_GENERAL DOCUMENTS - C1981017 ‎(279)‎

• Permit No: C1981017
• IBM Index Class Name: GENERAL DOCUMENTS
• Doc Name: Bid Documents ‎(IMP)‎
• Media Type: D
• Archive: No

Mine No. 1 and No. 2
1. Map 11-B-App.7-Att.1 indicates only one sedimentation pond in use to
settle out disturbed drainage from both mines. However, State inspectors
have indicated that two ponds in a series are actually used. The applicant
should indicate the location of the second pond and include the designs of
the pond.
2. Map 11-B-App.7-Att.1 identifies a small pond located on the north side
of pad #4. The application should include design information on this pond to
verify compliance with Section 4.05.
3. A series of diversion ditches, collection ditches, and conduit conveyance
pipes -are in use at Mine #1 and #2 to route disturbed drainage to sedimentation
ponds. The application should include designs on these structures to verify
that they are in compliance with Section 4.05.3, which deals with Diversions
and Conveyance of Overland Flow. The primary design criteria that needs to be
addressed is that the structures can safely pass the runoff generated from a
10-year, 24-hour event with adequate freeboard. In addition, the designs
should show that velocities in these structures will not result in scouring
of the channel nor excessive erosion at the outlet.
4. The pond designs for these mines indicates that a 18" csp conduit is used
as a primary and emergency spillway and is located above the 10-year flood
storage level. This design is in direct conflict with several regulations
contained in Section 4.05.6. Section 4.05.6(3) (c) requires the installation of
a non-clogging dewatering device to remove stored water resulting from inflow.
The dewatering device should be located at the elevation of the 100% sediment
storage volume level. Section 4.05.6(3) (e) requires that there be no outflow
through the emergency spillway during the passage of runoff resulting from
the 10-year, 24-hour event. The applicant should, redesi gn this pond to
provide for an appropriate combination of principal and emergency spillways,
as well as a dewatering device to bring this structure into compliance with
this Section.
5. Page 37 of Volume 3 displays design flows from seven drainage areas which
range from a low of 0.38 cfs to a high of 6.93 cfs. Page 39 indicates that
the maximum spillway discharge required is 3.0 cfs. The applicant should detail
how the spillway design discharge was arrived at. If storage routing was used,
the raw calculations should be submitted.
6. Capacity curves displayed on Map I1-B-App.7-Att.1 indicate storage
designated for mine effluent. The applicant should indicate how much water
(range) is being pumped from the mine to this pond.
Mine No. 3
1. Several diversion and collection ditches are used to convey disturbed
drainage to ponds 3-1, 3-2A, and 3-2B. The applicant should include designs
of these ditches that verify that they can handle a 10-year, 24-hour event
with adequate freeboard and will not result in excessive scouring or erosion
at the outlet.