In this study, the Regional Transportation District's (RTD's) light rail operations were examined for pollutant production and runoff. Conclusions from the study: Water leaving ballasted tracks carries only a small fraction of the heavy metals that are introduced into tracks from the light rail operations. Heavy metal concentrations at the most heavily traveled light rail station showed that pollutant concentrations were far below the regulatory limits.
In this study, the Regional Transportation District's (RTD's) light rail tracks were modeled to determine the Rational Method runoff coefficient, C, values corresponding to ballasted tracks. The runoff coefficient for ballasted tracks is significantly larger than the previously tabulated values for railroad yards. The higher runoff coefficient reflects the design of ballasted tracks to drain rainfall as quickly as possible.
Currently, CDOT has no uniform statewide procedure to size detour drainage structures and permanent hydraulic structures using existing methodologies may result in failures. The main objective of the study is to develop a statewide detour drainage structure design procedure that also considers environmental impacts and mitigation measures.
A new service life chart for steel pipes was developed based on the information collected from the field observations and data analysis. Pipe failure criteria were established in accordance with the ongoing culvert evaluation procedure along I-70 and I-25. For the steel pipe failure cases along I-70 and I-25, the previously published service life predictors for steel pipes deviated from observations by as much as 10 times.
HDPE pipes used in CDOT drainage systems are expected to have a 50-year design life. During the T-Rex project in 2003 a number of HDPE pipes were installed with shallow cover. Later, the majority of these pipes had to be removed and replaced after they were damaged by construction equipment driving over installed pipes, and excavations occurring near installed pipes. In this study, performance of HDPE pipes under CDOT highways was evaluated by: an extensive literature review; field studies utilizing manual inspection, CCTV video inspection, and laser-ring profiling technology; and, by observing a CDOT HDPE pipe installation project.
CDOT currently uses FHWA's HEC-18 methods to estimate bridge-pier scour values. The FHWA equations was based largely on streams with uniform sediments, subcritical-flow conditions, and flatter gradients. In western states where many bridges cross steep mountain channels, bridge-scour equations are applied beyond the range of conditions for which they were derived. In this research study, a new bridge pier-scour equation has been developed suitable for streams flowing through mountainous regions of Colorado.
