Environmental Health
Surface Water (Lakes, Rivers & Streams)
Henderson WPA Septic System O&M Program
  Henderson Watershed Protection Area  

Septic System O&M Program — FAQs


If fecal bacteria is contaminating Henderson Inlet, how much is from septic systems?

DNA-typing studies have shown that human sewage is one of the sources of fecal bacteria pollution. Exactly how much or what percent of the pollution load is from septic systems is not known. There is proof that repairing failing septic systems has had dramatic success in improving water quality in Eld Inlet in Thurston County, as well as North Bay and Lower Hood Canal in Mason County.

Why aren't sewers being installed?

Sewer may be one of the solutions to on-site sewage system problems in some areas. However, sewers can only be installed within the Urban Growth Management Area (UGMA) as per the Growth Management Act. About forty-five percent of the Henderson watershed is outside of the area planned for urban growth. So on-site sewage systems will remain the method of sewage treatment and disposal in the rural areas and likely in at least some of the urban growth area.

Sewers are also expensive – construction and management of the sewage collection network, lift stations, and the treatment plants cost millions of dollars each year. In this community, new development pays for extending sewers into new areas. Neither the County nor the Cities have funds to pay for sewer extensions into previously developed areas. Special loans and grant funds, and local improvement districts (paid for by the property owners) would be needed to pay for extending sewers into existing neighborhoods.

Shouldn't I be more concerned with my well which is only 100 feet from my septic system, than Henderson Inlet which is miles away?

The 100-foot setback from a well is based on protection of groundwater, which flows differently than surface water and has layers of soil to penetrate before reaching the ground water. Often there is a protective layer, such as hardpan, that prevents surface contaminants from reaching the ground water. NOTE: If you have a shallow well, it is recommended to have it tested regularly.

The concern with a failing septic system is how readily can that sewage get into the water of Henderson Inlet, and what is the soil type (does water run over the surface and soak down into the ground).

Why are inspections and renewal certificates necessary?

Inspections and certificates are needed in order for septic systems to be properly maintained. There are many homeowners who carefully maintain their systems and are keenly aware of how to use the system to maximize its useful life. Unfortunately, that it not true for every system owner. So education programs and regulations help ensure that all systems are being inspected and maintained.

Pumping the tank is an important "insurance" policy to prevent a buildup of sludge and scum that could move out into a drainfield and cause clogging and failure. More complex septic systems have additional components that require continual oversight and care by a professional. Though residents may be well-intentioned, sometimes a reminder (every 3 years) to check things is what is needed.

Why not a one-time inspection of all septic systems in the program, then fix those that need repairs?

A one-time effort can have dramatic results, as in the case of Eld Inlet in Thurston County. However, 10 years later after all septic system evaluations were completed and repairs made, the water quality in Eld Inlet is once again declining. Regular inspection, maintenance, and repairs are key to keeping systems working and protecting water quality.

Will I have to pump my tank every year?

The majority of residential septic tanks in the Henderson Watershed Protection Area (HWPA) operation and maintenance program are evaluated every three years and pumped as needed. The septic tank pumper or homeowner (who has been certified to inspect their own system) can perform a “stick test” to determine if pumping is necessary. See Inspecting Your Septic Tank.

Does this mean County inspectors will be coming to my home?

Quality control inspections by County staff would happen on only 10% of systems, so they may never reach your house. High-risk systems must be dye tested every 6 years. The dye test is done either by County staff or a County-trained certified professional selected by the owner.

Why do systems installed in the last 5-10 years need monitoring?

Septic systems have many different components, such as septic tank, treatment unit, disinfection unit, pump, pump chamber and controls, alarm, sewer pipe, distribution box, and drainfield. Proper design siting, construction, installation, and maintenance are all critical pieces of the system.

However, even with the best of all those elements, a septic system can fail or cause pollution that a homeowner is absolutely not aware of. For example, pipes can crack, break, or pull apart due to the ground settling or shifting after construction, vehicle traffic, or even earthquakes. The result is that all the wastewater doesn’t go through all the treatment components of the septic system, but may leak instead into a foundation or roof drain that is routed to a stream or shoreline. Still other failures are caused by inadequate septic tank pumping or a broken baffle in the septic tank, which then allows solids and scum to flow out and clog the drainfield.

Additionally, homeowners and residents have a great effect on system performance. Using more water than the system was designed to handle can cause a failure. Also disposal of chemical or excess organic matter, such as that from a garbage disposal, can destroy a septic system. Good practices include:

  • avoiding the garbage disposal
  • spreading laundry out over the week
  • protecting drainfield area
  • using water saving fixtures on faucets and showers and low-flow toilets
  • pumping septic tank when needed

What if a septic system is failing?

The County has the responsibility to ensure that a failing system is repaired. A failing septic system is a violation of the County’s sanitary code. It is unsanitary and a serious public health concern to be discharging improperly treated sewage onto the surface of the ground, surface water, or ground water.

Not all failures require a new septic system be installed. Over 50% of system failures are caused by a component problem, i.e. cracked tank, broken building sewer line, improperly glued transport line, broken plumbing, etc.—all of which can cause untreated or partially treated sewage to reach surface water. Some systems have served their useful life and must be completely replaced. The owner is responsible for repairing problems or replacing failing systems. The County may be able to assist with the Loan/Grant Program.

How much is the program going to cost?

Annual fees for the program, as of January 1, 2012, are:

  • Low-risk Systems - $35 per year
  • High-risk Systems - $96 per year
  • Community Systems - $177 per year (Each parcel with an individual septic tank which is connected to the community system will also be charged either the low-risk or high-risk system fee, as applicable.)

Fees began in 2007 and appear on your property tax statement. Due to limited space on the Property Tax Statement, fees are included with the Stormwater Utility charge.

NOTE: For each subsequent year of the program, charges will be automatically adjusted each January 1 by the percentage increase in the June Consumer Price Index for the previous year. The maximum increase will be 3.5%.

What does the money collected pay for?

The costs are for operational expenses. Things such as system records, database management, educational workshops, dye testing, field operations, sending notices, issuing certificates, and system evaluations are paid for by the fees. Fees will cover the County’s responsibilities for this program.

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This page last updated: 04/01/22