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3rd AMIREG International Conference (2009): Assessing the Footprint of 78
Resource Utilization and Hazardous Waste Management, Athens, Greece
Criteria for beneficial utilization of dredge sediments in Virginia, USA
W. Lee Daniels, A. Wick and N. Haus
Virginia Tech, Blacksburg, Virginia, USA
G.R. Whittecar
Old Dominion University, Norfolk, Virginia, USA
C. Carter III
Weanack Land LLLP, Charles City, Virginia, USA
ABSTRACT
Upland placement of dredge sediments is fa-
vored over bulk disposal options in the USA for
many projects where contaminant levels meet
beneficial utilization standards. Since 2001, we
have placed over 350,000 m3 of fresh water
dredge materials (Woodrow Wilson Bridge Pro-
ject -WWB) and 250,000 m3 of saline materials
from the Earle Naval Weapons Station (N.J.)
into monitored upland placement cells and
documented their conversion to agricultural
uses. Detailed groundwater and soil quality
monitoring has indicated no adverse effects
from material placement and outstanding agri-
cultural productivity for the freshwater WWB
materials. Our combined experience to date in-
dicates that an important primary screening pa-
rameter is acid-base accounting which should
become a mandatory analytical requirement.
Our second level of screening is based upon a
combination of USEPA risk-based soil screen-
ing levels and related New Jersey standards.
High silt+clay and TOC may also eliminate
many dredge materials for physical and logisti-
cal reasons. This new dredge material screening
system separates potential upland placement
candidates into two quality levels with differing
management and monitoring requirements. Fi-
nally, it is also clear that whenever dredge mate-
rials from a saline environment are utilized for
upland placement, that salinity and Na will limit
plant productivity and soil quality for some pe-
riod of time, and that appropriate management
practices and/or extended leaching intervals will
be necessary.
1. INTRODUCTION
River and harbor dredging activities generate
hundreds of millions of m3 of dredge materials
in the eastern USA annually, and disposal op-
tions are becoming increasing limited and ex-
pensive. While certain sediments are heavily
contaminated (USEPA, 2005), much of the ma-
terial is quite suitable for placement into upland
environments for conversion to topsoiling mate-
rials for mining and other disturbed sites (Dar-
mody and Marlin, 2002; Darmody et al., 2004;
Lee, 2001). The basic chemical and physical
properties of these dredge sediments vary
widely based on their depositional environment
and watershed characteristics and history. For
example, exposure and weathering of highly
sulfidic dredge sediments produces extremely
acid soil conditions and metal release (Fanning
and Fanning, 1989), while any materials re-
moved from marine or brackish environments
will necessarily contain entrained salts and Na
that will need to be leached before their conver-
sion into viable topsoiling materials. Similarly,
dredge materials that are too high in fine
silt+clay and organic matter may be difficult to
handle, place and till in an upland environment.
However, large volumes of non-sulfidic poten-
tially suitable materials are routinely dredged
and disposed of annually, and the federal Inter-
agency National Dredging Team (USEPA,
2003) has placed a high priority on moving suit-
able materials to upland beneficial use environ-
ments rather than into disposal impoundments.
In this paper we will review results obtained
from two large upland dredge placement pro-
jects in Virginia and summarize our new regula-
3rd AMIREG International Conference (2009): Assessing the Footprint of 79
Resource Utilization and Hazardous Waste Management, Athens, Greece
tory proposal for the screening and classifica-
tion of dredge materials for upland placement
and agricultural use.
2. THE WOODROW WILSON BRIDGE PRO-
JECT WITH FRESHWATER SEDIMENT
The construction of the Woodrow Wilson
Bridge (WWB) replacement spans across the
Potomac River just south of Washington D.C.
excavated approximately 500,000 m3 of fresh-
water tidal dredge sediments between 2000 and
2005. Extensive pre-excavation testing indicated
that the sediments were very low in organic
contaminants and metals, relatively low in or-
ganic matter (< 5% TOC), loam to silt loam in
texture, and moderate in pH. All pesticides, her-
bicides, and other anthropogenic organic com-
pounds were either non-detectable or well be-
low USEPA Region 3 Risk Based Criteria for
residential soils (Daniels et al., 2007)
Weanack LLLP worked cooperatively with
Virginia Tech, Old Dominion University, and
Potomac Crossing Consultants to develop an
upland beneficial use permit structure to use
these materials to construct an agricultural soil
landscape on former sand and gravel mined
lands adjacent to Shirley Plantation in Charles
City County, Virginia. The majority of materials
were moved by barge to Weanack in 2000 and
2001 and then off-loaded at its port facility with
a clamshell loader into haulers. The materials
were then placed into the 20 ha utilization cell
(Fig. 1) and allowed to dewater and consolidate.
The upland utilization cell was on a former sand
& gravel mine. The pre-existing mine soils were
cut out to enlarge the capacity of the area and
the cut spoils were used to construct a 3 to 6 m
dike around the facility to avoid any loss of
sediments to surface waters during operations.
2.1 Agricultural Soil Development
The fresh dredge materials were approximately
35 to 45% solids when placed in 2000 through
2002 and were highly reduced and anaerobic
(Fig. 1). Over the course of one year, however,
the materials stabilized and settled to some ex-
tent, and deep polygonal cracking was observed.
The polygons were initially 20 to 50 cm in di-
ameter at the surface, the cracks were 2 to 8 cm
wide, and > 25 cm deep by the summer of 2002.
Observations in the fall of 2002 indicated that
the material was oxidized along cracks to a
depth of > 50 cm, but reduced materials within
polygon/prism centers were observed at 25 cm.
We excavated several soil pits in 2002 (see
Fig. 2) and the surface layer was clearly becom-
ing more uniformly oxidized with time and the
surface became better aggregated. Auger bor-
ings also revealed relatively unconsolidated
“soupy” materials that occurred at 2.0 m+ that
were still strongly reduced and low chroma
(blue-gray color). Total subsidence of the re-
Figure 2: Profile of oxidizing dredge soil in April 2002,
less than 18 months after placement.
Figure 1: Placement of WWB dredge spoil on old sand
and gravel mined lands.
3rd AMIREG International Conference (2009): Assessing the Footprint of 80
Resource Utilization and Hazardous Waste Management, Athens, Greece
search plot area is estimated to be 10 to 15% (of
originally placed 5 to 7 m of dredge) to date,
and further settlement is expected over time
once these deeper layers dewater and consoli-
date fully. Despite the significant oxidation of
reduced Fe and Mn species, the pH of the sur-
face layers has remained > 6.5 to date at all lo-
cations and averaged > 7.0. The inbound dredge
sediments had an average calcium carbonate
equivalence of > 2.5% and were very low in sul-
fides, so this outcome was expected.
2.2 Crop Production Trials
By the fall of 2001, the sediments had dewa-
tered, cured and oxidized sufficiently to allow
for cultivation (Fig. 3). Between 2002 and 2005,
a series of row crop production trials was estab-
lished and run in a replicated design that is de-
scribed fully by Daniels et al. (2007).
The row crop trial plots received varying
rates of yardwaste compost addition and very
minimal applications of P and K fertilizers be-
tween 2002 and 2005. No lime or N additions
were made. Corn (Zea mays L.) yields are pre-
sented in Table 1. Simply put, the corn yields
recorded on the dredge spoil materials in 2002
were outstanding. This region suffered a severe
regional drought in 2002, although a few sum-
mer thunderstorms did provide adequate mois-
ture at critical times for ear filling and grain de-
velopment. Apparently, the corn was able to
root down through the dewatering dredge spoils
(through the deep desiccation cracks discussed
earlier) to tap into the wetter dredge materials at
depth.
While corn grain yield did appear to increase
with compost loading rate up to 112 Mg/ha,
within-plot variability was high, and no signifi-
cant compost rate effects were noted. However,
even the 0 compost treatment yields were well
above any 2002 yields on surrounding farms
that we queried. In contrast to 2002, 2003 was
an exceedingly wet year, and we believe that
contributed to overall yields being lower than
the high yields observed in 2002 (Table 1). It is
also important to note that we added no N-
fertilizer to these plots, even though the heavy
crop the preceding year certainly extracted large
amounts of plant available N. Nitrogen avail-
ability is generally the major predictor of corn
yield when rainfall is not limited, so we are
quite impressed by this overall yield response,
particularly from the 0 compost control plots.
The lower yield at the highest compost loading
rate was most likely related to excess moisture
holding in the very large amount of organic
matter added. Crop yields in 2004 through 2008
on the WWB materials were consistently higher
than local county average yields for prime farm-
lands.
2.3 WWB Summary Conclusions
Based upon these documented chemical, physi-
cal and morphological properties, and the com-
bined crop yield data, we are convinced that
these newly deposited “dredge soils” may be as
productive as any natural soils in the region.
From a narrow standpoint of bulk soil chemical
properties and fertility, these newly developed
soils are outstanding and actually superior to
most native agricultural soils. The pH of the sur-
face soil ranges from 6.8 to 7.4, despite over
five years of oxidation and weathering. Thus, on
a net basis, this project replaced low productiv-
ity reclaimed mined lands with high productiv-
ity prime farmland.
Figure 3: Row crop production trial plot area in the fall of
2001. Multiple crops of wheat and corn were established
and grown through 2006.
Table 1: Corn yield in September 2002 and 2003 at
Shirley Plantation/Weanack. kg/ha Treatment
Compost Mg/ha 2002 2003
0 13,090 a 7,350 a
56 15,820 a 7,910 a
112 16,100 a 7,910 a
224 13,790 a 8,190 a
336 14,630 a 4,900 b
*Yields in a given year followed by different letters are
significantly different at p < 0.05).
3rd AMIREG International Conference (2009): Assessing the Footprint of 81
Resource Utilization and Hazardous Waste Management, Athens, Greece
3. EARLE SALTWATER SEDIMENTS
In 2005 and 2006, approximately 250,000 m3 of
saline dredge materials from the Earle Naval
Weapons Station (N.J.) were placed into a new
upland placement cell directly to the east of the
WWB materials. These materials were placed
over eroded low productivity farmland and con-
tained within a 2.5 to 4 m high dike and moni-
tored over time to document their conversion to
agricultural use. The Earle sediments contained
several PAH’s (e.g. Benzo(a)pyrene) slightly
above USEPA residential use standards and
were higher in TOC and silt+clay than the
WWB sediments. Full characterization data on
these materials are provided in Daniels and
Whittecar (2006). As expected, relative to the
WWB sediments, the rapid conversion of these
materials to agriculture has been limited by en-
trained salts (Cl and SO4) and Na. Regardless,
approximately 60% of the sediment surface was
supporting vigorous vegetation by mid-2009
and certain areas were supporting agricultural
crops. Current studies are detailing salt leaching
rates within and under the dewatering sediments
and effects of sand, topsoil and compost
amendments.
4. SULFIDES, TEXTURE AND CARBON
Due to the well publicized success of the WWB
sediment project, we were asked to review, test
and consider many (10+) differing fresh- and
saltwater dredge materials for inclusion in our
cooperative upland placement program. The
typical analytical package provided to us in-
cludes total metals, nutrients, herbi-
cides+pesticides and a wide range of organics
(e.g. PAHs, PCBs and Dioxins). However, we
are convinced that the most essential analysis
that must be conducted on all materials is a sim-
ple acid-base accounting for acid-forming po-
tential similar to that utilized by the mining in-
dustry. Of the 15+ materials that we have tested
to date, over 50% have sufficient reactive sul-
fide content vs. net neutralizers that we have re-
jected them from consideration for upland use.
Typically, these acid-forming materials would
require at least 30 Mg/ha of lime additions per
15 cm depth to neutralize their acid loadings to
allow for crop production. Further oxidation be-
neath the limed zone would lead to significant
water quality degradation. One alternative solu-
tion would be to bulk mix agricultural limestone
with the inbound sediments (e.g. at 1.5 to 2.5%
by weight) but this cost would need to be ac-
counted for and the logistics of this process with
wet/soupy sediments are challenging.
The beneficial use potential of any given
sediment for agricultural uses is also directly
limited by particle size and organic C content.
In general, when the silt+clay content exceeds
70%, the materials will be very difficult to man-
age from a tillage perspective, regardless of
their bulk chemical properties. Similarly, when
the total organic C (TOC) content exceeds 5 to
10% (depending on texture), short-term dewa-
tering is complicated and physical ripening
processes are greatly slowed.
5. PROPOSED DREDGE SEDIMENT CLAS-
SIFICATION FRAMEWORK
In association with the work described above,
we have focused a large collective effort on de-
veloping a better working knowledge of the ap-
proaches used by other USA states and federal
agencies for screening sediments and solid
wastes for upland use. As a result of these com-
bined efforts, we have developed a proposed set
of sediment screening criteria which are based
on a combination of (A) soil screening levels
used by USEPA (2008) for setting cleanup lev-
els for contaminated sites, (B) upland dredge
spoil placement criteria developed by the New
Jersey Department of Environmental Protection
(1997), and (C) modifications by our group to
account for agronomic plant growth needs and
certain nonsensical standards as discussed be-
low. This classification system has been pro-
posed to the Virginia Department of Environ-
mental Quality for adoption. An example of our
system is presented in Table 2 which is drawn
from a full spreadsheet that specifies a range of
classification levels for over 130 different pa-
rameters. The base document is an Excel
spreadsheet that allows for entry of sample
characterization data into appropriate review
fields with instructions for the proposer to
bold/highlight all exceedances.
This proposed system is unique in that it pro-
poses two tiers of acceptable materials with dif-
ferent levels of permitting, management and
monitoring requirements. The left-hand column
3rd AMIREG International Conference (2009): Assessing the Footprint of 82
Resource Utilization and Hazardous Waste Management, Athens, Greece
in Table 2 lists screening levels that we propose
to be used to separate “clean fill” from material
with moderate levels of contaminants. From a
regulatory perspective, we propose that these
materials should be released for upland use
without intensive soil and groundwater monitor-
ing requirements once the material properties
had been confirmed via inbound sediment sam-
pling and analysis. However, site placement
mapping and minimum fill location require-
ments would need to be documented for these
materials. The middle column in Table 2 con-
tains what we consider to be “exclusion criteria”
where one or more exceedances (of average
characterization values) would prevent upland
utilization. The right-hand column in Table 2
lists the current USEPA Region 3 risk-based
soil screening levels which are intended for use
in contaminated site cleanup. However, they are
often utilized by state agencies and consultants
as generic screening criteria for other applica-
tions.
The various screening levels given in Table 2
were originally developed from human health
risk assessment protocols that may be quite in-
appropriate for the intended uses discussed here.
For example, the USEPA industrial site soil
screening level for As is 1.6 mg/kg (Table 2)
while the normal background As level in native
Virginia soils is approximately 5.0 mg/kg
(Smith et al., 2005). Use of this standard for
screening dredge materials is therefore clearly
inappropriate and nonsensical. Similarly, the
USEPA screening level for Zn is 310,000 mg/kg
since Zn is not particularly toxic when in-
gested/inhaled by humans at target doses. How-
ever, Zn at these levels in soils could be phyto-
toxic at soil pH levels < 7.5, and we therefore
have adjusted the Zn screening levels for our
system based on agronomic and soil literature.
In addition to the conventional screening cri-
teria presented in the large table, we are also re-
quiring that all proposed sediments be carefully
screened for acid production potential, soluble
salts and other properties such as texture and
TOC. Based on our collective experience in this
area since 2001, it is obvious that a number of
materials that will be proposed and available for
upland placement are going to fall somewhere
between our “clean fill” and “exclusion” criteria
as explained above. These materials should con-
tinue to be regulated via a site-specific permit
with soil and water quality monitoring criteria
tailored to the nature of the inbound sediments
and the characteristics of the utilization site.
6. CONCLUSIONS
Upland placement of dredge sediments offers
great potential to improve land use potentials on
formerly mined and degraded lands with an as-
sociated economic return to landowners. All
dredge materials need to be rigorously screened
for acid-forming potential in addition to conven-
tional chemical and physical quality criteria.
Freshwater dredge materials are generally better
candidates for upland utilization than saline ma-
terials, but saline materials can be effectively
managed over longer timeframes. The new clas-
sification system proposed here could signifi-
cantly improve the review, permitting and over-
all environmental compliance process for these
unique materials.
REFERENCES
Daniels, W.L. and G.R. Whittecar, 2006. Annual Moni-
toring Report - 2005 - Weanack Dredge Spoil Utiliza-
tion. Submitted to Va DEQ and PCC 2/15/2006.
Available at: http://www.cses.vt.edu/ revegeta-
tion/dredgemanu.html.
Daniels, W.L., G.R. Whittecar and C.H. Carter, 2007.
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Darmody, R.G. and J.C. Marlin, 2002. Sediments and
Table 2: Selected examples of proposed screening limits
for beneficial upland use of dredge sediments. These are
drawn from a full spreadsheet list of > 130 parameters.
Exclude
Clean Fill Limit EPA* Parameter mg/kg
Metals
As 20 40 1.6
Pb 300 800 400
Zn 1500 7500 310,000
Organics
Total PCBs 0.49 25.2 25.2
BAP** 0.21 0.66 0.21
4,4'-DDT 2.0 7.0 7.0
*USEPA 2008 Region 3 Risk Based Criteria for industrial
uses.
** Benzo(a)pyrene
3rd AMIREG International Conference (2009): Assessing the Footprint of 83
Resource Utilization and Hazardous Waste Management, Athens, Greece
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