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HomeMy WebLinkAbout1978-05-22 Septic System Design & Soil Test ReportA May 22, 1978 Mr. Don Roderick 1925 County Road 24 Long Lake, Minnesota 55356 545 Indian Mound Wayzata, Minnesota 55391 (612)473-4224 -7kiy P19r wN ""-D Re: Percolation Test for Tract A, Registered Land Survey No. 1275 Orono, Minnesota, Job No. 11-78-22 Dear Mr. Roderick: Enclosed is information requested for an on -land sewage treatment system for the above -referenced lot. The drainfield information was based on percolation tests and soil borings performed on May 10, 11, 18, and 19, 1978. The average rate of percolation for the primary site, as tested, was 32.7 minutes/inch. The average rate of percolation for the secondary site, as tested, was 20.0 minutes/inch. The location of the percolation test holes are indicated in Figure 1. Soil borings were augered to a depth of eight feet (81). The soil logs of the soil borings are shown in Table 1. The location of the soil borings, as well as the soils map, are shown in Figure 1. Because of an acceptable percolation rate of 32.7 minutes/inch and because of an acceptable depth to the water table,'*a conventional on-site sewage treatment system is recommended for the priniary site. Due to the high water table, and the steepness of the slope, an "innovative shallow trench system" is recommended for the secondary site. Stated percolation rates are averaged for the location shown, and no guarantee is implied or expressed that these conditions exist for the entire test area. If you have any questions, please do not hesitate to contact me. Sincerely, EUGENE A. HICKOK & ASSOCIATES Ames P. DeBenedet, P. E. JPD/jel Enclosures SOIL BORING #1 Depth 0.0 - 1.0' 1.0 - 2.1' 2.1 - 8.0' TABLE #1 - SOIL LOGS Material Dark brown loam Yellowish brown silty loam Olive brown silty clay Water table encountered at -4.3' SOIL BORING #2 Depth Material 0.0 - 0.9' Dark brown silty loam 0.9 - 2.0' Yellowish brown silty loam 2.0 - 8.0' Olive brown silty clay Water table encountered at -6.0' SOIL BORING #3 Depth Material 0.0 - 0.7' Dark brown loam 0.7 - 2.0' Yellowish brown silty loam 2.0 - 8.0' Olive brown silty clay loam Water table was not encountered within 8.0' of the surface. k Y�fr1 °1h u O `— 9s -rg — i cn r I c� WON 0 c Dai SEPTI c_ E.A. HICKOK & ASSOCIATES JUNL I` I& HYDROLOGISTS -ENGINEERS f`1V11 MINNEAPOLIS -MINNESOTA I �i z 4 Z -0 O 7 0 �oN (LbpF�1,IU< E�EJP�'(la�� r�PP O X `— E.A. HICKOK & ASSOCIATES JANE ME> HYDROLOGISTS -ENGINEERS MINNEAPOLIS -MINNESOTA r_ a0 � 0� c0 o Y O X `— E.A. 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MKOK & ASSOCIATES -f ow -p GOm c_;r& l l ot) HYDROLOGISTS -ENGINEERS MINNEAPOLIS -MINNESOTA SPECIFICATIONS FOR PROPOSED ON-SITE SEWAGE DISPOSAL SYSTEM CONVENTIONAL SYSTEM LOCATION: Don Roderick, System Design for Tract A, Registered Land Survey No. 1275 Orono, Minnesota, Job No. 11-78-22 DATE: May 31, 1978 I. SEWAGE TANK - TWO 1000 -gallon LIQUID CAPACITY tanks, IN SERIES, manufactured and installed in compliance with the following specifications. See Figure 1 for location. 1. MATERIALS A. General All tanks, regardless of material or method of construction shall be: (1) Water tight (2) So designed and constructed as to withstand all lateral earth pressures under saturated soil conditions with the tank empty. (3) So designed and constructed as to withstand a minimum of seven feet of saturated earth cover above the tank top. In addition, the following specifications apply to specific mater- ials as indicated. B. Precast Concrete Tanks (1) Precast concrete tanks shall be constructed of at least a 4,000 psi (pounds per square inch) core test, air entrained concrete mix. (2) Precast concrete tanks shall be cured to at least a seven-day strength before installation. C. Fiberglass and Plastic Tanks Fiberglass and plastic tanks shall be designed and constructed to meet the requirements in Section I - a. above. D. Metal Tanks Metal tanks shall have a wall thickness of at least eight gauge corrosion resistant alloys and shall be coated inside and out with at least one coat of bitumastic seal, Koppers 300-M, or by other equivalent means. Tanks shall be carefully installed so as not to puncture or damage the seal coating. E. Block or Sectional Tanks (1) Rectangular Blocks (a) Rectangular blocks shall be laid on an approved bottom. Block shall be at least eight inches thick, constructed of a 4,000 psi core test concrete mix, and cured to a 28 -day strength before installation. (b) Rectangular blocks shall be laid either with mortar joints or filled cores. (c) There shall be at least two coats of 1/4 inch thick concrete plaster placed on the inside of the block tank. There shall be at least two hours elapsed time between coats. The plaster coat shall start at the bottom course and work up. (2) Circular Block Tanks (a) Circular blocks shall be carefully placed on an approved bottom. Circular blocks shall be at least two inches thick and constructed of a 4,000 psi core test concrete mix, cured to a 28 -day strength before installation. (b) There shall be at least two coats of 1/4 inch thick concrete plaster placed on the inside of the block tank. There shall be at least two hours elapsed time between coats. The plaster coat shall start at the bottom course and work up. (3) Sectional Tanks (a) A sectional tank shall have an entire section cast as an integral unit. (b) A sectional tank shall have two or more sections and shall have at least one joint below the level of the outlet in- vert of the tank. (c) Sectional tanks shall have an integrally cast bottom, or shall be laid on an approved bottom. (d) The joint or joints shall be permanently sealed so as to be watertight. (4) Bottoms (a) Any tank not having an integrally cast bottom shall not be installed when the water table is closer than three inches to the bottom of the excavation. - 2 - (b) If the bottom is poured -in-place concrete, it shall be at least four inches thick and extend to at least four inches outside the tank wall. A concrete mix of at least one part cement, two parts washed sand and three parts washed rock shall be mixed before placement in the excavation. (c) If a starter ring is used, it shall be constructed of a 4,000 psi core test concrete mix, cured to a seven-day strength before installation. It shall extend at least one inch beyond the tank wall, inside and out. A bottom shall be poured of concrete mix defined in Section (b) above. It shall extend at least two inches above the starter ring and shall be at least four inches thick. (d) If a precast bottom is used, it shall be made of a 4,000 psi core test concrete mix, cured to a seven-day strength before installation. It shall extend at least one inch beyond the tank wall, or be cast integrally with the bottom section. (e) A sectional tank not having an integrally precast bottom shall have a four -inch thick bottom poured within the tank walls. (5) Covers (a) Any tank cover not integrally cast with the tank shall be so installed that the joint with the tank sidewall is permanently sealed so as to be watertight. (b) All covers shall be so designed and constructed as to withstand a minimum of seven feet of saturated earth cover above the tank top. F. Inlet and Outlet Device Materials (1) Inlet and outlet devices shall be sanitary tees, or baffles constructed of acid resistant concrete, acid resistant fiberglass or plastic. (2) Sanitary tees shall be glued to the inlet or outlet pipes. Baffles shall be integrally cast with the tank, affixed with a permanent waterproof adhesive or affixed with stanless steel connectors, top and bottom. 2. DESIGN All tanks, regardless of material or method of construction, shall conform to the following design criteria: - 3 - A. The LIQUID DEPTH of any septic tank of compartment thereof shall be not less than 30 inches. A liquid depth greater than six and one-half feet shall not be considered in de- termining tank capacity. B. No tank or compartment thereof shall have an inside horizontal dimension less than 24 inches. C. Inlet and outlet connections of the tank thereof shall be sub- merged by means of vented, sanitary tees or baffled. D. The space in the tank between the liquid surface and the top of the inlet and outlet baffles or sanitary tees shall be not less than 20 percent of the total required liquid capacity, except that in horizontal cylindrical tanks this space shall be not less than 15 percent of the total required liquid capacity. E. The inlet baffle or sanitary tee shall extend at least six inches but not more than 20 percent of the total liquid depth below the liquid surface and at least one inch above the crown of the inlet sewer. F. The outlet baffle or sanitary tee and the baffles or sanitary tees between compartments shall extend below the liquid surface a distance equal to 40 percent of the liquid depth except that the penetration of the indicated baffles or sanitary tees for horizontal cylindrical tanks shall be 35 percent of the total liquid depth. They also shall extend above the liquid surface as required in D. above. In no case shall they extend less than six inches above the liquid surface. G. There shall be at least one inch between the underside of the top of the tank and the highest point of the inlet and outlet devices. H. The inlet invert shall be not less than three inches above the outlet invert. I. The inlet and outlet shall be located opposite each other along the axis of maximum dimension. The horizontal distance between the nearest points of the inlet and outlet devices shall be at least four f=et. J. Sanitary tees shall be at least four inches in baffles shall be no less than six inches or no inches measured from the end of the inlet pipe point on the baffle. Outlet baffles shall be ured from beginning of the outlet pipe to the the )affle. - 4 - diameter. Inlet more than 12 to the nearest six inches meas - nearest point on Feature Minimum Setback Distances Cfeet) Buildings Property Lines The ordinary High Water Mark of: Natural Environment Lakes and Rivers Recreational Development Lakes and Rivers General Development Lakes and Streams Wild River Scenic River Designated Tributaries of Wild, Scenic, and Recreational Rivers 10' 20' 150* 75* 50* 150* 100* 75* *Required for new developments and where practicable, for existing developments. 4. SURFACE FLOODING Sewage tanks shall not be placed in flood plains delineated by local ordinances adopted in compliance with the Statewide Standards for Management of Flood Plain Areas of Minnesota (Minn. Reg. NR85-93), or in areas for which regional flood information is available from the Department of Natural Resources, except that in areas where ten year flood information is available from and/or approved by the Department of Natural Resources. - 5 - II. DISTRIBUTION OF EFFLUENT 1. BY GRAVITY FLOW OVER THE SOIL TREATMENT AREA A. Level Ground (1) The box shall be watertight with a removable cover and shall be constructed of durable materials not subject to excessive corrosion or decay. The minimum inside dimen- sion shall be at least ten inches. (2) The inverts of all outlets shall be at the same elevation as measured from a liquid surface in the bottom of the box. (3) The inlet invert shall be at least one inch above the out- let inverts. (4) The outlet inverts shall be at least four inches above the distribution box floor. (5) Each drainfield trench line shall be connected separately to the distribution box and shall not be subdivided. When sewage tank effluent is delivered to the distribution box by pump, either a baffle wall shall be installed in the distri- bution box or the pump discharge shall be directed against a wall or side of the box on which there is no outlet. The baffle shall be secured to the box and shall extend at least one inch above the crown of the inlet flow line. B. Sloping Ground Where the elevation difference of the ground surface exceeds 28 inches in any direction within soil treatment area a drop box shall be installed at the head end of each lateral line. Connec- tions between drop boxes shall be by watertight pipes. (See Figure 2) (1) The drop box shall be watertight and constructed of durable materials not subject to excessive corrosion or decay. The minimum inside dimension shall be at least ten inches, un- less the box is to be used as a valve box. Then each outlet shall have at least eiqht inches of sidewall space and the side of any outlet shall be at least six inches from any corner. (2) The invert of the inlet pipe shall be at least one inch higher than the invert of the outlet pipe to the next trench. (3) The invert of the outlet pipe to the next trench shall be at least two inches higher than the invert of the outlet pipe of the trench in which the box is located. (4) When sewage tank effluent is delivered to the drop box by a pr�ap, the pump discharge shall be directed against a wall or side of the box on which there is no outlet. (5) The drop box shall have a removable cover either flush or above finished grade or covered by no more than six inches of soil. III. DRAIN FIELD - Final treatment and disposal of all sewage tank effluent shall be by means of soil treatment. 1. SIZING Indicated average percolation rate is 32.7 minutes per inch for the primary site and 20.0 minutes per inch for the alternate site. The proposed flow rate into the system is based on the require- ments for a four-bedroom house. A. Total drainfield absorption area is 1200 square feet. B. Drainfield trench bottom width is 3'. C. TOTAL lineal feet of drain tile is 400. D. This requires 5 laterals of 80 feet in length. (See Figure 1 for typical placement.) E. Minimum spacing of laterals is 7.5 feet from center to center. 2. LOCATION A. On slopes in excess of 12 percent the soil profile shall be carefully evaluated in the loca*ion of the proposed soil treatment area and downslope to identify the presence of layers that mai► cause sidehill seepage. In no case shall a trench be located within 15 feet of such a layer surfacing on the downslope. B. Bed construction shall be limited to areas having natural slopes of less than six percent. C. Any soil treatment area other than seepaqe pits shall be set bacx the following distances from the features given below: Feature Set back distance in feet Water supply well less than 50 feet deep and not encountering at least 10 feet of impervious material 100 - 7 - Feature Set back distance in feet Any other water supply well or buried water suction pipe 75 Buried pipe distributing water under pressure 10 Building 20 Property lines 20 The ordinary High Water Mark of: Natural Environment Lakes and Streams 150* Recreational Development Lakes and Rivers 75* General Development Lakes and Streams 50* Wild River 150* Scenic River 100* Designated Tributaries of Wild, Scenic, and Recreational Rivers 75 *Required for new developments and where practicable, for existing developments. 3. DESIGN AND CONSTRUCTION A. The bottom of trenches and beds shall be at least three feet above the water table or bedrock. B. The bottom of the trench or bed excavation shall be level. The bottom and sides of the trench or bed excavation to the level of the filter material shall be scarified to remove smears left by the construction equipment and footprints. All loose material shall be removed from the excavation The bottom of the excavation shall not be driven on or walked on after scarification. C. When the soil percolation rate at the bottom of the trench or bed is slower than 15 minutes per inch, no vehicle or excava- tion equipment shall be allowed on the trench or bed area. Excavation shall be by back hoe or other means that allow the equipment wheels or tracks to remain on the surface soil. M_ D. There shall be a layer of 12 inches of filter material in the bottom of the trenches and beds placed as shown in Figure 3. E. Distribution pipe used in trenches or beds for gravity flow distribution shall be at least four inches in diameter and constructed of sound and durable material not subject to corrosion or decay or to loss of strength under continuously wet conditions. The ends of each lateral shall be capped. (1) Agricultural drain tile shall be in 12 -inch It Tths and laid with 1/4 -inch open joints on grade boards. All open joints shall be protected on top by strips of asphalt -treated building paper at least ten inches long and three to six inches wide or by other acceptable means. (2) Perforated plastic pipe shall be laid with one row of per- forations on the bottom. Perforations shall be at least 1/2 -inch in diameter and spaced no farther than 12 inches apart. (3) Other devices may be used to distribute sewage tank effluent over the soil treatment area upon approval of the local ad- ministrator of the sanitary ordinance. (4) The distribution pipes shall be laid level or on a uniform slope away from the sewage tank of no more than four inches per 100 feet. F. The filter material shall be covered with untreated building paper or a two-inch layer of hay or straw or similar, ap- proved permeable materials. G. The trenches or beds shall be backfilled with the excavated material and slightly crowned above finished grade to allow for settling. The backfill shall not be compacted to a density greater than that of the original soil. H. The minimum depth of cover over the distribution pipes shall be at least eight inches. I. The maximum depth of cover over the distribution pipes shall be no more than 36 inches and preferably 24 inches. J. A grass cover shall be established over the soil treatment area. K. See Figure 3 for further detail.