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Home My WebLink About1986-03-06 Septic System Design ReportHakanson Anderson Associates Inc. 222 Monroe Street, Anoka, Minnesota 55303 EuMm J. Hakanan, P.E. 6121427-500 JanM M. Winter, R.L.S. engineers rs and snrrveyon Lawrence 0. K n ilm , P.E. Peter R. Reetikka, P.E. March 6, 1986 VarwEeckhout Building Corp. Attn: Chuck VanEeckhout 15500 Wayzata Boulevard Wayzata, MN 55391 Dear Chuck: At your request a site evaluation to determine soil suitability for an on -site sewage treatment system was performed at Lot 6, Block 1, The Nursery in the City of Orono, Minnesota. Standard methods of percola- tion testing were employed. Elevations are relative to an assumed elevation of 100.0 based at the center of the Devlin Lane cul-de-sac (see enclosed sketch). This report includes: 1. Soil boring logs 2. Percolation test results 3. Testhole location and septic system configuration sketch 4. Septic system design specifications 5. Discussion and recommendations. The soil boring logs show that silt loam to sandy clay loam topsoils overlie sandy clay subsoil horizons. A discontinuous silty medium sand subsoil horizon was encountered at Borehole #1. Soil mottling and gleying begin at 1.5 to 2.0 feet depth at the boreholes. Soil mottles (spots of contrasting color) are accepted indicators of periodic saturation in soils. Gleying (dull gray soil color) form in soils which are saturated and in a chemically reduced condition for long periods of time. Ground water was measured at elevation 103.3 and 101.1 at Boreholes #1 and #5, respectively on March 6, 1986. civil • municipal a planning • soils a laid sureryir a lalkisrape, architecture t Mr. Chuck VanEeckhout Page 2 March 6, 1986 Percolation test results are as follows: Depth Soil Texture at Percolation Rate Hole Elevation (inches) Bottom of Hole (min/in) P-1 109.8 24 Silty sand to medium sand 1 P-2 107.8 18 Silty sand to clayey sand 15 P-3 107.9 18 Sandy clay 17 P-4 109.1 24 Silty sand 6 P-5 108.4 24 Silty sand 16 P-` 106.1 18 Sandy clay 23 Measured percolation rates are consistent to somewhat rapid for the texture of the soil materials in which the percolation tests were run. The City of Orono requires at least three (3.0) feet separation between the bottom of the filter rock of a septic system drainfield and groundwater or indication of periodic soil saturation such as soil mottling. In order to provide the required separation, a mound septic system design is recommended for both the primary and alternate septic system sites on this lot. The proposed mound system is designed to serve a four bedroom house. Design sewage flow is 600 gallons per day. With a design infiltration rate of 1.2 gallons effluent per square foot per day for the medium sand fill material of the mound, the required rock bed area of the mound is 500 square feet. 600 gal/day = 1.2 gal/ft2/day - 500 ft2 A rock bed 10.0 feet wide by 50. a lon ovides the needed area. A minimum of one and one-half f et (1.5') of m dium sand should be constructed below the rock bed. The basal area calculation of the mound is based on a loading rate of 0.45 gallons per square foot per day for silty clay to sandy clay loam soils. The mound should have at least 1,333 square feet of basal area. 600 gal/day _ 0.45 gal/ft2/day - 1,333 ft2 The basal width of the mound (basal width - distance between upslope edge of rock bed and toe of medium sand fill) is 27 feet. (See cross section of mound on enclosed sketch.) Mr. Chuck VanEeckhout Page 3 March 6, 1986 The pressure distribution system of the mound consists of Schedule 40 PVC plastic pipe. The supply pipe should slope back towards the pumping chamber so that it drains after the mound is dosed. The laterals are 1.5 inch inside diameter pipes. The laterals should have 1/4 inch diameter holes drilled at a spacing of 3.0 feet. The laterals should be assembled to the manifold so that the holes point downwards into the rock bed. The distal ends of the laterals should be capped. Also, the last hole in each lateral should be drilled horizontally in the end cap near the crown of the pipe to facilitate air venting. "? A submersible effluent pump capable of delivering at least 3 gallons per minute against a total dynamic head of at leas 15.7 should be selected. Headlosses are calculated as follows: 1. Vertical headloss of 10.0 feet between pump discharge (approx.„ elev. 101.0) and manifold (approx. elev. 111.0) 2. Friction loss of 0.7 feet in 30 feet of supply pipe (2.35 feet per 100 feet 2.0 inch I.D. plastic pipe at 37.5 gpm flow), 3. Five feet (5.0) to account for losses in distribution network. If as -built elevations are different from those above, headloss should be recalculated to ensure proper pump selection. The pump should be rigged with mercury float switches to dose about 150 gallons of effluent to the mound. An additional mercury float switch should be installed on a separate circuit to an alarm device to warn of pump failure. The mercury switches should be rigged to allow 600 gallons reserve capacity in the pumping chamber. All electrical connections should be watertight. The first septic tank should have at least 1,250 gallons capacity. / The second septic tank should have at least 1,000 gallons capacity. -Oor The pumping chamber should have at least 1,000 gallons capacity. It is highly recommended that the installer of this septic system holds an Individual Sewage Treatment Systems Certificate for installa- tion issued by the Minnesota Pollution Control Agency. The sole purpose of soils data contained herein is evaluation of soil suitability for on -site absorption of septic tank effluent at the test site. Although soil texture and horizonation information and groundwater elevation data may be helpful for the setting of basement elevations at this site, we cannot warrant any such interpretations or use of this data for other purposes. 0 Mr. Chuck VanEeckhout Page 4 March 6, 1986 It you have any questions about information contained in this report, please feel free to contact me. Sincerely, HAKANSON ANDERSON ASSOCIATES, INC. Ghry JWthmn, soil Scientist /mlc Enclosures File: 693.04 • IMS OF SOIL BORINC3S Pgocr: VanEeckhout Percolation FILE No. 693.04 BMING MEd: 4" Flight Auger WE: 3/6/86 (feet 0.0 1.0 2.0 4.5 6.5 7.5 Borehole 01 F� wart nu - 109 -A rk brown silt loam Brown sandy clay loam UfAyish brown silty medium and rayish brown silty medium and, few to many yellowish rown mottles, few gray leyed areas, wet to saturate /depth Gray silty clay, many yellowish brown mottles, many gray gleyed areas, wet END OF BORING *Ground water at 103.3 on 3/6/86 0001 NWW1 ASSOCIATES, INC. E3 OEM feet 0.0 1.0 1.6 3.0 7.0 Borehole /2 1:1MATIAM -1W_A Dark brown silty clay loam Brown sandy clay loam Grayish rows silty c ay oam any yellowish brown mottles, any gray gleyed areas Grayish brown sandy clay, few yellowish brown mottles, few gray gleyed areas END OF BORING Ground water not encountered BY: LAGS OF SOIL BORINGS Roza: YanEeckhout Percolation FILE N0, 693.04 DING NM; 4" Flight Auger DATE: 3/6/86 c, (feet) O.Q 1.0 1.5 M 4A 7.1 Borehole /3 G e%&A"Au — -I n-v a Frkb silty clay loam y clay loam own sandy clay loam, many yellowish brown mottles, many gray gleyed areas Brown silty sandy clay, few yellowish brown mottles i Grayish brown silty sandy clay, many yellowish brown mottles, many gray gleyed areas END OF BORING brouno water nuL enwunr,cu NAKAIMI At+DOR9(XV ASSOCIATES, INC, Borehole #4 p� y �. H rv1Tl�l — 1[�8 ( :-et) Dark brown sandy lom to sandy clay loam 1. Gray silty clayey sand, wet 2. Gray silty clay, many yellowish brown mottles, many gray gleyed areas, wet 4. - Gray -'silty clayey sand, many yellowish brown mottles, many gray gleyed areas, wet 1. END OF BORING Ground water not encountered BY: I= OF SOIL BORINGS Fpp,ECT; VanEeckhout Percolation FILE No. 643.04 BMINS "EnM; 4" Flight Auger DATE: 3/6/86 OEM feet)0.0 1.0 1.5 3.0 6.0 Borehole #5 Fi euari nr - I n6.1 . Dark brown sandy clay loam Brown sandy clay loam Grayish brown sandy clay, many yellowish brown mottles, many gray gleyed areas, wet Gray silty sandy clay, many yellowish brown mottles, many gray gleyed areas END OF BORING *Ground water at 101.1 on 3/6/86 mr] tvo.o� w ` 1 1 1 I r � �v 8 � 0 0 N Sam- LOr.. LAX - iL _ l� lie 1 CW d".o \ y / e r Tbqpelm it lz 7p' Sirs PL.^.j Lo r (o DL Tta � N URS�"R Y .SvRVI�y IUF. Fitom R%Z oRA Fir 11ax.e Loc.. Avp LZ,- - S4 C SC/'//4AJ/1=1'i C/K N�T.�r P.� � Ne 007 ALTERNATE $/r�or (PP-5 R B"9 /O •�. Exi ». GQOaNp St�Ar 5'/o Esis�. 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