International Dredging Review

International Dredging Review

Chris Ransome and Associates Inc. (CRA) has added a new 26-foot survey boat to its fleet. The boat built at Scully’s Metal Fabrication of Morgan City Louisiana is all-aluminum construction with a nine-foot cabin console and two 115-horsepower outboard engines. The boat will be equipped for hydrographic surveys magnetometer surveys sidescan sub-bottom profiling and sediment sampling.


The boat is equipped with two transducer wells for single beam low (left) and high (right) frequency transducers.

CRA is headquartered in Houston Texas and does its primary work in ports on the Texas coast with other projects throughout the U.S.

The cabin of the new boat was installed as far forward as possible leaving a large back deck with ample space for ROV fish cables sampling equipment and other equipment. Ransome invested in a Universal Sonar Mount (USM) which he calls “the Cadillac of sonar mounts” for an over-the-side permanent multibeam transducer installation. (See related article in this issue pg. 18) The single-beam high and low-frequency transducers are mounted through the hull in two wells. Another feature is a davit on back for handling equipment such as velocimeters or grabs for sediment sampling which can work from either side of the boat.

The boat was delivered in late March and CRA engineers began installing the survey equipment which will include single- and multibeam sounders and capability for sidescan magnetometer and sub-bottom profiling. A previously-purchased Lidar system is being disassembled and the IMU (inertial measurement unit) will provide orientation information while the Lidar (radar) head will provide above-water information where needed.

Ransome explained that this application has been developing in the past few years as the market for extending terrain models up and out of the water matures. Because rock placement is so expensive and repair of rock structures involves precise measurement the extremely accurate data provided by mapping the underwater portion of a wall coupled with a Lidar image of the above-water portion is becoming cost effective particularly in open-sea areas where wave action makes it too dangerous to land a person to map the above-water section. Other companies such as Arc Survey & Mapping in Jacksonville Florida have had this capability for several years and Ransome sees the market as justifying investing in it now.

CRA’s major work is doing depth surveys sediment sampling and sidescan at ships’ berths in ports on the Texas coast – in the Port of Houston and north from Orange and Beaumont near the Louisiana border to Corpus Christi 130 miles north of the Mexican border. The new boat joins CRA’s four other boats partially replacing a 24-foot fiberglass boat which Ransome will keep in reserve for high-volume use such as in the aftermath of a hurricane.

Equipment: New CRA Survey Boat
• Multiple topside processors all powered by a built-in Windows 7 Workstation fed by dual 1000-Watt pure sine wave inverters connected to the outboard engine alternators
• Odom ES3 multibeam system
• R2Sonic 2020/2024 multibeam system
• Two built-in transducer wells for single beam low and high frequency transducers
• USM (Universal Sonar Mount) for multibeam depth sounding and imaging sonar transducers
• Trimble Navigation model SPS 651 RTK GPS heading/positioning system
• Odom Digibar Pro and Digibar “Pro V” velocimeters
• Novatel IMU motion sensor
• Twin mounts for single 300-pound-capacity lifting davit
• Twin Yamaha 115 hp outboard motors.