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HomeMy WebLinkAboutStructural Engineering - bulkhead 43021 ckCla COASTAL engineering co. Date 04/30/2021 Project Number: C19633.00 To: Skippy's Pier 1 Marina Attn: Sandy DiGiovanni P.O. Box 370 Yarmouth, MA 02664 VIA EMAIL: spashun(aJaol.com From: Coastal Engineering Company, Inc. (CEC) 260 Cranberry Highway Orleans, MA 02563 Re: Structural Consultation for Marine Bulkhead Skippy's Pier 1 Marina 17 Neptune Lane, South Yarmouth, MA MEMORANDUM Dear Sandy, Pursuant to your request, Coastal Engineering Company, Inc. (CEC) visited the site of the reference property on Thursday, April 22nd to conduct a visual conditions assessment of the existing timber marine bulkhead. The purpose of the investigation and this assessment has been to observe and evaluate the structural conditions of the bulkhead as required by the Town of Yarmouth's Building Department and outlined in a letter to Neptune Lane LLC dated April 16th, 2021. The letter raises concerns about the structural integrity of the bulkhead and potential for failure and residual harm to adjacent floating dock and deck structures. This assessment concludes that the bulkhead is in serious condition and is in need of immediate repair. Until recommended repairs are made, there should be limitations of use of a portion of the deck structure. Ultimately, it is recommended that the wall is replaced. OBSERVATIONS The existing bulkhead consists of a timber soldier pile system that is approximately 160 feet long. The structural assembly generally consists of 12 inch diameter piles spaced at approximately 8-10 feet. Inboard of the piles, there are three levels of timber wale members consisting, from bottom to top, of a 10x10 lower wale, 6x6 middle wale, and 6x10 (on flat) top wale. According to the reference Chapter 91 License Plan No. 3032 dated 9/7/1993 by William Lieberman, P.E., the wall is restrained by dead- man anchors on the retained side of the wall at approximately the location of the middl- . - - 2$O Cranberry Highway,Orleans,MA 02653 Orleans I Sandwich I Nantucket 508.255.6511 I coastalengineeringcompany.com CEC#:C19633.00 Skippy's Pier 1 Marina The wall sheeting consists of 4x10 tongue and groove members. The overall wall height is approximately 11 feet from mud line to top of wall. There is a floating dock at the base of the seaward side of the bulkhead. Landward of the wall, there is a pile supported deck approximately 8 feet from the bulkhead. The following is a list of specific observations noted during the site visit: 1. Overall, the wall is moderately deteriorated, however there are portions of the wall that are severely deteriorated and failed. a. The center 6x6 wale is seriously deteriorated and completely missing in some locations. Due to this, bearing plates for the tie-backs to the dead-man anchors have punched through the beams allowing the wall to deflect seaward approximately 6 inches in these locations. 2. Two of the soldier piles are broken where the lower 10x10 wale is connected. 3. In a few locations, the tie-backs that connect the piles to the dead-man anchors are missing or have been previously cut. 4. Approximately at the center of the wall length, it appears that the tie-back connecting the pile to the dead-man anchor has failed. Due to this, the pile and the wall have deflected outward about 1 foot more than adjacent parts of the wall. EVALUATION The existing bulkhead is in serious condition and repairs should be made immediately to prevent further deterioration and failure. The failed 6x6 center wales have caused the wall to deflect forward in many locations, and increases the unsupported length of the timber sheeting past a safe load capacity. Additionally, the potentially failed tie-back increases loads on adjacent tie-backs. An analysis of the bulkhead and deck yields that upon full loading of the seaward portion of the deck during restaurant operation, the driving pressure behind the bulkhead increases approximately 3% to 5%, exceeding an allowable safe loading for the wall that is in serious condition. Until repairs are made, limitations of use should be implemented at the deck to reduce the loading on the bulkhead and to mitigate risk of injury and financial loss. RECOMMENDATIONS Immediate Recommendations 1. The deteriorated 6x6 center wale should be replaced with new 6x6 wales with scarf joints at the intersecting 6x6 sections. The existing tie-backs that have punched through the wales should be spliced with new threaded rod and connected to the 6x6 wales, Where the wales intersect the soldier piles, shims should be installed to transfer loads to the piles. 2. Until the immediate repairs are made, the outer 10 feet portion of the timber deck extending from the center support beam to the seaward face of deck should be limited to no more than 10 pounds per square foot of loading, or the equivalent of maintenance work only. It is not recommended that the space be used for restaurant or entertainment use. 4/30/2021 Page 2 of 3 CEC#:C19633.00 Skippy's Pier 1 Marina 3. The use of the greenspace within 10 feet of the southern portion of the wall should be limited to maintenance purposes or access to the floating dock only. Short-Term Recommendations 1. Once the immediate recommendations are implemented, the work should be evaluated for adequacy. If acceptable, the safe live loading on the deck can be re-evaluated. 2. Ultimately the bulkhead should be replaced within a 1-3 year time frame. Permitting Note Though not included in the scope of this memorandum, the proposed recommendations might require regulatory review and environmental permitting prior to construction. Please let us know if you have any questions concerning this memo, or if we can provide any further assistance. Sincerely, Coastal Engineering Company, Inc. ���,'IH OF MASS q ° NICHOLAS Sy011. s ,0 +..5-073 130 v SSrO N A L Est' Nicholas (Cole) Bateman, P.E. Senior Structural Engineer 4/30/2021 Page 3 of 3