§ 6. Sewer construction requirements

6.1. General Requirements. Sanitary sewer improvements shall conform to the requirements of the New Shoreham Board of Sewer Commissioners, Department of Environmental Management, and any other agencies having jurisdiction.

6.2. Sanitary Sewers.

• Depth. Sewers shall be designed deep enough to drain basement fixtures and to prevent freezing. The minimum depth of cover for street installation shall be 6-feet and for cross country installation it shall be 4-feet.

• Slope. The following minimum slopes may be used only if necessary because of grade restrictions.

Sewer Size Inches	Minimum Slope Feet/Foot
8	0.0040
10	0.0028
12	0.0022
14	0.0017
15	0.0015
16	0.0014
18	0.0012
21	0.0010
24	0.0008
27	0.0007
30	0.0006
36	0.0005

 

• Velocity. The minimum velocity for design purposes is two (2) feet per second and the maximum velocity is ten (10) feet per second.

• Alignment. Sewers shall be laid with a straight alignment between manholes.

• Increasing Pipe Size. When a smaller sewer joints one of a larger one, the invert of the larger sewer should be lowered sufficiently to maintain the same hydraulic gradient.

• Materials. Sewers shall be constructed of materials described in Section II. Sewers crossing streams or any body of water shall be ductile iron encased in concrete.

• Manhole Locations. Manholes shall be installed at the end of each sewer line, at changes in grade, size, or alignment and at all intersections. The maximum spacing of manholes shall not exceed 300 feet.

• Drop Manhole Type. A drop pipe should be provided for a sewer entering a manhole at an elevation of 24-inches or more above the manhole invert. The size of the drop pipe will be the same size as the sewer inlet pipe. Where the difference in elevation between the incoming sewer and the manhole invert is less than 24-inches, the invert shall be so constructed so that there is a smooth transition of flow in the manhole.

• Manhole Diameter. The minimum internal diameter of manhole shall be 48-inches.

• Flow Channel. A drop of at least 0.1 feet shall be provided between incoming and outgoing sewers on all manholes.

• Elevation. In all buildings in which any building drain is too low to permit gravity flow to the public sewer, sanitary sewage carried by such building drain shall be lifted by a grinder pump system as specified in Section A and discharged to the building sewer.

• Clean Outs. Clean-outs shall be installed at the property line, at every fitting over 22½ degrees and at 75-foot intervals.

• Grease, Oil and Solids Interceptors. A user who is required to install a grease removal system may install either an outdoor passive in-ground grease interceptor or an automatic electrical/mechanical grease removal unit.

In-ground grease removal systems shall have a minimum capacity of 500 gallons and shall have a capacity to provide at least a 24-hour detention period for the process flow. The process flow shall be based on a minimum of 15 gallons per seat or chair per day or based upon actual water usage for existing facilities.

The automatic electric/mechanical grease removal unit shall be the "Big Dripper" Automatic Grease Recovery System as manufactured by Thermaco, Inc., Asheboro, North Carolina, or equal. The unit shall be sized in accordance with the manufacturer's written recommendation. Influent to the unit with temperatures exceeding 150 degrees will not be permitted.

A separate suitable sampling location as approved by the Superintendent shall be provided for sampling of the discharge from the ground grease removable systems. The automatic electrical mechanical grease removal systems shall have a sampling valve installed on the discharge piping with a minimum clearance of eight (8) inches to allow samples to be taken by representatives of the Board of Sewer Commissioners.

Dishwasher wastewater shall not be discharged into the grease removal systems. The dishwasher wastewater shall bypass the grease removal system and discharge directly into the municipal sewer collection system except that the dishwasher wastewater from the pre-rinse station shall discharge to the grease removal system.

• Identification.

a) Underground-Type Line Markers for Non-Metallic Pipings. Manufacturer's standard permanent detection tape, bright colored, continuous-printed polyethylene tape with a metallic core for easy detection of non-metallic underground installations, intended for direct burial service; not less than 6 inches wide × 4 mils thick. Provide green detection tape with black printing reading "CAUTION SEWER LINE BURIED BELOW" as manufactured by Seton or equal.

b) Underground-Type Line Markers for Metallic Pipelines. Manufacturer's standard permanent, bright colored, continuous-printed polyethylene tape, intended for direct- burial service; not less than six-inches wide by 4 mils thick. Provide green tape with black printing reading "CAUTION SEWER LINE BURIED BELOW" as manufactured by Seton or equal.

c) Installation marker two (2) feet above top of pipe.

• Backflow Preventer. All connections are to be equipped with a backflow preventer. Backflow preventers must conform to the New Shoreham Building Inspector's requirements and the Building Officials Code Administrators Basic National Plumbing Code, Article 10, Section P-1003.0.