Home > Sewage Disposal > Septic Systems          

Septic Systems and Design Standards in Santa Cruz County

History of Septic System Repair Regulations in Santa Cruz County

Santa Cruz County has over 22,000 septic systems, 13,000 of which are in the San Lorenzo River Watershed. The San Lorenzo Watershed has the highest density of septic systems of any comparable area in the State. The majority of septic systems in the county are over 25 years old and are located on parcels that could not fully meet today's standards for installation of a new septic system due to small lot size, close proximity to a stream, high groundwater, steep slope, or clay soil. Many of these systems have already been repaired or replaced at least once. However, many of the repairs were done prior to 1980 when there were little or no standards for septic system repairs. There were no minimum size requirements and systems were allowed to go in very deep, with little regard to soil conditions or winter groundwater levels.

Poor septic system conditions in the San Lorenzo Valley during the 1970's and early 1980's led to frequent failures, high bacteria levels in the River and elevated nitrate levels which threatened the City of Santa Cruz water supply. As a result, in 1982, the Regional Board stepped in and issued Resolution 82-10, an order prohibiting any new development and prohibiting the continued use of existing septic systems in the San Lorenzo Valley. The State wanted the area sewered. But, in 1985, the proposed sewer project failed due to high cost, lack of grant funds, and substantial disagreement in the community about whether sewers were really needed. In spite of this, the State still felt sewers were needed and the prohibition on septic systems remained in effect.

In 1986, County Environmental Health proposed a compromise solution, whereby septic systems could be allowed to continue to be used, provided that they were upgraded over time to meet a minimum set of standards necessary to improve the water quality in the River. The County would provide ongoing inspection of systems and water quality monitoring to ensure that immediate problems were found and corrected. The Valley community supported this idea and the program has been in place since 1986. However, it took a lot of time and demonstration of good results before the State was willing to lift the prohibitions. The State also insisted that the repair standards be made more stringent than the County originally proposed, particularly with regard to minimum groundwater separation. In May, 1995, the State Regional Board lifted the septic system prohibitions and adopted the San Lorenzo Wastewater Management Plan, including the repair standards as they substantially are today.

Since the County began the program in 1986, septic system failure rates have dropped from 15% to 5%. Some 2300 systems have been repaired and 85% of these have been able to fully meet the repair standards for standard system. Although water quality in the River has improved somewhat and the failure rates have declined, ongoing efforts among the County, the contractors and the property owners, will be needed to upgrade the rest of the systems over time. Repair of most of these systems will be relatively straight forward. However, some 5-10% of the system upgrades will present major challenges for the owner, the designer, the contractor, and County staff to design and install a workable system that meets minimum requirements for protection of water quality.

How Septic Systems Work

Septic systems (also known as onsite sewage disposal systems or individual sewage disposal systems) are the primary method for treating and disposing sewage in rural areas where sewer systems are not available or too expensive to install. Septic systems are designed to provide partial treatment of the sewage, with disposal to the soil in such a manner that the sewage stays under the ground and is further treated by soil organisms so that contaminants do not reach groundwater or streams.

A septic system typically consists of a septic tank and a leaching device. The tank is usually 1000-2000 gallons in size and is designed to trap solids and grease and provide initial, primary treatment of the sewage. Treatment in the septic tank is anaerobic (without oxygen) and produces a fairly raw effluent that is still very high in bacteria and pathogens, dissolved solids and organics, ammonia, and organic nitrogen. The sewage then typically flows by gravity to the leaching device where the sewage soaks into the soil and most of the treatment takes place. Good treatment is primarily a biological process and it occurs most rapidly in upper soil layers that are rich in soil organisms (bugs) with plenty of oxygen to provide aerobic treatment.

Leaching devices typically consist of perforated pipe set along the top of one or more gravel-filled trenches (leachfields). The sides and bottom of the trench below the level of the perforated pipe provide the absorption area for the effluent to soak into the soil. The total amount of trench and absorption area needed is determined by the expected amount of sewage flow into the system and capabilities of the soil to absorb water. A sandy soil requires less absorption area than a clay soil. The effective depth of a trench is the depth of the trench below the distribution pipe. Because the pipe is covered with soil and typically laid 1-2 feet below the soil surface the total depth of the trench is usually 1-2 feet greater than the effective depth.

Besides the basic tank and trench leaching device, an onsite sewage disposal system may include other components:

A pump chamber and pump may be used to send the sewage to a higher, more suitable disposal area on the property. (Pump systems include extensive electrical controls, alarms, and excess storage capacity to ensure proper timing of pumping and safeguards in the event of power failures, pump breakdowns, or system overloading.)

An effluent filter may be set in the tank to help ensure that solids don't escape from the tank to clog the leaching device.

Inspection Risers are vertical pipes which extend from the bottom of the leaching device to above the ground surface which can be opened and inspected to determine the level of the effluent in the trench.

A distribution box or flow divider ensures that the sewage is evenly distributed to all parts of the leaching system. If this is not installed properly, one part of the system can be overloaded and fail, while other parts remain dry.

A diversion valve is used in older systems to cut off the flow of sewage to part of a leachfield, potentially allowing it to rest or recover while the other part of the leachfield is being used.

Pressure distribution systems may be used in conjunction with pumps to deliver sewage under pressure evenly to all parts of the leaching device.

Chamber leaching devices may be placed in trenches instead of gravel and perforated pipes. An example of this are the Infiltrator devices.

Enhanced treatment units may be used in place of or in addition to the septic tank to provide a much higher level of effluent treatment before the sewage is discharged to the soil. Examples of these are sand filters, or proprietary devices such as Multiflo units, Microfast Systems, Clearwater Systems.

Mounded Bed Systems or At-grade systems are engineered leaching devices which provide for sewage disposal right at, or above the natural ground surface for use in areas where there are high groundwater levels.

Seepage pits are leaching devices that consist of a circular pit 3-4 feet in diameter drilled 20-40 feet into the ground.

Greywater Sumps are small leaching devices designed to dispose of sewage from clothes washers, sinks, showers, or other sources that do not contain toilet waste (blackwater).

A haulaway system is used where standards for in ground sewage disposal cannot be met. Sewage is contained in a holding tank for regular removal by a septic tank pumper.

How Septic Systems Don't Work

A septic system is obviously not working properly if untreated sewage comes out on the surface of the ground or if it backs up into the house. This is known as a failure. Septic systems are also not working properly if contaminants such as bacteria or nitrate from those systems are reaching groundwater or surface water in excessive amounts. A system is close to failure if the leachfield inspection risers show that the leachfield is completely full of a sewage. This condition also limits adequate treatment.

Following are some of the factors that contribute to septic system failure or improper function:

- Age -As a septic leachfield ages, the soil surfaces in the leaching device become clogged with an organic scum layer which limits the ability of the sewage to soak into the soil. The trench or pit fills up and untreated sewage comes out on the ground surface or backs up into the drains in the house. This clogging process usually takes place over a period of 10-40 years and works from the bottom of the trench up to the top. Standing effluent levels in the riser can give an indication of how much usable trench is left. The clogging process is speeded up by system overloading, saturation by groundwater, or lack of septic tank pumping which allows solids to enter the leaching device. Once a leaching device is clogged, it generally needs to be replaced, although some temporary or partial restoration may be gained by resting a leachfield or treating it with an oxidizing agent. In addition to the aging process, older septic systems tend to be undersized and too deep because they were installed prior to development of septic standards.

- Poor Maintenance or Overloading - Inadequate pumping of the septic tank, use of damaging chemicals, or overloading the system by excessive wastewater discharge can inhibit the treatment process and/or contribute to premature system failure.

- High Groundwater can cause septic failure or contamination of groundwater and surface water. In many parts of Santa Cruz County, groundwater levels rise significantly during the rainy season, often coming within 1-6 feet of the ground surface for at least several weeks. If a leaching device is flooded by groundwater, it greatly limits the ability of the sewage to soak into the ground and a failure may occur. If sewage enters groundwater before it has been adequately treated in the soil, bacteria, virus, and pathogens can contaminate wells or nearby streams. Studies in the San Lorenzo Valley have shown very high levels of bacteria within 25-50 feet of leachfields that penetrate groundwater. In some studies, pathogenic viruses have been shown to travel several hundred feet under high groundwater conditions. However, where soils are not saturated, it has been found that bacteria and virus are reduced to safe levels within only 2-5 feet of a leachfield.

- Poor Surface Drainage If roof runoff or surface runoff is allowed to flow into a leachfield area and soak into the ground, it can rapidly saturate the soil and cause the leachfield to fail.

- Clay Soils cannot absorb sewage as rapidly as sandy or loamy soils and they become saturated more easily during winter months. Leachfields must be much larger in clay soils or they will become saturated, overloaded and fail.

- Sandy Soils absorb effluent more easily and are less prone to sewage failures. But the sewage moves through very rapidly and does not receive as much treatment. Studies in the San Lorenzo Valley have shown that septic systems in sandy soils contribute 10-15 times as much nitrate to groundwater as systems in other types of soils.

- Steep Slopes and Cuts - Leachfields cannot be located too close to cuts or on steep slopes as there is a danger that the sewage can seep laterally out of the slope or cut before it has a chance to be fully treated. Septic systems can also cause slope failures if located in unstable slopes.

How Septic Systems Are Regulated

The State and County have several regulations to prevent septic systems from causing pollution or presenting a serious public health hazard. The State Health and Safety Code requires an appropriate means of sewage disposal for all homes and businesses. It also prohibits any discharge of sewage on the ground surface. The Health and Safety Code designates the County Health Officer as the person for ensuring proper sewage disposal in the county. The Health Officer delegates these responsibilities to the Environmental Health Service.

The State Regional Water Quality Control Board (Regional Board) is responsible for ensuring that septic systems do not cause pollution of surface or groundwater. The Regional Board has developed many standards for proper septic system installation, including: groundwater separation, stream and well setbacks, slope limitations, minimum system sizing requirements, and allowances for use of alternative technologies. These standards are contained in the Water Quality Control Plan for the Central Coast Region (Basin Plan). All the provisions of the San Lorenzo Wastewater Management Plan have also been adopted into the Basin Plan. The Regional Board has conditionally delegated authority to oversee and regulate the installation of septic systems to the County Environmental Health Service through a memorandum of understanding. The County must comply with the minimum standards contained in the Basin Plan in order to keep the authority to permit septic systems.

The County Board of Supervisors has adopted Section 7.38 of the County Code (the Sewage Disposal Ordinance) which specifies the standards for septic system installation in Santa Cruz County. In addition to the standards for new or expanded septic systems, the Code allows some specific reduction of standards for the repair of existing septic systems. Environmental Health has developed a specific set of Standards and Procedures for the Repair and Upgrade of Septic Systems. Many critical parts of these standards were developed through negotiations between the County and the Regional Board as a condition of lifting the Regional Board's prohibition on septic systems in the San Lorenzo Valley. Environmental Health also has developed other policies and procedures for implementation of the Sewage Disposal Ordinance. In the last five years these policies and the repair standards have been circulated to consultants, contractors and members of the Board of Supervisors for input at least 30 days prior to implementation.

Any installation, replacement, or significant repair of any part of a septic system requires a permit from Environmental Health. The proposed work is designed by a consultant, septic contractor, or the property owner, and described on the septic permit application form and a detailed plot plan. Environmental Health staff review the application and relevant information for the area on soils, groundwater depth, and site conditions in order to determine that the proposal meets the standards as established by the State and the County. If inadequate information exists, additional soil or groundwater testing may also be needed prior to approval of the application. Once the application is approved, the Environmental Health Inspector conducts several progress inspections of the installation to ensure the work is done as indicated and that it is in compliance with standards. Minor changes to an approved permit may be allowed to accommodate actual field conditions encountered during the installation process. However, the discovery of soil conditions or high groundwater levels substantially different than those expected may require the work to stop until the project can be redesigned to meet standards.

There are many parcels in Santa Cruz County which have site constraints that cannot meet the standards for a conventional septic system. However, a nonstandard system may be permitted on many of these properties using either alternative technologies or special operating conditions (such as water conservation) to overcome the constraint(s). Because these systems require added maintenance and oversight to ensure they function properly, County staff inspect them on at least an annual basis and charge an annual fee on the tax bill to pay the cost of those inspections. Prior to approval and installation of a nonstandard system, the property owner must sign an Acknowledgment of Nonstandard System which indicates that they recognize and accept the special operating conditions required for use of such a system. A notice describing these operating conditions is also recorded on the deed to notify any prospective buyer of the special conditions and limitations, if any, of the sewage disposal system serving that property. Standards and procedures for use of nonstandard systems are contained in the Basin Plan, the Sewage Disposal Ordinance and the Repair Standards.

Conclusion

Septic system standards and procedures have evolved significantly in Santa Cruz County during the last ten years. Further changes are likely needed to make the procedures as effective as possible and to take advantage of new technologies that are emerging. It is critical that County Environmental Health, the State Regional Water Quality Control Board, Consultants, Contractors, Realtors, and Property Owners all work together to implement workable septic system design and installation procedures in order to provide property owners with a well functioning septic system that will last many years and not threaten public health or harm the environment.