Resolution - #17-05-121 - 05/23/2017

Home

Our Mission: To work together to resposihly prow our community, and to provide quality, cost-effective. and efficient government services.. CC Regular Session 7. 6. Meeting Date: 05/23/2017 By: Bruce Westby, Engineering/Public Works Information Title: Adopt Resolution #17-05-121 Accepting Quotes and Awarding Contract for Improvement Project #17-11, Ground Penetrating Radar Pavement Evaluations - 2018 & 2019 Reconstruction and Overlay Improvements Purpose/Background: Purpose The purpose of this case is adopt Resolution #17-05-121 accepting quotes and awarding a contract for Improvement Project #17-11, Ground Penetrating Radar Pavement Evaluations for 2017 - 2026 CIP Reconstruction and Overlay Improvements Background: On more than one occasion staff has proposed pavement maintenance improvements to existing streets based on pavement section information found in plans or by examining spot locations of the existing pavement section, only to learn at a later date that the pavement section was not constructed per plan, or that the pavement section was not consistent throughout. The proposed design must then be revised, which in turn delays projects and impacts project costs, as well as proposed assessment amounts. This happened most recently in the Rivers Bend development where a mill and overlay project was proposed for 2017. After soil borings and pavement corings were completed, it was discovered that the pavement was too thin to effectively mill and overlay so the street had to be rescheduled for a reconstruction in 2018. Staff researched available options for evaluating existing pavement section structures and determined that two primary options exist. Staff have typically used soil borings or pavement corings in the past to verify existing pavement sections at numerous locations along street segments. However, a newer technology has emerged in the form of ground penetrating radar. Of these two methods, the ground penetrating radar is significantly cheaper. Ground penetrating radar has been used primarily to locate items buried underground. However, this technology is now being used to evaluate the existing pavement section design in 1 to 2 foot intervals along the entire street, depending on the speed at which the vehicle the radar unit is attached to is traveling. The radar is strong enough to penetrate the top foot or so of the pavement section, revealing changes in material densities between the bituminous or concrete pavement section, the aggregate base section, and subgrade soils. A minimal number of pavement cores are also extracted to calibrate the readings and to verify the specific pavement and aggregate base materials, as well as the subgrade soils. The City has never used ground penetrating radar to evaluate existing pavement sections, whereas soil borings and pavement corings have been used extensively for this purpose. However, staff has found that existing pavement sections on older City streets can vary significantly from location to location. Staff therefore proposes to use ground penetrating radar to evaluate existing pavement sections on all streets proposed to be reconstructed or milled and