Danville Levee Improvements

Larson Design Group (LDG) provided survey, design, bidding support, and construction administration for improvements in support of the FEMA certification of 6,100 linear feet of levee along Hospital Run and the Susquehanna River in Danville, Montour County, Pennsylvania. As a result of Tropical Storm Lee in September of 2011, FEMA increased the base floodwater surface elevations between 0.3 to 0.4 feet. The increase mandated a new levee certification to account for the higher surface elevations and to ensure a sufficient amount of freeboard, or the portion of the levee above the floodwater.

For the survey and design portion of the project LDG completed a topographic survey of the levee crest, landside embankment, and 15 additional feet from embankment toe. LDG also conducted a site visit and confirmed a previously completed survey of the levee, noting any evidence of erosion, sloughing, rodent damage, and potential utility conflicts. The initial review of the levee sections that needed to be raised indicated that most of the improvements could be made without requiring work on the levee embankment. The sections included two stoplog structures. In situations where the required fill could not be completed within the existing minimum levee width of 10 feet, additional fill needed to be placed on the levee’s landside embankment. LDG identified existing property lines to determine if the fill would remain within the levee property, if the borough needed to acquire additional right-of-way, or if alternate levee raising designs needed to be considered. LDG prepared construction details and typical cross sections for the levee modifications in accordance with FEMA and PADEP requirements. LDG coordinated with the stoplog manufacturer to develop plans for extending those structures and provided construction details with the final plans. LDG also provided details on the required revisions to all the headwalls and inlets that need to be raised.

The bidding and construction administration support included preparing the bid advertisements, maintaining a log of plan holders, preparing clarifications to questions, responding to requests for information, issuing addenda, attending the bid opening, reviewing the provided bids, preparing bid tabulations, assisting the borough in the bid evaluation, periodic site visits, and performing final inspections to verify the completion of construction and any necessary punch-list items. LDG also verified that the closeout documents provided by the contractor were complete and accurate.