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ft*, ' • ' ' GOLDMAN ANTONETTI CORDOVA & AXTMAYER ATTORNEYS AND COUNSELORS AT LAW AMERICAN INTERNATIONAL PLAZA FOURTEENTH FLOOR 25O MUNOZ RIVERA AVENUE NATO REY, PUERTO RICO OO9I8 Ref. 2092.003 POST OFFICE BOX 7O364 FRANCIS TORRES SAN JUAN, PUERTO RICO OO936-O3S4 PARTNER TELEPHONE (8O9) 7S9-8OOO (809) 759-4125 TELECOPIER (SO9) 767-9333 April 5, 1993 VIA FEDERAL EXPRESS Mrs. Caroline Kwan Emergency and Remedial Response Division Caribbean Superfund Branch II U. S. Environmental Protection Agency Region II - Room 747 Jacob K. Javits Federal Building New York, NY 10278 Dear Ms. Kwan: Attached please find a copy of the soil gas survey report prepared by Target Environmental Service, containing results of an investigation conducted at the Four Winds Shopping Center on the vicinity of the Western Auto store. In addition, enclosed please find correspondence from Bruce Green, Four Wind's litigation expert, to Clifford Crook of the Department of Planning and Natural Resources regarding certain conflicting analytical results. To say the least, the conflict referred to in Bruce Green's letter gives credence to Geraghty & Miller's recommendation that the TEIC should investigate the potential release of petroleum products and hazardous substances from the Four Wind's tanks. Please call if you have any questions. Sincerely yours, Francis Torres nro Enclosure TUT 006 1566 *64809* 64809 1 I _ SOIL GAS SURVEY UST AREAS 1 FOUR WINDS SHOPPING CENTER 1 TUTU AREA, ANNA'S RETREAT I UNITED STATES VIRGIN ISLANDS I PREPARED FOR i LAW OFFICE OF JOHN K DEMA, P.C 1236 STRAND STREET, SUITE 103 CHRISTIANSTED, ST. CROIX, VIRGIN ISLANDS 00820-5008 PREPARED BY TARGET ENVIRONMENTAL SERVICES, INC 9180 RUMSEY ROAD COLUMBIA, MARYLAND 21045 (410) 992-6622 SEPTEMBER 1992 TUT OO6 1567 I if" L TABLE OF CONTENTS I EXECUTIVE SUMMARY ............................................. ii I Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 i Sample Collection and Analysis .......................................... 2 Quality Assurance/Quality Control (QA/QC) Evaluation ......................... 3 I Results ........................................................... 4 • Interpretation ...................................................... 5 Conclusions ........................................................ 6 FIGURES Figure 1. Sample Locations Figure 2. Total FID Volatile* Figure 3. Tetrachloroethene (PCE) TABLES Table 1. Sampling Depth Table 2. Analyte Concentrations via GC/FID Table 3. Analyte Concentrations via GC/ECD APPENDICES APPENDIX A - Field Procedures APPENDIX B - Laboratory Procedures APPENDIX C - Detectability & Terminology TUT OO6 1568 I « A EXECUTIVE SUMMARY 1 On September 3, 1992, TARGET Environmental Services, Inc. (TARGET) conducted a soil I gas survey in the UST Areas on the western side of the Four Winds Shopping Center, Tutu Area, • - Anna's Retreat, U.S. Virgin Islands. A total of 35 soil gas samples were collected from depths of 2 to 4 feet and analyzed on a gas chromatograph equipped with a flame ionization detector I (GC/FID) for petroleum hydrocarbons and with an electron capture detector (GC/ECD) for _ chlorinated hydrocarbons. The objectives of the survey were (1) to determine whether reported underground storage tanks (USTs) in this area have contributed to the hydrocarbon occurrences I previously delineated within the parking lot and service station areas on the eastern side of the shopping center buildings, and (2) to determine whether the reported USTs or any other source on the west side of the shopping center buildings have caused significant contamination to the soils or the aquifer in this immediate area. ' A low level of Total FID Volatiles was present in Sample 313, collected adjacent to the Western Auto garage. Very low levels occurred in the samples extending westward to the property line and in one sample from the northwestern corner of the survey area. The FID chromatogram signature of Sample 313 reveals only very small peaks representing very low levels of petroleum hydrocarbons. GC/ECD analysis revealed low levels of tetrachloroethene (PCE) in several samples from the northern portion of the survey area between the buildings, as well as in two samples collected adjacent to the southwestern corner of the Four Winds Plaza building. None of the remaining chlorinated analytes were present above the 1 fig/1 reporting limit in any of the samples. The volatile hydrocarbons observed adjacent to the Western Auto garage may be related to the suspected UST in this area. The very low level observed, however, does not suggest the presence of significant residual petroleum hydrocarbons in the subsurface. A comparison of map " TUT 006 1569 patterns from the soil gas survey conducted in January 1992 suggests that this occurrence is not related, nor is it contributing to the occurrence on the eastern side of the shopping center. No source is evident in the immediate area for the low levels of PCE observed north and southwest f of the Four Winds Plaza building. 1 I I I •^f I HI • '°"""*-~ TUT OO& 157O { 1 TARGET Project MVIS3 I Introduction The Law Office of John K. Dema (Dema) contracted TARGET Environmental Services, Inc. I (TARGET) to perform soil gas survey in the UST Areas on the western side of the Four Winds I Shopping Center, Tutu Area, Anna's Retreat, U.S. Virgin Islands. Subsurface petroleum and chlorinated hydrocarbons have previously been detected within the parking lot and service station I areas on the eastern side of the shopping center. Two underground storage tanks (USTs) have I been reported to be located within this survey area west of the shopping center buildings. One was allegedly used prior to 1985 for waste oil. The other is reportedly a diesel fuel oil tank for j Western Auto's emergency generator. No known releases have been reported. The objectives of , the soil gas survey were (1) to determine whether reported underground storage tanks (USTs) in this area have contributed to the hydrocarbon occurrences previously delineated within the parking f~*^- lot and service station areas on the eastern side of the shopping center buildings, and (2) to determine whether the reported USTs or any other source on the west side of the shopping center buildings have caused significant contamination to the soils or the aquifer in this immediate area. The survey was designed to cover the area around the suspected USTs, between the buildings and the western property line. The survey area is covered with pavement. The soils consist of permeable stratified sands, gravel, and clay up to 20 feet thick over fractured bedrock. The ground water fluctuates from a rainy season high of 20 feet below grade to a dry season low of about 90 feet below grade. A 4 foot sampling depth was planned. The field phase of the soil gas survey was conducted on September 3, 1992. TUT 006 i ' TARGET Project MVIS3 s~\. Sample Collection and Analysis Soil gas samples were collected at a total of 35 locations at the site, as shown in Figure 1. Several samples were collected shallower than the proposed 4 foot depth due to probe refusal, as | reported in Table 1. This slight variation in depth is not sufficient to adversely affect the comparability of the data. A detailed explanation of the sampling procedure is provided in ' Appendix A. | All of the samples collected during the field phase of the survey were subjected to dual analyses. One analysis was conducted according to EPA Method 601 (modified) on a gas T i chromatograph (GC) equipped with an electron capture detector (ECD), and using direct injection. Specific analytes standardized-f5r this analysis were: 1,1-dichloroethene (11DCE) methylene chloride (CH2C12) f~*\ trans-l,2-dichloroethene (H2DCE) 1,1-dichloroethane (11DCA) cis-l,2-dichloroethene (c!2DCE) chloroform (CHCy 1.1.1-trichIoroethanc (111TCA) carbon tetrachloride (CC14) trichloroethene (TCE) 1.1.2-trichloroethane (112TCA) tetrachloroethene (PCE) The chlorinated hydrocarbons in this suite were chosen because of their common usage in industrial solvents, and/or their degradational relationship to commonly used compounds. The second analysis was conducted according to EPA Method 602 (modified) on a gas chromatograph (GC) equipped with a flame ionization detector (FID), and using direct injection. The analytes selected for standardization in this analysis were: methyl tertiary butyl ether (MTBE) ethylbenzene benzene meta- and para- xylene toluene ortho- xylene TUT 006 1572 - * TARGET Project HVI33 /—v These compounds were chosen because of their utility in evaluating the presence of fuel products, or petroleum based solvents. An explanation of the laboratory procedures is provided in • Appendix B. 1 The tabulated results of the laboratory analyses of the soil gas samples are reported in micrograms per liter (^tg/l) in Tables 2 and 3. Although "micrograms per liter" is equivalent to • "parts per billion (vfv)" in water analyses, they are not equivalent in gas analyses, due to the • difference in the mass of equal volumes of water and gas matrices. Because pentane and MTBE co-elute, they are listed together in Table 2. The xyienes concentrations reported in Table 2 are I the sum of the m- and p-xylene and the o-xylene concentrations for each sample. I Quality Assurance/Quality Control (QA/QO Evaluation Held QA/QC Samples . Field control samples were collected at the beginning and end of the day's field activities and after the twentieth soil gas sample. These QA/QC samples were obtained by filtering ambient I air through a dust and organic vapor filter cartridge and encapsulating as described in the "Field Procedures" in Appendix A. The laboratory results of the analysis of these samples are reported in Tables 2 and 3. Concentrations of all analytes were below the reporting limit in all field control samples, indicating that the QA/QC measures employed were sufficient to prevent cross- contamination of the samples during collection. Laboratory QA/QC Samples To document analytical repeatability, a duplicate analysis was performed on every tenth field sample. Laboratory blanks of nitrogen gas were also analyzed after every tenth field sample. The results of these analyses are reported in Tables 2 and 3. The duplicate analyses were within TUT OO<b 1573 X TARGET Project MVIS3 I acceptable limits. Concentrations of all analytes were below the reporting limit in all laboratory blanks. 1 Results In order to provide graphic presentation of the results, the tetrachloroethene (PCE) and Total * FID Volatiles data sets in Tables 2 and 3 have been mapped and contoured to produce Figures I 2 and 3. The sampling locations from the previous site visit are also shown. Map sample points from the current survey with no data shown indicate that the analyte concentrations in the sample I were below the reporting limit. An explanation of the terminology used in this report is provided ~*t I in Appendix C. A low level of Total FID Volatiles (Figure 2) was present adjacent to the Western Auto /—N garage in Sample 313. Very low levels were present in the samples extending westward to the [ property line and in one sample from the northwestern corner of the survey area (Sample 337). Very low levels of toluene and xylenes (not mapped) were present only in Sample 313. None of the remaining petroleum analytes were present above the 1 /ig/1 reporting limit in any of the samples. GC/ECD analysis revealed low levels of PCE (Figure 3) in several samples from the northern portion of the survey area between the buildings, as well as in two samples collected adjacent to the southwestern corner of the Four Winds Plaza building. None of the remaining chlorinated analytes were present above the l'/ig/l reporting limit in any of the samples. TUT OO6 1574 k I 1 1 I I \ I 1 TARGET Project MVIS3 Interpretation The volatile petroleum hydrocarbons observed adjacent to the Western Auto garage may be related to the suspected UST in this area. The levels are typical of "background" concentrations often observed in auto service areas and do not appear to represent a release from a UST. The FID chromatogram signature of Sample 313 (left) reveals only very small peaks representing very low levels of petroleum hydrocarbons. The pattern is insufficient to allow chromatographic interpretation of the original material. The very low level observed, however, does not suggest the presence of significant residual petroleum hydrocarbons in the subsurface. A comparison of map patterns from the soil gas survey conducted in January 1992 suggests that this occurrence is not related nor is it contributing to the occurrence on the eastern side of the shopping center. No source in the immediate area is evident for the low levels of PCE observed north and southwest of the Four Winds Plaza building. Sampling through the floor of the buildings would be necessary to determine whether the PCE observed west of the shopping center is related to the occurrence in the parking lot to the east. * GC/FID Chromatogram Signature of Sample 313 TUT 006 1575 ii /*~N TARGET Project MVIS3 1 Conclusions •• Very low levels of petroleum hydrocarbons are present west of the Western Auto garage. • + The occurrence may be related to the suspected UST in the area, but does not appear to be related or contributing to the occurrences on the eastern side of the shopping center. | *• The levels are typical of "background" concentrations often observed in auto service areas and do not appear to represent a release from a UST. i >• Low levels of tetrachloroethene (PCE) are present north and southwest of the Four Winds Plaza building. No source for this occurrence is evident in the immediate area. i i i i I i 006 1576 PROPERTY LINE H C GRACE TUTU GOSPEL CHAPEL PROPERTY FEET • SOU. GAS SAMPLE LOCATION o NOT SAMPLED (UNCOLLECTABLE) « MONITORING WELL + WATER SUPPLY WELL D PREVIOUSLY SAMPLED LOCATION ENVIRONMENTAL SERVICES. INC. I lhis met is Mural to o irittai r»crt 11 and should Ixvbedh that antexl || FIGURE 1. Sample Locations FOUR WINDS SHOPPING CENTER AND ENVIRONS TUTU AREA. ANNA'S RETRFAT TEXACO PROPERTY PROPERTY LINE GRACE TUTU GOSPa CHAPEL PROPERTY APPROXIMATE | LOCATION Of I AMUAL HOSPITAL I FEET • SOIL GAS SAMPLE LOCATION o NOT SAMPLED (UNCOUECTABLE) O MONITORING WELL + WATER SUPPLY WELL G PREVIOUSLY SAMPLED LOCATION ENVIRONMENTAL SERVICES. INC. Ihb map K integral to a iritta report and should be wied h that context FIGURE 2. Total FID Volatiles (calc'd/»g/l) FOUR WINDS SHOPPING CENTER AND ENVIRONS TUTU AREA, ANNA'S RETREAT IIMITCTl CTATTO XII-./M.1 —— ...-- TEXACO PROPERTY PROPERTY IJNE IIIIIIIII I I H C H O O Q- U5 GRACE TUTU GOSPa CHAPa PROPERTY FEET • SOIL GAS SAMPLE LOCATION a NOT SAMPLED (UNCOUECTABLE) O MONITORING WELL + WATER SUPPLY WELL O PREVIOUSLY SAMPLED LOCATION ENVIRONMENTAL SERVICES. INC. This map b htegrd to a written report ond shwU be teed h that context FIGURE 3. Tetrachloroethene (PCE) fog/0 FOUR WINDS SHOPPING CENTER AND ENVIRONS ' TUTU AREA, ANNA'S RETREAT 1 J I I I I 1 i I I I 1 1 I 1 I TABLE 1 SAMPLING DEPTH SAMPLE FEET 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 3 4 2 3 2 3 4 2 4 4 3 4 4 4 4 4 4 4 4 4 4 2 4 4 2 3 4 2 4 4 4 3 3 4 4 TARGET Project MVIS3 TUT 006 1580 X I TARGET Project MVIS3 TABLE 2. ANALYTE CONCENTRATIONS VIA GC/FID 1 I 1 I 1 1 1 _. ^—— N 1 1 I 1 1 I i 1 1 PENTANE/ ETHYL- SAMPLE MTBE1 BENZENE TOLUENE BENZENE REPORTING LIMIT 1.0 1.0 1.0 1.0 306 <1.0 <1.0 <1.0 <1.0 307 <1.0 <1.0 <1.0 <1.0 308 <1.0 <1.0 <1.0 <1.0 310 <1.0 <1.0 <1.0 <1.0 311 <1.0 <1.0 <1.0 <1.0 312 "<1.0 <1.0 <1.0 <1.0 313 <1.0 <1.0 2.0 <1.0 314 <1.0 <1.0 <1.0 <1.0 315 <1.0 <1.0 *1 .0 <1.0 316 <1 .0 <1.0 <1.0 <1.0 317 <1.0 <1.0 <1.0 <1.0 319 <1.0 <1.0 <1.0 <1.0 320 <1.0 <1.0 <1.0 <1 321 <1.0 ~ <1.0 <1.0 <1.0 322 <1.0 <1.0 <1.0 <1.0 323 <1.0 <1.0 <1.0 <1.0 324 <1.0 <1.0 <1.0 <1.0 325 <1.0 <1.0 <1.0 <1.0 326 <1.0 <1.0 <1.0 <1.0 327 <1.0 <1.0 <1.0 <1.0 328 <1.0 <1.0 <1.0 <1.0 329 <1.0 <1.0 <1.0 <1 330 <1.0 <1.0 <1.0 <1.0 331 <1.0 <1.0 <1.0 <1.0 332 <1.0 <1.0 <1.0 <1.0 333 <1.0 <1.0 <1.0 <1.0 334 <1.0 <1.0 <1.0 <1 335 <1.0 <1.0 <1 .0 <1.0 336 <1.0 <1.0 <1 .0 <1 «0 337 <1.0 <1 .0 <1 .0 <1.0 338 <1.0 <1.0 <1.0 <1.0 339 <1.0 <1.0 <1.0 <1.0 340 <1.0 <1.0 <1.0 <1.0 FIELD CONTROL SAMPLES 302 <l!o <l!o <l!fl <\'.Q 303 <1.0 <1.0 <1.0 <1.0 1 CONCENTRATIONS BASED ON RESPONSE FACTOR OF MTBE 2CALCULATED USING THE SUM OF THE AREAS OF ALL INTEGRATED CHROMATOGRAM PEAKS AND THE TOLUENE TOTAL FID XYLENES VDUTILES2 1.0 1.0 <1.0 <1. ^1.0 *1 .0 <1 .0 *1 .0 *1 .0 *1 .0 ^1.0 <1 »0 <J ^Q <^ BQ <^ BQ <^ fQ 1.2 77 <1.0 <1.0 <1.0 9.4 <1.0 1.2 <1.0 3.8 <^ BQ <^ ^Q ^1.0 ^1.0 <^ .0 ^1 «0 <^ ^Q <^ ^Q <^ ^Q <^ BQ <^ ^Q <^ aQ <^ 4Q <^ BQ 1 ^-1 «0 ^1 «0 <1 *0 ^1 .0 <^ ^Q <^ aQ <^ aQ <^ BQ <^ ^Q <^ ^Q *1*0 *^1«0 <^ ^Q <^ ^Q <^ ^Q <^ aQ <^ BQ <^ BQ <1.0 2.1 <1.0 <1.0 <1.0 <1.0 <1.0 <1.0 <^ ^Q <^ ^Q <^ ,0 ^1 »0 <1.0 <1.0 INSTRUMENT RESPONSE FACTOR F TUT OO6 1581 V A 1 I I I I I I I ! TARGET Project MVIS3 TABLE 2 (CONn ANALYTE CONCENTRATIONS VIA GC/FIO (<ig/l) PENTANE/ ETHYL- TOTAL FID SAMPLE_______MTBE1________BENZENE________TOLUENE_______BENZENE_______XYLENES______VOLATILES* REPORTING LIMIT 1.0 1.0 1.0 1.0 1.0 1.0 LABORATORY DUPLICATE ANALYSIS 312 ^10 *1»0 <1»0 <1«0 ^1,0 <1»0 312R * 1 • 0 < 1 • 0 ^ 1 • 0 ^ 1 • 0 ^ 1 • 0 < 1 • 0 322 <1 «0 <1.0 <1,0 <1 «0 <1.0 <1.0 322R <1 «0 <1.0 <1«0 <1 «0 <1«0 <1.0 332 <1«0 <1.0 <1,0 <1.0 <1»0 <1»0 340 <1.0 <1.0 <1«0 <1.0 <1.0 <1.0 LABORATORY BLANKS 3128 ^1.0 <1.0 <1.0 <1 »0 <1 «0 <1 *0 322B <1«0 <1*0 <1.0 <1 »0 < 332B <1«0 <1.0 <1.0 <1«0 < 340B *1*0 <1 *0 <1«0 <1«0 <1«0 ! ^*N. , CONCENTRATIONS BASED ON RESPONSE FACTOR Of MTBE 2CALCULATED USING THE SUM OF THE AREAS OF ALL INTEGRATED CHROHATOGRAM PEAKS AND THE INSTRUMENT RESPONSE FACTOR FOR TOLUENE TUT 006 1582 I X I I I I I I I IIIIII JLI 1 TARGET Project MVIS3 SAMPLE 11DCE CHoCU t12DCE TABLE 3 ANALYTE CONCENTRATIONS VIA GC/ECD (ftg/l) 11DCA C12DCE CHCU 111TCA CCt.. TCE 112TCA PCE REPORTING LIMIT 1.0 1.0 306 <1.0 <1.0 307 <1.0 <1.0 308 <1.0 <1.0 309 <1.0 <1.0 310 <1.0 <1.0 311 <1.0 <1.0 312 <1.0 <1.0 313 <1.0 <1.0 314 <1.0 <1.0 315 <1.0 <1.0 316 <1.0 <1.0 317 <1.0 <1.0 318 <1.0 <1.0 319 <1.0 <1.0 320 <1.0 <1.0 321 <1.0 <1.0 322 <1.0 <1.0 323 <1.0 <1.0 324 <1.0 <1.0 325 <1.0 <1.0 326 <1.0 <1.0 327 <1.0 <1.0 328 <1.0 <1.0 329 <1.0 <1.0 330 <1.0 <1.0 331 <1.0 <1.0 332 <1.0 <1.0 333 <1.0 <1.0 334 <1.0 <1.0 335 <1.0 <1.0 336 <1.0 <1.0 337 <1.0 <1.0 338 <1.0 <1.0 339 <1.0 <1.0 340 <1.0 <1.0 FIELD COHTROL SAMPLES 301 <1.0 <1.0 302 <1.0 <1.0 303 <1.0 <1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.1 1.2 1.8 3.2 1.4 1.8 <1.0 1.2 1.2 11DCE I12DCE C12DCE 111TCA TCE PCE 1,1-dichloroethene trans-1,2-dichloroethene cis-1,2-dichloroethene 1,1.1-trichloroethane trichloroethene tetrachloroethene 110CA CHClg CC14 112TCA •ethylene chloride 1.1-dichloroethane chlorofonn carbon tetrachloride 1.1.2-trichloroethane TUT OO6 1583 1 I 1 1 I 1 1 I 1 TARGET Project MVIS3 TABLE 3 (COHn • ANALYTE CONCENTRATIONS VIA OC/ECD <M9/l> SAMPLE——11DCE———CHoCl? t12DCE 110CA c12DCE CHClg 111TCA CCl, TCE 112TCA PCE • REPORTING LIMIT 1-° i-o 1.0 1.0 i.o i.o 1.0 i.o 1.0 1.0 i.o LABORATORY DUPLICATE ANALYSIS HL "!*!! <1>0 <1-° <1-° "*-° <1-° <1-° <1-° <l-° <i.o <i o 312R <1-° «i-° <LO <i.o <i.o <i.o <i.o <i.o < HI <1-° <1-° <i.o <i.o <i.o <i.o <i.o <i.o 322R <1.0 <1.0 <1.0 <1.0 <1.0 <1.0 <1 n ,1 n -in 332 <1.0 <1.0 <1.0 <1.0 <1.0 <1.0 332R <1.0 <1.0 <1.0 <1.0 <1.0 <1.0 340 <1.0 <1.0 <1.0 <1.0 <1.0 <1.0 340R <1.0 <1.0 <1.0 <1.0 <1.0 <1.0 LABORATORY BLANKS 312B <1.0 <1.0 <1.0 <1.0 <1.0 <1.0 322B -O.O <1.0 <1.0 ~<1.0 <1.0 <1.0 332B <1.0 <1.0 <1.0 <1.0 <1.0 <1.0 3408 <1.0 <1.0 <1.0 <1.0 <1.0 -O.O •0.0 1 11DCE * 1,1-dichloroethene CHgClg > acthylene chloride t12DC£ = trans-1.2-dichloroethene 11DCA * 1,1-dichloroethane c12DCE » cis-1,2-dichloroethene CHC13 = chlorofora '***WN 111TCA * 1,1,1-trichloroethane CC14 * carbon tetrachloride TCE * trichloroethene 112TCA = 1.1.2-trichloroethane f PCE = letrachloroethene TUT OOfc 1584 - i A I 1 1 APPENDIX A FIELD To collect the samples a 1/2 inch hole was produced to a depth of approximately 4 feet by I using a drive rod. Where pavement was present, a rotary hammer was employed for penetration prior to using the drive rod. The entire sampling system was purged with ambient air drawn • through an organic vapor Glter cartridge, and a stainless steel probe was inserted to the full depth I of the hole and sealed off from the atmosphere. A sample of in-situ soil gas was then withdrawn through the probe and used to purge atmospheric air from the sampling system. A second sample • of soil gas was withdrawn through the probe and encapsulated in a pre-evacuated glass vial at two I atmospheres of pressure (15 psig). The self-sealing vial was detached from the sampling system, packaged, labeled, and stored tor laboratory analysis. • Prior to the day's field activities all sampling equipment, slide hammer rods and probes were f ^ ~ . decontaminated by washing with soapy water and rinsing thoroughly. Internal surfaces were flushed dry using pre-purified nitrogen or filtered ambient air, and external surfaces were wiped clean using 1 clean paper towels. 1 1 1 TUT OO6 1585 1 1 1 J 1 APPENDIX B LABORATORY PROCEDURES g The analytical equipment was calibrated using a 3-point instrument-response curve and 9 injection of known concentrations of the target analytes. Retention times of the standards were ^ used to identify the peaks in the chromatograms of the field samples, and their response factors were used to calculate the analyte concentrations. • Total FID Volatiles values were generated by summing the areas of all integrated chromatogram peaks and calculated using the instrument response factor for toluene. Injection I peaks, which also contain the light hydrocarbon methane, were excluded to avoid the skewing of 1 Total FID Volatiles values due to injection disturbances and biogenic methane. For samples with low hydrocarbon concentrations, the calculated Total FID Volatiles concentration is occasionally • lower than the sum of the individual analytes. This is because the response factor used for the /"""V • Total FID Volatiles calculation is a constant, whereas the individual analyte response factors are compound specific. It is important to understand that the Total FID Volatiles levels reported are • relative, not absolute, values. I TUT 006 1586 J X 1 APPENDIX C DETECTABELITY & TERMINOLOGY I Detectabilitv The soil gas survey data presented in this report are the result of precise sampling and measurement of contaminant concentrations in the vadose zone. Analyte detection at a particular 1 location is representative of vapor, dissolved, and/or liquid phase contamination at that location. The presence of detectable levels of target analytes in the vadose zone is dependent upon several " factors, including the presence of vapor-phase hydrocarbons or dissolved or liquid concentrations 1 adequate to facilitate volatilization into the unsaturated zone. * Terminology ^ In order to prevent misunderstanding of certain terms used in TARGETs reports, the following clarifications are offered: J Analyte refers to any of the hydrocarbons standardized for quantification in the chromatographic 1 analysis. Anomaly refers to an area where hydrocarbons were measured in excess of what would normally I be considered "natural" or "background" levels. «i Elevated and significant are used to describe concentrations of analytes which indicate the existence of a potential problem in the soil or ground water. J Feature is used in reference to a discernible pattern in the contoured data. It denotes a contour 1 form rather than a definite or separate chemical occurrence. Indicates is used when evidence dictates a unique conclusion. Suggests is used when several explanations of certain evidence are possible, but one in particular seems more likely. As _ a result, "indicates" carries a higher degree of confidence in a conclusion than does "suggests." 1 TUT 006 1587 APPENDK C Occurrence is used to indicate an area where chemical compounds are present in sufficient concentrations to be detected by the analysis of soil vapors. The term is not indicative of any specific mode of occurrence (vapor, dissolved, etc.), and does not necessarily indicate or suggest the presence of "free product" or "phase-separated hydrocarbons." Reporting Limit refers to the minimum concentration reported for each analyte. Vadose zone represents the unsaturated zone between the ground water table and the ground surface. TUT OO6 1588