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HomeMy WebLinkAboutCorrespondence Miscellaneous 4/4/2006 Apr. 4, 2006 4:25PM DEQ EUGENE . No. 1254 P. 1 . State of Oregon DEPARTMENT OF ENVIRONMENTAL QUALITY FAX Transmittal Memorandum " No. of Pages: d... Date: If 'l.{ / 0), , To: . ~J ,'"", From; W-~ c...--1 ;;,. 1 EUGENE OFFICE Dept. of Enviromnental Quality 1102 Lincoln St., Suite 210 Eugene, OR 97401 Company or Department: Phone: Phone: (541)___. ____ (541) 686.7551 , FAX: ,FAX: Message: 0 URGENT o ReView D Please Comment o Please Reply Re: . PlaRRer: , , , i I i Li If ^ f [i Date Received:" I V )0 I dD J 0+(( f~ I I i i I I i , ! o . . -, " '" ~ ./ ! / OA-!<...S4D- ~J. ~~ APPENDIX A ~:-=::::::::; SEWER PIPELINES .1) MINIMUM REQUIREMENTS FOR SEWER - PIPELINES (2) GUIDELINES FOR SEWER PIPELINES (a) Caoacitv: (a) Caoacity: Sewers shall be of such diameter as to (A) Collection sewers should be designed for pass without overflow, bypass, or back the ultimate development of the tributary flow onto damageable property of a user areas as determined by master sewerage the design peak flow including sewage and land use plans of the owner. and intiltration. All unavoidable inflow fram roaf. surface. fooring, foundation, (B) The design of sewers should be based upan or other graundwater. or surface water initial and ultimate tlows. Flows should be saurces shall be excluded from capacity broken' down into domestic, industrial, and allowance. in ti ltration! in flow fractions. A peaking factor should be applied to domestic and industrial fractions. (C) Domestic tlows should be between 50 and 100 gallons per capita per day (gpcd). Peaking factors should be between 1. 8 and 4.0. Infiltration allowance should be normally less than 2,CXlO gallons per acre per day; any greater allowance should be justified. Any significant intlow allawance should be justified. (0) The minimum diameter,Of sewers should be 8 inches far maintenance purpases. Short nonextendable 6 inch sections ,Of up " to 250 feet are permissible. (E) Replacement sewers should be designed commensurate with flow conditions. (b) Velocity: (b) Velocitv: Sewers shall be designed to have a' (A) Sewers should be laid on a gradient which velocity to "self clean" or transport will produce a mean velocity, when flow- constituent solids to the treatment facility ing full or half full, of at least (2) two feet or the owner shall periodically service per second, based upon the Manning for- sewers to flush, transport, or remove mula with" n", the coefficient of rough- solids from sewers with minimal ness. valued at 0.013. r velocity . (B) Sewers with minimal flow such as upper OAR52 A-I (September, 1981) . . (c) Waterti!!htness: Completed sewer construction shall result in limited infiltrationlexfiltration through pipe walls, joints, fittings, and connection fittings, etc., andno inflow. The limit shall be consistent with the pipe and manhole materials and with what is obt.ainable at the time by the construction industry on representative jobs for the same type of construction using high quality materials and state-of- . the-art methods of workmarrship. All completed sewer lines in new work shall be tested for watertighmess using either recognized air or water testing require- ments and procedures. . : reaches of laterals or those sewers serving few dwellings should be steepened and/or . reduced in diameter to approach a (2) two feet per second selfcleaning velocity. Actual flows during initial years of use should be carefully'evaluated in this regard. ,I .',...-_..\ -, ." (C) Force mains and inverted siphons should be designed for (3) three feet per second at average flows. (D) The minimum gradient for 8 inch sewers should be no less than 0.4 percent regardless of pipe material. (E) The minimum gradient for 6 inch sewers should be no less than 0.6 percent, . preferably 0.75 percent. (F) The flow channel(s) through manhole bases should be smooth .and conform to the shape and slope of the inlet sewer(s). (G) Intersecting sewers, sewer connections, etc., should be made without causing backup into the smaller sewer. For intersecting unequal sized sewers in manholes, the elevation at 0.8 of full depth of flow in each sewer should match. (c) Waterti!!hmess: (A) Watertighmess begins with good material and finally depends upon sound field practices. Good inspection and tests should be supplemented with an initial television inspection after trench backfilling is complete. Since many defects do not appear initially. an eleventh month final inspection should be performed where that capability is available and determined necessary to obtain acceptable in-place work. If only one television inspection is considered, the eleventh month inspection is recommended. . (B) Exfiltration testing or the low pressure air test for sanitary sewers should be a pres- 0AR52 A-2 (September, 1981) . . " , , . sure at least 6 feet greater than the groundwater conditions which the sewer is subject to at test time. (C) Pipe materials, joints, fittings, and appurtenances should be selected for their watertight capabilities. (D) Acceptance or performance standards should not necessarily be uniform for all pipe materials since average testing results with good workmanship for work will vary depending upon pipe materials. The range of allowable exfiltrationlinfiltration for work acceptance should be between 50 and 200 gallons per day per inch-of-diameter per mile (gpdidm). Nonporous (non-airpermeable) pipe should sustain pressure for twice the computed time for the same one pound per square inch (ps'i) air pressure drop required by the air test. Test sections should be from manhole-to- manhole or about 700 feet maximum, (E) The watertightness of all building sewers' should conform to the State Plumbing Code and' be tested without exception. (F) Manholes should be water tested for exfiltration during construction and/or visually inspected during first wet weather season after construction for intiltration. Leaks should be promptly repaired. ,. (G) Curved sewers should be as watertight as other sewers and be tested. While not recommended, horizontal/vertical curves at times may be allowed but should be limited in use. When used, the minimum radius of curvature should be not less than 200 feet and the maximum computed joint opening no more than 3/8 inch. Complete and accurate records should be kept of the exact location of such curved sewers for future reference. Reasonable field control should be exercised to not compound joint deflections and compromise watertightness. 0AR52 A-3 (September, 1981) . (d) Structural Stren~h: The completed installation including the excavated trench, the pipe, the bedding, and the pipe zone materials shall resist imposed loads from backfill, impact, and live loads (construction and design) without pipe failure through crushing, loss of watertightness; settlement, or significant capacity loss. (e) Abilirv to Pass Solids: . Sewer systems shall be free of depressions, sharp edges, roughness, side sewer projections, obstructions, restrictions, displaced "0" rings, etc., which can cause solids to accumulate or deposit. 0AR52 . ! (d) Structural Stren~h: (A) Bedding material should be placed full trench width from at least 4 inches under to spring line of all pipe for a leveling course and proper pipe support. Hand shaping of the native trench bottom for rigid pipe is not recommended but may be allowed, if appropriate, and uniform pipe support can be obtained and gradel alignment can be maintained. (B) Cantilevering of nonreinforced rigid pipe at manholes should be limited to the least distance practicable to make a flexible connection. A flexible joint should be within 12 inches of manhole for smaller pipe sizes. A ~econd flexible joint should be provided within 4 feet of the manhole. (C) Where cover from top of pipe to finished grade is less than 36 inches, special design and/or construction requirements should be considered including, but not limited to, raising finish grade, increasing class of pipe and/or pipe bedding, use of ductile iron, concrete encasement and restriction of construction equipment from travel over partially backfilled trench. (e) Abilirv to Pass Solids: (A) New sewers should be thoroughly flushed and visually inspected for accumulated . debris prior to use. (B) Building sewer connections should be made with fittings which prevent any projection into the main sewer. The main sewer should not be cracked, crushed, or otherwise damaged in making taps. All taps should be watertight. (C) A tolerance for vertical deviation from true grade line should be plus or minus 0.02 feet. Depressions for solids deposition should be avoided. Similarly, the horizontal tolerance for deviation from line should be plus or minus 3/8 inch. A-4 (September, 1981) . " , (f) Durability: (A) The materials and details of construction shall provide an in- place sewerage system which will resist corrosion of the pipe and manhole materials caused by any source or condition. Any corrosive effect shall be consistent with the . design life of the sewer. (B) Resistance to erosion of surfaces by grit, high velocity flow, etc., shall be addressed if appropriate. (C) Temperature effect upon thermoplastic materials shall be appropriate. (g) Stability: (A) Line and Grade: Horizontal alignment and vertical grade of in- place sewers upon construction completion and construction acceptance shall be relatively stable. Design considerations, construction specifications, inspections, etc., shall preclude pipe settlement, shifting,. or flotation such that capacity, watertightness structural integrity, ability to pass solids, maintainability, etc., are not compromised either at construction or any later time. (B) Diameter: Rigid, flexible and . (D) Drop manhole piping should be easily maintained, self cleaning or able to '~.overtlow" into the manhole. Pressure sewer piping cD'llnections, flow measuring devices, etc., in manholes should be designed to not obstruct flow. (E) Flow channels in manholes should slope at least 0.1 feet from inlet to outlet. (f) Durability: (A) Sewers should be constructed of materials resistant to or protected from biological degradation, acid and alkaline solutions, normal sewer temperature variations, abrasion and industrial wastes (where applicable), or other harmful service conditions which may exist in the sewerage system. Velocities over 15 feet per second in sewers should have special consideratio for erosion control. ta (A) Appropriate foundation stabilization or soils should be employed in unstable soils. Back fill should be in small lifts and compacted uniformly to specified density along and around the pipe. (B) The Soil Class and density for bedding and pipe zone materials should be carefully selected and then compacted in the field to the required in-place density. PVC and ABS composite sewer pipe should be deflection tested upon construction completion prior to acceptance with an approved nine blade go-no-go gauge. Initial deflection at construction completion should be no more than the following: 0AR52 A-5 (September, 1981) . semitlexible pipes tend to lose minimum inside diameter if not designed andJodnstalled properly. Design considerations, construction specifications, field inspections, etc., shall preclude diameter loss such that capacity, watertightness, structural integrity, ability to pass solids, maintainability, etc., are not compromised either at construction or any later time. (h) Ooeration. Maintenance. and SafelY: Sewer systems require periodic. and unscheduled maintenance for sustained . operation. Designs shall conform to requirements of the sewage works owner for manhole construction, spacing, size, details and easements. All parts of the sewerage system shall be readily accessible. The minimum inside bottom diameter of manholes shall be 42 inches. . ! (i) pye (ASTM 0-3034) sewer pipe should detlect no more than 4 to 5 percent bas~ upon inside base diameters of 7.76,9.71, 11.56 and 14.14 inches for 8, 10, 12, and 15 inch nominal pipe respectively. \ ./ (ii) ABS (ASTM 0-2680) composite sewer pipe should deflect no more thaa 2 to 3 percent based upon inside average diameters of 7.75, 9.75, 11. 75 and 14.75 inches for. 8, 10, 12, and 15 inch nominal pipe re- spectively. (C) Sewers on slopes over 25 percent should be evaluated for slippage or pipe bedding depending upon soil type, groundwater presence, construction conditions, etc. Appropriate anchors should be provided if necessary . (h) Ooeration. Maintenance. and SafelY: (A) Access to the sewer by the sewer owner is essential to perform maintenance tasks. Easements should be granted along the sewer I ine to the system owner for any sewer for emergency repai rs. Manholes and cleanouts are necessary for routine access. Strucrures should not be located over sewers. (B) Owners should review own procedures, equipment, construction standards, etc., for sewer maintenance. Requirements of the owner should be obtained by designers upon start of sewer design since the owner must assume all future maintenance. Stricter standards of the owner should prevail if in conflict with these guidelines. (C) General Manhole/Cleanout Standards for Sewers : (I) The minimum inside bottom diameter should be no less than 48 inches. The least inside dimension may be reduced 38 inches where an integral 0AR52 (September, 1981) , '. A-6 " . . '.; insige drop is acceptable to the owner. No more than one inside drop should be installed in a manhole: (Ii) Minimum cover opening diameter should be 22 inches. (iii) Manholes should be located at: (l) Every change in grade or alignment of sewer. (II) Every point of change in size or elevation of sewer. (III) Each intersection or junction ' of sewers. (IV) Upper end of a lateral sewer. (V) At intervals of 500 feet or less except for 24 inch and larger sewers . (iv) Cleanouts should not be substituted for manholes except at the upper end of lateral sewers 250 feet or less in length. (v) Channel width and depth should be equal pipe diameter. Manhole base ledges should be sloped to drain at least I in 12. (vi) Access to manholes may be by port- able ladder. Manhole rungs and in-place ladders which are subject to considerable' corrosion and sliming are not recommended. (vii) Where free fall of sewage into a manhole exceeds 24 inches from inlet pipe invert to manhole invert, an approved drop manhole should be used. 0AR52 A-7 (Seprember, 1981) . . (D) Inverted Siohons: I Inverted siphons should include at least two pipe lines of such size and hydraulic gra- dient as to maintain a velocity of at least 3 feet per second in one pipe under c'ondi- tions of average dry weather flow. Control manholes must be provided at both ends of the inverted siphon line. The inlet and outlet details shall be so arranged that the . normal flow is diverted to either barrel so that the other barrel may be removed from service for maintenance. / -\ . .-' (i) Seoaration of Water and Sewer Lines: (I) Seoaration of Water and Sewer Lines: Protection of the water supply, be it distribution system, production facilities or source is not only prudent but mandatory and absolutely necessary. (A) Parallel Water and Sewer Lines: (i) Sewer lines should conform to Figure A-I. Sanitary sewers and appurtenances thereto shall not physically connect to a public or private potable water supply system so as to permit the passage of any sewage or polluted water into the potable supply. (ii) Common trench construction for water and sewer should be avoided where practical. Where used, the minimum pipe separations of Figure A-I should be maintalned. Sewer construction shall not disturb, degrade, or decrease the watertightness of any existing water supply line. (B) Vertical Seoaration at Crossin!!s of Water and Sewer Lines: No special precautions should be necessary where top of sewer line is at least 1.5 feet below bOllom of waterline and adequate structural protection for each line is provided. , (C) ExceDtions: Use of Pressure Pice Materials for Sewer Line: (I) Where the above horizontal or verti- cal separations cannot be maintained, the following pressure pipe materials should be used in ,addition to what- ever waterline improvements or reconstruction that may be advisable or required for protection of water. The use of these pressure pipe materials from manhole-to-manhole is encouraged to avoid discontinuity 0AR52 A-8 (September, 1981) . 'i . of materials. (I) . Ductile iron pipe, class 50, ANSI Standard A21.51 (AWWA C-151) with either Push-on or mechanical rubber gasket joints in accordance with ANSI Standard A2Ul (AWWA-Cll I). (II) PVC pressure pipe, ASTM 0-2241, SDR 32.5, (125 psi) with rubber-gasket joint in accordance with UNI-Bell Plastic Pipe Association recommended Standard Specification UNI-B-l for a pressure-joint assembly. (III) Asbestos-Cement pressure pipe, class 100. ASTMC-296 (A WW A C-400) wirh rubber- ring gaskets in accordance wirh ASTM 0-1869. (IV) High densiry polyethylene pipe (Driscopipe 1000) PE 3406, minimum SDR 32.5, wirh butt fused joints. (\I) Orher materials approved by the State Health Division. (ii) At crossings requiring pressure pipe materials, the following should apply with one standard length of special pressure pipe centered over the waterline in all cases: S'2Jld2rd ~Iinimum Layiq . Pipe Pipe' Leo~Lb Eacb Side Material of Waterlin~:". L=lLb Cr~5iDg:i;,':..;:: . Ductile leon I 18 Feet I 18 Feet I PVC 10 Feet I 20 Feet A.&:.to....ccment lJ Feet 19 Feet High.Deruiry I 38 Feel 19 Feet Polyethylene 0AR52 A-9 (September, 1981) . . -. , . ( . (D) Soil Restoration at Crossin!!s: Soil removed in sewer line trench construction at waterline crossings where sewer crosses over water should be replaced in all areas to as near natural densities as possible through mechanical compaction to restore any natural resis- tance to groundwater movement which did exist prior to construction. Soil should include no rocle fragments over 1-112 inch in the pipe zone. /-...... ! / (E) Well Protection: No sewer pipe should be laid less than 50 feet from any well without specific Health Division approval. Pressure pipe materials should be used to protect wells where minimum setbacks are not obtainable or where additional protection is required as determined by the State Health Division. (F) PiDe Testin!!: Whenever a pressure pipe material is used for any of the above purposes of separa- tion, an appropriate pressure test should be conducted on the pressure pipe to confirm watertightness. Test pressures should be no less than 15 psig where use will be for a gravity sewer and higher where use will be for a pressure sewer (force main). (G) Other Exceptions should be resolved jointly with the water purveyor and the State Health Division. 0AR52 (Seprember, 1981) ./ A-I0