The City of Beech Grove, Indiana, located on the south side of Indianapolis, had some serious erosion issues in Sarah Bolton Park. Erosion of Lick Creek through the park was raising concerns of threating the roadway, eroding the foundation of an existing power pole, exposing a sewer line and losing three large trees. To find solutions to their problem, Beech Grove hired United Consulting to survey & permit the project and Christopher Burke Engineering for the design.
Three cross sections were developed at the project site. The determining factor on the type of cross section utilized along the bank was the available horizontal space to the soon-to-be protected obstruction. Erosion began downstream of a concrete bridge and continued for 750’. The furthest downstream cross section incorporated a vegetated soil confinement wall, GeoWeb, to protect the power pole from relocation. Above the wall, a permanent turf mat, North American Green SC-250, was used to protect the seeded area till germination and strengthen the vegetation during flood overtopping. The opposing side the creek had an already constructed gabion wall. The gabion baskets were repaired with new PVC coated galvanized steel baskets and live staked to increase vegetation.
Once past the power pole, the cross section could be slightly modified with the GeoWeb wall to lessen the steepness of the cross section. It should be noted that around the power pole a modified wall design was used. Helical anchors were used to reinforce the gravity wall to decrease the cut into the slope minimizing any impacts to the power pole.
Eventually, Christopher Burke was able to lay the slope back for a gentler cross section approaching the bridge while protecting the sewer line, tree roots and roadways. Due to the erodible soils, GeoWeb was once again used; however as a surface applied product in this cross section. A 12” diameter, 9 lbs/ft3 density pre-vegetated coir log was placed at the Ordinary High Water Mark (OHWM) to assist in establishing the vegetation at this vulnerable location. The same permanent turf mat, North American Green SC-250, was used on top of the surface applied GeoWeb to increase the shear stress capacity of the system. Note the SC-250 was below the coir log, continued up the slope to the top of bank. The Parks Department was very specific on the types of plants to be incorporated into the design. As such, D2 worked with the Parks Department to pre-vegetate the coir logs appropriately and provide a seed mixture.
Next to the bridge, Christopher Burke was able to transition to the bridge with articulated concrete block mat, which was consistent with the existing design.
The project was an overall success and D2 will continue to monitor the site through the upcoming years.
