vvEPA
United States
Environmental Protection
Agency
Best Practices for Identifying
Reference Condition in
Mid-Atlantic Streams
REFERENCE CONDITION CONCEPT
The Clean Water Act (CWA) poses significant
challenges to states and tribes charged with
evaluating whether aquatic resources under their
management achieve the biological integrity
objective and the "protection and propagation" goals.
One of the critical challenges is the development of
a standard or benchmark by which to judge whether
particular water bodies are in accordance with the
CWA objective and goals. The concept of a reference
condition and its implementation form the foundation
on which to make such judgments (Stoddard et al.
2006a)
Reference conditions have been applied at site-
specific and regional scales. Regional reference
condition, described here, is recommended to support
biological criteria. Biological criteria are used to
detect deviation from reference condition to determine
whether water bodies meet their water quality
standards. The Biological Condition Gradient (BCG) is
a scientific narrative model for interpreting biological
response to increasing effects of stress on aquatic
ecosystems. The BCG describes how attributes of aquatic
ecosystems change in response to increasing levels of
human disturbance (Fig. 1, Davies and Jackson 2006).
States in the Mid-Atlantic region have developed and
implemented the concept of reference condition in a
variety of ways to meet their individual needs, without
comprehensive guidance from EPA.This brochure
offers examples from these states as case studies in the
application of the reference condition concept in water
resource management.
Level of Exposure to Stressors
Natural structure, functional, and taxonomic
integrity is preserved
Structure & function similar to natural community
with some additional taxa & biomass; ecosystem
level functions are fully maintained
Evident changes in structure due to loss of some
rare native taxa, shifts in relative abundance;
ecosystem fnctions fully maintained
Moderate changes in stucture due to replacement
of sensiti ve ubiquitous taxa by more tolerant taxa;
ecosystem functions largely maintained
Sensitive taxa markedly diminished conspicuously
unbalanced distribution of major taxonomic groups;
ecosystem function shows reduced complexity &
redundancy
Extreme changes in structure and ecosystem
function; wholesale changes in taxonomic
composition; extreme alterations from normal
densities
Watershed, habitat, flow regime and
water chemistry as naturally occurs.
Chemistry, habitat, and/or flow regime
severely altered from natural conditions.
Figure 1. The Biological Condition Gradient (BCG) is a tool for developing more precise aquatic life uses. The BCG displays six
positions of biological condition along a stressor-response curve, with Position 1 exhibiting the least stress and highest quality
condition, and Position 6 representing the greatest stress and lowest quality. (Modified from EPA 2005)
-------
TYPES OF REFERENCE CONDITION
The term reference condition can have multiple meanings.Therefore, consistent and specified
definitions of reference condition can greatly enhance collaboration among states and the transfer
of best practice technology and expertise. In all cases, reference condition is the benchmark
against which changes in current biological conditions are evaluated.The following definitions
distinguish among four specified types of reference condition:
Reference Condition for Biological Integrity, RC(BI): the natural biological condition of
a water body, undisturbed by human activity. As a conceptual aid, it is useful to think of an
absolute "natural" or pristine condition that could exist in the absence of all historical and
current human disturbances. This definition recognizes the need for a reference condition term
reserved for"naturalness"or"biological integrity"even though we might only approximate it in
most parts of the world.
Minimally Disturbed Condition, MDC: the
biological condition found in water bodies in
landscapes with minimum human disturbance.
Places that meet the criteria for RC(BI) are
rare or impossible to find. Human activity is
present throughout the global ecosystem,
affecting remote systems through long-range
atmospheric transport and deposition of
pollutants onto pristine landscapes. Biological
integrity in places with a low amount of human
activity might not be significantly affected.The
phrase"minimally disturbed condition"describes
photo credit: wayne Davis the biological condition in places with a minimal
Figure 2. A Mid-Atlantic stream displaying physical amount of human disturbance.
attributes suggestive of minimally disturbed condition.
Least Disturbed Condition, LDC: in altered landscapes, the biological condition found in
water bodies with the least amount of human disturbance compared to similar water bodies
in the region of interest. There is a clear need to describe the best condition of water bodies in
landscapes that have been moderately to heavily disturbed by human activities. Definitions like
"minimally disturbed condition" are of little practical use in these situations. Therefore, the phrase
"least disturbed condition" has been applied to describe the condition in water bodies that are the
least disturbed in a landscape altered by significant human activity. LDC should not be used as a
benchmark for biological integrity. Further, in certain severely altered landscapes, LDC may not
even be useful as a benchmark for meeting CWA aquatic life use protection and propagation goals.
Best Potential Condition, BPC: the highest possible biological condition deemed achievable
through the implementation of best management practices and other rehabilitation activities
that can be undertaken in a given landscape given social and economic considerations. In some
circumstances, a condition could be achieved that is better than the least disturbed condition (i.e.,
better than the condition at the best sites) with implementation of the best available practices
to remove or minimize stressors. Even though the biological potential might approach biological
integrity if the stressors are removed, societal/economic constraints typically mean that a condition
is achieved that differs from biological integrity. The term "best potential condition" describes
this condition, where the biological expectations are set somewhere between the least disturbed
condition and biological integrity.
-------
APPROACHES TO DERIVING REFERENCE CONDITION
Ideally, every water body segment will have its own reference condition. In order to describe reference
condition in a way that will not change over time due to further human activity, several general methods have
been developed through practical experience. These methods include sampling the biota at sites with little
or no indication of stressors associated with human disturbance (i.e., minimally disturbed reference sites).
In altered landscapes, where such sites are few or absent, reference conditions are determined through a
combination of methods: (1) sampling biota from least disturbed sites (reference sites), (2) interpreting
historical records to deduce which biological characteristics occurred at times with substantially less human
disturbance, (3) developing models that incorporate the best ecological knowledge, and (4) using best
professional judgment.
1. Reference Sites
The selection and characterization of reference
sites that are minimally or not disturbed by human
activities have been the basis for defining reference
conditions that approximate biological integrity.
However, reference sites have also been identified
as "the best of what's left" and as such are used to
estimate a least disturbed condition. The approach
used to select reference sites may be similar, regardless
of whether the sites are classified as minimally
disturbed or least disturbed. The process and
considerations involved in selecting reference sites is
discussed in further detail in the following pages.
2. Historical Reconstruction
The role of historical reconstruction is to use available
data to describe a range of water body or riparian
conditions that existed at an earlier time. Historical
reconstruction estimates a minimally disturbed
condition rather than a least disturbed condition.
Benefits of this approach include the following:
• Improving the characterization obtained from
reference sites;
• Needing to be generated only once;
• Providing a permanent benchmark;
• Allowing for a more cost-effective approach than
extensive sampling; and,
• Providing motivation to stakeholders as a vision of
desirable conditions.
3. Empirical modeling
When the number of representative reference sites
is low and historical information is not sufficient
to reconstruct reference condition, predictive
modeling can be used to construct and calibrate a
model reference condition.This approach effectively
leverages a smaller number of sites from the region
or water body type than is needed for the typical
spatially intensive reference site approach. However,
it does require reliable data from representative sites.
Absent such data, this approach reverts to a best
professional judgment approach with its inherent
shortcomings of subjectivity. This approach is
limited also by the data used in the model, and
therefore, inferences beyond those data must be
undertaken with great caution.
Predictive modeling approaches that show promise
include the following:
• Extension of reference site results from
adjacent regions or similar water body types;
• Application of stressor-biotic assemblage
interactions identified in restoration
experiments; and,
• Inclusion of extirpated species or exclusion of
nonnative species.
Photo credit: Morris Perot
Figure 3. Biologists conducting a physical habitat
assessment at an unnamed tributary in Frederick
County, MD.
-------
4. Best Professional Judgment
Best professional judgment (BPJ) should
be incorporated into all decisions; however,
comparisons with a stressor gradient are also
needed to accurately identify the position of the
reference sites. The natural variability in biological
attributes for a certain biological condition (e.g.,
biological integrity) dictates that biological data
alone should not be used to develop reference
conditions. Although BPJ is a critical part of
biological assessments, great care must be taken
to ensure that the development of reference
conditions and selection of reference sites are well
documented and include objective procedures that
can be reproduced easily by others.
SELECTING REFERENCE SITES
Selecting reference sites involves applying
screening criteria to a set of sites from the region
or water body type of interest. These criteria will
identify sites that are most likely to be minimally
or least disturbed by human activities. The result
is a set of candidate reference sites, qualified as
such because depending upon the protectiveness
that the screening criteria represents, some of
the sites selected may not represent the desired
reference condition (Fig. 4).
Criteria useful for screening sites include stressors,
indicators of stressor sources, and indicators
along the pathway from source to exposure. The
goal is to evaluate as many of these indicators as
is practical, efficient, and relevant to the water
body type and region of interest. Only those sites
that meet the criteria of minimal disturbance or
those that are the least disturbed among the set
of sites are considered candidate reference sites.
Applying Reference Screening Criteria
Screening criteria should apply to potential
reference sites at three levels: landscape or
watershed, reach or riparian corridor, and
site. While watershed and reach scale analysis
using maps and/or CIS technology can identify
candidate reference areas, there are many human
activities that can only be revealed by collecting
data at the site level. However, it is essential that
the final list of candidate sites identified through
this screening be evaluated against an objective set of stressor thresholds obtained from sampling
data. Brief descriptions of the Mid-Atlantic Highlands Streams Assessment and the Maryland
Biological Stream Survey illustrate approaches to reference site selection using objective criteria.
Having too few reference sites to analyze each region or water body type is a common constraint
in indicator development and may lead to relaxation of reference site criteria to obtain more sites.
Developing Reference Condition
Using Reference Sites
ALL SITES
Applying Initial Screening Criteria
Important consideration: Coarseness of filter
CANDIDATE REFERENCE SITES
Evaluating Quality and Representativeness
Important consideration: Readjustment of filter's codrseness
REFERENCE SITES
for Reference Condition
Applying Final Screening Criteria
Importdnt consideration: Codrseness of filter; Reference site vdridPility
?EFERENCE CONDITI
for Biocriteria
Figure 4. This schematic shows the steps involved in
developing reference condition using reference sites. At
each step, it is important to consider the coarseness of
the filter, which influences the confidence that the quality
of the reference sites accurately represents the intended
quality of the reference condition.
-------
Prior to the Mid-Atlantic Highlands Streams
Assessment (MAHSA; Davis and Scott 2000), a
precedent for using objective, abiotic criteria for
identifying reference sites in the region had not
yet been set. MAHSA biologists anticipated that
the probabililty-based design would generate
too few candidate reference sites, and therefore
asked local resource managers to "hand-pick"
sites in order to augment the spectrum of
conditions. All sites sampled-including those
selected via BPJ-were subjected to objective,
abiotic criteria (below) representing potential
disturbance activities including acid rain,
acid mine drainage, agriculture, and general
development. Sites were considered candidate
reference sites if they met these criteria:
• acid neutralizing capacity (ANC) > 50 ueq/L
(pH of about 6)
• sulfate (SO4) < 400 ueq/L
• total phosphorus (P) < 20 ug/L
• total nitrogen (N) < 750 ug/L
• chloride (CIO < 100 ueq/L
• mean Rapid Bioassessment Protocol (RBP)
habitat score > 15
Application of the objective screening filter to
the 58 BPJ sites resulted in only 15 sites (26%)
meeting the reference site criteria. This study
established the need to support the application
of objective, abiotic screening criteria for
candidate reference sites regardless of the
method used to select sites.
The Maryland Biological Stream Survey (MBSS)
is an example of a probability-based stream
monitoring program that successfully uses
objective criteria for sampled sites to identify
reference conditions (Klauda et al. 1998).
Because the program samples approximately
300 sites per year, data are available from
all regions and stream types. No screening
was done to narrow the range of candidate
reference sites, so all sampled sites were
evaluated using the following criteria of water
chemistry, physical habitat, and land use stress
(Roth et al. 1998). To develop the Maryland fish
index of biological integrity (IBI), the MBSS
used these criteria to identify 152 of the total
1098 sites (13.8%) as reference sites:
• pH >6 or blackwater stream (pH < 6 and
DOC >8 mg/L)
• ANC >50 ueq/L
• dissolved oxygen >.4 ppm
• nitrate <300 ueq/L (4.2 mg/L)
• urban land use ^20% of the catchment area
(draining to the site)
• forest land use >;25% of the catchment area
• remoteness rating = optimal or suboptimal
(>1 Don 0-20scale)
• aesthetics rating = optimal or suboptimal
• instream habitat rating = optimal or
suboptimal
• riparian buffer width >.15 m
• no channelization
• no point source discharges
The development of a fish IBI for MAHSA (Davis and Scott 2000) addressed this situation by evaluating metric
performance against three different reference definitions: (1) least restrictive criteria based on chemical
thresholds and the mean RBP habitat score (producing 46 reference sites with good geographic coverage); (2)
moderately restrictive criteria based on chemical criteria, watershed land use, road density, and quantitative
habitat filters (producing 23 reference sites with good geographic coverage); and (3) most restrictive criteria
based on the moderately restrictive criteria plus the watershed condition class (Bryce et al. 1999; producing
12 reference sites with limited geographic coverage). If less restrictive criteria are used to define reference
sites, then the lower quality may result in conditions that correspond to lower positions along the Biological
Condition Gradient (e.g., Position 3 rather than 2, in Fig. 1).
Evaluating Quality and Representativeness
Because reference criteria vary among water quality monitoring programs, it is essential to evaluate the
selected reference sites for whether they are truly minimally disturbed and whether they are representative of
the water bodies of interest.
The Maryland Biological Stream Survey used a set of water chemistry, physical habitat, and land use reference
criteria that produced reference sites with considerably higher benthic macroinvertebrate IBIs than all sites
-------
sampled and were also higher than the original MBSS set
of reference sites (see dashed line in Fig. 5). Subsequently,
the reference criteria used in the original MBSS IBIs
were reviewed to identify changes that would result in
greater confidence that the new reference sites could
be defined as "minimally disturbed." Based on analysis of
urban effects on stream condition (V0lstad et al. 2003),
the presence of original reference sites with relatively
high levels of urban land (i.e., 5% to 20%) indicated that
not all reference sites were minimally disturbed; instead,
many were impaired.Therefore, the MBSS changed the
minimum allowable forested land use from >25% to
>35% of the catchment area, maximum allowable urban
land use from ^20% to ^5%, and minimum allowable
riparian buffer from 15m to 30m. These changes in land
use and riparian width thresholds resulted in a smaller
proportion of stream sites meeting the reference site
criteria. Using the original reference site criteria, 152
of the 1098 Round One sites (14%) were designated as
reference sites. Using the new criteria, 196 of the total
2508 sites (8%) were designated as reference. These new
reference sites were of higher quality (dotted line in Fig.
5) than sites meeting the original reference criteria. This
result is consistent with greater confidence that the sites
are minimally disturbed.
As the criteria for selecting reference sites are
tightened to ensure minimally disturbed sites are
chosen, it is important that these sites still represent
the range of natural factors likely to control the
biotic composition in the region of interest. For
example, stream size, gradient, and elevation can be
SETTING BENCHMARKS FOR REFERENCE CONDITION
The most common approach for using reference sites to set attainment benchmarks is to select a percentile
of the reference site index scores below which is considered degraded. As previously discussed, the selec-
tion of the percentile should consider the coarseness, or restrictiveness, of the screening criteria. In the Mid-
Atlantic Region, West Virginia sets a benchmark at the 5th percentile of the reference sites; Maryland uses
the 9th percentile; Virginia uses the 10th percentile; and EPA's Mid-Atlantic Integrated Assessment (MAIA)
uses the 25th percentile. In addition to percentile selection, the West Virginia Department of Environmental
Protection (WVDEP), the Maryland Department of the Environment (MDE), and the Virginia Department of
Environmental Quality (VDEQ) also include separate measures of index precision surrounding the bench-
mark in order to capture uncertainty for regulatory program use. These programs demonstrate innovative
approaches for setting attainment benchmarks, as well as recommended practices for defining and imple-
menting reference condition.
WVSCI Scoring Criteria
>68.0
Unimpaired
> 60.6 to 68
"Gray Zone"
Figure 6. The West Virginia Stream
Condition Index (WVSCI) has a precision
estimate of 7.4 units. Therefore, setting
the benchmark at a score of 68 (the 5th
percentile) effectively creates a "gray zone"
between 68 and 60.6. (WVDEP 2006)
West Virginia Benchmark
West Virginia DEP set a low benchmark (at the 5th percen-
tile) because their screening criteria included a secondary
review of the candidate reference sites that passed the ini-
tial objective screening criteria (akin to the evaluation step
in Fig. 4). Using BPJ in the secondary review, the number of
sites dropped from 349 candidate reference sites to 216 ref-
erence sites (Southerland 2006).The BPJ included a review
of each candidate site for its proximity to upstream point
source discharges and an evaluation of anthropogenic ac-
tivities and disturbances near the candidate sites. For their
stream condition index (SCI), WVDEP (2006) determined a
precision estimate of 7.4 out of 100 units. This uncertainty
in the index itself sets the 5th percentile benchmark of 68
effectively to 60.6, the range between those values being in
a "gray zone" (Fig. 6).
-------
major determinants of potential biotic composition.
Therefore the set of reference sites should cover
and be limited to the range of natural conditions
important in the region of interest. If the streams
represent an elevation gradient, reference sites should
also represent that elevation gradient; if streams
considered represent a range of sizes, the set of
reference sites should also represent these sizes.
2.00 3,00 4.00 5.00
Figure 5. Cumulative distribution of stream miles with benthic
macroinvertebrate IBI scores for (1) MBSS sites sampled in
2000-2004 (solid line), (2) subset of 2000-2004 sites meet-
ing original reference criteria (dashed line), and (3) subset of
2000-2004 sites meeting new reference criteria (dotted line).
(Southerland et al. 2005)
Virginia Benchmark
Virginia DEQ (2006) sets the attainment benchmark at the
10th percentile of their reference sites. Much like West
Virginia, the precision estimate for Virginia's stream condi-
tion index (VSCI) is ±7.9, which generates a "gray zone"
around the benchmark. As a result, the 10th percentile
benchmark of 60 effectively becomes a range from 55 to
63, where sites scoring above 63 are viewed as healthy
streams and those below 55 are deemed moderately to
severely stressed.
Maryland Benchmark
The Maryland Department of Natural Resources did
not establish a specific benchmark based on a distribu-
tion of their reference sites. They maintain a categori-
cal index score rating similar to the metric scoring
procedure of 1,3 and 5, where any score above 3 is
considered acceptable. To facilitate the use of the
Maryland IBIs for the regulatory agency, a statistical
measure of uncertainty (confidence interval) is used
to determine whether the mean of the results from
the sites sampled in a watershed is above or below the
Index of Biotic Integrity (IBI) value considered indica-
tive of satisfactory water quality (i.e., 3). Where at least
ten sites have been sampled in a watershed, watershed-
specific confidence intervals are calculated. If the
upper bound of the confidence interval is less than 3,
that watershed is designated as not meeting water qual-
ity criteria (MDE 2004). For comparison with other
states' methods, it was determined that the MDE index
benchmark of 3 was equivalent to the 9th percentile of
the reference sites (Southerland 2006).
Mid-Atlantic Integrated Assessment Benchmark
For a report card on the state of streams and rivers
in the Mid-Atlantic region, data was combined from
two sample surveys conducted in the region by
MAIA from 1993 to 1998 (Stoddard et al. 2006b).
MAIA established two benchmarks based on the
distribution of reference sites. The 25th percentile
value set the lower limit on "good" condition. The
1 st percentile was used as the threshold below which
values were deemed "poor."Values between the 1st
and 25th percentiles were designated as "marginal."
These classifications were deliberately used so as not
to conflict with regulatory terms used by the States
(Fig. 7).
100
90
Reference Distribution
80
o
o
C/D
X
0)
70
60
50
40
Percentiles:
o 99th
T 95th
75th
50th
25th
1
| 5th
0 -|St
Good
1
Marginal
T
Poor
i
Figure 7. The two benchmarks set by MAIA
established three categories of condition: poor,
marginal and good. (Stoddard et al. 2006b)
-------
Office of Environmental Information
Washington DC 20460
EPA-260-F-06-002
August 2006
CONTACTS
Office of Environmental Information
Wayne Davis
davis.wayne@epa.gov
Office of Water
Evan Hornig
hornig.evan@epa.gov
Office of Research and Development
John Stoddard
stoddard.john@epa.gov
REFERENCES
Bryce, S.A., DP. Larsen, R.M. Hughes, and P.R. Kaufmann.
1999. Assessing relative risks to aquatic ecosystems: A Mid-
Appalachian case study. Journal of American Water Resources
Association. 35:23-36.
Davies, S.P. and S.K.Jackson. 2006. The biological condition
gradient: a descriptive model for interpreting change in
aquatic ecosystems. Ecological Applications 16(4):1251-1266
Davis, W.S., and J. Scott. 2000. Mid-Atlantic Highlands Streams
Assessment: Technical support document. EPA-903-B-00-
004. U.S. Environmental Protection Agency, Region 3, Office
of Research and Development, Ft. Meade, MD. Available at:
http://www.epa.gov/bioindicators/html/publications.html
Klauda, R., P. Kazyak, S. Stranko, M. Southerland, N. Roth, and J.
Chaillou. 1998.The Maryland Biological Stream Survey: A state
agency program to assess the impact of anthropogenic stresses on stream habitat quality and biota. Third EMAP Symposium,
Albany, NY. Environmental Monitoring and Assessment 51:299-316.
Maryland Department of the Environment (MDE). 2004. 2004 List of impaired surface waters [303(d) List] and integrated
assessment of water quality in Maryland. Appendix C Listing Methodologies. Maryland Department of the Environment,
Baltimore, MD. Available at http://www.mde.state.md.us/assets/document/AppndxC2004-303d_Final.pdf
Roth, N.E., M.T. Southerland, J.C. Chaillou, R.J. Klauda, P.P. Kazyak, S.A. Stranko, S.B. Weisberg, LW. Hall, Jr., and R.P.
Morgan II. 1998. Maryland Biological Stream Survey: Development of a fish index of biotic integrity. Environmental
Management and Assessment 51:89-106.
Stoddard, J.L., D.P. Larsen, C.P. Hawkins, R.K. Johnson and R.H. Norris. 2006a. Setting expectations for the ecological
condition of streams: the concept of reference condition. Ecological Applications 16(4):1267-1276.
Stoddard, J.L, A.T. Herlihy, B.H. Hill, R.M. Hughes, P.R. Kaufmann, D.J. Klemm, J.M. Lazorchak, F.H. McCormick, D.V. Peck, S.G.
Paulsen, A.R. Olsen, D.P. LarsenJ.Van Sickle, and T.R.Whittier. 2006b. Mid-Atlantic Integrated Assessment (MAIA): State of
the flowing waters report. EPA-620-12-06-001. U.S. Environmental Protection Agency, Office of Research and Development,
Washington, DC. February 2006. Available at: http://www.epa.gov/bioindicators/html/publications.html
Southerland, M.T., G.M. Rogers, MJ. Kline, R.P. Morgan, D.M. Boward, P.F. Kazyak, RJ. Klauda, and S.A. Stranko. 2005.
New biological indicators to better assess the condition of Maryland streams. CBWP-MANTA-EA-05-13. Report for the
Maryland Department of Natural Resources, Annapolis, MD.
Southerland, M.,J.H.V0lstad, L. Erb, E.Weber, and G. Rogers. 2006. Proof of concept for integrating bioassessment results
from three state probabilistic monitoring programs. EPA-903-R-05-003. U.S. Environmental Protection Agency, Office of
Environmental Information and Mid-Atlantic Integrated Assessment Program, Ft. Meade, MD. Available at: http://www.epa.
gov/bioindicators/html/publications.html
U.S. Environmental Protection Agency (EPA). 2005. Use of biological information to better define designated aquatic life uses
in state and tribal WQS: Tiered aquatic life uses. EPA-822-R-05-001. U.S. Environmental Protection Agency, Office of Water,
Washington, DC. Available at: http://www.epa.gov/bioindicators/html/publications.html
Virginia Department of Environmental Quality (VDEQ). 2006. Using probabilistic monitoring data to validate the Non-
Coastal Virginia stream condition index. VDEQ Technical Bulletin WQA/2006-001. Richmond, VA. Available at: http://
www.deq.virginia.gov/probmon/pdf/scival.pdf
V0lstad,J.H., N.E. Roth, M.T. Southerland, and G. Mercuric. 2003. Pilot study for Montgomery County and Maryland DNRdata
integration: Comparison of benthic macroinvertebrate sampling protocols for freshwater streams. EPA-903-R-03-005. U.S.
Environmental Protection Agency, Office of Environmental Information and Mid-Atlantic Integrated Assessment, Fort Meade,
MD. Available at: http://www.epa.gov/bioindicators/html/publications.html
West Virginia Department of Environmental Protection (WVDEP). 2006. West Virginia 2006 Section 303(d) List, updated
3/22/2006. Available at http://www.dep.state.wv.us/show_blob.cfm?ID=10203&Name=303(d)_Listing_Rationale_Only.
pdf
Recycled /Recyclable
Printed with Vegetable Oil Based Inks on 100%
Post-consumer Process Chlorine Free Recycled Paper
------- |