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Comparison of Type I vs Type III sepfic systems Based on Minnesota State rules Type I System Type III System 1.Type I systems have specific design requirements 1.Type III systems deviate from this known criteria so that have been used and tested for many years so the it's performance is not as well known. Measures are longevity and performance are consistent. usually taken to compensate for the departure from this criteria such as replacing soils with sand and or sizing the Type III system the same size as a Type I. 2. A Type I system requires a minimum separation of 2. A Type III system is not required to have a 12" sep- 12" from the seasonal high water table to grade. aration from the seasonal high water table to grade. A minimum of 36"from the seasonal high water table to the treatment media is required for both Type I and Type III. If the separation distance to grade is less than 12 "this means it will take more materials to construct the system than a Type I. 3.The Septic Tank requirements are the same for both 3. Sepfic Tank requirements are the same for both Type I and Type III. Type I and Type III. 4.There are design tables in the code for the sizing of 4. If a Type III system needs to use values for sizing all types of septic systems . less than a Type I system a means of restricting devic- es that do not allow loading in excess of the smaller allowable values is required.Alternate sizing values can also be proposed but need to be approved by the City. 5. A maintenance program is to be devised by the de- 5. A maintenance program is required for a Type III signer for every type of septic system . system. Also a mitigation plan addressing what to do if the system fails or if portions of the system fail,who is responsible for the work and costs involved in cor- recting these issues. 6. Type I systems can be Mounds,Trenches, Pressure 6.Type III systems are usually Mounds but do not Beds, or At Grade systems. have to be Mounds