WW-06946 Reviewed 2008
Maintaining Your Shoreland Septic System
Shoreland Best Management Practices
Number 2 of 18 in the Series
Best Management Practices (BMPs) are actions you can take to reduce your impact on the environment. BMPs have been described for agriculture, forest management, and construction. This fact sheet describes BMPs you can adopt on your shoreland property to help protect and preserve water quality. In many cases, the best management for shorelands may be retaining the natural characteristics of your property.
In shoreland areas it is particularly important to maintain your septic system properly because soil and water conditions near shore may make the system less efficient in treating wastewater. Incomplete treatment can result in health risks for humans and water quality problems.
Potential health risks are the most serious concern related to failing septic systems. Hepatitis, dysentery, and other diseases may be spread by bacteria, viruses, and parasites in wastewater. These disease-causing organisms, called pathogens, may make nearshore water unsafe for recreation. Flies and mosquitoes that are attracted to and breed in wet areas where wastewater reaches the surface may also spread disease.
Many of the synthetic cleaning products or other chemicals used around the house can be toxic to humans, pets, and wildlife. These products may reach the ground surface or end up in the water.
Excessive nitrate levels in drinking water can result in serious health problems for infants. High nitrate levels in ground water can result from inadequately treated wastewater.
Inadequate treatment can also allow excess nutrients to reach your lake or stream, promoting algae or weed growth. Algal blooms and abundant weeds not only make the lake unpleasant for swimming and boating, but they also affect water quality for fish and wildlife habitat. As plants die, settle to the bottom, and decompose, they use up oxygen that fish need to survive.
The purpose of an on-site wastewater treatment system, commonly known as a septic system, is to treat sewage from your household. A septic system has two parts: the sewage tank and the soil treatment system. The most common sewage tank in Minnesota is a septic tank that receives raw sewage from the household. Three layers form in the tank: solids settle to the bottom and a layer of scum or grease floats on the surface of a liquid layer (Figure 1). As raw sewage is added to the tank, an equal amount of liquid flows out into the soil treatment system.
Figure 1: Typical cross section of a septic tank showing the layers of sludge, liquid, and scum. Newer tanks will have access ports for pumping. Older tanks may have a manhole cover that should be removed for pumping. Inspection ports on older tanks are not suitable for pumping.
Wastewater treatment is completed in the soil absorption area. There are three basic types of soil treatment systems. Drainfield trenches are the most common and do the most effective job of treating wastewater. They take full advantage of evaporation and plant life to help treat sewage. Seepage beds do not require as large a lawn area, but they have a smaller capacity and are less efficient than drainfield trenches. Mounds are elevated systems that may use pressure to distribute sewage effluent. Seepage pits, dry wells, and cesspools are no longer approved and may not be installed. On-site systems with seepage pits should be upgraded to include the proper size tank and drainfield to accommodate the house size and number of residents.
In the soil, microscopic organisms break down remaining biological contaminants such as bacteria or viruses. Nutrients are absorbed by soil particles or taken up by plant life. These processes only work in soil that is not saturated with water. If the soil is too wet, biological breakdown may be incomplete and nutrients may move much greater distances, sometimes hundreds of feet from the drainfield or mound and possibly into surface water (Figure 2). Even systems that appear to be working well or are in compliance with the health code may allow nutrients or bacteria to reach the water.
Figure 2: Avoid water contamination from inadequate wastewater treatment! If your system is improperly designed or located too close to the water, contaminants may reach your lake. This figure shows how ground water moving toward the lake can carry contaminants in saturated soil.
THESE CONDITIONS INDICATE YOUR SEPTIC SYSTEM MAY BE FAILING
The only practical long-term solution may be to upgrade your septic system by redesigning and replacing part or all of it. This work must be done by a registered contractor or a business licensed to design and install individual sewage treatment systems. In many counties, a permit is required for all new construction and replacement.
When remodeling your home or cabin, be sure to expand the capability of your septic system to meet the new demands that will be placed on it. Also, be sure to preserve enough undeveloped space on your property for future expansion of the drainfield.
Here are several BMPs you can follow to keep your septic system in good working order to protect your lake or river.
It will cost $75 to $150 each time you have a septic tank pumped, but replacing the entire system and drainfield may cost from $2,000 to $7,000. Threats to human health and water quality increase if your septic system is not properly maintained.
If water quality in the lake deteriorates, property values are likely to decrease. In addition, if your on-site treatment system fails, you'll have the inconvenience of being unable to use household plumbing until the system is replaced.
For property transactions, a septic inspection is required and the financial institution generally requires proof that the septic system conforms to standards. Minnesota's shoreland regulations require that septic systems within shoreland areas are in compliance with state standards before building permits for additions or new construction are issued.
Overall, your investment to properly maintain a septic tank and drainfield is minimal compared with the cost involved in repairing or replacing the system.
Regulations may vary somewhat in different counties. The state of Minnesota has minimum requirements that apply to shoreland areas, but some counties may have more restrictive ordinances. Check with your county Zoning and Planning, Health, or Shoreland offices for the setback requirements and permits needed in your county.
Setback is the distance away from the shore and is usually measured from the ordinary high water level. In some cases, the setback may be measured from a bluff face or where vegetation begins. The setback for septic systems depends on the type of lake or river. Required setbacks range from 50 feet for general development lakes to 150 feet for remote river segments or natural environment lakes.
The Minnesota Rules for on-site wastewater treatment systems are governed by the Department of Health and the Pollution Control Agency in Chapter 7080. When upgrading or building a new system, be sure to use a licensed contractor who has been trained to comply with these standards.
regional offices of MN State agencies:
Septic System Owner's Guide. Bulletin, PC-6583-S, 1997. Available from county offices of the University of Minnesota Extension Service or Extension Store.
Get to Know Your Septic Tank. Bulletin, MI-0639, revised 1997. Available at no charge from county offices of the University of Minnesota Extension Service or Extension Store.
FARM-A-SYST worksheet and fact sheet #6, Reducing the Risk of Groundwater Contamination by Improving Household Wastewater Treatment. Contact your county extension office.
This fact sheet is one of a series designed to assist shoreland property owners in protecting and preserving water quality. The series includes:
This series of fact sheets is a cooperative effort of the following agencies:
University of Minnesota Extension Service, University of Minnesota
College of Natural Resources, University of Minnesota
Water Plan Coordinators of the Arrowhead counties
Minnesota Board of Water and Soil Resources
Minnesota Department of Health
Minnesota Department of Natural Resources, Division of Fish and Wildlife,
Division of Waters, Division of Forestry
Minnesota Pollution Control Agency
Minnesota Sea Grant Extension Program
Mississippi Headwaters Board
St. Louis County Health Department, Environmental Services Division
Soil and Water Conservation Districts of the Arrowhead counties
Natural Resources Conservation Services
Environmental Protection Agency
Western Lake Superior Sanitary District
These publications may be photocopied for local distribution. The addition of commercial names, products, or identifiers is not permitted. please do not add or delete any text material without contacting:
You may add information about contact persons or regulations specific to your county, region, or lake association.
University of Minnesota Extension Store
St Paul, MN 55108-6069 612-625-8173
Produced by the Arrowhead Water Quality Team, a cooperative effort of Carlton, Cook, Itasca, Koochiching, Lake, and St. Louis counties and state and federal agencies. All publicly funded agencies involved are committed to equal opportunity education, service, and employment.
In accordance with the Americans with Disabilities Act, this material is available in alternative formats upon request. Please contact your University of Minnesota Extension office or the Extension Store at (800) 876-8636.