20020508 Ver 3_Fax_20081013

?0F W A rF9Q Michael F. Easley, Governor
?O C William G. Ross Jr., Secretary
North Carolina Department of Environment and Natural Resources
Coleen H. Sullins, Director
Division of Water Quality
Division of Water Quality
Department of Environmental and Natural Resources
401 Oversight/Express Review, Program Development and
Transportation Permitting Units
Street Address: 2321 Crabtree Boulevard, Suite 250
Raleigh, NC 27604-2260
Mailing Address: 1650 Mail Service Center
Raleigh, NC 27699-1650
Contact Information: Phone #: [phone]
Fax #: [phone]
Fax To: I f-) 7L /C ; el Fax -OF ?a0?
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Company: C C- Date:
From: C(I-n"-Jfk l C1 ?'U I Phone #: ??? (0 7 $ - ??al?
Number of pages including cover sheet: 3
Notes or special instructions:
NorthCarolina
401 Oversight/Express Review Permitting Unit- JVahlralky
1650 Mail Service Center, Raleigh, North Carolina 27699-1650
2321 Crabtree Boulevard, Suite 250, Raleigh, North Carolina 27604
Phone: [phone] / FAX [phone] / Internet: htto:Hh2o.cur.state.nc.us/ncwetlands
An Equal Opportunity/Affirmative Action Employer - 50% Recycled/10% Post Consumer Paper
Balsam Mountain Preserve
Dam Safety Comments on Mr. Bumgardner's September 4, 2008 response
October 1, 2008
Drawines:
Sheet 2
1. What is the width of the select material on SECTION A-A? Adequate response.
2. An energy dissapator is needed at the outlet end of the 24" DIP. It should be designed for
the maximum anticipated discharge velocity. Adequate response.
Sheet 3
1. How will the DIP riser be connected to the 24" DIP outlet pipe and the 8" DIP bottom
drain stub? The use of manufactured connections is recommended.
2. What will provide support for the canal gate and frame? Details of the proposed support
are suggested.
3. What is the top width of the dam on the SECTION? Adequate response.
4. The relocation of the chimney drain to a point further downstream such that the minimum
cover over the drain top elevation of 3682.0 is 2.0 feet., or approximately Station 130, is
suggested. Although no change was made we still stand by our recommendation.
Sheet 4
1. On the DIAPHRAGM DRAIN DETAIL a minimum thickness of 12" of stone at the ends
of the perforated pipe is suggested. Adequate response. Caps should be shown on the
ends of these pipe. Ident fy on the drawings. What precautions will be taken to ensure a
positive seal of the geotextile around the outlet pipe exit. It also appears the outlet pipe
for the chimney drain will penetrate this geotextile on both sides of the drain. The same
precautions should also be taken. Adequate response.
2. Will 20 feet of well screen be sufficient to remove the inflow to this large chimney drain?
Calculations to support response are recommended. An increase in the chimney drain
thickness to 3.0 feet is suggested. Response acceptable. It was also noted that the
chimney drain in plan view appears to extend beyond the limits shown on DAM CROSS
SECTION B-B.
3. On the PIPE OUTLET - HEAD WALL, two additional drain pipe should be shown on
the elevation view. Adequate response.
4. The trash rack is shown to be both CMP and DIP. Which is it? Adequate response.
5. The following suggestions are made for the trash rack. Move the rebar grating to the top
of the trash rack, raise the top to 12" above the normal pool, and provide another means
of supporting it on the riser. Require the trash rack to be hot dip galvanized after
fabrication. Response unacceptable.
Specifications:
1. Is the geotextile specified shown around the diaphragm drain a woven or non-woven
fabric? Is the Trevira 1135 fabric still available? The use of a non-woven fabric is
suggested. Adequate response.
Flanged joints should not be used in the earth fill portion of this installation. The joints
should be push-on or mechanical that will allow for some rotation of the joints. Adequate
response.
It appears the contractor could use Class II, Type 1 backfill which would be too coarse
for dam backfill. The use of Class I backfill is suggested. Adequate response.