MONITORING CRUISE AT THE 



SACO BAY DISPOSAL SITE 



HAY 1990 



1.0 INTRODUCTION 



The objectives of the present survey were to characterize 

 dredged materials deposited at the Saco Bay Disposal Site. This 

 material came from dredging activities for two projects at the 

 nearby Biddeford Pool. The Saco Bay Disposal Site was approved for 

 use by only these projects and was located 1.3 nm east of Ferry 

 Beach, Maine, and 1.7 nm northeast of the Saco River inlet (Figure 

 1-1). This site was centered at 70°19.300'W, 43°28.500 I N, and 

 consisted of a circular area 500 yards in diameter. From 9 January 

 to 11 May 1989, approximately 34,800 cubic meters of dredged 

 sediment were disposed at the site. A previously deployed disposal 

 buoy was removed on 7 October 1989, 8 months prior to the present 

 survey . 



The areal extent and thickness of dredged material were 

 measured using both acoustic techniques and REMOTS® sediment 

 photographs. A precision bathymetric survey was conducted at the 

 site on 18 May 1990, and a REMOTS® survey completed the following 

 day, on 19 May 1990. In addition, REMOTS® pictures were used to 

 map benthic disturbance gradients and monitor the process of 

 benthic recolonization on and adjacent to the disposal area. Prior 

 to this work, no previous bathymetric or REMOTS® surveys had been 

 conducted at this site, and therefore no pre-disposal baseline data 

 existed for the area. A capping model currently under development 

 had predicted the formation of a small mound of dredged material, 

 approximately 2 m high and 500 m in diameter. Because a year had 

 passed since the last disposal event, the benthic community 

 successional stage on this mound was predicted to be primarily 

 Stage II going to Stage III recolonization. 



2 . METHODS 



2.1 Bathymetry and Navigation 



Precision bathymetry and navigation methods were used to 

 delineate the areal extent and thickness of dredged materials at 

 the Saco Bay Disposal Site. The SAIC Integrated Navigation and 

 Data Acquisition System (INDAS) supplied the precision navigation 

 required for the bathymetric survey. This system used a Hewlett- 

 Packard 9920 series computer to provide real-time navigation and to 

 collect position, depth, and time data for subsequent analysis. 

 The ship's position was determined to an accuracy of ±3 m from 

 ranges provided by a Del Norte Trisponder® system. Shore stations 

 were established at sites in Maine located along Old Orchard Beach 



