Chemical Contaminants

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Chesapeake Bay Program Indicator Framework

Reporting Level Indicators

Indicator and Data Survey

A.  Category/Name/Source/Contact

(1) Category of Indicator

___ Factors Impacting Bay and Watershed Health

___ Restoration and Protection Efforts

___ Watershed Health

_x Bay Health

(2) Name of Indicator:

Percent of Tidal Tributaries without Partial or River-wide Impairments Due to Chemical Contaminants. (As determined by Virginia, Maryland, and DC under Clean Water Act requirements)

(3) Description of Dataset used to calculate percent of goal achieved:

For what purpose(s) were the data collected? (e.g., tracking, research, or long-term monitoring.)

Monitoring.  Data was collected by MDE and VA DEQ, and DC for the purpose of identifying waters with fish tissue contamination at levels requiring Clean Water Act 303(d) listing.

Which parameters were measured directly? Which were obtained by calculation

Data was obtained from 303(d) lists for MD, VA, D.C., and EPA

Concentrations of contaminants in tissue of collected fish were measured by VA DEQ and MDE these are the primary source of PCB related impairments.  A variety of other methods are used to determine impairments by states.  Those exceeding the state’s thresholds or determined impaired using other methods were included in the CWA 303(d) listings for MD, VA, and DC.

This indicator calculates the number of impaired segments as a percentage of the total number of tidal segments considered.  The result is an indicator value that is a calculated percentage based on states’ criteria.

(4) Source(s) of Data:

Is the complete data set accessible, including metadata, data-dictionaries and embedded definitions?  If yes, please indicate where complete dataset can be obtained.

Yes, data was obtained from DC, MD and VA 303(d) lists and supporting data for these lists.  D.C.’s draft list of impairments is provided through the District of Columbia Department of the Environment (DDOE). 

Maryland’s 303(d) list is available through the Maryland Department of the Environment (MDE), Virginia’s is available though the Virginia Department of Environmental Quality (VADEQ). Supporting data was provided by contacts in both state departments. 

A description of methodology is provided by the states: 



(5) Custodian of Source Data (and Indicator, if different):

Source data: MDE, VADEQ, DDOE

Indicator: Water Quality Goal Implementation Team

(6) CBPO Contact:

Greg Allen, Karey Harris

B.  Communication Questions

(complete either part 1, 2, or 3)

1.  Restoration and Protection Efforts indicators only

(7a) How much has been completed since 1985 (or baseline year)?  How much has been completed since 2000?

(8a) How much was done last year?

(9a) What is the current status in relation to a goal?

(10a) What is the key story told by this indicator?

(11a) Why is it important to report this information?

(12a) What detail and/or diagnostic indicators are related to this reporting level indicator? (Detail and diagnostic indicators can be spatially-specific, parameter-specific, temporally-specific information, etc.)

2.  Bay Health or Watershed Health indicators only

(7b) What is the long-term trend?  (since start of data collection) 

N/A.  Can only compare the 2006 and 2008 303d assessments by DC, MD and VA (see below for short-term trend). 303(d) lists are updated every-other year, and will not be updated again until 2010.

 (8b) What is the short-term trend? (10 year trend)

N/A.  Can only compare the 2006 and 2008 303d assessments by DC, MD and VA.  In 2008, 28.1% of tidal tributaries were unimpaired, down from 33.7% in 2006.  303(d) lists are updated every-other year, and will not be updated again until 2010.

(9b) What is the current status in relation to a goal?

Currently less than 30% of the tidal waters considered contain no impairment for chemical contaminants.  The goal is for 100% of segments considered to contain no impairments due to toxic chemicals.

(10b) What is the key story told by this indicator?

Over two thirds of the Bay’s tidal segments contain partial or full impairments related to chemical contaminants. Metals, PCBs, Tributyltin, and priority organics are found exceeding the TMDL in part or the entirety of tidal tributaries that deliver water to the mainstem of the Chesapeake Bay. This gives some idea regarding the extent of toxic contamination in Bay tidal waters.  PCB listings are present in 98% of impaired or partially impaired segments.

Due to the bioaccumulative nature of many of these substances, even if inputs to the tributaries decreases, fish tissue concentrations will not respond quickly.  There may be little positive change seen in the short term for this indicator since a large majority of partially or fully impaired segments contain a PCB impairment based on fish tissue.

(11b) Why is it important to report this information?

It is important to communicate the prevalence of toxic contamination in fish tissue, sediment, and the water column as it has both an ecosystem and human health connection.  Contamination due to bioaccumulative substances in fish tissue gives an indication of the overall presence of these substances in the Chesapeake Bay ecosystem.  Due to their bioaccumulative nature, these substances will end up in predatory species and potentially humans through fish consumption.  

The issue of chemical contamination within the Chesapeake Bay is often characterized as a localized problem pertaining to “hot spots” or the “Regions of Concern” this indicator shows that chemical contaminants are a concern for segments beyond these emphasized areas.

It is valuable to use state data to feed the indicator.  States use this data to develop 303(d) lists and eventually TMDLs.  Using states’ data strengthens the connection between the Bay Program’s and states’ communication pieces.

(12b) What detail and/or diagnostic indicators are related to this reporting level indicator?

“PCBs in White Perch” which incorporates measured concentration of PCBs in white perch for each tributary is linked to this indicator.  The white perch indicator gives more specific information for each tributary by providing specific tissue concentrations.  This indicator tells a geographic story as well.

3.  Factors Impacting Bay and Watershed Health indicators only

(7c) What is the long-term trend?  (since start of data collection) 

(8c) What is the short-term trend? (3 to 5 year trend) 

(9c) What is the current status? 

(10c) What is the key story told by this indicator?

(11c) Why is it important to report this information? 

(12c) What detail and/or diagnostic indicators are related to this reporting level indicator? 

C.  Temporal Considerations

(13) Data Collection Date(s):

The data used in this indicator is the same data used by the states of Virginia, Maryland DC to determine impairments for the 2008 impairment listing year.   Some of the 2008 listings were first determined during previous listing cycles, which used data beginning in 1996.  Therefore, a 10 year period is reflected in the data. 

(14) Planned Update Frequency (e.g. - annual, bi-annual):

(a) Source Data: States update 303(d) listings every even year. MD and VA both updated their lists in 2008 and will do so again in 2010.

(b) Indicator: Updates will be done biannually, during even years, coinciding with states’ 303(d) updates.  The indicator was updated in 2008 and will not see change again until 2010.

(15) For annual reporting, month spatial data is available for reporting:

Finalized reports are available by November of the given even numbered year.

D.  Spatial Considerations

(16) Type of Geography of Source Data (point, line polygon, other): CBP Tidal segments.

(17) Acceptable Level of Spatial Aggregation (e.g. - county, state, major basin, tributary basin, HUC): This indicator looks at major tributaries individually, determining whether each tidal segment identified contains a partial or segment-wide impairment due to toxic chemicals.

(18) Are there geographic areas with missing data?  No If so, where?

(19) The spatial extent of this indicator best described as:

(a) Chesapeake Bay (estuary) – includes major estuarine, tidal tributaries and the mainstem, using CBP segment classifications.

(b) Chesapeake Bay Watershed

(c) Other (please describe): 

Please submit any appropriate examples of how this information has been mapped or otherwise portrayed geographically in the past. 

The Toxics Subcommittee produced and updates a map that visually displays impairments.  “Tidal Waters Identified as Impaired by Toxics under State 303(d) Lists from MD, VA, D.C., and the EPA’s TMDL.”  The product indicates the percentage of tidal tributaries with any toxic impairments resulting in 303(d) listings by VA, MD, DC, and EPA.  It includes impairments due to water column and sediment data as well as fish tissue and as a result captures toxics that do no bio-accumulate in fish tissue.  This information is displayed graphically with tidal Chesapeake Bay tributaries color coded on a map with colors indicating what toxic substance or substances, if any, are responsible for listings in the tributaries.

(20) Can appropriate diagnostic indicators be represented geographically?

Geographic representation showing which tidal segments are contaminated adds valuable information to this indicator.  It may show spatial trends such as a North to South trend or difference between Eastern and Western Shores, or highlight differences between state criteria.  

E.  Data Analysis and Interpretation

(Please provide appropriate references and location of documentation if hard to find.)

(21) Is the conceptual model used to transform these measurements into an indicator widely accepted as a scientifically sound representation of the phenomenon it indicates?  (i.e., how well do the data represent the phenomenon?)  

The indicator represents the percent of tidal segments containing some impairment (partial or segment-wide).  The calculated percentage, indicator title, and description are accurate and make clear what is being presented, however there is some concern that presenting 303(d) listings in this way could be misleading, as some partial impairments are due to local contamination and do not necessarily indicate conditions throughout an entire segment.

(22) What is the process by which the raw data is summarized for development and presentation of the indicator?   

Impairments listed by MD, VA, and DC are used as the raw data for this indicator.   Following a pass or fail pattern, a segment containing one or more impairments “fails” and one containing no impairments within its boundaries “passes.”  The indicator value is the total number of “passing” segments as a percentage of the total number of segments considered.  Each segment is given equal weighting toward this calculation.  Raw data on tissue concentrations in fish collected by states feeds the development of the 303(d) list.  If concentrations are above the state determined threshold then part or all of a river is listed with impairment due to that chemical in fish tissue.  These listings are used to develop the percentage of unimpaired rivers or river segments that is presented in the indicator.

(23) Are any tools required to generate the indicator data (e.g. - Interpolator, watershed model) No

(24) Are the computations widely accepted as a scientifically sound? Yes

(25) Have appropriate statistical methods been used to generalize or portray data beyond the time or spatial locations where measurements were made (e.g., statistical survey inference, no generalization is possible)?  NA

(26) Are there established reference points, thresholds or ranges of values for this indicator that unambiguously reflect the desired state of the environment? (Health/stressors only) 

States have identified concentrations of contaminants found in fish tissue that drive impairment listings.  These are tied to ecological risk, fish consumption and human health.  Similar criteria combined with Best Professional Judgement are used to determine other listings in the sediment and water column.

F.  Data Quality

(Please provide appropriate references and location of documentation if hard to find.)

(27) Were the data collected according to an EPA-approved Quality Assurance Plan?  

If no, complete questions 28a – 28d:

(28a) Are the sampling design, monitoring plan and/or tracking system used to collect the data over time and space based on sound scientific principles?


(28b) What documentation clearly and completely describes the underlying sampling and analytical procedures used?  

MD and VA 303(d) lists provide explanations of the methodologies used to determine listings.

(28c) Are the sampling and analytical procedures widely accepted as scientifically and technically valid? 

Data accepted for inclusion in 303(d) impairment considerations must be proven scientifically and technically valid.  States submit assessments to EPA for approval; all listings considered for this indicator have been determined by states and approved by EPA.

(28d) To what extent are the procedures for quality assurance and quality control of the data documented and accessible?

QA/QC documentation for VA data is available online:

For MD a QA/QC project plan is required for those submitting data. EPA’s is given as an example for those submitting, If one is not available, MDE requests the authors supply an annual monitoring report or similar documentation to help them assess the quality of the data.

(29) Are the descriptions of the study or survey design clear, complete and sufficient to enable the study or survey to be reproduced?  Yes

(30) Were the sampling and analysis methods performed consistently throughout the data record?  We relied upon the state QA procedures to eliminate unacceptable data and data outliers.

(31) If datasets from two or more agencies are merged, are their sampling designs and methods comparable?

Data is supplied to the states from multiple sources.  Each must follow procedure that allows all data sets to be deemed comparable if they are to be included in 303(d) determination.

(32) Are uncertainty measurements or estimates available for the indicator and/or the underlying data set? No

(33) (Do the uncertainty and variability impact the conclusions that can be inferred from the data and the utility of the indicator? NA

(34) Are there noteworthy limitations or gaps in the data record?  Please explain.

Frequently more data is available where there are known contamination issues. 

G.  Additional Information


(35) Please provide any other information about this indicator you believe is necessary to aid communication and any prevent potential miss-representation.

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