20051117 Ver 2_More Info Received_20080917

Condition 10.
I /?TF 05- 401 Water Quality Certification No. 3742 111?
Subject: Condition 10. 401 Water Quality Certification No. 3742 <D
From: Lang Wilcox <[e-mail]>
Date: Wed, 17 Sep 2008 09:59:18 -0400
To: "'Ian McMillan"' <[e-mail]>
Ian,
Good morning. I hope you are doing well.
`D
We have completed the study of the subsurface rock structure under the location of the proposed
stream-crossings where we plan on utilizing open-bottom culverts. We found as expected that there is solid rock
close to the surface of a non-erosive type to allow for the proper design and installation of our crossings. I have
attached the letter from our geotechnical engineer, signed and sealed.
I believe this satisfies Condition 10 of the permit.
Thanks again and I will talk with you soon. Please call if you have any questions.
Very truly yours,
Lang Wilcox
Lissara Partners, LLC
2008-08-27 ET letter for open-bottom culvert geotech0001.pdf Content-Type: application/pdf
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Content-Type: application/pdf
2008-08-27 ET letter for open-bottom culvert geotech0002.pdf
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1 of 1 9/17/2008 9:15 AM
ENGINEERING TECTONICS, P.A.
ENGINEERS - GEOLOGISTS - HYDROLOGISTS
1720 Vargrave Street. Winston-Salem, NC 27107 [phone]
August 27, 2008
NC Department of Natural Environment and Natural Resources
Division of Watcr Quality
401 Oversight)'Express Review Permits Unit
1650 Mail Service Ccnter
Raleigh, North Carolina 27699-1650
Attention: Ms. Coleen H. Sullins
Subject: Lissara Development
(Forsyth) 401 _IC
Stream Crossings
Dear Ms. Sullins:
Pursuant to DWQ Permit Q0051117, Ver.2 and US Army Corps of Engineers Action ID
No. 20052.0968 for an unnamed tributary to the Yadkin River for the Proposed Lissara
Development, this letter is written to respond to condition 10 of the permit. This
condition outlines the provisions for utilization of two bottomless culverts at the locations
shw,vn on the attached map.
We have conducted a limited investigation of the subsurface conditions at the proposed
locations of the culverts to determine the condition of the bedrock. A total of four (4) test
pits were excavated at each of the proposed locations of the bottomless culverts in order
to provide direct inspection of the condition of the rock material. The pits extended
through approximately 2-3 feet of regolith soil material before the top of bedrock was
encountered. The rock in the test pits consists of weathered mica schist which according
to the NC State Geologic Map of 1985 by Brown, et al, is considered to be of Cenozoic
Age. The area lies within the Milton Belt, a zone of metamorphosed rock which was
originally deposited as sands and clays in a shallow marine cnvironmcnt. The rock. has
undergone numerous periods of metamorphism to at least a sillimanite faeies during the
Paleozoic.
The rock exposed in the test pits is a massive rock with a hardness ol'between 6 and 8 on
the Mohs hardness scale. The original bedding planes are still visible in the rock. The
bedding provide for a planar parting face that dips to the south at an angle of
approximately 25 degrees. The top of the rock surface is fairly regular within the test pits
and is absent of signs of faulting even though it is fractured throughout. While no soil
test borings were completed at the specific locations of the test pits, extensive drilling and
testing in this rock unit throughout the development indicates that the rock is quite dense
and hard. Standard Penetration Testing of the rock at either locations in the development,
performed in general accordance with ASTM Method D-1586, confirm that the rock has
a penetration resistance greater than 50 blotivs per 6 inches of penetration. Similar
conditions were observed with rock outcropping Within the stream bed alone; the axis of
the proposed bottomless culverts.
It is our processional opinion, based on inspection of the rock in the test pits at the
locations cited herein, that a rock surface exists in the areas of the proposed shallow
Iuotin,us and within the channel section of the bottomless culverts that is and will he, non-
crosivc at a design storm flow equal to a 25 year, 24 hour return interval.
We understand that when a more detailed preliminary design of the proposed bottomless
culverts is developed for the project, a subsurface investigation based. on actual soil test
borings and rock coring will he conducted by our firm. If the results of this detailed
investigation conclude that the conditions at the proposed bottomless culverts differ from
our preliminary findings, we also understand, based on condition 10 of the permit, that a
revised plan for crossing the stream will be required that either removes or relocates the
proposed crossings or provides an alternative bridge design.
We hope that this preliminary investigation provides the necessary information needed at
this time for the project to proceed. If you have any questions or desire additional.
information, please do not hesitate to contact me directly at 336 724 6994 ext. 104.
Sincerely,
I NCJLLR1-NC1'1'LC't'ONICS, P.A.
elk
:?. Barry Nelson , PG Lr.. EAL
Chic i' I nginccring Ueolol ist 166
NC' License No. 16.5 ? . ._,??. r

ENGINEERING TECTONICS. P.A.