The location of the disposal buoy at the New London 

 Disposal Site has not changed since the July 1986 REMOTS survey. 

 That survey focused primarily on the NL-85 mound formed at the 

 buoy. In order to delineate the extent of the dredged material 

 deposited during the past year's disposal activities and to 

 document any changes in bottom conditions, the results of the 

 present survey have been compared with the results of the July 

 1986 survey. 



2 . 3 Dissolved Oxygen 



The depth gradient in dissolved oxygen was characterized 

 at REMOTS stations using a Rexnord Instruments Model 66 dissolved 

 oxygen probe interfaced to an STD probe (Applied Microsystems, 

 Ltd. Model STD-12) . The STD-12 , used to measure salinity, 

 temperature, and pressure (depth) , was mounted vertically on the 

 REMOTS camera frame such that its sensors were located 

 approximately 42 cm from the camera base. The attached Rexnord 

 probe was mounted horizontally on the camera base frame such that 

 its membrane was located between 6 to 9 cm above the sediment 

 surface during deployment, depending on how deep the camera frame 

 settled into the bottom. In this configuration, vertical 

 hydrographic profiles were obtained during REMOTS image 

 acquisition. 



The STD-12 is capable of sampling up to 8 scans per 

 second and can store up to 7648 scans in 56k of internal RAM. 

 Commands are sent to and data read from the instrument with a 

 Compaq Portable II microcomputer via an RS-232 interface. Prior 

 to commencing the REMOTS survey, the STD-12 was set to internally 

 log data at 1 second intervals. The data were downloaded to the 

 microcomputer during REMOTS film changes and stored on floppy 

 disks for later analysis. 



The Rexnord Model 66 probe is a polarographic oxygen 

 electrode (platinum-lead galvanic couple with a potassium-iodide 

 electrolyte) . The probe was covered with a 1 mm thick diffusion 

 membrane. Calibration of the Rexnord Model 66 was performed at 

 the SAIC Oceanographic Service Center by the standard method of 

 comparison with Winkler titration (Strickland and Parsons, 1972) . 

 Calibration must be done whenever the membrane and electrolyte are 

 changed. The calibration of the conductivity, temperature, and 

 pressure sensors on the STD-12 was performed by the manufacturer. 

 Salinity was calculated from conductivity data based on procedures 

 described by Perkin and Lewis (1980) . 



2.4 Sediment Sampling and Analysis 



Triplicate sediment samples were collected with a 0.1 

 m 2 Smith-Mclntyre grab sampler at six stations located across 

 the disposal site northwest to southeast (the direction of the 



