Useful Septic System Statistics

Transcription

1 GENERAL Useful Septic System Statistics - About 25% of the nation s households are served by onsite/septic systems (see Census data) - Approximately 33% of new construction is served by onsite systems (see Census data) - More than 50% of onsite systems are located within Standard Metropolitan Statistical Areas (cities and their suburbs) - Conservatively 10% to 30% of onsite systems are significantly failing at any given point in time - Over 50% of onsite systems are over 30 years old (greatly increasing their likelihood to be failing) - CENSUS DATA Historical Summary (from Decennial Census ): 1990 Census: Households served by septic tank or cesspool: 24.1% of total occupied housing units (Alabama: 44%, ME: 51%; NH: 49%; NC: 49%; SC: 41%; VT: 55%; WV: 41%) 1980 Census: 24.1% 1970 Census: 24.5% 1960: Units lacking a flush toilet: 10.3% 1950: : 24.5% 1940: 35.3% (MS: 81%; Alabama: 71%; Arkansas: 79%) American Housing Survey for the United States: Conducted by U.S. Census Bureau for HUD to obtain up-to-date housing statistics. Covers an average of 55,000 homes; data collected by field rep s. National data collected every other year; data for 46 selected SMSA s taken every 4 years Housing Survey: Conducted from 8/97 through 11/97. Issued September, Some results of 1995 and 1997 Housing Surveys: Total no. of housing units: 112,357,000 Total occupied units: 97,693,000 99,487,000 Occupied units on public sewer: 75,282,000 (77%) 76,906,000 (77%) Occupied units on septic/cesspools: 22,296,000 (23%) 22,479,000 (23%) with breakdowns in last 3 mo s: 407,000 (2%) 403,000 (2%) Occupied new housing units (built in previous 4 years): 5,848,000 Occupied new housing units served by onsite: 1,962,000 (33%)

2 Definitions: Sewage Disposal and Sewage Disposal Breakdowns (1997 Survey) : A public sewer is connected to a city, county, sanitary district, neighborhood, or subdivision sewer system, serving six or more units. A septic tank or cesspool is an underground tank or pit used for disposal of sewage (serving five or fewer units.) A chemical toilet, which may be inside or outside the unit, uses chemicals to break down or dissolve sewage. Housing units for which sewage is disposed of in some other way are included in the "other" category. The data on breakdowns in the means of sewage disposal are limited to housing units in which the means of sewage disposal was a public sewer, septic tank, or cesspool. Breakdowns refer to situations in which the system was completely unusable. Examples include septic tank being pumped because it no longer perked, tank collapsed, tank exploded, sewer main broken, sewer treatment plant not operating as a result of electrical failure or water service interruption, etc. Data on breakdowns are shown if they occurred in the 3 months prior to the interview or while the household was living in the unit if less than 3 months, and if the breakdown lasted 6 consecutive hours or more. Housing units with a breakdown in sewage disposal are also classified according to the number of breakdowns. According to homeowners responding to the Census survey (1995), 10% experienced catastrophic failure of their septic system at least once during the previous year. Significant failures, some of which are not easily detected by the homeowner, are probably affecting at least 25% of septic systems, based on data from the State of Massachusetts. Even at a 10% failure rate, this represents over 2.5 million failures in In terms of wastewater volumes, this represents over 343 million gallons of inadequately treated effluent potentially entering ground or surface waters on any given day in the United States. (2.5 million systems X 2.5 pp/hh X 55 gpcd) WATER QUALITY PROBLEMS IDENTIFIED BY EPA: - Types of problems where failing systems are a contributor: - Closure of swimming beaches and shellfish beds; - contamination of drinking water supplies; - eutrophication of ponds, lakes, coastal embayments - Contaminated Drinking Waters: (Source: EPA s gw protection proposed reg s): Sourcecontaminated ground water-based drinking water systems result in an estimated 168,000 viral illnesses per year due to contamination. Another 34,000 cases of bacterial illnesses are estimated to occur annually. Malfunctioning septic systems are identified as one source of this contamination. - Septic systems were a leading source of pollution for over one-third (36%) of the impaired miles of ocean shoreline surveyed as part of the (1996) National Water Quality Inventory (305(b) report). - (From (b) Report):

3 (1) In 1996, EPA requested each State to indicate the top 10 sources that potentially threaten their ground water resources. For each source, States were also asked to identify the contaminants impacting gw quality. Thirty-seven States provided information related to contaminant sources. Septic systems were the third most-frequently mentioned source of ground water contamination, cited by 29 out of 37 states. Concerns included location of septic systems relative to sources of drinking water, the large number of residential septic tank systems, and human health. (2) Ground water may be contaminated by releases from septic systems when the systems are poorly designed (tanks and drainfields are installed in areas with inadequate soils or shallow depth to ground water); poorly constructed or sealed; are improperly used, located or maintained; or are abandoned. Pollutants of concern: pathogenic bacteria and viruses, nitrates, phosphates from detergents, and various chemicals from cleaners and other products used in the home. (3) American households dispose of an estimated 3.5 billion gallons of liquid waste into domestic septic systems each day. (4) The most misused septic systems are those used by the automotive repair/servic businesses that dispose of engine fluids, fuels and cleaning solvents. As much as 4 million pounds of waste per year are disposed of by commercial sites into septic systems that have affected the drinking water of approximately 1.3 million Americans. - Shellfish Growing Waters: The National Shellfish Register has been published every few years since 1966 to provide summary information on the status and extent of the nation s commercial shellfish growing areas. (Currently published by NOAA). Classification of waters is based on sanitary surveys of water quality and shoreline surveys of pollution sources. When state managers close or otherwise restrict a shellfish growing area, they typically cite one or more sources of fecal coliform bacteria and other potential contaminants as the reason. In 1995, the discharge of partially treated sewage from malfunctioning on-site septic systems was identified as a principal or contributing factor in 32% of all harvest-limited growing areas. - Specific examples: - Indian River Lagoon, FL America s most diverse estuary, 156 miles long, making up 40% of Florida s Atlantic Coast. Tremendous population growth, accompanied by high nutrient levels, low dissolved oxygen and algal blooms. Septic systems are suspected as contributors of nutrients through ground water contact, as well as stormflow where hydraulic failures occur. Best estimates at this time indicate that septic systems are adding almost 1 ½ million pounds of nitrogen per year to the lagoon, making up 10% of the total nitrogen loading. - In Sarasota Bay (FL), septic systems are a major contributor of nitrogen to the Bay. Conventional septic systems are not designed to remove nitrogen, so so even properly functioning septic tanks are a source of pollution if they are located near

4 water bodies such as creeks, rivers, lakes, and bays. The Sarasota Bay Program reports that septic systems within 900 feet of surface water do not provide the same level of treatment as the City of Sarasota's wastewater-treatment plant. Over 45,000 septic systems in Sarasota County contribute four times more nitrogen to the Bay than the City of Sarasota s wastewater treatment plant. - Vermont: Discharging septic systems have been identified as one of the most prevalent sources of ground water contamination in the state, posing a serious health risk. The 1998 VT Nonpoint Source Assessment Report identified untreated waste from domestic septic systems as a source of pollution affecting nearly 90 miles of rivers and streams. In addition, 53 of 96 designated waterbodies have illegally discharging septic systems that contribute to nonpoint source pollution. - The Centers for Disease Control and Prevention (CDC) reports at least one source water outbreak of disease associated with sewage contamination. A total of 82 cases of shigellosis were identified resulting from source water contamination of a well at a resort in Island Park, Idaho in 1995 (MMWR, 1996). Nearby septic tanks or a leaky sewer line are the possible sources of contamination. - The largest ground water disease outbreak documented by CDC occurred in Georgetown, Texas in 1980 (Hejkal et al., 1982). About 7900 people became ill. Both Coxsackievirus and Hepatitis A virus were found in the raw well water and the outbreak was the result of source water contamination. The contamination source was never identified but the site is within an area of karst (solution-enhanced) limestone with cavernous zones which allows contamination to travel long distances in short periods with relatively little natural attenuation. Septic systems improperly designed or sited in such terrain can transmit untreated sewage over long distances. - In Racine, Missouri, 46 cases of hepatitis A were identified in 1992 at a non-community water supply in a karst limestone setting. A nearby septic system was identified as the contaminant source. - In Lancaster County, Pennsylvania, 49 cases of hepatitis A occurred in 1980 as the result of septic tank contamination of a well in a karst limestone area. - An outbreak resulting in 1200 cases of shigellosis occurred in 1974 (Wiessman, 1976) as the result of septic tank contamination of source water in a likely karst area in Florida. - Thin soils and fractured rock were in part responsible for a 39 case outbreak of illness at a northern Michigan resort island in An inadequate septic system was identified as the source that contaminated the raw water of the public water supply well. - A septic tank sited uphill from a well was the cause of 135 cases of illness due to Norwalk virus in 1986 at a South Dakota campground (MMWR, 1988). - New York: In the summer of 1999, nearly 800 people who attended the Washington County Fair in New York became ill. Dozens were hospitalized, and two died. Telephone surveys conducted in the weeks following the outbreak indicated that between 2,800 and 5,000 attendees may have developed gastrointestinal illness. Researchers at the New York State Department of Health strongly suspect that a septic system serving a nearby dormitory contaminated a fairgrounds well that provided water for mixing beverages

5 served to thousands of fair attendees. DNA analyses of bacteria samples from the septic system, the well, and those who became ill were indistinguishable. C:\WINDOWS\Temporary Internet Files\Content.IE5\DZ7GM1PL\factoids (1).wpd