 |
Oklahoma Administrative Code (Last Updated: March 11, 2021) |
 |
TITLE 252. Department of Environmental Quality |
|
Chapter 656. Water Pollution Control Facility Construction Standards |
|
Subchapter 5. Sanitary Sewer Standards |
SECTION 252:656-5-4. Construction standards
Latest version.
- (a) Sewer. Lay sewers in straight alignment with uniform grade between manholes. Protect all pipe from traffic load damage. Install metal tracer wire on all non-ferrous piping.(b) Trench. The width of the trench shall be ample to allow the pipe to be laid and joined properly and to allow the backfill to be placed and compacted as needed.(1) Trench sides shall be kept as nearly vertical as possible. When wider trenches are dug, appropriate bedding class and pipe strength shall be used.(2) Provide a minimum clearance of 4 inches between all pipe and any large stones, ledge rock, or boulders.(3) Except for ductile iron pipe, provide 30 inches of soil cover as protection from traffic load damage to the pipe. Specify the applicable ASTM standards for ductile iron pipe.(c) Separation. Sanitary sewers located in the street right-of-way shall be located on opposite sides of the streets from potable water linesand shall comply with the following:(1) Horizontal separation. Sanitary sewers shall be at least:(A) 50 feet from petroleum product tanks unless constructed of ductile iron pipe which shall be no closer than 10 feet (joint material shall be resistant to petroleum products);(B) 300 feet from a public water supply well;(C) 50 feet from a private water well;(D) 10 feet from any existing or proposed water main; and(E) 5 feet from electrical lines and petroleum lines.(2) Vertical separation (crossings). Sanitary sewers and sewer service lines shall cross at least 24 inches above or below water mains, and the crossing section centered so that the joints will be as far as possible from the water mains.(3) Special conditions. When it is impossible to obtain proper horizontal and vertical separation as stipulated in (1) and (2) of this subsection, design and construct the sanitary sewer equal to water pipe, and pressure test it to assure water tightness of joints adjacent to the water line prior to backfilling. [See OAC 252:626-19-2(h)(3) (relating to vertical separation of water mains and sewer lines).](4) Prohibition against sewer and water lines in same trench. Sanitary sewer and sewer service lines shall not be laid in the same trench as water mains and/or water service lines.(d) Stream crossings - aerial. Support all joints in aerial crossings. Design crossing supports to prevent frost heave, overturning and settlement. Use concrete encasement (except around PVC pipe) or riprap where the pipe enters stream banks. Use expansion joints between above-ground and below-ground sewers and force mains, and protect them from freezing. Protect pipes that cross streams from the impact of flood waters and debris.(e) Stream crossings - below-grade. The top(s) of all sewers entering or crossing stream beds shall be at least 3 feet below the natural bottom of the stream bed. Construct or encase the crossing with ductile iron pipe using mechanical joints. Sewers shall remain watertight and free from changes in alignment or grade. Trench backfill shall be stone, coarse aggregate, washed gravel or other material that will not cause siltation. Specify construction methods to minimize siltation and bank erosion.(f) Flood plain structures. Protect sewer outfalls, headwalls, manholes, gate boxes and other structures located in flood plains from stream erosion. Locate structures so they do not interfere with the free discharge of flood flows.(g) Manholes. Manholes shall be installed at the end of each line; at all changes in grade, size, or alignment; at all intersections; and at distances not greater than 400 feet apart for sewers 15 inches in diameter or less, and 500 feet for sewers 18 to 30 inches in diameter. Greater spacing may be permitted in larger lines, those carrying a settled effluent or where adequate modern cleaning equipment for such spacing is provided. Lampholes and cleanouts shall not be substituted for manholes nor installed at the end of laterals longer than 250 feet. [See 252:656-27-2(b) (relating to separation distance requirements).](1) Drop manhole. A drop pipe is required for all sewer lines entering a manhole at an elevation of 24 inches or more above the manhole invert. Where the difference in elevation between the incoming sewer and the manhole invert is less than 24 inches, the invert shall be filleted to prevent solids deposition. For drop pipes constructed outside the manhole, the entire outside drop connection shall be encased in concrete. Drop pipes constructed inside the manhole, shall be secured to the interior wall of the manhole and provide access for cleaning.(2) Diameter. The minimum inside diameter of manholes shall be 48 inches with a conical section at top to receive a standard manhole ring and cover.(3) Flow channels. The flow channels through manholes shall conform in shape and slope to that of the sewer lines.(4) Inlet and outlet pipes. Join inlet and outlet pipes to the manhole with a gasket or other flexible watertight connection that allows for differential settlement of the pipe and manhole wall.(5) Watertight covers. Use watertight covers on manholes that may become submerged.(6) Bases. Manhole bases shall be at least 8 inches thick, with a diameter 8 inches more than the largest outside diameter of the manhole. Construct with leakproof joints between the base and manhole.(7) Leakage Testing. Specify the applicable ASTM standard for the test to be used.(h) Inverted siphons. Inverted siphons shall have at least two barrels with a pipe size at least 6 inches in diameter. Provide necessary appurtenances for convenient flushing and maintenance. Construct manholes with adequate clearance for rodding the pipes. Provide sufficient head and select a pipe size for a velocity of at least 3.0 fps for average flows. Arrange the inlet and outlet details so normal flow is diverted to one barrel and either barrel may be taken out of service for cleaning. The vertical alignment shall permit cleaning and maintenance.