Agenda - 06-18-2024; 8-m - Approval of a Professional Engineering Services Contract with Schnabel Engineering, Inc. for the Lake Orange Intake Tower Rehabilitation-Replacement Project

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19 schnabel-eng.com 1. Qualifications / Lake Orange Intake Tower / 3 of intake replacement alternatives, we will review existing information on the dam, intake system, and watershed such as as-built drawings, original design documentation, previous inspection and investigation reports, operation and maintenance records, and surveys. In conjunction with our review of existing information, we will setup a kickoff meeting and site walk-through with the County. The purpose of this meeting and walk-through will be to finalize the project approach and field survey plans, observe the existing site conditions in more detail, and discuss key project milestones, operational considerations, site constraints, and other requirements. At the conclusion of the kickoff meeting, we will schedule the field investigations discussed below, the results of which will be used to inform the evaluation of intake rehabilitation or replacement alternatives and design development. 1.2 Site Survey Schnabel understands there was a site survey performed by CH Engineering (now Pennoni) to support erosion repairs on the upstream slope of the earth embankment in 2020. Schnabel will subcontract with Pennoni to update this baseline topographic survey to confirm the general geometry and evaluation of key features including the dam, intake tower, and select portions of areas surrounding the dam. A bathymetric survey of the reservoir area in the vicinity of the intake structure should also be performed as this information will help inform the evaluation of intake replacement alternatives, including options for control of water and stream diversion during construction, and the subsequent design. 1.3 Environmental Investigations Our environmental subconsultant, Three Oaks Engineering (Three Oaks) of Durham, NC, will research jurisdictional wetlands and waters within the project area. Based on our experience, the proposed improvements will impact jurisdictional waters but should qualify for a Nationwide Permit #3. Three Oaks will consult with the USACE and NC DEQ and North Carolina Division of Water Resources (NC DWR) to confirm that the proposed work is compatible with a Nationwide Permit #3. Three Oaks will also advise Schnabel on planning and design of the work to meet USACE, NC DEQ, and NC DWR permit conditions and to avoid the need for compensatory mitigation. 1.4 Underwater Investigation Depending on the anticipated scope of the intake tower rehabilitation or replacement based on the kick off meeting and discussions with the County, an underwater investigation of the existing intake tower and surrounding areas may be prudent to refine project details and reduce risk. Schnabel supported two previous dive inspections of the intake tower and will utilize information gathered during those and will only request an additional underwater investigation if needed. We routinely team with experienced underwater contractors to perform these types of investigations, and we anticipate that the investigation for this project could be completed cost-effectively in one day if it is needed. 1.5 Subsurface Investigation Depending on the anticipated scope of the intake tower rehabilitation or replacement based on the kick off meeting and discussions with the County, a subsurface geotechnical/geological investigation of the intake tower and surrounding areas may be needed to obtain information to support the alternatives analysis and design. Also, it is our understanding that the County intends to keep the reservoir at least partially full during construction of the intake tower rehabilitation/ replacement, this will require the installation of a temporary cofferdam around the intake tower work area to allow for the area to be dewatered. The subsurface investigation will also gather Build Better.Together.