Stellwagen Bank Final EIS and Management Plan 



Page 61 



however, factored into the MMS analysis of site 

 suilabihty. The Bureau of Mines made particular 

 reference to the possibihty that concerns over 

 environmental protection "could have significant 

 adverse effects on any dredging and processing 

 operations". (BOM, 1987). Several small deposits 

 of gravel and coarse sand occur on top of the Bank, 

 which could be individually exploited. 



The distribution of gravel and sand on 

 Stellwagen Bank is provided in Figiu-es 11 and 12, 

 respectively. 



Most of the sand and gravel resources on the 

 Bank occur in less than 130 feet, indicating the 

 feasibility of recovery using currently available 

 mining technology. While a number of small gravel 

 deposits have been identified immediately east of 

 the Bank, and in waters off of Cape Ann, these 

 areas are considered too deep to make the deposits 

 economically recoverable (MMS, 1987). Other 

 factors which make Stellwagen Bcmk a desirable 

 source for sand and gravel are its proximity to 

 Boston (approximately 30 miles east of Boston 

 Harbor), and its occurrence in Federal waters, 

 making the area potentially available for leasing 

 (Hassol, 1987). 



Sand and gravel resoiu^ces are unconsolidated 

 deposits classified as "industrial materials" by MMS 

 (Cruickshank, et a]., 1987). These deposits maybe 

 collected directly either at or under the seafloor. 

 While numerous methods have been developed to 

 exploit offshore sources of mineral aggregate, 

 current mining technologies appUcable to sand and 

 gravel deposits on Stellwagen Bank would likely 

 include individual variations of two basic methods: 

 scraping the surface and excavation of pits and 

 tunnels into the surface. Variations in methodology 

 could include both traihng suction dredges 

 (scraping), or anchored suction dredges 

 (excavation). It is likely that the latter method 

 would be used at Stellwagen Bank, depending on 

 water depths at operating locations. Similar 

 methods are routinely used for mining of sand and 

 gravel at depths of less than 100 feet (30.48 meters). 



In general, the environmental effects of offshore 

 sand and gravel mining include: destruction of the 

 existing benthic biota; resuspension of fine 



sediments; and alteration of the surface profile 

 (Hurme and PuUen, 1988). To date, however, there 

 have been few studies thoroughly assessing the 

 effects of offshore mining activities. During the late 

 1970's, the New England Offshore Mining 

 Environmental Study (NOMES) addressed the 

 impacts of commercial-scale mining, although the 

 study was terminated prior to actual test mining. 

 The NOMES project identified several possible 

 results of offshore hydraulic mining for sand jmd 

 gravel, including: formation of stagnant water-filled 

 excavation pits, causing in turn coastal erosion or 

 penetration of freshwater aquifers; harm (or 

 benefit) to fisheries, depending on the physical 

 nature of the bottom surface following excavation; 

 introduction, via discharge plumes, of pollutants and 

 undesirable nutrients, causing interference with 

 fdtering, feeding, and respiratory functions of 

 marine organisms; direct smothering of benthic 

 species; loss of food sources and habitat; lowered 

 photosynthesis and oxygen levels; and degraded 

 appearance of the water itself. Unavoidable changes 

 in bathymetry and bottom type may also cause 

 alterations in population and migration patterns 

 (Hurme and Pullen, 1988). 



Of particular concern at Stellwagen Bank are 

 impacts to fish, invertebrates, and marine mammals 

 resulting from mining operations. The sandy 

 substratum is especially important to sand lance, the 

 primary forage fish for cetaceans. Sand lance 

 burrow into the Bank's sandy substratum during the 

 day, and may also burrow for longer periods of 

 inactivity during the late summer. (S. Katona, 1991). 



In terms of fmfish, there is general agreement 

 among the sources consulted (DeGroot, 1979; ICES, 

 1981; MMS, 1987; Hurme and Pullen, 1988; 

 Oulasvirta and Lehtonen, 1988) that individual adult 

 fish are unlikely to be affected by mining 

 operations, as they are likely to avoid the disturbed 

 site. Early fish life stages are less mobile, however, 

 than adults and more sensitive to elevated 

 suspended sediment concentrations. DeGroot 

 (1979) has determined that dredging and 

 construction of a sand island would cause damage 

 to fisheries of the area, as well as a sizeable 

 permanent economic loss to commercial fisheries 

 (Dfl. 10,000,000, or approximately $ 5.3 million in 

 1990 dollars). In a study of the effects of sand 



