937.13  SEWAGE PUMPING STATIONS.
   (a)    Sewage pumping stations shall be protected from flooding. A suitable superstructure located off the right-of-way of streets and alleys should be provided. The station shall be readily accessible.
   (b)    Grit shall be given special attention.
      (1)    If a grit problem is anticipated, grit removal equipment shall be included in the station design.
      (2)    Pump intake lines shall be designed to prevent grit from settling in piping of pumps not operating.
   (c)    Wet and dry wells including their superstructure shall be completely separated.
   (d)    Provision shall be made to facilitate removing pumps and equipment.
   (e)    Suitable and safe means of access shall be provided to dry wells of pump stations and shall be provided to wet wells containing either bar screens or mechanical equipment requiring inspection or maintenance. Stairways should be installed, with rest landings not to exceed ten foot vertical intervals.
   (f)    Pumps and Pneumatic Ejectors.
      (1)    At least two units shall be provided, with design to permit installation of one future unit with no structural changes.
      (2)    If only two units are provided, they should have the same capacity, and be capable of handling flows in excess of the expected maximum flow. Where three or more units are provided, they should be designed to fit actual flow conditions and must be of such capacity that with any one unit out of service, the remaining units will have capacity to handle maximum sewage flow.
      (3)    Accessible clogging protection shall be provided in all pumping stations. Type and size of clogging protection will depend on flow and type of pumps used. Approval of clogging protection design is at the discretion of the Superintendent.
      (4)    Pumps shall be capable of passing spheres of at least three inches in diameter. Pump suction and discharge openings shall be at least four inches in diameter.
      (5)    Pumps shall be so located as to normally operate under a positive suction head.
      (6)    Each pump shall have an individual intake, and an outside lever operated check valve.
   (g)    Electrical equipment shall comply with The National Board of Fire Underwriters specifications for hazardous conditions (Nema Type 7).
   (h)    A separate sump pump shall be provided in the dry wells to remove leakage or drainage with discharge above the overflow level of the wet well. All floors and walkways shall slope to point of drainage.
   (i)    Forced ventilation shall be provided on all pumpage stations. There shall be no interconnection between the wet and dry well ventilation system. Dampers, fine screen or other obstructions in air ducts shall be used. Any screen used in the ventilation system shall be at least one-half inch mesh, and must be accessible. Ventilation system must be explosion proof. Ventilation to be by fresh air introduction.
      (1)    Wet well. Ventilation may be either continuous or intermittent. Ventilation, if continuous, should provide at least twelve complete air changes per hour, if intermittent, at least thirty complete air changes per hour.
      (2)    Dry wells. If continuous, should provide at least six complete air changes per hour, if intermittent, at least thirty complete air changes per hour.
      (3)    Type of ventilation to be used is at the discretion of the Superintendent.
   (j)    An alarm system shall be provided for all pumping stations designed to serve over twenty-five homes. The alarm shall be activated in case of high water level in the  wet well and shall be telemetered to the treatment plant.
   (k)    Force Mains from Pump Stations.
      (1)    At design average flow, a velocity of at least two feet per second shall be maintained.
      (2)    An automatic air relief valve shall be placed at high points in the force main to prevent air locking.
      (3)    Under no conditions shall a service tap be made into a force main.
      (4)    Force mains shall be either cast or ductile iron pipe.
      (5)    Force mains should enter the gravity sewer system at a point not more than two feet above the flow line of the receiving manhole. On force mains, the exfiltration will be zero percent (0%).
         (Ord. 12-2-74-A. Passed 1-20-75.)