31 



indicated that approximately 38,100 m 3 

 was placed at CS-2. 



Capping operations for both CS-1 and 

 CS-2 began in May 1983. Approximately 

 53,700 m 3 of New Haven silts was placed 

 at CS-1 (17-23 May 1983) and 42,000 m 3 

 of New Haven sand at CS-2 (30 May-3 

 June 1983). Based on these disposal 

 volume records, capping ratios of 1.6:1 

 and 1.1:1 were disposed at CS-1 and CS- 

 2, respectively (Table 2-4). Subsequent 

 surveys using a combination of acoustic 

 and photographic techniques indicated in- 

 place volume estimates of approximately 

 24,200 m 3 of Black Rock and 56,300 m 3 

 of New Haven sediment at CS-1, and 

 23,700 m 3 of Black Rock and 30,900 m 3 

 of New Haven material at CS-2, resulting 

 in slightly higher cap: mound ratios (2.3:1 

 and 1.3:1, respectively). 



The percent difference between the 

 disposal barge log records and volume 

 difference calculations for capping material 

 at CS-1 was negligible (a gain of 2.4%). 

 The difference between disposal barge and 

 volume difference calculations for mound 

 material at CS-1 and cap material at CS-2 

 was approximately 15%, and 23% for 

 mound material at CS-2. 



Considerable difficulties were 

 encountered during disposal operations at 

 CS-1: cap material was deposited 

 southwest of the intended disposal point, 

 resulting in uneven coverage of the Black 

 Rock Harbor material. The cap apex was 

 roughly 100 m southwest of the apex of 

 the contaminated material mound (Figure 

 2-9; Morton et al. 1984a, 1984b). There 



were areas of the eastern margin of CS-1 

 that did not receive a cap layer measurable 

 by bathymetric methods (>20 cm). 



Complete coverage was reported at CS- 

 2. Cap thicknesses ranged from 20 to 

 40 cm along the eastern margin to as much 

 as 1.4 m on the western border of CS-2 

 (Figure 2-10; Morton et al. 1984b). At 

 this time, DAMOS surveys routinely 

 incorporated photographic documentation 

 of sediment disturbance using Remote 

 Ecological Monitoring of the Seafloor 

 (REMOTS®) technology (discussed in 

 Section 3.2.2). Follow-up REMOTS® 

 surveys identified sections of the flanks of 

 CS-2 where the layer of reworked 

 sediment from bioturbation exceeded sand 

 cap thicknesses (Morton et al. 1984b). 



The Cap Sites demonstrate the 

 importance of precise navigation and point- 

 dumping for achievement of a successful 

 capping project. These operations differed 

 from the original capping disposal plans. 

 Taut- wired, moored buoys were to be used 

 during the disposal of contaminated 

 sediments in order to reduce the spread of 

 material requiring capping, and LORAN-C 

 was to be used for disposal of capping 

 material in order to cover a larger area 

 (Morton et al. 1984b). LORAN-C is a 

 navigational system which defines a 

 location based on distance from shore- 

 based transmitting stations with known 

 geographic locations. Problems developed 

 in the operation of the LORAN-C 

 receivers during the CS-2 capping 

 operation. Consequently, the remainder of 

 the capping operation at CS-2 was 

 accomplished using a taut-wired buoy as 



Sediment Capping of Subaqueous Dredged Material Disposal Mounds 



