Sequence to Phytoreclamation

Technical Note DOER-C9

November 1999

In addition, the group discussed phytoreclamation processes, both published and in study, worthy

of consideration for use in dredged material. It was noted that no single phytoreclamation process

would be the cure-all for all contaminants. Each must be addressed separately. The following two

sections describe the sequence necessary to select a phytoreclamation approach and recommenda-

tions on phytoreclamation processes for specific contaminants. Specific remarks are provided based

on the professional judgment of working group participants. References are cited where provided

in the discussions.

Sequence to Phytoreclamation:

1. Determine Reclamation Goals: If cleanup thresholds are available, the local authority in

which the site is located or where the material will be used if transported offsite will normally

determine reclamation goals or acceptable concentrations in the final soil product.

2. Water Removal: For phytoreclamation of freshly dredged sediment or in a ponded CDF,

removal of water to support establishment of upland plants and other bioreclamation

processes may be required. A number of mechanical approaches for dewatering have proven

effective for CDFs (Headquarters, U.S. Army Corps of Engineers, 1987). Lee et al. (1976)

determined that certain plants can facilitate dewatering and consolidation of fine-grained

dredged material. Transpiration by plants can remove significantly larger quantities of water

than simple evaporation of unvegetated dredged material. Plants that can be easily estab-

lished on loosely consolidated dredged material and have large root systems that will reach

anaerobic zones to facilitate water removal are necessary. Some examples of suitable plants

include Eastern gamma grass and hybrid poplar trees. Selection will be dependent on

specific needs. Under certain conditions, anaerobic dredged material may be blended with

cellulose and biosolids to produce a manufactured soil product. The resulting soil product

will have less free water and is ready for immediate establishment of plants for the

phytoreclamation process.

3. Selection of Plants to Achieve Goals: The cleanup goals of each contaminant will drive

the selection of a phytoreclamation process. Goals may be based on a soil concentration

threshold or a bioavailability threshold. In situations where two or more contaminants

require some form of reduction, phytoreclamation may have to occur sequentially or

concurrently with other phytoreclamation, bioreclamation, or chemoreclamation processes.

Phytoreclamation processes that are known or suspected to have effective results are

discussed in the following sections by contaminant class.

4. Screening and Quantification Testing: It will be necessary in most cases with dredged

material to conduct tests in controlled greenhouse environments to determine the plant

growth response to dredged material and/or manufactured soil. Sturgis and Lee (1999)

describe the manufactured soil screening test to determine blends of dredged material,

cellulose, and biosolids most suitable for plant growth. The effectiveness of a phytorecla-

mation process should be evaluated prior to initiation of a field-scale demonstration,

particularly where little information is known about the effectiveness of a particular

phytoreclamation process on dredged material or manufactured soil. Due to the small

volume of soil material used in the manufactured soil screening test, it is not suitable to