Agmt05 Moffatt & Nichol Engineer

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Redwood Shores Lagoon Dredging Project Scope of Services - Moffatt & Nichol Specific tasks will include engineering analysis to estimate volume/location of dredging, potential type of dredge/transport equipment, discussions with City staff to identify potential disposal sites or temporary processing sites, discussions with resource agencies and contractors to identify other projects in the vicinity which may need dredged material as construction fill or for marsh restoration. This will include the proposed Bair Island as well as other restoration projects in the vicinity. A hydrographic survey of the lagoon system was completed recently, which shows that most of the sedimentation (1 to 2 feet) is in the intake arms of the lagoon and in the arms of the lagoons near Marlin Park and Shorebird Park. In addition, the areas between Bridge and Shell, and around Baltic Circle and Rockport Avenue show sedimentation up to 1 foot. A preliminary analysis indicates the volume of sediment to be about 40,000 cubic yards (CY). Actual dredging volumes, which need to account for over-dredging, are estimated to be between 50,000 and 60,000 CY. Because the material is spread out thinly, an over-dredge allowance usually adds a significant quantity to the volume of material to be dredged and permitted. Also, the presence of docks and continued recreational uses such as boating and public access, and original construction methods for the lagoon (such as rip-rap slopes and diking for salt ponds) may pose design and construction constraints. The characteristics, volume, and distribution of sediments typically dictate construction method. For example, clamshell or bucket dredging is more suitable for locations where the deposited material is several feet thick, and where depths are large enough to support barges to transport the material. Deliverable.. Technical Memorandum - Initial Dredging Assessment (Draft & Final) Task 1.3 - Prepare a Sediment Sampling and Analysis Plan The first step in sediment characterization is to obtain concurrence from the DMMO on sampling and testing protocol for dredged sediments, as well as sediments from the potential disposal site. This takes the form of a sediment Sampling and Analysis Plan (SAP) which needs to be submitted to DMMO for approval prior to sampling. The purpose of the SAP is to convey the proposed methods for evaluation of dredging and disposal/reuse options. The SAP will include estimates of dredging volume, potential disposal and reuse options, areas of the lagoon proposed to be composited, number of coring locations within each area, approximate core lengths, and other specifics on testing. We will coordinate with regulatory agencies in association with Kinnetic Laboratories (KLI), who will be a sub-consultant to us. A comprehensive SAP will be prepared by KLI, which will include a detailed description of the sampling procedures, equipment, and quality assurance practices proposed for collecting the samples. The SAP will also contain a discussion of proposed chemical and testing procedures, contingency bioassay procedures, and associated Quality Assurance/Quality Control (QA/QC) measures to be performed in compliance with all DMMO requirements. M&N will prepare the required Section 404(b) (1) documentation concurrent with the SAP. A draft copy of the Alternatives Analysis will be provided to the City for comment prior to submission of a final copy to the DMMO. The documentation will include a description of the lagoon and its history, the minimum dredging requirements, the scope of the current dredging episode, and identification with preliminary descriptions of all potential disposal sites. The list 2