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Minnesota Pollution Control Agency (MPCA) Subsurface
Sewage Treatment Systems (SSTS) Installer Certification
Questions And Correct Answers Plus Rationales 2025.
- What is the primary purpose of an SSTS in Minnesota? To treat and dispose of domestic wastewater on-site Properly designed SSTS systems protect public health and the environment by treating and dispersing wastewater safely.
- Which Minnesota Rule governs the design and installation of SSTS systems? Minnesota Rules Chapter 7080- 7083 These chapters provide specific technical standards and administrative requirements for SSTS.
- Which soil horizon is most suitable for a drainfield trench? Unsaturated permeable soil An unsaturated zone allows for aerobic treatment and percolation, which is critical for wastewater treatment.
- What is the minimum vertical separation required between the bottom of the drainfield trench and a restrictive layer? 3 feet Minnesota requires at least 3 feet of vertical separation to ensure adequate soil treatment.
- What is the minimum setback from a septic tank to a drinking water well? 50 feet This setback protects drinking water from contamination by sewage effluent.
- Which component provides primary treatment in an SSTS? Septic tank The septic tank separates solids and allows partial digestion before effluent enters the soil treatment area.
- What is the maximum allowable slope for a soil treatment area? 12% Slopes greater than 12% can lead to surfacing and erosion problems.
- Who is responsible for obtaining the required permits for SSTS installation? The property owner However, installers often assist the property owner in preparing and submitting permit applications.
- What is the main function of a distribution box? To evenly distribute effluent to the laterals Proper distribution prevents overloading any one section of the drainfield. 10.What type of soil texture is generally unsuitable for a conventional drainfield? Clay Clay soils have low permeability, which can cause ponding and system failure.
17.What is the maximum distance that effluent can travel in a gravity flow line before a pump is needed? 150 feet Beyond this distance, effluent may not flow adequately and a pump is required. 18.What is the purpose of a soil pit observation? To determine soil characteristics and limiting layers This ensures the system design is compatible with site conditions. 19.What is the minimum tank capacity for a three-bedroom home? 1,500 gallons Minnesota Rule specifies minimum tank sizing based on number of bedrooms. 20.What is the minimum setback from a drainfield to a property line? 10 feet This ensures adequate space and minimizes disputes or encroachment. 21.Which component must be watertight? Septic tank and pump tank Leaks can lead to system failure and groundwater contamination. 22.When installing a pump, what feature prevents backflow? Check valve A check valve keeps effluent from flowing backward into the tank. 23.Which site condition requires an alternative design? High groundwater table
A mound or other advanced system may be needed where separation distance is inadequate. 24.Which of these is a sign of a failing system? Surfacing effluent Surfacing indicates the soil treatment area is overloaded or clogged. 25.What should be done if bedrock is encountered at 2 feet below trench bottom? Design a mound system A mound provides additional vertical separation above restrictive layers. 26.How should excavation spoils be handled? Disposed of downslope, away from the system Spoils can compact soil or interfere with drainage if left on top of the system. 27.What is the purpose of inspection pipes in a drainfield? To monitor the performance of the system They allow for easy observation of effluent levels. 28.What is the minimum setback from a drainfield to a wetland? 50 feet Wetlands must be protected from contamination. 29.What is the required slope for effluent lines in a gravity system? 1/8 to 1/4 inch per foot This ensures proper flow without excessive velocity.
37.What must an installer do when using effluent filters? Install and maintain per manufacturer’s instructions Filters improve effluent quality and protect the drainfield. 38.Which type of effluent distribution promotes the longest drainfield life? Uniform distribution Even loading prevents overloading any single area. 39.When sizing a pump, the installer must consider: Head pressure, flow rate, and elevation These factors ensure the pump delivers the correct volume at the correct pressure. 40.Which condition requires soil replacement or mound construction? Shallow bedrock If native soil is inadequate, soil must be added to meet treatment requirements. 41.If a system is installed on a slope, what should be done to prevent erosion? Install erosion control measures Silt fences, mulch, or vegetation help stabilize the site. 42.How should inspection ports be installed? Extend to the surface and be accessible This allows for easy monitoring and maintenance. 43.Which license is required for an installer to legally install SSTS systems in Minnesota? MPCA SSTS Installer license Only certified installers can legally install or repair SSTS systems.
44.What is a common reason for system failure? Lack of maintenance Neglecting pumping and inspections leads to clogging and failures. 45.What is the purpose of the baffle in a septic tank? To prevent solids from exiting the tank Baffles direct flow and keep solids in the tank for digestion. 46.What test is performed to determine soil permeability? Percolation test or soil boring analysis These tests help select the appropriate system design. 47.Which component must be vented to prevent odor and gas buildup? Septic tank and effluent lines Proper venting protects system function and occupant safety. 48.How deep should laterals typically be installed? 12 – 36 inches below the ground surface This ensures contact with unsaturated soil for treatment. 49.What is the penalty for installing an SSTS system without a permit? Administrative fines and possible revocation of license Working without a permit violates Minnesota Rules and local ordinances. 50.When must the installer provide homeowner education? At system completion Educating owners on proper use and maintenance helps ensure long-term system performance.
58.What is the required freeboard in a septic tank? 12 inches Freeboard prevents overflow during peak flows. 59.What is the maximum depth of a trench for a gravity system? 36 inches Deeper trenches may reach saturated zones, reducing treatment. 60.How far must the system be from a swimming pool? 20 feet Setbacks protect recreational water from contamination. 61.What is the minimum size of inspection pipes? 4 inches Smaller pipes are too difficult to use for observation. 62.When are manhole risers required? When tank covers are more than 12 inches below grade Risers provide easy access for pumping and inspection. 63.Which system type is required if the percolation rate is less than 0.1 in/hr? Holding tank or advanced treatment unit Extremely slow soils can’t absorb effluent properly. 64.How often must pump alarms be tested? At least annually Testing ensures the alarm works when needed.
65.What is the function of an effluent filter? To trap solids before effluent enters the drainfield This prolongs drainfield life by preventing clogging. 66.What does “linear loading rate” mean? Flow rate per unit length of trench It helps distribute flow evenly in trenches. 67.What is the minimum design flow for a four-bedroom house? 600 gallons per day Design flow must meet or exceed expected wastewater generation. 68.What must the installer do if an abandoned system is encountered? Properly abandon per local code Old systems must be decommissioned to avoid contamination. 69.What is the primary source of nitrates from septic systems? Effluent discharge Untreated or poorly treated effluent can cause nitrate pollution. 70.Which situation may require pressure distribution? Very permeable soils Pressure systems ensure even dosing in fast-draining soils. 71.How often must lift pumps be serviced? As per manufacturer’s recommendations Routine maintenance prevents pump failure.
79.What does “peak flow” refer to? Maximum expected wastewater flow System design must handle peak flows without backup. 80.What does “biomat” mean? Biological layer in the soil treatment area It helps treat effluent but can clog if overloaded. 81.What is the minimum tank baffle extension below the water line? 12 inches Proper baffle placement improves solids retention. 82.Which component can freeze if not properly insulated? Pump discharge line Frozen lines can cause backups and damage. 83.How can freezing be prevented in a mound system? Insulate and maintain adequate cover Cover and insulation protect pipes and distribution media. 84.What is a distribution valve used for? To alternate effluent flow between drainfields Alternating fields allows recovery time and extends system life. 85.What must be documented in an as-built drawing? Location and dimensions of all components Accurate records are essential for future maintenance.
86.What is the purpose of flow equalization? To spread effluent loads evenly over time This reduces hydraulic surges and protects the drainfield. 87.Which soil structure is best for treatment? Granular or blocky These allow good permeability and aeration. 88.What is the minimum tank cover thickness? 2 inches concrete or equivalent Adequate covers prevent collapse and contamination. 89.What must be done before reusing an old septic tank? Inspect for leaks and structural integrity Reusing a faulty tank is not allowed. 90.What does “SSTS abandonment” require? Pumping, crushing, and filling the tank Proper abandonment prevents hazards and contamination. 91.What is the purpose of a sand filter? To provide additional treatment of effluent Sand filters improve effluent quality before soil dispersal. 92.How far must a holding tank be from a well? 50 feet Same as septic tanks, to protect drinking water.
- What does “OWTS” stand for? Onsite Wastewater Treatment System This is another term for SSTS.
- What is the purpose of a septic tank outlet baffle or tee? To prevent floating solids from leaving the tank This helps protect the drainfield from clogging.
- How deep should a pump tank be installed to prevent frost damage? Below frost depth or properly insulated Protects pumps and pipes from freezing.
- What does the term “limiting layer” refer to in soils? Layer that restricts vertical movement of water Examples include bedrock, water table, or dense clay.
- Which factor most affects effluent dispersal? Soil texture and structure They determine how well wastewater moves and is treated in the soil.
- What is the minimum setback from a system to a road right-of-way? 10 feet Prevents conflicts with future road work and utilities.
- How often must licensed installers renew their license? Every year Annual renewal keeps certification valid and current.
- What is the consequence of failing to submit an installation report? Administrative penalties and possible license suspension Installers must document all work as required by MPCA rules.
- What is the function of a surge tank? To store excess flow temporarily Controls peak flows and protects the soil treatment area.
- What is the typical depth for soil borings? At least 3 feet below the trench bottom This helps identify any restrictive layers or groundwater.
- What does “ponding” in a drainfield indicate? System is hydraulically overloaded or soil is clogged May require repair or redesign.
- What should you do if you discover a buried fuel tank during excavation? Stop work and notify the property owner and appropriate authorities Buried tanks can pose environmental hazards.
- What is the minimum distance between trenches in a drainfield? 3 feet side-to-side Prevents overlapping of infiltration zones.
- What is the purpose of effluent dosing? To apply wastewater in controlled amounts Prevents overloading the soil and helps maintain treatment quality.
- How are tank lids secured for safety? With locking devices or heavy covers Prevents unauthorized access or accidents.
- When should the soil pit observation be performed? Before final system design Site evaluation determines proper sizing and placement.
- Which site feature could require a holding tank? Tiny lot with no suitable soil Holding tanks are used when soil treatment isn’t possible.
- What is “permafrost” in the context of SSTS? Ground that stays frozen year-round May require special design considerations in northern areas.
- What is the purpose of a flow splitter? To divide flow evenly among multiple trenches or beds Ensures uniform loading and prevents premature failure.
- When is a pressure bed preferable to trenches? When lot size is limited Pressure beds maximize area use and achieve uniform distribution.
- What should you do if snow is present during installation? Remove snow and install on thawed, dry soil Snowmelt can cause smearing and poor soil conditions.
- What must be included in a management plan? Operation and maintenance requirements for the system This guides the owner in proper upkeep.
- How often must distribution boxes be checked? At least once per year Uneven distribution can lead to drainfield failure.
- How is trench bottom elevation verified? Leveling device and measurement Ensures proper slope and even distribution.
- What is the minimum setback from a drainfield to a stormwater pond? 50 feet Protects surface water from contamination.
- What is the maximum acceptable drop in elevation in a trench bottom? 2 inches per 100 feet Maintains even effluent dispersal.
- How is soil compaction prevented during installation? Use light equipment and minimize traffic over the area Compacted soil loses infiltration capacity.
- What is the main concern with sandy soils? Rapid percolation may limit treatment Pressure distribution or additional treatment may be needed.
