Okaloosa County BOCC — Apr 25, 2013 — CCF05222013_0001 — reading text

Okaloosa Island, Florida Beach Accesses 4, 5, 6 CONCEPTUAL BEACH ACCESS IMPROVEMENTS May 16, 2013 MRD Project Number 13-363 Prepared For: NORTHWEST \\ FLORIDA'S EMERALD COAST Prepared By: mrd associates, inc. Coastal Engineering PREBLE-RISH INC CONSULTING ENGINEERS & SURVEYORS Cine $2 hint yah! cs EXHIBIT A Norriego Point T-Groin Wall Analysis Okaloosa County Taylor Engineering, Inc. Overview Norriego Point, an undeveloped spit separating East Pass and Destin Harbor, continues to experience critical erosion, This chronic erosion required an average annual placement of over 48,000 cubic yards of sand between 1970 and 1999, Two t-head groins constructed in 2003 near the southern limit of the City-owned portion of the Point reduced the erosion and annual sand placement within the vicinity of the structures; however, erosion along the northern tip has continued. The erosion has “flanked” the northernmost groin, and the structure appears to be inducing further erosion landward of the structure, The erosion reduces the storm protection to Destin Harbor and increases the accumulation of sand within Old Pass Lagoon channel, further hindering commercial and recreational vessel traffic. Over the past two years, the City has performed numerous maintenance dredging operations to provide safe navigation; however, the material eroded from Norriego Point quickly returns to the channel resulting in unsafe navigation conditions and significant costs to the City and County for continual maintenance dredging. For these reasons, the currently adopted Inlet Management Plan (Taylor Engineering, 1999) as well as the revised Inlet Management Plan (Coastal Planning and Engineering, 2010) recommend stabilizing Norriego Point to provide storm protection to Destin Harbor and reduce the maintenance dredging requirements within the navigation channel, Stabilizing Norriego Point will also reduce the future emergency fill requirements, allowing the U.S. Army Corps of Engineers (USACE) to place a greater volume of material from channel maintenance dredging events onto adjacent beaches. To facilitate immediate progress of the Norriego Point stabilization project, Okaloosa County has requested Taylor Engineering to provide design alternatives for the proposed first phase of construction, to be implemented immediately following the proposed U.S. Coast Guard maintenance dredging project. The proposed Coast Guard project includes dredging approximately 5,000 cubic yards of sand from the Coast Guard entrance channel and placing the material on Norriego Point to fill in the scour hole and channel that is currently flanking the existing T-groin structure. The proposed first phase of construction includes the reconstruction and landward extension of the existing T-groin return wall to stabilize the two existing (refilled) embayments and inhibit the structure from being flanked again. We have made several key assumptions in developing this scope of work and associated fees for the project. These assumptions, noted below and throughout this scope of work, affect the proposed level of effort and associated costs. If any of the assumptions should prove incorrect, we will submit a proposal to modify our scope of work and our fees accordingly. We have developed this scope of work with the following assumptions and background information: 1, We assume the USACE will perform the proposed Coast Guard channel dredging and place the material within the northern embayment and immediately landward of the northernmost existing T-groin. We further assume the dredge volume will be sufficient to meet the fill templates shown in the FDEP permit drawings for the dredging project. 2. We assume the proposed dredging will occur between Nov — Dec 2013. 3, We assume the City of Destin will receive the regulatory authorizations for the construction of the proposed return wall prior to the Coast Guard channel dredging operations. 4, We assume the City of Destin will provide digital copies of all historic and recent boundary, topographic and bathymetric surveys of Norriego Point. A-1 EXHIBIT A 5. Taylor Engineering will perform preliminary engineering design of the existing northern T-groin return wall currently being permitted for the purposes of cost estimation, Our analysis will not include structure effects on the littoral system and performance of the proposed project. 6. The scope of work does not include final design services or construction phase services for preparing construction drawings, specifications, and bid documents or performing construction administration/ observation, Structural Design Alternatives Analysis Taylor Engineering will review the proposed permit drawings and provide cost estimates for the two design alternatives — sheetpile wall and the all-rock alternative. As the permit drawings do not specify any material type or details for the sheetpile or rock return walls, Taylor Engineering will perform a preliminary engineering analysis of various sheetpile materials (steel, vinyl, etc) and the all rock alternative to determine the most cost-effective alternative, We will assess the material based on assumed design conditions relevant to the future phasing of Norriego Point. Following our analysis, Taylor Engineering will present our findings to the County in a brief letter report. The report will include the following information: . design assumptions for the engineering analysis: typical cross-sections of the alternatives; material descriptions and quantities; opinions of probable cost for the proposed alternatives; and, recommendations for project implementation. oe © © @ @ We will perform these services for a fixed lump sum price of $9,936.00.