3D Resistivity Survey For Sinkhole/Underground Void Locating

Due to complexity and often 3D natures of subsurface conditions, 2-dimensional direct current electrical resistivity surveys (resistivity profiling) often can not provide the best results and the data interpretation is difficult. In the other hand, a 3D resistivity survey provides a much better prospective and the results more accurately reflect the subsurface conditions. Enviroprobe recently conducted a 3D resistivity survey in northwest New Jersey to identify potential sinkholes for a residential property. There had been sinkhole openings in and around the properties. Through the survey, a number of potential sinkholes were identified.

Electrical Resistivity Imaging In Bermuda

In 2015, Enviroprobe conducted an electrical resistivity imaging (ERI) survey to locate underground caves in Bermuda. Along with the beauty and myth of Bermuda came one of the most difficult surveys. The majority of the survey areas were in jungles with tough terrains. Paths had to be cleared for the survey lines and they were kept narrow to minimize the impact to vegetation. In humid weather, carrying heavy equipment while watching your footing was a challenge to the survey crew, both physically and mentally. Despite the difficult survey conditions, Enviroprobe's survey crew spent a month completing about 100 ERI lines with miles of linear length in total without any major injuries. One of

Electrical resistivity imaging in Bermuda

In 2015, Enviroprobe conducted an electrical resistivity imaging (ERI) survey to locate underground caves in Bermuda. Along with the beauty and myth of Bermuda came one of the most difficult surveys. The majority of the survey areas were in jungles with tough terrains. Paths had to be cleared for the survey lines and they were kept narrow to minimize the impact to vegetation. In humid weather, carrying heavy equipment while watching your footing was a challenge to the survey crew, both physically and mentally. Despite the difficult survey conditions, Enviroprobe's survey crew spent a month completing about 100 ERI lines with miles of linear length in total without any major injuries. One of

Underground Utility Locating in Gas Stations

Prior to drilling, digging, trenching, and excavating, it is essential to know where underground utility lines are located. It’s particularly important for gas stations. Unlike residential house and office building properties, gas stations usually contain extra underground utilities including those for gasoline/diesel tanks and pumping systems. Besides the usual utilities including electrical power, communication, sewer, water and natural gas lines, there are other important lines such as fuel/product lines, ventilation lines and electrical conduits for the gasoline/diesel fueling system. There could also be other lines related to car shop and car wash facilities which are often found in gas

7 Site Condition Considerations For Geophysical Services

Before you sign a contract with a geophyscial service provider, there are some general considerations for the site conditions you need to discuss with them for cost-effective and successful geophysical surveys. Is the site generally accessible through vehicles or ATVs? Geophysical equipment for some tasks could be heavy and vehicle access could speed up the data acquisition process significantly. Sometimes the data acquisition design/logistics could be totally different depending on the easiness of vehicle access. Is the site generally walkable? Is it heavily vegetated? Dense vegetation can require additional costs and/or permissions to clear survey areas. What’s the ground surface material?

An Unexpected Underground Storage Tank Found During Utility Markout

Enviroprobe conducted an underground utility locating survey at a gas station in Morristown, NJ. During the process of searching for underground utilities, an anomaly showed up in the ground penetrating radar data close to the pump island. The experienced Enviroprobe geophysicist immediately realized this could be an orphaned underground storage tank. Further investigation utilizing metal detectors confirmed the finding. The finding was notified to the client, a reputable environmental consulting company, so further appropriate actions could be taken.

Underground Void Locating Using Seismic Method - Multichannel Analysis of Surface Waves (MASW)

Enviroprobe recently conducted an underground void locating survey at a traveling center in New Jersey. MASW instead of electrical resistivity tomography (ERT) was used due to reinforced concrete in the survey areas. MASW is one of the seismic survey methods evaluating the elastic condition of subsurface materials. MASW measures seismic surface waves generated from a seismic source, analyzes the propagation velocities of those surface waves, and then finally deduces shear-wave velocity (Vs) variations of subsurface materials. For each survey area, survey lines were laid out in a grid pattern. A 2 dimensional (2D) MASW survey was conducted along each line. A sledge hammer was used to strike a

Ground Penetrating Radar To Estimate Subsurface Layer Thickness Such As Concrete And Soil Cover

When there is a good penetration depth for ground penetrating radar (GPR), GPR can be used to estimate thicknesses of subsurface layers. However, caution has been taken as such estimation may not be accurate without references or ground truth information. As EM waves from GPR travel down and bounce back from a subsurface interface between two layers, the travel time can be determined. In order to calculate the depth to the interface, the wave travel velocity needs to be known. Although there are indirect ways to estimate the wave velocity and depths such as using the common midpoint (CMP) method, the most direct and accurate way is to get the ground truth. The ground truth collected at one o

Soil Resistivity Testing Utilizing Wenner 4-Pin Method

Enviroprobe recently conducted soil resistivity testing with Wenner Array 4-point Method at several sites in central and north New Jersey. This method is the most commonly used test method to measure the resistivity of soil for electrical grounding design. The Wenner array consists of a line of four equally spaced electrodes. Current is injected through the outer electrodes and potential is measured between the inner electrodes. The testing utilized an Advanced Geoscience Inc. (AGI) SuperSting R8 resistivity system and was done in a perpendicular pair at each testing location using the standard traverse setup with the maximum “a” spacing as 100'. For accurate results, testing locations shoul

How Accurate Is Underground Utility Locating?

One question we get frequently from our clients is: how accurate is underground utility locating? The alternate question is: what's the safe distance to drill or excavate away from marked underground utilities? Although there is no precise answer to this question, there are still some good practices to follow. Some states require you keep certain distance away from marked underground utilities if powered tools are to be used. For example, in new jersey, you can only hand dig within two feet of a line marked by utility companies. In general, two feet is the minimal distance. but most companies doing drilling or excavation routinely have formed their own policies and 3, 5, or even 10 feet dist

GPR Survey With Snow Or Ice Cover On The Ground

"The ground is snow covered, is it OK for the GPR survey?" This is a very common question from our clients. Ground penetrating radar (GPR) actually works well through snow or ice. Below is a GPR profile showing an underground storage tank (UST) with ground covered by about 4 to 6" of snow. The located UST was marked on-site as in the picture to the right. Although snow or ice on the ground surface wouldn't block GPR signals, it's not a favorable working condition for some types of GPR surveys, such as those searching for underground utilities. A GPR designed for underground utility locating typically has a ground-coupled antenna, meaning it works the best when it's close to the ground surfac

GPR Scanning For Concrete Footing

Ground penetrating radar (GPR) has many applications. One of its applications in engineering is to delineate lateral extents of footings for bridges, buildings and other structures. Design and as-built plans are not always available when needed and a GPR survey could provide valuable information about the footings in a non-destructive and efficient way. The GPR profile below shows a concrete footing with reinforcement. The top of the footing was about 3' underneath a concrete floor. The GPR profile was collected next to a steel supporting structure.

Watch Out The Ends Of Fiberglass USTs For Drilling

It's a very common practice for environmental consultants to get soil samples around underground storage tanks (USTs). The selection of drilling locations depends on a lot of factors and sometimes it's preferable that they are located as close as possible to USTs without risking damaging them. Ground penetrating radar (GPR) is a great tool to use to delineate UST scopes due to its very high lateral resolutions. GPR can be used to delineate scopes of USTs made of steel or fiberglass. Even if a concrete slab is constructed on the ground surface for the protection of UST, it's a safe practice to conduct a GPR survey to make sure the UST does not extend beyond the scope of the concrete slab. We

Electromagnetic (EM) Surveys – Data Contour Maps or Not?

Traditionally, results of electromagnetic surveys utilizing EM instruments such as Geonics EM31 or EM61 are usually presented in contour maps. A picture is worth a thousand words -- these data contour maps, especially when drawn in colors, can be very powerful presentation materials showing details of investigation results. However, when the budget of a project is limited, it’s possible to lower the survey cost, but still achieve the same investigation goal without contour maps as the final output. This can be done with the reconnaissance survey mode without setting up GPS or a manual grid. By doing so, both field time and office time are saved, hence the cost is lower. So, should you set up

Environmental and Engineering Geophysical Services

Over the years, the geophysical service provided by Enviroprobe for environmental and engineering communnities has grown tremendously. Our geophysicists and geophysical technicians employ varieties of geophysical methods including but limited to: ground penetrating radar (GPR), precision locating (for underground utility lines), borehole geophysical logging, DC electrical resistivity, sub bottom profiling, seismic, and EM mapping. Our services include but not limited to: Locating underground metallic and nonmetallic pipes and utility cables Delineating underground storage tanks (metallic and nonmetallic) Mapping rebar in concrete structure Mapping landfill boundaries Delineating pits and tre

A sonic drilling rig has joined our drilling equipment family

Enviroprobe recently purchased a Dando SDC375 Roto-Sonic drilling rig equipped with the Sonicor 50K drill head. It is a multipurpose sonic drilling rig capable of continuously collecting large diameter undisturbed samples at much higher rates than conventional drilling methods. Its compact and powerful design, featuring the industry leading Sonicor 50K rotary head, offers great flexibility for a range of drilling applications including mineral, water, geotechnical and GSHP. The sonic drilling rig is a powerful machine with a small foot print allowing it to operate in area of limited space. It is outstanding in its ability to provide continuous, undisturbed core samples through any geological

3rd Annual Southwest Florida Brownfield Symposium

We are proud to announce that Enviroprobe Service, Inc. will be a sponsor of 3rd Annual Southwest Florida Brownfield Symposium. As a company providing drilling and geophysical services for more than 20 years, being a sponsor of the symposium is our continuing effect to support environmental communities. The symposium is to be held on March 20, 2015 in Fort Myers, FL. Its goal is to assist you in putting your Brownfield puzzle together as you thrive towards economic enrichment through redevelopment. There will be a diverse group of volunteer speakers with a wide range of expertise ready to provide you the latest information. The program will include several panel discussions as well as presen

Seismic Refraction Survey To Delineate Bedrock Topography

As part of a project for tracking down overflowed oil, Enviroprobe conducted a geophysical survey to delineate the bedrock topography around a tank field. The seismic refraction was the primary investigation method and an EM31 survey was also conducted as a quick complementary method. The 2D seismic refraction survey was conducted along parallel lines and the results were interpolated for the bedrock topography. One of the important discoveries was that the elevations of the bedrock top around perimeters of the tank field were low, although the tank field itself appeared to be at the top of a hill. The EM31 data appeared to agree with the seismic survey results although it was severely affec

Misconception of “Concrete GPR”

We’re frequenctly requested by clients to bring “concrete GPR” to sites for searching something underground. However, sometimes these requests were based on the misconception of concrete GPR. Just because the medium is concrete it does not mean that the "concrete GPR” is the best approach. The main difference between a concrete GPR and a regular GPR, such as those for underground utility locating and underground storage tank locating, is the antenna frequency. The antenna frequency of a concrete GPR system is usually in the range of GHz, while those of regular GPRs are typically between 250MHz and 900MHz. Higher frequency means shallower penetration depth but better resolution. If you look f

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©2018 Enviroprobe Service, Inc. : 81 Marter Avenue : Mt. Laurel, NJ 08054 : 856.858.8584