Project Overview
Originally built in 1874, the dam spanning the San Marcos River in Luling, Texas, now complements the Zedler Mill complex―a 9.32-acre tranquil getaway popular with locals and tourists alike. The facility was experiencing bank erosion from increasingly severe and frequent flood and storm events. PND created a 380-foot bank-stabilization retaining wall upstream of the dam to protect the historic site. The client ultimately selected PND’s OPEN CELL SHEET PILE™ (OCSP™) system as the most versatile and cost-effective solution over several other retaining wall options. The OCSP wall’s design addressed shallow bedrock and rehabilitated the site to its pre-erosion state. While dewatering the project area or using cofferdams for dry construction were not feasible, the OCSP solution could be constructed with the river at normal levels with minimal risk of flood damage.
Upon construction completion in 2020, PND’s OCSP wall restored Zedler Mill’s crumbling bank, provided durable protection from future flood events, and enhanced the beauty of the park at the San Marcos River’s edge for years to come.
Our Role
- Coastal Engineering: used an OCSP™ system to protect an eroding river bank, accommodating shallow bedrock and eliminating the need for dewatering or cofferdams
- Waterfront Engineering: created an OCSP™ wall to upgrade the park at the Zedler Mill facility
Shoring Up a Historic Riverbank with Thoughtful Design
The site’s topography proved challenging, as the shallow bedrock steeply sloping up from the river bottom prevented driving sheet piles deep enough for a cantilevered or tieback wall. However, the OCSP™ wall relies on anchoring in the soils behind the wall rather than requiring toe embedment or support from soils in front of the wall. In some instances, rock was pre-drilled or excavated to achieve the minimum depth.
The complex wall geometry of the OCSP™ required minimal excavation to follow the historic riverbank’s alignment. The flexibility of the OCSP™ also allowed horizontal and vertical adjustments during construction, now providing earth retention and erosion protection along the river. As waterways across the nation are subjected to more severe and frequent flood and storm events, PND’s creative OCSP™ system offers quick, effective, and sustainable solutions for waterway resilience.
“This project was a success due to the innovative OCSP™ system and the dedicated work of PND to adjust the design to site conditions. The project restored the city’s lost bank and enhanced the aesthetics of the park.”
