AS-320_5357_CA_LTRRPT_20231121

WithersRavenel
Our People. Your Success.
115 MacKenan Drive | Cary, NC 27511
t: 919.469.3340 | f: 919.467.6008 | www.withersravenel.com | License No. F-1479
ASHEVILLE | CARY | CHARLOTTE | GREENSBORO |PITTSBORO | RALEIGH | SOUTHERN PINES | WILMINGTON

November 21, 2023 State of North Carolina Department of Environmental Quality
Federal & State Lead Program
Division of Waste Management-Underground Storage Tank Section 1646 Mail Service Center Raleigh, North Carolina 27699-1646
Attn: Mr. Scott Ryals, P.E.
RE: LETTER REPORT – MMPE Event Former Riddle’s Exxon 267 Old Mars Highway
Weaverville, Buncombe County, North Carolina
UST # AS-320 Groundwater Incident Number: 5357 WR Project Number: 23-0307-DV
Mr. Ryals:
WithersRavenel, Inc. (WR) has completed a mobile multi-phase extraction (MMPE) event described in task authorization (TA) TA-01 for the above referenced site approved August 29, 2023 under North Carolina Department of Environmental Quality (NCDEQ) Contract #N70522-
C. The site location is depicted on Figure 1 and site features including monitoring well locations
are depicted on Figure 2. MMPE Event WR personnel, along with Eastern Environmental Management, LLC (EEM) mobilized to the site
on October 9, 2023 for the purposes of performing a 96-hour MMPE event. This event was
initiated to recover light, non-aqueous phase liquid (LNAPL) from monitoring well MW-1 and MW-4, as well as dissolved-phase hydrocarbons from MW-3 on the property. In the performance of the MMPE, EEM utilized vacuum extraction equipment mounted within an enclosed trailer. Fluids recovered were contained in a 6,000-gallon (gal) tanker trailer.

On arrival, WR personnel opened and gauged monitoring wells MW-1, MW-3, and MW-4 with a decontaminated product/water interface probe. Gauging of LNAPL within these wells showed the following:
Well ID Depth to LNAPL Depth to Water Well Depth LNAPL Thickness
MW-1 26.19 28.61 36.5 2.42 MW-3 --- 26.36 39.2 ---
MW-4 26.58 26.94 34.75 0.36
[All measurements shown in feet (ft)]

WithersRavenel
Our People. Your Success.
Former Riddle’s Exxon Incident #5357 WR Project No. 23-0307-DV Letter Report – MMPE Event November 2023 Page 2
For completion of MMPE activities, EEM installed 1-inch (in) diameter (dia) poly-vinyl chloride
(PVC) stingers in wells MW-1, MW-3, and MW-4 at depths of 27 to 29-ft beneath the top of casing in each well. These stingers were plumbed at surface to 2-in dia chemical resistant flexible hose, which was connected to a vacuum trunk servicing the vacuum/pressure regenerative blower housed in the equipment trailer. Following setup, the MMPE system was started and run continuously for a period of 96-hours to recover total fluids, including LNAPL and contaminated
groundwater. EEM personnel monitored the performance of the MMPE system over the course of the event, adjusted the stinger depths and optimized recovery as necessary. Through the course of the MMPE event, a combined total of 8,517-gal of fluids were recovered from MW-1, MW-3, and
MW-4. Recovery included total emissions of 2,475.22 pounds or an estimated 396.03-gal of
gasoline as emissions. On October 11, 2023, 4,837 gallons of petroleum contaminated groundwater was then transported off-site for proper disposal at their facility in Rocky Mount, NC. On October 13, 2023, 3,680 gallons of petroleum contaminated groundwater was also transported offsite by EEM for proper disposal. The manifests and disposal document associated
with disposal are included as attachments. Trace amounts of LNAPL present on the recovered
groundwater in the tanker truck at the completion of the event. Airflow rates during the MMPE event ranged from 309- to 392-feet per minute (fpm). System temperature ranged from 68- to 108-degrees Fahrenheit, and relative humidity was 100-
percent. Monitoring of VOC emissions showed initial levels of 9,735 parts-per-million (ppm)
decreasing to 3,687 ppm over the course of the event. After completion of the MMPE event, EEM dismantled the MMPE setup at the location. Wells MW-1, MW-3, and MW-4 were gauged with the interface probe during water recovery after
removal of the stingers. LNAPL was measured at a thickness of 0.11 ft in MW-1 following the
removal of the stingers. LNAPL was not measured in MW-3 and MW-4. Field notes and site photos for the October 2023 MMPE event are included as Attachment A while EEM documentation associated with the event are provided as Attachment B.
WR appreciates the opportunity to be of service to the Federal & State Lead Program. Should
you have any questions regarding the attached, please do not hesitate to contact us at [phone]. Cordially, WithersRavenel

Flora D’Souza, CHMM Elizabeth A. Allyn, P.G.
Environmental Project Scientist II Environmental Project Geologist II
Enclosure(s): Figures Attachment A: Field Notes & Site Photographs Attachment B: EEM MMPE Documentation

FIGURES

500'
1,500'
1,000'
KBB
FD
DRAWN BY:
11/14/2023 23-0307-DV
1
SUBJECT SITE
±0.63 ACRE
SCALE:FIGURE NO.:
PROJECT NO.:DATE:APPROVED BY:
FORMER RIDDLE'S EXXON
TF# 5357
267 OLD MARS HILL HIGHWAY
WEAVERVILLE, BUNCOMBE COUNTY, NC
GENERAL LOCATION MAP
1"=500 '
GRAPHIC SCALE
1 inch = 500 ft.
0 500250 1000
WithersRavenel
Engineers | Planners | Surveyors
115 MacKenan Drive | Cary, NC 27511 | t: 919.469.3340 | license #: C-0832
www.withersravenel.com
OLD MARS HILL HIGHWAYMW-3
MW-4
MW-2
(DESTROYED)
MW-1
FORMER UST
LOCATIONS
(ESTIMATED)
AST
AST
AST
ASTMW-5
(DESTROYED)KBBMJDRAWN BY:12/31/202002171214.952SCALE:FIGURE NO.:PROJECT NO.:DATE:APPROVED BY:SITE MAPWithersRavenelEngineers | Planners | Surveyors115 MacKenan Drive | Cary, NC 27511 | t: 919.469.3340license #: C-0832 | www.withersravenel.com1"=30 'FORMER RIDDLE'S EXXONTF# 5357267 OLD MARS HILL HIGHWAYWEAVERVILLE, BUNCOMBE COUNTY, NCLEGEND
TYPE II MONITORING WELL LOCATION
MUNICIPAL WATER LINE LOCATION
NOTES:
1.) 2020 AERIAL OBTAINED FROM THE LOCAL COUNTY GIS DEPARTMENT.
GRAPHIC SCALE
1 inch = 30 ft.
0 3015 60

ATTACHMENT A

FIELD NOTES
&
SITE PHOTOGRAPHS

PHOTOGRAPH 1 View of onsite building and dispenser island.
PHOTOGRAPH 2 View of MW-1

PHOTOGRAPH 3 View of MW-3

PHOTOGRAPH 4
View of MW-4

ATTACHMENT B

EEM MMPE DOCUMENTATION