CLE Engineering was retained by Omega Demolition to perform pre- and post-demolition surveys in support of the Whittier Bridge replacement project. These surveys were done to the specifications dictated by the USACE and the Massachusetts DPW. The purpose of this survey was to develop a post-demolition grade based on existing condi-tions adjacent to the abutments that were to be removed. This survey was performed in an active con-struction site with barges, falsework, and sheet pile coffer-dams.
CLE navigated through the obstructions to generate the required data. The Merrimack River is an extremely fast moving river, with tidal influences. Surveys were planned to take advantage of tidal lags in order to generate accurate survey deliverables. Obstructed views of the sky prevent proper GPS positioning, this is overcome with the use of inertial positioning. Inertial positioning blends GPS positions with positions calculated using vessel accel-erations eliminating outages caused by overhead obstructions. Deliverables for the project included bathymetric data and integrated existing and design profiles.