Section 7 4. Special Considerations
SECTION 7 SANITARY SEWER GRAVITY COLLECTION SYSTEM
4. SPECIAL CONSIDERATIONS
A. . Design criteria:
1. Minimum slopes: Gravity sewer mains shall be designed and constructed to achieve scouring velocities, when flowing full, of not less than 2.0 feet per second, based on Manning’s formula using an “n” value of 0.013.
2. Minimum pipe sizes: Gravity sewer mains shall be minimum 8 inches in diameter. Laterals shall be minimum 6 inches in diameter for single family residential properties; and minimum 8 inches in diameter for multi-family and non-residential properties and are to be connected to the main through a manhole.
3. Manholes shall be installed at the end of each line; at all changes in grade, size or alignment; at all intersections of mains; and with line distances of not greater than 400 feet between manholes
4. Where gravity sewers mains cross above waterlines, the sewer pipe for a distance of 6 feet (pipe to pipe separation) on each side of the crossing shall be DIP or PVC C900/C905, with no joint closer horizontally than 3 feet to the crossing (pipe to pipe separation).
5. The following pipe materials shall be used based on vertical depth of cover and locations, unless shown otherwise required by calculations due to special loading or other conditions:
a) Unpaved swale area:
COVER < 30″-36″: Use PVC C-900 or Ductile Iron Pipe.
COVER > 3 feet: SDR 35 or C-900
b) Paved areas:
COVER < 30″-36″: Use PVC C-900 or Ductile Iron Pipe with concrete slab over it, as per Standard Detail.
COVER > 3 feet: Use PVC C-900 or Ductile Iron Pipe.
B. The Contractor shall be in compliance with all applicable provisions of the Occupational Safety and Health Act of 1970, in general, and any subsequent amendments and revisions thereto and specifically to the provisions concerning confined space entry and the Trench Safety Act. The costs of compliance shall be included as part of the unit cost of pipe installation.
C. The Contractor shall be responsible for providing an approved maintenance of traffic (M.O.T.) plan and shall conduct his operations in such a manner, utilizing warning devices such as traffic cones, barricades and warning lights, and personnel such as flagmen and uniformed police officers, the contractor shall ensure that the public is given adequate warning of hazards of the work site as may be deemed necessary by the City Engineer. In the instance of men working within the manholes, the Contractor shall provide safety provisions to cover any possible of structural failure and/or flooding. Such provisions might include but not be limited to, ladders in position to permit rapid egress; safety harnesses; stand by pumping equipment; extra air supplies; and such other measures as the situation and good construction practices might indicate.
D. Riser rings will not be allowed to adjust manholes to final grade, unless specifically approved by the City Engineer.
E. Sewer Bypass Pumping:
1. Sanitary sewer flows shall be controlled through the section of pipeline and pump stations where work is being performed. Under no circumstances, can portions of the system be removed from service for periods of time in excess of that approved by the City’s Public Works Department.
2. The Contractor shall be responsible to assess conditions and capacities of the existing sewer lines and pump stations, in coordination with City of Miami Beach Public Works Department, and accommodate the flows in the project work-plan in order to implement an acceptable bypass pumping plan at no additional cost to the City.
3. Bypass pumping will be required for all sewers and pump station reconstruction that would result in shutdown of existing facilities. The Contractor shall supply the necessary pumps, conduits, and other equipment to not only divert flow around the pump station, manhole or section of pipe in which work is to be performed, but also to transmit the flow in downstream sewer lines and/or pump stations without surcharge.
4. The bypass systems shall be of sufficient capacity to handle existing flows plus additional flows that may occur during periods of high tide or rainfall. In addition to the primary bypass pumping system emergency backup pumping capability, such as a Vacuum Truck with minimum capacity of 1000 gallons, must be available within one (1) hour in case of emergency.
5. The Contractor shall be responsible for furnishing the necessary labor, power, and supervision to set up and operate the pumping and bypass systems.
6. When pumping is in operation, all pump engines shall be equipped in a manner to keep the pump noise to a minimum in order to comply with the City noise ordinances.
7. Contractor shall have personnel present at all times during sanitary sewers by passing operation. By-passing in the roads or within pedestrian traffic areas shall not result or pose a hazard to pedestrians or traffic.
8. Contractor shall provide an approved maintenance of traffic (M.O.T.) plan and obtain all required right-of-way and regulatory permits prior to commencing any work.
F. As Builts:
Prior to final acceptance, 2 copies of as-built drawings certified by a Florida Registered Land Surveyor and Mapper (PSM) shall be provided to the City for approval and acceptance of the sewer mains, manholes, laterals and cleanouts, together with a copy of the digital media producing such As-Builts. The As-Built drawings must show Station numbers and horizontal offsets from the Base Line and Right-of-Way lines on a plan scaled at not less than 1″=50 ft. for all manholes, wyes, laterals cleanouts etc. in horizontal alignment, and a profile with a vertical scale of not less than 1″ = 2 ft. with invert elevations at all manholes, wyes and at approximately every 50 ft. at a minimum. As-Built Plans and Profiles must also show all abandoned and plugged sewer pipes and laterals within the project limits.