58. LOWER BAI BAaaiERS 



a. General . The Lox^r Bay barriers described below are 

 based on preliminaary studies. Completion of detailed design 

 studies that would prove satisfactory to all interests must 

 await the results of further studies of the effects of the 

 barriers on present conditions within the bay, principally 

 on navigation, pollution and fisheries. The final plan may 

 differ from the plan herein described in providing for larger 

 navigational opening^yLn the West barrier, asA the addition of 

 navigation and sluice gates. 



b. East barrier 



(1) Description . This would be a massive stone 

 structure extending from Conanicut Island 3^200 feet to Newport 

 Neck (see Plate 5). It would have a quarry-run stone core, 

 capped and faced with heavy derrick stones to a depth of 20 

 feet below mean sea level. The top would be 20 feet in width, 

 at an elevation of 22 feet above mean sea level. With sides 

 sloping one vertical on two horizontal the maximum base width 



of the structure would be more than 700 feet. The barrier would 

 be oriented at right angles to the existing navigation channel, 

 and a navigation opening 1,000 feet wide and ^0 feet deep at 

 mean low water would be centered upon this channel. 



(2) Geology . The East Passage of Narragansett Bay 

 at the barrier site occupies a deep trough with water depths 

 reaching l60 feet below m.s.l. Seismic indications are that 

 bedrock lies at a depth of UOO or more feet below. m.s.l. The 

 character of the materials overlying bedrock could not be 

 determined by the seismic method because velocity determinations 

 about equalled that of water. The assun^jtion that fine-grained 

 materials conparable to those found elsewhere in the bay exist 

 at the site has led to the adoption of large settlement factors. 



(3) Design . In view of the huge quantities of fill 

 necessary, the problems of placing it in deep water, and the 

 probability of violent wave attack, rock fill would appear to be 

 mandatory for the East barrier. Quarry-run rock would be 

 adequate for the core, but the need for protection against wave 

 action would require that the top and ^]pper sides be protected 

 with derrick stones of 20 ton minimum size. Conqjlete protection 

 against the 25-foot waves that could occur at the East barrier 

 might require even larger stones. 



UU 



