A-0009.AcidicRockResponse.Final

STATE OF NORTH CAROLINA
DEPARTMENT OF TRANSPORTATION
ROY COOPER J. ERIC BOYETTE
GOVERNOR SECRETARY

Mailing Address:
NC DEPARTMENT OF TRANSPORTATION
DIVISION 14
253 WEBSTER ROAD
SYLVA, NC 28779
Telephone: [phone]
Fax: [phone]
Customer Service: 1-877-368-4968

Website: ncdot.gov
Location:
253 WEBSTER ROAD
SYLVA, NC 28779

September 13, 2022

Kevin Mitchell
NC Department of Water Resources
2090 US 70 Highway
Swannanoa, NC 28778-8211

Dear Mr. Mitchell,

In response to NCDWR’s Water Quality Permit Condition #3, the NC Department of
Transportation offer’s the following response.

NCDOT is aware that STIP A-0009C passes through geologic units that may contain
acid-producing mineralization. The study area north of NC 28 runs through the Wehutty
(Zwe or Anakeesta) and Nantahala (Znt) units. The Zwe and Znt units are known to be
sulfidic and were key reasons in improving existing NC 28 to avoid known hot areas.
Decades of mapping, testing, and construction have concluded that this portion of A-0009
routed through the Ammons Formation (Zam and Zamh) poses low potential to create
acid rock drainage. Therefore, there are no expectations that deleterious effects will be
encountered.

NCDOT proposes the following monitoring and mitigation plan for sulfide bearing rock
that may be encountered during the construction of A-0009CC.
1. Resident Engineer’s Office will schedule training for all project site inspectors on
how to identify sulfidic rock
2. Kevin Barnett and/or Patrick Breedlove will conduct all necessary training. The
training will include:
a. Identification of acid rock;
b. Testing Zwe including pH, acidity, alkalinity, conductivity, and sulfate
contents from water samples;
c. Discovery of suspected acid rock during construction activities the
following will be implemented:
i. Any rock suspected of containing sulfidic rock will be stockpiled
separately and NCDOT’s Geologist’s Office will be contacted
for verification/testing
ii. Should testing confirm the presence of sulfidic rock and at the
direction of NCDOT’s Geologist, this material shall be amended
appropriately by blending with lime to maintain pH at near
neutral levels
DocuSign Envelope ID: 9678E000-E6C5-465D-BA11-E407F2ED1169

1. Identifying potential waste areas above the water table for
the isolation or temporary storage of potential acid
producing material, or
2. Identifying potential borrow sites for cover material
iii. Retest to include pH, acidity, alkalinity, conductivity, and sulfate
contents

The construction plan will be reviewed and adapted to allow activities to continue while
sulfidic rock is being tested and evaluated.

Best Regards,

Kevin H. Barnett
Division Environmental Supervisor
Division of Highways, Division 14

cc: Jody C. Kuhne, PE
Crystal C. Amschler
DocuSign Envelope ID: 9678E000-E6C5-465D-BA11-E407F2ED1169
9/13/2022 | 8:41 AM EDT