[26 Pa.B. 1491]
[Continued from previous Web Page]
INDIVIDUAL RESIDENTIAL SPRAY IRRIGATION SYSTEM STANDARDS § 73.161. General.
(a) Individual residential spray irrigation systems shall be designed by a registered professional engineer with expertise in sanitary sewage system design or by a currently certified sewage enforcement officer who has successfully completed a Department-sponsored course on design of this system. Copies of the plans and specifications along with the designer's report shall be attached to the applicant's copy, local agency's copy and the Department's copy of the application for sewage permit.
(b) Standards for individual residential spray irrigation systems described in the following sections shall also be met: §§ 73.1, 73.12--73.17, 73.21, 73.31, 73.32 and 73.41--73.46.
§ 73.162. Intermittent sand filters.
(a) There are two types of intermittent sand filters available for use with individual residential spray irrigation systems. The standards for free access sand filters and buried sand filters are included in this section.
(b) Free access sand filters shall meet the following standards:
(1) Filter. The filter shall be constructed in a tank meeting the following specifications:
(i) The surface area of a filter tank shall be a minimum of 40 square feet for systems using an aerobic treatment tank and serving a single family residence of three bedrooms or less. The filter area shall be increased by 10 square feet for each additional bedroom over three.
(ii) Systems proposing the use of a septic tank to serve a single family dwelling of three bedrooms or less shall be designed using two filter tanks or a single tank with two chambers. Each tank or chamber shall have a surface area of 40 square feet. The filter area of each filter shall be increased by 10 square feet for each additional bedroom over three.
(iii) Tanks shall be watertight and made of a sound, durable material which is not subject to excessive corrosion or decay.
(iv) Concrete tanks shall have a minimum wall thickness of 2 1/2 inches and be adequately reinforced.
(v) Precast slabs used as tank tops which support the access covers and risers shall have a thickness of at least 3 inches and be adequately reinforced.
(vi) Tanks shall have a uniform depth throughout the tank and may not be less than 5 feet in depth, nor greater than 7 feet.
(vii) Tanks shall be designed and constructed so that the depth from the cover to the top of the sand layer is a minimum of 24 inches.
(viii) Access to grade shall be provided by a minimum of two access openings. These access openings shall be a minimum of 36 square inches and provide access to the entire surface of the filter.
(ix) The tank wall shall be extended a minimum of 6 inches above final grade.
(x) Access covers shall be insulated against severe weather, secured by bolts or locking mechanisms, prevent water infiltration and the entrance of debris, and be lightweight to facilitate routine maintenance.
(2) Media. Sand suppliers shall provide certification, in writing, to the sewage enforcement officer and permittee, with the first delivery to the job site, that the sand to be supplied meets Department of Transportation specifications for Type A sand in Section 703.1(c), Table A, Fine Aggregate listed in the Department of Transportation Specifications Handbook. Limestone sand may not be used.
(3) Construction. The sand filter shall be constructed according to the following standards:
(i) A 4-inch diameter perforated underdrain pipe with a minimum 2,500 pound crash test specification shall be placed on the bottom of the tank.
(ii) Two rows of perforations between 1/2 to 3/4 inch in diameter shall be drilled in the underdrain pipe at 6 inch intervals and the pipe shall be placed so the perforations face downward and the rows are approximately 45° from each other.
(iii) Aggregate shall be placed around the underdrain to a total depth of 5 inches from the bottom of the tank.
(iv) A minimum depth of 4 inches of pea gravel (1/4 to 1/8 inch in diameter) shall be placed over the aggregate underdrain material.
(v) Sand shall be placed over the pea gravel to a depth of at least 24 inches.
(vi) The sand in the filter shall be no greater than 36 inches deep.
(vii) The central distribution system shall be designed and installed to convey a minimum 100 gallon flood dose of effluent to the surface of the sand filter. A high water alarm shall be installed in the filter tank which produces an audible and visual alarm when effluent backs up on the filter surface to 12 inches above the surface of the sand.
(viii) When two filters or chambers are required to treat septic tank effluent, the duplicate units shall be flooded alternately.
(ix) The central distribution piping shall be 2 inches in diameter.
(x) The height of the central distribution system's effluent outlet above the sand surface shall allow for the installation of a splash plate and the maximum flooding depth of the sand filter.
(xi) A concrete splash plate shall be located under each effluent outlet to prevent scouring of the sand surface. Movement of the splash plate during the flooding operation shall be prevented.
(c) Buried sand filters shall meet the following standards:
(1) Location.
(i) Buried sand filters may not be installed in areas where bedrock is encountered above the proposed depth of the sand filter, or where the seasonal high groundwater table rises above the proposed depth of the sand filter unless a concrete bottom and sides are used.
(ii) A buried sand filter may not be constructed in unstabilized fill.
(2) Size.
(i) The size of the sand filter shall be determined on the basis of the appropriate application rate and the estimated daily sewage flow in accordance with § 73.16(a) (relating to absorption area requirements) but the sand filter area may not be less than 300 square feet for use with either an aerobic treatment tank or septic tank with solids retainers units.
(ii) For a single family residence, the minimum sand filter area shall be based on a maximum hydraulic loading of 0.67 gallons per day per square foot.
(3) Media.
(i) At least 2 inches of clean aggregate shall surround underdrains and distribution pipes. A layer of porous geotextile material (such as polypropylene, polyester, nylon) shall be placed on top of both layers of aggregate to prevent migration of soil or sand into the aggregate.
(ii) At least 24 inches of clean sand shall be placed over the underdrain aggregate. The sand shall meet the specifications in subsection (b)(2).
(iii) The minimum depth of earth cover over the coarse aggregate in all installations shall be 12 inches. When the top of the aggregate is less than 12 inches from the undisturbed soil surface, the soil cover shall extend beyond the filter area by at least 3 feet on all sides. The soil over the sand filter shall be so graded that surface water will run off, consist of soil suitable for the growth of vegetation and be seeded to control erosion.
(4) Underdrain piping.
(i) Underdrain piping shall be laid on a grade of 3 to 6 inches per 100 feet sloped to the outfall pipe.
(ii) Underdrain piping shall be positioned between the distribution laterals to maximize effluent travel through the filter sand.
(iii) Underdrain piping holes shall be equal or greater in number and size to the distribution piping holes.
(iv) Underdrain piping shall have two rows of holes placed at approximately a 45° angle from each other along the bottom half of the pipe.
(v) The outfall pipe from the underdrain header shall have an antiseep collar and bentonite clay plug, or a leak proof boot sealed as per manufacturer's instructions to the subsurface sand filter liner.
(5) Filter base and liner. The base of the filter shall be sloped to the underdrain pipe a maximum of 1%. An impervious liner of hyplon, polyvinyl chloride or polyethylene sheeting of 20 millimeter thickness or equal shall be installed on a tamped earth base to prevent seepage to the groundwater unless a concrete bottom and sides are used. A 2- inch layer of sand or a layer of 10 ounce porous geotextile material shall be provided on each side of the liner to prevent punctures and tears. Seams shall be made according to manufacturer's specifications.
(6) Distribution of effluent to the buried sand filter shall meet the requirements of §§ 73.44--73.46 (relating to pressurized distribution design; dosing tanks; and closing pumps).
§ 73.163. Spray fields.
(a) The maximum slope of the undisturbed soil where a spray field may be permitted is 25%.
(b) Individual residential spray irrigation system spray fields are not permitted on:
(1) Soils with evidence of a seasonal high water table at less than 10 inches from the surface.
(2) Soils with rock formations at less than 16 inches from the surface.
(3) Floodplain soils or floodprone areas unless any required encroachment permits have been obtained from the Department and compliance with local ordinances pertaining to flood areas.
(4) Agricultural areas in active production of food for human consumption.
(c) Slopes shall be as follows:
(1) Open, grassed areas--limited to 12%
(2) Forested areas--limited to 25%
(3) Nonfood producing agricultural areas--limited to 4%
(d) Spray field sizing based upon soils characteristics shall be in accordance with Table B in § 73.16(c) (relating to absorption area requirements).
(e) Construction shall be as follows:
(1) The area upslope of the spray field shall be graded or bermed to divert upland drainage from the spray field site.
(2) The downslope portion of the permitted spray field shall be graded or bermed to retain effluent on the permitted spray site.
(3) The permitted spray field shall be covered with vegetation.
(4) Construction activity within the spray field site should be conducted in a manner which will minimize earth disturbance and compaction.
§ 73.164. Chlorine contact/storage tanks.
(a) The minimum liquid capacity of an individual residential spray irrigation system storage tank serving a three bedroom dwelling, shall be 2,000 gallons. The tank size shall be increased an additional 500 gallons for each additional bedroom over three. Additional increases in size may be required where more than 5 days storage may be needed due to climatic conditions or when spray fields are located in floodplain or floodprone areas.
(b) Storage tanks used in individual residential spray irrigation systems shall meet the construction standards in § 73.45(1) and (4)--(6) (relating to dose tank). When more than one tank is used, the tanks shall be connected together at the bottom to equalize the liquid level in the tanks.
§ 73.165. Disinfection.
(a) Disinfection of effluent is required prior to spraying. The disinfection shall be by chlorination and shall produce an effluent which will contain a concentration not greater than 200/100 milliliter of fecal coliform organisms in a single sample. Disinfection units shall be installed in accordance with the manufacturer's specifications. Disinfection units shall be reliable, able to disinfect sewage effluent and be easily maintained by the property owner.
(b) A chlorinator shall be designed to maintain a chlorine residual of 1 ppm to 2 ppm and provide for a 30 minute contact time.
(1) When an erosion chlorinator is proposed, the base of the unit may be placed no deeper than 36 inches below finished grade or to a shallower depth which allows access for maintenance.
(2) When a lift pump is used to keep the unit no deeper than 36 inches below finished grade, the pump shall have a discharge rate that does not exceed the manufacturer's specifications for the erosion chlorinator and shall meet the appropriate specification of § 73.46 (relating to dosing pumps, siphons and life station pumps).
(3) Chlorine contact time may be obtained using a separate chlorine contact tank or in-line chlorination followed by the storage tank.
(4) Chlorinators shall be housed separately from chlorine contact tanks or storage tanks unless the tanks are specifically designed to house chlorinators.
§ 73.166. Design of pressure distribution for individual residential spray irrigation systems.
(a) Design of pressure distribution in an individual residential spray irrigation system shall comply with the following:
(1) Conveyance of effluent from the storage tank to the spray field shall be through a delivery pipe sized to minimize friction loss.
(2) Check valves shall be prohibited on delivery lines. Air relief valves may be placed at high points in the delivery line to prevent air locks.
(3) The delivery line and lateral shall be designed so that the effluent will drain back to the storage tank.
(4) Individual laterals shall be sized to minimize friction loss. The hydraulic loss (friction and elevation changes) within a lateral shall be less than 20% of the operating head of the sprinklers.
(5) Design of laterals should include consideration of measures to prevent freezing of lines.
(6) Spacing of laterals and sprinklers shall provide for uniform distribution of the effluent over the spray field in accordance with the manufacturer's specifications for spray nozzles proposed for use.
(7) Design of the spray field shall be based on the manufacturer's sprinkler specifications listing operating head, wetted diameter, nozzle size and discharge rate which shall be attached to the system design.
(8) Sprinklers shall be installed on risers 18 inches to 5 feet above grade level.
(9) Sprinklers shall be kept clear of obstructing vegetation for a radius of 5 feet.
(10) The design head of the sprinkler may not exceed the manufacturer's specifications for each system component.
(11) The minimum pump capacity shall equal the total discharge from all sprinklers when operating at design head.
(12) Total pump head shall be calculated by addition of all losses incurred due to elevation changes, pipe and fitting friction losses and the design head of the sprinkler.
(13) The effluent shall be discharged to the spray field once per day. A manual override shall be installed in the system to allow interruption of this spray cycle when weather conditions are not conducive to spraying.
(14) The permittee shall conduct a test pressurization of the completed spray field in the presence of the sewage enforcement officer prior to covering the piping system from view. During the test, the sewage enforcement officer shall confirm that all joints are water tight, the design head is achieved and the manual override is functional.
§ 73.167. Operation and maintenance.
Individual residential spray irrigation systems require periodic maintenance by the property owner and entity established under § 72.25(h) (related to permit requirements for operation and maintenance of individual residential spray irrigation systems). Without proper maintenance, system components will fail and pollution or a public health hazard will occur. This may result in costly repairs and civil penalties. The system designer shall provide an operation and maintenance manual to the permittee which shall include, as a minimum, the following standards for operation and maintenance which shall be met by the permittee:
(1) Septic tanks, dosing tanks, lift tanks and chlorine contact/storage tanks shall be inspected for structural integrity of the tank, inlet and outlet baffels, solids retainer, pumps, siphons and electrical connections.
(2) Aerobic tanks shall be inspected for structural integrity of the tank, inlets and outlet baffels, buoyed solids retainer, pumps, siphons and electrical connections. The inspection and concurrent pumping of excess solids shall be conducted in accordance with manufacturer's and National Sanitation Foundation requirements.
(3) Free access sand filters, buried sand filters chlorinators, the pressurized spray irrigation plumbing and spray nozzles and the spray fields shall be inspected periodically by the property owner and every 6 months by the maintenance entity established under § 72.25(h). Each component shall be inspected for compliance with the following standards:
(i) Chlorine residual sampled after the contact/retention tank shall be maintained at a concentration of at least 1.0 ppm.
(ii) The chlorinator shall be functioning within the specifications of the manufacturer. Bridging of chlorine tablets may not be occurring.
(iii) Solids may not be accumulated on the surface of the sand in the free access sand filter nor may 12 inches of effluent be ponded over the sand. The high water alarm shall be functional.
(iv) The surface of the free access sand shall be raked and porous and any sand removed shall be replaced with sufficient clean sand to maintain the depth at a minimum of 24 inches.
(v) The plumbing in the free access sand filter tank shall be functional and free of leaks and splash plates shall be in place.
(vi) The free access sand filter tank and cover shall be structurally sound and unauthorized access equipment shall be in place. Insulation shall be in place.
(vii) The areas of the buried sand filter shall be free of ponded effluent and downgradient seepage.
(viii) The plumbing to the spray field shall be functional and free of leaks.
(ix) The spray nozzles shall be functioning within the design specifications and the extent of the designed wetted perimeter of each nozzle.
(4) A laboratory shall test the discharge to the system for fecal coliforms, biological oxygen demand (BOD), suspended solids and chlorine residual to determine compliance with Chapter 72 (relating to administration of sewage facilities permitting program). At least annually, a copy of the tests results along with the most recent inspection of the system by the maintenance entity established under § 72.25(f) shall be sent to the local agency.
[Pa.B. Doc. No. 96-526. Filed for public inspection March 29, 1996, 9:00 a.m.]
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