1.0 INTRODUCTION 



1.1 The Boston Harbor Navigation and Improvement Project 



The Boston Harbor Navigation and Improvement Project (BHNIP) involves 

 deepening of the main ship channel (in the Inner Confluence and the mouth of the 

 Reserved Channel), and three tributary channels (Mystic River, Chelsea Creek, and 

 Reserved Channel) in Boston Harbor (Figure 1-1). In addition to the channels, several 

 terminals and berth areas will also be dredged, for a total of 2. 1 million yd^ of material 

 (Table 1-1). All of the channels will be deepened to -40 ft MLLW, except for Chelsea 

 Channel, which will be dredged to -38 ft MLLW. BHNIP is a joint project between the 

 US Army Corps of Engineers, New England District (NAE) and the local sponsor, the 

 Massachusetts Port Authority (Massport). The first phase of the project, Conley Terminal, 

 was conducted in the summer of 1997. 



Following extensive environmental review, the disposal options for both suitable 

 and unsuitable material were described in the Final Environmental Impact 

 Statement/Report (FEIS/R; NAE and Massport 1995). The plan included disposing the 

 unsuitable material in approximately 50 in-channel confined aquatic disposal (CAD) cells, 

 approximately 1.3 million yds^ of clean material will be dredged to create the cells 

 averaging 20 feet deep, dredged below the federal navigation channels in the Mystic River, 

 Chelsea River, and the Inner Confluence (Figure 1-2; NAE and Massport 1995; Demos 

 1997). Because of concerns over the environmental impact of such a large-scale project, 

 the state of Massachusetts negotiated for intensive environmental monitoring under the 

 auspices of the CWA 401 Water Quality Certificate (WQC; Babb-Brott 1997). The WQC, 

 granted by the Massachusetts Department of Environmental Protection, included the 

 stipulation that the unsuitable material must be dredged using an environmental (closed) 

 clamshell bucket, and capped by at least 3 ft of clean, granular material. One of the goals 

 of the WQC was to monitor the short and long-term integrity of the capped CAD cells, and 

 included review of all monitoring data by a state-sponsored Independent Observer (10) for 

 the Coastal Zone Management Agency (CZM; ENSR, Acton, MA was selected as 10). 

 Survey results presented in this paper are only part of the extensive monitoring data 

 collected for the Conley Terminal project (ENSR 1997a,b; Section 1.2). 



Concerns were raised by the BHNIP Technical Advisory Committee (TAC) prior to 

 capping that the density difference between the fine-gramed maintenance sediment and the 

 coarse-grained sand cap would result m displacement of the cap, and that cap coverage 

 would be difficult to verify using bathymetric methods alone (ENSR 1997b). Verification 

 monitoring of the cell, in addition to the required monitoring by the WQC, was initiated in 

 the summer-fall of 1997. The survey data presented in this report were collected in order 

 to address these TAC concerns (Section 1.3). 



MONITORING RESULTS FROM THE FIRST BHNIP CONFINED AQUATIC DISPOSAL CELL 



