1993-04-19_REVISION - C1981008

• Permit No: C1981008
• IBM Index Class Name: Revision
• Doc Date: 4/19/1993
• Doc Name: PROPOSED DECISION & FINDINGS OF COMPLIANCE FOR RN2
• Type & Sequence: RN2
• Media Type: D
• Archive: No

of the irrigation system for this area in about 1910, these areas have been
intensively reworked for irrigated agriculture. Especially in the New Horizon
Mine 2 mining area, the surface water system is characterized by a
"disjointed" tributary drainage system almost completely controlled by return
flow ditches of the local irrigation network. The perennial flow nature of
both Tuttle and Calamity Draws is largely due to the local irrigation
practices. Over the years this more or less constant source of water in these
drainage systems has encouraged the growth of vegetation. This has resulted
in the channels becoming more erosionally stable but more incised.
In the New Horizon Mine 1 area the Second Park Lateral Irrigation Ditch is in
continuous operation from mid-April through mid-October. While this water is
primarily used for irrigation, important secondary uses include maintaining
water levels in stock ponds and domestic cisterns . During the non-irrigation
season the ditch is occasionally turned on to maintain the water levels in the
stock ponds and cisterns .
The flow in Tuttle Draw is primarily from irrigation return waters.
Occasional precipitation and snowmelt events contribute waters to this Draw.
Sediment Pond 001 discharges water to this drainage system regularly with
flows characterized by lows in April , averaging about 0.01 cfs , to highs in
September of 0. 9 cfs . Sediment Pond 006 discharges significant flow to Tuttle
Draw beginning in May and continuing through August. Average flow for this
period is 0.4 cfs. In September discharges from Sediment Pond 006 rapidly
decline . In January through April the average discharge is insignificant.
This discharge has been monitored for ten years . These flows appear to be
greatly influenced by local irrigation practices . Impacts on water quality
from these ponds on Tuttle Draw are very limited due to the high dilution
ratios . These discharges occur upstream of surface water monitoring site
SW-N3. Measurements of water flow at SW-N3 show rates from 0.019 cfs to
9.35 cfs . Flows in April were measured at 0.665 cfs and at 9.35 cfs in
September. The West Return Ditch is also tributary to Tuttle Draw just
upstream of SW-N3. Contributions from this source generally decline to near
zero during the non-irrigation period. These flows vary from 0.006 cfs during
April to 0.856 cfs in June.
Flows in Calamity Draw generally reflect local irrigation practices. Water
from the West Lateral Ditch ' s return irrigation flow is its primary source .
Very little supplemental flow is derived from precipitation and snowmelt
runoff. In 1987, measured flow rates in Calamity Draw varied from 0.605 cfs
in April to 13.4 cfs in July. Flow in Calamity Draw varied from 1 .04 to
2.06 cfs during the non-irrigation period. Shallow ground water alluvial
sources provide a large portion of this low flow period' s water. This ground
water flow is related to local irrigation practices but is consolidated into a
more uniform and regular flow by the permeabilities of these near surface
alluvial deposits. Sediment Pond 007 for the New Horizon Mine 2 mining site
will contribute water to the Calamity Draw system. The drainage system at the
New Horizon 2 site has been designed to provide adequate capacity and storage
times to completely control a 10-year 24-hour precipitation event. This
system will collect all runoff from the mine site and should actually lower
present total suspended solids (TSS) contribution from this area over the life
of the mine. Increased TDS levels in this water from mining disturbances are
expected but are projected to be within acceptable discharge levels and will
be mitigated by dilution. Regular monitoring of these flow rates and water
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