1018 14TH ST 2023-02-09 - Laserfiche WebLink

SHANNON MMILSON,INC. from those upon which our recommendations are based. The follmN ing sections discuss some construction considerations for this project. 5.1 Sheet Pile Installation We understand that sheet piles will be used for the new bulkhead wall. Sheet piles may be installed with a vibratory and/or impact hammer. Vibratory hammers would likely be an efficient installation method for penetration through the loose to medium dense sand and gravel soils. To facilitate penetration through the dense to very dense beach and glacial deposits; however, an impact hammer would likely be more efficient. The Contractor should be prepared with both types of hammers to install the sheet piles. If existing riprap is present at pile locations, it should be removed prior to installation of the sheet piles. If riprap is removed,the Contractor should be careful not to undermine the existing bulkhead in the removal areas. Depending on the required depth of the sheet piles, predrilling may be required to facilitate sheet pile penetration into the very dense glacial deposits. It should be noted that the existing site soils consist of loose to very dense sand and gravel soils. Wood was encountered at several boring locations. The wood is likely construction debris from previous work on site, buried historic structures, wood chips, or driftwood. The Contractor should be made aware that difficult driving conditions may exist because of the presence of dense soils containing gravels and wood. Care should be taken during sheet pile installation to maintain proper interlocking of the sheet piles. Because of the presence of gravels and wood in the subsurface soils, the sheet piles may deflect as they are driven or vibrated into the ground. The Contractor should use an iterative process to install adjacent sheet piles. For example, a series of piles can be installed to a depth of about half the required penetration. Then further penetration can be achieved by driving each pile a few feet and then the adjacent piles a few feet, etc. This iterative method would allow for better control of deflections and thereby result in greater success with maintaining the proper interlocking between the sheet piles. There is the possibility that soil setup could occur. Iterative driving should be accomplished in a timely manner. 5.2 Steel Pipe Pile Installation The viewing platform structure open end pipe piles can be installed with an impact hammer and/or a vibratory hammer. Pile driving should be monitored by taking a continuous driving record of each pile. For this purpose, the Contractor should be required to mark the pile in I-foot intervals. The pile-driving record should include hammer stroke and blows per foot for impact 21-1-21761-003-R I f.docx/wp/clp 21-1-21761-00, 17