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HomeMy WebLinkAbout467 4010 RESOLUTION NO. 467 A RESOLUTION OF THE CITY COUNCIL OF THE TOWN OF LOS ALTOS HILLS ADOPTING STANDARDS FOR SEPTIC TANK CONSTRUCTION AND MAINTENANCE. RESOLVED, by the City Council of the Town of Los Altos Hills that those certain standards for septic tank':construc- tion and maintenance, a true copy of which is annexed hereto marked EXHIBIT A and by this reference incorporated herein, be, and thesame are hereby adopted as the standards for the Town of Los Altos Hills . * * * * * I HEREBY CERTIFY that the foregoing is a full, true and correct copy of a resolution duly passed and adopted by the City Council of the Town of Los Altos Hills, California, at a meeting thereof held on the . 1.5m day of July, 1968, by the following roll call vote: AYES: Councilmen Benson, Davey, Fowle, Helgesson Mayor Aiken NOES : None ABSENT: None ATTEST: , /' City lerk APPROVEDr.:, 1 /' Mayor IORIO & FAISANT TTORNEYS AT LAW THIRD STREET S ALTOS, CALIF. .448-82OO Resolution #467 411 EXHIBIT_ "A" - • TOWN STANDARDS FOR PRIVATE SES'/AGE DISPOSAL These standards are• minimum standards intended to provide adequate facilities for sub-surface disposal of sewage under average usage and • general conditions. Where proposed usage or known topographic, soil • permeability, drainage or other physical features will produce conditions • that are not average or general, these minimum requirements shall be • exceeded as deemed necessary by the Health Officer. A. DEFINITIONS 1., Septic Tk Disposal System: Septic tank disposal system shall ' mean any system for .the private disposal of sewage or other liquid • waste including but not limited to a septic tank and disposal. field. 2. Septic Tank: Septic tank shall mean a watertight tank designed to receive sewage or other liquid waste and to provide sedimentation • • and partial sludge digestion. • 3. Disposal'Field: Disposal field shall mean a system of underground drain or leach lines laid in gravel lined trenches for the purpose of receiving effluent from the septic tank for percolation into the adjoining ground. 4. Diversion Box: Diversion box shall mean a structure designed to permit introduction of septic tank or filter effluent into alternate sections of. the disposal field, so that one.•or more sections of the disposal field may undergo an extended resting period. 5. , Dosing Chamber: Dosing chamber shall mean a watertight compartment or structure provided with float controlled automatic pump or auto- matic siphon designed to receive the effluent from the septic tank • and from.whic:h effluent will be discharged intermittently in doses to either a filter or to the disposal field. 6. Filter: Filter shall mean a bed of graded filtering material through which septic tank effluent posses prior to its introduction into the disposal field. • • . S E. SEPTIC TANK DISPOSAL SYSTEM Each septic tank disposal system shall consist of the following components: (1) septic tank, (2) diversion box, and (3) disposal field. It may also include either or both of the following components: (1) dosing chamber, and (2) filter. No portion of the septic tank disposal system shall be located within 10 feet of a foundation, 10 feet of a property line, 10 feet of a swimming pool, or 100 feet of a water well, except that a septic tank may be located within 5 feet of a foundation. 1.- Septic Tank: The septic tank shall be constructed of concrete • or masonry units. Tanks shall have smooth finished walls and bottom at least 4 inches thick. When concrete blocks, other than approved interlocking blocks or precast masonry.units are used, they shall be waterproofed, laid with cement mortar, and • shall be reinforced with half-inch steel bars vertical and horizontal on two-foot centers. All hollow units shall be poured solid with cement mortar. • The septic tank shall have a minimum water capacity of 1,500 gallons measured at flowline and shall be constructed with two compartments. The capacity of the second compartment shall be one-half of the capacity of the first compartment. The general configuration of the tank shall be as shown in Figure 1. Dimensions for tank capacities not shown or deviations from, . •• the dimensions shown must be approved by the Health Officer. The septic tank, and outlet and inlet connections, shall be watertight. The septic tank top may be of two layers of two-inch redwood board covered with building.paper and at least 6-inches of dirt .to form a water--and.odor seal. Concrete tanks with poured concrete covers need not be covered with a dirt seal. Each poured concrete cover • shall have tkro manholes, one over the inlet and one over the out- let, each at least 22 inches in diameter, and with tight fitting • lids. These lids shall be provided with iron U-bolts, or reinforcing rod handholds, to facilitate lifting. Inlet.and outlet baffles may be. of one-inch redwood board mortared into side wall notches. Vitrified clay septic tank tees or vitrified clay septic tank ells cast in place may be substituted for these inlet and outlet baffles. See Figure 1. 111 . 2. Disposal Field: In_ addition to the general limitations upon location of any portion of a septic tank disposal system, no portion of a r13ovoszl field shall be located in a filled ground area, r,Y- t:ithin 50 feet of any creek, drainage ditch bank or any cut slope bank below the elevation of the disposal field. Leaching lines may not be laid in existing or proposed paved surface areas or areas subject to vehicular traffic. • The disposal field shall consist of leaching lines.laid in gravel lined trenches. Leaching line tile shall be of clay, not less than 4 inches in diameter, not more than l2 inches long and shall be laid with Ye." to j2" openings at joints. Perforated, bituminous, plastic or other types of leaching line may be used when approved by . . the Health Officer. Leaching lines shall be laid no closer than 8 feet on centers. The total lineal length of trench shall be determined from subsurface soil analysis based upon observations of test borings and percolation tests. Boring requirements and percolation test procedure shall be / • as- -described in Sections 6 and 7. Previous soil mantle shall extend • ( • for a depth of at least 3 focb below the proposed trench bottom. The water table shall not lie within three feet of the trench bottom. • Required depth of trench shall. be 6 feet. The Health Officer may permit modification of this depth. Trench width shall be not less than twelve inches .and not more than eighteen inches except that all of the trench in any one private sewage disposal system shall be of the same width. The trench bottom . shall be carefully excavated to level grade. Trench walls or those . portions of trench walls which have been sealed by the excavating . equip;=nt shall be scarified to the- satisfaction of. the Health. • Officer prior to placing of gravel. The excavated trench shall be filled with 3/4" to lh ' gravel from the bottom to the level of the base of the tile which shall be laid to grade. Gravel shall be added • to a depth of 4 inches above the tile, covered with building paper • to prevent clogging with earth and the remainder- of the trench backfilled. There shall be at least twelve inches of backfill below finished grade of adjoining ground surface. Cud ( The backfilled trench should be well tamped and be 'over--filled with 4 inches to 8 inches of earth to prevent depressions due to settling of earth (trench line depressions may collect storm water, leading to premature saturation of the absorption field and possibly to trench washouts). Trucks and heavy grading equipment shall be excluded from the disposal area unless special provision is made • to support the weight. •See Figure 2. Sections of disposal fields located on hillsides at different elevations shall be separated by undisturbed earth dams at least 2 feet across at the ground surface. There shall be a pipe transfer from the .terminus of the trench at one elevation to the inlet of the ztrench at a lower elevation. Section connecting lines or pipe transfers shall be 4-inch tight-joint sewers with connections to the distribution tiles in ,adjacent sections or to:a-drop box. The crown of the transfer shall be at least 2 inches •• below the top of the gravel. Transsfe-r.--lines•shall be so constructed as to insure an undisturbed �l block of earth between sections. The trench connecting the transfer =pipe and the preceding asborption section shall be dug no deeper • than the top of the soil gravel interface. The transfer line shall rest on undisturbed earth and backfill shall be carefully tamped. Inspection. wells consisting of four inch pipe placed vertically • in 'the trench from the bottom to the surface of the ground and provided with a cap or plug shall be placed at the terminus of each trench or/and at such other points as will make possible a check of the water table elevation within the trench at the inspection well points. These sampling wells shall be adequately marked to permit ready location and provide protection from damage. 3. Dosing Chamber: The dosing chamber where employed shall be constructed . of concrete or masonry units and may be an independent structure or a third compartment of the septic tank structure. It -shall have smooth finished walls and bottom at least 4 inches thick. When concrete block or other than approved interlocking blocks or masonry units are used, • -4- • • 111 • they shall be waterproofed., laid with cement mortar and shall be reinforced with half inch steel bars vertical and horizontal on two foot centers. All hollow units shall be poured solid with cement • • mortar. . The closing chamber top may be of two layers of two-inch redwood board • covered with building paper and at least 6 inches of dirt to form a water and odr..sea1. Concrete tanks with poured_ concrete covers need not be covered with a dirt seal. Each poured cover shall have two manholes, one over the inlet and one over the outlet, each at least 22 inches in diameter- and with tight fitting lids. These lids Sua.11 be fitted with iron U-bolts or reinforcing, rod handholds to facilitate lifting. The dosing chamber shall be equipped with an automatic float controlled submersible pump having a capacity of at least 15 gallons per minute or an automatic siphon at least 3 inches • in size. The pump control shall be set to start the pump at a water • level of 6 inches below the inlet and to shut the pump off at a water -7-It level of 6 inches above the bottom of the tank. • QThe dosing tank top or manhole covers shall extend •to grade and be-constructed to give easy access to the dosing tank and to permit periodic inspection and maintenance. The dosing chamber if located between the septic tank and the leaching field shall have a minimum capacity equal to the approximate void volume of the leaching field . or section of-. leaching field to which it discharges. The dosing chamber if located between the septic tank and a 'filter and used to dose the filter shall have a minimum capacity not less than 400 gallons. • 4. Filter: The filter, if used, shall be contained by side walls con- structed of concrete or masonry units or irrigation heart grade redwood. The minimum capacity shall be based upon the estimated • maximum daily domestic water usage, and shall not be less than 400 gallons per day per residence. The filter media shall be selected for durability and effective surface area. An application for a proposed filter shall be accompanied with supporting design data and detailed specifications. • • -5- • • C5. .Diversion Box: The diversion box shall be located at the beginning of the disposal field and shall be connected' to the septic tank by a tight line placed on undisturbed soil or otherwise installed to • • minimize the danger of breakage or displacement. . The box shall be kept to a minimum size necessary to accommodate the inlet and the outlets but not less than 18 inches in either width or length. The box shall extend to the surface of the ground and be fitted with • an easily removable lid to permit periodic inspection and alternation of outlet in use. There shall be at least two outlets each cod to independent sections of the disposal field. Each outlet shall • be constructed to permit opening or closing of a gate so that only one -outlet will be- in use at.any particular time. • . 6. Bori�n Requirements: There shall be at least one test boring at • each proposed disposal field site:. These borings shall be to _rock, • : . • hardpan, water or. to a maximum depth of nine feet.. 7. Percolation Tests: .There shall be at least three percolation tests at the site of each proposed disposal field. Tests shall be made in holes having a diameter of not less than 8" or more than10 . . Test holes are not to exceed 43" in depth. Wall surfaces in holes may be scarified if there is sealing during digging. Test .holes shall be flooded at least once 24 hours before the per- f ormance of the test. The Health Officer may require additional - - • presoaking. The initial test reading. shall .be .at a depth.of 12 .inches . below .grade. Successive readings shall be made- at hourly intervals until at least two successive falls are egiial . If the fall at any reading exceeds one-half inch, the water level in the hole shall be brought up to the 12 inch mark before the start of the next hourly • interval. The Health Officer may specify other test reading intervals. 8. Standards for Alternate Private Sel•rage Disposal Systems: 4pplications for permits to construct, maintain and operate private sewage disposal systems, , using alternate methods or designs, will be considered by • the Health Officer upon request by the applicant. Each application • shall be submitted with 5 copies of plans and specifications and engineering data. 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