No Holds Barred—with GPS
The Bureau looked to its environmental consultant, The Louis Berger Group Inc. (LBG) of Providence, R.I., for help. LBG in turn hired B.P. Barber & Associates Inc. (BPB) of Columbia, S.C., to provide the complete boundary and topographic survey for the three sites.
It didn’t take BPB more than a quick glance at the marshlands, overcut wooded areas and generally unfavorable living conditions to realize that these surveys would require more than routine point-and-shoot methods.
“At each site, we needed to map over 200 soil borings spread throughout the more than 700 acres,” recalls Henry Dingle, senior survey manager for BPB. “Add to this, we’d need to remove heavy brush, negotiate around murky swamplands and pass through heavily wooded forests. We knew immediately that we couldn’t traverse on foot by conventional survey methods to perform these surveys due to the Bureau’s time constraints.”
BPB surveyors looked for some speedy help of the four-wheeled variety. They borrowed a Honda ATV four-wheeler from their inspection group, added some Leica Geosystems (Norcross, Ga.) GPS System 530 equipment provided by Earl Dudley Associates Inc. of Charlotte, N.C., and created a highly efficient, mobile survey solution. In the end, this innovative combination helped BPB save hundreds of labor hours, established a sound method of data gathering and saved the client thousands of dollars.
GPS-based Aerial ReinforcementsAt project go-ahead, BPB relied on aerial photography shot by GRW Aerial Surveys of Lexington, Ken., to develop a strategic plan that accounted for the geographically disparate locations of all three sites. One site was located near the city of Bennettsville in Marlboro County. The second and third sites were located some 100 miles south in Williamsburg County near the cities of Salters and Greelyville.
Prior to the aerial photographs, BPB used GPS to set control panels. With the closest USGS control monuments located 10 miles away in Kingstree, GPS control for the base station needed to be established near the property. Surveyors established two South Carolina NAD 83 control points for the base station on either side of each piece of property using the Leica System 530 in rapid static GPS mode and Leica Ski-Pro Software for post processing. Once the aerial panels and survey control points for the property survey were placed, the survey team positioned these points on the ground using real-time kinematic (RTK) GPS with the base station on one of the two GPS control points. The base station was then moved to the other GPS control point and the process repeated to provide a check for the location and elevation. Once this information was checked and analyzed, the soil borings were then located using the same methods.
Submeter locations of the wetlands were provided by LBG and incorporated into the drawings. Accuracy for control and soil borings was ± 1 cm horizontal and ± 2 cm vertical. The surveyors also researched county records, highway department plans, and files and maps from state and county agencies prior to surveying each property.
Overhauling a Sport MachineReady to begin the detailed topographic survey, the BPB survey knew they needed mobility. The crew borrowed a Honda ATV from BPB’s Inspection Division. The survey team drove the ATV onto the survey van trailer and drove to the Greelyville site in Williamsburg County. Then they attached the Leica GPS pole to the front with simple brackets from a local hardware store. Next they installed the receiver on the handlebars.
“Over the course of several days, one surveyor would move into the field along a pre-determined path, gathering horizontal and vertical position data,” Dingle says. “Keep in mind that over 200 soil boring positions had to be located during this process.”
Added to this, he says, both the Greelyville and Salters sites included the assessment of numerous interior and adjoining parcels of land, along with many easements and rights of way.
The BPB team worked 10-12 hours per day, depending on satellite availability. At the end of the day, the field data from the GPS was downloaded to a laptop computer in a nearby hotel room and transmitted over the Internet to BPB’s headquarters in Columbia allowing design technicians to work in near real-time as data was gathered. The ability to speedily locate the soil borings allowed the aerial photographer to use the elevations as a check for his map contours.
At the Greelyville location, the survey addressed right of way road widening and bridge construction on Highway 52. No monumentation existed, and BPB worked with the South Carolina Department of Transportation personnel to establish control points and rights of way. Nearly a mile of highwater line along the Santee River Swamp was included in the survey.
The Bennettsville site proved just as complex. The site had not been surveyed since 1946, and no records were available on file. BPB was able to gather plats, deeds and highway plans of the surrounding parcels.
Four-Wheeled SuccessBy combining the speed of the ATV, the efficiency of the GPS, and the real-time data transfer capabilities of the Internet, BPB completed the survey of all three sites six weeks faster than would have been otherwise possible. This saved the firm 480 labor hours and saved the client several thousand dollars. It in turn allowed survey crews to be available to other clients sooner and allowed LBG to begin design work earlier than would have otherwise been possible.
In the end, the Bureau selected the Salters site and the Bennettsville site for the prisons. Each of these communities will benefit economically through the creation of new jobs and increased revenue. The Salters site will be home to a $130 million medium-security prison and will bring about 400 jobs to the area. The Bennettsville site is expected to be similar size and create as many jobs.