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TO: Jeanne A. Mabusth, Building & Zoning Administrator <br /> FROM: Stephen Weckman, On-Site System Manager <br /> DATE: August 13, 1993 <br /> SUBJECT: Septic System at 2100 6th Avenue North <br /> The Woodlands, Inc. located at 2100 6th Avenue North is a group home which houses six <br /> residents plus a staff of five on a daily basis. This site has an existing failing trench system <br /> requiring replacement at this time. <br /> The existing trench system appears to have failed as a result of several errors found in the design <br /> and installation of the system. The seasonally high water table was incorrectly identified in the <br /> original soil testing at 4.5', while recent borings by staff indicate a seasonal water table at 2.5' <br /> and would preclude the use of trenches. The system was designed with trenches no deeper than <br /> 1.5', but were installed at least 3.S' deep and within the seasonal water table. The water use <br /> at the residence is often greater than the design flow of the system although on average the daily <br /> flow is just below the design flow for the system. Also, it has been determined that <br /> approximately 120 gallons of softener discharge enters the system daily which could be harming <br /> the bacterial action of the system. It is impossible to determine the exact cause of the system <br /> failure, but the combination of several factors is likely to have caused the problem. <br /> The site evaluation for this property indicates that a suitable sewage treatment system cannot be <br /> installed completely within the bounds of this property. Soil borings performed on the subject <br /> property indicate that the existing system was installed within 3' of the seasonally high water <br /> table and thus cannot be. expanded, while the previously designated alternate site has been <br /> compacted and cannot be used. The remainder of the lot north of the residence consists of fill <br /> soils and slopes greater than 12% which do not meet City codes. <br /> A septic system design has been completed and approved by staff pending a lot line <br /> rearrangement. A suitable area has been located north and west of the parking lot for the group <br /> home lying jointly on the subject property and the property to the west. This site meets all City <br /> and State codes. <br /> Staff would recommend approval of the lot line rearrangement provided that a 20' setback is <br /> maintained from the drainf'ield site to the property line. As the proposed drainfield site is the <br /> only area available for sewage treatment on this property, extra care must be taken to protect <br /> this site from compaction. <br /> ch <br />