EROSION AND SEDIMENTATION CONSULTATION
R. CRAIG FINDLAY, PH.D., P.E., G.E.
Noxon Rapids and Cabinet Gorge Projects Project, Erosion and Sedimentation Consultation in Support of FERC Relicensing, Clark Fork River, Montana, Avista Corporation - Dr. Findlay conducted an extensive baseline study of shoreline erosion for Avista Coporation's (formerly Washington Water Power Company) Noxon Rapids and Cabinet Gorge Projects on the Clark Fork River in Northwestern Montana. The study included mapping over 130 miles of shoreline and documenting erosion conditions at 67 study sites. The findings of the field work as well as engineering assessment to characterize the erosion processes were documented in a summary report. He is currently serving on the Erosion Task Force and is a consultant on erosion and sediment issues for relicensing of the project. The erosion and sedimentation aspects of the project relicensing are the subject of a paper to be presented at the ASCE Waterpower 99 Conference.
Spokane River Projects, Shoreline Erosion Study, Spokane River, Washington, Avista Corporation - Dr. Findlay conducted an extensive baseline study of shoreline erosion for the reservoirs of Avista Corporation's (formerly Washington Water Power) Upper Falls, Monroe Street, Nine Mile, Long Lake and Little Falls projects on the Spokane River in Spokane, Washington. The study included mapping over 60 miles of shoreline and documenting erosion conditions at 40 study sites. The findings of the field work as well as engineering assessment to characterize the erosion processes were documented in a summary report.
Bridgewater Development, PMF Dam Erosion Analysis, Catawba River, North Carolina, Duke Power Company - Duke Power Company was faced with the possibility of riprap stabilization of the upper portion of three hydraulic fill dams of the Bridgewater Development against floods approaching PMF level. Access to the areas to be stabilized and quantities of material involved make the construction logistics difficult and expensive. Duke retained Dr. Findlay to assess the erosion of the dams which would occur under such a flood condition. An analytical approach, based on predicted wave height, dam slope and mass-balance wave erosion theory was developed and indicated that although some damage of the face of the dam would occur under such a flood scenario, the dam would not be breached. As a result of the analysis, Duke decided they would prefer to fix the PMF damage should it occur, rather than expend the resources and effort necessary to armor the dams against potential flood erosion. Duke is currently reviewing the case with the FERC, using the analysis performed by ND&T as the basis for their proposal not armor the dams at this time.
Maritimes & Northeast Pipeline Project, Erosion and Sediment Control Consultation, Maine, Duke Energy Corporation - Assisted Maritimes & Northeast (M&N) in negotiating with the Maine Department of Environmental Protection (DEP) on erosion and sediment control standards pertaining to this 380 mile (mainline and laterals) pipeline project across the state of Maine. Because the DEP erosion control standards applied to general development projects, negotiations with DEP centered around developing specific erosion and sediment control standards applicable to pipeline projects. Developed responses and alternatives to DEP's review comments on M&N's erosion and sediment control plan, and participated in meetings with DEP to develop standards acceptable to both parties.
Hydraulic and Scour Analysis, Proposed Carlton Bridge, Bath, Maine, Hardesty and Hanover - Dr. Findlay was project manager and lead geotechnical engineer to perform a hydraulic and scour analysis for a proposed high bridge over the tidal Kennebec River in Bath, Maine. The bridge is proposed by the Maine Department of Transportation and is to consist of six spans, including a lift span situated over the channel portion of the river. The bridge is to be supported by five in-water piers, and has a total length of over 2,500 feet. Dr. Findlay served as project manager and lead geotechnical engineer for assessing scour potential. To develop design flood levels for the bridge, ND&T used the model DAMBRK to evaluate the extreme water levels at the proposed river crossing for various conditions of flood flows and storm surge. Scour analysis was a three part process. First, particle sized analyses were performed on sediment samples of the river sediment. Second, modeling of the various combinations of extreme storm surges and tides using the model FASTTABS determined flow velocity distribution and vectors around the bridge piers. In the third stem, an empirical scour model was used to estimate potential scour depth at each pier, considering sediment type, pier geometry, flow depth, and velocity distribution and vectors around each pier. The scour depths, computed using the CSU method, were compared to scour observations made at the existing bridge piers. Recommended design foundation support elevations were provided based on the results of the scour assessment.
Hydro-Kennebec Project, Increased Headpond Level, Kennebec River, Maine, Scott Paper Company - Dr. Findlay was the lead geotechnical engineer for assessment of several miles of shoreline which were to be impacted by raising the normal water elevation of the existing dam at Scott Paper Company's Winslow, Maine paper making facility. This increase in dam height resulted in a substantial increase in the impoundment elevation, affecting the shoreline at several industrial and residential areas. Assessment was made in two phases; a preliminary phase to evaluate the impact at individual locations based on observation, and a follow-up phase which included subsurface investigation and additional assessment at critically impacted areas. The assessment resulted in delineation of areas and recommended methods for slope stabilization. Work included development of contract plans and specifications for implementation of the recommendations. Involvement included consultation and monitoring services through construction.
Eustis Hydroelectric Project, Shoreline Stabilization Project, Dead River, Maine, Consolidated Hydro Incorporated - Dr. Findlay designed riprap slope revetment to mitigate erosion of a significant archaeological site for Consolidated Hydroelectric, Inc. Design included land and bathymetric survey, field observation of ongoing erosional processes, riprap design based on expected flows, and preparation of plans and specifications for construction of the remediation.
Edwards Project, Sediment Study, Kennebec River, Maine, Edwards Manufacturing Company - Dr. Findlay planned and coordinated a sediment study to assess the amount and distribution of sediment in the reservoir behind Edwards Dam as part of a dam removal study. This assessment was necessary to further assess the environmental effects of dam removal on introducing sediment into downstream flow. The sediment was surveyed by a number of cross sections and profiles using ground penetrating radar. The generated cross section and profiles were interpreted to estimate sediment volume. Sediment samples were retrieved at several representative locations for testing of metals and other priority pollutants to assess the potential for downstream contamination and means of sediment disposal that would be necessary in the case of dam removal.
Beaver River Project, Shoreline Erosion Study, Beaver, River, New York, Niagara Mohawk Power Corporation -Niagara Mohawk - Power Corporation was requested by FERC as part of their relicensing effort to map all erosion occurring on their Beaver River System due to reservoir level fluctuations. This was part of a FERC request to assess the impact of operating the eight developments of the hydro system as run-of-river as an alternative to the current peaking mode. Since reservoir bank erosion and instability could result from causes other than reservoir fluctuation, simply mapping all erosion occurring would be misleading. Because of this, the assessment not only mapped and inventoried locations and type of erosion/instability that were occurring but also characterized the erosive/destabilizing forces occurring on the reservoirs. The project was the subject of a technical paper to be presented by Dr. Findlay at the United States Committee on Large Dams (USCOLD) Annual Conference in 1995, and published in the USCOLD publication Sediment Management and Erosion Control.
Northeast Wind Energy Station, Erosion and Sediment Control Consultation and Expert Witness, Boundary Mountains, Maine, Kenetech Corporation - Served as expert witness in permitting hearings and liaison with soil conservation officials for permitting and preliminary design of this proposed 250 MW wind energy station to be constructed over fragile, erosion susceptible mountain soils. In addition, responsibilities included preliminary geotechnical investigation, survey reconnaissance, and civil engineering design (full plans and specifications) for a 21 mile transmission line and several miles of access roads for the first phase of development. This included layout of the access roads and development of permanent and temporary erosion and sedimentation control measures in consideration of the heightened environmental concern regarding the fragile mountain soils.
Corporate Headquarters Campus Expansion, Erosion and Sediment Control Consultation and Project Manager, Portland, Maine, UNUM Life Insurance of America - Developed a phased erosion and sediment control plan for a proposed 30 acre expansion of this existing Corporate Headquarters. The site is adjacent to the Presumpscot River, for which local residents and environmental agencies are extremely sensitive to construction related sedimentation. The plan included use of diversion and retention dikes, sedimentation basins and numerous permanent and temporary erosion and sediment control measures, and was scrutinized by the county soil conservation agency, Maine Department of Environmental Protection, and Portland City Officials.
Oneida Project, Sediment Transport Study, Bear River, Idaho, Pacificorp - Dr. Findlay is the technical lead to direct and conduct a sediment transport study for the subject project. The sediment transport into the reservoir, out of the reservoir, and at various points in the river downstream of the project are being studied by field measurements at various flows. The geomorphology of the river below the project is being examined to determine the project effect on sediment loading and stream bank erosion. This includes consideration of the effects of irrigation canal discharge downstream of the project. Current and historical aerial photos are being used to compare channel conditions relative to sinuosity, width and curvature in the meandering bends. The study is also evaluating the relationship between project and sediment movement as well as assessment of sediment sources entering the Bear River.
Brassua Hydroelectric Project, Expert Witness for Piping Failure, Rockwood, Maine - Dr. Findlay was retained as an expert witness for the contractor during post-construction litigation of a piping failure which developed during construction. The piping developed underneath an existing concrete gravity dam founded on glacial till. Dr. Findlay thoroughly reviewed the project design and construction documentation and provided a deposition during the discovery period. The litigating parties decided to attempt mediation to settle the case. Dr. Findlay made a technical presentation for a mediation hearing on the mechanics of piping and a review of the chronology of events leading to the piping failure.
Drawdown Effects on Bank Stability, Confidential Project - A client was interested in determining how the nominal 2-foot-daily drawdown at one of their reservoirs might safely be interpreted to mitigate reservoir bank stability. For example, if a one-foot rise followed by a three-foot draft in 24 hours could be interpreted as a "net" 2-foot-daily drawdown, some optimization of reservoir operation could be realized, provided such operation did not exacerbate bank erosion. Reservoir fluctuations can impact bank stability if the groundwater does not immediately equilibrate with reservoir level changes. In other words, the greater the lag time of groundwater response, the greater impact on slope stability of the reservoir banks. As a result, the study planned and conducted by Dr. Findlay included field samples and testing, laboratory testing, and groundwater modeling of the response of the water table in the reservoir banks to various reservoir fluctuation scenarios at three selected critical sites. Field work included in situ permeability testing. The USGS groundwater flow model MODFLOW was used to assess groundwater response to fluctuations. The resulting groundwater information was then used to analyze impacts on slope stability. Slope stability analysis was completed using the program STABRD (developed at the University of California at Berkeley) to compute the effects of the groundwater lag on slope stability. Preliminary results of the study indicate the "net" interpretation will have no significant impact on bank stability up to incremental level changes of 4 feet.
Orono Dam, Dam Removal Study, Penobscot River, Bangor Hydro-Electric Company - Dr. Findlay was the lead geotechnical engineer to assess erosion and slope instability aspects of various degrees of dam removal. Assessment included consideration of increased hydraulic flows on aggregation of river sediment, as well as mapping of geologic conditions on the reservoir during a drawdown study.
Aroostook and Millinocket Lake Projects, Shoreline Erosion Studies, Aroostook River, Maine, Maine Public Service Company - Dr. Findlay was retained to assess the erosion potential of several archaeological sites on river and lake settings. He evaluated erosion potential due to river flow, wave action, and impoundment level changes, and provided recommendations regarding alternatives to Phase III archaeological investigation.
Spencer Hydro Project, Upgrade Feasibility Study, Niobrara River, Nebraska, Nebraska Public Power District - ND&T was selected to evaluate approaches for remediation of the Spencer Hydro Project on the Niobrara River in northeastern Nebraska. The project is owned and operated by the Nebraska Public Power District. The river carries a heavy sediment load, and the reservoir is almost completely filled with alluvial material. Geotechnical engineering services provided by Dr. Findlay included evaluation of sediment sluicing options and the potential of sediment siphoning as a possible future operation alternative. The spillway structure was founded on Pierre Shale, an expansive bentonite shale, and had to be evaluated for sliding stability. Because the rock erodes easily, the tailrace has eroded about 10 to 20 feet since the project was constructed. The reservoir and tailrace are bordered by cliffs of Pierre Shale which are undergoing continuing erosion. Assessment of remediation alternatives included consideration of impacts of remediation alternatives on continued erosion of the tailrace channel and slope stability of the adjacent cliffs.