§ 6.6. Sewerage Facilities
6.6.1 General Requirements : The applicant shall install sanitary sewer facilities in a manner prescribed by the City of Santa Fe construction standards and specifications. All plans shall be designed and approved in accordance with the rules, regulations, and standards of the City of Santa Fe.
6.6.2 High-Density Residential and Nonresidential Districts : Sanitary sewerage facilities shall connect with public sanitary sewerage systems. Sewers shall be installed to serve each lot and to grades and sizes required by the Development Officer. No individual disposal system or treatment plants (private or group disposal systems) shall be permitted. Sanitary sewerage facilities (including the installation of laterals in the right-of-way) shall be subject to the specifications, rules, regulations, and guidelines of the City of Santa Fe.
6.6.3 Low- and Medium-Density Residential Districts : Sanitary sewerage systems shall be constructed as follows:
A. When a public sanitary sewerage system is reasonably accessible, the applicant shall connect with same and provide sewers accessible to each lot in the subdivision.
B. When public sanitary sewerage systems are not reasonably accessible but will become available within a reasonable time (not to exceed fifteen (15 years), the applicant may choose one of the following alternatives:
1. Central sewerage system with the maintenance cost to be assessed against each property benefitted. Where plans for future public sanitary sewerage systems exist, the applicant shall install the sewer lines, laterals, and mains to be in permanent conformance with such plans and ready for connection to such public sewer mains; or
2. Individual disposal systems, provided the applicant shall install sanitary sewer lines, laterals, and mains from the street curb to a point in the subdivision boundary where a future connection with the public sewer main shall be made. Sewer lines shall be laid from the house to the street line, and a connection shall be available in the home to connect from the individual disposal system to the sewer system when the public sewers become available. Such sewer systems shall be capped until ready for use and shall conform to all plans for installation of the public sewer system, where such exist, and shall be ready for connection to such public sewer main.
C. When sanitary sewer systems are not reasonably accessible and will not become available for a period in excess of fifteen (15) years, the applicant may install sewerage systems as follows:
1. Medium-Density Residential Districts . Only a central sewerage system may be constructed. No individual disposal system will be permitted. Where plans exist for a public sewer system to be built, for a period in excess of fifteen (15) years, the applicant shall install all sewer lines, laterals, and mains to be in permanent conformance with such plans and ready for connection to such public sewer main.
2. Low-Density Residential District : Individual disposal systems or central sewerage systems shall be used.
6.6.4 Mandatory Connection to Public Sewer System : If a public sanitary sewer is accessible and a sanitary sewer is placed in a street or alley abutting upon property, the owner of the property shall be required to connect to the sewer for the purpose of disposing of waste, and it shall be unlawful for any such owner or occupant to maintain upon any such property an individual sewage disposal system.
6.6.5 Individual Disposal System Requirements : If public sewer facilities are not available and individual disposal systems are proposed, minimum lot areas shall conform to the requirements of the Santa Fe Zoning Ordinance and percolation tests and test holes shall be made as directed by the Development Officer and the results submitted to the Galveston County Health Department. The individual disposal system, including the size of the septic tanks and size of the tile fields or other secondary treatment device, shall also be approved by the Development Officer.
6.6.6 Design Criteria for Sanitary Sewers :
A. General Guidelines : These design criteria are not intended to cover extraordinary situations. Deviations will be allowed and may be required in those instances when considered justified by the Planning Commission.
B. Design Factors : Sanitary sewer systems should be designed for the ultimate tributary population. Due consideration should be given to current zoning regulations and the Santa Fe Comprehensive Plan. Sewer capacities should be adequate to handle the anticipated maximum hourly quantity of sewage and industrial waste together with an adequate allowance for infiltration and other extraneous flow. The unit design flows presented below should be adequate in each case for the particular type of development indicated. Sewers shall be designed for the total tributary area using the following criteria:
Design Criteria for Sanitary Sewers
Land Use Categories
Unit Design Flows
One and Two-Family Dwellings .02 cubic feet per second
(c.f.s.)/acreApartments One and Two Story .02 c.f.s./acre Three through Six Story .03 c.f.s./acre Commercial Small Stores, Offices, & Miscellaneous .02 c.f.s./acre Shopping Centers .02 c.f.s./acre High Rise As directed by the Development Officer Industrial As directed by the Development Officer These design factors shall apply to watersheds of 300 acres or less. Design factors for watersheds larger than 300 acres and smaller than 1,000 acres shall be computed on the basis of a linear decrease from the applicable design factor for an area of 300 acres to a design factor of .01 c.f.s./acre for an area of 1,000 acres unless otherwise directed by the City of Santa Fe Development Officer. Design factors for watersheds larger than 1,000 acres shall be .01 c.f.s./acre unless otherwise directed by the Development Officer.
C. Maximum Size : The diameter of sewers proposed shall not exceed the diameter of the existing or proposed outlet, whichever is applicable, unless otherwise approved by the Development Officer.
D. Minimum Size : No public sewer shall be less than eight (8) inches in diameter.
E. Minimum Slope : All sewers shall be designed to give mean velocities when flowing full of not less than 2.0 feet per second. All velocity and flow calculations shall be based on the Manning Formula using an N value of 0.013. The design slopes shall be evenly divisible by four (4). The slopes shall be minimum for the size indicated. Exceptions to these minimum slopes shall be made at the upper end of lateral sewers serving under thirty (30) houses.
Minimum Slopes for Sewer Size Indicated
Sewer Size in Inches Minimum Slope (feet per 100 feet) 9 .33 10 .25 12 .20 15 .15 16 .11 21 .09 24 .08 F. Alignment : All sewers shall be laid with straight alignment between manholes, unless otherwise directed or approved by the City of Santa Fe Development Officer.
G. Manhole Location : Manholes shall be installed at the end of each line; at all changes in grade, size, or alignment; at all intersections; and at distances not greater than 500 feet for sewers 15 inches and smaller, and 500 feet for sewers 18 inches in diameter and larger.
H. Manholes : The difference in elevation between any incoming sewer and the manhole invert shall not exceed 12 inches except where required to match crowns. The use of drop manholes will require approval by the City of Santa Fe Development Officer, but in no case shall the diameter be less than forty eight (48) inches. The minimum inside diameter of the manholes shall conform to those specified by the City of Santa Fe Development Officer. Inside drop manholes will require special considerations; however, in no case shall the minimum clear distance be less than that indicated above. When a smaller sewer joins a larger one, the crown of the smaller sewer shall not be lower than that of the larger one. The minimum drop through manholes shall be 0.2 feet.
I. Sewerage Locations : Sanitary sewers shall be located within street or alley rights-of-way unless topography dictates otherwise. When located in easements on private property, access shall be to all manholes. A manhole shall be provided at each street or alley crossing. End lines shall be extended to provide access from street or alley right-of-way when possible. Imposed loading shall be considered in all locations. Not less than six (6) feet of cover shall be provided over the top of pipe in street and alley rights-of-way or three (3) feet in all other areas.
J. Cleanouts and Lampholes : Cleanouts and lampholes will not be permitted.
K. Water Supply Interconnections : There shall be no physical connection between a public or private potable water supply system and a sewer which will permit the passage of any sewage or polluted water into the potable supply. Sewers shall be kept removed from water supply wells or other water supply sources and structures.
L. Relation of sewers to Water Mains : A minimum horizontal distance of ten (10) feet shall be maintained between parallel water and sewer lines. At points where sewers cross water mains, the sewer shall be constructed of cast iron pipe or encased in concrete for a distance of ten (10) feet in each direction from the crossing, measured perpendicular to the water line. This will not be required when the water main is at least two (2) feet above the sewer.