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Title: Confined disposal area effluent and leachate control (laboratory and field investigations)
Authors: Chen, Kenneth Y.
Mang, James L. (James LaVern)
Eichenberger, Bert
Hoeppel, Ronald E.
Keywords: Soils--Leaching
Water quality
Dredging spoil
Dredged material
Waste disposal sites
Publisher: U.S. Army Engineer Waterways Experiment Station
Series/Report no.: Technical Report (Dredged Material Research Program (U.S.)) ; no. DS-78-7
Abstract: This report summarizes the findings of five work units concerned with the impact of dredged material disposal in confined land disposal areas. Three of the work units dealt with active disposal operations at 11 sites; impact was assessed by comparing the quality of influents and effluents at each site with background surface receiving water. Two work units are discussed which evaluated the impact of confined disposal area leachates on groundwaters. The leachate studies included laboratory column elutions (3- to 9-month period) of each of five types of dredged material overlying one of two different soils; four of the 11 field sites were also monitored for changes in leachate and groundwater quality (four onsite, four offsite monitoring, and two offsite background sampling locations at each site) in a 9-month study. The field sites included freshwater (riverine and lake) and brackish water (estuarine and ship channel) dredging environments located in geographical areas where contamination problems were anticipated. The dredged material and environmental features varied greatly at the different sites. Data from the active disposal studies showed that in most cases soluble concentrations of most chemical constituents were very low. Only soluble manganese and ammonia nitrogen levels failed to meet most criteria. The concentrations of chlorinated hydrocarbons, most trace metals, and total phosphorus in unfiltered effluent water also failed to meet most water quality criteria. Thus, it appears that efficient removal of suspended solids before effluent discharge is necessary to meet these regulatory guidelines. The presence of thick, actively growing vegetation in disposal areas seemed to improve the removal of suspended solids and soluble nutrients (ammonium nitrogen and soluble phosphorus). Salinity levels in effluents from saline dredged material disposal sites should impact low-salinity receiving waters. The leachate studies suggest that the disposal of brackish water dredged material in upland disposal areas may render subsurface water unsuitable for public water supply or irrigation purposes. Leachates from both the freshwater and brackish water disposal sites usually contained levels of ammonia nitrogen, iron, and manganese that exceeded drinking water standards. The freshwater site also contained an average nitrate nitrogen level that exceeded guidelines. Leachate data from background and offsite monitoring wells showed that high levels of some chemical constituents, especially iron and manganese, were governed by local environmental conditions (i.e. Eh and pH) present in the surrounding soils. This strongly suggests that the physical and chemical properties of the soils underlying a prospective site be considered in context with the nature of the dredged material. It is suggested that guidelines for evaluation of potential disposal sites be developed in a stepwise progression that will not require complete execution of the total program to determine site suitability. A short discussion of an evaluatory scheme is included.
Description: Technical Report
Gov't Doc #: Technical Report DS-78-7
Rights: Approved for Public Release; Distribution is Unlimited
Appears in Collections:Technical Report

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