• Equipment to place capping materials varies depending on project requirements and site conditions
• Equipment mobilization costs are minimized by accurately tracking mobilization, demobilization, and expected utilization. This allows for cost-effective mobilization of equipment from the nearest equipment yard or project location

Sevenson typically uses a hydraulic excavator stationed on a modular barge for placing sand and armor stone material. Production rates for mechanically placing armor material vary depending on the material’s availability and physical dimensions.

Sevenson owns and operates custom-built and patented slurry spreader systems for hydraulically placing cap material.

Materials are fed on a dry weight basis to the slurry hopper and mixed with makeup water. A dredge pump is used to convey the slurry. The hopper, screening, and slurry system are typically placed on the shoreline for easy truck pickup and delivery. The slurry system can also be staged on a barge.

A diffuser/spreader barge is attached to the slurry system by a high-density polyethylene (HDPE) pipe. The barge has a discharge apparatus fabricated on the deck, which functions to dissipate the energy in the capping material slurry delivered to the placement barge. Cap material enters the water in a controlled fashion. The barge is equipped with a cable winch system and anchors to facilitate movement.

The barge’s controls are integrated with RTK DGPS and DREDGEPACK® software. Output from the software is used to “drive” the barge along a preprogramed cap lane. The production rate of material placement is based on the pumping distance between the site and the shoreline, as well as the grain size of material.

Sevenson consistently demonstrates the ability to place cap lift thickness ranging from 1 inch to 18 inches per pass with the barge.