Area Flood Assessment

Pinnacle Engineering was retained by a rail client to analyze approximately 29 miles of mainline track adjacent to a major river system which had experienced a significant number of washouts during extreme flooding in 2011.  A majority of the rail line was in a remote area, and survey and flood data were not readily available.  Analysis was required as quickly as possible so that new, properly sized culverts could be installed as rail roadbeds were repaired and similar damage in future flooding events could be avoided.

Pinnacle engineers provided hydraulic analysis, surveying, GIS mapping, regulatory representation, environmental analyses, and environmental permitting.  The hydraulic analysis report covered six bridges and approximately 25 culverts, The Pinnacle team adapted LIDAR (aerial topography) data from the County to create a track profile map of the 29-mile stretch which included survey data, elevations of culverts and bridges, and an analysis of water levels during the 2011 event.

Upon completion of a revised flood study, additional work was scheduled, enabling Pinnacle’s client to adjust bridge heights to avoid future damage from 100-year event floods.

Hydrologic Assessment

Pinnacle Engineering was retained by a rail client to investigate complaints by a City and an area farmer whose land flooded following heavy rainfall in the summer of 2010. The City and farmer believed the flooding was caused by inadequate drainage capacity through two culverts on railroad property:  an old cast concrete arch culvert running parallel to the rail client’s tracks and passing under a County Road; and a steel culvert leading from the city into a State Highway ditch and passing under the client’s tracks.  Pinnacle’s client did not want to install additional culverts if they were not needed.

Pinnacle Engineering personnel conducted a site inspection and found that, although the farmer’s (and adjacent) property had seen only minor changes in the preceding 25 years, the farmer’s land and that of several nearby residents had experienced severe flooding in 2010.  Pinnacle’s investigation also revealed that (1) the culvert that passed under the County Road had partially collapsed, reducing culvert capacity and (2) the adjacent State Highway had recently been reconstructed and that water appeared to be standing on the downstream side of the railroad’s culvert in the new highway ditch.

Pinnacle performed an engineering analysis, prepared a report of its findings, and worked closely with the rail client, County Engineers, City personnel, and area residents to find an acceptable solution for all.

Because the partially collapsed cast concrete culvert passed underneath a County Road, the County Engineer agreed to assume responsibility for replacing and thereafter maintaining the culvert. 

Pinnacle determined through a hydraulic analysis that the steel culvert leading into the State Highway ditch was properly sized.  However, the Iowa  Department of Transportation’s reconstruction of the paralleling State Highway had not provided adequate ditch grade, and this (rather than an inadequately sized culvert) had caused an excessive tail-water and flooding to the City and the farmer’s land following excessive rainfall.

We need to add something about how this was resolved.  Did the DOT accept this finding?  Did they change the ditch grade? The original description just says we sent them a letter.

webpagespacer.png

Hydraulic Analysis

Pinnacle Engineering was retained by a rail client to provide hydraulic analysis of an area which was flooded following extreme rainfall events in 2011.  Heavy rains, combined with over-topping of an area reservoir, flooded the client’s mainline track and caused a washout and subsequent train derailment adjacent to a National Wildlife Refuge.

After environmental clean-up and restoration work concluded, Pinnacle surveyed the area and prepared a hydraulic analysis of various alternatives to prevent future washouts and minimize downtime for the railroad, replicating the extreme 2011 rainfall events. To accomplish this, the Pinnacle team provided hydraulic analysis, survey, civil design environmental assessment, regulatory representation, and permitting services.

Ultimately, Pinnacle engineers designed a channel that bypasses the existing serpentine channel during major water flow events, rather than increasing the sizes of existing culverts or constructing box culverts to handle increased water flow. Once water flow returns to normal rates, the slow-moving stream returns to the existing channel.