WS-3893_3893_CA_MRP_20081208_DENRcomments

NCDENR
North Carolina Department of Environment and Natural Resources
Michael F. Easley, Governor Division of Waste Management Dexter R. Matthews. Director
William G. Ross Jr., Secretary
December 8, 2008
Colonial Pipeline Company
Attn: Mr. Faron Leigh
411 Gallimore Dairy Road
Greensboro, NC 27409
Reference: Colonial Pipeline — Gasoline Side, 411 Gallimore Dairy Road, Greensboro
Guilford County, North Carolina
GW Incident #3893
Dear Mr. Leigh:
This office acknowledges the receipt of your Semi-annual Monitoring Report — April
2008 Monitoring Event for the subject site on November 20, 2008 from Apex. Your cooperation
is appreciated. After reviewing the report, we have made following comments:
Monitoring wells MW-197, MW-192, MW-144 and MW-124 are discussed in
text, but they can't be located in the figures. Please show the monitoring wells in
figures that you mention in the text.
The report indicates that Hi -Vac Trailer was used to recover free product from
MW-20,'but the amount recovered from three separate events was not reported.
A monitoring well should be installed downgradient from MW-83 that has high
benzene concentration. MW- 41 is more than 350 feet from MW-83 and cannot
be considered as a downgradient well for MW-83.
Based on the thickness and extent of free product in Southern Area, active free
product recovery (MMPE or AFVR) should be used in this area. SVE is not
efficient for free product recovery.

If you have any questions concerning this letter, please contact Gene Mao at (336)
641-3589.
Sincerely,
CindyRintoul, PG
Regional Supervisor
Winston-Salem Regional Office
Cc: Guilford County Health Department
UST Regional Offices
Winston-Salem (WS) — 585 Waughtown Street, Winston-Salem, NC 27107 [phone]
Guilford County Environmental Health, 1203 Maple Street, Greensboro, NC 27405, [phone]