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HomeMy WebLinkAbout1978-08-08 Septic Repair Design ReportDear Mr. and Mrs. Molin: As requested soil borings and percolation tests have been completed at the above location. This investigation weis undertaken in order to deter­ mine the current conditions of the existing on-site sewage disposal system and to make recommendations to upgrade this system. A rather intensive soil boring investigation was undertaken in order to establish the groundwater levels and also to locate suitable sites for percolation tests because of the limited area available for investigation. A total of 8 shallow soil borings were completed in conjunction with three deep borings. The boring indicated a relatively homogenous loam to clay loam soil. See Table 1 for a conqplete description of the deep soil boring logs. The static groundwater level of soil boring 1 was 5.1 feet below land sur­ face and 4.5 feet at soil boring 2. The static water level was not recorded in soil boring 3. All groundwater level measurements were made 24 hours after borings were completed. Conventional on-site sewage disposal systems could not be utilized 'in the vicinity of soil borings 1 and 2 because of the high groundwater level, however, modified mound systems could be utilized. See Figure 1. The groundwater level does not pose a problem in the vicinity of soil boring 3. A total of six percolation test holes were installed. The percolation rates ranged from a high of 11 minutes per inch to a low of 240 minutes per inch. The results of the percolation tests are as follows: Mr. and Mrs. Dean K. Molin Page TWo August 8, 1978 f Percolation Test Hole Percolation Rate Minutes/Inch 11 240 18 11 20 14 Because of the groundwater conditions and percolation in the vicinity of the existing drainfield it is suggested that the present system be abandoned. See Figure 1. It is also recommended that a conventional system be installed in the vicinity of percolation test holes 3, 4, 5 and 6. The average rate of percolation for these test holes is 18 minutes per inch. See Figure 2 for location. The wastewater flow for a three bedroom house is 450 gallons per day. A wastewater flow of this volxune requires a septic tank with a 1,000 gallon liquid limit. However, it is suggested that the existing tank be pumped and that an additional 1,000 gallon tank b«p installed and connected in series with the existing tank. . The dual septic tank system is recommended because if the proposed drainfield site is utilized as shown on Figure 2 it will be necessary to punq> the effluent to the dr2d.nfield. The drainfield requirement for a wastewater load of 450 gallons per day and a percolation rate of 18 minutes per inch is 751 square feet. The square footage requirement could be obtained by installing four laterals with a width of 3 feet and a length of 64 feet. See Figure 2. It can be theorized that the existing system failed either because of ten^orary high groundwater levels or variable percolation rates as indicated by the 240 minutes per inch recorded at P2. If you have any cpiestions please do not hesitate to contact me< SincerelyI SOLOM, INC. Marcxis C. Hannaman Soil Scientist MCH/cmk Enclosures TABLE I SOIL BORING LOG NOLIN Soil Boring 1 - (Soil - apparent fill) Depth, Inches Material 0-48 48 - 53 53 - 60 Dark brown clay loam mottled - possible fill or disturbed Brown to gray brown loam Gray loam The static water level after 24 hours was 5.1 feet below land surface. Mottling indicates that perched water table conditions may exist during wet seasons. Soil Boring 2 0-9 9 - 36 36 - 42 42 - 48 48 - 54 54 - 72 Dark brown loam (fill) Dark brown loam Brown loam Brown to yellow brown loam Grayish brown loam, mottling, with fine angular gravel Brown sandy loam, saturated The static water level after 24 hours was 4.5 feet below land surface. Soil Boring 3 0-30 30 - 36 36 - 84 Dark brown loam Brown to gray brown loam Yellowish brown sandy loam - heavily mottled with calcareous concretions and fine amgular sand The stati tter level was not recorded in the upper 7 feet of the soil profile after 24 hours. Dog o-SB SB Pen a' SB P 3� —SB3 Tree Line Dean K. Molin - 248 Cygnet Place, Long Lake, Minnesota Locatica Map Patio House Existing Septic Tank SCALE, feet 0 20 40 Figure 1 Solum, Inc. SCALE, feet Dean K. Nolin, 248 cygnet Place. Long Lake, Minnesota Figure 2 Location Map - On-Site Sewage System Design Solum, Inc.