City of Bridgman, MI Article IX Sanitary Sewer Construction Standards

§ 470-67 Approval and permits.

Construction of sanitary sewers and/or sewer service shall not commence until engineering plans and specifications have been approved by the City Engineer and permits for construction of the sewers have been issued by the City and the Michigan Department of Environment, Great Lakes and Energy (EGLE).

§ 470-68 Excavation and foundation.

A. The trench shall be excavated so that the flow line of the finished sewer shall be at the depth and grade shown on the approved plans. The trench for the pipe shall be excavated at least 12 inches wider than the external diameter of the pipe. The width of the trench shall not exceed the external diameter of the pipe by more than 18 inches at the top of the pipe. If the excavation has been deeper than necessary, the foundation shall be brought to proper grade by the addition of well-compacted bedding material. Where a firm foundation is not encountered at the grade established, due to soft, spongy or other unsuitable soil (unless other special construction methods are called for on the plans or in the special provisions), all such unsuitable soil under the pipe and for the width of the trench shall be removed and replaced with well-compacted bedding material.

B. The pipe shall be laid so that it will be uniformly supported and the entire length of the pipe barrel will have full bearing. No blocking of any kind shall be used to adjust the pipe to grade except when used with embedment concrete.

(1) Note that when PVC or ABS pipe is used, the bedding material shall extend to 12 inches over the top of the pipe and shall be compacted to the satisfaction of the inspector.

(2) Where required by external loading or soil conditions, concrete bedding shall be substituted for granular bedding.

§ 470-69 Pipe laying.

A. Pipe shall be laid straight both horizontally and vertically between manholes.

B. Pipe laying and joining shall be done in accordance with the pipe manufacturer's recommendations.

C. Pipe shall not be dropped from delivery vehicles. All pipe shall be lowered into the trench with a suitable apparatus; in no case shall the pipe be dropped or thrown.

§ 470-70 Connections.

A. Connections to the sewer main shall be done by means of a wye fitting installed in the main.

B. When the sewer mains are deeper than 12 feet, risers shall be installed at connections such that service pipe shall be no more than 12 feet deep. The pipe shall than be extended to within five inches to zero inches of the surface with a vertical riser at the property line.

C. Unused wye fittings shall have socket ends sealed by water tight rubber or plastic stoppers suitably fastened or braced to prevent dislodging by back pressure from the main line.

D. Connections to existing sewer mains shall be made by installing a new wye fitting or by use of a circular saw cut by proper tools (sewer tap machine or similar) and installation of a wye saddle in accordance with manufacturer's recommendations. All such connections shall be done in the presence of the City inspector.

§ 470-71 Sewer depth.

Sanitary sewers shall be constructed sufficiently deep so as to prevent freezing. For the purposes of this specification, a depth of not less than five feet to the sewer invert shall be required unless otherwise approved by the City Engineer. In addition, they shall be sufficiently deep to provide an outfall for all sanitary sewage within the ultimate service area, both existing and future.

§ 470-72 Backfilling.

A. Backfilling shall not be done until installation of the sewer has been inspected and approved by the Director of Public Services or the City Engineer.

B. Backfill to four inches above the top of the pipe, except flexible thermoplastic pipe, shall be done with material conforming to bedding material placed in six-inch lifts compacted to 95% maximum dry density as determined according to ASTM D1557 or AASHTO-T180.

C. Excavations for sewers which are beneath any existing or proposed pavements, driveways and sidewalks and any trenches where the inner edge is within two feet of such areas shall be backfilled with MDOT Class II granular material in twelve-inch lifts compacted to 95% maximum dry density as determined according to ASTM D1557 or AASHTO-T180.

D. Excavations for sewers not beneath or within two feet of existing or proposed paved areas shall be backfilled with material excavated from the trench, unless such material is determined to be unsuitable by the City Engineer. The material shall be free from clods and rocks and shall be placed in twelve-inch lifts compacting each lift to yield a minimum of 85% of maximum dry density as determined according to ASTM D1557 or AASHTO-T180.