The Ledge Amphitheater

Challenge

Central Minnesota is known for its quantity and quality of granite. Abandoned granite quarries are present throughout the area and being transformed into community assets as opposed to waste areas. The Ledge Amphitheater in the City of Waite Park is an example of capitalizing on these opportunities. The City used 20 acres of land donated by a local quarry owner, Martin Marietta, to create a 5,000 seat, open air community amphitheater that will draw people for years to come.

SEH and Oertel Architects partnered with the City to lead this complex project. SEH led the civil engineering efforts, Oertel led the architectural design, and City staff played an instrumental role in moving this project from an idea to a completed, unique amphitheater that engages the natural beauty of Central Minnesota. The collaboration of the entire team made it possible to implement innovative features into the amphitheaters design and transform this abandoned quarry.  

Solution

Cleaning up the quarry – Removing rubble and bedrock blasting
Thoughtful solutions were required to navigate sensitive areas around the quarry and begin the clean-up effort – including shelters for people experiencing homelessness, abandoned railroad tracks and rubble piles.

Significant amounts of bedrock and granite spoil piles – some as big as small vehicles – needed to be moved, including 40-50 ft. piles of granite spoil. In addition, granite soil pile chunks were used for the backslope stabilization at the back of the amphitheater (12-15 ft. in height). These materials were also used for seating, benches, borders to the parking lot and decorative areas.

Another unique approach was implemented for the bedrock blasting that was required. The bedrock blasting area was substantial, so the team conducted resistivity testing along with soil borings. These tools were then used to compare the estimated surface model of bedrock with the surface model of the final design to identify potential conflicts with the bedrock.

Stage and plaza design, location
The City wanted the amphitheater’s stage in a specific location to provide scenic views for audiences. The goal was for the theater to face in a direction so that the audience would see open pit quarries off to either side, with a plaza area that went right up to the quarry edges. Constructing the plaza so close to the quarries required slope stabilization techniques.

Fitting the amphitheater into the site to allow the audience to view the open pit quarries also meant creating the slope of the bowl seating area against the natural slope of the site. With the audience views at the forefront of the planning process, this challenge was solved by importing about 30,000 cubic yards of fill material to create the desired slope of the bowl.

Creating the plaza area presented additional challenges. The theater’s steps, ramps and bowl needed to meet Americans with Disability Act (ADA) requirements. Innovative solutions were necessary to implement these accommodations in such tight areas. The SEH team did this by strategically adding the steps and ramps, providing landscape areas with granite rip rap, and minimizing or adding to certain plaza areas to create appropriate slopes.

Oertel worked with the City to develop an architectural theme based on the quarry and site as it existed for years, that being a granite mine where the types of structures on site are more utilitarian and often simply metal structures and sheds. The buildings on this site include sheet metal siding and metal roofs, with relatively simple forms, to emulate what might be a mining operation. This includes:

• Box office and security building
• Concessions and restroom building
• Performer’s building, which is attached to the main stage

Working with a very limited budget for this otherwise large-scale development, using stick framed buildings with metal skins was also a cost savings measure. With the owner’s concern for minimizing maintenance, the buildings will last for decades without the need for painting and related future maintenance.

Public outreach and perception
The project team engaged the public throughout this project to build support and buy-in. This started with partnerships with area businesses. As noted, Martin Marietta donated the 20 acre quarry. They also partially donated 30,000 cubic yards of fill material. Another local business, Rock on Trucking, donated the trucking of some of the fill material.

Another important part of outreach was engaging the public for naming ideas. After putting out a call for submissions for the amphitheater’s name, the City received hundreds of entries. This was followed by a voting process to decide on the name – with the theater now called “The Ledge.”

The decision was also made to open The Ledge up for tours at about 80-90% construction – this allowed people to see the return on the community’s investments and the opportunities that would be upcoming once the amphitheater was completed.

Economic development
The social considerations of this project were apparent from the start with the way that it proceeded as a public-private partnership. This showed the collective investment from the community in transforming the site and creating a destination that would draw people to Waite Park, spur the local economy, and promote community music and art festivals.

The total cost for the project was $11 million – the City received $5 million in bonding money to complete the project. These efforts were also supported by local fundraising. With an estimated 80,000 visitors per year, The Ledge will provide a boost to the City’s economy and tax base by attracting tourists to experience this unique amphitheater.

Sustainability impacts
This project’s commitment to sustainability starts with a condition that no soil materials could leave the site. For example, salvaged soil stayed on site and was used to create private picnic areas and trail corridors. In addition, granite soil pile chunks were moved and used for backslope stabilization, seating and decorative areas of the theater.

Another important aspect of the project was stormwater treatment. Multiple above ground and underground stormwater applications were used to treat the stormwater on site. The team also had to meet several environmental parameters as a part of the project’s compliance with Minnesota’s B3 Sustainable Building (SB) 2030 Energy Standards.

Awards

• 2021 Engineering Excellence Honor Award | American Council of Engineering Companies, Minnesota Chapter (ACEC-MN)