MONITORING OBJECTIVES

Technical Note DOER-I1

July 1999 (Revised April 2000)

office or alternative DGPS is required. Printouts of screen data reflecting the advance of the dredge

and the arc of the swing within the channel are to be generated on an automated basis such that the

inspector receives a copy for every 2 hr of dredging activities. As described above, the contractor's

dredges are required to be equipped with recording vacuum and pressure gauges during operations.

Legible charts of these recordings are furnished to the Contracting Officer for each day's operation

on a daily basis.

These dredges are also to be equipped with a production meter system consisting of a nuclear density

gauge, a mass-flow system transmitter, an ultrasonic flowmeter with two acoustic transducers, a

crossed-pointer indicator display, and a chart recorder. The crossed-pointer indicator display and

chart-recorder readout format are in cubic yards per hour and feet per second (slurry velocity).

Personnel supervising the use of the nuclear-density meter are required to hold and maintain,

throughout the contract, a current Nuclear Regulatory Commission (NRC) license. The licensed

personnel are to maintain the required NRC records and perform periodic wipe tests to detect

radiation and ensure that the system is in compliance with NRC safety standards. As additional

safety precautions, the radiation source has to be encased in a protective housing to prevent

accidental exposure to personnel, and a turnbuckle and pipe guard are also to be installed as a

secondary securing device to provide protection from bumping. The system is to be calibrated and

placed into service by a qualified technician prior to start of work. The detector is to be located as

close to the pump discharge as possible, and the crossed-pointer indicator is located in the lever

room. This equipment is not to be affected by outside interference. These recordings are furnished

to the contracting officer for each day's operation on a daily basis in the following data string: date,

time (military), northing, easting, vacuum and discharge pressure, pump rpm's, slurry velocity,

slurry density, and integrated instantaneous production.

San Francisco District: The San Francisco District had required contractors to provide smoke

charts of vacuum and pressure readings in the past, but around 1985, the required data were changed

to pipeline slurry velocities near the dredge pump discharge and at the end of the pipeline (presented

in digital form). Several years after this modification, the required digital data were changed to

include date, time, slurry velocity, cutterhead horizontal positioning (2-D), number of DGPS

satellites available, Horizontal Dilution of Precision (HDOP, a measurement of the accuracy in 2-D

positioning), and vessel heading.

MONITORING OBJECTIVES: QM, defined as the control and assurance activities instituted to

achieve the quality established by the contract specifications, is the reason for monitoring hydraulic

pipeline dredges. Because the use of time-measure unit price (rental) contracts (as opposed to

volume-measure contracts) reapportions more risk to the Government, additional monitoring of

dredging parameters becomes more important. For a rental contract, the use of correct vacuum and

discharge pressure recordings provides "an accurate report of shutdowns and are generally irrefu-

table if a difference of opinion arises. They are a necessity, not a luxury" (Huston 1970). In addition

to QM, the data from monitoring dredging parameters like these (vacuum and discharge pressure)

and other types described in this TN are used by Corps personnel for planning, estimating, and

settling contract disputes.

SUMMARY: Standard methods for pipeline dredge monitoring provide many benefits. They

reduce monitoring costs because contractors do not need to develop capabilities to meet differing