Small Flow Treatment Facilities Manual

Transcription

1 Small Flow Treatment Facilities Manual TECHNICAL GUIDANCE NUMBER COMMONWEALTH OF PENNSYLVANIA Department of Environmental Protection For more information, visit DEP s Web site at Keyword: Wastewater.

2 DEPARTMENT OF ENVIRONMENTAL PROTECTION Bureau of Water Standards and Facility Regulation DOCUMENT NUMBER: TITLE: Small Flow Treatment Facilities Manual EFFECTIVE DATE: December 2, AUTHORITY: POLICY: PURPOSE: APPLICABILITY: DISCLAIMER: The Clean Streams Law (35 P.S ) and Title 25 Pa. Code Chapter 91. To improve and preserve the purity of the waters of the Commonwealth for the protection of public health, animal and aquatic life, and for recreation. To amend and clarify and to add additional treatment facilities to the previous guidance regarding the design, permitting, installation, operation and maintenance of domestic wastewater treatment facilities with flows not greater than 2,000 gallons per day (gpd). This policy provides major amendments to the previous guidance regarding the design and construction of small flow treatment facilities. The policies and procedures outlined in this guidance are intended to supplement existing requirements. Nothing in the policies or procedures shall affect regulatory requirements. The policies and procedures herein are not an adjudication or a regulation. There is no intent on the part of DEP to give the rules in these policies that weight or deference. This document establishes the framework within which DEP will exercise its administrative discretion in the future. DEP reserves the discretion to deviate from this policy statement if circumstances warrant. PAGE LENGTH: 37 pages LOCATION: Volume 33, Tab 24 DEFINITIONS: Small Flow Treatment Facility (SFTF): An individual or community sewerage system designed to adequately treat sewage flows not greater than 2,000 gpd using a stream discharge or other disposal methods approved by DEP / FINAL December 2, 2006 / Page i

3 TABLE OF CONTENTS I. Introduction...1 A. Systems Covered by this Manual...1 B. Systems Not Covered by this Manual...1 C. Advantage of Using the Systems in this Manual...2 II. Design Requirements...3 A. General...3 B. Building Sewer...4 C. Raw Sewage Pumping...5 D. Treatment Tanks Septic Tank(s) Aerobic Treatment Tank...9 E. Filter Distribution System...11 F. Filtration System Subsurface Sand Filter Recirculating Subsurface Sand Filter CO-OP RFS III Recirculating Filter Accessible Sand Filter System...23 G. Disinfection Chlorination Ultraviolet (UV) Radiation...27 H. Outfall Sewer...29 III. Installation...29 IV. Operation and Maintenance...30 V. Monitoring and Reporting Requirements...31 Appendices A. Sewage Flows...32 B. Minimum Maintenance Chart...34 Page / FINAL December 2, 2006 / Page ii

4 I. INTRODUCTION A. Systems Covered By This Manual 1. This manual provides guidance for the design, permitting, installation, operation and maintenance of SFTFs. These facilities are intended to serve single-family residences, duplexes and small commercial establishments that generate 2,000 gallons per day (gpd) or less of domestic wastewater with influent concentrations at or below 50 mg/l ammonia as nitrogen, 85 mg/l organic nitrogen, 85 mg/l total kjeldahl nitrogen, 1,200 mg/l total solids, 350 mg/l suspended solids and 400 mg/l 5-day Biochemical Oxygen Demand (BOD 5 ). The influent must be free of any substances that could produce floating material, oil, grease, scum and substances which produce color, tastes, odors, turbidity or settle to form deposits after treatment (Title 25 Pa. Code, 93.6). The SFTFs listed in this document have been monitored over an extended period of time under the siting, design, installation, operation and maintenance standards listed for each technology. The monitoring results document that these systems are capable of producing an effluent suitable for discharge without polluting surface waters and/or groundwater, as appropriate to each listing. All plans and specifications must be prepared by a licensed professional engineer authorized to practice in this Commonwealth in compliance with Chapter 91 of the Department of Environmental Protection s (DEP) regulations. 2. The treated sewage effluent from an SFTF may be discharged to a stream or dry stream channel. The feasibility of each of these discharge options is site-specific. The determination of which option is best in a specific case requires evaluation by a professional knowledgeable in this area. B. Systems Not Covered By This Manual Proposals for systems that may appear to be the same or similar to the systems described in this manual may not be eligible for the permits described in this manual for a number of reasons: 1. Soils suitable for use of an onlot system. An SFTF may only be used when soils are documented as not suitable for the installation of individual or community onlot sewage treatment systems permitted by local agencies under the Pennsylvania Sewage Facilities Act (see Title 25 Pa. Code 71.64). The first step in assessing any lot for potential SFTF use is, therefore, to have the lot tested for an onlot system. This testing is done by the Sewage Enforcement Officer (SEO) employed by the local agency established under the Pennsylvania Sewage Facilities Act serving that municipality. A denial letter and accompanying soils report must be obtained from the local agency to document that the lot is unsuitable for onlot system use. A copy of the denial letter and all soils information must be attached to any application proposing the use of an SFTF submitted to DEP / FINAL December 2, 2006 / Page 1

5 2. SFTF proposed to discharge to High Quality (HQ) or Exceptional Value (EV) Waters. A proposal for discharge of an SFTF to HQ or EV waters as defined in Title 25 Pa. Code Chapter 93 is not eligible for the National Pollutant Discharge Elimination System (NPDES) General Permit described in this manual. Proposals for systems similar to those listed in this manual must qualify for an individual NPDES permit. This permitting process has additional requirements and may result, in some cases, in the denial of permits, based on the quality of the receiving waters. Because of the complexities of this individual permitting process, the applicant should contact the appropriate regional office for more information and appropriate permitting procedures before making additional investments in the property based on the potential availability of an SFTF. Regional office locations and contacts are available on DEP s Web site. 3. Proposal for the use of an SFTF with a discharge to a dry stream channel in areas of hazardous geology or with discharge in areas with high nitrate-nitrogen. A proposal for the use of an SFTF with a discharge to a dry stream channel in areas of hazardous geology or existing background nitrate-nitrogen concentrations exceeding 5 mg/l requires, at a minimum, a preliminary hydrogeologic study to determine the potential impact of the SFTF discharge on water supplies in the estimated area of impacted groundwater. In either case, the proposal may be disapproved if adverse impacts are projected and supported by further evaluation. 4. Proposals not documenting compliance with operation and maintenance requirements. The systems listed in this manual require significant operation and maintenance. If the necessary maintenance is not provided, the system may fail and the property owner may be faced with significant costs to resolve problems. When proper operation and maintenance is provided, these systems should function for their design life. Any municipality proposing use of an SFTF must establish specific responsibilities for operation and maintenance of the proposed system during the Act 537 planning process as stated in Title 25 Pa. Code 71.64(c)(5). C. Advantage Of Using The Systems In This Manual The systems described in this manual may be eligible for coverage under an NPDES General Permit and Water Quality Management (WQM) General Permit. These general permits are published statewide one time and coverage is obtained under the statewide permit by documenting compliance with the provisions of this manual and a commitment to meet any conditions contained in the statewide permit. The design standards in this manual are based on accepted engineering practices and are meant to ensure that the resulting systems are adequate to protect the public and the environment. Proposals for / FINAL December 2, 2006 / Page 2

6 systems not described in this manual must apply for individual NPDES and WQM permits which involve a more complex siting, design and approval process. II. DESIGN REQUIREMENTS A. General 1. An SFTF must be capable of continuously producing a suitable effluent (< 10 mg/l BOD 5 and Total Suspended Solids (TSS)) without causing water pollution or public health hazards. The technology in this manual, if properly installed, operated and maintained, will meet this requirement. In addition, final disposal of treated effluent to a dry stream channel must meet the requirements of 25 Pa. Code 71.64(c)(2) and 71.64(c)(3) regarding hydrogeologic evaluations. This information should have been submitted as part of the planning module. 2. The design flow for an SFTF must be based on the following: a. An SFTF proposed to serve a single-family residence with three bedrooms or less must be designed based on a minimum flow of 400 gpd. The flow is increased by 100 gpd for each additional bedroom over three. These flow figures allow for the use of household garbage grinders, automatic washing machines, dishwashers and water softeners. b. SFTFs proposed to serve any other source of domestic sewage are designed based on the flows in Appendix A for the type of facility to be served. If available, actual flow data obtained by daily recordkeeping or metering for any establishment, indicating peak daily flows over a 1-year period, may be used in place of the estimated sewage flows listed in Appendix A. For nonresidential establishments, 200 gpd is the minimum volume used in calculating the size of the SFTF. 3. An SFTF consists of a treatment tank, filtration system, disinfection and outfall sewer. 4. All piping for an SFTF, except perforated underdrain piping in Sections II.F.1.e (1) and II.F.2.e. (1), must be marked NSF-Drain-Waste-Vent (DWV). Only domestic wastewater may be discharged to the SFTF, including kitchen and laundry wastes and water softener backwash. Roof gutters, sump pumps, foundation drainage, surface runoff and cooling water must not be discharged to the SFTF, nor may such discharges be permitted to flow over any underground treatment units. 5. A properly sized exterior grease trap is required where grease may be a problem. 6. Good water conservation practices are important in reducing the volume of wastewater requiring treatment, helping to ensure the availability of adequate water supplies in the future, and reducing energy costs. Examples of water / FINAL December 2, 2006 / Page 3

7 conservation fixtures includes but are not limited to 1.6-gallon flush toilets, faucet and shower flow restrictor and front-loading washing machines. 7. The SFTF must be accessible for inspection, sampling and maintenance. 8. Visual and audible alarms are required for mechanical equipment, such as aerobic treatment units and pumps, to alert the responsible individual in the event of a malfunction. These alarms, when electrically operated, must be connected to a separate circuit from the circuit serving the mechanical equipment or device. 9. The following minimum horizontal isolation distances must be maintained between all treatment or mechanical components of the SFTF and the features named. Where conditions warrant, greater isolation distances may be required. a. Property line, easement or right-of-way - 10 feet. b. Occupied buildings, swimming pools and driveways - 10 feet. c. Individual water supply or water supply system suction line - 50 feet. A water supply suction line must never pass under a building sewer. d. Water supply line under pressure - 10 feet (including building sewer). e. Streams, watercourses, lakes, ponds or other surface waters - 25 feet. The discharge pipe need not be isolated from the receiving waterbody. 10. An SFTF must not be placed where: a. The area is identified by the Federal Emergency Management Agency (FEMA) as a floodway. b. Completed flood mapping is not available, but the soil has been mapped or identified as floodplain soil or a flood-prone area. c. The area has been delineated as a wetland; however, a discharge to a wetland may be considered by DEP where no other options exist. 11. If the SFTF is located in an area identified as a flood fringe by FEMA, an encroachment permit may be required. B. Building Sewer 1. FUNCTION To convey the wastewater from the building to the SFTF / FINAL December 2, 2006 / Page 4

8 2. SPECIFICATIONS a. Building sewers must be constructed of a durable material acceptable to DEP (DWV or better) and as specified by local plumbing or building codes. b. When the average daily flow of sewage from an establishment is 1,000 gpd or less, all building sewers must be at least 3 inches in diameter (or larger if specified by local plumbing or building codes). When the average daily flow exceeds 1,000 gpd, all building sewers must be at least 6 inches in diameter (or larger if specified by local plumbing or building codes). c. Cleanouts must be placed at the junction of the building drain and building sewer. d. Cleanouts must be provided at intervals of less than or equal to 100 feet. e. House or building sewers should be installed with as straight an alignment as possible. Bends ahead of the SFTF are limited to 45 degrees or less where possible. If 90 degree bends cannot be avoided, they must be made with two 45-degree bends. Cleanouts must be provided at each change of direction in solids-carrying lines. f. The grade of the building sewer must be at least 1/8 inch per foot; however, the grade of the 10 feet of building sewer immediately preceding the SFTF must not exceed 1/4 inch per foot. g. All building sewers must be constructed with watertight joints, be strong enough to withstand the imposed loads, and be installed on material suitable to prevent damage from settling. h. The building sewer must be installed to allow continuous venting of any underground treatment tank through the main building stack, unless otherwise specified by local plumbing or building codes. i. Building sewers must be connected to treatment tanks using watertight mechanical seals or hydraulic grouting. Portland cement grouting is not permitted. C. Raw Sewage Pumping 1. FUNCTION To lift wastewater from the source to the SFTF. Pumping of raw sewage should be avoided if possible due to potential clogging, added maintenance and increased electrical usage / FINAL December 2, 2006 / Page 5

9 2. TYPE OF UNIT The pump used should be specifically designed for pumping of sewage. Grinder pumps may be necessary. 3. CAPACITY The pump must have a discharge rate, at design head conditions, of at least two times the estimated peak flow but not less than 5 gallons per minute. 4. ALARM FEATURE When a lift station is used, an alarm system (both audible and visual) must be provided that warns of a sewage level in excess of the maximum height in the wet well. The alarm system must be on a separate electrical circuit from the pump. 5. WET WELL The wet well must have a minimum storage capacity of 50 gallons, in order to accommodate normal peak flows and emergency storage during a short power outage. The pump must be able to be serviced without dewatering the wet well. 6. VALVES Check and shutoff valves must be used to isolate the pump from the wet well and force main. The check valve must be located between the shutoff valve and the pump. 7. LOCATION If the pump unit is installed outside the structure served, it must be accessible and protected from weather and vandalism. Inside installations must be quiet, free from electrical and health hazards, and must be certified by nationally-recognized independent testing laboratories, such as the Underwriter s Laboratories, Inc. (UL) and NSF International. 8. VENTILATION The wet well must be properly vented to the outside. Inside installations must be completely airtight and vented to avoid buildup of hazardous and odorous gases. The completed installation must be pressure tested prior to operation. 9. FORCE MAIN The force main piping associated with the pump unit(s) must have watertight joints, and meet or exceed DWV specifications / FINAL December 2, 2006 / Page 6

10 D. Treatment Tanks 1. Septic Tank(s) a. FUNCTION Septic tanks provide the initial treatment of sewage by removing settleable and floatable solids, and by anaerobic bacterial decomposition of the stored sludge. b. CAPACITY (1) The minimum liquid septic tank capacity for any installation shall be 1,000 gallons. (2) The septic tank capacity shall have a minimum hydraulic retention time of 2.5 days using estimated maximum daily sewage flows from Appendix A. (3) Where dual compartment septic tanks are used to attain required capacity, the tanks shall be connected in parallel. Two single compartment tanks shall be equivalent to a dual compartment tank. c. CONSTRUCTION (1) Tanks must be either two-compartment rectangular or rectangular tanks in series, watertight and constructed of a sound and durable material not subject to excessive corrosion or decay. (a) (b) (c) (d) Rectangular precast concrete tanks must have a minimum 2 1/2-inch wall thickness and be adequately reinforced. Precast slabs used as covers shall have a thickness of at least 3 inches and be adequately reinforced. Rectangular tanks having a liquid capacity of 5,000 gallons or less may not be constructed of blocks, bricks or similar masonry construction. Tanks having a capacity in excess of 5,000 gallons may be constructed onsite to meet the standards of the National Concrete Masonry Association for reinforcement and waterproofing. These standards are contained in Basement Manual, Design and Construction Using Concrete Masonry, TR 149. National Concrete Masonry / FINAL December 2, 2006 / Page 7

11 Association, 2001, Concrete Masonry Basement Wall Construction, TEK National Concrete Masonry Association, 2001 and Preventing Water Penetration in Below-Grade Concrete Masonry Walls, TEK 19-3A. National Concrete Masonry Association, (2) The depth of liquid in any tank or its compartments shall be: (a) (b) Greater than or equal to 2 1/2 feet but less than or equal to 5 feet for tanks having a liquid capacity of 600 gallons or less. Greater than or equal to 3 feet but less than or equal to 7 feet for tanks having a liquid capacity of more than 600 gallons. (3) No tank or compartment may have an inside horizontal dimension less than 36 inches. (4) Septic tank installations must consist of rectangular tanks with 2 compartments or 2 single compartment tanks in series. The first compartment or tank shall have at least the same capacity as the second but may not exceed twice the capacity of the second. Multiple tank sets connected for the purpose of achieving required hydraulic capacity shall only be permitted where the sets are connected in parallel. All tank sets shall have equal capacity and receive equal loading. d. INLET AND OUTLET CONNECTIONS (1) The bottom of the inlet shall be a minimum of 3 inches above the bottom of the outlet. (2) Inlet baffles or vented tees must extend below the liquid level at least 6 inches. Penetration of the inlet device may not exceed that of the outlet device. (3) The outlet baffles or vented tees of each tank or compartment shall extend below the liquid surface to a distance equal to 40 percent of the liquid depth. (4) The inlet and outlet baffles or vented tees shall extend above the liquid depth to about 1 inch from the top of the tank. Venting shall be provided between each compartment and each tank / FINAL December 2, 2006 / Page 8

12 (5) An effluent filter bearing the seal of NSF indicating testing and approval by that agency under Standard No. 46 shall be installed on the outlet of the final tank or compartment. e. TREATMENT TANK ACCESS (1) Each tank or tank compartment shall have an access manhole with an inside dimension of at least 20 inches square (20 x 20) or in diameter, with a removable cover. The top of the tank containing the manhole or the top of the manhole extension may not be more than 12 inches below grade level. If access is extended to grade, the access cover must be airtight. Grade level access covers shall be secured by bolts or locking mechanisms, or have sufficient weight to prevent unauthorized access. (2) The ground surface shall slope away from any access extended to grade level. (3) An access port directly above the filter is required so the filter can be removed for inspection and cleaning. f. INSPECTION PORT A maximum 4-inch diameter inspection port with a sealed cover shall be installed to grade level above the inlet tee. g. OPERATION AND MAINTENANCE An annual inspection of the system by the service provider is required. The septic tank(s) shall be pumped at least every 3 years. 2. Aerobic Treatment Tank a. FUNCTION Aerobic treatment tanks provide for aerobic biochemical stabilization of sewage by bacteria (reduction of BOD 5 and suspended solids) by mechanically introducing air into the sewage during the detention period provided in the aeration unit. b. CAPACITY Capacity shall comply with the following: (1) The rated treatment capacity of an aerobic treatment tank shall be specified by the manufacturer. The manufacturer s data shall be in / FINAL December 2, 2006 / Page 9

13 conformance with the approved test sequence and protocol in part (c), Testing and Approval, below. (2) The minimum manufacturer s rated treatment capacity of an aerobic treatment tank approved under this section is 400 gpd. (3) For single-family dwelling units not served by a community system, a minimum daily flow of 400 gpd is used to determine required aerobic treatment tank capacity. This figure is increased by 100 gpd for each additional bedroom over three. The daily flow provides for use of garbage grinders, automatic washing machines, dishwashers and water softeners. (4) For other than single-family dwellings, the rated treatment capacity must meet or exceed the estimated daily sewage flow as determined using Appendix A. c. TESTING AND APPROVAL (1) Aerobic treatment tanks shall bear the seal of the NSF International, indicating testing and approval by that agency under Standard No. 40. (2) Units tested and awarded a seal under a standard other than the current standard shall be approved for use until the expiration of the seal. Units initially submitted for testing or resubmitted for testing shall be approved under the version of NSF International Standard No. 40 in effect at that time. (3) Multiple aerobic treatment tanks connected for the purpose of achieving required hydraulic capacity must be connected in parallel. All tanks shall have equal capacity and receive equal loading. (4) Every aerobic sewage treatment tank shall be equipped with a visual and audible alarm system that is designed to respond to any electrical failure, mechanical failure, or malfunction of the tank or any component. d. OPERATION AND MAINTENANCE An annual inspection of the system and pumping of the tank by the service provider is required / FINAL December 2, 2006 / Page 10

14 E. Filter Distribution System 1. FUNCTION Distribution systems distribute the effluent from the septic or aerobic tank uniformly over the area of the filtration unit for further treatment. 2. DOSING TANKS a. Dosing tanks shall be constructed of materials to the specifications outlined in Section II.D.1.c(1). b. Dosing Volume The dosing tank shall be designed so that the estimated daily flow shall be discharged to the filter area in one or more doses. Minimum dose volume shall be five times the internal liquid capacity of the delivery pipe, manifold and laterals, or 100 gallons, whichever is greater. When a siphon is used in a pressure distribution system, the minimum dose volume shall be equal to the internal liquid capacity of the delivery line plus five times the internal liquid capacity of the manifold and laterals. c. The dosing tank shall have a minimum liquid capacity equal to or greater than two times the designed dose volume. d. Sufficient space shall be provided for electrical connections and proper pump control operation. e. Unless otherwise regulated by local electrical codes, all electrical connections shall be moisture resistant and at a point higher than the inlet pipe, or mounted above grade outside of the dosing tank or manhole extension within a tamper resistant, lockable control box. f. A watertight manhole, at least 20 inches square (20 X 20) or in diameter, extended to grade, shall be provided for access to the dosing tank. Manhole covers shall meet the specifications in Section II.D.1.e., Treatment Tank Access. 3. DOSING PUMPS AND SIPHONS a. The intake of the dosing pump shall be at least 6 inches from the bottom of the tank. b. Pumps shall not be suspended above the bottom of the tank by chains or similar equipment / FINAL December 2, 2006 / Page 11

15 c. A disconnect shall be incorporated into the piping within the dosing tank for ease of pump removal. This shall be located so that entering the tank to remove the pump is not necessary. A non-biodegradable rope may be provided to remove the dosing tank pump. d. An effective warning device shall be installed in the dosing tank to indicate failure of the pump or siphon. Warning devices requiring electricity shall be provided with a circuit separate from the pump circuit. e. A copy of the performance curve of the pump or discharge specifications for the siphon to be used shall be included in the design specifications attached to the permit application form. A copy of the manufacturer s specifications showing that the pump is designed to handle sewage or sewage effluent shall also be attached to the system design. f. Where an aeration tank or other batch-type treatment process is used which results in a periodic pump discharge from the treatment tank, the discharge mechanism may be substituted for a dosing tank and pump if the periodic discharge rate meets the criteria in Section II.E.3.l.(1). g. When an establishment produces more than 50 percent of its total daily flow during a peak flow period, the minimum dose volume shall equal the anticipated flow during that peak period. h. Check valves in the dosing tank or delivery pipe are not permitted. i. All delivery and manifold piping in pump systems shall be sloped to allow drainage back to the dosing tank. j. The low water level in the dosing tank shall be high enough to keep the pump suction submerged at all times. k. When a siphon is used, a ball valve and observation port shall be provided in the delivery line between the dosing tank and the manifold. Access to the observation port and ball valve shall be extended to grade, capped and secured to prevent unauthorized entry. l. Pump Capacity (1) The minimum pump capacity (gpm) shall meet the periodic discharge rate. The periodic discharge rate can be calculated by multiplying the total number of discharge holes contained in the laterals of a proposed distribution layout by the gpm factor determined by the hole size at the design head level / FINAL December 2, 2006 / Page 12

16 (2) Discharge rates from the individual holes of the lateral at design head shall be calculated using the sharp-edged discharge hole equation: gpm=11.99(d 2 ) h gpm=gallons per minute d=diameter of hole (inches) h=head to be maintained at terminal ends of lateral (in feet) (3) Total pump head shall be calculated by addition of all losses incurred due to elevation changes, pipe and fitting friction losses, and the head level to be maintained at the terminal end of the lateral of 3 feet. (4) Head loss due to friction in pipe and fittings used in construction of the pressure system shall be calculated using a friction loss table for smooth-walled plastic pipe (C=150). (5) When siphons are used in a pressure distribution system, each discharge hole shall be at least 5/16 inch in diameter. The discharge from all of the holes in the distribution system may not be less than the minimum rate of the siphon and may not vary from the average discharge rate of the siphon by more than 20 percent. (6) The minimum pump capacity shall equal the total discharge from all holes in the laterals when operating at designed head. 4. PRESSURE DOSE CRITERIA a. General Requirements: (1) The piping used in a pressurized system shall have watertight joints. (2) Delivery pipes from dosing pumps shall be installed to facilitate drainage of the distribution piping back to the dosing tank between doses. b. Design Standards: (1) Conveyance of effluent from the dosing tank to the filter area shall be through a delivery pipe sized to minimize friction loss. Check valves shall be prohibited on delivery pipes. Where the system designer determines that water hammer may be a problem, thrust blocks may be installed on delivery pipes / FINAL December 2, 2006 / Page 13

17 (2) Distribution to the individual laterals shall be by a central manifold extending into the filter area from the delivery pipe or header. The manifold shall have the following minimum diameters: Sq. ft. of Filter Area Minimum Manifold Diameter 200 to 1, /2" >1,199 2" (3) Laterals shall be extended from both sides of the manifold by opposing tees or a double sanitary tee. (4) Laterals shall consist of 1 1/2-inch minimum diameter pipe, with holes placed along the bottom of the pipe; an end cap shall be cemented on the terminal end of the lateral. Minimum hole size shall be 1/4-inch systems using pumps or 5/16 inch for systems using siphons. (5) The first hole in the lateral shall be 3 feet from the manifold. Additional holes shall be placed 6 feet on center with the last hole placed directly in the end cap. (6) Distribution laterals shall be placed from 4 to 6 feet on center and 2 to 5 feet from the side walls. (7) All systems shall be designed to maintain a minimum of 3 feet of head at the terminal end of each lateral. (8) The maximum length of a lateral designed under this subsection shall be 100 feet. (9) All piping and fittings in the system shall be sized to minimize friction losses to provide as uniform distribution of effluent as possible. (10) The head loss due to friction from the beginning of the distribution manifold to the terminal end of the last lateral may not exceed 15 percent of the head level to be maintained at the terminal end of the lateral. (11) Spacing of laterals and discharge holes in the laterals shall provide for uniform distribution of the effluent over the filter. (12) The permittee shall conduct a test pressurization of the completed distribution system in the presence of the design engineer prior to covering the piping system from view. During the test, the permittee shall confirm that all joints are watertight and that a discharge is occurring from each hole / FINAL December 2, 2006 / Page 14

18 c. Design of Pressure Distribution: (1) Variation in head in the laterals caused by differences in elevation or friction losses shall be compensated for by individual design of the laterals. (2) The effluent application rate per square foot of any two laterals served by a common dosing tank shall have a maximum design variation of 10 percent. (3) Equalization of loading may be accomplished by variation of discharge hole diameter between laterals, variation of spacing of discharge holes between laterals or another method approved by DEP. (4) The maximum spacing between discharge holes is 10 feet. 5. OPERATION AND MAINTENANCE F. Filtration System Annual inspections of the system and pumping of the dosing tank by the service provider are required. 1. Subsurface Sand Filter a. FUNCTION To further treat the effluent from the initial treatment unit (septic tank system or aerobic treatment unit) by filtration and biochemical treatment in the sand media. b. LOCATION (1) A subsurface sand filter must not be installed in areas where bedrock is encountered unless a concrete bottom and sides are used. Where the seasonal high water table rises above the bottom of the sand filter, a suitable liner and padding as described in Section II.F.1.f. must be used to prevent sewage exfiltration or groundwater infiltration. (2) A subsurface sand filter must not be constructed in unstabilized fill / FINAL December 2, 2006 / Page 15

19 c. SIZE The size of the sand filter shall be determined using an application rate of 1.50 square feet of filter area per gpd based on the design flow calculated in Section II.A.2. for a septic tank system. A 1/3 reduction in filter surface area may be applied when an aerobic treatment unit is used. d. MEDIA (1) Gravel (Coarse Aggregate) At least 2 inches of coarse aggregate must surround underdrains and distribution pipes. The coarse aggregate shall have the following characteristics: (a) (b) (c) (d) (e) The aggregate shall not contain more than 5 percent by weight clay lumps and friable particles. Testing shall be performed using ASTM C 142. The aggregate shall not contain more than 5 percent by weight material finer than 75 µm (No. 200 sieve). Testing shall be performed using ASTM C 117 or PMT No The aggregate shall not contain more than 15 percent by weight total deleterious material. Deleterious material is any material that will adversely affect the structural soundness or storage capacity of the aggregate including material finer than 75 µm, clay lumps and friable particles. Consistency with AASHTO No. 3, 467, 5 or 57 size and grading requirements. The aggregate may meet the characteristics of an individual category (3, 467, 5, or 57) or fall within the outer boundaries of sieve testing for each sieve size category. A 3-inch layer of pea gravel meeting size and grading characteristics of AASHTO No. 8 must be placed on top of the underdrain aggregate to help prevent migration of the sand into the aggregate. A layer of porous geotextile or equivalent material shall be placed on top of the distribution pipe aggregate to help prevent migration of soil into the aggregate. (2) Sand At least 24 inches of clean sand must be used. The sand shall be consistent with Bituminous Concrete Sand Type B #2 specifications as described in PADOT Pub. 408, Section / FINAL December 2, 2006 / Page 16

20 The sand shall not contain more than 15 percent by weight deleterious material as determined by AASHTO-104 or ASTM The sand must be washed prior to installation. (3) Cover Soil A 12-inch minimum depth of earth must cover the coarse aggregate in all installations. If the top of the aggregate is less than 12 inches from the undisturbed soil surface, the soil cover must extend at least 3 feet beyond the filter area on all sides. The soil over the sand filter must consist of soil suitable for the growth of vegetation, be seeded to control erosion, and must be graded so that surface water will run off. e. UNDERDRAIN PIPING (1) A 3-inch diameter or greater DWV or equivalent underdrain piping shall be laid on a grade of 3 to 6 inches per 100 feet sloped to the outfall pipe. (2) Underdrain piping shall be located between the distribution laterals to maximize movement of the effluent through the filter sand. (3) Underdrain piping holes shall be equal or greater in number and size to the distribution piping holes. (4) Underdrain piping shall have two rows of holes placed at approximately 45-degree angles from each other along the bottom half of the pipe. (5) The outfall pipe from the underdrain header shall have an anti-seep collar and bentonite clay plug, or a leakproof boot sealed to the subsurface sand filter liner in accordance with the manufacturer s instructions. f. FILTER BASE AND LINER The base of the filter shall be sloped to the underdrain pipe (1 percent maximum slope). An impervious liner of hyplon, high density polyethylene (HDPE), polyvinyl chloride (PVC) or polyethylene sheeting of 20 mil thickness or equal must be installed on a tamped earth base to prevent seepage to groundwater unless a concrete bottom and sides are used. A 2-inch layer of sand or a layer of 10-ounce porous geotextile material must be placed on each side of the liner to prevent punctures and tears. Seams must be made according to the liner manufacturer s specifications / FINAL December 2, 2006 / Page 17

21 g. OPERATION AND MAINTENANCE Annual inspections of the system by the service provider are required. 2. Recirculating Subsurface Sand Filter a. FUNCTION To provide further treatment of the effluent from the initial treatment unit (septic tank system or aerobic treatment unit) by filtration and advanced biochemical treatment in the media through recirculation of a portion of the discharge back to the sand filter. This allows for a reduced size subsurface sand filter. b. LOCATION c. SIZE (1) A recirculating subsurface sand filter (RSSF) must not be installed in areas where bedrock is found at a depth less than the proposed depth of the sand filter. However, an RSSF can be installed when the seasonal high groundwater table rises above the bottom of the sand filter if a suitable synthetic liner that will prevent sewage exfiltration or groundwater infiltration is included in the design. (2) An RSSF shall not be constructed in unstabilized fill. The RSSF shall be sized using 2.0 gpd per square foot of surface area based on the design flow calculated in Section II.A.2. for a septic tank system. A 1/3 reduction in filter surface area may be applied when an aerobic treatment unit is used. d. MEDIA (1) Coarse Aggregate At least 2 inches of coarse aggregate shall surround underdrains and distribution pipes. The coarse aggregate shall have the following characteristics: (a) The aggregate shall not contain more than 5 percent by weight clay lumps and friable particles. Testing shall be performed using ASTM C / FINAL December 2, 2006 / Page 18

22 (b) (c) (d) The aggregate shall not contain more than 5 percent by weight material finer than 75 µm (No. 200 sieve). Testing shall be performed using ASTM C 117 or PMT No The aggregate shall not contain more than 15 percent by weight total deleterious material. Deleterious material is any material that will adversely affect the structural soundness or storage capacity of the aggregate including material finer than 75 µm, clay lumps and friable particles. Consistency with AASHTO No. 3, 467, 5 or 57 size and grading requirements. The aggregate may meet the characteristics of an individual category (3, 467, 5, or 57) or fall within the outer boundaries of sieve testing for each sieve size category. (2) Sand (e) A 3-inch layer of pea gravel having AASHTO No. 8 characteristics must be placed on top of the underdrain aggregate to help prevent migration of the sand into the aggregate. A layer of porous geotextile or equivalent material shall be placed on top of the distribution pipe aggregate to help prevent migration of soil into the aggregate. At least 24 inches of clean sand must be used. The sand shall be consistent with Cement Concrete Sand Type A as described in PADOT specifications, Pub. 408, Section 703.1, or ASTM C-33 fine aggregate. The sand shall not contain more than 15 percent by weight deleterious material. (3) Cover Soil A minimum of 12 inches of cover soil material must cover the coarse aggregate in all installations. Ponding observation ports shall be installed to the top of the coarse aggregate through the cover material. Where the top of the aggregate is less than 12 inches from the original grade, the soil cover must extend at least 3 feet beyond the filter area on all sides. The soil over the sand filter must consist of soil suitable for growth of vegetation, be seeded to control erosion, and be graded so that surface water will run off / FINAL December 2, 2006 / Page 19

23 e. UNDERDRAIN PIPING (1) A 3-inch diameter or greater DWV or equivalent underdrain piping shall be laid on a grade of 3 to 6 inches per 100 feet, sloped to the outfall pipe. (2) Underdrain piping shall be placed between the distribution laterals to optimize effluent travel through the filter sand. (3) Underdrain piping holes shall be equal or greater in number and size to the distribution piping holes. (4) Underdrain piping shall have two rows of holes placed at approximately a 45-degree angle from each other along the bottom half of the pipe. (5) Underdrain piping shall have a cleanout extended to grade at a minimum of 1 foot from the sidewall and baffle. (6) The outfall pipes from the underdrain header shall have an antiseep collar and a bentonite clay plug or leak-proof boot sealed to the RSSF liner. f. FILTER BASE AND LINER The base of the filter shall be sloped to the underdrain pipe (1 percent maximum). An impervious liner of hyplon, HDPE, PVC or polyethylene sheeting of 20 mil thickness or equal must be installed on a tamped earth base to prevent seepage to the groundwater. A 2-inch layer of sand or a layer of 10-ounce porous geotextile material must be placed on each side of the liner to prevent punctures and tears. Seams must be made according to the liner manufacturer s specifications. g. RECIRCULATION The required effluent recirculation to outfall drain ratio is 3:1. This ratio can be achieved by one of the following methods or equivalent: (1) The underdrain is divided by an 8-inch high baffle placed under the liner and perpendicular to the long sidewall of the filter. Seventyfive percent of the effluent collected by the underdrain shall be recirculated back to the RSSF dose tank through a T-configured drain pipe and gravity discharge pipe. The remaining 25 percent of the effluent shall be collected by a drain pipe set parallel to the baffle with gravity discharge to the disinfection unit and outfall / FINAL December 2, 2006 / Page 20

24 (2) A typical flow splitter may be installed so that 75 percent of the effluent collected by the underdrain shall be recirculated back to the RSSF dose tank. The remaining 25 percent of the effluent shall be conveyed by gravity discharge to the disinfection unit and outfall. h. OPERATION AND MAINTENANCE Annual inspections of the system by the service provider are required. 3. CO-OP RFS III Recirculating Filter a. FUNCTION To provide further treatment of effluent following a two-compartment rectangular septic tank equipped with a 4-inch Biotube effluent filter or equivalent, or two rectangular septic tanks in series with each tank equipped with a 4-inch Biotube effluent filter or equivalent. b. LOCATION This filter should not be installed in locations where the filter would be subject to surface water flooding. c. ACCESS d. SIZE Access shall be provided by a minimum of two access openings. These access openings shall be a minimum of 24 inches by 36 inches and provide access to the entire surface of the filter. The effective surface area of the filter shall be sized to maintain a hydraulic loading rate no greater than 5 gpd per square foot. In no instance shall the effective surface area be less than 120 square feet with minimum sewage flow of greater than or equal to 200 gpd. d. MEDIA Filter media shall conform to wastewater treatment media requirements to be hard, durable and free of organic matter. Filter media shall be crushed boiler slag (Black Beauty product grade #1040) or manufacturer approved equal with the following physical properties: / FINAL December 2, 2006 / Page 21

25 Effective size 1.0 mm to 1.7 mm Uniformity coefficient less than 1.9 Particle shape angular Hardness 6 to 7 on Moh s scale Bulk density 75 to 100 lbs. per cubic foot Specific gravity 2.73 Moisture content less than 0.5 percent Free silica less than 1.0 percent A minimum of 24 inches of media is required. The bottom zone must consist of at least 16 inches of AASHTO #57 washed and crushed aggregrate, followed by 8 inches of AASHTO #8 washed and crushed aggregate. e. UNDERDRAIN PIPING The underdrain system shall consist of Infiltrator Systems, Inc. s, Equalizer 36 chambers or equivalent. The underdrain shall be positioned on either side of the spray grid. f. DISTRIBUTION/RECIRCULATION (400 to 600 gpd/unit in parallel) Grids per system, with flexibility to shut off 2 flow to any grid Orifices/spray grid 4 Total orifices 8 Laterals per spray grid 2 Length of laterals 10 ft. Orifice spacing 52 inch centers Orifice size 0.25 inch diameter Design flow per orifice 4.1 gpm Internal recirculation ratio 12:1 Cycles per day 72 Recirculation tank 1120 gal. Flushing orifice to underdrain with valve 1 per grid Freeboard (top of tank to sand) 1 ft. Submersible pump 33 gpm at required total design head The pump wet well shall contain a high water level alarm. The recirculation tank must be constructed to comply with the minimum requirements in Section II.E.2., Dosing Tanks. All tank pipe connectors shall be constructed of polyisoprene or natural rubber to ensure a flexible watertight seal. Any lids used shall comply with the following minimum requirements: STD 6/6-10/10 welded wire mesh, #3-A615 GR 40 steel rebar on 12-inch centers, Portland Type 1 cement, Pennsylvania Type A / FINAL December 2, 2006 / Page 22

26 concrete sand, #57 limestone gravel, or equivalent. Precast concrete shall have a minimum 28 days compressive strength of 4,000 pounds per square inch. g. OPERATION AND MAINTENANCE Annual inspections of the system by the service provider are required. 4. Accessible Sand Filter System a. FUNCTION b. SIZE To provide further treatment of the effluent from the initial treatment unit (septic tank system or aerobic treatment unit) by filtration and biochemical treatment. The size of the sand filter shall be determined using an application rate of 1.25 gpd per square feet of filter area based on the design flow calculated in Section II.A.2. c. FILTER The filter shall be constructed in a tank meeting the following specifications: (1) Tanks shall be watertight and made of a sound, durable material not subject to excessive corrosion or decay. (2) Concrete tanks shall have a minimum wall thickness of 2 1/2 inches and be adequately reinforced. (3) If precast slabs are used as tank tops to support the access covers, the slabs shall be at least 3 inches thick and be adequately reinforced. (4) Tanks shall be designed and constructed so that the depth from the cover to the top of the sand layer provides sufficient freeboard to allow for maintenance of the sand surface. (5) Access Access to the filter surface shall be provided by one of the following methods: / FINAL December 2, 2006 / Page 23

27 (a) Access openings Access shall be provided by one or more square or rectangular openings to allow maintenance of the entire surface area of the filter. The minimum dimension on any access opening shall be greater than 36 inches. For access openings with a dimension less than 60 inches, the inside of the tank wall shall be no greater than 18 inches from the edge of the opening in the direction of that dimension. For access openings with a dimension greater than or equal to 60 inches, the inside of the tank wall shall be no greater than 36 inches from the edge of the opening in the direction of the dimension. If more than one access opening is used, the distance between the openings shall be no greater than 36 inches. The access openings shall be extended a minimum of 6 inches above the final grade. Access covers shall prevent water infiltration and the entrance of debris, designed to facilitate routine maintenance, insulated and secured against unauthorized access. (b) Building The entire filter may be enclosed with a building or structure to allow access to the entire filter surface area. All exposed surfaces of the building must be insulated and the building must be secured against unauthorized access. Ventilation shall be provided for filter buildings. Switches for operation of ventilation equipment should be marked and conveniently located. Consideration should be given for the use of automatic controls. If automatic controls are used, a manual ventilation switch is required and shall override the automatic controls. The fan wheel should be fabricated from nonsparking material / FINAL December 2, 2006 / Page 24

28 d. MEDIA At least 24 inches of clean sand must be used. The sand shall be consistent with Bituminous Concrete Sand Type B #2 specifications as described in PADOT Pub. 408, Section The sand shall not contain more than 15 percent by weight deleterious material. The sand must be washed prior to installation. e. CONSTRUCTION The sand filter shall be constructed according to the following standards: (1) A 3-inch diameter or greater DWV or equivalent perforated underdrain pipe shall be placed on the bottom of the tank. (2) Underdrain piping shall be located between the distribution laterals to maximize movement of the effluent through the filter sand. (3) Two rows of perforations between 1/2 to 3/4 inch in diameter shall be drilled in the underdrain pipe at 6-inch intervals. The pipe shall be placed so the perforations face downward and the rows are at approximately 45-degree angles from each other. (4) All coarse aggregate shall meet the following specifications: (a) (b) (c) The aggregate shall not contain more than 5 percent by weight clay lumps and friable particles. Testing shall be performed using ASTM C 142. The aggregate shall not contain more than 5 percent by weight material finer than 75 µm (No. 200 sieve). Testing shall be performed using ASTM C 117 or PMT No The aggregate shall not contain more than 15 percent by weight total deleterious material. Deleterious material is any material that will adversely affect the structural soundness or storage capacity of the aggregate including material finer than 75 µm, clay lumps and friable particles. (5) Aggregate shall be placed around the underdrain to a total depth of 5 inches from the bottom of the tank. The uniform size and grading of the aggregate shall meet AASHTO No. 57 requirements. (6) A minimum of 4 inches of aggregate shall be placed over the aggregate underdrain material. The size and grading shall meet AASHTO No. 8 requirements / FINAL December 2, 2006 / Page 25