Conceptual Design Report for the Hamilton Dam Modifications Project Flint, Michigan Prepared For: City of Flint P.O. Box 99 Flint, MI 48501-0099 Flint River Watershed Coalition 432 N. Saginaw St. Suite 1001 Flint MI 48502 Prepared By: Gary M. Lacy, P.E. Recreation Engineering and Planning. Boulder, CO 80302 (303) 545-5883 November, 2008
Table of Contents Introduction... 1 Background... 3 Economic Benefit... 6 Site Description... 7 Project Description... 11 Anticipated Use... 13 Accessibility... 14 Maintenance... 15 Costs... 15 Future Work... 15 Conclusion... 16 Appendix 1. Conceptual Cost Estimate... 17 Appendix 2. Concept Plan... 19 (303) 545-5883
Introduction Built in 1920, the Hamilton Dam is located on the Flint River as it flows through the City of Flint, Michigan. It once served not only as a dam, but a pedestrian bridge as well. Today, however, this river-wide dam obstructs the river s flow, presents dangerous structural weaknesses and is a threat to public safety. Because of this current state of disrepair, the Michigan Department of Environmental Quality has mandated the Hamilton Dam be replaced. was contracted to create a conceptual design for such replacement that would provide a unique recreational whitewater opportunity in Flint. The purpose of this project is to replace the current dam with a structurally and hydraulically sound structure that maintains adequate upstream pool elevation, allows for the City of Flint to pump water for a backup water system, maintain adequate bank head pressure to not allow contaminates into the river, provide reasonable fish passage, and provide a recreational amenity. Similar dams in cities across the country have been converted to provide attractive recreational amenities while improving safety and maintaining the purpose of the dam. The resulting improvements not only provide for increased safety in the river, but serve as an attraction to residents and visitors who seek whitewater for recreation, events, and competition. The net effect of such improvements results in transforming a failing dam into a popular community attraction that stimulates the local economy. This report presents a conceptual plan and cost estimate for the construction of improvements to the Hamilton Dam on the Flint River in Flint, Michigan. The conceptual plan consists of recreational boating improvements as well as related bank and (303) 545-5883 1
access improvements. The proposed improvements will create a whitewater paddling amenity for the local community and a resource for the region. The site is ideal due to the amount of available gradient, flow and its location adjacent to the University and downtown area. Adjacent infrastructure including parking, restrooms, lodging and restaurants help make this site an outstanding location for this project. (303) 545-5883 2
Background Many communities across North America are looking to their river corridors, historically centers of industry, as the heart of urban renewal plans. Rivers can serve as the catalyst for economic development, and as the dominant natural feature of communities, accessible river corridors with recreational amenities are key anchors. Whitewater Parks and Courses are increasingly being explored and built by communities looking to create a unique attraction and recreational opportunity of national importance. The term whitewater park is analogous to a brand name that has been generally applied to river access improvement projects all over the US. These projects are located in diverse communities, with diverse goals. The common thread among all of these projects is that elements of a public river corridor had become a liability. Whitewater parks convert river corridors and failing dams from liabilities, to amenities that provide recreational opportunities and economic stimulus. Whitewater parks are an emerging trend in North America that provides river related recreation near a population center. Whitewater parks vary in length from the longest, 1 mile, to the shortest, 1 single feature, but all meet the same goal: attracting diverse users to a single destination where they can recreate without the logistical issues involved in more traditional, point A to point B river trips. These parks can be constructed in all types of rivers and can be designed to achieve a range of different outcomes. In-stream modification, as seen in the Salida Whitewater Park, consists of a feature created with carefully placed, native boulders within the existing channel. The appropriateness of this type of improvement is based on the (303) 545-5883 3
availability of flow, the gradient of the stream in the immediate vicinity of the drop structure, and the geotechnical makeup of the substrata of the river. In-stream whitewater improvements are popular in appropriate rivers around the western US. This structure is located in the Arkansas River in Salida, Colorado. Dam modification whitewater parks are also a commonly pursued option, whereby an existing dam is retrofitted with drop structures to create a whitewater course on the backside of a dam. Dam modifications, like the Rio Vista Dam shown in the photo below, serve to eliminate structural stability issues and mitigate existing navigability hazards while maintaining the existing use of the dam and not negatively impacting the floodplain. These projects are appropriate when a dam s function needs to be maintained but the downstream edge of the dam can be modified for navigation, recreation and fish passage, or when the crest of a dam can be lowered and the vertical fall of the dam can be redistributed through a longer reach. (303) 545-5883 4
This whitewater park in San Marcos, Texas is an example of a dam modification project. The original crest of this dam and its diversion capabilities are maintained while the vertical drop on the back side of the dam is redistributed in a drop/pool sequence. Diverse communities ranging in population and geographic characteristics are turning to their rivers as a source of recreation, education, and local pride. Whitewater parks attract citizens of all ages and socio-economic backgrounds. The operation of these parks across the country has shown that these types of projects provide a number of benefits including new recreational opportunities, economic stimulus, enhanced aquatic habitat and environmental education opportunities. (303) 545-5883 5
Economic Benefit There is substantial, empirical evidence that river access improvements can have significant, positive, economic benefits, for a local community. Whitewater Parks attract a desirable demographic of users between the ages of 25-45 with disposable income and the willingness to travel in pursuit of this specific recreational activity. Golden, Colorado commissioned an economic impact study in the year 2000 for a whitewater park that was built in 1996. At the time of the study, the project was shown to have an annual economic impact of between $1.4million-$2million to the local community. This study was for a stream which has a usable season of three months. The whitewater park in Reno, Nevada has a projected economic impact of $18million over the first decade and contributes to a $9million economic impact of the, annual, three day, Reno River Festival. The Truckee River Whitewater Park at Wingfield, Reno Nevada. (303) 545-5883 6
Site Description Flint River and Hamilton Dam Project Hamilton Dam project site. (Source Google Earth) The location for improvements is at the existing Hamilton Dam located on the Flint River in Flint, Michigan. Due to the site s location adjacent to the University of Michigan and Downtown Flint, it is expected to attract a diverse number of users. (303) 545-5883 7
As built drawings of the existing Hamilton Dam. (Source US Army Corps of Engineers.) (303) 545-5883 8
Monthly Mean Streamflow: USGS 04148500 Flint River near Flint, MI from 1932-2007 2000 1500 1000 500 0 Jan Feb Mar Apr May Jun Jul cfs Aug Sep Oct Nov Dec month Mean-monthly flows at the proposed project site from October, 1926 through September, 1960. (source: http://waterdata.usgs.gov/nwis/monthly.) Flows at the site vary from around 1500 cubic feet per second (cfs) in the early spring, down to around 250 cfs in mid-summer to early fall. Peak streamflow data is shown in Error! Reference source not found.. Extreme flood flows have historically reached above 15,000 cfs in the Flint River. However, flows usually peak in the range of 4,000 cfs. This historic flow data suggests that the project would be useable 12 months a year, weather permitting. The most popular seasons for usage would during the spring and summer months. Use of similar projects typically follows the hydrograph. When flows are higher more experienced users will use the facility; when flows are lower during the summer months less experienced users and bank-based users will frequent the site. (303) 545-5883 9
Historical peak streamflows at the proposed project site (source: waterdata.usgs.gov, station USGS 04148500 Flint River Near Flint, Michigan.) (303) 545-5883 10
Project Description Conceptual Plan for the proposed improvements at Hamilton Dam. This plan illustrates the proposed layout of the suggested improvements at the Hamilton Dam. A full-page version of this drawing is available in Appendix 1. The general layout provides for three whitewater features/grade control structures located in the main channel of the river adjacent to the University. Each feature would consist of a drop structure with approximately two feet of head. The first structure will be located at the existing dam, with the crest being approximately two feet lower than the existing crest. The final two structures will be located downstream from the existing dam, upstream of the Harrison Street Bridge. (303) 545-5883 11
Typical profile view of a low-head dam modified for fish passage and safety. The crest of this low head dam was similarly modified for safe passage. A new pedestrian bridge would be constructed at the location of the dam, with trail extensions to connect the park on river right with existing trails on river left. Selective bank access improvements and bank terracing will be included on both banks between the dam and the Harrison Street Bridge. This terracing will provide safe river access and improve public safety while maintaining existing flood protection. (303) 545-5883 12
Completed bank terracing at the Truckee Whitewater Park in Reno, NV. Reach of the Flint River that would benefit from bank terracing. Anticipated Use This project will serve many users and purposes. The primary purpose of the modifications is to replace the aging and deteriorating dam with a structurally and hydraulically sound structure. Additionally, the site will be designed as an attraction to whitewater enthusiasts such as kayakers, canoeists and rafters. The character of the features created by each of the drop structures will evolve as the flow rates at the site increase and decrease Paddlers at the Pueblo Whitewater Park throughout the year. At lower flows the park will provide recreation opportunities for less experienced river users as well as intermediate and expert users who come to the site for fitness and practice. At higher (303) 545-5883 13
flows of over 1000 cfs the more powerful whitewater features will create a regional draw for intermediate and expert users while still allowing use of the project by inexperienced users. The design can also accommodate upstream fish passage. Future design phases will need to consider the specific needs of critical local fish species. Generally, the proposed grade control structures can provide short sections of both higher velocity flow and velocity shelters to facilitate upstream fish movement. Accessibility The site is immediately accessible through the University of Michigan-Flint campus and the downtown area. Access points would be constructed both upstream and downstream of the whitewater features to allow for ingress and egress to and from the river. (303) 545-5883 14
Maintenance In-stream improvements are virtually maintenance-free. Regular inspections should be scheduled to evaluate any significant erosion during the first year and every year thereafter. Tree, ice and woody debris will be passed in the course of normal flows, but should be removed if suspended during high-use times as they represent an immediate instream hazard. Maintenance of the existing park will require typical park maintenance for parking areas, restrooms, etc. Costs See the attached cost estimate. Normally, the bulk of this cost is in construction of inchannel improvements. In-stream drops and pools should be constructed, along with any related paths/ access ways, during low-flow periods. Reduction in rock costs through donated or stored rock can have a significant impact on the total cost of the project. Future Work If the City decides to go forward with this project, future tasks include but are not necessarily limited to: Detail Design Flood/Fluid Modeling Permit Applications Construction and Bid Documents Construction Phase Services These tasks are categorized in Design and Construction Phase Services, as listed in the attached cost estimate. It is recommended that the design team open a dialogue with (303) 545-5883 15
related planning and government agencies as soon as possible following the decision to proceed, as it is often imperative that these stakeholders be included in the design process. Conclusion Cost effective, recreational safety improvements can be made at the Hamilton Dam site. These improvements will provide a solution to the structural stability concerns at the Hamilton Dam, remove an existing hazard and provide a recreational amenity that will attract recreational users and their families throughout the region, to Flint. The proposed improvements will preserve the base of the existing dam while gradually redistributing the vertical fall to eliminate the existing powerful hydraulic. The hydraulics formed by the whitewater structures will be user friendly and will not act to keep inexperienced boaters or users of inflatable craft trapped. Many communities have found that whitewater parks not only solve safety issues, but also draw residents as well as visitors to the river, thus providing an economic driver for the local community.. Similar improvements have had enormous impacts on the quality of life and local economies of communities throughout the country. REP s $170,000 whitewater park in Golden, Colorado has had an estimated 1.7 to 2 million dollar per year impact on the local economy. Similar estimates have been made for our parks in Breckenridge and Vail. Another project, a two-channel whitewater park on the Truckee River at Wingfield Island in Reno, Nevada, has transformed a neglected and denuded section of downtown into a revitalized urban greenway with walking paths, shaded riverside seating, and picnic areas all surrounded by world-class whitewater. Just like the cities mentioned above, Flint has the potential to create a world-class recreational amenity that could benefit the entire community. For these reasons REP recommends including recreational improvements in the modification of the Hamilton Dam. (303) 545-5883 16
Appendix 1. Conceptual Cost Estimate Flint Michigan-Hamilton Dam Cost Estimate 11/3/2008 Item # Description Estimated Quantity Unit Unit Price Item Total Price 1 Mobilization L.S. L.S. $50,000 $50,000 2 Dewater (During low-flow) open obermyer gates, construct coffer dams and area pumping. L.S. L.S. $240,000 $240,000 3 Demo existing Bridge/Dam super structure and Gates- leave concrete abutment walls and ogee crest. L.S. L.S. $140,000 $140,000 4 Grouted rock drop structures: 4A At Dam Face 1,100 cubic yards grouted rock $190 $209,000 4B Drop # 2 1,600 cubic yards grouted rock $190 $304,000 4C Drop # 3 1,000 cubic yards grouted rock $190 $190,000 5 Boulder edge and terracing 1,400 LF $160 $224,000 6 Large Random Boulders 20 L.S. $400 $8,000 (303) 545-5883 17
7 miscellaneous heavy Equipment cost/hour 240 hours $180 $43,200 8 landscape restoration and miscellaneous signage, put-ins, take-outs and trails L.S. hours $90,000 $90,000 Subtotal $1,498,200 9 Contingency 25% $374,550 10 Total $2,112,462 Design and Permitting 16% $239,712 11 Pedestrain Bridge replacement L.S. $200,000 Itemized costs: Grouted Rock costs per cubic yard Heavy equipment cost/hour Large Random Boulders $190 $180 $400 (303) 545-5883 18
Appendix 2. Concept Plan (303) 545-5883 19
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