Colorado Onsite Wastewater Treatment Regulation Revisions

Transcription

1 DRAFT November 29, 2011 Colorado Onsite Wastewater Treatment Regulation Revisions Table of Contents 1. Purpose and Identification of the Regulation (Scope and Applicability) 2. Definitions 3. Administration 4. Site and Soil Evaluation 5. Wastewater Flow and Wastewater Strength 6. Minimum Distances Between Components of a System and Physical Features 7. Design Criteria - General 8. Design Criteria -Components 9. Design Criteria Soil Treatment Area 10. Design Criteria Higher Level Treatment 11. Design Criteria Other Facilities 12. Technology Review and Approval 13. Operation & Maintenance 14. Performance Appendix A Opt Ins/Opt Outs 15. Transfer of Title Inspection 16. Permitting and Oversight of Maintenance for Soil Treatment Area Reductions and Vertical Separation Distance Reductions and Horizontal Separation Distance Reductions based on Use of Higher Level Treatment 17. Use Permits Comments to Barbara Dallemand, barbara.dallemand@state.co.us By December 9,

2 Notes: Section 14. Performance has a number of tables that are appropriate to locate in other parts of the final regulations, but it is worthwhile to see them all together. For this draft, the tables have been located in both sections. Definitions have been temporarily moved to the end. We ask you to focus on the regulations first, and if you have time to review the definitions. Definitions will need re-editing after the final draft is complete. This is a rough draft. It is being sent out for your evaluation of content and clarity. Please ignore inconsistent formatting, but let us know about gross grammatical errors. 1. Purpose and Identification of the Regulation (Scope and Applicability) 2. Definitions Have been moved to the end. Will move back in the final draft. 2

3 3. Administration Site and Soil Evaluation 4.1. Site Evaluation Matrix? 4.2. Soil Evaluation Soils are classified using the United States Department of Agriculture (USDA) textural classifications and the Unified Soil Classification System (USCS) classes The soil groups are shown in Table Percolation Test Falling Head (1980 EPA DESIGN MANUAL) Number and location of Tests Commonly a minimum of three percolation tests are performed within the area proposed for an absorption system. They are spaced uniformly throughout the area. If soil conditions are highly variable, more tests may be required Preparation of Test Hole The diameter of each test hole is 6 in., dug or bored to the proposed depths at the absorption systems or to the most limiting soil horizon. To expose a natural soil surface, the sides of the hole are scratched with a sharp pointed instrument and the loose material is removed from the bottom of the test hole. Two inches of 1/2 to ¾ in. gravel are placed in the hole to protect the bottom from scouring action when the water is added Soaking Period The hole is carefully filled with at least 12 in. of clear water. This depth of water should be maintained for at least 4 hr and preferably overnight if clay soils are present. A funnel with an attached hose or similar device may be used to prevent water from washing down the sides of the hole. Automatic siphons or float valves may be employed to automatically maintain the water level during the soaking period. It is extremely important that the soil be allowed to soak for a sufficiently long period of time to allow the soil to swell if accurate results are to be obtained. In sandy soils with little or no clay, soaking is not necessary. If after filling the hole twice with 12 in. of water, the water seeps completely away in less than ten minutes, the test can proceed immediately Measurement of the Percolation Rate Except for sandy soils, percolation rate measurements are made 15 hr but no more than 30 hr after the soaking period began. Any soil that sloughed into the hole during the soaking period is removed and the water level is adjusted to 6 in. above the gravel (or 8 in. above the bottom of the hole). At no time during the test is the water level allowed to rise more than 6 in. above the gravel. Immediately after adjustment, the water level is measured from a fixed reference point to the nearest 1/16 in. at 30 minute intervals. The test is 3

4 continued until two successive water level drops do not vary by more than 1/16 in. At least three measurements are made. After each measurement, the water level is readjusted to the 6 in. level. The last water level drop is used to calculate the percolation rate. In sandy soils or soils in which the first 6 in. of water added after the soaking period seeps away in less than 30 min, water level measurements are made at 10 min intervals for a 1 hr period. The last water level drop is used to calculate the percolation rate Calculation of the Percolation Rate The percolation rate is calculated for each test hole by dividing the time interval used between measurements by the magnitude of the last water level drop. This calculation results in a percolation rate in terms of min/in. To determine the percolation rate for the area, the rates obtained from each hole are averaged. If tests in the area vary by more than 20 min/in., variations in soil type are indicated. Under these circumstances, percolation rates should not be averaged. Example: If the last measured drop in water level after 30 min is 5/8 in., the percolation rate = (30 min) / (5/8 in.) = 48 min/in. 4

5 5. Minimum Standards for the Calculation of Wastewater Flow and Wastewater Strength 5.1. For new facilities use Table 5.2 to estimate average daily wastewater flow and BOD5 strength Where gallons per day and pounds of biochemical oxygen demand (BOD5) per day can be obtained by measurement of existing conditions, such data may be used In no event will the system be designed for a lesser capacity than the anticipated maximum daily sewage flow or treatment requirements of the sewage or wastes in the system, whichever is larger BOD5 strength must be reduced to Treatment Level TL1 or lower before applying to a soil treatment area The local health official may require the installation of a meter to measure flow into the onsite wastewater treatment system Single Family Residential Homes Flow per person will be 75 gallons per day Local Health Departments have authority to increase the wastewater flow per person to 100 gallons/day For homes up to and including 3 bedrooms, the number of persons/bedroom shall be For homes with more than three bedrooms, the number of persons will be six persons (first three bedrooms x 2 persons/bedroom) plus one additional person for each bedroom in excess of three bedrooms The minimum design is for a 2 bedroom home Local Health Departments have authority to increase the number of persons per bedroom to 2 for all bedrooms For unfinished areas of residential dwelling units the local health officer may increase the number of bedrooms by as much as 2 bedrooms based on an assumption of 150 square feet per bedroom Reductions for water conservation devices: The local health official may allow reduction in design flow for proven and permanently installed water conservation devices. Reduction rates will be based on flow rate information supplied to the local health department for comparison with standard accepted rates for each fixture that utilizes water conservation devices Table 5.1 summarizes the design flows for single family residential homes up to 6 bedrooms. These design flow values do not require a peaking factor. Local Health Departments have authority to adjust these values as covered in Section

6 Table 5.1: Single Family Residential Design Flows # Bedrooms Occupancy (# of Persons) Wastewater Flow Per Person (gallons/day) Design Flow (gallons/day) Multi-Family and Commercial OWTS Design flow values for other systems are determined from Table 5.2 6

7 TABLE 5.2: ESTIMATE OF AVERAGE DAILY WASTEWATER FLOW AND BOD5 LOAD RESIDENTIAL WASTEWATER PER PERSON UNLESS OTHERWISE NOTED AVERAGE GALLONS PER DAY BOD5 IN POUNDS PER DAY Single-family dwellings OR Single-family dwellings by fixture type Bath/Shower Dishwasher Kitchen sink without garbage grinder Kitchen sink with garbage grinder Laundry washer Lavatory Water closet Total without kitchen sink garbage grinder Total with kitchen sink garbage grinder Hotels and Motels per room without private baths Hotels and Motels per room with private baths Multiple-family dwellings or apartments Boarding and Rooming houses Mobile Home Mobil Home Park per space COMMERCIAL WASTEWATER PER PERSON UNLESS OTHERWISE NOTED AVERAGE GALLONS PER DAY BOD5 IN POUNDS PER DAY Airports per passenger 5.02 Airport per employee Barber and Beauty Shops per chair * Bowling Alleys per lane - toilet wastes only 5.03* Bus Service Areas not including food 5.02 Country club per member County club per employee Dentist offices per non-wet chair 50.14* Doctors offices per doctor * Fairgrounds per person attending 5.02 Factories and plants exclusive of industrial wastewater per employee per 8-hour shift-no showers Factories and plants exclusive of industrial wastewater per employee per 8-hour shift - showers provided Kennels per dog Laundries, self-service per commercial washer Office Buildings per employee per 8-hour shift Stores and Shopping Centers per square foot of retail space.1.01* Service Stations per toilet fixture * Stadiums, Race Tracks, Ball Parks per seat 5.02 Theaters: Movie, Indoor, or Auditorium per seat

8 Work or construction camps semi-permanent with flush toilets Work or construction camps semi-permanent without flush toilets FOOR SERVICE ESTABLISHMENT WASTEWATER PER PERSON UNLESS OTHERWISE NOTED AVERAGE GALLONS PER DAY BOD5 IN POUNDS PER DAY Restaurant open 1 or 2 meals per seat 50.06/meal served 24-hour restaurant per seat 75.07/meal served Restaurant with paper service only per seat 25.01/meal served Additional for bars and cocktail lounges Drive-in restaurant per car space INSTITUTIONAL WASTEWATER WITHOUT KITCHENS PER PERSON UNLESS OTHERWISE NOTED AVERAGE GALLONS PER DAY BOD5 IN POUNDS PER DAY Churches 5.01 Hospitals per bed space Nursing Homes per bed space Schools, Boarding per person Schools, Day without cafeteria, gym or showers Schools, Day with cafeterias, no gym or showers Schools, Day with cafeterias, gym and showers Schools, Day additional for school workers RECREATIONAL AND SEASONAL WASTEWATER USE PER PERSON UNLESS OTHERWISE NOTED AVERAGE GALLONS PER DAY BOD5 IN POUNDS PER DAY Camps, day, no meals served Luxury resort Resort night and day Campground per campsite** Public park flush toilet per fixture per hour when park is open lbs./ fixture Public park urinal per fixture per hour when park is open lbs./fixture Public park shower per fixture per hour when park is open lbs./ fixture Public Park Faucet per fixture per hour when park is open lbs./ fixture Swimming pools and bathhouses Travel trailer parks with individual water and sewage hookup per unit ** Travel trailer park without individual water and sewage hookup per unit ** Formatted: Font: Calibri 8

9 6. 6. Minimum Distances Between Components of a System and Physical Features 6.1. Minimum, horizontal distances from the various components of a system to pertinent terrain features, including streams, lakes, water courses, springs, wetlands, wells, subsoil drains, cisterns, water lines, suction lines, gulches, dwellings, other occupied buildings and property lines, shall be in accordance with the following "Table of Minimum Horizontal Distances." The set back requirements are applicable for minimum system performance and treatment levels with modification allowed for higher performance or higher risk as suggested in Table 6.2. Acceptable methods of analyzing horizontal separation distances with higher treatment levels include: Researching the intended uses of impacted surface and / or ground waters not associated with drinking water supplies; Surveying adjacent property owners for potential conflicts with property line encroachments; Analyzing potential impacts that system locations may have on building foundations and other potentially affected features; Reductions in separation distances with higher level treatment must include provisions for operation and maintenance for the life of the system, as described in Appendix A Section 15. Permitting and Oversight of Maintenance for Soil Treatment Area Reductions and Vertical Separation Distance Reductions and Horizontal Separation Distance Reductions based on Use of Higher Level Treatment The minimum horizontal distance required from manmade cut banks and fill areas to on site wastewater treatment system components discharging effluent into or onto the surrounding soil shall be four (4) times the height of the cut bank or fill area. The distance set back shall be measured from the top of the cut bank or fill area to the nearest edge of the soil absorption component of the system, unless it can be demonstrated by a registered Professional Engineer or Geologist that a mechanical or natural barrier will prevent lateral effluent surfacing. (See diagram below). (replace with correct drawing) Wells, springs or potable water supply suction lines and all other constructed units listed in "Table 6.1" shall be installed or located in accordance with the minimum distance requirements provided in the table or such increased distances provided by the local board of health regulation Table 6.2 includes six of the required site evaluation, design, and treatment level 9

10 considerations necessary to properly evaluate the site and to design and locate the Soil Treatment Area (STA) component of an OWTS. Overall, the table recognizes that more highly treated effluent applied to the STA poses a lesser risk than less highly treated effluent Items 1, 2 & 3 in Table 6.2 address the allowable horizontal setback distance between the STA and a physical feature: Setback distance from well to STA Setback distance from STA to water features Setback distance from STA to a dry gulch Item 4 addresses the required vertical separation distance between the infiltrative surface of the STA and the restrictive layer or the required depth of soil comprising the STA Items 5a and 5b address the effluent density in gallons per day per acre. Higher effluent density results in greater nitrogen impacts to groundwater. For effluent density exceeding 1050 gallons per day per acre, the OWTS must remove nitrogen to treatment level 3N, prior to application to the STA The designer will select the level of treatment from Table 6.2 to be applied to the STA that is necessary in order to accommodate the site conditions. 10

11 Dispersal System Utilizing Aerosol Methods Seepage Pit or Slit Trench Absorption Trench, Seepage Bed, Sand Filter, Sub-surface Dispersal System, or Drywell Unlined Sand Filter in Soil With a Percolation Rate Slower than 60 Minutes per Inch Unlined or Partially Lined Evapotranspiration System, Wastewater Pond, or Surface Disposal System Other than Aerosol TABLE 6.1 MINIMUM HORIZONTAL DISTANCES IN FEET BETWEEN COMPONENTS OF A SEWAGE DISPOSAL SYSTEM INSTALLED AFTER NOVEMBER 15, 1973 AND PERTINENT PHYSICAL FEATURES Spring, Wells, Suction Lines (3) 100 (3) 100 (3) Potable Water Supply Line 100 (4)(2) 25 Potable Water Supply Cistern Dwelling Occupied Building Property Lines, Piped or Lined Irrigation Ditch 11 Subsoil Drains, Intermittent Irrigation Lateral (4)(2) (4)(2) (4)(2) Lake, Water Course, Irrigation Ditch Stream or Wetland (3) 25 (3) 50 (3) 50 Dry Gulches Septic Tank (3) (3) 25 6 (3) 25 6 (4)(2) Lined Sand Filter 60 (4)(2)

12 Lined Evapotranspiration 60 Field or Lined Wastewater Pond Pit Privy or Vault Privy 50 Septic Tanks, Treatment Plants, Dosing Tanks, Vaults Building Sewer or Effluent Lines (2) 50 (2)(4) (4)(2) (4)(2) (4)(2) (1) (4)(2) 10 (4) 25 0 (2)(4) (4) 10 (2)(4) 50 (2)(4) NOTE: The minimum distances shown above shall be maintained between the system components and the physical features described. Where soil, geological or other conditions warrant, greater distances may be required by the local board of health or by the Water Quality Control Commission pursuant to C.R.S in accordance with the authority prescribed by law and rules and regulations implemental of said section. Components which are not watertight should not extend into areas of the root system of nearby trees. For repair or upgrading of existing systems where the size of lot precludes adherence to these distances, repaired facility shall not be closer to set back components than the existing facilities. (1) Distance shown shall not apply to treatment plants or effluent lines where recycling is permitted. (2) Crossings or encroachments may be permitted at the points as noted above provided that the water conveyance pipe is encased for a minimum distance of ten (10) feet on each side of the crossing. A length of pipe shall be used with a minimum Schedule 40 rating of sufficient diameter to easily slide over and completely encase the water conveyance. Ridged end caps of at least Schedule 40 rating must be glued or secured in a watertight fashion to the ends of the encasement pipe. A hole of sufficient size to accommodate the pipe shall be drilled in the lowermost section of the ridged cap so that the conveyance pipe rests on the bottom of the encasement pipe. The area in which the pipe passes through the end caps shall be sealed with an approved underground sealant compatible with the piping used. (3) Add 8 feet additional distance each 100 gallons per day of design flow greater than 1000 gallons per day, unless it can be demonstrated by a registered Professional Engineer or Geologist that a mechanical or natural barrier or hydrologic analysis will prevent contamination. Flows greater than 2000 gallons per day must be hydrologically analyzed for flow, velocity, hydraulic head, and other pertinent

13 characteristics as means of estimating safe separation distances required to prevent contamination. (4) Encroachments may be permitted provided the water or wastewater conveyance pipe is encased as in (2) above, specified in the table. 13

14 TABLE 6.2: OWTS DESIGN CONSIDERATION AND TREATMENT REQUIREMENTS PRESSURE DOSING REQUIRED ITEM OWTS DESIGN CONSIDERATION Treatment Level 1 Treatment Level 2 Treatment Level 3 Treatment Level 3 with Nitrogen Reduction Horizontal Separation Distances 1 Distance from well to soil treatment area (STA) Greater than or equal to 100 feet Less than 100 feet and more than 75 feet Less than 100 feet and more than 75 feet Less than 75 feet and more than 50 feet 2 Distance from STA to pond, creek, lake, or other surface water feature Greater than or equal to 50 feet Less than 50 feet and more than 25 feet Less than 50 feet and more than 25 feet 3 Distance from STA to dry gulch Greater than or equal to 25 feet Less than 25 feet and more than 10 feet Less than 25 feet and more than 10 feet Vertical Separation Distances 4 Depth in feet from STA infiltrative surface to restrictive layer 4 feet 3 feet with pressure dosing Less than 3 feet and more than 2 feet Less than 3 feet and equal to or greater than 2 feet Effluent Density 14

15 5a Effluent density in gallons per day per acre (GPDPA) with onsite well Limited to One Single Family Residence Limited to One Single Family Residence 5b Effluent density in gallons per day per acre (GPDPA) with community water Less than or equal to 1050 GPDPA Greater than 1050 GPDPA Notes to Table6.2: 1. STA: Soil Treatment Area 2. GPDPA: Gallons per day per acre 3. Effluent Density Treatment Level Requirements: For repairs / replacement of existing systems in areas where OWTS nitrate pollution DOES NOT pose a public health or water quality threat to ground water or surface water, items 5A and 5B are not applicable. 15

16 7. Design Criteria General 7.1. Reliability: Onsite wastewater treatment systems shall be designed and constructed such that each component shall function, when installed and operated, in a manner not adversely affected by normal operating conditions including erosion, vibration, shock, climatic conditions, and usual household chemicals used. Each component shall be free of non-functional protrusions or sharp edges, or other hazards, which could cause injury to persons, animals, or properties. Design shall be such as to exclude flies and rodents and to prevent the creation of nuisances and public health hazards and shall provide for efficient operation and maintenance Pipe Standards: All wastewater lines used in onsite wastewater treatment systems shall be constructed of compatible pipe, bonding agent, and fittings. Where plastic pipe and fittings are used, the minimum wall thickness of the pipe shall conform to ASTM Standard D 3034, or equivalent. Perforated distribution pipe surrounded by rock within a soil absorption system shall have a minimum wall thickness conforming to ASTM Standard D Corrugated polyethlene pipe with smooth interior that meets ASTM F405 and AASHTO M252 specifications or equivalent may also be used. Certain applications will require Schedule 40 or pipe of equivalent strength. Tile, open-joint pipe, and cast iron pipe shall not be used in onsite wastewater treatment systems Plumbing Codes: Plumbing fixtures, greasetraps, building sewers, vents, sewer lines and other appurtenances shall be designed, operated and maintained so as to comply with the minimum requirements of the locally enforceable plumbing code. In absence of a local plumbing code these must comply with the minimum requirements of the most recently revised Colorado Plumbing Code (3 CCR 720-1) Electrical Equipment, if used: All electrical work, equipment, and material shall comply with the requirements of the currently applicable National Electrical Code. All electrical connections must use water tight connections and have conduits sealed to prevent sewage gases from entering junction boxes and control panels and to prevent corrosion. No plugs and electrical sockets will be installed inside treatment components Identification and Data Marking: A permanent type plate or other indelible marking so inscribed as to be easily read and visible for the purpose of inspection shall be provided on major components not constructed on the site where installed. Said inscription shall include the following: Name of manufacturer. Model or serial number designation. Maximum design capacity of the unit and the unit of measurement Structural Integrity: Tanks shall be so constructed and installed as to withstand the weight of burial and hydrostatic pressures when full and when empty. All metal surfaces shall be properly coated to prevent corrosion Watertight Requirement: Septic tanks, pump tanks, vaults, or other units, including risers shall not allow entry of precipitation or infiltration of groundwater or surface water and shall not 16

17 permit the release of wastewater or liquids through other than designed openings Tank Anchoring: In locations where groundwater may cause instability problems to the septic tank, pump tank, vault, or other tanks in the onsite wastewater treatment system due to flotation, the tank shall be anchored in a sufficient manner in order to provide stability when the tank is empty. The design of the anchoring system will be prepared by a Registered Professional Engineer Accessibility for Inspection, Maintenance, and Serviceability: Each treatment component opening shall be equipped with access manholes with risers if more than 8 inches below ground surface, located to permit periodic physical inspection, collection and testing of samples and maintenance of all components and compartments. Components shall include but not be limited to submerged bearings, moving parts, pumps, siphons, valves, tubes, intakes, slots, filters, inlet and outlet baffles, and other devices. Components shall also be designed and constructed so that, when installed, they shall be easily capable of being maintained, sampled, and serviced according to the manufacturer s recommendations. Physical access to treatment components by maintenance personnel and equipment shall also be provided Indicators of Failure for Systems Utilizing Mechanical Apparatus: A signal device shall be installed which will provide a recognizable indication or warning to the user that the system or component is not operating or is operating but malfunctioning. This indication or warning shall be in the form of a visual or audible signal, or both. A signal or message may also be sent remotely to a maintenance provider Sampling Access: Where a required final effluent sample cannot be easily obtained, a sampling well shall be constructed. The sampling well shall be accessible, located in an area down gradient from the final effluent disposal area, and be provided with a properly secured cover at or above the ground s surface where located Instructions: The manufacturer of treatment units utilizing mechanical components shall provide clear, concise instructions covering the components which, when followed, will assure proper installation and safe and satisfactory operation and maintenance Surface Activity: The surface of the ground over the onsite wastewater treatment system or any part thereof, must be restricted to activity or use which will allow the system to function as designed and which will not contribute to compaction of the soil nor to structural loading detrimental to the capability of the component to function as designed. During construction, equipment will be kept off of the ground surface above the absorption field and out of the excavation to prevent compaction. If compaction occurs, the disturbed or compacted soil will be re-evaluated and new percolation tests will be performed to the disturbed or compacted soil and the system redesigned if the parameters have changed Distribution Box: A distribution box, if used, shall be of sufficient size to equally distribute effluent to the lateral lines and shall be constructed with the inlet invert at least one (1) inch above the level of the outlet inverts. Flow equalizers or similar devices will be installed on each outlet. Access to the distribution box will be such that the flow equalizers can be adjusted to maintain even flow between lines. 17

18 7.15. Sewage Pumping System Where Applicable: Non-clog pump opening shall have at least 2-inch diameter solids handling capacity where raw sewage is pumped or not more than 1/2-inch diameter solids handling capacity if previously settled effluent is pumped Automatic liquid level controls shall be provided to start and shut off pumps at a frequency required by the design Pressure pipe shall be of sufficient strength to accommodate pump discharge pressure and the pipe shall be sized to maintain a velocity of 2 or more feet per second Automatic air release valves shall be installed at high points in the pressure line where necessary to prevent air locking A pump shall be installed in a separate pump tank following the septic tank and be of sufficient volume to allow pump cycling commensurate with the pump design capacity. The second compartment of the septic tank shall not be used as the pump tank unless it can be shown that the minimum 48-hour detention time will not be decreased and the pump is screened or provided with an approved filtering device to assure that only liquid effluent will be discharged. The use of a 3 compartment septic tank, sized to accommodate the pump in the 3 rd compartment, is also acceptable The discharge line from the pumping chamber shall be protected from freezing by burying the pipe below frost level or sloping the pipe to allow it to be self-draining. Drainage shall be provided through the bottom of the pump or through a weep hole located in the discharge line prior to exiting the tank Pump tanks shall be installed so as to be accessible for servicing and maintenance. The discharge line inside the pump tank shall be connected to the line exiting the tank with a quick disconnect coupler so as to provide easy removal of the pump for servicing or replacement Grinder pumps are not allowed to be installed before septic tanks Floodplains: No new or expanded system shall be installed in a floodway. For any system repair that may affect the floodway delineation, appropriate procedures will be followed including revision of the floodway designation, if necessary. When a system is installed in a 100-year floodplain then the new or repaired system shall meet or exceed the requirements of the National Emergency Management Agency. The system as approved by the local Health Officer or his/her designated agent shall be designed to minimize or eliminate infiltration of floodwaters into the system, and discharge of the system into the floodwaters. 18

19 8. Design Criteria - Components 8.1. Septic Tanks: Sizing Requirements: Sizing for residential capacity shall be based upon the number of bedrooms according to the following table: SEPTIC TANK SIZE BASED UPON NUMBER OF BEDROOMS Minimum Effective Liquid Number of Bedrooms Tank Capacity (gallons) 2 or Each Additional For non-residential applications, a septic tank shall be sized to permit detention of incoming wastewater design flows for a minimum of 48 hours Septic tank design and dimension criteria: Except for systems that remove blackwater for separate treatment, the effective liquid capacity shall be no less than 1000 gallons Inlet invert shall be at least 3 inches higher than the outlet invert Outlet tee or baffle shall extend above the surface of the liquid to within one inch??? of the underside of the tank top and shall extend at least 14 inches below the outlet invert The distance from the outlet invert to the underside of the tank top shall be at least 10 inches Liquid depth shall be a minimum of 30 inches and the maximum depth shall not exceed the tank length or 60 inches, whichever is less A septic tank shall have two or more compartments or more than one tank may be used in series to provide the following capacity arrangement. The first compartment of a septic tank shall hold no less than 1/2 of the required effective capacity The transfer of liquid from the first compartment to the second or successive compartment shall be made at a liquid depth of at least 14 inches below the outlet invert, but not in the sludge zone At least one access manhole no less than 20 inches across shall be provided in each compartment of a tank The opening cover of a septic tank manhole, inspection port, or sampling access port shall be no deeper than 8 inches below the finished grade and made of materials resistant to degradation from moisture or sewer gases There shall be no less than 25 square feet of liquid surface area provided and at least six (6) feet between the inlet and outlet. 19

20 Pipe meeting or exceeding ASTM Standard D 3034 properly supported to prevent failure by settling shall extend from the septic tank for a distance of at least five (5) feet from the inlet and outlet ends Septic tank structural design criteria: Recommend that this section be moved to APPENDIX and Tanks will be watertight components constructed in accordance with accepted concrete, fiberglass or??? standards. Recognized standards include: A.C.I,??? The components must be designed, stamped, and approved by a structural engineer and include installation specifications Watertight Requirements: Septic tanks, vaults, pump tanks, or other treatment components shall not allow infiltration of groundwater or surface water and shall not allow the release of wastewater of liquids through other than designed openings. Tank slab lids shall be sealed with a water tightening agent. Each unit shall be inspected for indicators which may compromise its watertightness capabilities. The inspection shall be conducted by the Local Health Department and be performed after the tank installation but before backfilling. At the discretion of the inspector, the tank may be required to be tested for water tightness by the tank manufacturer or the system contractor. Acceptable testing methods include water filling the tank or vacuum testing Fiberglass, Fiberglass Reinforced polyester, and Polyethylene Tanks All tanks shall be sold and delivered by the manufacturer completely assembled Tanks shall be structurally sound and support external forces as specified above when empty and internal forces when full. Tanks shall not deform or creep resulting in deflection more than 5 percent in shape as a result of loads imposed Risers Each access hole or sampling port or inspection port must have a riser to the surface. Tank inlet and outlet lids may be buried within 8 inches of the surface without a riser requirement Each riser lid brought to the surface will have a secure closing mechanism such as a lock, special headed bolts or weight so as to prevent unauthorized access Identification and Data Marking: A permanent type plate or other indelible marking as to be easily read and visible for the purpose of inspection shall be provided on all tanks not constructed on the site where installed. The inscription shall include the following: Name of manufacturer Model or serial number designation Maximum design capacity of the tank and unit of measure In addition, the outlet of the tank shall be indelibly marked Effluent Filters An effluent filter will be installed in the outlet of the final compartment of each septic tank for new and repair installations If a pump is used to remove septic tank effluent from the final compartment of the septic tank, an effluent filter or equivalent must be provided prior to the pump The effluent filter will be cleaned at manufacturer-recommended intervals, or more often if use patterns indicate Effluent filters must comply with ASTM and NSF Standards or equivalent and 20

21 include installation and Operation and Maintenance specifications Grease Interceptors and Grease Traps A component designed to intercept, trap, and remove grease and oil from wastewater prior to it entering a septic tank shall be required for all commercial or licensed establishments that prepare or serve food to the public and that discharge into an onsite wastewater treatment system Grease interceptor units shall be properly sized, installed, and maintained per the criteria of the current Colorado Plumbing Code (3 CCR 720-1) or other locally adopted code in the applicable jurisdiction Grease interceptors shall treat only those portions of the total wastewater flow from which grease and oils are generated. 21

22 9. DESIGN CRITERIA Soil Treatment Area 9.1. For a system treating and disposing effluent through a soil absorption area, the method for calculating the minimum soil treatment area shall be based upon the capacity of the soil to absorb liquids as established by the subsurface evaluation and upon design criteria and construction standards for such type of absorption system as set forth in these regulations Unless designed by a registered professional engineer and approved by the local board of health (approval may be given by the local health department if authorized by regulations of the local board of health for such systems treating exclusively domestic wastes), no such system may be permitted in areas exhibiting any of the following conditions: Areas where the Soil Classes are determined to be in the following categories, as defined in Section? of these Regulations: Class U, Class IV, Class BR-1, and BR Where the maximum seasonal level of the groundwater table is less than four feet below the bottom of the proposed absorption system Where bedrock exists less than four feet below the bottom of the proposed absorption system Where the ground slope is in excess of thirty percent Soil building or replacement will be permitted to bring the soil within the requirements of suitable soil. Added soil shall pass XX sieve test, be classified as XX soil taxonomy, or not be certain soil taxonomy classification. Sand meeting ASTM C-33 is preferable. All added soil shall be completely settled prior to installation of components Lots platted after must have adequate area for a replacement soil treatment area Soil Treatment Areas The required area for an STA is determined by the following formula: Soil Treatment Area Required = Design Flow (in gallons/day) Adjusted LTAR (in gallons per day per square foot) 22

23 Table 9.1: Soil Treatment Area Long Term Acceptance Rates by Soil Texture, Soil Structure, Percolation Rate and Treatment Level Soil Type a 4b Soil Texture gravel coarse sand medium sand fine sand loamy sand sandy loam loam loam silt loam loam silt loam silt clay loam clay loam clay Soil Structure 85% rock fragments strong granular structure strong structure moderate structure excluding platy structure massive, no structure Unified Soil Classification Symbol & Soil Properties GP SP SW SM SC SM SC-CL CL LL <50, PI<20 CH LL > 50, PI > 20 *Note: Treatment Levels are defined in Section 10. Percolation Rate (MPI) Treatment Level 1* Gallons per day per square foot Treatment Level 2* Treatment Level 3* Treatment Level 3N* < 5 N/A to to to The soil types and LTAR s are only for absorption systems and are not applicable for use in systems that rely upon evapotranspiration Allowable Soil Treatment Area Reductions and Increases: The adjustment factors in Table 5 are only applicable for TL1 (septic tank effluent) The adjustment factors recognize more or less effective types of treatment areas, effluent application, and storage/distribution media by either increasing or decreasing the LTAR For the purpose of the table a baseline system (i.e. adjustment factor of 1.00) is considered to be effluent applied by gravity to a gravel filled trench The effective area of a trench is only the bottom area-no sidewall credit is allowed Adjustment factors less than 1.00 will increase the size of the STA, while adjustment factors greater than 1.00 will increase the size of the STA. 23

24 Table 9.2: Long Term Acceptance Rate (LTAR) Adjustment Factors for Soil Treatment Areas Accepting Treatment Level 1 Effluent Type of Soil Treatment Unit Method of Effluent Application from Treatment Unit Preceding Soil Treatment Unit Gravity Dosed (Siphon or Pump) Demand Pressure Dosed (Siphon or Pump) Timed Pressure Dosed (Pump Only) Type of Storage/Distribution Media Placed on Soil Treatment Unit Rock or Tire Chips Manufactured Media Chambers Bed Trench No Provision for Multiple STA s and Manually Alternated Flow Sand Filter* Not Allowed Not Allowed

25 The maximum reduction from all combined alternatives shall be no greater than 50% of the standard required soil absorption area Reductions for the added treatment categories listed shall only apply provided the system is inspected and certified annually per the requirements of Appendix A - Section 15. Permitting and Oversight of Maintenance for Soil Treatment Area Reductions and Vertical Separation Distance Reductions and Horizontal Separation Distance Reductions based on Use of Higher Level Treatment of these regulations 9.7. The ground surface shall be graded to deflect precipitation or other outside water from the soil treatment area. The area shall be protected against erosion. Subsurface drains upslope of the soil treatment area may be installed to divert subsurface flow around the area Alternating Systems: For two alternating soil absorption areas: A diversion valve or other approved diversion mechanism may be installed on the septic tank effluent line allowing alternating soil absorption systems. Each soil absorption system shall be a minimum of fifty (50%) percent of the total area required excluding the reductions given for dosing and gravelless systems. The diversion mechanism shall be readily accessible from the finished grade and shall be switched on an annual basis. Reductions in soil treatment area are not applicable to alternating systems For more than 2 alternating soil absorption areas with more frequent rotation between soil absorption areas: The number of soil absorption areas will be determined and the total area will be divided into that number of equal soil absorption areas, i.e. each of 3 systems will have 33 1/3 % of the total area. An automatic distribution valve will be used. Dosing of each system will be evaluated based on daily flow rates and the resultant proportionate flows required Dosing: Dosing may be used in conjunction with soil treatment areas. The dosing frequency may be calculated according to the following table: Table 9.3 Suggested dosing Frequencies for Various Soil Textures Soil Texture Dosing Frequency Sand 4 doses / day Sandy Loam 1 dose / day Loam Frequency not critical* Silty Loam 1 dose / day* Silty Clay Loam 1 dose / day* Clay Frequency not critical* *Long term resting provided by alternating fields is desirable and recommended in these soils Trenches 25

26 Trenches shall be 3 feet wide or less. The number and length of trenches will be sufficient to provide the required absorption area The bottom of the trench and distribution lines shall be level The bottom of the trenches will be no deeper than 4 feet unless adequate treatment at a deeper level can be demonstrated and approved by the Local Health Officer Perforated distribution pipe which shall be required for an absorption trench shall be placed the entire length of the trench and shall be surrounded by clean graded gravel, rock or material of equal efficiency which may range in size from 1/2 inch to 2 1/2 inches and shall be placed from at least 2 inches above the top of the distribution pipe to at least 6 inches below the bottom of the distribution pipe The separating distance between trenches shall be a minimum of six (6) feet sidewall-tosidewall. Pipe for gravity distribution shall be no less than 3 inches in diameter and preferably less than 100 feet in length. The terminal ends of lines shall be capped unless looped or air vented. The top of the placed gravel or such material used shall be covered with permeable geotextile meeting Standard or similar pervious material. An impervious covering shall not be used. Tile or open joint pipe shall not be used. A final cover of soil suitable for vegetation at least 10 inches deep shall be placed from the top of the geotextile or similar pervious material to the finished surface grade of an absorption trench. The final cover shall be graded to deflect runoff water away from the disposal area Machine tamping, rolling or hydraulic compaction of final cover shall not be permitted, however, hand tamping may be allowed where necessary to stabilize the soil to prevent erosion or the intrusion of extraneous water If dosing is used in conjunction with an absorption trench system, the dosing chamber shall be sized to account for the volume of the distribution and the dosing frequency Absorption Beds The bottom of the absorption bed and distribution lines shall be level The bottom of the absorption bed will be no deeper than 4 feet unless adequate treatment at a deeper level can be demonstrated and approved by the Local Health Officer Perforated distribution pipe which shall be required for an absorption bed be placed the entire length of the bed and shall be surrounded by clean graded gravel, rock or material of equal efficiency which may range in size from 1/2 inch to 2 1/2 inches and shall be placed from at least 2 inches above the top of the distribution pipe to at least 6 inches below the bottom of the distribution pipe The separating distance between parallel distribution lines in a absorption bed shall not exceed 6 feet and a distribution line shall be located within 3 feet of each sidewall of the absorption bed Pipe for gravity distribution shall be no less than 3 inches in diameter and preferably less 26

27 than 100 feet in length. The terminal ends of lines shall be capped unless looped or air vented. The top of the placed gravel or such material used shall be covered with permeable geotextile meeting Standard or similar pervious material. An impervious covering shall not be used. Tile or open joint pipe shall not be used. A final cover of soil suitable for vegetation at least 10 inches deep shall be placed from the top of the geotextile or similar pervious material to the finished surface grade of an absorption trench or seepage bed. The final cover shall be graded to deflect runoff water away from the disposal area Machine tamping, rolling or hydraulic compaction of final cover shall not be permitted, however, hand tamping may be allowed where necessary to stabilize the soil to prevent erosion or the intrusion of extraneous water If dosing is used in conjunction with an absorption bed system, the dosing chamber shall be sized to account for the volume of the distribution and the dosing frequency Seepage Pits, Dry Wells, and Cesspools: The construction of new seepage pits, dry wells, and cesspools for the treatment and disposal of onsite wastewater is prohibited, effective from the approval date of the Regulation Revision. Repairs to an existing seepage pit or dry well may be considered, provided the effluent discharged to these facilities is pre-treated to a Class 2 Level, as defined in these Regulations. [Note that construction of new cesspools has been banned since the initial ISDS regulations.] [Alternative1: Seepage pits and dry wells may be used for OWTS repairs, if space for other alternatives is not available. Seepage pits or dry wells may not be constructed on new sites. ] [Alternative 2: Seepage pits and dry wells may be used for OWTS repairs, if space for other alternatives is not available. Higher level treatment of at least TL2 must be used. Seepage pits and dry wells may not be constructed on new sites. ] [Alternative 3: If space for other alternatives is not available, seepage pits or dry wells may be constructed on repair or new sites if treatment level TL3N effluent is used.] Use of dry wells for the disposal of water not associated with an OWTS is not covered by these regulations Distribution Distribution between lines in an absorption system should be as even as possible. Provisions to adjust distribution following construction to allow for uneven settling of the system should be made On sites with slopes greater than 3%, the absorption field or trenches shall follow approximately the ground surface contours so variations in absorption depth will be minimized Serial Distribution: A serial distribution system may be used in all situations where a soil absorption system is permitted and shall be used where the ground slope does not allow for suitable installation of a single level absorption field, unless a distribution box or dosing chamber is used. The horizontal distance from the side of the absorption system to the surface of the ground shall be adequate to prevent lateral flow and surfacing of effluent above ground. Adjacent absorption fields or trenches shall be connected with a relief line or a drop box arrangement such that each trench fills with effluent to the top of the gravel before flowing to succeeding absorption areas. 27

28 10. Design Criteria Higher Level Treatment Table 2 below includes four levels of treatment that can be achieved by various OWTS components, excluding the Soil Treatment Area. TABLE 10.1: TREATMENT LEVELS Treatment Level CBOD5 (mg/l) TSS (mg/l) Total Nitrogen (mg/l) TL 1* TL TL TL 3N mg/l *Typical residential septic tank effluent prior to soil treatment Systems qualifying for the above treatment levels need to be approved under Section 12 of this Regulation From Performance Matrix: Suspended or Fixed Growth Aerobic Unit; Recirculating Sand Filter, Textile or Peat Filter, other to be determined by future advances To achieve treatment levels of effluent as described in the Performance Section or in other sections, treatment components shall be approved by the OWTS Technology Product Approval process (see Section 12), and adequate maintenance service for each shall be performed and documented Aerobic and Mechanical Sewage Treatment Systems General Design: The shape and design of an aeration compartment, its inlet and outlet arrangements, baffling and air application shall: Allow for intimate mixing of applied sewage, return solids, and applied air Prevent excessive short-circuiting of flow Prevent the deposition and buildup of solids in the aeration compartment Method of Aeration: The method of aeration shall be accomplished by mechanical aeration, diffused air, or a combination of these. The method of aeration shall at all times maintain aerobic conditions at the maximum organic loading in both the aeration and settling compartments Onsite wastewater treatment systems utilizing mechanical apparatus and furnished for installation in Colorado shall comply with the minimum requirements of criteria and construction standards set forth in these Regulations No unit utilizing mechanical apparatus and which is designed for surface or sub surface discharge or which may adversely affect state waters shall be permitted unless the following are adhered to: The system is installed within a geographic area wherein a public, quasipublic, or private entity is continually responsible for the operation and maintenance of the unit The operator of the system insures an efficient operation of all mechanical and electrical components prior to and during continued use of the system. 28