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USGS2017

California sea otter (Enhydra lutris nereis) census results, Spring 2017

The 2017 census of southern sea otters ( Enhydra lutris nereis ) was conducted between late April and early July along the mainland coast of central California and in April at San Nicolas Island in southern California. The 3-year average of combined counts from the mainland range and San Nicolas Island was 3,186, down by 86 sea otters from the previous year. This is the second year that the official index has exceeded 3,090, the Endangered Species Act delisting threshold identified in the U.S. Fish and Wildlife Service’s Southern Sea Otter Recovery Plan (the threshold would need to be exceeded for 3 consecutive years before delisting consideration). The 5-year average trend in abundance, including both the mainland range and San Nicolas Island populations, remains positive at 2.3 percent per year. Continuing lack of growth in the range peripheries likely explains the cessation of range expansion.

California↗

USGS2017

Groundwater data collection for the Quinault Indian Nation, Grays Harbor and Jefferson Counties, Washington

Groundwater data were collected on the Quinault Indian Reservation to provide the Quinualt Indian Nation (QIN) with basic knowledge of the existing wells and springs on the reservation, and to establish a water-level network to be monitored by QIN to begin building a long-term groundwater dataset. The 327 mi 2 Quinault Indian Reservation is located within the heavily forested Queets-Quinault watershed along the west-central coast of Washington and includes the coastal communities of Taholah and Queets, and the inland community of Amanda Park. Groundwater data were collected or compiled for 87 sites—82 wells and 5 springs. In October 2016, a field inventory was done to locate the sites and acquire site data. Groundwater levels were measured in 15 of the field-inventoried wells and 3 of those wells were observed as flowing (artesian). A monthly groundwater‑level monitoring network of 13 wells was established by the U.S. Geological Survey in March 2017, and the network was transferred to QIN in June 2017 for continued measurements. Several data needs were identified that would provide a more complete understanding of the groundwater system of the Quinault Indian Reservation. The collection of monthly water-level data for multiple years is an important first step in understanding seasonal and long term changes in water levels. Additionally, the collection of baseline groundwater chemistry and quality data across the reservation would help with future efforts to monitor existing and potentially changing groundwater quality conditions. Development of a water budget of the Queets-Quinault Watershed and the reservation within that area would provide water users with a better understanding of this important resource and provide needed information about the competing demands on local water sources.

Washington↗

USGS2017

Chemical quality of water and bottom sediment, Stillwater National Wildlife Refuge, Lahontan Valley, Nevada

The U.S. Geological Survey, in cooperation with the U.S. Fish and Wildlife Service collected data on water and bottom-sediment chemistry to be used to evaluate a new water rights acquisition program designed to enhance wetland habitat in Stillwater National Wildlife Refuge and in Lahontan Valley, Churchill County, Nevada. The area supports habitat critical to the feeding and resting of migratory birds travelling the Pacific Flyway. Information about how water rights acquisitions may affect the quality of water delivered to the wetlands is needed by stakeholders and Stillwater National Wildlife Refuge managers in order to evaluate the effectiveness of this approach to wetlands management. A network of six sites on waterways that deliver the majority of water to Refuge wetlands was established to monitor the quality of streamflow and bottom sediment. Each site was visited every 4 to 6 weeks and selected water-quality field parameters were measured when flowing water was present. Water samples were collected at varying frequencies and analyzed for major ions, silica, and organic carbon, and for selected species of nitrogen and phosphorus, trace elements, pharmaceuticals, and other trace organic compounds. Bottom-sediment samples were collected for analysis of selected trace elements. Dissolved-solids concentrations exceeded the recommended criterion for protection of aquatic life (500 milligrams per liter) in 33 of 62 filtered water samples. The maximum arsenic criterion (340 micrograms per liter) was exceeded twice and the continuous criterion was exceeded seven times. Criteria protecting aquatic life from continuous exposure to aluminum, cadmium, lead, and mercury (87, 0.72, 2.5, and 0.77 micrograms per liter, respectively) were exceeded only once in filtered samples (27, 40, 32, and 36 samples, respectively). Mercury was the only trace element analyzed in bottom-sediment samples to exceed the published probable effect concentration (1,060 micrograms per kilogram).

Nevada↗

USGS2018

Chemical concentrations in water and suspended sediment, Green River to Lower Duwamish Waterway near Seattle, Washington, 2016–17

From August 2016 to March 2017, the U.S. Geological Survey (USGS) collected representative samples of filtered and unfiltered water and suspended sediment (including the colloidal fraction) at USGS streamgage 12113390 (Duwamish River at Golf Course, at Tukwila, Washington) during 13 periods of differing flow conditions. Samples were analyzed by Washington-State-accredited laboratories for a large suite of compounds, including metals, dioxins/furans, semivolatile compounds including polycyclic aromatic hydrocarbons, butyltins, the 209 polychlorinated biphenyl (PCB) congeners, and total and dissolved organic carbon. Concurrent with the chemistry sampling, water-quality field parameters were measured, and representative water samples were collected and analyzed for river suspended-sediment concentration and particle-size distribution. The results provide new data that can be used to estimate sediment and chemical loads transported by the Green River to the Lower Duwamish Waterway.

Washington↗

USGS2018

Chirp subbottom profile data collected in 2015 from the northern Chandeleur Islands, Louisiana

As part of the Barrier Island Evolution Research project, scientists from the U.S. Geological Survey (USGS) St. Petersburg Coastal and Marine Science Center conducted a nearshore geophysical survey around the northern Chandeleur Islands, Louisiana, in September 2015. The objective of the project is to improve the understanding of barrier island geomorphic evolution, particularly storm-related depositional and erosional processes that shape the islands over annual to interannual time scales (1–5 years). Collecting geophysical data can help researchers identify relations between the geologic history of the islands and their present day morphology and sediment distribution. High-resolution geophysical data collected along this rapidly changing barrier island system can provide a unique time-series dataset to further the analyses and geomorphological interpretations of this and other coastal systems, improving our understanding of coastal response and evolution over medium-term time scales (months to years). Subbottom profile data were collected in September 2015 offshore of the northern Chandeleur Islands, during USGS Field Activity Number 2015-331-FA. Data products, including raw digital chirp subbottom data, processed subbottom profile images, survey trackline map, navigation files, geographic information system data files and formal Federal Geographic Data Committee metadata, and Field Activity Collection System and operation logs are available for download.

Louisiana↗

USGS2018

Nearshore coastal bathymetry data collected in 2016 from West Ship Island to Horn Island, Gulf Islands National Seashore, Mississippi

The U.S. Geological Survey (USGS) St. Petersburg Coastal and Marine Science Center, in cooperation with the U.S. Army Corps of Engineers, Mobile District, conducted bathymetric surveys of the nearshore waters surrounding Ship and Horn Islands, Gulf Islands National Seashore, Mississippi. The objective of this study was to establish base-level elevation conditions around West Ship, East Ship, and Horn Islands and their associated active littoral system prior to restoration activities. These activities include the closure of Camille Cut and the placement of sediment in the littoral zone of East Ship Island. These surveys can be compared with future surveys to monitor sediment migration patterns post-restoration and can also be measured against historic bathymetric datasets to further our understanding of island evolution. The USGS collected 667 line-kilometers (km) of single-beam bathymetry data and 844 line-km of interferometric swath bathymetry data in July 2016 under Field Activity Number 2016-347-FA. Data are provided in three datums: (1) the International Terrestrial Reference Frame of 2000 (ellipsoid height); (2) the North American Datum of 1983 (NAD83) CORS96 realization and the North American Vertical Datum of 1988 with respect to the GEOID12B model (orthometric height); and (3) NAD83 (CORS96) and Mean Lower Low Water (tidal datum). Data products, including x,y,z point datasets, trackline shapefiles, digital and handwritten Field Activity Collection Systems logs, 50-meter digital elevation model, and formal Federal Geographic Data Committee metadata, are available for download.

Mississippi↗

USGS2018

Distribution and abundance of Least Bell’s Vireos (Vireo bellii pusillus) and Southwestern Willow Flycatchers (Empidonax traillii extimus) on the Middle San Luis Rey River, San Diego County, southern California—2017 data summary

We surveyed for Least Bell’s Vireos (LBVI) ( Vireo bellii pusillus ) and Southwestern Willow Flycatchers (SWFL) ( Empidonax traillii extimus ) along the San Luis Rey River, between College Boulevard in Oceanside and Interstate 15 in Fallbrook, California (middle San Luis Rey River), in 2017. Surveys were conducted from April 13 to July 11 (LBVI) and from May 16 to July 28 (SWFL). We found 146 LBVI territories, at least 107 of which were occupied by pairs. Five additional transient LBVIs were detected. LBVIs used five different habitat types in the survey area: mixed willow, willow-cottonwood, willow-sycamore, riparian scrub, and upland scrub. Forty-four percent of the LBVIs occurred in habitat characterized as mixed willow and 89 percent of the LBVI territories occurred in areas with greater than 50 percent native plant cover. Of 16 banded LBVIs detected in the survey area, 8 had been given full color-band combinations prior to 2017. Four other LBVIs with single (natal) federal bands were recaptured and banded in 2017. Three LBVIs with single dark blue federal bands indicating that they were banded as nestlings on the lower San Luis Rey River and one LBVI with a single gold federal band indicating that it was banded as a nestling on Marine Corps Base Camp Pendleton (MCBCP) could not be recaptured for identification. One banded LBVI emigrated from the middle San Luis Rey River to the lower San Luis Rey River in 2017. One resident SWFL territory and one transient Willow Flycatcher of unknown subspecies (WIFL) were observed in the survey area in 2017. The resident SWFL territory, which was comprised of mixed willow habitat (5–50 percent native plant cover), was occupied by a single male from May 22 to June 21, 2017. No evidence of pairing or nesting activity was observed. The SWFL male was banded with a full color-combination indicating that he was originally banded as a nestling on the middle San Luis Rey River in 2014 and successfully bred in the survey area in 2016. The male SWFL left the middle San Luis Rey River after June 21, 2017 and subsequently was detected on the San Dieguito River on June 26, 2017, by USGS biologists. The transient WIFL was detected on May 30, 2017, in mixed willow habitat comprised of 50–95 percent of native plant cover.

California↗

USGS2018

Concentrations of nitrate in drinking water in the lower Yakima River Basin, Groundwater Management Area, Yakima County, Washington, 2017

The U.S. Geological Survey, in cooperation with the lower Yakima River Basin Groundwater Management Area (GWMA) group, conducted an intensive groundwater sampling collection effort of collecting nitrate concentration data in drinking water to provide a baseline for future nitrate assessments within the GWMA. About every 6 weeks from April through December 2017, a total of 1,059 samples were collected from 156 wells and 24 surface-water drains. The domestic wells were selected based on known location, completion depth, ability to collect a sample prior to treatment on filtration, and distribution across the GWMA. The drains were pre-selected by the GWMA group, and further assessed based on ability to access sites and obtain a representative sample. More than 20 percent of samples from the domestic wells and 12.8 percent of drain samples had nitrate concentrations that exceeded the maximum contaminant level (MCL) of 10 milligrams per liter established by the U.S. Environmental Protection Agency. At least one nitrate concentration above the MCL was detected in 26 percent of wells and 33 percent of drains sampled. Nitrate was not detected in 13 percent of all samples collected.

Washington↗

USGS2018

Groundwater-quality data from the eastern Snake River Plain Aquifer, Jerome and Gooding Counties, south-central Idaho, 2017

Groundwater-quality samples and water-level data were collected from 36 wells in the Jerome/Gooding County area of the eastern Snake River Plain aquifer during June 2017. The wells included 30 wells sampled for the U.S. Geological Survey’s National Water-Quality Assessment project, plus an additional 6 wells were selected to increase spatial distribution. The data provide water managers with the ability for an improved understanding of groundwater quality and flow directions in the area. Groundwater-quality samples were analyzed for nutrients, major ions, trace elements, and stable isotopes of water. Quality-assurance and quality-control measures consisted of multiple blank samples and a sequential replicate sample. All data are available online at the USGS National Water Information System.

Idaho↗

USGS2018

Detections of current-use pesticides at 12 surface water sites in California during a 2-year period beginning in 2015

Surface water samples were collected by the U.S. Geological Survey and multiple cooperators during base flow/irrigation runoff and storm runoff conditions from 12 sites throughout California, over 2 consecutive years beginning in April 2015, from both urban and agriculturally dominated watersheds. Water samples were analyzed by gas chromatography/mass spectrometry and liquid chromatrography/tandem mass spectrometry for a suite of 157 pesticides and degradates. Suspended sediments associated with these water samples were analyzed by gas chromatography/mass spectrometry for a suite of 131 pesticides and degradates. Overall, 85 pesticides and degradates were detected in the water: 32 fungicides, 25 herbicides, 27 insecticides, and 1 synergist. In the suspended sediment, 29 pesticides were detected: 9 fungicides, 10 herbicides, and 10 insecticides. Sixteen pesticides (bifenthrin, carbendazim, chlorpyrifos, clothianidin, diazinon, diuron, fenpyroximate, fipronil, fipronil sulfone, fluopicolide, imidacloprid, metolachlor, novaluron, oxyflurofen, permethrin, and simazine) were detected in the water at concentrations that were above at least one aquatic life benchmark value as defined by the U.S Environmental Protection Agency.

California↗

USGS2018

Pesticide inputs to the Sacramento–San Joaquin Delta, 2015–16: Results from the Delta Regional Monitoring Program

Emergent hypotheses about causes of the pelagic organism decline in the Sacramento–San Joaquin Delta (Delta) indicate that a more complete understanding of the quality of water entering the Delta is needed. Less than half of all pesticides used in the Delta watershed are measured in samples collected for routine monitoring, and with new pesticides continually being registered for use, the concentrations of unmonitored pesticides in the Delta ecosystem are unknown. In response, a multi-year, cooperative effort to improve monitoring of mercury, nutrients, pathogens, and pesticides was begun by the Delta Regional Monitoring Program (RMP). In July 2015, the U.S. Geological Survey in cooperation with the Delta RMP began measuring concentrations of 154 pesticide compounds in monthly samples of surface water and suspended sediment collected at five major inputs to the Sacramento–San Joaquin Delta from July 2015 to June 2016. In addition to pesticide concentration measurements, field water-quality indicators (water temperature, specific conductance, dissolved oxygen, pH, and turbidity) were measured at each site and samples were collected for the analysis of dissolved organic carbon, dissolved copper, particulate organic carbon, particulate inorganic carbon, total particulate carbon, and total particulate nitrogen. Pesticide concentrations in particulates were measured in collected suspended-sediment samples by gas chromatography with mass spectrometry, whereas concentrations measured in surface-water samples utilized a combination of gas chromatography with mass spectrometry and liquid chromatography with tandem mass spectrometry. Samples were collected from two sites in the San Joaquin River watershed and at one site for each of the Mokelumne River, Sacramento River, and Ulatis Creek watersheds. All water samples contained mixtures of 2–25 pesticides. Pesticides were detected in 100 percent of surface-water samples. A total of 54 pesticide compounds were detected in water samples during the study period (19 fungicides, 18 herbicides, 9 insecticides, 7 breakdown products, and 1 synergist). The most frequently detected pesticide compounds were the herbicides hexazinone (95 percent) and diuron (73 percent) and the fungicides boscalid (93 percent) and azoxystrobin (75 percent). Pesticide concentrations ranged from below the method detection limits to 2,630 nanograms per liter for the herbicide metolachlor. A total of 11 pesticide compounds were detected in the suspended sediments filtered from water samples (6 herbicides, 3 insecticides, 1 fungicide, and 1 breakdown product). The most frequently detected compounds were the insecticides permethrin (7 percent) and bifenthrin (5 percent) and the herbicide pendimethalin (5 percent). Pesticide concentrations in the suspended-sediment ranged from below the method detection limit to 265 nanograms per liter for the herbicide pendimethalin.

California↗

USGS2003

Streamwater Quality Data from the 2002 Hayman, Hinman, and Missionary Ridge Wildfires, Colorado, 2003

Concern about water-quality issues related to wildfires in Colorado has intensified because of the wildfires that occurred in Colorado during the summer of 2002. In 2003, the U.S. Geological Survey (USGS) conducted water-quality sampling of burned and unburned watersheds in the areas affected by the Hayman, Hinman, and Missionary Ridge wildfires to provide information to scientists, watershed managers, and public-water suppliers regarding the extent to which wildfires may cause water-quality degradation.

Data Series↗

USGS2018

Hydrogeologic framework for characterization and occurrence of confined and unconfined aquifers in quaternary sediments in the glaciated conterminous United States—A digital map compilation and database

The U.S. Geological Survey has created a hydrogeologic framework for Quaternary sediments in glaciated areas of the conterminous United States that categorizes, maps, and characterizes the glacial sediments at and beneath the land surface. The hydrogeologic framework divides the glaciated United States into 17 distinct hydrogeologic terranes using a geologic approach based on previous mapping, and was characterized using the Glacial Environments and Surficial Sediments geodatabase compiled from the Quaternary Atlas of the United States map series, the Surficial Materials Map of the United States, and several Integrated Geologic Map Databases for the United States; a groundwater use database compiled from public-supply, water-well data; and a lithologic database compiled from State-managed well records and geologic logs. This framework is to be used to assess the occurrence and characteristics of confined and unconfined glacial aquifers, their distribution and extent, and their potential intrinsic susceptibility and vulnerability.

Data Series↗

USGS2018

Abundance and productivity of marbled murrelets (Brachyramphus marmoratus) off central California during the 2017 breeding season

Marbled murrelets ( Brachyramphus marmoratus ) have been listed as “Endangered” by the State of California and “Threatened” by the U.S. Fish and Wildlife Service since 1992 in California, Oregon, and Washington. Information regarding marbled murrelet abundance, distribution, population trends, and habitat associations is critical for risk assessment, effective management and evaluation of conservation efficacy, and ultimately to meet Federal- and State-mandated recovery efforts for this species. During June–August 2017, the U.S. Geological Survey Western Ecological Research Center continued previously established, long-term (1999–2016), at-sea surveys to estimate abundance and productivity of marbled murrelets in U.S. Fish and Wildlife Service Conservation Zone 6 (central California—San Francisco Bay to Monterey Bay). Using conventional distance sampling methods, we estimated marbled murrelet abundance using 189 detections of 321 individuals observed on nine unique surveys. The abundance estimated for the entire study area using all surveys in 2017 was 530 birds (95-percent confidence interval, 384–732 birds). Estimated abundance from 2017 is comparable to most prior years of study, except for 2008 and 2015, which had anomalously low abundances. We estimated productivity (calculated as the hatch-year [HY] to after-hatch-year [AHY] ratio) in 2017 using three detections of three individuals observed in six surveys. After date-correcting HY and AHY counts to account for birds expected to be absent from the water while inland at nests, the date-corrected juvenile ratio was 0.022 ± 0.014 standard error. We created a synthesized database of all marbled murrelet survey data from 1999 to 2017 to allow scientists and managers to evaluate established survey methods and assess trends in abundance and productivity estimates. Future modifications of survey design could help reduce variance in abundance estimation.

California↗

USGS2018

High-water marks from Hurricane Sandy for coastal areas of Connecticut, Rhode Island, and Massachusetts, October 2012

Because coastal areas in Connecticut, Rhode Island, and Massachusetts were heavily affected by Hurricane Sandy in October 2012, the U.S. Geological Survey (USGS), under a mission agreement with the Federal Emergency Management Agency, collected storm tide high-water marks in those coastal areas. This effort was undertaken to better understand the areal extent and impact of storm tides resulting from strong storms. On October 27–29, 2012, Hurricane Sandy moved up the eastern coast of the United States after passing over the Bahamas. On October 29 at about 7:30 p.m. eastern daylight time, Hurricane Sandy made landfall its final time near Brigantine, New Jersey, with recorded wind speeds of about 80 miles per hour. The damages from Hurricane Sandy exceeded $50 billion in total, making it the second most costly Atlantic hurricane at that time, second only to Hurricane Katrina in 2005. Hurricane Sandy also resulted in 147 deaths, and about 650,000 homes and many businesses being damaged along the eastern coast of the United States. The severity of Hurricane Sandy’s effects resulted in presidential disaster declarations being declared in 10 States from Virginia to Massachusetts and the District of Columbia in the months following Hurricane Sandy; the list of States affected included Connecticut, Rhode Island, and Massachusetts. In response to the approach of Hurricane Sandy, the USGS deployed 60 temporary storm tide sensors and 2 temporary real-time rapid deployment gages to collect tide elevation data during the storm along the coastal areas of Connecticut, Rhode Island, and Massachusetts. This activity was done from Virginia to Maine before the storm. Following Hurricane Sandy, in October and November 2012, 371 storm tide high-water marks were identified and flagged in the coastal areas of Connecticut, Rhode Island, and Massachusetts. High-water marks near USGS temporary storm tide sensors, real-time rapid deployment gages, and streamgages affected by the tides as well as high-water marks on Block Island, R.I., and Martha’s Vineyard and Nantucket, Mass., were surveyed at the same time the high-water marks were identified and flagged in October and November 2012. The remaining high-water marks flagged during October and November 2012 were surveyed from December 2013 through June 2014 and in December 2016. Elevations of all high-water marks were referenced to the North American Vertical Datum of 1988 and horizontal coordinates to the North American Datum of 1983 using the Global Navigation Satellite System, survey-grade Digital Global Positioning System receivers, and total station surveying equipment. Of the 371 storm tide high-water marks flagged following Hurricane Sandy, only 364 high-water marks were surveyed; the remaining 7 could not be found or had been destroyed when locations were revisited to conduct surveys. The 157 high-water marks surveyed in Connecticut had elevations that ranged from 2.5 to 12.2 feet (ft) with an average elevation of 8.1 ft and a median elevation of 8.3 ft. The 76 high-water marks in Rhode Island had elevations that ranged from 3.6 to 16.2 ft and averaged 7.1 ft with a median of 6.6 ft. The 131 high-water marks in Massachusetts had elevations that ranged from 2.8 to 22.7 ft and averaged 7.3 ft with a median of 6.6 ft. Individual information on the location, type, accuracy, and elevation of the 371 high-water marks can be found in an accompanying USGS data release and at the USGS Flood Event Viewer website for Hurricane Sandy ( https://stn.wim.usgs.gov/fev/#Sandy ). The high-water marks along the coast line of Connecticut and eastern Massachusetts, including Nantucket, generally had higher storm tide elevations than the coast line of Rhode Island including Block Island and southern Massachusetts, including Martha’s Vineyard. The high-water mark elevations compare well with recorded peak-storm tide data at USGS temporary storm tide sensors and real-time rapid deployment gages deployed for Hurricane Sandy in Connecticut, Rhode Island, and Massachusetts. High-water mark data collected following Hurricane Sandy will be used by Federal, State, and local government agencies, nongovernmental organizations, universities, and the public for better understanding the areal extent and impact of the storm tides. Additionally, these data can be used for such activities as land-use planning, flood risk studies, flood resiliency studies, and coastal modeling. These data from this historic storm can be compared with other regional hurricanes and tropical storms for planning into the future.

Connecticut, Massachusetts, Rhode Island↗

USGS2018

California sea otter (Enhydra lutris nereis) census results, spring 2018

The 2018 census of southern sea otters ( Enhydra lutris nereis ) was conducted from late April to mid-May along the mainland coast of central California and in April at San Nicolas Island in southern California. The 3-year average of combined counts from the mainland range and San Nicolas Island was 3,128, a decrease of 58 sea otters from the previous year. The 5-year average trend in abundance, including both the mainland range and San Nicolas Island populations, remains positive at 1.3 percent per year. Continuing lack of growth in the range peripheries likely explains the cessation of range expansion.

California↗

USGS1998

Geology of the conterminous United States at 1:2,500,000 scale a digital representation of the 1974 P.B. King and H.M. Beikman map

This CD-ROM contains a digital version of the Geologic Map of the United States, originally published at a scale of 1:2,500,000 (King and Beikman, 1974b). It excludes Alaska and Hawaii. In addition to the graphical formats, the map key is included in ASCII text. A geographic information system (GIS) allows combining and overlaying of layers for analysis of spatial relations not readily apparent in the standard paper publication. This disc contains only geology. However, digital data on geology, geophysics, and geochemistry can be combined to create useful derivative products-- for example, see Phillips and others (1993). This CD-ROM contains a copy of the text and figures from Professional Paper 901 by King and Beikman (1974a). This text describes the historical background of the map, details of the compilation process, and limitations to interpretation. The digital version of the text can be searched for keywords or phrases.

Data Series↗

USGS2019

Point-source nutrient loads to streams of the conterminous United States, 2012

Total nitrogen and phosphorous loads were estimated for 5,430 major point-source facilities (all types) and 11,537 minor wastewater treatment facilities discharging to streams in the conterminous United States during 2012. Facilities classified as a major discharger are typically a facility that discharges greater than one million gallons of water per day however some industrial facilities are classified as a major based on specific criteria developed by the U.S. Environmental Protection Agency (EPA) and the National Pollutant Discharge Elimination System state program. Data documenting discharge information from point sources were obtained from the EPA’s Integrated Compliance Information System (ICIS) and Permit Compliance System (PCS). When available, actual nutrient concentration measurements were used to calculate point-source loads. In the many cases in which concentration data were not available in either the ICIS or PCS databases, typical pollutant concentrations (TPCs) were developed using data from similar facilities. A new method for calculating TPCs was implemented that allows varying amounts of nutrient concentration data and (or) varying numbers of facilities to determine TPCs. This new method minimized the effect that any single facility discharging extremely large nutrient concentrations had on resultant TPC values. Because of the smaller TPC values from this new TPC method, the total nutrient load for many states was reduced compared to previous TPC methods. Major wastewater treatment facilities are the largest contributor of nutrient loads to streams even though there are almost three times as many minor wastewater treatment facilities. Specifically, 4,218 major wastewater treatment facilities account for 94 percent of the total nitrogen load for the conterminous United States, whereas 11,397 minor wastewater treatment facilities contribute 6 percent of the total nitrogen load. Total phosphorous loads are similarly divided among major (93 percent) and minor (7 percent) wastewater treatment facilities. Total nitrogen loads, including all facility types, primarily are from wastewater treatment facilities and some petroleum refining facilities. Total phosphorous loads also are primarily from wastewater treatment facilities, but several manufacturing facilities such as corn milling, pulp and paper mills, and industrial chemical facilities also contribute to total phosphorous loads.

Data Series↗