Urban storm water runoff was a contribut- ing factor to the degradation of an urban hillside shoreline in Madison, Wis. In addition to carrying sediment and pollutants down to the lakefront, heavy rains continued to erode the slope and destroy the existing wooden retaining structure.
Prior to developing design concepts, Dixon Shoreline Landscaping provided a detailed storm water analysis for the project site and surround- ing properties. By using drone technologies, Dixon better understood the urban watershed and assessed the conditions of the existing storm water infrastructure. The next step was to unclog and replace failing infrastructure and install temporary storm water devices to slow and redi- rect the water from the site. As with many his- toric, urban lakefront sites, the biggest challenge was accessibility of the slope. Traditional hard armoring solutions require expansive footings and excessive backfill. With site access limited to a 3-ft wide corridor between buildings, large machinery was not an option. Existing site fea- tures also required a nearly vertical 30-ft tall wall along the property edge.
Envirolok is a suitable solution for challenging sites like this. It is a fully engineered, geobag system developed for stabilization of slopes, shorelines and streambanks. As a vegetative alternative to hard armoring, it is designed for flexibilty and easy installation within a small construction footprint.
Envirolok’s engineering team worked with Dixon to develop a plan that would satisfy regula- tory requirements and meet the aesthetic needs of the property owner. By incorporating a system of geogrid layering and earth anchor reinforcements, Envirolok was able to create a solution that is long lasting.
While many contractors rely on barges or take advantage of winter ice to move materials to the site, Dixon used a mobile conveyor belt system that allowed the team to efficiently move materials up and down the slope with minimal labor. Upon installation in the summer of 2018, the Envirolok system was hydroseeded with a mixture of native grasses and sedges, creating a series of green terraced walls that span the waterfront hillside.
Shortly after construction, an unprecedented 14 in. of rain fell in less than 24 hours. While the project was not yet completely vegetated, the slope, along with additional storm water features, withstood the historic rain event. In less than one year, the terraced walls were fully vegetated, and with the help of storm water features such as Dixon’s patented Lakesaver Bag, runoff has slowed and is filtered or infiltrated before reaching the lake.