Patrick Cloonan of Cloonan Design Services walked a couple sites for a client that wanted to craft their home from the ground up.

The view was amazing and beautiful however it was the site of an eroding hillside. Cloonan soon assembled a team of engineers, architects, and of course, Landscape Architects who used their skills to investigate what it would take to make this a buildable lot that would be fit for a home.

The site is part of a subdivision that originally consisted of 26 acres of sparsely wooded land in Moreland Hills, Ohio, a suburb of Cleveland where development began in 2008. At the end of a new cul-de-sac sits one 4.7-acre lot overlooking the Chagrin River. The site is on a bluff that drops down to the river.
Over the years, active erosion by the Chagrin River resulted in frequent episodic landslides. From 1993 to 2008, approximately 30 feet of ground had been lost as the crest of the slope receded.
The face of the bluff ranged from nearly vertical to steeply sloping as it dropped nearly 100 feet to the river below.

The complexity of the geography, steep slope, and evidence of continuing failures caused by erosion meant a long-term solution to stabilize the slope was a prerequisite to sitting and constructing a home. Site access was severely constrained by the river on the west side and steep-sided wooded ravines to the south and north. Adjacent properties were restricted by conservancy easements and were unavailable for access or staging. These difficulties and costs delayed building on the site.
Various alternatives for stabilization were considered. The final solution consisted of four parts that ranged in complexity. First, flattening the slopes to approximately 2(H):1(V) to establish global stability. Then, the team installed a permanent row of 24" long ground anchors that were installed through a sheet pile and steel whaler system, and the second row of 15 soil nails. Stabilization of the riverbank at the base of the slope to preclude further erosion was then conducted. Finally, the design called for revegetation along the new slope to protect against local erosion caused by heavy rain through native plantings.

 
Cloonan Design Services worked closely with technical teams to develop a solution that would maintain the natural slope and act as a design focal point. The stabilization began at the edge of the slope where concrete pylons and soil nails were added. The infrastructure would assist the overall stability for the top of the slope. Rocks were added for additional support and to add depth to the design approach.

Design Process
The work required approval from multiple agencies. It was engineered and permitted between January 2020 and September 2020 through The Village of Moreland Hills Planning Commission and Building Department, The Ohio Department of Natural Resources, The US Army Corp of Engineers, and Cleveland Metroparks.

Work began in July 2020; it progressed orderly through clearing and mass excavation. Several heavy summer rain events caused severe failures that required re-grading the slope. Sheet pile lagging was placed in September.
The soil anchor drilling and tensioning occurred throughout October and November. In water work, construction began the week after Thanksgiving and was completed by the end of December. The slope was hydro seeded and work was then suspended for the winter. In March 2021, work commenced once again with underground storm and spring water interceptor piping. The slope was fine graded and topsoil and native plant seeds were placed by hand the first week of April. The seeding was immediately covered with approximately 44,000 sq. ft. of High-Performance Turf Reinforcement Mats. This mat is a three-dimensional, lofty, woven polypropylene geotextile designed to control erosion on steep slopes. It requires Percussion Driven Anchors and twist pins to fasten the mats to the ground surface.

By May 1, 2021, after 11 months of planting and securing the hillside, the work was completed. Native trees were added to the landscaped hillside and then it was time to wait and watch the native grasses and wildflowers grow through the mat and turn the slope into a stable, picturesque complement to the river below.

The total scope of the project area was approximately one acre. The design team ended up using about 50 pounds of seed because of the thick matting (the recommended rate was 12-16lbs/acre).

After a year and a half of design and construction on the hillside the native grasses and trees have filled in. Meanwhile, the house is presently under construction, but the pool, spa, and casita have been completed.

The other aspects of the home may take some more time, but the hillside will withstand for many seasons to come due to the anchor reinforced system and vegetation regrowth.

Team List:
Geotechnical Engineer: SME, Cleveland, OH
Civil Engineer: Gutoskey & Associates, Inc., Chagrin Falls, OH
Ecological Consulting Services: Davey Resource Group, Inc., Kent, OH
Hydraulic Modeling & Engineering: GC Engineering, LLC, Sharon Center, OH
Lagging and Soil Anchors: Nicholson Construction Company, Canonsburg, PA
Earthwork & Grading: Independence Excavating, Inc., Independence, OH
Stormwater Piping, Embankment, & Instream: Marks Construction, Inc., Valley City, OH
Landscape Architect & Erosion Control: Cloonan Design Services, Inc., Willoughby, OH