06-09-1980 Planning Packet - Laserfiche WebLink

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Mr. Mike Gaffron Page 2 May 8, 1980 would perform then ?.ltere would be no need to evaluate their perform.ince. Of course, we do ieel that if the construction techniques and size criteria given below are followed, there is a good possibility the system will pro vide adequate treatment for the effluent generated. We would estimate that the percolation rate in the top 12 inches of the soil profile is in the A6 to 60 minute per inch percolation rate range, or faster. However, based on the high clay content in the subsoil, we feel that there is little need to perform percolation testing at this time. We would suggest the following construction of drainfield trenches: Trench excavation width, 2A inches maximum; trench excavation depth, 12 inches maximum as measured on the down slope fdge of the trench; trenches excavated only when the moisture content of the soil is dryer than the plasti*" limit; drop box distribution between trenches with the liquid level estabxished at •’he top of the rock. Six inches of rock placed under the distribution pipe and two inches of rock above the distribution pipe for a total rock depth of 12 inches; rock cov ered with a layer of hay or straw which in turn is covered with a layer of red rosin paper; trench bottoms to be level throughout their length, distri bution pipe to be level throughout the length of the trench; the top of the rock to be level throughout the length of the trench; and a design factor of one gallon per lineal foot of the above specified trench. Based on this design factor, the city of Orono and Mr. Hawklnson ca;. cecide on the size required for the drainfield trench system, l.e., the total trench length. We would suggest that no single trench be greater than 100 feet long. In order to study the performance of the system, it is absolutely necessary to have a water meter Installed in the residence. The meter should measure all water which flows into the sewage system. The meter should not measure that water which is used outside for the lawn, garden, washing cars, etc. Each drop box should have ready access to determine the Jiquid level in the trench. In addition, inspection wells should be placed halfway along the trench length and at the far end of each trench to ascertain that effluent is fully loading each trench. A V-shaped waterway approximately 12 inches deep should be installed upslope of the trench system to divert any surface runoff from the^ system. To determine the saturated soil conditions, an Inspection well should be installed to a A-foot depth between each of the trenches. This can be a 2-inch to A-inch diameter pipe capped flush with the ground surface. When a decision is made by the city of Orono and Mr. Hawkinson on the size required for the drainfield trench system, a decision should also be made on what will be done in the event that the proposed system does not accept or. treat the effluent generated by the Hawkinson residence. The performance of the proposed system may give some indication of appropriate modifications. For example, if the system as installed is only slightly undersized as indi cated by its performance and the water meter readings, then it may be possible to add several more trenches. If the performance of the proposed system is far less than originally anticipated, it may be necessary to consider the construction of a mound or some other type of soil treatment system. However, whatever considerations are made should be fully understood and agreed upon by both parties. We would also note here that future access to the site is necessary to evaluate the performance of the sewage system. We hope that the above comments will be helpful to you in reaching a decision on the pro posed sewage treatment system. Sincerely yours. (cxnc^~ <£', Roger E. Machmeier Extension Agricultural Engineer James L. Anderson Extension Soils Specialist