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B-6029 TEX★A★Syst

Reducing the Risk of Ground Water Contamination by Improving Household Rural Water Treatment Assessment B.L. Harris, D.W. Hoffman and F.J. Mazac, Jr.*

1. Do you have an on-site wastewater disposal system (septic tank) on your land? 2. Is your septic tank less than 50 feet from a water well? 3. Has it been longer than 3 to 5 years (or one year if you have a disposal) since you have had your septic tank pumped out? 4. Do you dispose of grease, oils or leftover household chemicals down the drain? 5. Have you noticed wet or smelly areas in your yard? 6. Is your septic tank capacity too small to accommodate the number of people in your house- hold, or has an additional restroom been added to your home? 7. Do you have non- water entering your septic system or drain field?

If these questions create doubt about the safety of your management practices, this publication will provide helpful information.

*Professor and Extension Specialist; Research Scientist, Texas Agricultural Experiment Station; Extension Associate-, The Texas A&M University System.

Texas Agricultural Extension Service ¥ Zerle L. Carpenter, Director ¥ The Texas A&M University System ¥ College Station, Texas Household the household sewage lines into an under- ground septic tank. The following then occurs: Virtually all farms use a septic system or similar on-site wastewater treatment system. ★ The waste components separate, with the While these systems are generally economical heavier solids () settling to the bot- and safe, household wastewater can contain tom and the grease and fatty solids (scum) contaminants that degrade water quality for floating to the top. such uses as drinking, stock watering, food ★ Bacteria partially decompose and liquefy preparation and cleaning. the solids. Potential contaminants in household waste- ★ Baffles in the tank provide maximum water include disease-causing bacteria, infec- retention time of solids to prevent inlet tious viruses, household chemicals, and excess and outlet plugging, and to prevent rapid nutrients such as . Viruses can infect the flow of wastewater through the tank. liver, causing hepatitis, or infect the lining of the intestine, causing gastroenteritis (vomiting ★ The liquid portion () flows through and diarrhea). If coliform organisms (a group of an outlet on the septic tank to the indicator bacteria) are found in well water, the absorption field. water is potentially dangerous for drinking and ★ The absorption field is usually a series of food preparation. Septic systems are a potential parallel trenches, each containing a distri- source of this , as are livestock yards. bution pipe or tile line embedded in drain A properly installed and maintained system field gravel or rock. for treating and disposing of household waste- ★ The effluent drains out through holes in water will minimize the impact of that system the pipe or seams between tile sections, on ground water and . State and then through the drain field gravel or rock county codes specify how wastewater systems and into the soil. must be designed, installed and maintained. All new systems must be installed by a state ★ The soil filters remaining minute solids, certified installer and inspected by a state certi- some dissolved solids, and pathogens (dis- fied inspector prior to use. At a minimum, fol- ease-producing microorganisms). Water low the Texas Natural Resource Conservation and dissolved substances slowly percolate Commission codes for design and construction, outward into the soil and down toward but also consider whether the minimum ground water or restrictive layers. A por- requirements are sufficient at your site. tion of the water evaporates into the air, and growing over the drain field A glossary of terms at the end of this publi- lines utilize some of the water. cation will clarify terminology. This publication covers the following topics: Figure 1 shows a typical household system for wastewater generation, collection, treat- 1. Septic tanks/soil absorption systems ment, and disposal. While such systems may 2. Quantity of wastewater be called by various names (such as septic tanks or subsurface treatment and disposal sys- 3. Quality of wastewater tems), they are similar. In this discussion the 4. Collection of wastewater term septic tank is used. Note the list of options below each part of the diagram. You 5. Treatment systems may wish to circle the parts found in your sys- 6. Disposal system tem. The “leakage,” “overflow,” “infiltration” and “clearwater” components represent possi- 7. Assistance with failing systems or new ble problems with the system. Unfortunately, designs these problems are often difficult to recognize. 8. Evaluation table Over-flow from systems may be noticed as wet spots, and changes in vegetation cover. Septic Tanks/Soil Absorption Systems Water entry (infiltration and clear water) will be more difficult to detect. To help detect any The most common form of on-site waste- water entry, trace where the floors drain, the water treatment is a septic tank/soil absorption roof drains, the foundation drains, and where system. In this system, wastewater flows from sumps are directing outside water into the treatment system. Leakage from the collection assess. The flow chart at the bottom of the box and treatment system, as well as infiltration of follows the flow of wastewater and sludge water into the system through unsealed joints, through the treatment system. access ports and cracks, can be very difficult to

Excessive Water Use

EA GR SE Infiltration Problem Overflow Problem

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 Sludge Problem @@@PPPÀÀÀyyyyyyyyyyyy@@@PPPÀÀÀLeakage Problem

yyyy Clearwater Problem Water Supply*

Water Use Collection Pretreatment Additional Treatment Disposal Quantity* Leakage* Septic Tank* Sand Filter Soil Absorption* Quality* Clearwater* Holding Tank Removal In Ground Infiltration* Cesspool Disinfection Bed Aerobic System Trench Mound, At Grade * = Elements Illustrated and Haul

Figure 1. Typical household wastewater treatment system with problems. Illustration by Andy Hopfensperger, University of Wisconsin-Madison Department of Agricultural Engineering. Quantity of Wastewater ★ Wash full loads of clothes to save soap and water. Front loading washers use much The best strategy is to minimize the volume less water. When running small loads, be of household wastewater entering the treat- sure to use the reduced water level set- ment system. This is important because less ting. flow (volume) means better treatment, longer system life, and less chance of overflow. Less ★ Use modern, efficient fixtures volume also lowers costs by reducing the num- and appliances, including 0.5- to 1.5-gallon ber of times the holding tank must be emptied. , 0.5- to 2.0-gallons-per-minute (gpm) showerheads, faucets of 1.5 gpm or The quantity of water used depends upon less, and front loading washing machines the number of people using the dwelling, their of 20 to 27 gallons per 10- to 12-pound dry water use rates, and the maintenance of the load. These fixtures and appliances can water supply system. Average water use in reduce water use from 30 to 70 percent rural households is 40 to 50 gallons per person (see Fig. 2.). per day. With low-use fixtures and individual awareness and concern, a reduction to fewer ★ Use water softener devices with care, be- than 25 gallons per person per day is possible. cause they may use significant amounts of However, even conservative use by several peo- water. Proper adjustment and timing of ple may exceed the capacity of the wastewater the softener’s regeneration mechanism can treatment system. reduce excessive water use. The flush backwash should not go to your septic Reducing the volume of water entering the tank. system will improve treatment by increasing the time the waste spends in the system, thus ★ Eliminate household water leaks. A leak in providing more time for settling, decomposi- the home may be detected by opening the tion, aeration and soil contact. cleanout (usually located between the house stub-out and the septic tank) and Consider the following ways to minimize checking for a continuous flow through water use. the pipe to the septic tank. Since a small ★ Eliminate non-functional uses, such as flow is sometimes difficult to see, you flushing toilets to dispose of tissues or should drop a pinch of sand into the pipe other waste that should be handled as and watch to see if the sand is carried solid waste. Turn off water between uses, away. If the sand is carried away, you have fix plumbing fixture leaks, and try to elim- a continuous leak inside the home. To iso- inate sources of clear water infiltration late the leak, check each fixture. If a leak- into the system. (For example, divert roof ing is suspected, put a small amount drains away from the soil absorption of food coloring into the toilet and check field.) to see if it appears in the flow through the cleanout. ★ Consider which actions use the most water. Toilet flushing usually ranks the ★ Prevent water from other sources from highest. Low-flow models could decrease entering either the septic tank or the drain water use by more than half. Composting field. Divert water flowing from roof toilets allow even greater reductions, but drains away from the septic tank and they can present other waste disposal away from the drain field. Construct a challenges. berm or a swale upslope of the drain field if there is flowing down- ★ Bathing and washing clothes are next in slope over the drain field. However, avoid order of water use. Consider installing diverting the runoff toward your well. low-flow or controlled-flow showerheads, which give good cleansing with less water; ★ Do not allow water from basement floor taking shorter showers; and taking “wet- drains or foundation drains to enter the down-soap-up-without-water-then-rinse” septic tank through the house plumbing. showers. Keep in mind that your family’s awareness of your water use and how it can be reduced is as important as the use of devices. Vent

Electric Motor Outlet

Inlet

Aeration Compartment

Settling Air Compartment Discharge

Mixing Return Sludge Return

Figure 2. Aeration tank of a household . Source: Onsite Domestic Sewage Disposal Handbook, MWPS-24, Midwest Plan Service, 1982

Quality of Wastewater ★ High oxygen demand can lower water quality. The microorganisms that decom- Domestic wastewater usually contains rela- pose organic wastes (such as blood, milk tively small amounts of contaminants — less residues and garbage grindings) use lots of than 0.2 percent (i.e., it is 99.80 percent “pure” oxygen. The amount of oxygen required to water), but even small amounts of contami- “stabilize” wastewater is typically mea- nants can make a big difference in the useful- sured as biochemical and chemical “oxy- ness of the water. gen demand.” Aeration and digestion Contaminants found in wastewater include processes, in the presence of oxygen and the following: organisms, produce stable, low- wastewater when given enough time. ★ Bacteria and viruses, some of which can However, wastewater with excess oxygen cause disease in humans. These microor- demand can cause problems for soil ganisms are large enough to be removed absorption fields, ground water, streams by settling, or through in sand and lakes by reducing levels of oxygen in beds or soil. Many will die as they pass the water. through the system. ★ Organic solvents from cleaning agents and ★ Suspended solids are particles that are fuels may not be degraded or removed more dense (sludge) or less dense (scum) through treatment and can pass along than water and that can be removed by with the wastewater back into the water filtration. Most can be separated from liq- supply. uid waste by allowing enough time in a relatively calm tank. Grease and fats are a ★ Nutrient contaminants are composed part of the suspended solids. Filtration mainly of nitrogen from human wastes, beds and absorption systems can be phosphorus from dish washer detergents clogged by wastewater high in suspended and some chemical water conditioners. solids. Nitrate-nitrogen is a common ground water contaminant, and phosphorus is a additional treatment or disposal, for example, common contaminant of surface water. in the soil absorption field. Here are some ways to improve wastewater The design and construction of septic tanks quality: influence their water tightness and effective- ness at retaining sludge and scum. Multiple ★ Minimize use of the garbage disposal unit. tanks or chambers in series can improve sludge Garbage disposals deposit large amounts and scum removal. Gas deflectors and filter of suspended solids and organic matter screens or inclined-plate settling units help to into the septic system, as well as using minimize solids entering the drain field. Tanks additional water. should be sized to accommodate at least 24 ★ Do not clog septic tanks by putting items hours of wastewater flow while still allowing such as fats, grease, coffee grounds, paper for sludge and scum retention. Pumping the towels, sanitary napkins, tampons or dis- tank before it is more than one-third filled with posable diapers down drains. scum and sludge (generally every 3 to 5 years) improves the functioning of the system. When ★ Do not put toxic substances in drains. the tank is pumped, you should have the baf- They might end up in the ground water. fles checked and also check for tank leaks. These include solvents, degreasers, acids, Septic tanks should be made of reinforced con- oils, paints, disinfectants and . crete, or prefabricated fiberglass. However, this does not prohibit the use of to disinfect laundry or the washing Aerobic (oxygen using) biological systems, of clothing worn for applications. which are considered packaged systems, treat wastewater better than the typical anaerobic ★ Do not use chemicals to clean your sys- (no oxygen) septic units, thus improving solids tem. They may interfere with the biologi- separation, releasing volatile chemicals, and cal action in the tank, clog the drainfield reducing sludge volume. These systems are, by flushing sludge and scum into the field, however, more expensive to operate and main- or add toxic chemicals to ground water. tain and are more often subject to problems caused by changes in wastewater quality or Collection of Wastewater environmental conditions. Aerobic systems are Collect all waste that needs treatment and often used because they produce high quality minimize the loss of untreated waste. Leaking effluent which may be disposed of through pipes or treatment tanks can allow wastewater conventional trenches or drip , or to return to the local water supply without ade- sprayed on top of the ground. quate treatment. Exclude from the treatment If you have an aerobic system, you should system water that does not need treatment or have a maintenance person inspect the unit disposal. three times each year. The maintenance person Infiltration of clear water overloads the sys- should check the aeration mechanism, the dis- tem and dilutes the wastes. Do not allow rain- infection unit (tablet chlorinator), and other water or water from basement floor drain critical aspects of the unit. sumps, foundation drains or roof drainage to Between inspections you should check the add to your waste water volume. Divert clean tablet chlorinator for chlorine tablets. If there water away from the house, any , and any are no tablets, fill the chlorinator immediately. wastewater treatment system. An empty chlorinator increases the chance that disease causing organisms will come into con- Treatment Systems tact with people. Make wastewater suitable for treatment and Additional treatment after wastewater has disposal in the soil by reducing the concentra- passed through the septic system can reduce tion of contaminants in the wastewater. the concentration and amount of contaminants in the wastewater and make it suitable for dis- Septic tanks retain most of the suspended posal. solids (sludge) and scum from wastewater. In the tank, bacteria digest and compact the Aerobic systems may be used for additional sludge. The partially treated water moves to treatment of septic tank effluent, and these sys- 6"

Distribution Lines. 3" o.c.

Collection Line

Distribution Lines. 3" o.c. Observation Pipe

PLAN VIEW Soil Cover Observation Pipe

Rock

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yyyyyyyyyyyy Gravel Collection Line Rock Plug SIDE VIEW Slope 6" / 100' yyyyyyyyyyyy 1/4" Screen 12" max Soil Observation and 10" Rock 24" Sand Ventilation Pipe yyyyyyyy 3" Pea Gravel 6" Rock over Pipe

yyyyyyyy 10' max to next collection line

END VIEW

Figure 3. Buried sand filter. Source: Onsite Domestic Sewage Handbook, MWPS-24, Midwest Plan Service, 1982. tems can yield a better quality effluent suitable tenance includes resting, occasional raking, for more disposal options. removal of clogged or crusted surface media, filter media replacement, and attention to dos- Sand filters also improve the quality of ing equipment. wastewater after septic tank pretreatment. Effective treatment involves aerobic biochemi- Wastewater treated in such systems is gener- cal activity as well as physical filtration. Filters ally lower in bacteria, nitrogen, phosphorus, consist of 2 to 5 feet of sand (or other media) in oxygen demand, suspended solids and organic a bed equipped with a distribution and collec- matter. The amount of reduction depends on tion system. Wastewater is applied by dosing, the design of the system. and it may be recirculated to improve treat- A disinfection unit is a system that kills dis- ment. ease-causing microorganisms in wastewater, Filters should be designed according to the and is used when discharge on the surface is pretreatment system used, the quality of the permitted. Chlorine, iodine, and ultravio- wastewater, the hydraulic loading rate, the dos- let light systems are available to treat good ing frequency, the temperature, and the distrib- quality effluent, such as that from properly ution and collection systems used. Filter main- functioning aerobic units and sand filters. Disposal Systems ★ The application of effluent in a surface treatment system should not produce To reduce the risk of wastewater contaminat- runoff or ponding. ing water supplies, disperse effluent and maxi- mize its contact with soil and . ★ Spreading the effluent over a larger sur- face area promotes maximum vegetative Discharging treated or untreated wastewater uptake of nutrients. The entire application from private systems directly to surface waters area should be covered with vegetation so or ditches is illegal in Texas. Illegal wastewater that most of the effluent will encounter discharges or wastewater surfacing above the plant roots before reaching ground water. drain field can endanger your health as well as The plant roots will utilize many of the the health of others in your community. nutrients in the wastewater. Subsurface Treatment Systems Assistance with Failing Systems Subsurface treatment and disposal, using soil absorption systems (trenches, beds, or or New Designs mounds), is the common disposal system fol- If you suspect your household wastewater lowing septic tanks. There are, however, sites treatment system is backing up or your distrib- where soil absorption systems will not function ution system is clogged, first contact a plumber properly and will endanger ground water quali- or treatment system installer, who may have ty. Unsuitable sites are those with impermeable suggestions for extending the life of your sys- soils, shallow rock, shallow water tables, or tem. The county public health office is the very permeable soils such as a sand or gravelly location to visit for permits to repair or replace soil. a wastewater treatment system. Take the fol- Suitable sites are those with deep, well- lowing steps to reduce any risk of contaminat- drained, well-developed, medium-textured soils ing ground water: (such as silt loam and loam). Soil beneath the ★ Do not use septic tank cleaners that con- disposal area must be unsaturated to provide tain degreasing solvents such as TCE, adequate treatment. Unsaturated soil allows which can contaminate ground water. the effluent to remain aerobic and to flow through tighter soils, thereby filtering contami- ★ Do not place more soil over a surfacing nants and giving soil microbes longer contact soil absorption field; this does not fix the time with soil organic matter. Approximately 4 system, and water will surface again. feet of unsaturated soil should be maintained ★ Do not pipe sewage to the road ditch, beneath the disposal system to adequately storm sewer, sink hole, drainage well, remove pathogens and organic matter from stream, or drain tile; this pollutes the wastewater. water and creates a health hazard. Disposal systems that are downslope and far ★ Do not wait for the system to fail before from the water well will better protect your pumping the septic tank. Once a system water supply from possible contamination from fails, it is too late to pump the tank. wastewater. ★ Remember that spreading the effluent Surface Treatment Systems over a larger area and placing the effluent shallower in the soil will decrease the When compared to subsurface treatment sys- chance of contaminating your water sup- tems, surface treatment systems promote more ply. evapotranspiration (removal of effluent by evaporation and loss through plants). Increased A properly designed, constructed and main- evapotranspiration decreases the amount of tained septic system can effectively treat waste- treated effluent that can reach the water sup- water for many years, but it requires routine ply. However, disposal systems that apply the maintenance. For additional information on treated effluent directly on the ground surface septic systems, contact your county Extension must have an approved method of treatment agent, local health department, or Texas and should disinfect the effluent before appli- Natural Resource Conservation Commission cation. Keep the following application strate- On-Site Wastewater/Agricultural Division (512) gies in mind: 463-8260. Evaluation Table read across to the right and circle the state- ment that best describes conditions on your The following table can be used to help agri- land. Allow 15 to 30 minutes to complete the cultural producers and rural homeowners table, and skip any categories that do not determine the risk that drinking water on a apply. Note any high risk ratings and take given property may be contaminated because appropriate actions to remedy them. Strive for of the management practices being used. For all low or low-moderate risk ratings. each category on the left that is appropriate,

Assessing the Risk of Ground Water Contamination from Household Wastewater Treatment Low Risk Low-Moderate Risk Moderate-High Risk High Risk Quality of Wastewater Internal water use Conservative water Moderate water use. High water use. Use Excessive water use. Use water- Use a few water- very few water-con- use. Use no water- conserving fixtures. conserving fixtures. serving fixtures. conserving fixtures, Routinely check for Periodically check for Rarely check for and never check for and repair leaks. and repair leaks. repair leaks. Water and repair leaks, Water softener re- softening recharges and water softening recharges are infre- charges to septic tank to septic tank more recharges to septic quent or not connect- twice per week or less. than twice per week. tank more than ed to septic tank. twice per week. Unnecessary water No inflow. Rain-water Moderate inflow. Rain- High inflow. Neither Excessive inflow. entering treatment runoff and roof drains water runoff and roof rainwater runoff nor Rainwater runoff or disposal system are diverted away drains are diverted roof drains are divert- and roof drain flow from septic tank and away from septic tanks ed away from the directly over septic disposal area. The and disposal area. drain field and septic tank or drain field. basement or founda- However, the system tank. The septic Septic tank tion drain is not con- does receive water tank receives water receives flow from nected to the system. from either foundation from basement or foundation and or basement drains. foundation drains. basement drains. Quality of Wastewater Solids No use of garbage Minimal use of gar- Moderate use of gar- Daily use of gar- disposal unit in bage disposal (1 to 2 bage disposal unit (3 bage disposal unit. kitchen sink. times per week). to 5 times per week). Chemicals Minimal use of house- Careful use of house- Moderate use of Extensive use of hold chemicals (cups hold chemicals (pints household chemicals household chemi- per week). No dis- per week). Minimal (quarts per week). cals (gallons per posal of solvents and disposal of solvents Moderate disposal of week). Extensive toxic cleaning agents. and toxic cleaning solvents and toxic disposal of solvents No water softener or agents. Water softener cleaning agents. and toxic cleaning not recharged on site. used, recharged on agents. site. Oils/Grease No disposal of grease Minimal disposal of Moderate disposal of Extensive disposal or oils into sewer. grease/oils. Oil and grease/oils. No of grease/oils. Domestic wastes only. grease wiped from attempt to reduce cooking utensils disposal of grease/oil before washing. from household, but little generated. Pretreatment System Cesspool (these are Any cesspool, illegal systems) direct discharge of water, or seepage pit. Assessing the Risk of Ground Water Contamination from Household Wastewater Treatment Low Risk Low-Moderate Risk Moderate-High Risk High Risk Pretreatment System (continued) Septic tank More than one tank in One tank or one-com- Metal or cinder block Any homemade de- series or two-com- partment tank. Tank tank. Total liquid vices, particularly partment tank. Tank made of reinforced capacity less than with small volumes. made of reinforced , polyethene 500 gallons. Tank is Tank or device has concrete. Liquid or fiberglass. Liquid pumped every 7 or never been capacity of tank is capacity of tank is less more years. pumped. equal to or greater than 300 gallons times than 300 gallons the number of bed- times the number of rooms. Tanks pumped bedrooms. Tanks every 5 years. pumped every 3 years. Packaged aerobic Maintenance program No maintenance pro- No maintenance, No maintenance, system followed. gram, but no notice- occasional failures. frequent system able failures. failure. Tablet chlorinator Chlorine tablets pre- Chlorine tablets are Chlorine tablets are No chlorine is in sent. Strong chlorine disintegrated and disintegrated and chlorinator and no smell. caked on walls, but a caked on walls and chlorine smell is chlorine smell is no chlorine smell is present. present. present. Disposal of Wastewater Horizontal separa- Offsite disposal. Subsurface disposal Subsurface disposal Upslope from well. tion of wastewater downslope more than downslope less than disposal site from 50 feet from well. Sur- 50 feet from well. water supply (sub- face disposal more Surface disposal less surface or surface) 200 feet from well. than 200 feet from well. Vertical separation Offsite disposal. More than 6 feet to 3 to 6 feet to saturat- Less than 3 feet to of wastewater dis- saturated soil or bed- ed soil or bedrock. saturated soil or posal site from rock. bedrock. water supply (subsurface) Soils Offsite disposal. Medium- or fine-textur- Medium-to coarse- Very coarse sands ed soils (silt loam, textured soils (sandy or gravel. loam, clay loams, clay). loam, sands). Subsurface disposal Pressurized system Pressurized system Gravity system with Gravity system with system which uniformly which uniformly applies shallow trenches. deep trenches or applies effluent effluent throughout There is healthy bed. There is little throughout entire entire field. Deep vegetation above vegetation above field. Shallow trenches or bed with- trenches and vege- trenches or bed. trenches or bed out covering of healthy tation is regularly covered with healthy vegetation. harvested. vegetation. Vegetation harvested regularly. Surface application Irrigation area is Irrigation area is Irrigation area has Irrigation area is disposal system covered with healthy covered with healthy bare spots and it totally bare and is vegetation. Vegetation vegetation. Vegetation appears that irriga- producing channel- harvested regularly. is rarely harvested and tion is producing ized runoff from the Area appears to pro- it appears that irriga- runoff. site. duce little or no run- tion is producing run- off. off. *See Glossary. Glossary Off-site disposal: Disposal of wastewater or sludge at a municipal treatment plant or Approved disposal site: A site for land appli- other approved disposal site. cation of wastewater or tank pumpage that meets state standards of the Texas Natural Scum: Floatable solids, such as grease and fat. Resource Conservation Commission Seepage pit (): Underground recepta- (TNRCC). cle constructed to permit disposal of septic Cesspool: Covered excavation in the ground tank effluent, treated wastes or clear wastes that receives sewage directly from a build- by soil absorption through its bottom and ing’s sanitary drainage system. It is walls. Seepage pits are not allowed for con- designed to retain the organic matter and struction and/or use in the state. They are solids and to permit liquid to seep into the considered unsuitable on-site wastewater soil. Cesspools are not allowed for construc- disposal methods. tion and/or use in the state. They are con- Sludge: Settleable, partially decomposed solids sidered unsuitable on-site wastewater dis- resulting from biological, chemical or physi- posal methods. cal wastewater treatment. Clear water infiltration: Entry of water that does not need treatment into a treatment Contacts and References system; clear water may enter through tile drainage, unsealed joints, access ports and For additional information, contact your cracks. local county Extension agent, or: Design capacity: Maximum volume of liquid ★ The Texas Natural Resource Conservation that can be treated in a particular waste- Commission at (512) 239-1000, water treatment system. For systems that ★ Texas Agricultural Extension Service include subsurface wastewater disposal and Agricultural Engineering unit (409) 845- distribution, capacity is also based on the 7451, soil’s ability to accept and treat sewage effluent. In filling out the worksheet, if you ★ Texas Agricultural Extension Service Water do not know the design capacity of your Quality unit (409) 845-0887, system, use 150 gallons per bedroom per ★ Texas State Soil and Water Conservation day as an estimate. Board, (817) 773-2250. Effluent: Liquid discharged from a septic tank Internet address: TEX*A*Syst bulletins and or other tank. links to other water quality sites are contained Holding tank: An approved watertight recep- in a homepage located on the World Wide Web tacle for collecting and holding sewage. at: http://waterhome.tamu.edu. Hydraulic loading rate: The volume of waste discharged per unit area per unit time.

TEX*A*Syst is a series of publications to help rural residents assess the risk of ground , and to describe Best Management Practices (BMPs) that can help protect ground water. The TEX*A*Syst documents were developed from the national Farm*A*Syst ground water protection program. The TEX*A*Syst system is designed to help the user learn more about the environment, existing environmental policies and regulations, and recommended management practices. Thus, the user can voluntarily reduce the pollution risks associated with water wells.

TEX*A* Syst materials were edited by Anna Schuster Kantor, and reviewed by M.C. Dozier and the personnel of the USDA-Natural Resources Conservation Service, U.S. Environmental Protection Agency, Texas Department of Agriculture, Texas Natural Resource Conservation Commission, Texas Water Development Board, Texas State Soil and Water Conservation Board, Texas Water Resources Institute, and Texas Farm Bureau. Editorial and formatting assis- tance were provided by the Department of Agricultural Communications, The Texas A&M University System. The TEX*A*Syst program is sponsored by the U.S. Environmental Protection Agency under Section 319(h) of the Clean Water Act. Funds for this program are administered by the Texas State Soil and Water Conservation Board’s Agricultural/Silvicultural Nonpoint Source Management Program.

Educational programs of the Texas Agricultural Extension Service are open to all people without regard to race, color, sex, disability, religion, age or national origin. Issued in furtherance of Cooperative Extension Work in Agriculture and Home Economics, Acts of Congress of May 8, 1914, as amended, and June 30, 1914, in cooperation with the Department of Agriculture. Zerle L. Carpenter, Director, Texas Agricultural Extension Service, The Texas A&M University System. 10MÐ6-97, Revised E&NR 5