A Glimpse into the Unique Challenges of Surveying

Surveying can be a uniquely complex profession. While a majority of the population may automatically imagine roadway surveyors, the reality is that much of surveying takes place out of sight. This may include hydrographic surveying, aerial surveying, or Global Positioning System or GPS using satellites. While Dewberry does offer many of these surveying services, here in the southeast and the Gulf specifically, the majority of our surveying work is focused on land and in water, sometimes both simultaneously.

geospatial

hydrographic

land


Other types of surveying include geospatial (top), hydrographic (middle), and land (bottom).

Taking on a Tall Task

Our survey team in Daphne, Alabama, took on a tall task earlier this year. As a subconsultant to a large construction engineering company, we performed layout and baseline control for an accelerated bridge construction project, which involved working on both land and in water. It was not an ordinary project, in fact, many surveyors never get the chance to be involved in such a unique undertaking.

The Usual Cast of Characters

The existing bridge was in an area of the Mobile River Delta that can only be accessed by water or rail. During our initial site visits, the train was operational. We were given access to a track manager whose job was to notify us 15 minutes prior to a train coming. We were required to vacate the tracks numerous times per day. The surrounding area was full of the usual cast of characters, wild hogs, bears, snakes, and a gator or two. You cannot simply run to the truck when being chased because you left it seven miles downriver.

Performing the Work

The first task was to establish a baseline on the centerline of the existing rails and bridge. The south end of the bridge section was actually at the point of curvature for a curved section of track heading south towards Mobile. We evaluated the best possible solution for getting the accuracy required, 0.015-feet vertical and 0.02-feet horizontal. After taking numerous locations along the track section, we were able to safely establish enough of a straight track segment to complete the task with reasonable confidence. Then we had to setup a template at the assembly point at a concrete yard back downriver. The final step was providing real time baseline locations during installation.

Getting it Done Over the Holidays

The elements under which the work was performed were challenging to say the least. The construction team had a 20-hour window in 40-degree weather (cold for south Alabama) to disassemble the old swing and install the new one. The survey team was focused and in sync with the contractor’s team. The work was performed starting on Wednesday night—Thanksgiving Eve—and finished Thanksgiving night.

Before


Before

After


After

Amidst these obstacles, our team persevered and completed the task on time and with quality. I’m incredibly proud of the surveyors involved and the way they joined together to complete a lofty—and arguably somewhat dangerous—task.

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