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C':ommunity Development <br />Building Inspection Division <br />Marion County <br /> OREGON <br /> PPd~SS~IZED DISTEIB%~ION SYSTEMS <br /> <br />Construction and Inspection Procedures <br />Marion County Building Inspection <br /> <br />Pressurized distribution systems, shall be used where the depth to soil defined <br />as Soils with Rapid or Very Rapid Permeability in OAR 340-71-100(114)(a) and <br />(b) is less =hah thirty-six (36.) inches or there is less than eighteen (18) <br />inches between the disposal field trench bottom and the above mentioned soils. <br />In areas with permanent water tables, pressurized distribution systems shall <br />not discharge more than four hundred fifty (450) gallons of effluent per one- <br />half (1/2) acre per day. <br /> <br />SITE PREPAPQkTIONt <br /> 1. A site evaluation of the property is required prior to issuance of <br /> an installation permit. The site evaluation report will indicate <br /> if a pressurized distribution system is required on your property. <br /> 2. The application for a septic system installation permit must <br /> include a site plan which shows the elevations of the proposed <br /> house, septic tank and disposal field. The attached s stem h drau- <br /> lic calculation~ worksheet must be completed to determine which <br /> pump will be required for your system. <br /> <br />CONSTRUCTION CRITERIA: <br /> <br /> 1. SEPTIC TANK~ Shall be provided with a watertight manhole riser <br /> extending to the ground surface or above. <br /> 2. TR~nNSPORT PIPING: Two (2) inch minimum diameter; class 160 PVC <br /> 1120 as identified in ASTM Specification D2241. It is recommended <br /> that a trace wire be installed with the pipe to facilitate loca- <br /> tion of the pipe and disposal field in the future. <br /> 3. DISTRIBUTION PIPING:.. Same materials and si~e as transport piping. <br /> Ends of pipes provided with threaded plugs or caps. Installed <br /> level throughout length of trench. ' <br /> 4. ORIFICES= Holes installed on top of distribution pipe in "up" <br /> position with a minimum 1/8 inch diameter. Holes shall be evenly <br /> spaced at distance not greater than 24 inches in coarse ~extured <br /> soils or not greater than 48 inches in finer textured soils. There <br /> s~all be a minimum of five (5) feet of head at the remotest <br /> orifice. <br /> 5. DISPOSAL TRENCHES~ Standard trench construction with gravel six <br /> (6) inches under and four (4) inches over the distribution piping. <br /> The sides of the trench and top of the gravel shall be lined or <br /> covered with filter fabric. In soils finer than loamy sand, lining <br /> the sidewall may not be required. <br /> 6. FILTER FABRIC: Non-degradable material, permeable to fluids but <br /> restrictive to soil particles. Installed as lining for trench <br /> sidewalls and covering over gravel. As of 6/24/92 D.E.Q. memo, <br /> only CBRBX 25 and DUPONT TYPAR 3201 are acceptable for use within <br /> on-site sewage systems. <br /> 7. PUMPS: See attached Effluent Lift Pump Guide. Mus~ be protected <br /> from solids with corrosion resistant screening extending above the <br /> maximum effluent level within the pump chamber. Shall have at <br /> least 12 square feet of surface area with 1/8 inch openings. <br /> <br />INSPECTIONS= <br />1. Install the septic tank, effluent sewer, dosing tank, pressure <br /> line and the disposal trenches up to the level of the distribution <br /> piping. Leave the-distribution piping uncovered and call for <br /> inspection. The system must be tested at this point for pump <br /> operation and head level at the distribution piping. <br />2. Complete the installation of gravel and filter material and make <br /> any corrections noted on first inspection. Call for second inspec- <br /> tion. After this final inspection, you may complete the backfill <br /> <br /> <br />