2016-06-17_PERMIT FILE - C1982056 ‎(5)‎

• Permit No: C1982056
• IBM Index Class Name: Permit File
• Doc Date: 6/17/2016
• Doc Name: CPW and CWQCD Approval of Flocculant Use at Fish Creek Borehole
• Section_Exhibit Name: Exhibit 49G Flocculant System at Fish Creek Borehole, Regulatory Approvals
• Media Type: D
• Archive: No

Thanks again for the opportunity to provide input,
1=1H 11"r-%ii1son
Aquatic Biologist
Colorado parks and Wildlife
925 Weiss Dr.
Steamboat Springs, CO 80487
office: 970-871-2868. cell: 970-846-9331
e-mail: [e-mail]
On Tue, Jun 7, 2016 at 7:16 AM, Nettleton, Jerry <TNettleton'a peaboclyenerg�-.com> wrote:
Bill —
We have an existing water treatment facility on Fish Creek that has been used for years to treat mine water prior
to discharge in order to meet the effluent limits and requirements of our Colorado Discharge Permitting System
(CDPS) industrial discharge permit. Originally, this facility used sodium -hydroxide (caustic soda) to change
the pH of the mine water discharge, causing iron and other suspended solids to agglomerate and drop-out in a
three cell (in series) settling pond system prior to discharge. Sodium hydroxide is a strong alkaline material
with certain handling hazards, and the system was fairly expensive to operate, so in 2006 Twentymile converted
our treatment system to an electro -coagulation system, where the mine water is directed over a series of charged
electric plates causing suspended solids in the water to pick-up an electrical charge, adhere to other particles,
and drop-out in the settling pond system prior to discharge.
While this system remains in-place, we have not used it for a number of years because our extensive mine water
recycling system has allowed us to balance mine water use with mine inflow and recycling such that both our
water withdrawals and discharge have been minimal. We are moving into a new coal seam which is underneath
the previously mined seam. In order to safely develop and mine this lower seam, we need to drain some of the
water which has accumulated in the previously mined and sealed areas of the upper seam. This additional water
volume means that we need to discharge some of the water.
The water that we need to discharge has elevated coal fines from pumping operations, elevated iron, and
elevated electrical conductivity (EC). In consultation with water treatment professionals, we have determined
that the coal fines and iron can most effectively be treated with a polymer flocculant. The flocculant would be
metered into the flow stream in the existing Electro -Coagulation Building prior to a mixing tank, with the
discharge into the first cell of the three -cell settling pond system, and progressive movement through the pond
system to the discharge point. The selected flocculant (SOLENIS Amerifloc 490 — Safety Data Sheet attached)
is approved for use in drinking water systems, and at the proposed feed rate of 20 mg/I will be consumed in the
reaction with suspended solids, with little or no residual in the discharge to the stream. The SDS sheet (Section
12) indicates an LC50 for Daphnia magna (most sensitive aquatic species) of 10 — 100 mg/1, with an exposure
time of 48 hours. Based on this information, our testing, and the consultants recommendations, we are
confident that we can meet our permit effluent limits (which include WET testing) while using this treatment