Portsmouth Harbor Maintenance Dredging

This project consists of the maintenance dredging of 2,300 cubic yards (cy) of ordinary (sand) material at the upper-most end of the Portsmouth Harbor Federal Navigation 35-foot deep channel and turning basin, and the improvement dredging of approximately 674,800 cubic yards (cy) of ordinary (glacial till/outwash/clay) material and 14,700 cy of hard (rock) material to expand the existing 35-foot deep turning basin at the upper-most end of the Portsmouth Harbor Federal Navigation Project.  All depths refer to the plane of Mean Lower Low Water (MLLW).  The dredging work will be accomplished by using a mechanical dredge and scows with disposal work being accomplished using bottom dump scows for in-water placement and pump offloader(s) and hydraulic pipeline for beach placement.  The removal of the hard material will require submarine drilling and confined blasting.  The ordinary and hard (rock) material dredged to maintain and improve the Federal Navigation Project will be transported in scows and disposed of at four separate disposal locations.  All hard (rock) material and approximately 182,300 cubic yards of the ordinary material will be disposed of at the Isle of Shoals North (IOSN) Disposal Site, located in the Gulf of Maine, approximately 12 nautical miles east of Portsmouth, New Hampshire.  Of the remaining quantity of ordinary material, approximately 192,500 cubic yards will be disposed of at the Salisbury and Newbury Nearshore Disposal Sites located offshore from Salisbury and Newbury, Massachusetts, approximately 16 nautical miles south of Portsmouth, and approximately 300,000 cubic yard will be placed as beach fill at Nantasket Beach located in Hull, Massachusetts, approximately 55 nautical miles south of Portsmouth.