Design Standards for Effluent Disposal Systems

El Paso City Code tit. 18, ch. 18.21, art. VI

in effect

El Paso City Code § 18.21.220 Site evaluation.

18.21.220 - Site evaluation. The effluent discharge from a septic tank or aerobic plant requires further handling to render it safe from a public health standpoint. A well-designed subsurface soil absorption system will allow these liquids to seep into the ground without creating a health hazard or nuisance. After the prospective builder has selected a suitable area and is assured that safe distances from wells, lakes, etc. can be maintained, the builder must determine, with the assistance of an experienced soils scientist, registered professional engineer or registered professional sanitarian whether soil formations in the selected area will allow a soil absorption system to work. When conventional soil absorption systems are used, there shall be no interference from groundwater. The groundwater table must be situated at least four feet below the bottom of the soil absorption system. The design standards for conventional soil absorption systems set forth in this chapter are based on the premise that impervious strata are at depths greater than four feet below the bottom of the absorption trench. Conventional soil absorption systems shall not be used if either impervious strata or groundwater exists at depths less than four feet from the trench or bed bottom, unless a detailed site evaluation is made and a design by a registered professional engineer or registered professional sanitarian is accepted by the licensing authority. (Ord. 9448 (part), 1988)

El Paso City Code § 18.21.230 Soil absorption trench.

18.21.230 - Soil absorption trench. A soil absorption trench may be used if the proposed site provides sufficient room and is of suitable soil. An experienced soils scientist, registered professional engineer, or registered professional sanitarian should be consulted to determine if the site qualifies for trenches. A. Absorption Trench Field for Level Terrain. Where the topography or ground slope is not too steep, a flat or level system of gravel-filled trenches or percolation beds is recommended. The use of a looped trench system will avoid dead ends and assure maximum effective utilization of all portions of the system. No individual trench shall exceed seventy-five feet in length. 1. The field bottom must be at least twelve inches lower than the flowline of the treatment tank. The capacity of any particular absorption system is determined by the total area of trench or bed bottom built into the system. The amount of this required minimum area will depend upon the expected sewage load, the average soil percolation rate, and the site's soil evaluation results. The soil percolation rate may be determined by performing a percolation test as described in Section 18.21.110 of this chapter. The trench dimensions for single family residential units may then be estimated from Table 18.21.230. For sewage flows of less than five thousand gallons per day from commercial or institutional establishments, A, the absorption trench bottom required, is determined by formula A=1.25 Q/Ra, where Ra, the allowable application rate, is found in Table 18.21.230 and Q is the daily flow. 2. All parts of the trench or bed bottom shall be at the same elevation. Trenches should be constructed as shallow as possible with a minimum depth of eighteen inches and a maximum depth of thirty-six inches. Deeper trenches should be used where snow may saturate the upper portion of the trench. For trench depths greater than twenty-four inches (except where snow exists), sand shall be used to fill the trench up to the top soil over as shown in Figure 18.21.230(A). The trench width shall not exceed thirty-six inches, as narrow trenches (twelve to eighteen inches) are recommended. Although trench length is based on bottom area only, sidewall area is important since much of the wastewater is absorbed through the sidewalls and is eventually evaportranspirated. Maximum allowable spacing between adjacent edges of parallel trenches is three trench widths. 3. Liquid from the sewerage unit is conducted to the absorption system via a watertight line similar to the house sewer. The liquid is distributed uniformly through the gravel-filled trenches by the use of three-inch to ten-inch perforated plastic pipe of any one size, or equivalent pipe materials. It is important that the distribution piping be laid reasonably level (four inches per one hundred feet maximum allowable grade) in the trenches, with a minimum of six inches gravel depth under the pipe. A total gravel depth of approximately twelve inches is required. The trench media must be clean graded gravel, broken vitrified brick, washed rock, crushed stone, or similar aggregate that is generally one uniform size (from 0.75 inches to 2.0 inches). Oyster shell, other types of shell, and soft limestone are not allowed for trench media because the cementitious properties of this type of material often result in early trench failure. The distribution pipe shall consist of plastic perforated pipe, four-inch corrugated polyethylene, or equivalent materials with an SDR ratio (ratio of pipe diameter to wall thickness) not numerically greater than forty-one. Jointed tile is not recommended for use because of the difficulty in maintaining joint spacing and keeping the line level. Covering of several layers of newspapers, a layer of butcher paper, or geotextile filter fabric material over the top of the gravel is required to prevent the sandy loam or sand backfill from invading the gravel until the backfill becomes stabilized. When only sandy loam is placed over gravel, only geotextile filter fabric shall be allowed. Tar paper or other impervious material shall not be used under any circumstance. The pipe selected for drainfield construction shall have sufficient strength to resist crushing from external loadings such as earth fill, garden tractors, riding mowers, and similar yard equipment. Bituminous fiberboard or paper pipe shall not be used anywhere in the sewerage system. Poor construction practices will cause serious damage to the soil absorption system. Prior to issuance of a permit, notice shall be given to the licensing authority of the types of piping proposed. 4. It is extremely important that care be taken to avoid sealing the surface of the bottom and sides of the absorption trenches through smearing. Trenches or beds shall not be excavated when the soil is sufficiently wet so as to smear or compact easily. All smeared or compacted surfaces occurring during construction shall be raked to a depth of one inch and loose material removed just before the gravel or other media is placed. The absorptive areas should not be walked on unnecessarily. The completed surface of the disposal area must not be paved, used for parking of vehicles, or covered with impermeable materials. Table 18.21.230 Absorption Trench and Bed Sizing for Single-Family Residential Dwellings Average Percolation Rate (Minutes/ Inch) | Sewage Application Rate, R a | Soil Texture (See Table 18.21.160 (A), Soil Textural Classifications) | Minimum Bottom Area (Sq. Ft.) for a One or Two Bedroom House: | Minimum Bottom Area for Each Additional Bedroom* (Sq. Ft./ Bedroom): Minutes Per Inch | Inches Per Hour | Gallons Per Sq. Ft. Per Day | Trench | Bed | Trench | Bed Less than 5 | More than 12 | Too great for consideration | Sand/ gravel | Sections on alternative systems 5—15 | 4—12 | 0.6 | Sandy loam | 380 | 750 | 200 | 250 15—30 | 2—4 | 0.5 | Sandy clay | 500 | 900 | 250 | 300 30—45 | 1.3—2 | 0.4 | Silty clay | 625 | 1125 | 300 | 400 45—60 | 1.0—1.3 | 0.3 | Clay loam | 800 | 1500 | 400 | 500 More than 60 | Less than 1.0 | Less than 0.3 | Clay | See sections on alternative systems _____ Minimum trench bottom area is calculated to include capacity for washing machine wastewater, organic material from garbage grinders, and infiltration of rainfall. Required minimum spacing between parallel conventional absorption trenches is 3 trench widths. * When dwellings consist of a large living area relative to the number of designated bedrooms, the following guidelines should be used to approximate the trench area: Less than 1,500 sq. ft.—Use trench area for two-bedroom house. 1,500 sq. ft. to 1,900 sq. ft.—Use trench area for three-bedroom house. For each additional 800 sq. ft.—Add trench area equal to one bedroom. This criteria is valid for normal water consumption by an average household occupancy and is not applicable to collective sewage system design. [image omitted; see the official code] B. Absorption Trench Field for Irregular Terrain. Where the topography or ground slope is too steep for feasible construction of a closed-looped trench system, the following alternate layout may be used. There shall be a minimum sixteen-inch drop from the bottom of the outlet pipe to the bottom of the first trench when trenches are installed in this configuration. 1. A single level trench, constructed like the closed-looped trench, is built along a contour. The overflow from this trench is conducted via a watertight pipe to the next lower level where a second trench can be built along a contour similar to the upper trench. The pattern can be repeated until the required minimum trench bottom area has been provided. It is required that no individual trench exceed seventy-five feet in length. This technique is graphically illustrated in Figure 18.21.230(B). Other details of trench construction described in subsection (A)(1) of this section, and shown in Figure 18.21.230(A), should be followed. The crossover trench must be as shallow as possible to prevent effluent from draining from upper to lower levels through disturbed soil. 2. Table 18.21.160(C) should be reviewed if the irregular terrain has sharp slopes and breaks. (Ord. 9448 (part), 1988)

El Paso City Code § 18.21.240 Soil absorption beds.

18.21.240 - Soil absorption beds. A. In addition to the trench-type absorption field, two or three absorption beds of reasonably equivalent areas, separated by at least four feet and using water tight flow diversion valving, (See Figure 18.21.240), may be used in areas where the combination of soil percolation and lot size precludes the use of a trench-type system with minimum spacing between trenches. While absorption beds require more bottom area than trenches, they tend to be more compact. B. The bed shall be constructed with its depth ranging from twenty-four inches to thirty-six inches. It shall be kept as shallow as possible to promote aerobic bacterial action in the soil. The bottom of the bed must be level to within plus or minus one inch for uniform wastewater distribution. Fill dirt or top soil shall not be placed on the bed bottom for any reason. Media (gravel, crushed stone, etc.) that is generally one uniform size from 0.75 to two inches shall be placed on the bed bottom followed by two or more distribution pipes spaced six to twelve feet apart and three feet from the edge of the bed. The amount of gravel and spacing between the pipes is dependent on the size of the pipe used. The distribution pipe is then surrounded with additional gravel to the top of the pipe. The pipe must be one size, from three to ten inches in diameter. The total depth of the gravel in the bed is twelve inches. The gravel shall then be covered with filtering material, such as several layers of newspaper, a layer of butcher paper, or geotextile filter fabric, to prevent the final soil layer from invading the gravel and reducing porosity. The next soil layer shall consist of sand, sandy loam, or a mixture of the two. C. Wicks. In order to provide continuous capillary action in the sand, wicks shall be incorporated in the rock media. Wicks are simply sand structures which penetrate through the rock media to the bottom of the bed (See Figure 18.21.240). The total wick area shall be ten to fifteen percent of the bed surface area and shall be uniformly spaced throughout the bed. Wicks may also be constructed by simply grading furrows in the rock media in between the distribution pipe. The total amount of rock media may be reduced by filling the initial twelve inches of the bed with coarse sand (2.0 mm) and placing rock media only around the top, bottom, and sides of the distribution pipe to form an eighteen-inch enclosure. D. Capillary Medium. If clay, rock, or other semi-impervious material is excavated from the bed site, it must be removed and under no circumstances be used as backfill in the bed. Sand or sandy loam will provide a capillary medium to help eliminate some of the wastewater through [image omitted; see the official code] [image omitted; see the official code] evapotranspiration. The bed shall be filled to within six inches from the top with sand or sandy loam and mounded with sandy loam so that the center of the bed is approximately four inches above normal ground elevation. This will provide drainage away from the absorption bed. When this system is used, the total absorption bed area must be calculated using the following formulas: For Dwellings: A = 150 (1 + B) / Ra Where: A = The total absorption bed area required for two beds. B = The total number of bedrooms in the dwelling. Ra = Sewage application rate for absorption trenches expressed as gallons per square foot of bed bottom, per day based on percolation rate. (See Table 18.21.230) For non-single family residential situations: A = 2Q / Ra Where: Q = The total daily wastewater discharge in gallons from that situation. (Ord. 9448 (part), 1988)

El Paso City Code § 18.21.250 Evapotranspiration beds.

18.21.250 - Evapotranspiration beds. A. General. Evapotranspiration bed systems may be used in locations where soil conditions are not suitable for any type of soil absorption system. For very porous soils, solutioned limestone, fractured bedrock, and situations that would allow excessively rapid migration of sewage toward groundwater, lined evapotranspiration beds must be designed and certified by a registered professional engineer or registered professional sanitarian. The beds must be located outside the flood-prone area and not within areas subject to inundation or erosion by flood waters or rainfall runoff. An applicant for a permit to install a sewerage system shall consult with the local floodplain ordinances administrator, county engineer, State Highways and Public Transportation Department, nearest river authority, Farmers Home Administration, Federal Emergency Management Agency, and any other officials who may have information regarding the potential for flooding at the site of the evapotranspiration beds. B. Construction Features. The following factors must be considered in the design of evapotranspiration beds: annual mean rainfall and wettest month of the year, annual mean evaporation rate and monthly minimal rate, growing season variations, native grasses and shrubs available for cover, absorptive capacity of the soil surrounding an unlined bed, and site conditions, including varying sunlight and air movement. 1. Evapotranspiration beds are constructed in impervious soil or soil with very high absorptive capacity. When the soils have a very high percolation rate, less than five minutes per inch, impervious liners must be constructed to guard against the possibility of wastewater discharging through the soil (fissured rock or gravel) and contaminating streams, lakes, or shallow groundwater. Impervious liners may consist of reinforced concrete, twenty mil minimum single layer thickness plastic, or rubber liners. All must be repairable in the field. Liners are not required in slowly permeable soils (having permeability of less than ten centimeters per second) and should not be used since some of the wastewater may be absorbed into the soil and will help to reduce the overall evapotranspiration load. An evapotranspiration system shall be designed using the following parameters: a. Beds may be designed in any configuration, but the total number of square feet of bed area must be determined by the formulas in subsection C of this section. b. At least two beds must be constructed with valving arranged to allow the effluent from a sewerage unit to alternate between each bed. When one bed becomes saturated (top of bed remains moist) the valving must be operated to allow effluent to flow into the alternate underloaded bedding. In order to determine the water level in the beds during use, an inspection port shall be installed in each bed. Inspection ports shall be designed to prohibit access to the bed bottom by insects, small animals, and unauthorized persons. c. The beds shall be constructed as shallow as possible with a depth ranging from eighteen inches to a maximum of thirty-six inches. This is necessary to keep the beds aerobic and prevent clogging. Treatment tankage should be installed as high as practical to permit shallow bed construction. d. Evapotranspiration Bed. Its design features, as illustrated in Figure 18.21.250(A), are as follows: i. All piping must be three to four inches in diameter. All perforated collection lines of an evapotranspiration bed monitor system must have a minimum crush strength of one thousand five hundred pounds per linear foot. The standpipe and sample sump must be of Schedule 40 polyvinylchloride or stronger. All connections shall be glued or rubber gasketed joints with the exception of the intruder resistant standpipe cap located at finished topsoil grade. Perforations in the collection lines must face downward, with the two rows of perforations equally offset perpendicular to the ground. ii. The end(s) of the perforated collection line(s) shall extend to within two feet of both opposite ends of the bed, measured at the bed bottom. iii. An evapotranspiration bed which is twenty feet wide or less shall have a minimum of one collection line which must be located centrally, down the length of the bed. An evapotranspiration bed which is greater than twenty feet but equal to or less than forty feet in width, shall have a minimum of two collection lines. These lines must be equally spaced (within approximately one foot) from the edge of the bed to pipe, and from pipe to pipe, installed parallel down the length of the bed. The two collection lines must be jointed by a perforated header line. As indicated in item (ii) of this subparagraph (B)(1)(c), the header line shall be within two feet, and parallel, to the edge of the bed measured at the bed bottom. 4. The collection line system must maintain a minimum fall of one-sixteenth inch per foot toward the standpipe/sump assembly. 5. The collection line(s) shall tee into a solid wall sandpipe which must have a sampling sump below the bottom of the tee. This sump shall be eight to twelve inches in depth, measured from the bottom of the tee. A cap or plug must be glued to the bottom of the sump to provide a watertight connection. The top of the standpipe shall be flush with the finished grade of topsoil, and shall be covered with an intruder-resistant, removable access cap. A minimum three inch wide by three inch deep dry moat shall surround the standpipe cap to facilitate ease of cap removal and replacement. 6. The pit bottom on which the collection line(s) shall be placed must be an impermeable surface, graded to provide a minimum fall of one-eighth inch per foot toward the collection line from either side. This will result in an impermeable shallow vee trench for the collection line to rest in. 7. The collection line(s) shall be located within the sand cushion required under lined beds. The minimum four inch sand cushion depth will increase as it follows the grade fall of the pit bottom toward the collection line. The backfill material around the standpipe should consist of sand or sandy loam. [image omitted; see the official code] 8. Rock media that is generally one uniform size from 0.75 to two inches shall be placed on the bed bottom to a depth of twelve inches or less depending on the overall bed depth, after the liner and sand cushion are placed over the monitor system. 9. The top of the distribution pipe must be flush with the rock media and adequate to provide for uniform distribution of effluent. A twelve-foot maximum separation between pipes and no less than three feet separation between bed walls and the pipe is permissible. The bed bottom and the pipe must be level. 10. A water permeable sand barrier (butcher paper, newspaper, or geotextile filter fabric) is then placed over the rock. Sand is then added to fill the bed to within two inches from the top. 11. In order to provide continuous capillary action in the sand, wicks shall be incorporated in the rock media. Wicks are simply sand structures which penetrate through the rock media to the bottom of the bed (See Figure 18.21.250(B)). The total wick area shall be ten to fifteen percent of the bed surface area and shall be uniformly spaced throughout the bed. Wicks may also be constructed by simply grading furrows in the rock media in between the distribution pipe. In areas of the state where rock media is difficult to obtain, the total amount of rock may be reduced by filling the initial twelve inches of the bed with coarse sand (two millimeters) and placing rock media only around the top, bottom, and sides of the distribution pipe to form an eighteen-inch enclosure, as indicated in Figure 18.21.250(B). 12. After the sand is in place, the final two inches of bed volume are filled with sandy loam and mounded with a downward slope of two to four percent. 13. Final bed construction consists of covering the surface of the bed with vegetation having good transpiration properties and providing for the most stormwater diversion that is practical. C. Bed Sizing. The bed area may be approximated by using the following formulas: A = 31,000 (1 + B) / EA—1/2 RFRA Where: A = Total area of both beds (to find one bed area divide A by 2) B = Total number of bedrooms (B = 2 for minimum residence) EA = Mean evaporation rate in inches per year (See Table 18.21.250) RFRA = Mean rainfall rate in inches per year (See Table 18.21.250) For non-single family residential situations: A = 310 Q / EA—1/2 RFRA Where: ;b10; Q = ;hg;Average daily flow into the system, expressed in gallons per day (see Table 18.21.190). Evaporation and rainfall data for various areas of the state are listed in Table 18.21.250. Additional data may be found in "Report 192" and "Report LP192" published by the commission. D. Plants and Grasses for Transpiration. The bed surface shall be covered with vegetation designed to take maximum advantage of transpiration, depending on the season and site's location. Evergreen bushes having shallow root systems can be planted in the bed to assist in water uptake. If grasses are used which have dormant periods, steps shall be taken to provide appropriate vegetation on the beds during these periods. Overseeding with winter grasses is commonly used to provide year-round transpiration. [image omitted; see the official code] Table 18.21.250 Mean Pan Evaporation and Rainfall Station | E A Mean Evaporation Rate (Inches/Year) | RFR A Mean Rainfall (Inches/ Year) Abilene | 75.0* | 23.8** Amarillo | 87.9 | 20.28 Austin | 70.0 | 32.49 Beaumont | 47.8 | 55.07 Brownsville | 56.0 | 25.13 Canyon Lake | 80.8 | 33.19 Corpus Christi | 67.0* | 32.0** Daingerfield | 74.2 | 46.12 Dallas | 85.0 | 35.94 El Paso | 106.5 | 7.77 Fort Stockton | 105.6 | 11.85 Houston | 48.7 | 48.19 Lake Somerville | 71.7 | 37.45 Laredo | 87.0* | 21.0** Lubbock | 88.7 | 18.41 Lufkin | 51.0* | 43.00** Midland-Odessa | 85.0* | 13.0** San Antonio | 70.0* | 30.0** San Angelo | 84.0* | 19.0** Temple | 68.2 | 34.00 Tyler | 55.0* | 42.0** Uvalde | 72.0* | 25.0** Wichita Falls | 73.0* | 27.0** _____ * Interpolated from map, p. 66 "Climatic Atlas of Texas" ** Interpolated from map, p. 18 "Climatic Atlas of Texas" (Ord. 9448 (part), 1988)

El Paso City Code § 18.21.260 Pressure dosing systems.

18.21.260 - Pressure dosing systems. A. Description. A basic pressure dosing system must consist of an approved sewerage system, an effluent holding tank, an easily serviced screened intake electric pump which is activated by a float or programmed start/stop switch, a solid wall force main, and perforated distribution piping which is installed within the absorption area. The effluent pump must be capable of an operating range that will assure that effluent is delivered to the most distant point of the perforated piping network, yet not be excessive to the point that blow-outs occur in shallow systems. The programmed start/stop switch should allow the pump to operate at least three times during the twenty-four-hour day. A high water alarm, on an electric circuit separate from the pump, must be provided. After the alarm activates, the effluent holding tank shall have remaining capacity of five hundred gallons for residences and one thousand gallons for businesses and institutions. The number of perforations per length of pipe and the number of pipe lengths used per absorption area must be adequate to assure uniform liquid distribution over the entire bed area. B. Application. Pressure dosing is an appropriate method of conveying effluent from a treatment site that is at a lower elevation than the disposal site. It is also appropriate where seasonal high water tables exist or where the soil mantle thickness is from two to four feet to solid rock. In these situations the system must be oversized substantially to promote the effect of evapotranspiration. Commercial establishments may need to use continuously staged pressure dosing if their flow rates vary greatly during their business hours. Pressure dosing systems shall be designed by a registered professional engineer. (Ord. 9448 (part), 1988)

El Paso City Code § 18.21.270 Mound systems.

18.21.270 - Mound systems. A. Physical Description. A mound system is comprised of a layering of sand fill, gravel, perforated pipe, and top soil. The layering begins in a two-to-three inch excavated area of natural ground and develops above the ground line approximately three feet. For greatest efficiency, its shape is rectangular. The small diameter perforated piping must be pressure-fed, as pressure systems have greater control over application rates. B. Application. The purpose of this type of construction is to overcome adverse conditions at the disposal site such as a high groundwater table, shallow soil, impermeable soils, and high potential for flooding, for example. In general, the mound is constructed of a high quality soil which is brought in from another area. Since there is a potential for leakage from this type of system which could result in the surfacing of sewage around its perimeter, it is not recommended for use except as a last resort. It may be used in an effort to improve the operation of a malfunctioning disposal system. Applications of effluent to a mound system depend upon the selection of fill materials used, the absorption rate of the natural ground, and depth to the shallow groundwater table. Mound systems shall be designed by a registered professional engineer. (Ord. 9448 (part), 1988)

El Paso City Code § 18.21.280 Residential collective systems.

18.21.280 - Residential collective systems. Collective private sewage facilities for residential properties shall meet the following additional requirements. Collective private sewage facilities shall be only approved for condominiums, planned unit developments, or any other entity legally authorized to assess and collect fees for the operation and maintenance of this collective disposal system, and individual or collective treatment systems. The right of the entity to assess and collect such fees shall be clearly defined to the licensing authority and in the lot owners agreement or other legal document issued by such entity to the lot owner. Proposed collective private sewage facilities shall be located above the one-hundred-year water surface elevation. (Ord. 9448 (part), 1988)

El Paso City Code § 18.21.290 Gravelless drainfield piping.

18.21.290 - Gravelless drainfield piping. A. Appropriateness. Gravelless pipe may be used in place of conventional gravel-filled trench systems. B. Physical Description. Gravelless pipe generally consists of eight-inch or ten-inch diameter corrugated polyethylene pipe having two rows of perforations located approximately one hundred twenty degrees apart along the pipe's bottom half. The pipe is enclosed in a layer of spunbonded nylon filter wrap. Pipe shall meet American Society for Testing and Materials, ASTM F-667 Standard Specifications, for large diameter corrugated high density polyethylene (ASTM D 1248) tubing. Perforations shall be one-half-inch diameter in ten-inch diameter pipe and three-eighths-inch diameter in eight-inch diameter pipe. Perforations shall be arranged and spaced so that only one hole exists in each inner corrugation. The filter cloth must meet ASTM D 3776 and ASTM D 1682 specifications for weight and grab strength. Its burst strength and air permeability must meet ASTM D 3786 and ASTM D 737 specifications, respectively. Installations must be in accordance with the pipe manufacturer's instructions. However, the system installer is cautioned against surrounding the pipe with native soils having percolation rates slower than thirty minutes per inch or laden with very fine soil particles that might plug the filter wrap. C. Design Parameters. The design of an absorption bed, absorption trench, or evapotranspiration disposal field utilizing this product shall be based upon the same parameters that are used in the design of more conventional systems. (Ord. 9448 (part), 1988)

El Paso City Code § 18.21.300 Design standards for disposal alternatives/special applications.

18.21.300 - Design standards for disposal alternatives/special applications. A. Greywater Systems. Generally, blackwater and greywater are approximately forty to sixty percent of the total domestic sewage flow, respectively. Subsurface greywater systems may be utilized with disposal of blackwater through a split system only under the following conditions: 1. A greywater disposal system utilizing anything other than conventional sewage treatment and absorption beds or trenches shall be designed and certified by a registered professional engineer or registered professional sanitarian who can provide to the licensing authority evidence that the system complies with all appropriate state regulations and local governmental regulations. 2. If flow restricting showerheads and faucet aerators are utilized throughout, a ten-percent reduction in greywater disposal trench, absorption bed, or evapotranspiration bed size will be allowed when a residential greywater system is incorporated into the disposal system design. The maximum allowable reductions in field size are determined by the type of system and the extent of watersaving fixture usage. B. Composting Toilets. The composting toilet unit must be listed with the NSF. The NSF seal on a particular unit indicates its ability to meet the requirements of the NSF Standard Number 41, relating to wastewater recycle/reuse and water conservation devices. The liquid waste from the composting toilet unit must be disposed of through an approved subsurface disposal system. C. Sewage Recycling Systems. For small on-site applications, sewage recycling systems are very limited in types and capability as follows: 1. On-site sewage recycling as flush water for urinals and commodes in commercial and institutional projects may be possible when advanced tertiary treatment processes are engineered into designs that meet or exceed NSF Standard Number 41 testing and certification requirements. An approvable design will be permitted only after the supplier and user of the recycle system enter into a post-installation inspection, maintenance, and repair agreement that satisfies the licensing authority. 2. Proposals to recycle highly refined sewage for use outside project buildings such as for surface landscape irrigation will be subject to requirements indicated in Section 18.21.080 of this chapter (relating to innovative designs) and by the Texas Commission on Environmental Quality in 31 TAC Sections 317.1-317.13 (relating to design criteria for sewerage systems). (Ord. 16818 § 2 (part), 2008; Ord. 9448 (part), 1988)

Source: City of El Paso, City Code and City Charter (Municode Library, library.municode.com)URL: https://library.municode.com/tx/el_paso/codes/code_of_ordinances?nodeId=TIT18BUCO_CH18.21PRSEFA_ARTVIDESTEFDISYFetched: 10/28/2026