The City of Longview is replacing an aging 8 foot by 5 foot box culvert located in the center of a 60-foot wide median. Gibbs & Olson was recently hired to provide the planning, permitting, land surveying, design and construction phase services to replace the box culvert system. The project is approximately 2,600 linear feet and the total drainage basin collected by the existing box culvert is approximately 220 acres. Stormwater enters the box culvert from the contributing drainage area at numerous locations. The stormwater is collected at each intersection along Beech Street and is also collected in small branches consisting of 1 to 3 inlets that are directly connected through the side wall of the culvert with 8 inch concrete pipe. In addition, there are six larger collection system at various locations.
The current box culvert discharges to an existing 42 inch aluminum stormwater trunk line and outfalls into CDID Ditch 1. There is an overflow from one of box culvert which outfalls to CDID Ditch 3. Discharge to this overflow occurs when the water level in the box culvert is greater than one foot in depth.