Mackinac Island State Harbor, Michigan
United Design Associates
Ryba Marine Construction Co.
Michigan Department of Natural Resources
State of Michigan
Precast concrete Redi-Rock freestanding walls meet project scheduling, accessibility, aesthetic, and functionality requirements for a historic site.
Mackinac Island, known as the Great Lakes’ island jewel, is one of the classic historic parks in the United States. Located at the juncture of Lake Michigan and Lake Huron between Michigan’s upper and lower peninsulas, Mackinac Island attracts more than 1 million visitors each year.
The island is accessed primarily by ferry from the towns of Mackinaw City and St. Ignace, Mich. Mackinac Island State Harbor is the embarking point for thousands of visitors every day during the summer season. Although the look of the harbor is intended to be "historic," it was in need of serious renovation. In 2007, the Michigan Department of Natural Resources (DNR) decided to upgrade the harbor for better functionality and appearance to accommodate the large number of boaters and visitors.
The design team on this project included Ryba Marine Construction Company and United Design Associates, both located in Cheboygan, Mich., as well as the state of Michigan and the DNR.
When DNR officials first began looking at options for renovations of the harbor area, they wanted to use natural stone. However, natural stone proved to be cost prohibitive and nearly impossible to install and complete within the tight time constraints. The Mackinac Island State Harbor facility upgrade had to meet all Americans with Disabilities Act (ADA) requirements, which made natural stone a poor option because of dimensional irregularity.
"The critical points at the sidewalks only had a 3/8-inch tolerance," said Tom Bajko, P.E., from Ryba Marine. "With the ADA requirements for slopes in the sidewalks, this was very important and would have been extremely time consuming to achieve with natural stone."
After studying the budget numbers, ADA requirements, project deadline, and the aesthetics of each option, the design team concluded that Redi-Rock’s consistent dimensions, aesthetic appeal, and ease of installation best met the project’s needs. Redi-Rock’s freestanding blocks, columns, and caps were specified for the job to create a picnic area, seat walls, and fences to separate green space from roadway, as well as to provide stable cleats for boat moorings in the harbor.
|Redi-Rock blocks, manufactured in Charlevoix, Mich., were transported by ferry to Mackinac Island, directly to the harbor project site.|
New construction on Mackinac Island is often tricky because of the rich history of the area and the focus on preservation. Mackinac Island was a popular fur trading outpost and the site of battles during the Revolutionary War and War of 1812. By the 1860s, the island’s industry had shifted to tourism. Travelers from as far as away as Detroit and Chicago flocked to the island for a vacation getaway. In 1875, Mackinac Island was declared the United States’ second national park after Yellowstone. The island was transferred to the jurisdiction of the state of Michigan in 1895, becoming Michigan’s first state park.
Historic sites across the island have been preserved, allowing visitors to step back in time when they step off the ferry boat at Mackinac Island State Harbor. Mackinac Island has prohibited the use of motor vehicles since 1898, with the exception of emergency vehicles such as a police car and fire truck. Visitors and residents get around by foot, bicycle, or by horse and buggy.
The harbor project provided challenges for Ryba Marine’s construction crew. First, the project’s location on an island required transporting a significant amount of materials from the mainland. Second, construction could not begin until the harbor closed for the year in late September, leaving most of the project to be completed during the harsh winter months. Third, Ryba Marine had never installed Redi-Rock.
"The learning curve for installing Redi-Rock was minimal," Bajko said. "The workers had to learn as they went and did not have the luxury of any spare time to learn. This is a first-time installation that came out quite well."
The Redi-Rock blocks were manufactured in Charlevoix, Mich., by MDC Contracting and transported about 60 miles to the ferry dock in St. Ignace where they were loaded onto a barge bound for Mackinac Island. The island’s streets were not used in delivery of the blocks, and construction machinery was kept on barges to preserve the shore. In total, 1,300 Redi-Rock blocks equaling 650 tons were unloaded on the shore and installed. MDC worked closely with Ryba Marine to ensure the proper blocks were delivered at the right time to keep the project on schedule.
|Reinforcing bar expoxied to the bottom of wall caps provide a stable structure for anchoring boat cleats.|
Curved, freestanding blocks created pedestrian overlooks facing the water, featuring four different radii, ranging from 16 feet to 56 feet. Curved, freestanding blocks are produced with special inserts that eliminate the need for cutting the blocks on the job site. The minimum radius is 14 feet 6 inches when all curved Redi-Rock blocks are used. Variable-radius curves are achieved with special inserts and trimming the block as needed. The designers included some creative touches in the project such as using Redi-Rock’s freestanding blocks to make benches for visitors to sit and enjoy the view of the harbor.
The boat cleats at the end of the harbor’s docks needed to be anchored to a stable structure, ensuring the boats’ safe haven amidst the sometimes harsh conditions of summer storms. To give the boats the strong anchor they needed, project designers found a way to make the Redi-Rock freestanding garden blocks act as an anchor for each dock’s cleats.
The garden blocks were attached to the concrete sidewalk using 1-inch threaded bar. Garden blocks have the same basic design as a regular freestanding block except the top of the garden block has a 7.5-inch trough. This trough is typically filled with soil and flowers or other ornamental plants. However, in this application Ryba Marine filled the planter area with concrete. While the concrete was still wet, Ryba placed caps with reinforcing bars on the bottom to secure their position. The boat cleats were then attached by drilling into the caps where bolts were epoxied in place. This creative combination completed a secure cleat for boats to moor in the harbor.
To encourage a better flow of pedestrian, bicycle, and horse and carriage traffic through the park, United Design Associates designed a series of fences integrating Redi-Rock columns connected by fence rails. These columns feature the same cobblestone texture as the freestanding blocks, tying the entire project’s look together. Redi-Rock caps top off each column.
|A trough in garden block—designed to hold soil and plants—is filled with concrete to fasten a cap block with attached rebar.|
The Mackinac Island State Harbor Refuge, rededicated on June 19, 2008, serves as an example for future harbors of refuge in the state of Michigan. For a live look at the completed marina, visit http://mackinacisland.org/webcam.html.
Kevin Loe is business development manager for Redi-Rock International. He can be contacted at firstname.lastname@example.org.