INDUCED POLARIZATION (IP) AND RESISTIVITY DATA ACQUISITION IS A COST-EFFECTIVE, NON-INTRUSIVE, FAST METHOD FOR DETERMINING THE SOIL COVER THICKNESS, FOOTPRINT (LATERAL) AND VERTICAL EXTENT OF BURIED WASTE MATERIAL. WITH STATIONS EVERY 7.5 FEET AND LINES EVERY 30 FEET, A THREE PERSON FIELD CREW CAN COVER APPROXIMATELY 1.5 ACRES IN A TYPICAL FIELD DAY. DATA COVERAGE RANGES FROM THE SURFACE TO A DEPTH OF 30-40 FEET. GREATER DEPTHS CAN BE EASILY ACHIEVED BY CHANGING THE PARAMETERS OF THE SURVEY.
INDUCED POLARIZATION (IP) IS A COMMON TOOL IN MINERALS EXPLORATION, BUT IT IS LESS-COMMONLY APPLIED TO ENVIRONMENTAL PROBLEMS DUE TO THE EXPENSE. HOWEVER, MULTI-CHANNEL RECEIVERS, USED IN CONJUNCTION WITH MULTIPLEXERS, NOW ALLOW RAPID, INEXPENSIVE SURVEYS AT MANY SITES. THE ADDITION OF IP INFORMATION TO THE STANDARD RESISTIVITY DATA ALLOWS MORE COMPREHENSIVE INTERPRETATIONS, AND IN MANY CASES, THE IP DATA HAVE BEEN THE DEFINITIVE INDICATOR OF SUBSURFACE WASTE. IN MODERATE AND LOW RESISTIVITY ENVIRONMENTS, WHERE THERE IS LITTLE CONTRAST BETWEEN THE LOW RESISTIVITY WASTE AND BACKGROUND, IP ANOMALIES INDICATE WASTE, WHILE RESISTIVITY DATA PROVIDE USEFUL BACKGROUND LAYERING INFORMATION.
INDUCED POLARIZATION (IP) AND RESISTIVITY CAN BE VERY USEFUL TOOLS IN MAPPING ENVIRONMENTAL FEATURES SUCH AS BURIED LANDFILLS, BUT THE SURVEY SPEEDS AND PSEUDOSECTION INTERPRETATIONS HAVE BEEN DRAWBACKS. NEW MULTI- CHANNEL RECEIVERS WITH COMPUTER-CONTROLLED MULTIPLEXERS NOW ALLOW EXTREMELY FAST DATA ACQUISITION, AND TWO- DIMENSIONAL SMOOTH-MODEL INVERSION (WITH TOPOGRAPHY) PROVIDES REALISTIC GEO-ELECTRIC CROSS SECTIONS. THE DATA SET BELOW CONSISTS OF THREE OVERLAPPING SPREADS OF DIPOLE-DIPOLE DATA, EACH CONSISTING OF 236 DATA POINTS. THE RECIPROCAL OF EACH DATA POINT WAS ALSO READ (WITH THE TRANSMITTER AND RECEIVER DIPOLES REVERSED), RESULTING IN A TOTAL OF 1,416 DATA POINTS, PROVIDING MEASUREMENTS AT N=0.5 TO N=6 AT 0.5N INCREMENTS. A FIELD CREW OF THREE WAS ABLE TO ACQUIRE THIS DATA IN ABOUT 4 HOURS.
A NEW ENHANCEMENT TO THE GDP-32 RECEIVER PERMITS IT TO GATHER NANOTEM DATA ON THREE CHANNELS SIMULTANEOUSLY. THIS MULTI-CHANNEL CAPABILITY WAS USED RECENTLY ON A RESEARCH PROJECT TO ACQUIRE ALL THREE COMPONENTS OF THE MAGNETIC FIELD (HX, HY, AND HZ) AT EACH STATION ON A GRID OVER AN ENVIRONMENTAL TEST PIT IN IDAHO. THE WORK WAS DONE AT THE IDAHO NATIONAL ENGINEERING LABORATORY (I.N.E.L.) AS PART OF THE ELECTROMAGNETIC INTEGRATED DEMONSTRATION (E.M.I.D.) PROJECT.
DETERMINING THE LOCATION OF OLD, POORLY DOCUMENTED BURIED LANDFILLS HAS BECOME A SIGNIFICANT CONCERN IN MANY PLACES WHERE DEVELOPMENT IS HINDERED. TODAY NEW METHODOLOGY PROVIDES A MEANS FOR THE EFFICIENT ACQUISITION OF INDUCED POLARIZATION AND RESISTIVITY DATA. CASE STUDIES OF SIX LANDFILLS VERIFIED THE ACCURACY OF THE TECHNIQUE AND THE ACQUISITION SPEED OF THE SYSTEM. AT ALL SITES, IP ANOMALIES (>3 MILLISECONDS) CORRESPOND TO SOLID WASTE VERIFIED BY DRILLING AND TRENCHING.
INDUCED POLARIZATION (IP) AND RESISTIVITY CAN BE VERY USEFUL TOOLS IN MAPPING ENVIRONMENTAL FEATURES SUCH AS BURIED LANDFILLS, BUT THE SURVEY SPEEDS AND PSEUDOSECTION INTERPRETATIONS HAVE BEEN DRAWBACKS. NEW MULTICHANNEL RECEIVERS WITH COMPUTER-CONTROLLED MULTIPLEXERS NOW ALLOW EXTREMELY FAST DATA ACQUISITION, AND TWO DIMENSIONAL SMOOTH-MODEL INVERSION (WITH TOPOGRAPHY) PROVIDES REALISTIC GEO-ELECTRIC CROSS SECTIONS THAT ALLOW FOR THE INTERPRETATION OF THE EDGES OF BURIED LANDFILLS, THICKNESS OF SOIL COVER, AND THICKNESS OF WASTE MATERIAL.
HISTORICAL RECORDS INDICATE THAT THE RIO NUEVO NORTH LANDFILL WAS PROBABLY COMPRISED OF MULTIPLE, IRREGULARLY SHAPED PITS RESULTING FROM CLAY, SAND, AND GRAVEL MINING. SEVERAL DEEP AND NUMEROUS SHALLOW PITS, EVIDENT FROM AERIAL PHOTOGRAPHS, HAVE BEEN FILLED WITH CONSTRUCTION DEBRIS, LANDSCAPING WASTE, AND MUNICIPAL SOLID WASTE. HAPHAZARD CLEANING OF THE AREA IN THE EARLY 1980'S LEFT POCKETS OF GARBAGE IN THE SUBSURFACE BELOW 17 FEET. THE RESULT OF THE EXCAVATION AND FILL ACTIVITY IS AN AREA THAT MAY OR MAY NOT CONTAIN SMALL POCKETS OF WASTE MATERIAL.
INDUCED POLARIZATION (IP) AND RESISTIVITY CAN BE VERY USEFUL TOOLS IN MAPPING ENVIRONMENTAL FEATURES SUCH AS BURIED LANDFILLS, BUT THE SURVEY SPEEDS AND PSEUDOSECTION INTERPRETATIONS HAVE BEEN DRAWBACKS. NEW MULTICHANNEL RECEIVERS WITH COMPUTER-CONTROLLED MULTIPLEXERS NOW ALLOW EXTREMELY FAST DATA ACQUISITION, AND TWO DIMENSIONAL SMOOTH-MODEL INVERSION (WITH TOPOGRAPHY) PROVIDES REALISTIC GEO-ELECTRIC CROSS SECTIONS.
THE SURVEY AREA IN THIS PROJECT HAS BEEN USED AS A LANDFILL SINCE 1953. PITS OR HOLES LEFT FROM LOCAL BRICK AND CLAY COMPANIES HAVE BEEN FILLED IN WITH MUNICIPAL GARBAGE. THE LOCATION AND EXTENT OF THESE PITS CAN ONLY BE ASSUMED FROM AERIAL PHOTOGRAPHS. IN THE EARLY 80'S SOME OF THE GARBAGE WAS REMOVED IN A RANDOM MANNER. AN IP AND RESISTIVITY SURVEY LINE WAS RUN OVER THE PROPERTY AS A TEST TO DETERMINE IF THE SMALL PITS OF GARBAGE COULD BE DELINEATED WITH THESE METHODS. TO KEEP EXPENSES TO A MINIMUM, ZONGE UTILIZED THE MX-30 WHICH IS A COMPUTER-CONTROLLED SWITCHING INTERFACE BETWEEN A RESISTIVITY TRANSMITTER, A MULTICHANNEL RECEIVER SUCH AS THE GDP-32, AND AN ARRAY OF UP TO 30 ELECTRODES. THE DATA SET BELOW CONSISTS OF THREE OVERLAPPING SPREADS OF DIPOLE-DIPOLE DATA, EACH CONSISTING OF 236 DATA POINTS. THE RECIPROCAL OF EACH DATA POINT WAS ALSO READ (WITH THE TRANSMITTER AND RECEIVER DIPOLES REVERSED), RESULTING IN A TOTAL OF 1,416 DATA POINTS, PROVIDING MEASUREMENTS AT N=0.5 TO N=6 AT 0.5N INCREMENTS. A FIELD CREW OF THREE WAS ABLE TO ACQUIRE THIS DATA IN ABOUT 4 HOURS.