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§ 11.05.030.010 GENERAL.
   (A)   Design requirements. Sanitary sewer systems shall be designed, constructed and tested in accordance with the current editions of Circular DEQ-2 - Montana Department of Environmental Quality - Design Standards for Wastewater Facilities and the Montana Public Works Standard Specifications.
   (B)   Design report.
      (1)   All sanitary sewer main extensions shall require the design engineer to submit a written report to the PWD which addresses the design requirements listed herein.
      (2)   The design report shall demonstrate that all sanitary sewer main extensions have adequate capacity to convey wastewater from the anticipated service area and meet the minimum flow velocities and/or flow depth requirements in Chapter 30 of MDEQ Circular-2.
      (3)   The design capacity should be based on 112 gpd per capita for single family residence and an average of 2.1 people per residence.
(Prior Code, § 11.05.030.010) (Ord. 2019-9, passed 9-3-2019; Ord. 2021-15, passed 12-20-2021)
§ 11.05.030.020 SANITARY SEWER MAINS.
   (A)   Design considerations.
      (1)   Slope.
         (a)   Gravity sewer mains shall be installed with slope adequate to maintain flow velocities of at least two feet per second (fps) when depth of flow is at one-third of the sewers main inside diameter, based on Manning’s equation with an “n” value of 0.013.
         (b)   Recommended minimum pipe slopes listed in Section 33.41 of Circular DEQ-2 will be considered adequate.
      (2)   Capacity. Public sanitary sewers and appurtenances shall be designed to accommodate peak hourly flows, including an allowance for infiltration, while flowing no more than half full when no additional connections are possible and a quarter full when future growth is anticipated.
         (a)   The development must upsize the existing mains if the capacity of the sewer main is calculated to be three quarters full.
         (b)   The allowance for infiltration shall be 150 gallons per acre of coverage area per day or otherwise approved by Public Works Department.
      (3)   Diameter. Gravity sewer mains shall have a minimum diameter of eight inches. Increasing the diameter in order to meet the minimum pipe slope requirements will not be allowed.
      (4)   Manholes. Shall be a minimum for 48 inches less the 13 feet of bury for all manholes with bury depth greater than 13 feet a minimum of 60 inches manhole is required.
      (5)   Flow direction. On the infrastructure plans all sewer pipes shall be labeled as to the flow direction.
      (6)   Accessibility.
         (a)   Sewer mains shall be installed in the public right-of way wherever possible.
         (b)   Where mains cannot be installed in the right-of-way, a 20-foot wide exclusive easement with a 14-foot all-weather surface road must be constructed in the easement.
   (B)   Materials.
      (1)   Gravity piping. Gravity sewer main piping shall consist of any of the following materials:
         (a)   PVC meeting ASTM D3034, SDR 35 and 26 (8" to 15");
         (b)   PVC meeting ASTM D679, SDR 26 or ASTM F794 (18" and larger);
         (c)   HDPE meeting ASTM D3350 and ASTM F714;
         (d)   Concrete meeting ASTM C14, C76 or C655; and
         (e)   Other pipe materials specifically approved by the City PWD.
      (2)   Pressure piping. Pressure sewer piping (force mains) shall consist of PVC pressure pipe, ASTM D2241, Class 200 SDR-21, or AWWA C900 DR-18.
      (3)   Manholes.
         (a)   All manholes shall be constructed using pre-cast RCP, unless specifically allowed by the Public Works Department in writing. Structural strength shall withstand H-20 design load.
         (b)   All manholes installed at outfall lines must have PVC liner installed to protect against H2S gas.
      (4)   Manhole ring and cover. Manhole cover shall be stamped “Sewer.” The manhole ring/cover shall have an O-ring type gasket to protect the lid from inflow during storm events.
   (C)   Installation.
      (1)   Alignment and grade. Public sanitary sewers shall be installed with a straight alignment and grade between manholes as required in MPWSS.
      (2)   Location. Municipal wastewater system facilities shall be designed and constructed so that all such facilities are readily accessible for maintenance and repair.
         (a)   In addition, such facilities shall be situated so as to preclude the entrance of surface water into said facilities.
         (b)   All sewer mains shall be centered in the right-of-way or easement to the greatest extent possible.
      (3)   Depth.
         (a)   Sanitary sewers shall be buried to a depth sufficient to prevent freezing and shall have a minimum depth of four feet.
         (b)   Shallower depths may be allowed by the City PWD if suitable pipe insulating provisions are provided.
   (D)   Extension.
      (1)   Any extension of an existing city sanitary sewer main must be extended through the entire frontage length of the property to be served, with a standard manhole located at the terminus of the new sewer main.
      (2)   Sewer main extensions shall include all manholes, clean-outs and appurtenances deemed necessary by the city.
   (E)   Water line crossings.
      (1)   Crossings. A minimum of 18-inch vertical separation is required when a sanitary sewer main crosses above or below a water main, measured outside to outside of pipe.
         (a)   Please refer to MPWSS for further information on water line crossings.
         (b)   Less than an 18-inch vertical separation may be allowed when the gravity sewer at the crossing is made using a single 20-foot length of AWWA pressure pipe and the crossing is approximately 90° and the length of pipe is centered over the crossing.
            1.   Specific authorization from the Montana Department of Environmental Quality and the City PWD is required for a vertical separation of less than 18 inches.
            2.   No exception of the minimum 18-inch vertical separation requirement is permitted when the sewage pipe is a force main.
      (2)   Parallel. A minimum of ten-foot horizontal separation is required when a sanitary sewer main and water main are installed parallel.
(Prior Code, § 11.05.030.020) (Ord. 2019-9, passed 9-3-2019; Ord. 2021-15, passed 12-20-2021)
§ 11.05.030.030 SEWER SERVICE LINES.
   (A)   Materials.
      (1)   Gravity sewer service piping. Gravity sewer service piping shall consist of the following materials for the following situations:
         (a)   PVC meeting ASTM D3034, SDR-35 and 26 or PVC Schedule 40 - solvent weld or SBR gasket joint for normal installations. PVC Schedule 40 or cement lined ductile iron for installation within two feet of a building foundation;
         (b)   PVC Schedule 40 for water main or water service crossing; and
         (c)   PVC Schedule 40 with acrylonitrile butadiene (NBR) gaskets for installations in areas of hydrocarbon contamination.
      (2)   Pressure sewer service piping. Pressure sewer service lines shall consist of PVC pressure pipe, ASTM D2241, Class 200 SDR-21.
   (B)   Installation.
      (1)   (a)   All sanitary sewer service lines must be so arranged that the discharge from each separately-owned house premises or buildings on separate lots is a separate service line that connects to the main.
         (b)   The owner of each house or premises is liable for the charges for the wastewater service provided by the city to that owner’s house or premises.
      (2)   Sewer service lines shall be installed with a minimum of four feet of cover from the top of service pipe to finished grade.
      (3)   (a)   At all locations where sewer service lines are installed beneath new curb, the face of the curb shall be stamped with an “S” in lettering at least three inches tall, for marking the sewer service location.
         (b)   Tunneling of sewer service under curb, curb and gutter, sidewalks and the like is prohibited.
   (C)   Tapping city sewer.
      (1)   Any person desiring to make connection to the city’s water or sewer mains must make application in writing and pay for the cost of tapping in accordance with city policy, resolution or ordinance.
      (2)   (a)   All applications for service connection to the city’s wastewater system must be made at the front counter at city hall.
         (b)   Every such application must be made by the owner of the property to be served or the owner’s authorized agent and must include the nature of wastewater discharged into the system.
   (D)   Metering when not on city water. For new city sewer services which do not use the city water system or whose water consumption or wastewater discharge is not otherwise metered, the Public Works Department shall require the installation of a suitable metering device in order to determine an equitable charge for sewer services.
(Prior Code, § 11.05.030.030) (Ord. 2019-9, passed 9-3-2019; Ord. 2021-15, passed 12-20-2021)
§ 11.05.030.040 LIFT STATION.
   (A)   Capacity. The design capacity for a lift station shall be designed to a reasonable capacity based on similar flows from comparable zoned areas.
      (1)   The designer shall provide a table in the design report for the design capacity for each non-residential lot.
      (2)   Multi-family lots with a four-plex or greater are also considered commercial lots.
      (3)   (a)   During the building review process, a letter from an engineer must be submitted certifying that the sewer capacity is not greater than the original design capacity of the lot.
         (b)   If the capacity for the building is greater, additional capacity may be required.
   (B)   Building. The building shall be constructed of masonry block or similar high durability construction material.
      (1)   The building style must be compatible with the surrounding environment.
      (2)   The developer must install and provide access to the building so maintenance equipment can access the building and wet well.
   (C)   Landscaping. All lift stations must have low water/native vegetation and trees for the landscape screening with an irrigation system
   (D)   Fencing.
      (1)   All lift stations must be fenced with an eight foot high black vinyl coated chain link fence with two-strand barbed wire top.
      (2)   A minimum of two lockable gates must be provided; one for pedestrian access and one double gate that is able to swing 180° for allowing maintenance equipment to access the site.
   (E)   Wet well. Must be lined with a PVC coating or approved equal by the Public Works Department.
   (F)   Piping.
      (1)   (a)   All piping must be stainless steel within the wet well and ductile iron in the building.
         (b)   The pipe must also be configured to accommodate bypass pumping with a blind flanged tee after the last check valve.
      (2)   (a)   All fittings must be located out from under the lift station slab or located within a grated trench.
         (b)   All fittings must be accessible without damaging the building.
   (G)   Valving.
      (1)   All check valves must have external levers.
      (2)   A three-way Dezerik plug valve must be installed at the point the two pumping lines join.
   (H)   Safety.
      (1)   The wet well shall have a safety grate that is easily removable and integral to the hatch.
         (a)   The grate must be rated to at least 1,000 pound of loading.
         (b)   In addition to the hatch with a safety grate, removable handrails must also be supplied.
      (2)   (a)   A compressor and two full-face masks with a minimum 50-foot hoses will be required for a fresh air supply.
         (b)   SCBA will not be acceptable as a fresh air supply.
   (I)   Pumps. The pumps shall be Gorman-Rupp, Paco, Flyght or equal as approved by the PWD.
   (J)   Telemetry.
      (1)   The telemetry must be designed in accordance with the city telemetry design standards.
      (2)   If no standards exist, coordinate with the PWD.
   (K)   Pigging stations. Any lift station with a force main of more than 2,000 feet that does not have an existing flow of 50% of the design capacity, must have pigging stations for cleaning of the force main.
   (L)   Odor control. All vents from the wet well or force main must have a carbon filter.
   (M)   On-site generator. All lift stations must be supplied with an on-site generator.
      (1)   The generator must be a natural gas or diesel fuel unit located in a separate room within the building.
      (2)   An access door big enough to remove the generator for maintenance will be required.
(Prior Code, § 11.05.030.040) (Ord. 2019-9, passed 9-3-2019; Ord. 2021-15, passed 12-20-2021)
STORMWATER MANAGEMENT
§ 11.05.040.010 GENERAL.
   Storm drain systems shall be designed and constructed, in accordance with these engineering/design and construction standards and the Montana Department of Environmental Quality’s design circular DEQ-8, Montana Standards for Subdivision Stormwater Drainage, if the stormwater system is associated with a subdivision development.
(Prior Code, § 11.05.040.010) (Ord. 2019-9, passed 9-3-2019; Ord. 2021-15, passed 12-20-2021)
§ 11.05.040.020 STORM DRAINAGE PLANS AND REPORT.
   (A)   A storm drainage plan shall be submitted for development or redevelopment that includes the creation of more than 5,000 square feet of new impervious surface area.
   (B)   (1)   A detailed stormwater report shall be prepared by a registered professional engineer.
      (2)   The stormwater report shall contain the stormwater calculations and a discussion of the design rationale. The plan shall include the following:
         (a)   A map showing building site(s), open areas, drainage ways, ditches, culverts, storm sewers, inlets, storage ponds, roads, streets and any other infrastructure improvements which may affect drainage characteristics. The map shall also include identification of the various ground surfaces (i.e., vegetation, gravel and pavement) and their respective coverage (square feet);
         (b)   Topographic contours (one-foot intervals) and sufficient spot elevation data;
         (c)   Description of the ultimate destination of stormwater run-off from the project and an evaluation of its impact on down slope drainage facilities;
         (d)   Design calculations determining run-off quantities, storage requirements and peak rates;
         (e)   Description of water quality design method and calculations;
         (f)   A storm drainage facilities operation and maintenance plan. The plan shall:
            1.   Identify ownership of all facilities;
            2.   Establish a schedule for maintenance activities necessary to keep the system operationally effective; and
            3.   Identify the responsible party in charge of the specific maintenance duties.
         (g)   Details and specifications (including invert and other pertinent elevation information) for all storm drainage improvements, such as storm sewer, manholes, inlets, discharge structures, and retention/detention pond dimensions and volume, side slope, and top, bottom and maximum water surface elevations.
   (C)   Pre-development and post-development run-off calculations for sizing drainage facilities shall include:
      (1)   Depiction of the drainage area on a topographical map, with acreage indicated (the off-site contributing area must be included).
         (a)   Provide a pre-development topography and drainage basin map and a post-development topography and drainage basin map.
         (b)   The change in peak discharge and volume of surface water entering and leaving the subject property.
      (2)   The capabilities of all downstream drainage systems within one-fourth mile of the project site downstream boundary to handle the change in peak discharge and volume of surface water caused by the development.
      (3)   In areas where ground water may be a factor, the analysis shall include the effects of the ground water on the total storm drainage system proposed for the development.
(Prior Code, § 11.05.040.020) (Ord. 2019-9, passed 9-3-2019; Ord. 2021-15, passed 12-20-2021)
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