Johnston Construction Co.

Owner:

Howard County, Maryland

General Contractor:

ADI Limited

Scope Of Work

Johnston Construction Company provided construction services for modifications to the existing wastewater treatment plant for this $1,390,000 design-build subcontract for the treatment of wastewater from the Dreyer’s ice cream plant in Savage, MD that is part of Dreyer’s Grand Ice Cream, Inc.

The project involved site demolition and excavation activities plus the construction of concrete structures and mechanical process equipment. Demolition of the existing abandoned structures was followed by excavation to prepare the sub-grade for pre-cast concrete tanks and cast-in-place concrete structures. Construction was provided for the cast-in-place concrete structures to house the process equipment and the installation of all mechanical process equipment.

Site excavation, concrete and mechanical construction were key components of the project. Excavation was on a compressed three month time schedule and the discovery of unsuitable sub-grade soil conditions required the redesign of the limits of excavation. About 3,000 cubic yards of soil were excavated for the project and another 800 cubic yards of unsuitable soil had to be removed. Concrete work involved the construction of a 20’ x 18’ x 12’ tall reinforced concrete base structure for the bio-gas waste flare. A 20’ x 20’ x 4’ high reinforced concrete containment tank for chemical storage was also constructed using the Symons Steel-Ply form system. Mechanical installation included the fabrication and installation of over 400 lineal feet of welded 6-inch diameter stainless steel pipe (above and below ground), setting and trimming out a 5 million BTU, 12,000 pound boiler, and a 35 foot tall, 4,500 pound flare.

Certain issues required actions to meet the construction schedule. With the discovery of unsuitable soils on the site, the excavation subcontractor had the necessary equipment to move large quantities of earth within the compressed time schedule. The prefabrication of the welded stainless steel process piping for the project was required due to the tight construction schedule. Coordination with the piping vendor was critical to assure that prefabricated assemblies could be final fit and assembled on site that resulted in great success to meet the substantial completion deadline.

The project was started in January 2007. Final construction and performance testing was completed in January 2008.