Matrix was selected as one of two consultants to establish an inventory of all minor structures within the City of Boulder. This was the City’s initial inspection of their minor structures to ensure the safety and function of bridge infrastructure and to comply with the requirements of the National Bridge Inspection Standards (NBIS), Code of Federal Regulations 23 CFR 650C. The NBIS regulation recommends each bridge with public access that has an opening between four and 20 feet be inventoried and inspected at regular intervals, not to exceed 48 months.

The City of Boulder covers over 25 square miles along the base of the Rocky Mountains, Northwest of Denver, CO. Matrix inventoried and inspected 76 minor structures throughout the City limits. The structures varied from precast and cast-in-place box culverts, reinforced concrete pipe culverts, corrugated metal pipe culverts, steel truss pedestrian bridges, timber beam vehicular bridges, concrete arch bridge and prestressed concrete beam bridges. Many of the structures had been constructed prior to 1940 based on the exposed steel reinforcing.

The inspection procedure required all structures to be visually inspected from underneath, within, and above to identify all defects. Areas of visible defects were further tested using non-destructive testing methods, such as sounding concrete to determine if any delamination of concrete and steel was occurring. All major structural components were measured, photographed, and documented to allow for a Structural Inventory and Appraisal (SI&A) form to be completed for each structure. All structural elements were coded according to the National Bridge Inventory Coding Guide and Colorado Department of Transportation Coding Guide to help establish the overall condition of the structures. When desired by the City, load ratings were performed on vehicular structures to determine structural capacity.