PERC-RITE DRIP DISPERSAL DESIGN GUIDE FOR SEPTIC TANK OR ADVANCED TREATMENT EFFLUENT MAINE This Perc-Rite Design Guide is intended to simplify the design process of a Perc-Rite Drip Dispersal System. This technology is allowed for use by Section 6-GG of the Maine Subsurface Wastewater Disposal Rules, as amended on February 25, 2010 by the Perc- Rite Product Registration issued by the Wastewater and Plumbing Control Program. The Perc-Rite Drip Dispersal System is a unique fluid handling process for dispersal of wastewater into the soil. It incorporates filtration, time, and level-controlled application along with ultra-low rate drip distribution. The Perc-Rite Drip Dispersal System can disperse septic tank effluent, secondary effluent (from aerobic treatment units and other systems), or highly treated wastewater from membrane filtration or other methods. Most concepts for a Perc-Rite design will be familiar to the reader who has designed other leaching facilities. One exception to the standard design parameters will be that instead of determining the size of the disposal field using the Sizing Factor in Table 4D, one will determine the linear feet of drip tubing that is required for the project based on a table in this Guide. Offsets to restrictions (i.e. groundwater and bedrock) and other design standards should be maintained as stated in the Maine Subsurface Rules. This Design Guide contains commonly used configurations of smaller wastewater dispersal systems. Engineering design assistance is available for larger flow projects or for smaller flow projects with unique situations which do not fit within these basic design guidelines. The flexibility of the drip tubing, the uniqueness of the pressurecompensating emitter, and the different zone configurations which can be achieved allow for almost any site to be properly fitted with a Perc-Rite Drip Dispersal System. - 1 -
Typical Perc-Rite Drip Dispersal Components - 2 -
Perc-Rite Drip Dispersal Design Procedures for Maine By following these guidelines and standard design procedures, a Site Evaluator or Engineer can specify the appropriate Perc-Rite Drip Dispersal System needed. I. Site Assessment A. Determine design flow in gallons per day in accordance with the Maine Subsurface Wastewater Disposal Rules. B. Perform site evaluation in accordance with the Maine Subsurface Wastewater Disposal Rules. Note the only unique design limitation will be the inability for Perc-Rite Drip Dispersal to properly function beneath pavement, or beneath a gravel or dirt roadway which is driven over regularly. II. Perc-Rite Drip Tubing Calculation A. Determine Disposal Field Sizing Factor from Table 4D and chart below. Gallons per linear foot of Perc-Rite Drip Dispersal Tubing System Size Septic Tank Effluent Treated Effluent Medium 0.51 1.02 Medium-Large 0.40 0.81 Large 0.32 0.65 Extra-Large 0.27 0.53 B. Determine number of linear feet of drip tubing needed by dividing the design flow (in GPD) by the linear loading rate from the chart above. Note that for standard residential applications, a minimum of 400 linear feet of tubing is recommended. III. Perc-Rite Drip Dispersal System Design A. Determine area on property where drip tubing is to be placed. Depict perimeter and swing ties on Form HHE-200, also remember to depict existing ground elevation at corners and along the upslope edge. Tubing is typically placed 1-2 feet on-center when laid on an open bed of soil or fill material; tubing is typically placed 2 on-center when plowed into the existing ground in a lawn or lightly vegetated area; tubing is typically placed >2 on-center when plowed or trenched into sites with extensive vegetation. For ease of installation, selecting a long and narrow configuration following the contour of the land is recommended. - 3 -
There is no need to lay out and depict each drip tubing run as variation in drip tubing spacing will generally be best determined in the field by the installer and need not be depicted on the plan. For Engineered Systems only: B. Determine longest length of a single drip dispersal run which will be placed parallel to the site contours. C. Based on linear feet of tubing proposed and longest single length of drip tubing run, refer to the Standard Zone Selection Table in the Appendix and determine the appropriate Zone Detail. Contact Oakson, Inc. for an AutoCAD diagram of that detail. The Zone Detail will provide for the proper manifold system and appropriate number of zones for the project as well as a depiction of how construction is to occur. Once the Zone Detail is selected, the image is to be inserted as a separate detail on the design plan. It need not be inserted or depicted on the topographic contours. D. Contact Oakson, Inc. to acquire Detail Page to accompany site plan. Typically these notes and details are made into a separate page of the design plan, but are not required. - 4 -
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IV. Complete On-Site System Design Plan Typical site plan on HHE-200 Typical Detail on HHE-200-6 -
Typical Site Plan on Engineered Sheet On the design plan, show: A. Location of septic tank and treatment unit (if proposed). B. Location of pump chamber and hydraulic unit (note the hydraulic unit must be placed in a location which allows gravity return to the septic tank inlet). C. Indicate the area where the tubing is to be installed and depict any limiting setbacks that may exist such as property lines, wells, etc. - 7 -
D. Indicate the depth of tubing installation or amount of cover material to be provided. Note that the tubing installation depth, or depth of cover material to be imported, may be influenced by the following site variables: Separation from drip tubing to Bedrock Condition and Soil Drainage Condition in Table 4F. Installation depths may be as shallow as 6 for seasonal properties and 12 for year-round properties. Thickness of soil layers and the possible need to have the drip tubing placed in a particular soil horizon. E. Indicate the route of the supply and return pipes. F. For Engineered Systems: Depict Standard Detail sheet provided by Oakson, Inc.. Enhance Detail Sheet with Zone Detail selected from Zone Detail Table. G. Submit plans to Oakson, Inc. for confirmation of design parameters. H. Submit plans for review to appropriate regulatory agency as might be needed. - 8 -
Design Examples Example 1: Typical residential site; Septic Tank Effluent; tree in drip field to be preserved Assume a design flow of 360 gallons per day. Assume use of septic tank effluent. Assume a Medium-Large Disposal Field Sizing Factor From Table on Page 3 of Design Guide, use Perc-Rite Drip Tubing Loading Rate of 0.40 gal/linear ft/sq.ft. 360 gal/day/0.40gal/day/lin.ft.= 900 linear ft. of Perc-Rite Drip Dispersal tubing is required. Acceptable area for drip tubing shown by hatched area on site plan. During actual field installation, on-center spacing will vary to avoid the tree in the dispersal area. - 9 -
Assume a design flow 3,035 gpd Assume use of treated effluent Example 2: Larger system design; Treated effluent Assume a Medium Disposal Field Sizing Factor From Table on Page 3 of Design Guide, use Perc-Rite Drip Tubing Loading Rate of 1.02 gal/linear ft/ sq.ft. 3,035 gal/day/1.02gal/day/lin.ft.= 2,975 linear ft. of Perc-Rite Drip Dispersal tubing is required From the site plan above, the longest length of drip tubing will be 225. From the Standard Zone Selection Table in Appendix, select the zone detail at the intersection of 225 contour length and 2,975 linear feet. Since no detail exists at this intersection, move to the next largest area and select the zone detail at the intersection of 250 contour length and 3,000 linear feet, which would be a Z341. - 10 -
Zone Detail of Z341 Thank you for your interest in using Perc-Rite Drip Dispersal. This document is intended to assist you with design for many common wastewater projects. The flexibility inherent in the Perc-Rite Drip Dispersal system allows you to use this technology for a range of projects. Our dedicated team at Oakson, Inc. is committed to ensuring that your project will be successful. Please feel free to call or e-mail us with any projects or other items where we can be of assistance. 1-877-OAKSON1 Or info@oaksoninc.com - 11 -
APPENDIX Standard Zone Selection Table Length of Drip Field Parallel to Contour 50 75 100 125 150 200 225 250 300 Linear. Ft. of Perc- Rite Drip Tubing 400 Z124 Z142 450 Z133 500 600 Z125 Z152 Z126 Z134 Z143 Z123 Z132 Z124 Z142 Z122 Z141 Z151 Z123 Z132 Z122 Z141 Z131 Z122 Z141 Z121 Z131 Z121 Z121 625 Z151 675 Z133 Z131 Z135 750 Z152 Z132 Z151 Z131 Z153 Z144 Z142 Z141 800 Z224 Z222 Z221 Z242 Z241 900 1000 1200 Z136 Z233 Z145 Z225 Z252 Z226 Z234 Z243 Z134 Z143 Z223 Z232 Z224 Z242 Z133 Z251 Z223 Z232 Z142 Z222 Z241 Z132 Z231 Z222 Z231 Z141 Z221 1250 Z251 1350 Z233 Z231 1400 Z272 Z271 Z141 Z221 Z121 Z131 Z221-12 -
Z235 1500 Z252 Z232 Z251 Z231 Z253 1600 Z244 Z242 Z241 1800 Z236 Z326 Z234 Z324 Z233 Z323 Z232 Z322 Z331 Z241 1875 Z351 2000 Z254 Z252 Z242 Z251 Z241 2025 Z333 Z331 2100 Z372 Z371 Z231 Z321 Note Even 2250 Z335 2400 Z246 Z344 Z253 2352 Z244 Z424 Z243 Z342 Z423 Z332 Z351 Z242 Z422 Z341 Z431 2500 Z451 2700 Z334 Z341 Z333 Z332 Z434 Z431 2800 Z471 3000 Z452 Z352 Z342 Z432 Z451 Z351 3200 Z442 Z441 3375 Z353 Z351 3600 Z344 Z343 Z342 Z434 Z433 Z432 Z441 Z251 Z331 Z341 Z431 Z241 Z331 Z341 Z431 4000 Z452 Z442 Z451 Z441 4800 Z443 Z442 Z441 *Contact Oakson, Inc. for CAD images of these Zone Details or for design assistance with larger projects or unique situations not identified in this Table that the three digit Zone Detail number contains first the number of zones, then the number of laterals per zone, then the number of individual runs of tubing per lateral. For example Z222 has two zones (each one is alternatively supplied when the pump is activated), 2 laterals within each zone (to better divide up the flow evenly), and 2 individual runs of purple drip tubing within each lateral. numbers of runs are frequently advantageous as they allow the supply and return manifolds to be constructed at the same end of the dispersal area. - 13 -