Section 327IAC3-6-16. Manholes

   (a) Manholes shall be constructed of:

(1) precast concrete that has lift holes; or

(2) poured-in-place concrete;

and shall have grade adjustment rings sealed with nonshrinking mortar in conformance with ASTM C478-96, Standard Specification for Precast Reinforced Concrete Manhole Sections.

  (b) Inlet or outlet pipes shall be joined to the manhole with a gasketed, flexible, and watertight connection.

  (c) Manholes shall have a minimum diameter of forty-eight (48) inches and a minimum access diameter of twenty-two (22) inches.

  (d) Watertight manhole covers shall be used in any area where the manhole tops are:

(1) subject to flooding by street run-off or high water;

(2) in a floodway; or

(3) in a floodplain.

  (e) Manholes shall be located as follows:

(1) At all end points of sanitary sewers.

(2) Wherever changes occur in grade, size, or alignment of the sanitary sewer.

(3) At all intersections of sanitary sewers.

(4) With separation distances between any two (2) manholes not to be greater than the following:

(A) Four hundred (400) feet for sanitary sewers less than fifteen (15) inches in diameter.

(B) Five hundred (500) feet for sanitary sewers equal to or greater than fifteen (15) inches and less than thirty (30) inches in diameter.

(C) Six hundred (600) feet for sanitary sewers equal to or greater than thirty (30) inches in diameter.

  (f) All upstream sanitary sewers less than twenty-four (24) inches from the manhole invert shall be filleted to prevent solids deposition. Drop pipes shall be provided for incoming sanitary sewers entering a manhole at an elevation of twenty-four (24) inches or more above the manhole invert and shall be in accordance with the following:

(1) Drop pipe connections on the inside of manholes shall be secured to the interior wall of the manhole and provide access for cleaning.

(2) Drop pipe connections on the outside of manholes shall be encased in concrete.

  (g) A flow channel that conforms to the shape of the connecting sanitary sewer shall be made through the bottom surface of the manhole. The channel walls shall be formed or shaped to the full height of the crown of the outlet sewer.

  (h) A bench shall:

(1) be provided on each side of any flow channel if the pipe diameter is less than the manhole diameter;

(2) have a surface slope of no less than four percent (4%); and

(3) receive no discharge onto the surface of the bench from a:

(A) lateral;

(B) service connection; or

(C) drop manhole pipe.

  (i) The inlet to a manhole from a force main shall enter the manhole at an elevation less than twenty-four (24) inches above the flow line of the receiving manhole.

  (j) Manholes shall be air tested in accordance with ASTM C1244-93, Standard Test Method for Concrete Sewer Manholes by the Negative Air Pressure (Vacuum) Test. (Water Pollution Control Division; 327 IAC 3-6-16; filed May 17, 1999, 12:11 p.m.: 22 IR 3093; errata filed Dec 1, 2000, 5:25 p.m.: 24 IR 1033; readopted filed Apr 11, 2005, 2:45 p.m.: 28 IR 2470; readopted filed Jun 15, 2011, 11:15 a.m.: 20110713-IR-327110193BFA)