Skip to content

natchayal/Drinking-Water-Database

BranchesTags

Folders and files

NameName
Last commit message
Last commit date

Latest commit

 

History

135 Commits
analysis
analysis
 
 
docs
docs
 
 
get_data
get_data
 
 
images
images
 
 
README.md
README.md
 
 

Repository files navigation

Drinking Water Database Exploration

Analyzing drinking water standards and regulations. This git repository contains code for data acquision (see get_data subdirectory), analysis (see analysis subdirectory), and the jekyll site for this project (see docs subdirectory).

The website for this project can be viewed here (in progress).

💧 Executive Summary 💧

I spent a lot of time exploring various drinking water database available on the internet including national, state-level, and local-level databases. I evaluated resources on the relevance of the data they provided as well as how easily the data could be accessed and downloaded, a summary of which is provided below. Using a 1 to 5 water drop scale, with 1 being the lowest and 5 the highest, in terms of ease of access and utility of data. Ease of access ranges from 1 drop for data that is hard to access to 5 drops for data that is readily available online. In terms of utility, 1 drop denotes data with limited application, serving primarily as reference material like MCL values or enforcement dates, while 5 drops indicate data of high utility, suitable for conducting extensive analyses and answering research questions.

I also generated a number of R scripts, provided as interactive R markdown notebooks (.Rmd) files that demonstrate how some of these datasets are accessed and visualized.

While this represents a number of useful sites, it's certainly not exhaustive.

Note: The EPA ECHO database has a lot of data and easy to get lost. Recommend pre-processing data as follow to allow stitching of multiple databases: use FRS_PROGRAM_LINKS.csv to match PWSID with PGM_SYS_ID and get its matching REGISTRY_ID and FAC. PGM_SYS_ACRNM == SFDW and PGM_SYS_ID == PWSID for SDWIS data.

Summary of datasets evaluated

Source Dataset Ease of Access Data Utility Comments
EPA Safe Drinking Water Information System (SDWIS) 💧💧💧💧 💧💧💧 Limited data, easy to scrape with R.
Can get violation data, treatment, water system detail, and purchaser-seller info. Overlaps with ECHO.
Updated quarterly.
EPA Enforcement & Compliance History Online (ECHO) 💧💧💧 💧💧💧💧💧 Good, but so much data it's hard to know what's what.
See Drinking Water Dashboard for overview of SDWA regulatory activities. Extensive info on utility and contacts.
Download latest Utility Meta data as .zip.
EPA USEPA Six Year Review (SYR) 💧💧💧💧 💧💧💧💧 Data rich, easy to scrape or download as .zip file.
Reports National occurence for each contaminant with PWS info (not just the violations).
Updated every 6 years.
USGS/EPA Water Quality Portal (WQP) 💧💧💧💧💧 💧💧💧💧💧 Well organized & comprehensive data.
EPA Unregulated Contaminant Monitoring Rule (UCMR) 💧💧💧💧💧 💧💧 Easy to download as .zip file.
Reports occurrence on unregulated contaminants, disinfection type avilable for UCMR4 onwards, residual, and treatment info.
Updated every 5 years.
EPA Contaminant Candidate List (CCL) 💧💧💧💧💧 💧 Lists unregulated contaminants to be submitted as candidates for regulatory determinations.
Updated every 5 years.
EPA USEPA IRIS Information 💧💧💧💧💧 💧 Concentration on drinking (oral) route of exposure, not air. For Maximum Contaminant Level (MCL) info, refer to NPDWR table.
See ComTox Chemicals Dashboard and EPA Health Advisories tables for info on toxicology data used for setting the MCL.
EPA Drinking Water Regulations 💧💧💧💧💧 💧 SDWA rules and enforcement dates. See Regulation Timeline.
EPA Drinking Water Treatment Technologies 💧💧💧💧💧 💧 Lists available technology for drinking water treatment and their Work breakdown structure (WBS) as xlsm. Developed by EPA for cost estimates (treatment, monitoring, administrative costs).
EPA EJ Screen 💧💧💧💧 💧💧💧 Combining environmental and socioeconomic indicators for environmental jystice analysis. See EJScreen Mapping Tool. Download EJScreen Technical Documentation (PDF).
EPA Community Water System Service Area Boundaries 💧💧💧💧💧 💧💧💧💧💧 Exciting new data set, mapping application, and supporting materials for CWS service area boundaries. Developed by EPA included detailed facility, buyer-seller info, and EJScreen community report all in one place. Incredibly promising!!
EPA National PFAS Datasets 💧💧💧💧💧 💧💧💧💧💧 Exciting new data set, mapping application, and supporting materials for everything related to PFAS. PFAS Analytic Tools.

Overview of Regulatory Development Processes

The Contaminant Candidate List (CCL) is the starting point of EPA's regulatory development process. Every 5 years, EPA is required by the Safe Drinking Water Act (SDWA) to publish a new list of CCL to determine which unregulated contaminants to monitor for under EPA's Unregulated Monitoring Program (UCMR). UCMRs are limited to no more than 30 contaminants (every five years), and the monitoring is required for all large public water systems (PWSs) that serve more than 10,000 people, all small PWSs serving between 3,300 and 10,000 people, and a representative sample of small PWSs serving fewer than 3,300 people.

UCMR data are then used to make regulatory determinations of whether to develop a National Primary Drinking Water Regulation (NPWDR) for a contaminant. The SDWA requires EPA to make regulatory determinations for at least five contaminants on the CCL. During the final round of decisions which evaluates the final CCL list and UCMR results, EPA can decide to regulate or not to regulate the contaminants from the final CCL list. SDWA specifies three criteria that must be met in order for the development of a national regulation (1. Contaminant has adverse health effects on people, 2. Contaminant known to occur/substantial likelihood to occur in a PWS at frequency and level of concern, 3. Regulation of contaminant presents meaningful opportunity to reduce health risks for populations served by public water). There can be delays if additional data needs to be considered to decide whether the contaminant satisfies all three criteria, and note that the third criteria is at the sole judgement of the Administrator, the interpretation of the words in criteria can influence what action is taken.

Once the EPA has made the determination to issue a NPWDR, EPA has 24 months to develop a proposed regulation. After the proposal date, EPA has 18 months to finalize the regulation and can request an extension to that deadline if needed. Selecting the appropriate Maximum Contaminant Level (MCL) can be complicated and involves evaluating several science and policy options. EPA must consult with its Science Advisory Board (SAB) and the National Drinking Water Avisory Council (NDWAC). EPA may also conduct a "negotiated rulemaking" with stakeholders under the provisions of the Federal Advisory Committee Act (FACA). As part of the RegDet process, many organizations submit public comments such as water systems and their respective associations, state regulators (including ASDWA, AWWA, etc.), environmental advocacy groups, public interest groups, local elected officials and individual members of the public. Opportunities in the process for public input and comment are marked with a person icon.

In a separate but related regulatory effort, EPA reviews all existing regulations every six years (Six-Year Review) for evaluation of new data to assess whether a regulation needs to be revised.

Summary adapted from asdwa.org, which gives a pretty good summary of the processes.

Setting an MCL and MCLG

Reference Dose (RfD) is based on the human equivalent dose (HED) of where there's either no observed adverse effect level (NOAEL) or low observed adverse effect level (LOAEL). It is buffered by an uncertainty factor (UF) which adjusts for the interspecies, intraspecies, and/or other variabilty (e.g. from mice to humans). The RfD is then modified by body weight and the ingestion (BW/I) ratio to calculate the drinking water equivalent level (DWEL). A reduced BW/I ratio lowers the range of possible lifetime health advisory (Lifetime HA) given a range of relative source contribution (RSC) values. It is important to note that EPA uses 0.2 (20%) as a default RSC. The lowest RSC is 20% based on the assumption that chemicals with exposures less than 20% of the total will not provide a meaningful opportunity to reduce risk for the population. 80% is the highest available RSC based on the assumption that there may be minor sources not captured by the data. RSC values are typically bounded by 20% floor and 80% ceiling.

RSC of 0.2 is saying that 20% of your contribution to this contaminant comes from drinking water. Something to think about: If DWEL is 1 and RSC is 1 (100%), then your MCLG would be 1. If your DWEL was 1 and the RSC was 0.2 (20%), your MCLG would be 0.2ng/L. This means, the lower the relative source contribution, the lower it drives the MCLG! A lot of people argue that this is problematic (see PFAS for example, using RSC ranging from 0.2 to 1 can drive MCLG anywhere from 70ng/L to >600ng/L, big span!). EPA uses 35 (kg/L/day), some cases uses lower BW/I ratio to protect fetuses and women. In short, Lifetime HA or MCLG, is significantly influenced by RfD, RSC and BW/I values.

There can be multiple RfD sources whose standard are set by different agencies using their toxicological databases. For example for PFOS/PFOA: ASTDR (CDC), CA (California), NJ (New Jersey), and IRIS (USEPA) are different RfD sources used by different agencies, which uses different RfD values and could result in different Lifetime HAs or MCLGs. The difference in RfDs are most likely due to the different UFs used in calculation. EPA must decide on which MCLG to use based on the best available toxicology information. MCLG is health-based only, with adequate margins of safety, does not take cost and feasibility into consideration.

Once the Maximum Contaminant Level Goal (MCLG) is determined, EPA sets an enforceable standard. In most cases, the standard is an MCL. The MCL is set as close to the MCLG as feasible. Taking cost into consideration, EPA must determine the feasible MCL. This is defined by the Federal SDWA as the level that may be achieved with:

  • use of the best available technology or treatment approaches.
  • other means which EPA finds are available (after examination for efficiency under field conditions, not solely under laboratory conditions).

See USEPA IRIS Information and Drinking Water Treatment Technologies section.
For EPA reference on health advisories, read EPA Drinking Water Standards and Health Advisories tables.

I. National Data Sources

A. EPA Safe Drinking Water Information System (SDWIS)

  • Overview: Potential, but with obstacles; possibly redundant.

    • Violation and enforcement data are reported quarterly
    • The data are obscurely layered across different servers.
    • Possibly redundant with ECHO.
    • Queries must be done iteratively with R. Server is often down.

  • SDWIS home page: https://www.epa.gov/enviro/topic-searches#water

  • Summary: "What is the violation rate?" SDWIS tracks information on drinking water contamination levels as required by the 1974 Safe Drinking Water Act and its 1986 and 1996 amendments. The site provides data on violations and enforcement history since 1993 of the EPA's drinking water regulations.

  • Data:
    Violation:

  • Code examples :

	library(readr)

	Data1 <- read_csv(url("https://data.epa.gov/efservice/VIOLATION/ROWS/0:10000/CSV")) 
	Data2 <- read_csv(url("https://data.epa.gov/efservice/VIOLATION/ROWS/10000:20000/CSV")) 
	Data3 <- read_csv(url("https://data.epa.gov/efservice/VIOLATION/ROWS/20000:30000/CSV")) 
	Data4 <- read_csv(url("https://data.epa.gov/efservice/VIOLATION/ROWS/30000:40000/CSV")) 
	Data5 <- read_csv(url("https://data.epa.gov/efservice/VIOLATION/ROWS/40000:50000/CSV"))
	
	DataMerged_meta <- do.call("rbind", list(Data1,Data2,Data3,Data4,Data5))
	filename <- paste0("AllViolationData_EPA_EnvirofactsAPI_", format(Sys.Date(), "%m%d%y"), ".csv")
	write_csv(DataMerged_meta, file = filename)

	# Use filter or operator to select specific data to scrape, example, to only scrape Nitrate MCL violation data
	Nitrate_CWS <- read_csv(url("https://data.epa.gov/efservice/VIOLATION/pws_activity_code/A/pws_type_code/CWS/contaminant_code/1040/violation_category_code/MCL/CSV"))

Treatment:

Note: When analyzing violations, it may be more beneficial to count Public Water System (PWS) with the violation once per year, regardless of multiple quarterly violations. This method ensures a clearer understanding of yearly compliance without double-counting PWSs with multiple violations of the same contaminant due to multiple sampling. May also want to consider limiting sample to CWSs with consistent reporting over the study period and serving more than 500 people because SDWA regulations apply to small CWSs differently, especially in terms of sampling frequency. Sampling frequency could influence the likelihood of detecting a violation. For example, some DBPs only need to be sampled on an annual basis, rather than quarterly, for CWSs serving less than 500 people. Furthermore, very small systems are more likely to have inadequate reporting practices. A limitation of the SDWA violations dataset is underreporting. Check both Health-based violations (includes MCL, MRDL, TT violations) and Monitoring and reporting violatons (MR violations).

B. EPA Enforcement and Compliance History Online (ECHO)

  • Overview: Promising

  • ECHO home page: https://echo.epa.gov/

  • Summary: Provides compliance and enforcement information for over 900,000 regulated facilities nationwide. Allows query at state/county/city/zip level for a table of facilities and their compliance records. Not limited to water (NPDES and drinking water); includes air, hazardous waste,...

  • Data:

    • Main pages searches by form. Not REST interface. CSV's generated with temporary link.
    • While in https://echo.epa.gov/tools/data-downloads#downloads, scroll down to "Drinking Water Data Downloads" and download "SDWA Dataset (ZIP)"
    • SDWA Dataset (ZIP) contains files including a spreadsheet with PWS sysem info, contact: name/email/cell which can be useful for utility data requests!, address, source, size, etc. (SDWA_PUB_WATER_SYSTEMS.CSV), purchaser-seller info for each PWSID (SDWA_FACILITIES.CSV), and many more!
    • Also contains contaminant code and violation code references (SDWA_REF_CODE_VALUES.CSV), for example:
      • Contaminant Code: Nitrate (1040), TCR (3100) and RTCR (8000), HAA5 (2456), TTHMs (2950);
      • Violation Code: Average (02) and Single Sample (01) Maximum Contaminant Level Violation; Monitoring, Regular (03) and Monitoring, Check/Repeat/Confirmation (04) Violation
    • More info about ZIP file from Drinking Water Data Downloads: https://echo.epa.gov/tools/data-downloads/sdwa-download-summary contains facility information from SDWIS database (includes: Events, Facility, Geograhic Area, Violations and Enforcement, and PWS address information that can be geocoded using GIS!)
    • Web services provided: https://echo.epa.gov/tools/web-services
      • Documentation is a bit obtuse, generates temporary result files (valid for 30 min, Server often down due to Failed to load API definition.)

  • Code examples: None

C. USEPA Six Year Review (SYR)

  • Overview: Data rich, easy to scrape, and contains occurence and contaminant level data (not just the violations!)

    • Updated every 6 years.
    • Contains system info such as PWSID, system type, serving size, source water type, sampling location, treatment info, etc.
    • Dataset must be downloaded individually as Zip Files (grouped by category).
    • Can link with SDWIS database by matching PWSID to get more system information.

  • SYR home page: https://www.epa.gov/dwsixyearreview

  • Summary: "What is the typical concentration?" The Safe Drinking Water Act (SDWA) requires EPA to review each national primary drinking water regulation at least once every six years and revise them, if appropriate. As part of the "Six-Year Review," EPA evaluates any newly available data, information and technologies to determine if any regulatory revisions are needed. Revisions must maintain or strengthen public health protection.

  • Data:

  • Code examples:

nitrate <- read.delim("C:/Users/nluan/Downloads/syr3_phasechem_3/nitrate.txt")

D. US Water Quality Portal

  • Overview: Most promising!

    • Repository of many datasets from multiple sources (EPA, USGS).
    • Web services and file shares provide ready access to data with excellent documentation
    • Need to compare what data are provided relative to state/local data portals.

  • WQP home page: https://www.waterqualitydata.us/

  • Summary: The Water Quality Portal (WQP) is a cooperative service sponsored by the United States Geological Survey (USGS), the Environmental Protection Agency (EPA), and the National Water Quality Monitoring Council (NWQMC). It serves data collected by over 400 state, federal, tribal, and local agencies: https://www.waterqualitydata.us/. The data include information on sites where data are gathered, physical/chemical monitoring data, and biological sample data. Complete metadata are available here: https://www.waterqualitydata.us/portal_userguide/

  • Data:

  • Code examples:

    • USWQP/USWaterData-Scrape.Rmd uses the WQP web service to pull station data for all sites in California (N = 336801).
    • USWQP/USWaterData-Explore.Rmd provides and example for ingesting and visualizing the US Water Quality Portal data scraped for California.

E. Unregulated Contaminant Monitoring Rule (UCMR)

  • Overview: Only place to get data on unregulated contaminants

    • The 1996 Safe Drinking Water Act (SDWA) amendments require that once every five years EPA issue a new Contaminant Candidate List (CCL) of no more than 30 unregulated contaminants to be monitored by public water systems (PWSs).
    • The UCMR program was developed in coordination with the CCL.
    • Monitors all large PWSs (>10,000), all small PWSs (3,300-10,000), and a representative sample of small PWSs (<3,300).
    • Contains disinfectant type and treatment information useful info to match by PWSID and merge with data from SDWIS and SYR. Disinfectant Residual (e.g. Free Chlorine, Chloramine) and treatment information (e.g. GAC, Ionic exchange, etc.) only available UCMR4 onwards.
    • Currently the only source known to have disinfectant type explicitly reported as a column in dataset.

  • UCMR home page: https://www.epa.gov/dwucmr

  • Summary: EPA uses the Unregulated Contaminant Monitoring Rule (UCMR) to collect data for contaminants suspected to be present in drinking water, but that do not have regulatory standards set under the Safe Drinking Water Act (SDWA). The monitoring provides EPA and other interested parties with nationally representative data on the occurrence of contaminants in drinking water, the number of people potentially being exposed, and an estimate of the levels of that exposure. These data can support future regulatory determinations and other actions to protect public health.

  • Data:

  • Code examples: None

F. USEPA Contaminant Candidate List (CCL)

  • Overview: Only place to get a list of drinking water contaminants that are not currently subject to EPA drinking water regulations but under surveillance for potential future regulation.

  • CCL home page: https://www.epa.gov/ccl

  • Summary: EPA issues a new Contaminant Candidate List (CCL) every five years, serving as the first level of evaluation for unregulated drinking water contaminants if it presents a public health risk. Contaminants listed on the CCL is used to determine which contaminants to monitor for under EPA's Unregulated Monitoring Program (UCMR) and may require future regulation under the Safe Drinking Water Act (SDWA). The SDWA requires EPA to periodically decide whether or not to regulate at least five contaminants on the Contaminant Candidate List during the 'Regulatory Determination' phase. A regulatory determination is a formal decision on whether EPA should initiate a process to develop a national primary drinking water regulation (NPDWR) for a specific contaminant based on the final CCL and UCMR monitoring results. The RegDet process involves determining whether a contaminant may have adverse health effects, whether a contaminant is found or substantially likely to be found in PWS with a frequency and at levels of concern, and whther there is a meaningful opportnity for health risk reduction through a national drinking water regulation.

    • Developed in coordination with the UCMR.

  • Data:

G. USEPA IRIS Information

H. Drinking Water Treatment Technologies

I. Other Useful Database

# install the necessary libraries
library(dplyr, warn.conflicts = FALSE)
library(tidygeocoder)

# create a dataframe with addresses
some_addresses <- tibble::tribble(
  ~name,                  ~addr,
  "White House",          "1600 Pennsylvania Ave NW, Washington, DC",
  "Transamerica Pyramid", "600 Montgomery St, San Francisco, CA 94111",     
  "Willis Tower",         "233 S Wacker Dr, Chicago, IL 60606"                                  
)

# geocode the addresses
lat_longs <- some_addresses %>% 
  geocode(addr, method = 'osm', lat = latitude, long = longitude)

II. State Data Sources

EPA/State Drinking Water Dashboard (Analyze Statewide Trends)

Alaska Drinking Water Watch

California Drinking Water Watch

Illinois Drinking Water Watch

Indiana Drinking Water Watch (can select "sample point type" to identify distribution systems or entry point ID)

Louisiana Drinking Water Watch (can select "sample point type" to identify distribution systems or entry point ID)

New Jersey Drinking Water Watch

North Carolina Drinking Water Watch

Texas Drinking Water Watch

Most, if not all, states will have their own version of the drinking water watch dashboard for state specific monitoring and access to a public water system's Consumer Confidence Report (CCRs).

III. Local Data Sources

Florida

IV. Other Resources

Drinking Water Regulations

SDWA Rules and enforcement dates: contains drinking water rule pages which states the enforcement dates of each rule grouped by contaminant type.

  • Summary: The EPA regulates over 90 contaminants in drinking water, setting limits to protect health and ensure water systems can comply using current technology. The Safe Drinking Water Act allows states to enforce their own standards, provided they are as strict as the EPA's.
    • NPDWR Groundwater and Drinking Water Regulations: https://www.epa.gov/ground-water-and-drinking-water/national-primary-drinking-water-regulations
    • Regulation Timeline under the SDWA: https://www.epa.gov/sdwa/regulation-timeline-contaminants-regulated-under-safe-drinking-water-act
      • Some SDWA rule names and enforcement dates: Arsenic, Arsenic Rule (2006); GWR, Ground Water Rule (2009); IESW, Interim Enhanced SurfaceWater Treatment Rule(2002); LCR, Lead and Copper Rule (1992); LT1ESW, Long Term 1 Enhanced Surface Water Treatment Rule (2005); NIPDWR, National Interim Primary Drinking Water Regulations (1977); Phase I Rule (1989); Phase II Rule (1992); PhaseV Rule (1994); Radionuclides, Radionuclides Rule (2003); RLCR, Revised Lead and Copper Rule (2007); RTCR, Revised Total Coliform Rule (2016); Stage 1 DBPs, Stage 1 Disinfectants and Disinfection By-productsRule (2002–2004); Stage 2 DBPs, Stage 2 Disinfectants and Disinfection By-products Rule (2012–2013); SWTR, Surface Water Treatment Rule (1993); TCR, Total Coliform Rule (1990); and Trihalomethanes, Total Trihalomethanes (1981–1983).
    • Two important dates to note: When the EPA adopts a new standard for contaminants in drinking water, such as reducing the arsenic MCL from 50 ppb to 10 ppb on January 22, 2001, it also sets a compliance deadline for water utilities, which, in this case, was January 23, 2006. This gives utilities time to adjust their systems to meet the new requirements. When performing timeseries analysis, must decide on which of the two dates to use.
    • Every five years EPA reviews the list of contaminants, largely based on the Contaminant Candidate List (CCL), then list and collect monitoring data for up to 30 contaminants (UCMR), then determine whether at least five need a drinking water standard (Regulatory Determinations), if yes, then develop or revise the drinking water standard (Regulation Devlopment), then collect Six-Year Review data review and decide whether to revise the standard (SYR).

More readings:

Type of Sampling Point

Type of Sampling Point: indicates the location or function of the sampling point. Type could be one of the following:

  • DS: Distribution System—the location is in the distribution system of the water system. Examples of this type of sampling point include sampling points for Total Coliform, lead and copper, and perhaps disinfection by-products (see several of the types below for more precise ways to define disinfection by-products sampling points).

  • EP: Entry Point—location at which water enters the distribution system of a public water system. This is intended to correspond to the regulatory definition of an entry point to the distribution system representative of one or more sources of water. These should not be associated to Distribution System facilities but rather to the facility from which the water is flowing (e.g., a treatment plant, a well (if not treated prior to distribution), a common header).

  • FC: The first customer after the entry point into the distribution system. While this site is specifically needed for chlorite and chlorine dioxide distribution system samples, it may have other uses.

  • LD: Lowest Disinfectant Residual—the location where the disinfectant residual is the lowest. This type of sampling point comes directly out of the Revisions to the Unregulated Contaminant Monitoring Rule dated September 17, 1999, where the preamble explains, “Some public commentators suggested that sampling for microbiological contaminants not occur at the maximum residence time in the distribution system, but at the point of lowest disinfectant residual, since the monitoring of concern is for effectiveness of treatment and booster disinfection stations that may be in use in long distribution lines. In response, The U.S. Environmental Protection Agency added another sampling point at the ‘‘lowest disinfectant residual’’ in the distribution system.” for trihalomethane (Disinfection By-Products Rule) and/or Total Coliform sampling.

  • MD: Midpoint in the Distribution System—the Unregulated Contaminant Monitoring Rule location at which the chlorine residual would be expected to be typical for the system. This could also be used to designate those sampling points that are considered “representative points in the distribution system” under the Disinfection By-Products Rules.

  • MR: Point of Maximum Retention—the location that represents the maximum residence time of disinfectants within the distribution system under the Disinfection By-Products Rules. This can also be used as the Unregulated Contaminant Monitoring Rule location in the distribution system that is furthest from the entry point to the distribution.

  • PC: Process Control—locations normally associated with treatment plants or storage water system facilities. This sampling point type is used to demonstrate compliance with contact time or other disinfectant or treatment requirements.

  • RW: Raw Water Source—locations normally associated with intake or well water system facilities. Raw water monitoring is triggered by the detection of a contaminant at an entry point to the distribution system. This Sampling Point type can also be used to designate the raw water sampling point for precursor removal.

  • SR: Source Water Point—defined in the Unregulated Contaminant Monitoring Rule as the location at which untreated water is collected at the source.

  • UP: Unit Process—a sampling point used to evaluate the effectiveness of a unit process. This type might be used, for instance, to determine the contact time under the Surface Water Treatment Rule for a single unit process.

  • WS: Water System Facility point.

  • Source: https://dec.alaska.gov/dww/Help/html_Type_of_Sampling_Point.htm

Classifications

A public water system (PWS) must provides water for human consumption through pipes or other constructed conveyances to at least have at least 15 service connections or serves an average of at least 25 people for at least 60 days a year. It can be publicly or privately owned.

EPA has defined three types of public water systems:

  • Community Water System (CWS): A public water system that supplies water to the same population year-round.
  • Non-Transient Non-Community Water System (NTNCWS): A public water system that regularly supplies water to at least 25 of the same people at least six months per year. Some examples are schools, factories, office buildings, and hospitals which have their own water systems.
  • Transient Non-Community Water System (TNCWS): A public water system that provides water in a place such as a gas station or campground where people do not remain for long periods of time.

There are over 148,000 public water systems in the United States.

Size category (based on people served by the system)

Size category (based on people served by the system)

  • 1 = Very Small <=500
  • 2 = Small 501-3,300
  • 3 = Medium 3,301-10,000
  • 4 = Large 10,001-100,000
  • 5 = Very large >100,000

US EPA Regional Offices

  • Summary: EPA has ten Regional offices, each responsible for execution of their programs within several states and territories.
  • Link to image source and to get more information: EPA Regional and Geographic Offices

About

Analyzing drinking water standards and regulations

Resources

Readme
Activity

Stars

0 stars

Watchers

1 watching

Forks

0 forks
Report repository

Releases

No releases published

Packages

No packages published

Languages