t, · 2012. 7. 5. · Nan's Mobil Groundwater Monitoring - August 201I sMs #93-1467 in MW-201 and 0.05 feet was measured in RW-I. Approximately U4 of a gallon of product was pumped

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Nan's MobilCroundwater Monitoring - August 201IsMs #93-1467

l.O INTRODUCTION

Enclosed is the Groundwater Monitoring Report prepared by The Verterre Group (Vertene) to evaluatesubsurface conditions at Nan's Mobil located at 1301 Main Street in Fairfax, Vermont (the Site). ASITE Location Map is provided as Figure 1 and a SITE Plan is presented as Figure 2.

2,0 BACKGROUND

Nan's Mobil is a convenience store located on the north side of Route 104 in Fairfax, Vermont. Thebuilding is used as a convenience store with retail gas station and private residence. The property is onmunicipal water and municipal sewer. The building has a basement and block wall foundation. Thesouthern end of the block wall foundation (front of store) showed signs of deterioration prior to theMarch 2009 excavation activities. The property is heated by an aboveground storage tank (AST)located in the basement of the store.

A sump is located in the basement and gasoline impacted water was present in the sump. The sumpwater discharges to a drainage swale located north of the store. The swale outlets to a privately ownedPond (owned by Reg Barkyoumb). The Pond overflows to a branch of the Tracey Brook which islocated approximately 1,000 feet west of the Site. The Brook discharges to the Lamoille River.

The property contains three underground storage tanks (USTs): a 10,000 gallon gasoline, an 8,000gallon gasoline and a 3,000 gallon split (2,000 gallon diesel and 1,000 gallon kerosene).

Four (4) USTs were removed from the Site on September 15, 1993. These included a2,000 gallondiesel UST; two (2) 4,000 gallon gasoline USTs and a 5,000 gallon gasoline UST. These tanks wereall reported to be in good to excellent condition. Three (3) of the tanks were constructed of steel andone of the 4,000 gallon gasoline tanks was constructed of fiberglass. The 4,000 gallon fiberglassgasoline UST was ruptured by the backhoe, causing contaminated groundwater to flow into the tankand mix with gasoline. Approximately 1,300 gallons of product and water was pumped from the tankprior to its removal from the ground. The soils encountered in the UST excavation consisted of 2.5feet of fill over relatively dry silty clay to a depth of 9 feet below ground surface (bgs). Contaminatedgroundwater was encountered at a depth of approximately 2.5 feet below grade.

During tank removal activities, heavy rain saturated the contaminated soils. It was determined that itwould be best if the contaminated soils were not transported off-site but placed back in the excavation.Twin State Environmental Corporation (TSEC now known as the Verterre Group) recommended toMaclntyre (who was performing the UST closures and replacement) that the excavation for the newtanks be moved further to the northeast to avoid excavating within contaminated soils.

On December 20, 1996, TSEC installed four (4) monitor wells (MW-101, MW-102, MW-103 andMW-104). TSEC noted in the 1993 UST closure report that monitor wells MW-l and MW-2 werealready present. These wells appear to have bracketed the old UST cavity and may possibly have been

installed as tank monitoring wells. The four new monitor wells and the two existing wells were

Verterre Project No. 09006

Nan's MobilGroundwater Monitoring - August 201IsMs #93-1467

sampled on January 2, 1997. Contaminants of Concern (COCs) were present above the VermontGroundwater Enforcement Standards (VGES) in all six wells. TSEC concluded that contamination waslikely being intercepted by the municipal water line and the underground drainage line.

The Site has been overseen by Aquaterra and monitored bi-annually with the latest round conducted inMay 2008. MW-l0l has been abandoned. In the most recent round of groundwater sampling, COCs

were above the VGES in all wells including MW-104 (which is the most down gradient well).

In December 2006, Vertene conducted an assessment during the replacement of the two (2) USTsumps (unleaded and super) and the four (4) spill buckets (unleaded, super, diesel and kerosene) andvisible soil contamination was evident. Elevated PID readings were encountered at approximately the

same depth in all locations (42-48 inches bgs). All soils were backfilled. Groundwater was

encountered at approximately three (3) feet bgs. 600 gallons of groundwater was pumped into a

holding tank during dewatering activities and disposed of by EP&S on December 1, 2006. Areconnaissance of the drainage area located north of the sump area was conducted. No sheens wereevident.

On February 2,2009, Verterre was informed by R.L. Vallee, [nc. (Vallee) of gasoline vapors in the

store and basement at Nan's Mobil and the attached residence. Vallee also reported the issue to the

State of Vermont. The store owner (Peter Parkash) told Verterre that they had observed the odors forapproximately 12 days but hadn't reported it. Verterre immediately responded and screened the

airspace of the store and basement with a photoionization detector (PID). A sump with water and aclay crawl space were observed in the basement. The sump water did not have a sheen on it. Elevated

PID readings were recorded throughout the basement, store and residence.

Verterre returned to the Site on February 3,2009. D&M Petroleum was also on Site and determinedthat gas was leaking from a rusted fitting under the pump island which had broken off. D&M repaired

the fitting. Verterre set up a three (3) leg venting system with a two carbon drum train that vents to the

outside of the building. The vent legs and clay crawl space were polyencapsulated.

On February 4,2009 a drum top blower was set up to vent the air in the basement. An explosion proofblower was not immediately located so the vent legs were not connected to the blower. Instead, the

blower was set up to intercept low level vapors that were rising and making their way into the store.

On February 6, 2009 a t horsepower explosion proof blower was installed and the vent legs were

connected to the drum top blower and plumbed through the two (2) carbon drums. A reconnaissance

of the property was conducted during the site visit. A drainage swale was located approximately 250feet north of the store. The swale contained water without a sheen. A seep was noted downgradient ofthe site to the west in the field across Route 104. No sheens were present. Verterre inspected the

swale on the north side of Route 104 downgradient of the store. The swale was filled with snow and

no signs of product were present.

On February 10,2009 the air space in the store and basement were screened with a PID and allreadings were <0.1 ppmv. Verterre checked the site monitor wells for product and MW-l contained


Nan's MobilGroundwater Monitoring - August 201IsMS #93-1467

approximately fourteen (14) inches of gasoline. Two gallons of product and water were bailed into a55 gallon drum for subsequent disposal. On February 11, 2009 approximately seven (7) inches ofproduct was present in MW-l and approximately 0.25 gallons of gasoline & water were bailed into adrum for subsequent disposal.

Vertene advanced a total of nine (9) soil borings on February 12,2O0g using Verterre's Geoprobe@.

Two of these borings were completed as monitor wells MW-201 andMW-202.

The sump in the basement was inspected and a slight sheen was visible. A sample was collected and

sent to Endyne Laboratories in Williston, Vermont for volatile organic compound analysis. Benzene

\¡/as present at I0.2 micrograms per liter (Vg/l), toluene (98.7 ¡tg1), ethylbenzene (20.5 pgll), xylenes(116 pgll), trimethylbenzenes (36.9 ¡tgll) and naphthalene (6.7 pgll). These levels were above the

allowable discharge concentrations and so the State of Vermont Sites Management Section gave

Verterre permission to set up a treatment system on the sump water and discharge the treated water tothe drainage swale until a discharge permit was received. It was determined that the drainage swaledischarges to a private pond on the neighboring property. The owner of the pond is Reg Barkyoumband the property address is 3 Hillcrest Road. Verterre contacted Mr. Barþoumb and explained the

situation regarding the sump and received verbal permission from him to discharge the treated water tohis pond. Mr. Barkyoumb stated that the drainage swale has appeared oily in the past and that someonefrom the state looked at his water last year and thought the oily film was algae. Verterre recommendssampling the pond in the spring when it thaws. Verterre applied for a discharge permit which was

received on March 2,2009 (NOI 3-41 l5).

The liquid treatment system was set up on the basement sump on February 13,2009. The sump watertravels through two (2) liquid phase carbon canisters and outlets to an existing l.5"effluent line. The1.5" effluent line empties into a four inch line that discharges to the swale at the rear of the property.

Verterre consulted with the SMS and determined that the next step should be to excavate a recoverywell to improve product recovery. Verterre vvas on Site with Martell excavators on February 16,2009to install this recovery well (RW-l). The bottom of the recovery well was set at approximately 7 feet.Clay soils were encountered in the westem end of the excavation; however,at5-7 feet bgs silty sand

was predominant. The lower sidewalls were collapsing into the excavation but gas and water wereflowing into the hole at approximately 6 feet bgs. An 8" pipe slotted to approximately 2' bgs wasplaced into the excavated cavity. The hole was backfilled with stone. The stone was capped withbentonite at approximately 18" bgs, filled with stone to 2" bgs and then topped with asphalt patch. Avery heavy sheen and a small amount of product were present in the well. Approximately, 2 gallons ofwater and product were bailed into the on Site drum for subsequent disposal. The excavated soils were

shipped to ESMI for disposal (5.05 tons).

On February 17,2009, approximately 0.75 gallons of product was pumped from MW-201. OnFebruary 79,2009,0.86 feet of product was measured in MW-201 and approximately l13 of a gallon ofproduct was pumped into the on Site drum. On February 20,2009, 0.73 feet of product was measured

Verterre Proiect No. 09006


in MW-201 and 0.05 feet was measured in RW-I. Approximately U4 of a gallon of product waspumped into the on Site drum from MW-201.

Verterre recommended that when the pump island sumps are being replaced, contaminated soils shouldbe excavated and that the excavation cavity be treated with Regenox and ORC Advanced.

Vertene was on Site with D&M Petroleum (D&M) and Martell Excavation to perform sump

replacement under the gasoline pumps on March 17,2009. Additionally, D&M replaced the primarypiping but the secondary piping remained in place. The piping was not excavated and so thisassessment focuses on the sump areas. The sumps were inspected for cracks after their removal fromthe ground. No visible cracks were observed.

During these planned excavation activities two (2) abandoned USTs were discovered on March 17,

2009. The SMS and UST programs were notified and a 1926letter was generated. The USTs weredetermined to be 1,000 gallon and 2,000 gallon gasoline USTs. A representative from the Town ofFairfax Water Department (Randy Devine) reported that he thought one of the tanks might have

contained kerosene however, Verterre and D&M Petroleum believe both these tanks were gasoline

USTs. The removal of the abandoned USTs was documented under separate cover.

Both tanks were full of water. The SMS gave Verterre permission to pump the water out of the tanks,treat the water and discharge it. The Site has a discharge permit (NOI 3-41 l5). Once the water waspumped and treated from each tank, the tanks were removed from the ground on March 19,2009. Thetanks were in poor condition with numerous holes present. Groundwater was not encountered in thetank cavity.

The additional soil excavation was conducted on March 19th and 20th, 2009. The length of theexcavation was approximately 33 feet long, the width was approximately 15' (except in the area of theabandoned USTs where the length extended to 23'bgs). The depth of the excavation varied. In thearea of the eastern most pump island the excavation extended to approximately l0 feet bgs. At thatdepth PID readings of remaining soils ranged from21 to 40 ppmv. Excavation under the western mostsump extended to only 4.5 bgs because of the water line. Product globules were visible surroundingthe water line, Booms were placed around the water line in an attempt to remove some of the product.Composite sampling of soils that remained in this area had a PID reading of 339 ppmv.

Contaminated soils surrounding the abandoned USTs were excavated and added to the existing soilpile. Soils surrounding the USTs were excavated to approximately 8.5 feet bgs in this area. Because

of the fragile block foundation of the building and the proximity of these tanks to the foundation themaximum depth of the excavation in this area was limited to 8.5 feet bgs.

After the excavation was completed applications of Regenox and ORC Advanced were applied inaccordance with the recommended amounts by Regenesis Corporation on March 20,2009. 240pounds of Regenox A and 240 pounds of Regenox B were mixed with water and evenly distributed


Nan's MobilCroundwater Monitoring - August 201IsMs #93-1467

throughout the excavation cavity. 375 pounds of ORC were mixed with water and also evenlydistributed throughout the excavation cavity.

All soils were temporarily stockpiled under poly until laboratory analysis for waste characterizationwas complete. A total of 175.36 tons of contaminated soil were excavated and disposed of inCoventry. The excavation hole was backfilled with stone and clean frll.

The water treatment system that was connected to the sump and the air system were removed from theSite on May 8, 2009.

Verterre excavated three drums of gasoline contaminated soils from the Nan's Mobil basement onJanuary 14,2010. This soil excavation was documented in the February Bosement Soil ExcavationReport.

The Silva residence, located at 1311 Main Street northwest of Nan's Mobil, was formerly a creamery.Reportedly, a clay drain pipe was installed from the creamery to the Lamoille River to the southwest.The presence of this pipe was confirmed by Mr. Bellows, the owner of the property through which thepipe runs. Verterre met Mr. Bellows on-Site on February 1,2010. Mr. Bellows located three concretecleanouts and a seep on the top of a ravine through which the drain pipe purportedly ran. Water was

noted moving through the cleanouts and the seep is assumed to be located on a broken section of thedrain. Verterre inspected the cleanouts on May 24,20l0,locating a fourth. The four cleanouts werescreened with a PID. All readings were <0.1 ppmv. Vertene then walked the ravine to the LamoilleRiver. Broken sections of clay pipe were noted sticking out of the ground and a small stream formedfrom water runoff from various ravines. No sheens or odors were noted during the inspection.

A 3,000 gallon split diesel/kerosene UST was removed on October 12,201l. Kerosene and diesel are

now sold via aboveground storage tanks (AST). The property is heated via a fuel oil AST in thebasement of the store. Two gasoline USTs (a 10,000 gallon and an 8,000 gallon) installed in 1993

remain in use at the Site. An 8" recovery well installed during a 2009 gasoline release was properlyclosed at the time of this assessment. A previously undocumented tank well was located on the westside of the building (labeled TW-l on Figure 2). The tank well corresponds to the UST cavity fortanks removed in 1993. The tank well is I l' 4" deep and did not have a bailer. Verterre recommendssampling this well during the next round of groundwater sampling.

3.0 COLLECTION OF GROUNDWATER SAMPLES

Verterre performed a limited groundwater sampling at this SITE on August 30,2011 after approvalfrom the SMS. Samples were collected from wells MW-302, MW-303, MW-401 and MW-404. Depthto water was measured in MW-l and MW-201 to aid in the completion of a groundwater contour map.Product was measured at a thickness of 0.01 feet in MW-201.



To allow for a representative groundwater sample, each well was purged of three (3) volumes of waterwith a dedicated bailer. Purge water from the wells was discharged directly to the ground surface.

Sampling at each monitoring well was conducted with dedicated bailers.

Quality assurance/Quality control (QA/QC) samples incorporated into this sampling round includedone (l) duplicate sample taken from monitor well MW-302 and one (1) field blank. Samples collectedfrom monitoring wells were analyzed via US EPA Method 8021 for VOCs. Absolute Resource

Laboratories performed all laboratory analyses for this round of groundwater sampling. The results ofthe groundwater sampling round are discussed in the following sections.

4.0 RESULTS OF SAMPLING ACTIVITIES

4.1 Groundwater Flow Direction

Verterre personnel measured groundwater levels on SITE on August 30,2011. Depth to water ranged

from 2.02 (btoc) to 11.09 feet btoc at monitoring well MW-404 and MW-401, respectively. Asummary of groundwater elevation data is presented in Table 1. A Groundwater Contour Plan is

presented as Figure 3.

Groundwater was interpreted to flow to the northwest at the time of sampling with a hydraulic gradient

of 0.046 feet/foot calculated from MW-201to the 93 foot contour line.

4.2 Analytical Results

The August20ll groundwater sampling results are summarized in Table 2 and the complete anal¡icallaboratory report is provided as Attachment 1. A Contaminant Distribution Plan is presented as

Figure 4. Trend graphs displaying current and historical laboratory data are provided in Appendix A.

The maximum concentration of total Contaminants of Concern (COCs) was found in monitoring wellMW'302 at a concentration of 2I4 micrograms per liter (ryll). COCs were also reported above the

method detection limits (MDLs) in MW-303 (10 pgll) and MW-401 (41 pgll). COCs were not reportedabove the MDLs in MW-404.

Benzene was reported above the Vermont Groundwater Enforcement Standard (VGES) of 5.0 ug/l inMW-302 (90 pgll). Benzene was not reported above the MDL in any other sampled well.

Toluene was reported above the MDL but below the VGES of 1,000 pgll in MV/-302 (2 Ve/l).Toluene was not reported above the MDL in any other sampled well.

Ethylbenzene was reported above the MDL but below the VGES of 700 ¡4llin MV/-302 (45 pgll) andEthylbenzene was not reported above the MDL in any other sampled well.

Total xylenes were not reported above the MDL in any sampled well.



Methyl tert butyl ether (MTBE) was reported above the VGES of 40 ¡tgll in MW-302 (77 pgll) andMW-401 (al pgll). MTBE was reported above the MDL but below the VGES in MW-303 (10 pgll).MTBE was not reported above the MDL in any other sampled well.

Trimethylbenzenes (124 &,135) were not reported above MDL in any sampled wells.

Naphthalene was not reported above the MDL in any sample well.

Since the last sampling round COC levels have fluctuated as follows:

+ increase nc no change nd not detected - decrease ns not sampled fp free productna not applicable

4.3 QA/QC Results

The Relative Percent Difference (RPD) for total COCs in the sample collected from MW-302 and itsduplicate, DUP-I was 57.1Yo. The RPD for MTBE between MW-302 and its duplicate was 5.3o/o.

Typically, a RPD of up to 25o/o is considered to be an acceptable correlation between duplicatesamples. Heavy silt may have resulted in elevated RPD between MW-302 and Dup-I.

Prior to acceptance in this report the laboratory data was evaluated for the following parameters:

o correct sample ID's;. analysis date within method specified holding time;o correct reporting limits;

Well Location coc MTBE Sheen PresentMW-l ns ns ns

MW-2 ns ns ns

MW-102 ns NS ns

MW-103 NS ns NS

MW-I04 ns NS ns

MW-201 ns ns 0.01 ft oroductMW-202 NS ns ns

MW-301 ns ns ns

MW-302 + + noMW-303 T -r no

RW-1 NS ns ns

MV/-401 + + no

MW-402 ns ns NS

MW-403 ns ns ns

MW-404 nclnd nc/nd no


Nan's MobilCroundwater Monitoring - August 201IsMS #93-1467

. acceptable detection limit multipliers;

. acceptable matrix spike (MS) and matrix spike duplicate (MSD) recoveries, where applicable;o acceptable RPD between the MS and MSD, or the sample and duplicate where applicable; and,o acceptablesurrogaterecoveries.

No target analytes were detected above the MDL in the Field Blank.

Based on Verterre's QA/QC evaluation, the data was found to be acceptable.

5.0 SUMMARY AND CONCLUSIONS

Based on the information and anal¡ical data obtained during this investigation, Verterre concludes thefollowing:

o On August 30, 2011 Verterre collected a limited groundwater sampling of some of the off-sitemonitor wells (MW-302, MW-303, MW-401 and MV/-404).

o Product was measured at a thickness of 0.01 ft in monitoring well MW-201. Historicallymeasurable product has been noted and removed from this well.

o VOCs exceeded the VGES in MW-302 and MW-401.

o VOCs were reported above the MDLs but below the VGES in MW-303.

o VOCs were not reported above the MDLs in MW-404.

6.0 RECOMMENDATIONS

MTBE has been reported above the MDLs in two rounds of groundwater sampling of MW-302 andMV/-401 (February and May 2010) and the February 2010 sampling of MW-404. During the previousgroundwater sampling round (May 201l), MTBE was not reported above the MDL in MW-302, MW-401 or MV/-404 likely due to high groundwater limiting the movement of containments from thesource area. During this groundwater sampling round (August 20ll) MTBE was reported above theVGES in MW-302 and MW-401 but below MDL in MW-404. These wells are located across Route104. The contamination appears to be following septic and water lines indicating that the Site widecontamination is actively migrating.

This coupled with the fact that contamination shows up periodically in the on Site sump indicate theneed for a Corrective Action Feasibility Investigation (CAFI). The intent of a CAFI is to determinewhat corrective action technology would be best suited for this Site. The CAFI will be used to evaluatedifferent technologies and select an appropriate corrective action strategy. If the SMS concurs thenVertene will prepare a cost estimate for the preparation of a CAFI.


Nan's MobilGroundwater Monitoring - August 201IsMS #93-t467

A planned housing development is underway across Route 104 to the southeast. According to theTown of Fairfax V/ater and Sewer Department, l8 units are being built. The units will be serviced by Iprivate well and two community wells. Reportedly one of the wells has been drilled and has a yield of24 gallons per minute. Vertene recommends that the boring logs be obtained for these supply wellsand that the wells be sampled for volatile organic compounds by US EPA Method 524.2.

Verterre recommends that a full round of sampling be conducted in August 2012. All monitor wellswill be sampled at that time. The seeps and pond will also be sampled. The sump is being sampledunder the discharge permit and will be sampled in accordance with those requirements.

A previously undocumented tank well was located on the west side of the building (labeled TW-l onFigure 2) during the October 20ll UST Closure. The tank well corresponds to the UST cavity fortanks removed in 1993. The tank well is ll' 4" deep and did not have a bailer. Verterre recommendssampling this well during the next round of groundwater sampling and surveying it into the site plan.

G :\0803 I lreports\08 I I GlltR.doc

Vertene Project No. 09006

t, · 2012. 7. 5. · Nan's Mobil Groundwater Monitoring - August 201I sMs #93-1467 in MW-201 and 0.05 feet was measured in RW-I. Approximately U4 of a gallon of product was pumped

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