Milwaukee DMMF—Tandem Sheet Pile Containment, Design, and Construction

Milwaukee Metropolitan Sewerage District (MMSD) has initiated the Milwaukee Estuary Dredged Material Management Facility (DMMF) project to provide disposal capacity for 1.9 million cu yd (1.4 million m3) of contaminated spoils to be dredged from the Milwaukee, Menomonee, and Kinnickinnic Rivers and Milwaukee Bay. Though DMMFs typically use earthen dikes for material containment, Milwaukee DMMF uses tandem combi-wall structures on the waterside perimeter instead. It is the second such facility to be constructed in the Great Lakes. Ensuring the stability of the containment necessitated innovative practices for analyzing tandem bulkhead structures, where parallel rows of sheet piling form a relatively narrow containment for earth fill between, with significant structure-soil-structure interaction between the two walls. Despite this increasingly common wall configuration, there is limited technical literature available. Consequentially, the design team used finite element techniques to analyze this structure. This paper discusses the planning, design, and sequence of construction for the tandem combi-wall containment structures.