PROJECT DESCRIPTION: SEAS was contracted by the USACE Pittsburgh District to perform a high accuracy dam deformation surveys of ten Lock(s) and dams along the Allegheny, Monongahela, and Ohio Rivers. SEAS and SEAS’ team member TerraSurv, an expert in Dam Deformation & Geodetic surveying as well as local to the project area, performed all of the work on this project. This allowed for fewer mobilizations. The survey effort consisted of the following tasks:
✓ Calibration of Equipment: EDMs were calibrated at the Culver Davies NGS EDM calibration baseline. Digital Levels were initially calibrated by the manufacturer and daily peg tests were performed and recorded.
✓ Recover and surveyed select existing control monuments. A geodetic quality static GNSS network was performed to establish horizontal coordinates on each site’s reference network. Monuments were selected based on location at the project sites to give the best geometry for the network adjustment.
✓ Performed geodetic quality vertical leveling throughout the project sites tying all base control monuments together. Trimble DiNi 12 digital level and invar rods were used.
✓ Survey of all alignment pins using 1” total stations. Each pin was observed in at least four sets of direct and reverse sighting, and from at least two instrument setups. Wherever possible Seco Mini stakeout prisms with a height of 0.1 meters were used to locate the pins. This helps ensure that centering errors over the points is minimized.
✓ Survey report in compliance with the format defined in Chapter 12 of EM 1110-2-1009, including overall positional accuracy statements for each data set (alignment, settlement, gauges, etc.) equipment calibrations, QC process and summary, daily checks, positional accuracy statements for all data sets collected, a statement indicating if the least squares adjustment passed or failed the Chi-Squared test at a 95% confidence level and the value of the reference variance, dates/times of field surveys, and list of control used.
SCHEDULE AND PROJECT CHALLENGES: The Notice to Proceed was given September 21, 2019 with a delivery date of January 19, 2020.
CONTROL RECOVERY AND DAM SURVEY: SEAS and Terrasurv used Trimble R10 and R12 GNSS receivers to survey the existing primary control for the project sites. Receivers were started in the morning and allowed to run continuously throughout the work day. The alignment pins were surveyed using 1” Trimble total stations. During the alignment pin survey, any primary control that was visible from the setup were tied in as well.
DATA PROCESSING: GNSS, total station and digital level data was processed using Trimble Business Center. Star*Net was used to perform all least squares adjustments. A detailed report containing all of the horizontal and vertical coordinate values of the surveyed features and a comparison of those values to previous observations was prepared and submitted.