GENERAL30475

• Permit No: C1981019
• IBM Index Class Name: General Documents
• Doc Date: 5/4/2007
• Doc Name: Proposed Decision & Findings of Compliance for PR2
• Permit Index Doc Type: Findings
• Media Type: D
• Archive: No

was, as a result, necessarily modified. The pre-mining 16,000-foot-long Streeter Gulch profile ranged
from 5% near the lower end, increasing to 12.5 % for the upper 1800 feet (measurements, Map 18,
PAP). The post-mining profile is 30% for the first 1000 feet up the face of the Streeter Spoil fill, and
thence approximately 4 % across the approved post-mining topography of reclaimed land
(measurements, Map 19, PAP). Such diversions are designed, and certified by a registered
professional engineer, to accommodate the 100-year design storm [Rule 4.05.4(2)(a) and (b)]. These
diversions comply with the requirements of Rules 4.05.3(1)(b) through (f) (they are in compliarice
with applicable statutes and regulations, are designed not to increase flooding or otherwise endanger
property or public safety, are designed to be stable and not adversely impact to the hydrologic
balance, and do not divert water into underground mines). Construction is still in progress. Riprap is
used to control erosion. The channels aze stable and require infrequent maintenance [Rules
4.05.4(2)(a) and (4.05.4(4)(b)]. In smaller tributaries, profiles have been altered to accommodate
post-mining sides at lesser slopes (for stability) than original steep ravine slopes.
1. The Division proposes to approve the diversion of an ephemeral stream draining at least one
square mile. This decision is based on a finding that the proposed diversion meets the requirements
of 4.05.]8 and 4.05.4, applicable local, State, and Federal statutes and regulations and that the
diversion is designed to safeguard public safety and to minimize adverse impacts to the hydrologic
balance. The reclaimed Streeter Gulch ditch will drain a watershed area of about 1280 acres. Streeter
Gulch is an ephemera] drainage (PAP, page 2.04.7-27). It was (pre-mining) asteep-sided, 200-foot
deep (neaz the mouth) incised draw (PAP, Map 1 I ). Initial box cut material for mining south of the
Gulch (Draw) (PAP, page 2.06-3) was placed near the mouth, first as an experimental practice and
later recognized as excess spoil (overburden) fill. Upstream topography was, as a result, necessarily
modified. The pre-mining 16,000-foot-long Streeter Gulch profile ranged from 5% neaz the lower
end, increasing to 12.5 % for the upper 1800 feet (measurements, Map 18, PAP). The post-mining
profile is 30% for the first 1000 feet up the face of the Streeter Spoil fill, and thence approximately 4
across the approved post-mining topography of reclaimed land (measurements, Map 19, PAP)
(4.05.4(1) and (4)).
2. Channel lining structures, retention basins, and artificial channel roughness structures aze
approved for use to control erosion. These means are proposed to be approved by the Division since
they aze necessary to control erosion, they aze stable and will require infrequent maintenance. Riprap
lining, permanent stock ponds, and dugout sediment traps on the spoil areas are the measures that
will be used (4.05.4(2)(a)).
3. The Division does not approve a stream channel diversion with a lesser capacity than the
unmodified stream channel immediately above and below the diversion (4.05.4(2)(b)).
4. The Division approves permanent diversions in the reclaimed area. These diversions are the
reconstructed ephemeral channels necessary to safely drain the reclaimed lands after mining. The
diversions aze consistent with applicable state law, will not diminish downstream water rights and
meet the requirements of Rule 4.05.4 (4.05.4(3)).
Proposed Decision and Findings of Compliance 4 May 2007
Perini[ Revision 02 Page 33