The Franklin Street Reservoir was constructed in 1938 below a city park to store and provide fresh drinking water to residents. The concrete reservoir has a capacity of 16 million gallons and consists of two chambers, each with capacity for 8 million gallons, separated by a common concrete divider wall. The original construction incorporated construction materials now considered health hazards and the structure was experiencing concrete deterioration and waterproofing failures. Walker developed a repair program for removal and abatement of hazardous waterproofing materials and replacement with materials suitable for contact with potable water, repair of deteriorated concrete and replacement of structural expansion joints to extend the service life of the structure.
Due to the collapse of several wood porch structures, the City of Chicago developed minimum design guidelines for wood deck/porch structures constructed within the City. Many of the University buildings have multi-level wood framed porches. To meet the University’s proactive approach to safety and maintenance, Walker performs annual inspections of the wood structures for deficiencies which could affect the structural integrity of the structure or conditions which could result in safety concerns. Recent changes in pressure-treatment chemicals for decay resistance of lumber have also resulted in premature deterioration of standard hardware in wood structure construction. This has made it necessary to change the hardware and fasteners to galvanized or stainless to prevent premature deterioration.
The City of Grand Rapids B-Section primary settling tanks were constructed in 1954 as part of a multi-stage clarification system for wastewater from multiple municipalities in the Grand Rapids area. The structure consists of four circular tanks separated by concrete divider walls. The structure was experiencing corrosion and concrete deterioration from de-icing salts which had caused significant damage to the structure. Additionally, the supported slab over the influent and effluent channels exhibited severe stages of deterioration. Walker performed a comprehensive assessment of the structure to determine the location and extent of damages and developed a repair program for re-construction of supported slabs over the channels, installation of protective coatings on the reinforcing steel, and installation of new PVC coated conduits embedded into the concrete for power and controls of mechanical process equipment. The repairs addressed the current deterioration and provided enhancements to extend the life of the structure.
The City of Grand Rapids C & D Section primary clarifier tanks were constructed in the late 1970’s to process an average of 40 million gallons per day. The structure exhibited deficiencies including leaking tunnels from cracks in the concrete walls, failing mechanical process equipment and ponding water which was causing slip hazards in the winter when the water froze. Walker designed waterproofing and structure repairs to address current deterioration and mitigate future deterioration to protect and extend the life of these critical assets.
The Primary Effluent Retention Basin (PERB) was constructed in the 1970’s to hold up to 10 million gallons of overflow and contaminated wastewater during large storm events prior to the City’s separation of storm and wastewater. Deteriorating sealants and degradation of the wash down cannon system resulted in soils contamination and erosion of the tank sub-soils. Walker performed a detailed assessment of the structure and developed a repair program for replacement of the tank sealants, removal and replacement of concrete panels to allow replacement and consolidation of eroded soils, and replacement of the wash down cannon system to extend the useful fife of the structure.
Cooling towers are subject to constant and/or intermittent exposure to moisture. As a result, these structures are susceptible to corrosion-induced deterioration and freeze-thaw damages creating potentially hazardous conditions to the users and to the equipment.
Cooling towers require routine inspection to ensure safe operation of the structure, as well as long-term durability. Inspections are carried out by Licensed Engineers to identify imminently hazardous conditions, maintenance items, and other structural concerns such as cracks, moisture penetration through the shell (i.e., efflorescence), deteriorated packing material, and deteriorated concrete. Additionally, inspections can identify unsafe conditions at access stairs, walkways, and handrails.
Investigation methods for cooling tower inspections come in two forms: visual examination and physical examination. A visual examination of readily accessible areas is the primary investigation method when performing a cooling tower inspection. These areas include the upper and lower ring beams of the cooling tower, the internal and external faces of the concrete shell, the columns, walls, and fill packing material and supports at the basin, as well as the access stairs, basin walkways, and the top level handrails. Remote access surveys performed via an unmanned aerial vehicle mounted (UAV) with a video and/or photographic camera can be utilized in areas which may not be readily accessible or areas requiring more close-up documentation.
Physical examinations are performed when moderate to severe deterioration is observed in the structure. This includes, widespread rust stains, delamination, as well as spalled concrete in the shell and base columns. Physical examinations are typically up-close assessments performed via scaffold or lift access and can include destructive and/or non-destructive testing.