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70-92 Boston Street - Phase 1 Initial Site Investigation and Tier Classification - Appendix D - January 2006 APPENDIX D GEOPHYSICAL SURVEY REPORTS Hager G eoSclenee Inc. f � 596 Main Weet Wobam, MA 01801 � - Te1781.935-8111 Fe1c 781-93542717 i .i July 19, 2004 _ _I Ms. Amy Stattel Y TRC, Inc: Boot Mills South Foot of John'Street VLowell, MA 01852 Re.- Geophysical survey to locate underground storage tanks, 61 Ward Street and FlynnTan sites, Salem, MA. Dear Ms. Stattel: 1 This letter report details the results of a geophysical survey conducted as part of a Brownfields investigation at the 61 Ward Street and the 70-92 Boston Street (F1yanTan)-sites in Salem, Massachusetts. The purpose of the investigation was to locatee possible underground storage tanks at these locations. DATA COLLECTION Survey Control The survey .was conducted on May 26, 2004. Both HGI and TRC on-site representatives determined the survey grid locations and traverse spacing. Traverse locations were marked in the field by HGI personnel using spray paint and fiberglass tapes. Survey control was maintained throughout the survey by taping distances from fixed surface cultural features and noted on the site plan map and survey field notes_ GPR data was collected in all accessible portions of the designated survey areas along traverses in two perpendicular-directions spaced'2.5 feet apart. .The locations of the HGI survey grids and GPR traverses are shown on Figures 1 and 2, adapted from AutoCAD base plans provided by TRC. i r Geophysical.Investigation File 200433 61 Ward Street&70-92 Boston Street(F1ynnTan Site) Page 2 Salem,Massachusetts Data Collection GPR data were collected using a GSSI SIR 3000 system with 400-MHz antenna. A survey wheel was used-for distance control. Data were recorded with the acquisition time window set at 40 nanoseconds(ns). This time range was selected to exceed the estimated maximum two-way signal travel time at these sites. The time.range(s) recorded provided an average depth of signal .penetration of between 10.and 15-feet. Data was displayed in real time on the radar system's color display for quality control and initial data review purposes. All acquired data were stored-on the system's flash memory and transferred to PC-for signal- processing using RADAN for Windows NTIm software. A detailed description of the GPR method and its limitations is presented.in a separate section at the end of this letter report RESULTS Review of the GPR data from the two survey locations exhibits no reflectors characteristic of a buried UST. Please contact us at(781)935-8111 if you have any questions or need additional information. Respectfully yours, HAGER GEOSCIENCE, INC. Daniel J. De ea i" Jutta Hager h.D. Geophysicist President Hager GeoSclence,Inc- Geophysical Investigation File 200433 61 Ward Street& 70-92 Boston Street(F1ynnTan Site) Page 3 Salem,Massachusetts GROUND PENETRATING RADAR eDESCRIPTION OF THE METHOD The principle of ground penetrating radar-(GPR) is the same as that used by police radar,except that GPR transmits electromagnetic energy into the ground. The energy is reflected back to the surface from interfaces between materials with contrasting electrical(dielectric and conductivity) and physical properties. The greater the contrast between two materials in the subsurface, the stronger the reflection observed on the GPR record. The depth of GPR signal penetration depends. on the properties of the subsurface materials and the Pe p Pe frequency of the antenna used to collect radar data. The lower the antenna frequency, the greater the signal penetration, but the lower the signal resolution_ Data .Collection. GPR data are collected using a Geophysical Survey Systems (GSSI) SIR 2000/3000 ground penetrating radar system. GPR-data are digitally recorded on the internal hard drive, or flash-memory of the system. System controls allow the GPR operator to filter out noise, .attributed to both coupling noise, caused by conductive soil conditions, spurious noise caused by local EMF fields and internal system noise. For shallow surveys,we use 400-, 200-, 100- or 1500-megahertz (MHz) antennas. For deeper penetration,. we- uge lower frequency antennas ranging from 200 MHz to 15 MHz, depending on the anticipated depth of the target(s) and the degree of signal penetration_ All of these antenna configurations can collect data in continuous mode or as discrete point measurements using signal-stacking techniques. Since there is a tradeoff between signal penetration and resolution, test lines are run using different antennas at several frequencies.and then the highest frequency antenna that produces the highest quality data is used In some cases, data are collected with several antenna frequencies. The horizontal scale. of the GPR record shows distance along .the survey traverse. In the continuous data collection mode, the horizontal scale on each GPR record'is determined by the antenna speed along the surface.. When a survey wheel is used, the GPR.system records data with a fixed number of traces per unit.distance. The GPR record is automatically marked at specified distance intervals along the survey line. The vertical scale of the radar record is determined by the velocity of the transmitted signal and the recording time window or range_ The recording time interval, or range, represents the maximum two-way travel time in which -data are recorded. The conversion of two-way travel time to depth depends on the propagation velocity of the GPR signal, which is site specific. When little or no information is available about the makeup of subsurface materials, we estimate propagation velocities from handbook values and experience at similar sites or by CDP velocity surveys with a.bi-static antenna_ Data Processing. After completion of data collection, the GPR data are transferred to a PC for review and processing using RADAN NT for WindowsTm software. When appropriate, we prepare 3D models of GPR data, which can be sliced in the Y, Y, and Z directions_ Sager GeoSclence,Inc- Geophysical Investigation File 200433 ) 61 Ward Street&70-92 Boston Street(FlynnTan Site) Page 4. Salem,Massachusetts The size, shape, and amplitude of GPR reflections are used to interpret GPR data. Objects such as metallic DST's and utilities produce reflections with high amplitude and distinctive.hyperbolic shapes. Clay, concrete pipes boulders and other in-situ features may produce radar signatures of similar shape but lower amplitude. The boundaries between saturated-and unsaturated materials such as sand and clay,bedrock and overburden generally also produce strong reflections. LIlVI rATIONS OF THE METHOD GPR signal penetration is site-specific. It is determined by the dielectric properties of local soil and fill materials. GPR signals propagate well in resistive materials such as sand and gravel; however, soils containing clay, ash- or cinder-laden fill or fill saturated with brackish or otherwise electrically conductive groundwater cause GPR signal attenuation and loss of target resolution. Concrete containing rebar or wire mesh also inhibits signal penetration. The interpreted depths of objects detected using GPR are based on on-site calibration, handbook values, and/or estimated GPR signal propagation velocities from.similar sites. GPR velocities and depth estimates may vary if the medium under investigation or soil water content is not uniform throughout the site. Utilities are interpreted on the basis of reflections of similar size and depth that exhibit a linear trend, however GPR cannot unambiguously determine that all such-reflectors are related - Fiberglass UST's; or utilities composed'of plastic or-clay may be difficult to detect if situated in soils with similar electromagnetic properties, or if situated in fill with other reflecting targets which generate "clutter" or signal scattering and thus obscure other deeper reflectors. Objects buried beneath reinforced concrete pads or slabs may also be difficult,but possible,.to detect. Changes in the speed at which the GPR antenna is: moved along the surface causes slight variations in the horizontal scale of the recorded .traverse; Distance interpolation may be performed to minimize the error in interpreted object positions. The variation in the horizontal scale of the GPR record may be controlled,to a certain extent, with a distance encoder-or Survey Wheel. The GPR antenna produces a cone-shaped signal pattern that emanates approximately.45 degrees from horizontal front and back of the antenna. Therefore, buried objects may be detected before the antenna is located directly over them. GPR anomalies may appear larger than actual target dimensions. GPR interpretation is more subjective than other geophysical methods. The interpretive method is based on the identification of reflection patterns that do not uniquely identify a subsurface target. Borings, test pits, site utility plans and other ground-truth are recommended to verify the interpreted GPR results. Hager GeoScience,Inc CM CI1 z o o W H H W ei o EH 4 E'o U. 1b w W � .r ✓ � � � p r-. ff CQ E--4 co h � a J i t 1 t - lu i1i 4-a _J O 'I^L� Rio 7 W 4 Q 1. f y t w z tom. 4 C%l z Us v C 0 ZZ CQ E4 too •Z y fUl na er g o -.ie ace -Inc., - 696 Main Street Woburn, ?a 81W1 T61 M-9354111 Fay 781-M5 2717 - 1 - Cttober 8,2004 File 200468 t Ms. Amy Stattel TRC, Inc. Boott Mills.South Foot of John Street Lowell,MA 01852 Re: Geophysical survey to locate underground storage tanks Former FlynnTan Site, 70 92 Boston Street. Salem,MA. Dear Ms. Stattel: This letter report details the results of a geophysical'survey conducted b Ha er y y g GeoScience,Inc. (HGI)for MC at the former FlynnTan Site at 30-92 Boston Street in Salem.,Massachusetts. The survey was part of a TRC Brownfields investigation. The purpose of the investigation was to locate possible underground storage tanks at the site. DATA COLLECTION SUrve Control The survey was conducted on August 30 2004 gus . Both HGI and TRC on-site representatives determined the survey grid locations and traverse spacing. Traverse locations were marked in the field by HGI personnel using spray paint and fiberglass tapes. Survey control was maintained throughout the survey by taping distances from fixed surface cultural features and noted on the site plan map and survey field notes: GPR data was collected in all accessible portions of the designated survey are as along traverses in two perpendicular directions spaced 2.5 feet apart. The locations of the HGI survey grids and GPR.traverses are shown on Plate 1, an AutoCAD map adapted from a base plan provided by TRC. Geophysical Investigation_ File 200468 FlynnTan Site Page 2 1 Salem,Massachusetts J Data Collection GPR data were collected using a GSSI SIR 3000 system with 400-MHz.antenna. A survey wheel was used for distance control. Data were recorded with the acquisition time window set at 40 nanoseconds (ns). This time range was selected to exceed the estimated maximum two-way. signal travel time at these sites.-The time range(s) recorded provided an average depth of signal penetration of between 10 and 15 feet. Data were displayed in real time on the radar system's color display for quality control and initial data review purposes. All acquired data were stored on the system's flash memory and transferred to.PC for signal processing using RADAN for Windows NTTm software. A detailed description of the GPR method and its I nitations is presented in a separate section at the end of this letter report. RESULTS The results of the GPR survey are shown on Plate 1 and summarized briefly below: Survey Areas North and West of Storage Building. No.USTs were detected in these two survey areas. Several linear features interpreted as probable utilities are plotted on Plate 1. . Westernmost Survey Area by Fence Corner. Two USTs.were identified beneath a reinforced concrete pad in this survey area, where USTs were reportedly present. Plate 1 shows their location and depth; Figure 1.shows a portion of GPR traverse 17.5 E across the western UST. Three additional targets warranting further investigation were also identified in this survey area. We have also plotted their locations and their approximate depths on Plate. 1, as well as several linear features interpreted as probable utilities. Please contact us at_(781)9354111 if you have any questions or need additional information. Respectfully yours, HAGER GEOSCIENCE, INC_ utta Hager, h.D. President Hager GeoScience,Ine- g r ccier�ce* Inc. { 596 Main Street Woburn,-Mk 01801 i UI 701-935-8111 Feu 181-OW2717 October 8,2004 File 200468 Ms. Amy Stattel - TRC, Inc. Boott Mills South Foot of John Street Lowell,MA 01852 1r� L� Re:- Geophysical survey.to locate underground storage tanks F1 Former FiynnTan Site, 70 92 Boston Street Salem,MA. - Dear Ms. Stattel: This letter.report details the results of a-geophysical survey conducted by Hager GeoScience-, Inc. (HGI)for TRC at the former FlynnTan Site at 70-92 Boston Street in Salem,Massachusetts_ The survey was part of a TRC Brownfields investigation. The purpose of the investigation was to locate possible underground storage tanks at the site. DATA COLLECTION Survey Control The. survey was conducted on August 30, 2004. Both HGI and TRC on-site representatives determined the survey grid locations and traverse spacing. Traverse locations were marked in the field by HGI personnel using spray paint and fiberglass tapes. Survey control was maintained throughout the survey by taping distances from fixed surface cultural features and noted'on the site plan map and survey field notes. GPR data was collected in all accessible portions of the designated survey areas along traverses in two perpendicular directions spaced 2.5 feet apart. The locations of the HGI survey grids and GPR traverses are shown on Plate 1, an AutoCAD map adapted from a base plan provided by TRC. i Geophysical Investigation File 200468 F1ynnTan Site• Page 2 Salem,Massachusetts Data Collection -GPR data were collected.using a-GSSI SIR 3000 system with 400-MHz antenna. A survey wheet was used for distance control. -Data were recorded with the.acquisition time window set at 40 nanoseconds (ns). This time range was selected.to exceed.the estimated maximum two-way signal travel time at these sites.-The time range(s)recorded provided an average depth of signal penetration of between 10 and 15 feet. Data were displayed in real time on the radar system's- color display-for quality-control and initial data review purposes. All acquired data were stored on the system's flash memory and transferred to PC for signal processing'using RADAN for Windows NTTm-software. A detailed description of the GPR method and its limitations is presented in a separate section at the end of this letter report. RESULTS The results of the GPR survey are shown on Plate 1. and summarized briefly below: Survey Areas North and'West of Storage Building. No USTs were detected in these two survey areas.. Several linear features interpreted as probable utilities are plotted on Plate.l. Westernmost Survey Area.by Fence Corner. Two USTs were identified beneath a reinforced / concrete pad in this survey.area, where USTs were reportedly.present. .Plate 1 shows their location and depth; Figure 1 shows a portion of GPR traverse 17.5 E across the western UST. Three additional targets warranting further investigation were also identified in this survey area. We have also plotted their-locations and their approximate depths on Plate 1, as well as several linear features interpreted as probable'utilities. Please.contact us at(781)935-8111 if you have any questions or need additional information. Respectfully yours, HAGER GEOSCIENCE, INC. utta Hager,Ph.D_ President Hager GeoScience,Inc. Geophysical Investigation File 200468 F1ynnTan Site Page 3 .Salem,Massachusetts GROUND PENETRATING RADAR DESCRIPTION OF THE METROD The principle of ground penetrating radar(GPR)is the same as that used by police radar,.except that GPR transmits.electromagnetic energy into the ground. The energy is reflected back to the surface from interfaces between materials with contrasting electrical(dielectric and conductivity) L and physical properties. The greater the contrast between two materials in the subsurface,'the stronger the reflection observed on the GPR record. The depth of GPR signal penetration depends on the properties-of the subsurface materials and the frequency of the antenna used to collect radar data. The lower the antenna frequency,the greater the signal penetration, but the lower the signal resolution.- Data Collection: GPR data are collected using a Geophysical Survey Systems(GSSI) SIR 2, SIR 2000,or SIR 3000 ground penetrating radar system. Data are digitally recorded on the internal hard drive or flash memory of the GPR system. System controls allow the GPR operator- to filter out noise,attributed to coupling noise caused by conductive soil conditions, spurious noise caused by local EMT fields,and internal system noise. For shallow surveys,we use 1500-, 900-,400-,or 200-megahertz(MHz) antennas. For deeper penetration, we use lower frequency antennas ranging from 200.MFIZ to 15 MHz, depending on the anticipated target depth and the degree of signal penetration. All of these antenna configurations can collect data in continuous mode, distance mode, or as discrete point measurements using signal-stacking techniques. Since there is a trade-off between signal penetration and resolution, test data-are sometimes collected using antennas at several different frequencies, with the highest frequency antenna that produces the highest quality data used In some..cases,data are collected with several antenna frequencies. The horizontal scale of the GPR record shows distance along the survey traverse. In the continuous data collection mode, the horizontal scale on each GPR record is determined by the antenna speed along the surface. When a survey wheel is used, the GPR system records data with a fined'number of traces per unit distance. The GPR record is' automatically marked at specified. distance intervals along the survey line. The vertical scale of the radar record is determined by the velocity of the transmitted signal in the media under study and the range setting, or recording time window of the GPR system. The recording time .interval, or range, represents the maximum two-way travel time in which data are recorded The conversion of the two-way travel time of the transmitted signals to depth is determined by the propagation velocity of the GPR signal, which is site (media) specific. When little or no information is available about the makeup of subsurface materials, we estimate propagation velocities from handbook values and-experience at similar sites or by CDP velocity surveys with a bi-static antenna. . Data Processing. After.completion of data collection, the GPR data are transferred to a PC for review and processing using RADAN NT for WindowsTm software. When appropriate, we prepare 3D models of GPR data, which can be sliced in the X, Y, and Z directions. Hager GeoScience,Ina Geophysical Investigation File 200468 ) FlynnTan Site Page 4 Salem,Massachusetts The size,shape,-and amplitude of GPR reflections are used to. nterpret GPR data. Objects such as metallic UST's and utilities produce reflections with high amplitude.and distinctive hyperbolic shapes. Clay, concrete pipes boulders and other in-situ features may.produce radar signatures of similar shape but lower amplitude. The boundaries between saturated and unsaturated materials such as sand and clay, bedrock and overburden,generally also produce strong reflections. LIMITATIONS OF THE METHOD GPR signal penetration is site-specific. It is determined by the dielectric properties of local soil and fill materials. GPR signals propagate well in resistive materials such as.sand and gravel; however,soils containing clay, ash-or cinder-laden fill or fill saturated with brackish or . otherwise electrically conductive groundwater cause GPR signal attenuation and loss of target resolution. Concrete containing rebar or wire-mesh also inhibits signal penetration. The interpreted depths of objects detected using GPR are Based on on-site calibration, handbook. values, and/or estimated GPR signal propagation velocities from similar sites. GPR velocities and depth estimates may vary if the medium under investigation or soil water content is not uniform throughout the site. r Utilities are interpreted on the basis of reflections of similar size and depth that exhibit a linear 1 trend; however GPR cannot unambiguously determine that all such reflectors are related. Fiberglass USTs or utilities composed of plastic or clay may be difficult to detect if situated in soils with similar electromagnetic properties,.or if situated in fill with other reflecting targets that generate"clutter"or signal scattering and thus obscure other deeper reflectors. Objects buried beneath reinforced concrete pads or slabs may also be difficult, but possible,to detect. Changes in the speed at which the GPR-antenna is moved along the surface causes slight variations in the horizontal scale of the recorded traverse. Distance interpolation may be performed to minimize the error in interpreted object positions. The variation in the horizontal scale of the GPR record may be controlled,to a certain extent, with a distance encoder or survey wheel. The GPR antenna produces a cone-shaped signal pattern that emanates approximately 45 degrees from horizontal front and back of the antenna. Therefore,buried objects may be detected before the antenna is located directly over them. GPR anomalies may appear larger than actual target dimensions. GPR interpretation is more subjective than other geophysical methods. The interpretive method is based on the identification of reflection patterns that.do not uniquely identify a subsurface target. Borings,_test pits, site utility plans and,other ground-truth are recommended to verify the interpreted GPR results. Sager Geo.Science,Inc. Geophysical Investigation File 200468 i . FlynnTan Site Page 5 Salem,Massachusetts i N S Ll Figure 1. Portion of GPR Traverse-17.5 E across UST in westernmost survey area. Figure also shows rebar in concrete above UST and probable utility nearby(plotted on Plate 1). Each mark on horizontal scale is 4 feet. Vertical scale is derived from conversion of GPR signal velocity to depth in feet. Hager GeoScience, Ina t - RES I UEN TI A LL DI C HGI GPR Traverse Interpreted UST - Possible UST Probable Utility _} f Depths of targets in feet. 1 r 0 5 10 20 40 SCALE in FEET PLATE 1 OCTOBER 2004 �ILE�NO206- 468 GPR INTERPRETATION MAP , FORMER FLYNNTAN SITE owo� 70-92 BOSTON.STREET SALEM, MA Hager GeoScience,Inc. 596 Main Street,Woburn,MA 01801 (781)935-8111 hgi@hagergeoscience.com Base map provided by TRC.