Texas Contractor's Material and Test Certification for Underground Piping is an important document that must be filled out and submitted to the State of Texas in order to perform excavations and install underground piping. This document is designed to provide proof that the contractor is using materials that meet the standards established by the State of Texas for underground piping. There are two types of Texas Contractor's Material and Test Certification for Underground Piping: Type I and Type II. Type I certification is for contractors installing thermoplastic piping, while Type II is for contractors installing all other types of piping, such as metallic, concrete, or cast iron. The certification documents must include a description of the pipe material and test results, as well as the contractor's signature.