Cut & Fill Septic Drainfield Design
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What is a "cut and fill" septic drainfield and is it constructed?
Here, based on expert sources cited at the end of this article we [DF] explain the design and give construction specifications for this type of septic system effluent absorption bed.
More generally, septic drainfields, also called leach fields, absorption beds, soil absorption systems, soakaway beds, and leaching beds, perform the functions of septic effluent treatment and disposal in onsite wastewater treatment systems, conventionally called "septic systems".
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Cut and Fill Septic Drainfield Systems
Below, based on the New York State septic code
NEW YORK STATE 75-A.8 SUBSURFACE TREATMENT of EFFLUENT
we summarize the basics of a cut & fill septic drainfield design.
A cut and fill septic system is an absorption trench system installed on sites where impermeable soil overlays a permeable soil.
In the most common design of drainfield, perforated pipes are buried in gravel-filled trenches to form the drainfield.
[Click to enlarge any image]
This sketch shows a cross section of a typical drainfield trench, and places below the trench the critical biomat as well as other septic field design areas and considerations. (Source US EPA who in turn obtained the drawing from Ayres Associates)
a. Site Requirements for cut and fill septic systems
Cut and fill septic systems may be used where all the following conditions are found:
(i) A soil with a percolation rate slower than 60 minutes per inch,
such as clay or clay loam, overlays a usable soil with a percolation rate faster than 60 minutes per inch;
(ii) At least three feet of usable soil is available beneath the tight soil;
(iii) All minimum vertical and horizontal separation distances can be maintained as described
at CLEARANCE DISTANCES, SEPTIC SYSTEM.
b. Design criteria for cut and fill septic systems
(i) It shall provide for the removal of the overlaying unusable soil and replacement by soil having a percolation rate comparable with the underlying soil.
(ii) An absorption trench system is designed as described
in CONVENTIONAL SEPTIC LEACHFIELDS.
(iii) The required length of septic effluent absorption trench is based upon the percolation of the underlying soil or the fill material, whichever has the slower percolation (lower permeability).
c. Materials used for Cut and Fill Absorption Trench Systems
Cut and fill trench septic systems use essentially the same materials as found
at CONVENTIONAL SEPTIC LEACH FIELDS
d. Construction of cut and fill septic systems
(i) The cut and fill septic system trench area excavated and filled must provide at least a five foot buffer
in each direction beyond the trenches.
(ii) The material placed above the cut and fill septic trenches
shall have a percolation rate faster than 60 minutes per inch.
(iii) Original surface material
shall not be used as backfill above the cut and fill septic system trenches.
(iv) The surface area of the cut and fill septic system
must be mounded and graded to enhance the runoff of rainwater from the system and seeded to grass.
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Continue reading at SEPTIC DRAINFIELD SHAPE or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.
Or see SEPTIC DRAINFIELD SIZE FAQs - reader questions & answers.
Or see these
Recommended Articles
- NEW YORK STATE 75-A.8 SUBSURFACE TREATMENT of EFFLUENT
- SEPTIC DRAINFIELD INSPECTION & TEST - home
- SEPTIC SOIL & PERC TESTS
- SEPTIC SYSTEM DESIGN ALTERNATIVES - home
- SEPTIC SYSTEM DESIGN BASICS
- U.K. OFF-GRID SEPTIC REGULATIONS & SEWAGE SYSTEMS
- U.S. SEPTIC AUTHORITIES & DESIGN SPECIFICATIONS - Septic codes & regulations for each US State or Territory
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SEPTIC DRAINFIELD DESIGN - CUT & FILL at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.
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INDEX to RELATED ARTICLES: ARTICLE INDEX to SEPTIC DRAINFIELDS & DBOXES
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Citations & Reviewers
In addition to any citations in the article above, a full list is available on request.
- NYS DOH, RESIDENTIAL ONSITE WASTEWATER TREATMENT SYSTEMS HANDBOOK [PDF] (2012) - original source: http://www.ongov.net/health/env/documents/DesignHandbook10_24_2
- WA DOH, BASIC PRINCIPLES of ONSITE SEWAGE [PDF] (1992) Washington State Department of Health, Office of Water, Washington D.C. USA
Also including as
APPENDIX A: WHY DO COARSE SOILS HAVE LARGER PORE SIZE & LESS SURFACE AREA? & WHY DO FINER SOILS HAVE SMALLER PORE SIZE & MORE SURFACE AREA
and
Cogger, Craig G., APPENDIX B: SEPTIC SYSTEM WASTE TREATMENT in SOIL, (1987) Washington State University Cooperatie Extension, EB1475, - [1] US EPA ONSITE WASTEWATER TREATMENT SYSTEMS MANUAL [online copy, free] Top Reference: US EPA's Design Manual for Onsite Wastewater Treatment and Disposal, 1980, available from the US EPA, the US GPO Superintendent of Documents (Pueblo CO), and from the National Small Flows Clearinghouse.
Original source http://www.epa.gov/ORD/NRMRL/Pubs/625R00008/625R00008.htm Onsite wastewater treatment and disposal systems, Richard J Otis, published by the US EPA.
Although it's more than 20 years old, this book remains a useful reference for septic system designers. U.S. Environmental Protection Agency, Office of Water Program Operations; Office of Research and Development, Municipal Environmental Research Laboratory; (1980) - [2] "International Private Sewage Disposal Code," 1995, BOCA-708-799-2300, ICBO-310-699-0541, SBCCI 205-591-1853, available from those code associations.
- [3] "Manual of Policy, Procedures, and Guidelines for Onsite Sewage Systems," Ontario Reg. 374/81, Part VII of the Environmental Protection Act (Canada), ISBN 0-7743-7303-2, Ministry of the Environment,135 St. Clair Ave. West, Toronto Ontario M4V 1P5 Canada $24. CDN.
- [4] Manual of Septic Tank Practice, US Public Health Service's 1959.
- [5] "Installers Manual for Conventional Onsite Domestic Wastewater Treatment and Disposal Systems", Department of Environmental Conservation, Division of Environmental Health Drinking Water and Domestic Wastewater Program, Alaska Department of Environmental Conservation, 1 Aug 2000, Anchorage Offices, 555 Coredova, Anchorage AK 99501, Tel: 907-269-7500. retrieved 17 July 2012, original source: http://dec.alaska.gov/water/wwdp/onsite/pdf/Certified_Installer%27s_Manual.pdf [Copy on file as Alaska_Certified_Installer's_Manual.pdf].
Notice: [Quoting]
This document contains information regarding the installation of onsite sewer systems for single-family and duplex residences. It must be used by Certified Installers and homeowners who are subject to 18 AAC 72. Additional requirements are included in 18 AAC 72. If there is a conflict between the provisions of this manual and 18 AAC 72, 18 AAC 80, or other state regulations, the regulations language controls. AEDC offices.
The regulations cited above for Alaskans can be found at https://dec.alaska.gov/commish/newsroom/23-15-updated-onsite-wastewater-regulations/ - [8] TEST PIT PREPARATION for Onsite Sewage Evaluations [PDF]State of Oregon Department of Environmental Quality, Portland OR, 800 452-4011. PDF document. We recommend this excellent document that offers detail about soil perc tests, deep hole tests, safety, and septic design.
- [9] Wells and Septic System, Alth, Max and Charlet, Rev. by S. Blackwell Duncan, $ 18.95; Tab Books 1992.
- [17] Thanks to reader Michael Roth for technical link editing 6/29/09.
- [19] Septic Tank/Soil-Absorption Systems: How to Operate & Maintain [ copy on file as /septic/Septic_Operation_USDA.pdf ] - , Equipment Tips, U.S. Department of Agriculture, 8271 1302, 7100 Engineering, 2300 Recreation, September 1982, web search 08/28/2010, original source: http://www.fs.fed.us/t-d/pubs/pdfimage/82711302.pdf.
- In addition to citations & references found in this article, see the research citations given at the end of the related articles found at our suggested
CONTINUE READING or RECOMMENDED ARTICLES.
- Carson, Dunlop & Associates Ltd., 120 Carlton Street Suite 407, Toronto ON M5A 4K2. Tel: (416) 964-9415 1-800-268-7070 Email: info@carsondunlop.com. Alan Carson is a past president of ASHI, the American Society of Home Inspectors.
Thanks to Alan Carson and Bob Dunlop, for permission for InspectAPedia to use text excerpts from The HOME REFERENCE BOOK - the Encyclopedia of Homes and to use illustrations from The ILLUSTRATED HOME .
Carson Dunlop Associates provides extensive home inspection education and report writing material. In gratitude we provide links to tsome Carson Dunlop Associates products and services.
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