CLOSURE CONCEPTS FOR HART-MILLER ISLAND DREDGED MATERIAL CONTAINMENT FACILITY

摘要

Construction of the Hart-Miller Island (HMI) dredged material containment facility was completed in 1984. The facility was designed to safely contain dredged material from Baltimore Harbor shipping channels and berthing areas. The approximately 445-hectare (1100-acre) site is divided into two cells, the North Cell, 324 hectare (800 acres) and South Cell, 121 hectare (300 acres). In 1990, dredged material placement ceased in the South Cell and it lay idle for about eleven years. From 2002 to 2006, the South Cell underwent an environmental restoration project. Currently, the South Cell serves to provide valuable habitat to a large number of resident and migrating bird species, including some on the Maryland State rare, threatened, and endangered species list.The State of Maryland passed legislation that requires final closure of HMI with transfer of property and management to the Maryland Department of Natural Resources (DNR). Closure will begin after filling of the site with dredged material ceases at the end of 2009. However, before the HMI facility can be transferred to DNR, the Maryland Port Administration (MPA) intends to close the facility according to the site's master plan, which specifies that HMI shall be restored to provide valuable wildlife habitat and public opportunities for passive recreation.There are numerous challenges in closing a site like HMI; a relatively large flat site, fine-grained sediments that exhibit low strengths, estuarine sediments high in sulfide that can acidify and mobilize heavy metals and little precedent to use as guidance. Consequently, the MPA commissioned a study team to develop a variety of closure concepts ranging from completely flooded to mostly uplands. This paper summarizes the significant findings and recommendations of the HMI north cell closure study team and provides much insight into the development of a highly complex set of design requirements for closure of this type of facility.