<P>70The Military Engineer ? July-August ? 2010 kicked out as the scour hole grew not only in depth, but in width towards the station. Back?ll had begun migrating under the toe of the bulkhead and into the river; the waterfront structure was no longer stable and the station was in jeopardy. The Coast Guard installed a real-time monitoring system on the bulkhead, the operations building and the ground be- hind the bulkhead. The system recorded the locations of multiple sensors every four hours and used an integrated, web- based, automated alarm system to trigger automatic e-mail noti?cations to the proj- ect team. A major concern was that the bulkheads southwest corner and south wall would also fail in a similar manner. Although the failure of the northern end of the west wall was relatively limited, failure of the corner and the south wall would be catastrophic. The Coast Guard tasked Collins Engi- neers with the design of a short-term emer- gency repair to stabilize the bulkhead and buy time until a more permanent solution could be implemented. The bulkhead wall had been constructed in several phases, with the sheet piles of the southwest cor- ner and south bulkhead driven to a depth of 50-ft—more than 15-ft lower than the failed section. Underwater inspections had identi?ed the presence of riprap along the toe, but the extent of the armoring had never before been quanti?ed. Another Dimension As part of the design effort for the west bulkhead repairs, an underwater acousti- cal scan of the entire bulkhead sections was performed. The scan identi?ed and dimensioned all existing toe armoring and con?rmed the lack of armoring along the west wall. The scan accomplished two things: It allayed fears about the imminent failure of the southwest corner and the south wall, and it identi?ed where addi- tional toe armoring was necessary. Using the elevations and the slopes of the exist- ing toe armoring, an analysis con?rmed the toe of the south wall was stable, though it was literally feet from the hole. Conse- quently, it could be concluded that the failure of the bulkhead sections nearest the large scour hole was not imminent. The scan also was used to design the emergency placement of toe armor, pin- pointing the locations where riprap was required along the west bulkhead. The scans provided a 3-D measured view of the failed bulkhead. Riprap was then placed far enough off the face of the wall to ensure that no stone was piled on top of the toe of the sheets. Use of the scans, even in these emergency conditions, allowed an optimized design of riprap placement to ensure infrastructure safety. Approximately 1,000-T of 6-in to 6-ft di- ameter stone was placed at the toe of the bulkhead from the north end of the west- ern bulkhead towards the center of the bulkhead in November 2008. The riprap temporarily stabilized the bulkhead as a more permanent structural solution was designed and materials were procured. A second underwater acoustical scan was performed that veri?ed the contrac- tors correct placement of the riprap. The results of this scan, as well as the proper placement of the rip rap, alleviated fears of a sudden and catastrophic failure of the bulkhead while awaiting the temporary repairs. Again, the elevations and slopes of the toe armor were veri?ed by the scan. A Temporary Fix A temporary repair was completed in 2009 to further stabilize the wall while a long-term solution was studied. The sheet- pile bulkhead was built to a toe elevation of 65-ft with a new tieback system installed to support the increased size of the sheet piles. The sinkhole was then back?lled be- hind the bulkhead and the bulkhead has remained stable since completion. The underwater acoustical scans pro- vided bene?ts beyond their intended use. The scans and their images were initially obtained only for use by the structural en- gineers and the construction engineers. The Coast Guard engineers charged with the successful execution of this project quickly learned that the images were an important tool in explaining both the need and the urgency of the repairs to non-technical decision makers within the organization and local area. Because they could see the problem, the Coast Guard personnel charged with funding allocation could more easily understand the problem and its urgency. Similarly, the scans were included in all environmental permitting applications, highlighting both the prob- lem and its urgency. Permits were readily obtained for the bulkhead repairs, a pro- cess that normally takes several months. Since 2008, the Coast Guard has made efforts to study the hydraulics at the site and move toward a permanent, long-term solution. Proposals for a design-build project to replace most of the bulkhead sections were requested and submitted in early 2010. The proposed rehabilitation includes the realignment of the bulkhead, eliminating the southwest corner of the station in its entirety. It also provided ad- ditional armoring of the north shoreline of the waterfront adjacent to the west bulk- head to curb shoreline erosion. Lt. Cdr. Jorge Martinez, USCG, is Executive Of?- cer, USCGC EAGLE (WIX 327); 860-439-1562 or jorge.martinez@uscg.mil. Lt. Colleen Symansky, PMP, USCG, is Construc- tion Project Manager, USCG CEU Cleveland; 216-902-6268 or colleen.a.symansky@uscg.mil. Lynn Stock, P.E., is Structural Engineer, and Eliz- abeth Burkhart, P.E., LEED AP, M.SAME, is Fed- eral Programs Lead, Collins Engineers Inc. They can be reached at 312-704-9300 or lstock@col- linsengr.com, and 312-704-9300 or eburkhart@ collinsengr.com, respectively. An underwater acoustical scan of the west bulkhead performed in 2008 shows the newly- placed rip rap. Image by Brian Dilworth STA. 0+30STA. 1+00STA. 0+50STA. 1+88STA. 3+00STA. 3+41 Timber Fender(Vertical Planks) Old BulkheadSectionNew BulkheadSection Old TimberSheeting W.L. Elev. +3.0(+0.1) Channel Bottom Elevation on 10/8/08 Newly PlacedRiprap</p> <UL><LI><a href="http://www.stallionpublishers.com/publication/609/tofzxaosm/1/1/">Front-Cover</a></LI> <LI><a href="http://www.stallionpublishers.com/publication/609/tofzxaosm/2/2/">Inside-Front-Cover</a></LI> <LI><a href="http://www.stallionpublishers.com/publication/609/tofzxaosm/3/3/">Page-1</a></LI> <LI><a href="http://www.stallionpublishers.com/publication/609/tofzxaosm/4/4/">Page-2</a></LI> <LI><a href="http://www.stallionpublishers.com/publication/609/tofzxaosm/5/5/">Page-3</a></LI> <LI><a href="http://www.stallionpublishers.com/publication/609/tofzxaosm/6/6/">Page-4</a></LI> <LI><a href="http://www.stallionpublishers.com/publication/609/tofzxaosm/7/7/">Page-5</a></LI> <LI><a href="http://www.stallionpublishers.com/publication/609/tofzxaosm/8/8/">Page-6</a></LI> <LI><a href="http://www.stallionpublishers.com/publication/609/tofzxaosm/9/9/">Page-7</a></LI> <LI><a 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