132 



regarding this experiment were summarized into one final report 16 . Later, in 

 1987, an updated report was submitted to the NYD 17 . 



i. Capping mav work only under certain conditions 



The cap appeared to be successfully placed at the EMD and it was 

 still intact within 16 months. Cap erosion was considered minor, although the 

 researchers did document an increase of muds on the cap. They attributed this to 

 a combination of erosion of fine sand plus deposition of fines transported onto 

 the cap from peripheral locations. The cap was determined to have a lifetime of 

 20 years under "normal meteorological conditions. " 



However, the researchers were careful to caution that unusual events, such 

 as hurricanes, could generate energies more than an order of magnitude greater 

 than the combined wave/current maxima. Such conditions could cause the cap to 

 breach and expose contaminated muds to the water column. The researchers also 

 warned that the EMD cap was composed of the most easily erodible material, 

 fine sand. They recommended that "for a margin of safety... additional cap 

 material be placed over the present cap. This should be. ..sand, silt and clay 

 consisting of mostly mineral grains, with little or no organic matter 

 and.. ..relatively low water content." 18 As far as we know, this recommendation 

 was never followed. 



In 1986, a survey was conducted of the entire Mud Dump Site, including 

 the EMD 19 . This survey concluded that the capped mound within the EMD had 

 not substantially changed in height. However, it did find approximately 130,000 

 cubic yards of material to have accumulated to the north and east of the mound, 

 presumably from disposal operations in the northeast quadrant. 



It also discovered that the sand cap was not made up of over 1 million 

 cubic yards of material as presumed, but that the volume of material calculated to 

 have been deposited on at the EMD was only approximately 800,000 cubic 



16 ibid 



17 SAIC. June 17, 1987. Long-Term Sand Cap Stability: New York 

 Dredged Material Disposal Site (Draft). Newport, Rhode Island. 



18 George L. Freeland et al February 1983. Sediment Cap Stability Study 

 New York Dredged Material Dump Site . Miami. Florida. 



" See footnote 5 



