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1 <br /> Mound Systems _ <br /> A sewage treatrnent mound is a seepage bed elevated by dean sand fiEl to provide an <br /> adequate separation distanc:e beiween the rodc layer in�he mound and a barrier tayer, <br /> such as saturated soil c�ndfions or bedrodc. The mound must be carefu{ly constructed <br /> to provide adequate sewage treatrnent Mound faitures are usuaily traced in <br /> improper design and construction practices. <br /> Sewa�e Tr�atme,rtt Mounds l+�r P�rob/e,m Locations <br /> Suitable soil provides exceilent treatrnerrt of sewage tank effluent, and the natural <br /> topsoil shouid be crtif'ized for treatrnent wherever passibte. However. some locations do <br /> nof have soils or soii profiles suitable f�or treatrnent of sewage using in-ground or at <br /> grade systems. <br /> For i�sf�noe, some soiis do not have the abili�jr to accept effiuent,which is neoessary <br /> fo�the proper operation of the soil treatrnen#system. tn ot�r soils, t1�re is seasonat <br /> saturatian at depths doser than three feet to the ground surfaoe. suc�that adeQuate <br /> verrticat separation of the soif treatrnerrt uni#is not possible und�"natural"oonditions. <br /> Soils with a hardpan layer that restrid�s dowrtwand movement of tiquid, or with fradured <br /> or petmeabie bedrock, present prob�ms for adequafie irea#ment and/or ac�ceptanoe of <br /> sepfic tank efltuent � <br /> Mounds Tr+�at Sewage EffiecGverly <br /> Properly de.signed and construc�ed sewage treatrnent mounds are an effective method <br /> of onsite sewage treatrnent. Research at the Smail-Scale Vi/aste Management Project <br /> indicaties that re,sideMia!mounds utilizing pressure distribution wili have 44 peroertt <br /> fewer nitrates�tafing downward than a standard subsutface trench system. <br /> Sufficient numbers of mounds have been instafted in Minnesota and eisewhere to prove <br /> that the mound treatrnent system is a standard technot�y. There are more than 8,000 <br /> single-�amily mounds successfully treating sewage in Minnesota. <br /> Important factors in the design and <br /> successful operation of a sevvage <br /> treatmerrt mound are: <br /> • location, <br /> •size ar� shape, <br /> • soil surFace preparation, <br /> •construction procedures, <br /> •distribution of effluent, <br /> •dosing quantitty, and <br /> � •quality of dean sand fill. � <br />