidated waste pile will cover approximately one acre.

Following consolidation of the waste rock, 13 tons of minus 40 mesh ground limestone must be uniformly applied to the removal area and the denuded area, then the area must be revegetated per the Revegetation Specifications. Additionally, 40 tons of minus 40 mesh limestone must be applied to the consolidated waste rock.  To maintain the historic flavor of this site, no revegetation will be done on the consolidated waste rock.

In order to reduce leaching and erosion from the pile, approximately 375 feet of diversion ditch must be constructed on the west side of the pile.  The diversion ditch must be one foot in depth with 2h:1v side slopes.  The excavated portion of the ditch must be placed on the downhill side of the ditch to form a berm with maximum slopes of 2h:1v.

The Park Regent Mine is a stop on the Bachelor Historic Tour.  Therefore, the waste pile cannot be capped in-place or moved to a disposal area.  In order to reduce the environmental degradation from the pile, the upper one foot of the consolidated waste pile will be cemented by the incorporation of a mixture of cement kiln dust (CKD) and cement.