Q. What's the difference between an
onsite
wastewater system, or OWS, and a septic system?
A. Onsite wastewater system (OWS) is a broad term referring to
any system for the collection, storage, treatment,
neutralization, or stabilization of sewage that occurs on
the property.
A septic system is a type of OWS, consisting of
a septic tank that collects all the sewage. The sewage
separates into a solid (sludge) that settles to the bottom,
and a liquid effluent that then flows into a leach field for
final treatment by the soil.
OWS are used to treat
and dispose of relatively small volumes of wastewater,
usually from houses and businesses that are not a part of or
connected to a sewage treatment works.
Regulatory definition: OWS - an absorption system of any size or flow or a
system or facility for collecting, storing, treating,
neutralizing, stabilizing, or disposing of sewage which is
not a part of or connected to a sewage treatment works.
Q. How does an OWS work?
A. There are two main parts to the basic OWS: the tank and the
drainfield.
The household wastewater flows into the tank
where the average detention time is 30 hours. The tank
should have at least 1,000 gallon capacity.
Three layers are formed in the septic tank.
There are baffles in the tank which keep the wastewater
flowing though the tank at a level near the middle of the
tank.
Solids settle to the bottom, forming a layer
of sludge.
The grease and foam float to the top, forming a scum layer.
Both the sludge and scum layers remain in the tank where
bacteria work to break them down. In time, the layers build
in size. When the layers become too large and take up too
much space in the tank, the tank needs to be pumped. Every 3
years, the tank should be pumped out by a licensed OWS
cleaner. If the system is not pumped out when it is full of
solids, the wastewater is not fully treated, and solid
material can be carried into the drainfield.
Solids in the drainfield can clog pipes and seal pores in
the soil. When the pores become sealed with solids, the water
no longer percolates as it should. The drainfield provides additional treatment of the
wastewater. In the drainfield, wastewater trickles though a
series of perforated pipes, though a layer of gravel, and
down though the soil. The soil and soil bacteria act as a
natural filters that help treat the wastewater.
Q.
How do I know if there is something wrong with my OWS?
A.
Home owners should be alert to the following warning signs
of a failing OWS:
- Test results of well water show the presence of bacteria.
- The ground in the area is wet or soggy.
- Grass grows greener or faster in the area.
- Sewage odors in the house or yard.
- Plumbing backups into the house.
- Slowly draining sinks and toilets.
- Gurgling sounds in the plumbing.
If one or more of these warning signs exist, the home owner
should contact a licensed OWS cleaner to have the system
inspected and pumped.
Q.
How can I find the location of my OWS?
A.
Boulder County Public Health issues permits and inspects
systems as they are installed. If your system was installed
during the last 20 - 30 years, we may have a sketch
of the layout of your system.
OWS cleaners can usually find the tank by using a soil probe
in areas where they would expect to find a tank. Tanks are
usually behind the house, near the bathroom, and about 10
feet away from the foundation.
Q.
Do I need to add anything to my OWS to keep it working
properly?
A. Many products claim to help the OWS work better or cleaner;
however, there is no magical potion to cure an ailing
system. Most engineers and sanitation professionals believe
that most of these products are unnecessary and are
potentially harmful to the system.
Some chemical products can cause soil pores to clog in the
field or add pollutants to the ground-water.
Bacteria, enzymes, and yeast products are usually harmless,
but are unnecessary because the wastewater will already contain
enough bacteria to break down the organic matter.
Q. How much will installing an OWS cost?
A. For exact costs associated with
design, installation, or cleaning an OWS, it is best to
contact the professionals involved directly.
A rough
range of potential costs would be from $6,000 - $30,000.
Costs are very dependent on specific site constraints and
sizing of the system. More
information on calculating cost.
Q. How do
I know if an OWS is currently permitted?
A. You may contact the Boulder County
Public Health, Water Quality Program at (303)441-1564 to
inquire about a system or
search for
your inspection record online.
Q. Why do
OWS fail?
A. Most OWS
failures are related to inappropriate design and poor
maintenance. Some soil-based systems (with a leach or drain
field) have been installed at sites with inadequate or
inappropriate soils, excessive slopes, or high groundwater
tables.
These conditions can cause hydraulic
failures and water resource contamination. Failure to
perform routine maintenance, such as pumping the septic tank
at least every 3 to 5 years, can cause solids in the tank to
migrate into the drain field and clog the system.
Q. What
items should not be put down the drain if my house has an
OWS?
A. Do not put the following items
into sink drains or toilets: hair combings, coffee grounds,
dental floss, disposable diapers, kitty litter, feminine
hygiene products, cigarette butts, condoms, gauze bandages,
fat, grease, oil, paper towels, paints, varnishes, thinners,
waste oils, photographic solutions, or pesticides.
Q. What should I do if my basement floods?
A. If sewage from your plumbing fixtures or
onsite system backs up into your basement, avoid contact
with the sewage and the possibly harmful pathogens it might
contain.
Contact Boulder County Public Health at
303-441-1564. Cleanup personnel should wear protective
clothing (e.g., long rubber gloves, face splash shields).
After cleanup is complete, all equipment,
tools, and clothing used in the cleanup and the flooded
basement area should be washed thoroughly and disinfected
with a mixture of 90 percent water and 10 percent household
bleach. The area should be dried out with fans, heat lamps,
or other devices, and should not be used until it has been
completely dry for at least 24 hours.
Q. Who do I
contact with questions or concerns about my OWS?
A. Boulder County Public Health’s
Water Quality Program can assist you and can be reached
at (303) 441-1564.
If your system needs to be serviced, contact
a OWS service provider.
Licensed OWS Professionals
Q. Do OWS cause health or water quality problems?
A. OWS
that are properly planned, designed, sited, installed,
operated, and maintained can provide excellent wastewater
treatment.
However, systems that are sited in densities
that exceed the treatment capacity of regional soils and
systems that are poorly designed, installed, operated, or
maintained can cause problems.
The most serious documented problems involve
contamination of surface waters and groundwater with
disease-causing pathogens and nitrates. Other problems
include excessive nitrogen discharges to sensitive coastal
waters and phosphorus pollution of inland surface waters,
which increases algal growth and lowers dissolved oxygen
levels.
Contamination of important shellfish beds
and swimming beaches by pathogens is also a concern in some
coastal regions.
EPA has developed guidelines to assist
communities in establishing comprehensive management
programs for onsite wastewater systems in order to improve water
quality and protect public health.
Q. How are OWS regulated?
A. In most states, local health
departments issue construction and operating permits to
install OWS under state laws that
govern public health protection and abatement of public
nuisances.
Some states are beginning to add water
resource protection provisions to their OWS regulations because of the possible impacts from
nitrogen and phosphorus.
Under most regulatory programs, the local
permitting agency conducts a site assessment to determine
whether the soils present can provide adequate treatment, to
ensure that groundwater resources will not be threatened,
and to stipulate appropriate setback distances from
buildings, driveways, property lines, and surface waters.
Some states permit alternative systems if
conventional soil-based systems are not allowable. Very few
permitting agencies conduct regular inspections of OWS after they are installed. County,
State, Federal Regulations
Q. What can
be done to improve OWS management?
A. The Environmental Protection
Agency (EPA) is partnering with federal agencies, states,
tribes, local governments, and nongovernmental organizations
to improve the management of OWS.
EPA's guidelines for managing decentralized
wastewater treatment systems can be tailored to meet the
needs of states, counties, tribes, cities, towns,
subdivisions, and other areas where OWS
might threaten public health or water resources.
The guidelines focus on the following areas
where better management can achieve significant improvements
in overall system performance:
- Planning to ensure that system densities
do not exceed the ability of regional soils and water
resources to treat and assimilate pollutants.
- Site evaluations that characterize and
help to protect soil, groundwater, and surface water
resources.
- System designs that provide predictable
performance levels of treatment that are appropriate for
protecting public health and the environment.
- Operation and maintenance procedures that
ensure that systems are operated properly and that
maintenance tasks (e.g., septic tank pumping, inspection
of treatment units) are performed regularly.
- Monitoring and reporting to provide usable
and easily accessible records on system inventories,
capacity, and performance.
- Follow-up and corrective actions to ensure
that failing systems are repaired, upgraded, or replaced
before public health or water resources are adversely
affected.
Q. Are there
organizations that can assist my community in addressing
onsite wastewater problems?
A. Boulder County Public Health’s
Water Quality Program can assist you and can be reached
at (303) 441-1564.
The National Small Flows Clearinghouse has a
technical assistance hotline that can be accessed toll-free
at (800) 624-8301, or at (304) 293-4191.
The Rural Community Assistance Program
provides assistance to communities having problems with
their OWS and can be reached at (888)
321-7227 or (202) 408-1273.
Q. How do I know if I am on the flood plain?
A. The City of Boulder is currently
creating a map of the flood plain near Boulder Creek.
Q. How do I show
that my OWS is adequate?
A. Systems that were installed without the
benefit of an engineer's design or a licensed installer are
extremely unlikely to conform to current standards that
ensure adequate treatment of sewage. However, you may
attempt to verify that the existing OWS is adequate by
following our verification procedure.
OWS Verification Procedure (PDF
15 KB)
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