Structural Preservation Systems (SPS) was hired to complete an underground culvert repair and slab remediation at the Rockland Plaza shopping center located in Nanuet, New York. The floorless pile-supported culvert beneath the plaza and parking lot was subject to erosion, causing sinkholes to form beyond the culvert walls, as well as localized deterioration of certain areas of the culvert. SPS worked with McClaren Engineering to develop repair solutions, most of which were performed in low headroom and confined space conditions.

To repair the deterioration of the culvert and surrounding areas, the team first filled geotextile mattresses with cement grout, placing them along the bottom of the culvert. This required extensive preparation of the rubble culvert floor. Approximately 375 cubic yards of grout was injected into the geotextile mattresses, covering 1,200 linear feet of the culvert floor. Following this, the team performed localized concrete wall repairs, utilizing reinforced shotcrete. After the interior tunnel work was completed, voids in the soil along the outside of the walls were filled with low mobility grout from the surface through vertical grout pipes.

During the culvert repair, an adjacent structure required foundation strengthening. The solution involved transforming an existing slab-on-grade into a structural slab supported by 30 micropiles. SPS used a specialized electric low-headroom drill rig to install the piles. Each 5 ½ inch diameter steel pile was pressure grouted in the bond length, approximately 50 feet deep. The existing slab was removed and replaced with a reinforced structural slab.

Despite the tight working conditions, including low headroom and confined spaces, all repairs were completed safely and successfully. Work on this project began in November 2006 and was completed in February 2007.