The TIRZ 17 Redevelopment Authority (Tax Increment Reinvestment Zone Number Seventeen also known as the Memorial City Redevelopment Authority) is a local government corporation created to aid, assist and act on behalf of the City of Houston, Texas. Its mandate is to promote the common good and general welfare in the Memorial City area of Houston through investment in public infrastructure. Roadway and drainage improvements in this growing area of the City are of particular interest to the corporation. In the fall of 2014, the Memorial City Redevelopment Authority accepted bids for the reconstruction of Lumpkin Road between Westview Drive and Northbrook Drive.

The proposed improvements included the reconstruction of the existing Lumpkin Road with new concrete pavement, installation of new waterlines, storm sewer and sanitary sewer along Lumpkin Road and the widening and deepening of an existing storm water detention pond located at the northwest corner of the intersection of Westview Drive and Lumpkin Road.

The proposed redevelopment plan called for the existing L-shaped detention pond to be widened and deepened by 5 feet increasing its maximum depth to approximately 19 feet. The proposed grading for the new detention pond required the construction of over 22,000 square feet of retaining walls. To accomplish the required grade separation and transition, the City selected the Redi-Rock precast modular block retaining wall system with 9-inch setback units (0.52H:1V face batter). This particular precast modular block wall system was selected based upon its ability to be designed as a gravity wall system that would not require external geosynthetic soil reinforcement.

Used predominately in extreme height applications where the retaining wall is founded in competent bedrock, the 9-inch setback Redi-Rock wall system would need to be designed to meet some fairly significant structural challenges. Ultimately, the retaining walls would be required to support the reconstructed portion of Lumpkin Road and provide a very tall gravity wall solution in existing soils consisting of stiff to hard sandy clay and clayey sands. Regrettably, all the soil test borings completed in the vicinity of the proposed detention pond improvement were advanced to a depth of 40 feet without encountering rock.

Serving as the engineer of record for the retaining wall design-build team, JC Hines and Associates prepared sealed construction shop drawings for the six (6) interconnected retaining wall segments. The final design for the walls expanded slightly on the scope of a cement-stabilized sand foundation soil improvement recommended by the owner’s geotechnical engineer and incorporated recycled crushed concrete aggregate as structural backfill for all the retaining walls. The result was an optimized retaining wall solution that included fundamental elements of sustainable design and delivered cost effective earth retention structures for a difficult site.

The Redi-Rock retaining wall units were manufactured by Wilbert Vaults of Houston in Houston, Texas.