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Custom Search Help
The Custom Search allows users to create customized searches and access detailed pollutant loadings information. Use the search options below to customize the search to meet specific needs. For more information about the pollutant loadings data, refer to About Loading Tool Data or Loading Tool Frequently Asked Questions (FAQs).
Select Level of Detail for Loadings Output
The Custom Search can generate three types or levels of detail of outputs.
- The annual pollutant loadings for the selected reporting year provides loadings by year, NPDES ID, outfall, and pollutant.
- The monitoring period pollutant loadings for the selected reporting year provides loadings by year, NPDES ID, outfall, monitoring period, and pollutant. The monitoring period selection allows the user to choose a specific date range (month, year) from January 2007 to the present. Due to the potentially large amount of results returned with a monitoring period search, it is recommended that users restrict the date range to less than 6 months and use additional search criteria such as state or facility ID.
- The facility-level search provides the option to identify facilities and total pollutant loadings (sum all pollutant loadings for the selected reporting year) for a year, rather than analyzing the individual pollutant loadings. The facility-level output provides a list of facilities that meet the search criteria, including facilities that do not have discharge monitoring report (DMR) data in ICIS-NPDES.
Select a Reporting Year
For annual- and facility-level searches, select a calendar year for the pollutant loadings. For a monitoring period-level search, select the Monitoring Period Date Range by choosing a month and year on the calendar picker.
Search Considerations: The Loading Tool extracts the year from the monitoring period dates associated with DMR measurements in ICIS-NPDES. Dates are included for all DMR measurements. TRI releases are reported annually. See About the Loading Tool Data for information about DMR and TRI data completeness.
On this page, the Search Criteria are organized by the order they appear on the search page. Use the hyperlinks below to quickly find the search term of interest.
- Facility Location
- Facility Outfall/Monitoring Locations
- Receiving Watershed
- Facility Characteristics
- Industry Classification
Additionally, the Custom Search allows the user to specify several loading calculation options.
Search for facilities based on their location in the Facility Registry Service (FRS). If the location is not populated in FRS, location information in ICIS-NPDES is used. Narrow search results based on ZIP Code, EPA Region, State, City, and County.
- The two-character state abbreviation for the facility location. This field is required to be populated in the source database.
- The county name for the facility location. County must be specified after a state.
- Search Considerations: County names can be blank in FRS and ICIS-NPDES. If the county name is not provided for a facility, then the county name search will produce no results for that facility.
- The city name for the facility location. City must be specified after state.
- Search Considerations: City names can be blank in FRS and ICIS-NPDES. If the city name is not provided for a facility, then the city name search will produce no results for that facility.
- ZIP Code
- The 5-digit mail code for the facility address. This field is not required to be populated in the source database.
- Search Considerations: The Loading Tool searches use ZIP codes in two ways: To identify discharges from facilities located in the specified ZIP code. For this type of search, the search will produce results if the specified ZIP code matches the first five digits of any facility's ZIP code in FRS or ICIS-NPDES. ZIP codes are not required in FRS or ICIS-NPDES. If a facility's ZIP code is blank in the Loading Tool database, then the ZIP code search will exclude the facility.
- EPA Region
- The EPA designated area that U.S. states, territories, and tribes are assigned to. There are 10 EPA regions. This field is required to be populated in the source database.
- Facility Latitude and Longitude
- The latitude or longitude of the facility or permit holder as maintained in ICIS-NPDES. Enter full or partial latitude (e.g., 35.178) or longitude (e.g., -147.2568). Try entering partial latitudes and longitudes. If you are searching on a partial latitude/longitude and return no results, try further shortening the text fragment in the search field.
- Once longitude and latitude coordinates are entered, a search radius (in miles, e.g., 1, 5, 10) must be specified.
- Permit Feature ID (outfall/pipe number)
- The 3-digit code representing the permitted outfall or pipe of interest in ICIS-NPDES (e.g., 001).
- Monitoring Location Code
- A single-character code in ICIS-NPDES that indicates the sampling location for each pollutant measurement. The Loading Tool only includes locations for effluent sampling points. See Glossary for a list of accepted codes.
Search for facilities based on watershed. Narrow search results based on Watershed ID (HUC) and Major U.S. Watersheds.
- HUC Region:
- The U.S. Geological Survey classifies watersheds in the U.S. and Caribbean into 21 regions, represented by a 2-digit Hydrologic Unit Code (HUC).
- Watershed ID (HUC)
- Code assigned by the U.S. Geological Survey used to classify watersheds in the United States and the Caribbean. Code consists of twelve digits which correspond to six levels of classification Region (first-level, 2-digit HUC), Subregion (second-level, 4-digit HUC), Accounting unit (third-level, 6-digit HUC), Cataloging unit (fourth-level, 8-digit HUC), Watershed (fifth-level, 10-digit HUC), and Subwatershed (sixth-level, 12-digit HUC). This field is not required to be populated in the source database. Separate multiple HUC12 codes with a comma or carriage return.
- Search Considerations: The Loading Tool links facility discharges with hydrologic unit codes (HUC-12) using a WATERS web service. Searching on HUC-12 will produce results if the WATERS web service returns NPDES IDs that correspond to the specified HUC-12. For more information see Overview of Watershed Data.
- Major U.S. Watersheds
- Once a watershed group has been selected a specific watershed can be chosen from the dropdown menu. This menu provides options to search watershed boundaries defined by:
- Major watersheds: The Albemarle and Pamlico Sounds, Chesapeake Bay, Columbia River Basin, Delaware Bay, Delaware River Basin, Great Lakes, Long Island Sound, Lower Columbia River Basin, Mississippi-Atchafalaya River Basin, Mobile Bay, Puget Sound, San Francisco Bay, and Tampa Bay. Many of these watersheds consist of several HUC-12 codes. Maps of these watersheds are available on Overview of Watershed Data.
- USGS: The US Geological Survey classifies watersheds in the US and Caribbean into 21 regions, represented by a 2-digit Hydrologic Unit Code (HUC).
- Large Aquatic Ecosystems (LAEs) Program: EPA's Office of Wetlands, Oceans & Watersheds classifies LAEs to include multiple small watersheds and water resources within a large geographic area that provides significant resources or services, such as food supply, recreation and tourism, groundwater recharge, flood management, air purification, nutrient cycling, and wildlife habitat.
- National Estuaries Program (NEP): The NEP identifies nationally significant estuaries of the US for protection and restoration. EPA administers the NEP, but program decisions and activities are carried out by committees of local government officials, private citizens, and representatives from other federal agencies, academic institutions, industry, and estuary user-groups. Estuaries are selected for inclusion in the program through a nomination process. There are currently 28 estuary programs implemented in the U.S.
Chesapeake Bay TMDL
- Limit to facilities that contribute to the Chesapeake Bay TMDL
- The Chesapeake Bay Total Maximum Daily Load (TMDL) is a comprehensive "pollution diet" to restore the health of the Bay and its local streams, creeks and rivers. The Chesapeake Bay TMDL - the largest such cleanup plan ever developed by the U.S. Environmental Protection Agency (EPA) - sets limits on nitrogen, phosphorus and sediment pollution necessary to meet water quality standards in the Bay and its tidal rivers.
- The Chesapeake Bay TMDL was prompted by insufficient restoration progress and continued poor water quality in the Bay and its rivers. The TMDL is designed to ensure that all pollution control measures needed to fully restore the Bay and its tidal rivers are in place by 2025, with at least 60 percent of pollution reductions completed by 2017. Watershed Implementation Plans (WIPs) detail how and when the six Bay states and the District of Columbia will meet their pollution allocations.
- For more information and the latest news about the Chesapeake Bay TMDL, visit EPA's Chesapeake Bay TMDL website. User can limit the search to facilities that contribute to the Chesapeake Bay TMDL as well as the following options:
- Significant Discharge Facility: A municipal or industrial wastewater facility defined as such by the jurisdiction in which it is permitted. Significant facilities are distinguished from nonsignificant facilities based on flow for municipals and loads for industrials. In general, but not always, significant municipal facilities have flows larger than 0.4 million gallons per day, and significant industrial facilities discharge loads larger than 3,800 pounds per year of total phosphorus and 27,000 pounds per year of total nitrogen.
- Nonsignificant Discharge Facility: A municipal or industrial wastewater discharge facility that is not defined as a significant discharge facility by the jurisdiction in which it is permitted. In general, but not always, nonsignificant municipal facilities have design flows less than 0.4 million gallons per day (Virginia and Maryland thresholds are slightly different). Nonsignificant industrial facilities discharge less than 3,800 pounds per year total phosphorus and less than 27,000 pounds per year total nitrogen.
- Major Model River Basin: Search by Chesapeake Bay water basins as constructed by modeling software. Note these models are not based on spatial location.
- Only include facilities that discharge:
- To impaired water bodies: Under section 303(d) of the Clean Water Act, states, territories, and authorized tribes are required to develop lists of impaired waters. Impaired water bodies are waters that are too polluted or otherwise degraded to meet the water quality standards set by states, territories, or authorized tribes. The law requires that these jurisdictions establish priority rankings for waters on the lists and develop TMDLs for these waters. A Total Maximum Daily Load (TMDL) is a calculation of the maximum amount of a pollutant that a water body can receive and still safely meet water quality standards.
- Pollutants contributing to a water body impairment: Search for all pollutants discharged by the facility that are potentially contributing to the impairment of local water bodies.
- To counties or watersheds with ESA-listed aquatic species: ESA-listed aquatic species are a group of organisms that live in the water for most or all of its life and are designated as threatened or endangered under the Endangered Species Act (ESA). The purpose of the ESA is to protect and recover imperiled species and the ecosystems upon which they depend. It is administered by the U.S. Fish and Wildlife Service and the Commerce Department's National Marine Fisheries Service (NMFS).
- Limit to loads that have been flagged as potential outliers or data errors
- Select the checkbox to limit results to pollutant loads that have been flagged as potential outliers. Potential outliers are automatically assigned for loads calculated from DMR measurements which vary by more than three orders of magnitude during a calendar year. See the Hierarchy of Loading Calculations or Technical Users Background Document for additional information about how loads are calculated.
- Facility Name
- The name of the facility. Separate multiple names with semicolons.
- Note: Wherever possible, search for facilities using Facility IDs. Facility names can change frequently and many facilities may be referred to by multiple names. Thus, searching on an exact facility name may not produce results.
- Facility ID
- Search for pollutant loadings by facility identifiers. Separate multiple IDs with a comma or carriage return.
- FRS ID: 12-character code in EPA's Facility Registry Service (FRS) used to uniquely identify a facility site across EPA program databases. Note that some FRS IDs may link to more than one NPDES permit.
- NPDES Permit ID: A nine-character code used to uniquely identify a permitted NPDES facility. The NPDES permit program regulates the direct discharge of pollutants into US waters.
- Toxics Release Inventory (TRI) ID: A 15-character code in TRI to identify a facility.
- Clean Watershed Needs Survey (CWNS) ID: A unique identifier for a facility in the Clean Watersheds Needs Survey, an assessment conducted by the EPA and states to determine the capital needs for municipal wastewater treatment facilities to meet the goals in the Clean Water Act. Most facilities participating are publicly owned treatment works (POTWs).
- Use the additional checkbox to limit results to only NPDES permits that link to TRI ID(s).
- Major/Minor Designation
- A facility classification from the NPDES permitting authorities based on toxic pollutant potential, ratio of discharge flow/stream flow volume, conventional pollutant loading, public health impact, water quality factors, and proximity to coastal waters. EPA places greater priority on major facilities, and requires authorized states to provide more information about the compliance status of these dischargers. For more information, refer to About the Loading Tool Data.
- Permit Type
- The permit classification in ICIS-NPDES. These classifications include the following:
- NPDES Individual Permit (NPD): An individual NPDES permit is unique to each facility. The limitations and other conditions in an individual permit are based on the facility's operations, type and amount of discharge, and receiving stream, among other factors.
- NPDES Master General Permit (NGP): A NPDES permit that covers multiple facilities that have similar discharges and are located in a specific geographic area. A general permit applies the same or similar conditions to all dischargers covered under the general permit. This is the record for the general permit that is issued by the permitting authority. It sets the conditions with which permittees will be required to comply. The Master General Permit contains no facility-specific data, and compliance and enforcement data are associated with a Master General Permit (rather any data would be associated with the General Permit Covered Facility).
- General Permit Covered Facility (GPC): A NPDES facility that is covered under a Master General Permit.
- Facility Type
- The facility ownership classification derived from codes in ICIS-NPDES.
- POTW: Publicly Owned Treatment Works. A POTW is a sewage treatment plant that is owned and usually operated by a government agency. POTWs are typically owned by local government agencies, and are usually designed to treat domestic sewage.
- Industrial Point Sources (non-POTW): This selection will return all Industrial Point Sources that are not classified as POTWs and are often referred to as "non-municipals" or "industrials." Industrial point sources may include privately owned treatment works, water treatment plants, concentrated animal feeding operations (CAFOs), or any manufacturing or commercial activity.
- Federal; and
- Treatment Technologies
- When searching by Facility Type "POTW", the user can select a treatment technology from the dropdown menu. Refer to the Clean Watersheds Needs Survey (CWNS) for information on available treatment technologies. Choose to limit the search to find facilities where the technology is or is not present. By default, the search limits to facilities where the technology is present.
- Facilities with an approved pretreatment program
- When Facility Type = POTW is selected, the user may limits the search to facilities with approved NPDES National Pretreatment Programs.
- Facilities with one or more CSO Outfalls
- When Facility Type = POTW is selected, the user may limit the search to facilities with one or more CSO Outfalls. CSO Outfalls are wastewater collection system owned by a municipality which conveys sanitary wastewater (domestic, commercial, and industrial) and storm water through a single pipe system to a publicly owned treatment work
- Pesticide-producing establishments regulated under FIFRA
- Based on EPA's Section Seven Tracking System (SSTS), one of the major systems that supports the Pesticide Program at EPA. SSTS is the only automated system that EPA uses to track pesticide producing establishments and the amount of pesticides they produce. SSTS records the registration of new establishments and records pesticide production at each establishment. Selection is not available when Facility Type = POTW is selected.
- Abandoned, inactive, or uncontrolled hazardous waste sites
- Based on EPA's CERCLIS (Comprehensive Environmental Response, Compensation and Liability Information System), a database maintained by EPA that contains information such as the current status of cleanup efforts, cleanup milestones reached, and amounts of liquid and solid media treated at sites on the National Priorities List (NPL) or under consideration for the NPL. Selection is not available when Facility Type = POTW is selected.
- Facilities subject to SPCC/FRP to prevent and respond to oil spills
- Based on EPA's OIL database contains information on Spill Prevention, Control and Countermeasure (SPCC) and Facility Response Plan (FRP) subject facilities to prevent and respond to oil spills. Selection is not available when Facility Type = POTW is selected.
- Facilities with intermittent discharges
- Limit to facilities with intermittent discharges. Facilities may have one or more outfalls that do not continuously discharge wastewater for one or more months. Some facilities may only discharge in emergency situations.
Search for facilities based on specific pollutant discharges. See DMR Pollutant Parameters Used and Not Used by the Loading Tool for a list of all pollutants in ICIS-NPDES and whether they are included in the loading tool. For additional information on the pollutant universe consult About the Loading Tool Data.
- Chemical Abstract Service (CAS) number
- A number assigned by the American Chemical Society that uniquely identifies a chemical. This field is not required to be populated in the source database, ICIS-NPDES. CAS numbers are not available for bulk parameters (e.g., biochemical oxygen demand). Therefore, this search field cannot be used to find loadings for bulk parameters.
- Search Considerations: Do not use dashes. Separate multiple CAS numbers with a comma or carriage return.
- The name used in ICIS-NPDES to identify the substance discharged. Separate multiple pollutant names with semicolons.
- Search Considerations: A pollutant name is provided for each DMR measurement in ICIS-NPDES. See About the Loading Tool Data for more information about DMR data completeness. Separate multiple pollutants with a comma or carriage return.
- Parameter Code
- Enter one or more 5-digit ICIS-NPDES parameter codes (e.g., 50060). Separate multiple parameter codes with commas or carriage returns.
- Pollutant Categories
- Categories of different types of pollutants that can be viewed as aggregated loads with the Water Pollution Search tool. The Loading Tool selects pollutant loadings for each pollutant category if the loadings are associated with parameter codes in ICIS-NPDES that are on the specified pollutant category list. The Loading Tool also includes pollutant categories for which loadings cannot be calculated. A user must conduct a separate search on the categories to view discharge information for categories without calculated loadings.
- Section 3.3.2 of the Technical Users Background Document for the Water Pollutant Loading Tool describes the pollutant categories and how the Loading Tool calculates the pollutant category loads.
- Pollutant Categories With Calculated Loadings
- Nitrogen: All parameters for total nitrogen, organic nitrogen, total Kjeldahl nitrogen, nitrite, nitrate, and ammonia are included.
- Phosphorus: All phosphorus and phosphate pollutant parameters.
- Organic Enrichment: All biochemical oxygen demand (BOD) and chemical oxygen demand (COD) pollutant parameters.
- Solids: All parameters for suspended and settable solids. This category does not include chemical-specific solids, such as suspended copper.
- Metals: All metals parameters. Hexavalent or trivalent metals and metals in ionic form (e.g., hexavalent chromium and aluminum, ion) are included, but metal compounds (e.g., calcium chloride) are not included.
- Clean Water Act Priority Pollutants: All 126 pollutants that EPA currently defines as priority pollutants.
- CERCLA Hazardous Substances: Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) hazardous substances are substances that are considered severely harmful to human health and the environment. Many are commonly used substances which are harmless in their normal uses, but are quite dangerous when released. They are defined in terms of those substances either specifically designated as hazardous under the Superfund law, or those substances identified under other laws. Superfund's definition of a hazardous substance includes the following:
- Any element, compound, mixture, solution, or substance designated as hazardous under section 102 of CERCLA.
- Any hazardous substance designated under section 311(b)(2)(a) of the Clean Water Act (CWA), or any toxic pollutant listed under section 307(a) of the CWA. There are over 400 substances designated as either hazardous or toxic under the CWA.
- Any hazardous waste having the characteristics identified or listed under section 3001 of the Resource Conservation and Recovery Act. Any hazardous air pollutant listed under section 112 of the Clean Air Act, as amended. There are over 200 substances listed as hazardous air pollutants under the Clean Air Act (CAA).
- Any imminently hazardous chemical substance or mixture which the EPA Administrator has "taken action under" section 7 of the Toxic Substances Control Act.
- TRI Chemicals: All pollutants that are associated with chemicals that are reported to EPA's Toxics Release Inventory (TRI) Program.
- Radionuclides: All parameters measuring specific radionuclides, such as Uranium and Radium isotopes. To calculate an annual loading (pounds per year), the Loading Tool converts measurements of radioactivity (in Curies) to mass using the specific activity of the radionuclide. Specific activity is the decay rate per unit mass of a particular radionuclide.
Search Considerations: The Loading Tool selects pollutant measurements for the Radionuclides category if the measurements are associated with parameter codes in ICIS-NPDES that are on the radionuclides list. This list is available in the Technical Support Documentation.
- Per- and Polyfluoroalkyl Substances (PFAS): PFAS are a group of man-made chemicals that includes Perfluorooctanoic acid (PFOA), Perfluorooctane Sulfonate (PFOS), GenX, and many other chemicals. PFAS have been manufactured and used in a variety of industries around the globe, including in the United States since the 1940s. PFOA and PFOS have been the most extensively produced and studied of these chemicals. Both chemicals are very persistent in the environment and in the human body – meaning they don’t break down and they can accumulate over time. There is evidence that exposure to PFAS can lead to adverse human health effects. Section 188.8.131.52 of the Technical Users Background Document for the Water Pollutant Loading Tool describes how the Loading Tool identifies PFAS parameters and lists the parameter codes included in the pollutant category.
- Pollutant Categories Without Calculated Loadings
- Pathogen Indicators: All parameters for total coliform, streptococci, and enteric. The Pathogen pollutant category query in the Water Pollution Search is the only query option for users to view discharges of pathogens. Because these parameters are reported in units that cannot be expressed as a mass discharge (count per 100 mL), they are excluded from all other Loading Tool searches.
- General Radioactivity: All parameters for measuring radioactivity not specific to a particular isotope, such as gross alpha and gross beta radiation. Annual loadings cannot be calculated for these parameters.
- Search Considerations: The Loading Tool selects pollutant measurements for the General Radioactivity category if the measurements are associated with parameter codes in ICIS-NPDES that are on the general radioactivity list. This list is available in the Technical Support Documentation.
- Color: All parameters measuring color in wastewater. Color measurements may be reported using a variety of units, such as Platinum Cobalt (Pt-Co) units or pound/ton produced. The Loading Tool presents the measurements in the units reported on DMRs, and does not convert the measurements into standard units. The list of color parameters is available in the Technical Support Documentation.
- Whole Effluent Toxicity: All parameters measuring Whole Effluent Toxicity (WET) in wastewater. WET refers to the aggregate toxic effect to aquatic organisms from all pollutants contained in a facility’s wastewater. WET tests measure wastewater's effects on specific test organisms' ability to survive, grow and reproduce. WET measurements may be reported using a variety of units, such as percentages or pass/fail. The Loading Tool presents the measurements in the units reported on DMRs, and does not convert the measurements into standard units. The list of WET parameters is available in the Technical Support Documentation.
- Industrial Sector ID
- Code that describes the primary activity of the facility. The two-digit code defines a major business sector, the four-digit code contains two additional numbers that denote a facility's specialty within the major sector. Choose a two-digit code from the dropdown menu or enter a four-digit code. Separate multiple SIC codes with a comma or carriage return Use the lookup feature to search for an SIC code. See the U.S. Department of Labor website for more information.
- Search Considerations: For SIC code searches, the Loading Tool identifies matching facilities based on their primary SIC code in ICIS-NPDES. SIC codes are not required to be reported in ICIS-NPDES. Searching on SIC code will only return records for facilities that have a primary SIC code in ICIS-NPDES that matches the specified SIC code for the search.
- 2-digit/6-digit NAICS code
- A six-digit code that identifies NAICS industries and has replaced the U.S. Standard Industrial Classification (SIC) system. The first two-digits represent the industry sector, in which there exist 20 broad sectors. The third digit represents the industry subsector, the fourth digit represents the industry group, the fifth digit represents the industry, and the sixth digit specifies the country (i.e. U.S., Canada, or Mexico). See the U.S. Census website for more information. Choose a two-digit code from the dropdown menu or enter a six-digit code or enter a size-digit NAICS code. Separate multiple NAICS codes with a comma or carriage return.
- Search Considerations: NAICS codes are not required to be reported to ICIS-NPDES. Searching on this field will only return results for facilities that have NAICS codes in ICIS-NPDES.
Use this section to search for facilities based on exceedances of NPDES permit limits. Search for pollutants with effluent exceedances by:
- Percent over the limit (%) - Enter the percent over (e.g., 50)
- Pounds over the limit (lb) - Enter the pounds over limit (e.g., 100)
The Custom Search provides customized loading calculations to meet a wide range of analytical needs. It is important to note how the Custom Search methodology differs from the Water Pollution Search methodology. To generate the simplified top ten rankings presented in the Water Pollution Search results, the Water Pollutant Loading Tool uses several calculation methodologies, including:
- Estimating loads using DMR data only (loadings are not estimated using permit limits);
- Estimating loads for discharges reported as "non-detect";
- Estimating loads for monitoring periods with no reported discharges;
- Grouping pollutant parameters that represent the same chemical; and
- Aggregating loads for nitrogen and phosphorus compounds (i.e., nutrients).
These methods may not be appropriate for all end-uses of the loadings data; therefore, the Custom Search offers a more versatile alternative. The Custom Search calculation methodologies are described in detail in the Technical Users Background Document.
- Select Data for Loading Calculations
- This option enables you to calculate pollutant discharges using one of the following options:
- Calculate loadings from DMR data only (default method)
- Calculate loadings using DMR data and use permit limits for months where DMR data are missing
- Calculate loadings using permit limits only
- Set Non-Detects Equal to
- When a pollutant is reported as "not detected," its actual concentration may be zero, the detection limit, or some value between zero and the detection limit. With the Loading Tool, the user can choose to calculate annual loads using one of three methods: setting all non-detects to zero, setting all non-detects to ½ the detection limit, and setting all non-detects to the detection limit.
- To generate the loadings in the Water Pollution Search, the Water Pollutant Loading Tool uses a fourth method. It sets non-detects equal to zero if the pollutant was not detected for all monitoring periods in the reporting year. If the pollutant was detected in at least one monitoring period, then the Loading Tool sets the non-detects equal to ½ the detection limit.
- Estimation Function
- The estimation function applies to situations where monitoring data for one or more monitoring periods in a reporting year are missing. The estimation function applies an estimation factor to annual loads to extrapolate the load to account for the missing monitoring data. This estimation factor is not applied to monitoring periods where the facility indicated that no discharge occurred. To generate loadings results for the Water Pollution Search, the Loading Tool sets the estimation function to "on." The user can choose to turn this estimation function on or off for the Custom Search.
- Note: The estimation function is only available for loadings that are calculated on an annual basis.
- Parameter Grouping Function
- To generate the loadings in the Water Pollution Search, the Loading Tool uses a parameter grouping function to avoid double-counting loads for pollutant parameters that represent the same pollutant. For example, an NPDES permit may require a facility to measure a pollutant in more than one way, such as total lead and dissolved lead. Because "total" includes "dissolved," summing total and dissolved would result in double counting.
- Using the parameter grouping function, the Loading Tool selects the parameter that best represents the total pollutant discharge to calculate the total pollutant load. For instance, if a facility reported discharges of both total lead and dissolved lead, Loading Tool selects total lead (ignoring dissolved lead) to calculate the lead load. If the user turns off the parameter grouping function, the Custom Search results will include loads for each pollutant parameter, reported separately (for the example, total lead and dissolved lead will be listed separately).
- Nutrient Aggregation Function
- The Loading Tool uses a nutrient aggregation methodology to generate nitrogen and phosphorus pollutant category loads for the Water Pollution Search. You have the option to use this methodology to calculate total nitrogen and total phosphorus loads in the Custom Search. If you turn off the nutrient aggregation function, the Custom Search results will include loads for each nutrient parameter, reported separately (for the example, ammonia and nitrate will be reported separately).