Precast Solutions - Winter 2009 - (Page 5) water fisheries in Lake Pend Oreille during construction operations near the lakeshore. Consequently, marina construction had to take place at low-water levels during the off season so as not to disturb the lake’s waters, bottom ecology or fisheries. A dam controls lake water levels, which fluctuate from 7 feet to 12 feet deep, depending on annual snowfall, water runoff and other climatic conditions. Lake levels are drawn down beginning in September in conjunction with the end of the summer season. supports would prove too noisy for the envisioned ambience. Developers felt that permanent boat docks built on steel piles would provide the most maintenance-free design for the marina’s water level fluctuations. Turning to an experienced marina builder and designer, Dana Martin of Sandpoint, Idaho, found the answers the investors were seeking (see the sidebar “Why a Seasoned Marina Builder Promotes Precast”). As the project’s designer and superintendent, Martin knew he needed a structural system that could be built during Idaho’s harsh winters and provide needed environmental protection mandated by the Idaho DNR. New marina part of up scale development With these environmental constraints in mind, Beyond Hope’s investors put together an integrated and comprehensive plan to develop the site beginning with a complete reconstruction of the existing dilapidated boat basin. The lakeside resort had long been a typical summer campground and RV site that suffered from lack of upkeep and capital improvements. Because the water level fluctuates considerably, the option of building floating docks that would rise and fall with the lake’s surface was problematic. The depth of the marina is about 6 to 7 feet during high season. When the lake’s water levels are drawn down in the fall, developers could consider scheduling initial earthmoving operations without adversely impacting the lake’s natural resources or having to resort to erecting expensive sheet piling to protect the environment. When driving sheet piling to dewater shoreline projects, both the aquatic and bottom organisms are adversely affected during driving operations and when the area landward of the piling is subsequently pumped out for construction operations. The site’s investors also wanted to create stylish new docks for the marina that would withstand the test of time. Floating docks were first considered but were found to be less attractive (docks lying on the uneven lakebed in winter) and platforms riding up and down on Winter construction Alternative materials for the marina were considered by the owners and the project superintendent. Winter-time construction would not be practical using a cast-in-place concrete system. With a cast-in-place concrete design, pumping and shoring formwork would be required as well as protective tenting and heat to protect the concrete during coldweather curing. More importantly, heavy ready-mixed concrete trucks were not permitted to travel on the local roads during the winter due to the damage they might cause during seasonal freeze-thaw cycles. Martin knew that precast concrete could be erected during cold weather and could be fabricated to look like natural stone in retaining wall and breakwater systems. Not only would precast concrete be more versatile for the site conditions, but the cost of precast was equivalent to a cast-in-place alternative, because precast did not require laborintensive shoring and formwork construction. The selection of precast architectural and finish designs would also meet the owners’ demands for an aesthetically pleasing facility. Talking with fabricators at Wilbert Precast Inc. in Spokane, Wash., would be Martin’s next step. Precast system Wilbert Precast provides a wide variety of precast concrete products to the northwestern states. The precaster and project superintendent knew the first task was to design precast retaining walls to be built throughout the entire marina. Redi-Rock seemed to make the most sense for the project, because it offers a very natural stone finish, and the system has proven to withstand the constant battering of waves in marine conditions. Beyond Hope’s owners wanted the stone walls to run continuously on both sides of the marina and extend out into the lake. The solution was to create large precast panels using liners that would give the appearance of stone walls running seamlessly into the water. In order to support the precast panels, the contractor drove large Hpile beams vertically into the lake bed at intervals of about 12 feet. The precast panels were manufactured with a smooth picture-frame look on the edges so they would fit firmly against the steel H-beams. The maximum height of the jetty wall is 9 feet tall, and it appears to diminish in height as it runs out into the lake. To save time and money, the precaster manufactured smooth panels for some of the lower walls; www.precastsolutions.org Winter 2009 | Precast Solutions http://www.precastsolutions.org
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