Status of Current Hopper and Bin Measurement Technologies

ERDC TN-DOER-T6

September 2004

Status of Current Hopper and

Bin Measurement Technologies

PURPOSE: Research to improve dredging contract management, economics (cost

optimization), and contaminated sediments management (document dredging and placement

locations) is currently being conducted by the Innovative Technologies (IT) Focus Area of the

U.S. Army Corps of Engineers (USACE) Dredging Operations and Environmental Research

(DOER) Program. A common element in these research efforts is the ability to measure dredge

production with the Silent Inspector (SI). This technical note (TN) describes currently used

hopper and bin production measurement methods and discusses their respective capabilities and

limitations. In this TN, the term hopper is defined as the holding space for dredged material in a

hopper dredge, and the term bin identifies the holding space of a barge or scow. Subsequent

DOER technical notes will refer back to this document as a basis for defining system

requirements in the development of improved hopper and bin measurement technologies.

BACKGROUND: The DOER Innovative Technologies Focus Area is currently conducting

research to develop and demonstrate robust hopper and bin instrumentation and data analysis

techniques to quantify dredged material for assessing dredge performance. Corps dredging

operations are in transition to automated monitoring of contract dredge operation (Rosati 1998,

Welp and Rosati 2000, Rosati and Prickett 2001). The routine use of Silent Inspector (SI) data

has focused attention on the accuracy of production measurement. Analysis of hopper dredge

total production data errors clearly indicates that the largest uncertainty is measurement of

dredged material in the hopper (Rullens 1993, Rokosch 1989, Scott 2000). The U.S. Army

Engineer Research and Development Center (ERDC) worked with USACE Districts and

dredging contractors to investigate the performance of existing hopper and bin measurement

systems. Results from this investigation are being used to define a set of system requirements

for improving hopper and bin measurement.

In addition to hydrographic surveying before and after dredging, there are two ways of

determining hopper dredge production: measurement in the pipeline and measurement in "means

of conveyance" (Rullens 1993). Production is based on the quantity of solids transported by the

dredge. Production determined by hydrographic survey provides performance quantities relative

to the sediment's in situ mass characteristics (i.e., bulk density, etc.). It is desirable to relate

quantities of solids measured in the pipeline and means of conveyance to the "in situ solids

quantity," but sediment bulking influences these relationships.

A bulking factor is the ratio of the volume occupied by a given mass of dredged material in

either a hopper or bin immediately after deposition by a dredging process, to the volume

occupied by the same mass of sediment in situ. Sediment material, mass, and behavior

characteristics, and different types of dredges and dredging techniques affect bulking. Granular

materials may increase or decrease volume, depending on the initial density state (loose or