PERC-RITE DRIP DISPERSAL DESIGN GUIDE FOR SEPTIC TANK OR ADVANCED TREATMENT EFFLUENT MASSACHUSETTS

Transcription

1 PERC-RITE DRIP DISPERSAL DESIGN GUIDE FOR SEPTIC TANK OR ADVANCED TREATMENT EFFLUENT MASSACHUSETTS This Design Guide is to assist you in specifying a Perc-Rite Drip Dispersal System for General Use or Remedial Use as allowed by Title 5 of the Massachusetts Environmental Code and the approval letters issued by the Massachusetts Department of Environmental Protection. The Perc-Rite Drip Dispersal System is a unique fluid handling process for ultra-low rate dispersal of wastewater into the soil. 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. The purple tubing is specially designed for our soil conditions to provide a successful solution to your disposal and re-use needs. Most concepts for a Perc-Rite design will be familiar to the reader who has designed other leaching facilities. Offsets to restrictions (i.e. groundwater and bedrock) will be maintained as indicated in the Title 5 and these generally allow a 4 to 5 offset from the drip tubing to the seasonal high water table; and, for upgrades using an approved pretreatment system, a 2 offset from the drip tubing to the seasonal high water table or bedrock or a 50% size reduction as allowed by the Remedial Use approval letter for that technology. Perc-Rite Drip Dispersal is considered equivalent to Pressure Distribution in all instances where this disposal technique is required by Title 5. This Design Guide contains commonly used configurations of smaller wastewater dispersal systems. Engineering design assistance is available for larger flow projects or for projects with unique situations which do not fit within these simple 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. Perc-Rite is a registered trade name of American Manufacturing Company, Inc., Elkwood, VA

2 Typical Perc-Rite Drip Dispersal System Components Adapted from American Manufacturing Company, Inc Patent #s 5,200,065; 5,984,574B; 6,261,452B1 2

3 Perc-Rite Drip Dispersal System Design Procedures By following these guidelines and standard design procedures, an Engineer or Sanitarian can specify the appropriate Perc-Rite Drip Dispersal System needed. I. Site Evaluation A. Determine design flow in gallons per day in accordance with Title 5. B. Perform test pits, percolation tests, etc. in accordance with Title 5. Pay attention to the upper soil layers as you might need to consider the suitability of the A soil horizon in the design. II. Leaching Area and Perc-Rite Drip Tubing Length Calculation Determine area needed for a standard Title 5 leach field. You may use the regular or pressure distribution loading rate chart in Section of Title 5. Determine the minimum linear footage of Perc-Rite Drip Dispersal tubing required by dividing the leach area by two. The Perc-Rite Drip Dispersal tubing is typically placed at 2 on center which means the actual leaching area is the same as a Title 5 system. In limited situations, there are some variables which occur such as: When more than the required amount of tubing is used in which case the tubing spacing will be reduced to less than 2 on center (12 minimum spacing) within the Title 5 required leaching area When an obstruction (such as a tree) is in the leach field area in which case the tubing may be placed closer together to preserve that site feature When the tubing is spaced greater than 2 on center at a new construction project. In this case the size of the dispersal field/area shall be increased so that the total linear feet of tubing is equal to the length that would have been installed in the standard 24 inch by 24 inch scenario. Reserve area may be located between the existing tubing provided a 4 on center tubing separation is utilized. The full size reserve area is required to be depicted on the design plan. When tubing is spaced greater than 2 on center at an upgrade project and simply extends beyond the minimum area required by Title 5 For applications when less than 400 linear feet of tubing is utilized please contact Oakson, Inc. for design assistance. III. Perc-Rite Drip Dispersal System Design A. Determine area on property where drip tubing is to be placed, depict on site plan. For ease of installation, selecting a long and narrow configuration following the contour of the land is recommended. 3

4 There is no need to depict each drip tubing run on the design plan as long as the appropriate area is available. The actual location of the installed drip tubing, if different from the approved design plan, must be shown on the as built plan submitted at project completion. Note that the following design limitations: Perc-Rite Drip Dispersal may not be specified beneath pavement, beneath a gravel or dirt driveway which is driven over regularly, or beneath a parking or heavy equipment storage area Class IV soils are not to be used with Perc-Rite Drip Dispersal Positive or negative head can be accommodated. Please contact Oakson, Inc. for assistance if the project will be pumping downhill B. Determine longest length of a single drip dispersal run which will be placed parallel to the site contours. C. Based on the total linear feet of tubing and the longest single length of drip tubing, refer to the Standard Zone Selection Table in the Appendix to determine the appropriate Zone Detail. Download from website or 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. Adapted from American Manufacturing Company, Inc

5 D. Download from website or contact Oakson to obtain Detail Page to accompany site plan. Typically this is made into the second page of the design plan, but is not required. Detail Page Adapted from American Manufacturing Company, Inc

6 IV. Complete On-Site System Design Plan Site Plan Example slightly raised above ground due to water table 6

7 On the design plan show: A. Location of septic tank and pre-treatment unit (if proposed). Note the use of a pre-treatment technology approved for Remedial Use can allow a reduction in system offset to water table, bedrock or system size as authorized by the approval for that technology. 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 such as property lines, wells, etc. and indicate the route of the supply and return pipes. D. Indicate the depth of tubing for a plowed in installation, or the amount of cover material to be provided for a raised bed installation. Note that the tubing installation depth, or the depth of cover material to be imported, is usually influenced by the separation from drip tubing to bedrock, impermeable layer, or water table as indicated in Title 5 (or, if used, the Massachusetts DEP approval letter for a pre-treatment technology). E. Depict Standard Detail sheet provided by Oakson, Inc. Enhance Detail Sheet with Zone Detail selected from Zone Detail Table. F. Submit plans to Oakson, Inc. for confirmation of design parameters. G. Submit plans for review to appropriate regulatory agency. H. Discuss with the owner the need for this technology, like any non-traditional system, to be maintained to assure proper operation. Doing so preserves both the investment placed into the property and our shared environmental resources by assuring proper treatment and dispersal of sewage. A maintenance agreement with a trained and licensed entity will need to be in place prior to construction. Single-family houses require semi-annual maintenance visits and other sites typically have quarterly maintenance. Specific Title 5 design factors which can be changed per Perc-Rite s approval letters are: A. Minimum cover required over tubing is 6 B. A & B soil horizons can be used and need not be removed C. No 5 overdig required D. No change to existing slope is required E. No inspection port is required F. Setback to a cellar wall may be 5 7

8 Design Examples Example 1: Residential Site; More Than Minimum Amount of Area Available; Tubing Length Remains Same; Tree in Drip Field to be Preserved Example 1: Site Plan larger than minimum area required is available, tree to be maintained 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 8

9 Assume a design flow of 330 gallons per day Assume a percolation rate of 15 minutes per inch, Class III soil From Title 5, determine that Loading Rate to be used to determine the area and number of linear feet of Perc-Rite Drip Dispersal tubing is gal/day/0.37 = 892 square feet required 892/2 = 446 linear ft. of Perc-Rite Drip Dispersal tubing required From the site plan above, the length parallel to the contour is 75 feet From the Standard Zone Selection Table it can be found that detail Z132 is suited for a run length of 75 feet with 446 linear ft. of drip dispersal tubing Z132 Zone Detail This image shows the manifold system to be constructed. Note that since this is for a single family house, the small amount of flow allows use of only one zone so all the drip tubing will be fed every time the pump is turned on Adapted from American Manufacturing Company, Inc

10 Example 2: Larger System Design Assume a design flow 4,400 gpd Assume percolation rate of 3 minutes per inch, Class I soil Example 2 Site Plan Acceptable area for drip tubing shown by hatched area on site plan. Irregular shaped drip fields are not of concern since the system operates under pressure to provide even distribution throughout 10

11 From Title 5, determine that Loading Rate to be used to determine the area and number of linear feet of Perc-Rite Drip Dispersal tubing is ,400 gal/day/0.74 = 5,950 sq ft Divide square feet by 2 to determine the required minimum amount of Perc-Rite Drip Dispersal tubing 5,950/2= 2,975 linear feet of drip tubing required From the site plan above, the longest length parallel to the contour is 225 From the Standard Zone Selection Table, 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 Z341 Z341 Zone Detail Due to the flow to be dispersed in this example, the design will use a 3 zone system which will have automatic rotation between the zones Adapted from American Manufacturing Company, Inc

12 Example 3: Residential Site; More Than Minimum Amount of Tubing to be Installed, Area Stays Same Example 3 Site Plan Minimum area required by Title 5 is available, drip tubing spaced closer than 2 o.c. in order to install more than minimum amount of tubing at the site Note impervious barrier is placed 1 off edge of drip tubing to meet the breakout requirement of Title 5 12

13 Assume a design flow of 220 gallons per day Assume a percolation rate of 15 minutes per inch, Class II soil From Title 5, determine that Loading Rate to be used to determine the area and number of linear feet of Perc-Rite Drip Dispersal tubing is gal/day/0.56 = 392 square feet required 392/2 = 196 linear ft. of Perc-Rite Drip Dispersal tubing required After consultation with Oakson, Inc. due to the requirement for less than 400 linear feet of tubing, it was determined to install 392 linear feet of Perc-Rite Drip Dispersal tubing at 1 o.c. From the site plan above, the length parallel to the contour is 49 feet From the Standard Zone Selection Table it can be found that detail Z124 is suited for a run length of 49 feet with 392 linear ft. of drip dispersal tubing Z124 Zone Detail This image shows the manifold system to be constructed. Note that since this is for a single family house, the small amount of flow allows use of only one zone so all the drip tubing will be fed every time the pump is turned on Adapted from American Manufacturing Company, Inc

14 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 tackle a range of projects without significant site disturbance. Our team is committed to making your project using Perc-Rite Drip Dispersal a success. Please feel free to call or us with any projects or other items where we can be of assistance. Oakson, Inc. is an authorized user of the Perc-Rite trade name and related materials for drip dispersal systems OAKSON1 Or info@oaksoninc.com 14

15 APPENDIX Standard Zone Selection Table Length of Drip Field Parallel to Contour Linear. Ft. of Perc-Rite Drip Tubing 400 Z124 Z122 Z Z133 Z123 Z132 Z131 Z Z152 Z151 Z122 Z Z134 Z124 Z132 Z122 Z131 Z Z Z133 Z Z135 Z152 Z132 Z151 Z Z144 Z224 Z142 Z222 Z141 Z Z136 Z233 Z134 Z232 Z133 Z132 Z231 Z141 Z221 Z Z145 Z252 Z251 Z142 Z222 Z141 Z Z226 Z234 Z224 Z242 Z232 Z222 Z231 Z Z Z233 Z Z272 Z Z235 Z252 Z232 Z251 Z231 15

16 Length Parallel to Contour Linear. Ft. of Perc-Rite Drip Tubing Required 1600 Z244 Z242 Z Z236 Z326 Z234 Z324 Z233 Z323 Z232 Z322 Z331 Z Z Z254 Z252 Z242 Z251 Z Z333 Z Z372 Z Z253 Z Z332 Z351 Z251 Z Z246 Z344 Z244 Z243 Z342 Z423 Z242 Z422 Z341 Z Z Z334 Z341 Z333 Z332 Z434 Z Z Z342 Z452 Z352 Z451 Z351 Z Z442 Z Z353 Z Z344 Z434 Z343 Z433 Z342 Z432 Z441 Z341 Z431 Z231 Z321 Z241 Z331 Z341 Z Z452 Z442 Z451 Z Z443 Z442 Z441 Adapted from American Manufacturing Company, Inc Note 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. Even numbers of runs (the last number in the three digit Zone Detail) are frequently advantageous as they allow the supply and return manifolds to be constructed at the same end of the dispersal area. If the appropriate box in the table is blank, choose the next largest detail. This may have the same or a longer length parallel with the contour. 16