PB85-107126
Oregon Onsite Experimental Systems Program
Oregon State Dept. of Environmental Quality
Portland
Prepared for
Municipal Environmental Research Lab.
Cincinnati, OH
Oct 84
L
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EPA-600/2-«4-157
October 1984
OREGON ONSITE EXPERIMENTAL
SYSTEMS PROGRAM
by
Mark P. Ronayne
Robert C. Paeth
Steven A. Wilson
State of Oregon
Department of Environmental Quality
Portland, Oregon 97207
Grant NO. S806349
Project Officer
James F. Krelssl
Wastewater Research Division
Municipal Environmental Research Laboratory
Cincinnati, Ohio 45268
MUNICIPAL ENVIRONMENTAL RESEARCH LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
CINCINNATI, OHIO' 45268
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TECHNICAL REPORT DATA
[Pleat rtad luirucnons on tht rtveni bt/ort compltrinf/
-84-157
2.
3. RECIPIENT'S ACCeSSlON>NO.
107126
4. TlTLi AND SUBTITLE
OREGON ONSITE EXPERIMENTAL SYSTEMS PROGRAM
5. REPORT DATS
October 1984
*. PiRFORMING ORGANIZATION CODE
7. AUTHO«(S)
I. PSRFOPMINQ ORGANIZATION REPORT NO.
Mark A. Ronayne, Robert C. Paeth and
Steven A. Wilson
9. PERFORMING ORGANIZATION NAME AND ADDRESS
State of Oregon
Department of Environmental Quality
P.O. Box 1760
Portland. OR 97207
10. PROGRAM ELEMENT NO.
AZB1B
11. CONTRACT/GRANT NO.
S806349
12. SPONSORING AGENCY NAME AND ADDRESS
Municipal Environmental Research Laboratory-Cin., OH
Office of Research and Development
U.S. Environmental Protection Agency
Cincinnati, OH 45268
13. TYPE OF REPORT AND PERIOD COVf RED
Final (11/78 - 5/82)
14. SPONSORING AOINCY CODE
EPA/600/14
IS. SUPPLEMENTARY NOTES
Project Officer: James F. Kreissl (513) 684-7614
!«. ABSTRACT
This study was Initiated to develop useful design and performance data on
alternative onsite wastewater treatment and disposal systems which would permit
the use fo non-sewered technological solutions to residents of rural and suburban
areas of the State of Oregon and the rest of the United States.
In order to exclude the possibility of system failure due to homeowner
neglect or abuse, all systems were Installed at homeowner's expense. The systems
were chosen for the most part to suit the specific climate, soil conditions and
topography of the location from a variety previously developed and locally
conceived systems urith varying degrees of modification to suit the application.
Among the technologies evaluated were three types of sand filters, two types of
evapotransplration systems, mounds, biological ("composting") toilets, graywater
systems, steep-slope systems, pressure distribution, tlle-dewatering systems,
~and-vartou5T:omb1 nattonsrof .the- above.
-- This report^ was- submitted 1n -fulfillment t>f -grant number S806349 by the
Oregon Department of Environmental Quality under the partial sponsorship of the
U.S. Environmental Protection Agency. This report covers a period from November
17. 15, 1978 to May 14, 1982. KBY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.IDENTIFIERS/OPEN ENDED TERMS
COSATl Fi«ld/Group
18. DISTRIBUTION STATEMENT
Release to public
19. SECURITY CLASS (Tha Riport)
Unclassified
21. NO. OF PAGES
20. SECURITY CLASS
Unclassified
22. PRICI
tPA Perm 22)0-1 (»-73)
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DISCLAIMER
Although the Information described 1n this article has been funded whol-
ly or 1n part by the United States Environmental Protection Agency
through assistance agreement number; S 806349 to Oregon Department of
Enviromental Quality, it has not been subjected to the Agency's re-
quired peer and administrative review and therefore does not necessari-
ly reflect the views of the Agency jand no official endorsement should
be inferred." !
rt
ii
TYPii'JG GUiOL. SML[I
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FOREWORD
The US Environmental Protection Agency was created because of
Increasing public and government concern about the dangers of pollution
to the health and welfare of the American people. Noxious air, foul
water, and spoiled land are tragic testimony to the deterioration of
our natural environment. The complexity of that environment and the
Interplay between Its components require a concentrated and Integrated
attack on the problem.
Research and development 1s that necessary first step 1n problem
solution and 1t Involves defining the problem, measuring Its Impact,
and searching for solutions. The Municipal Environmental Research
Laboratory develops new and Improved technology and systems for the
prevention, treatment, and management of wastewater and solid and
hazardous waste pollutant discharges from municipal and community
sources, for the preservation and treatment of public drinking water
supplies and to minimize the adverse economic, social, health, and
aesthetic effects of pollution. This publication is one of the products
of that research; a most vital communications link between the research-
er and the user community.
This report relates the results of statewide study of alternative
wastewater treatment and disposal technologies for individual homes.
Because of the diversity of climate, soils and topography within the
State of Oregon the results should have wider applicability beyond the
borders of that state. Because more than one-fourth of the U.S. is not
served by community-wide collection and treatment, the potential Impact
of the technologies studied should be significant. Further, the
practical nature of this work should enhance its adoption by other
states in a way that more theoretical studies cannot often achieve.
Francis T. Mayo
Director
Municipal Environmental Research Laboratory
ill
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ABSTRACT
This study was Initiated to develop useful design and performance
data on alternative onsite wastewater treatment and disposal systems
which would permit the use of non-sewered technological solutions to
residents of rural and suburban areas of the State of Oregon and the
rest of the United States.
In order to exclude the possibility of system failure due to home-
owner neglect or abuse, all systems were Installed at homeowner's
expense. The systems were chosen for the most part to suit the specific
climate, soil conditions and topography of the location from a variety
of previously developed and locally conceived systems with varying
degrees of modification to suit the application. Among the technologies
evaluated were three types of sand filters, two types of evapotranspira-
tion systems, mounds, biological ("composting") toilets, graywater
systems, steep-slope systems, pressure distribution, t1le-dewater1ng
systems, and various combinations of the above.
Significant results of the study included the consistent capability
of sand filters to significantly remove nitrogen, remove organlcs and
suspended solids to extremely lew levels, and forestall development of
clogging mats In subsequent disposal trenches; the success of hand-dug
systems on slopes up to 45 percent where soils were deep (> 5 ft);
successful demonstration of the ability to pressure distribution to
prevent groundwater contamination where the unsaturated soil depth
exceeds 30 Inches; the Impracticability of evapotranspiration and mound
systems in Oregon; and the substandard performance of some commercial
graywater treatment systems compared to conventional septic tank and
reduced (by hydraulic flow change) size disposal fields.
This report was submitted 1n fulfillment of grant number S806349
by the Oregon Department of Environmental Quality under the partial
sponsorship of the U.S. Environmental Protection Acency. This report
covers a period from November 15, 1973 to May 14, Ho2.
-J
i
iv
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CONTENTS
Chapter Page
ABSTRACT iv
LIST OF FIGURES ix
LIST OF TABLES x
1 INTRODUCTION 1-1
2 RECIRCULATING SAND FILTER SYSTEMS 2-1
Methods 2-1
Recirculating Sand Filter Design 2-1
Monitoring 2-5
Results and Discussion 2-6
Operation and Maintenance 2-6
Sand Filter Effluent Quality 2-7
Disposal Field Performance 2-14
Conclusions 2-17
References 2-18
3 INTERMITTENT SAND FILTER SYSTEMS 3-1
Methods 3-1
Intermittent Sand Filter Design 3-1
Monitoring 3-8
Results and Discussion 3-8
Operation and Maintenance 3-8
Sand Filter Effluent Quality 3-10
Disposal Field Performance 3-16
Conclusions 3-19
References 3-22
4 INTERMITTENT RECIRCULATING SAND FILTER SYSTEMS 4-1
Methods 4-1
System Design 4-1
Monitoring 4-6
Results and Discussion 4-7
Hydraulic Loading 4-7
Sand Filter Effluent Quality 4-7
Industrial Filter Effluent Treatment 4-19
Filter Operation and Maintenance 4-23
Filter Modifications 4-31
Intermittent Reoirculatinq Pea-Gravel Filters 4-31
Alternate Resting and Dosing
of Filter Effluent Absorption Trenches 4-37
Intermittent Recirculating Gravel-Sand Filter 4-38
Disposal Field performance 4-42
Conclusions 4-48
References 4-50
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CONTENTS
Chapter
5 EFFECT OF TILE DRAINAGE ON DISPOSAL OF SEPTIC
TANK EFFLUENT IN WET SOILS 5-1
Methods and Materials 5-2
Site Description 5-3
System Design 5-3
Water Table Observations 5-6
Drainage Water Quality Parameters 6-7
Results and Discussion 5-7
Water Table Drawdown 5-7
Drainage Water Quality £-9
Conclusions 5-12
References 5-14
6 SEEPAGE TRENCHES IN SOILS WITH SLOW AND VERY
SLOW PERMEABILITIES 6-1
MfiOods and Materials 6-2
Site Description 6-2
S.'stem Design 6-2
S-'Stem Monitoring 6-3
Result. 6-4
Discussion 6-7
Conclusions 6-10
References 6-11
7 SEEPAGE TRENCHES ON STEEP SLOPES 7-1
Methods 7-1
Results and Discussion 7-3
Conclusions 7-4
3 DISPOSAL TRENCHES IN SOIL SHALLOW TO WEATHERED
AND FRACTURED BEDROCK 8-1
Methods 8-2
Results and Discussion 8-4
Conclusions and Recommendations 8-6
9 PRESSURE DISTRIBUTION SYSTEMS IN SOILS WITH
SHALLOW GROLJNDWATER 9-1
Methods 9-2
Results and Discussion 9-4
Conclusions and Recommendations 9-7
vi
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CONTENTS
Chapter
10 EVAPOTRANSPIRATION SYSTEMS 10-1
Methods 10-1
Results and Discussion 10-2
Conclusions 10-3
11 EVAPOTRANSPIRATION ABSORPTION SYSTEMS 11-1
Methods 11-1
Results and Discussion 11-4
Conclusions 11-8
12 MOUND SYSTEMS 12-1
Methods 12-1
Mound Design 12-1
Monitoring 12-10
Results and Discussion 12-10
Mound Treatment 12-10
Mound Operation and Maintenance 12-13
Conclusions 12-15
References 12-17
13 GRAY WATER 13-1
Results and Discussion 13-2
Recirculating Sand FiUer 13-2
Pea-Gravel Filter 13-5
Trickle Rock Filter 13-5
Cipax 198-Gallon Septic Tank 13-7
Standard 1000-Gallon Septic Tank 13-10
Conclusions 13-11
References 13-12
14 COMPOSTING TOILETS 14-1
15 CHARACTERISTICS OF RESIDENTIAL AND INDUSTRIAL
SEPTIC TANK EFFLUENTS 15-1
Methods 15-1
Results and Discussion 15-3
Residential Septic Tank Effluent Quality 15-3
Industrial Septic Tank Effluent Quality 15-5
References 15-6
VII
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CONTENTS
Chapter
16 SUBSURFACE SYSTEM COST
Results and Discussion
Conclusions
Page
16-1
16-3
16-6
Appendices
APPENDIX A OREGON ADMINISTRATIVE RULES
CHAPTER 340, DIVISION 74
APPENDIX B SITE SELECTION CRITERIA
APPENDIX C ON-SITE SEWAGE DISPOSAL RULES,
ALTERNATIVE SYSTEMS, OREGON ADMINISTRATIVE
RULES, CHAPTER 340; DIVISION 71,
RULES 260-320.
APPENDIX D SITE SELECTION CRITERIA
APPENDIX E PROGRESS REPORT, COMPOSTING TOILETS,
FEBRUARY 28, 1978
APPENDIX F PROGRESS REPORT, COMPOSTING TOILETS,
JANUARY 30, 1979
APPENDIX G PROGRESS REPORT, COMPOSTING TOILETS,
DECEMBER 18, 1979
A-l
8-1
C-l
0-1
E-l
F-l
G-l
viii
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FIGURES
Page
RECIRCULATING SAND FILTER 2-4
AVERAGE MONTHLY TEMPERATURES AND
PRECIPITATION RECORDED AT ROSEBURG
MUNICIPAL AIRPORT, DOUGLAS COUNTY OREGON,
BETWEEN 1900 AND 1957 2-11
3-1 DOUBLE CELLED INTERMITTENT SAND FILTER 3-4
3-2 SINGLE CELL INTERMITTENT SAND FIITER 3-5
3-3 INTERMITTENT SAND FILTER PLACED IN SOILS 3-6
SHALLOW TO SAPROLITE OR FRACTURED ROCK
4-1 INTERMITTENT RECIRCULATING SAND FILTER 4-3
4-2 INTERMITTENT RECIRCULATING PEA-GRAVEL FILTER 4-32
4-3 INDUSTRIAL INTERMITTENT RECIRCULATING 4-39
GRAVEL-SAND FILTER
5-1 TILE DEWATERING SYSTEM PLAN AND DETAIL OF 5-4
PERIMETER DRAIN AND DISPOSAL FIELD
5-2 DETAIL OF SILT TRAP AND MONITORING PORTS 5-5
7-1 STEEP SLOPE SYSTEM PLAN AND DETAIL OF SEEPAGE TRENCH 7-2
8-1 SAPROLITE SYSTEM PLAN AND DETAIL OF DISPOSAL TRENCH 8-3
9-1 LOW PRESSURE DISTRIBUTION SYSTEM PLAN AND
DETAIL OF DISPOSAL TRENCH 9-3
11-1 DIKED EVAPOTRANSPIRATIGN ABSORPTION PLAN 11-2
11-2 SERIAL DISTRIBUTION EVAPOTRANSPIRATION SYSTEM PLAN 11-3
12-1 SAND FILL MOUND WITH PRESSURE DISTRIBUTION TRENCHES 12-8
12-2 MOUND WITH PRESSURIZED DISTRIBUTION BED 12-9
13-1 GRAY WATER RECIRCULATING SAND FILTER SYSTEM 13-3
13-2 PEA-GRAVEL FILTER 13-6
13-3 CIPAX 198-GALLON SEPTIC TANK 13-8
ix
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TABLES
Page
DESIGN CHARACTERISTICS FOR RECIRCULATING
SAND FILTERS 2-2
2-2 AVERAGE DAILY SEWAGE FLOWS AND LOADING
RATES FOR RECIRCULATING SAND FILTERS 2-5
2-3 RECIRCULATING SAND FILTER OPERATION AND
MAINTENANCE NEEDS 2-8
2-4 A COMPARISON BETWEEN SINGLE FAMILY
RESIDENTIAL SEPTIC TANK EFFLUENTS AND
RECIRCULATING SAND FILTER EFFLUENTS 2-9
2-5 CHARACTERISTICS OF 8 OREGON SINGLE FAMILY
RESIDENTIAL SEPTIC TANK EFFLUENTS 2-10
2-6 A SEASONAL COMPARISON OF NITRATE AND
TOTAL NITROGEN CONCENTRATIONS IN RECIRCULATING
SAND FILTER EFFLUENT ' 2-12
2-7 A DESCRIPTION OF SITE CONDITIONS, SOIL ABSORPTION
TRENCHES, AND TRENCH PERFORMANCE AT RECIRCULATING
SAND FILTER LOCATIONS 2-15
2-8 A COMPARISON BETWEEN RECIRCULATING SAND FILTER
SOIL ABSORPTION TRENCH EFFLUENT ACCEPTANCE
RATES AND SEPTIC TANK EFFLUENT LOADING RATES
RECOMMENDED BY BOUMA AND MACHMEIER IN SIMILAR SOILS 2-16
3-1 DESIGN CHARACTERISTICS FOR INTERMITTENT SAND FILTERS 3-2
3-2 SANDS USED IN OREGON INTERMITTENT FILTERS 3-2
3-3 INTERMITTENT SAND FILTER HYDRAULIC LOADING
CHARACTERISTICS 3-7
3-4 SAND CHARACTERISTICS, LOADING RATES, AND SELECTED
SEPTIC TANK EFFLUENT CHARACTERISTICS OF 5
INTERMITTENT SAND FILTERS 3-9
3-5 A COMPARISON BETWEEN SINGLE FAMILY RESIDENTIAL
SEPTIC TANK AND INTERMITTENT SAND FILTER EFFLUENTS 3-11
3-6 CHARACTERISTICS OF 8 OREGON SINGLE FAMILY
RESIDENTIAL SEPTIC TANK EFFLUENTS 3-12
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TABLES
Page
A COMPARISON BETWEEN INTERMITTENT SAND
FILTER EFFLUENTS 3-13
3-8 DOSING RATE VS. FECAL AND TOTAL COLIFORM
REMOVAL PROVIDED BY INTERMITTENT SAND FILTERS 3-15
3-9 A DESCRIPTION OF SITE CONDITIONS, SOIL ABSORPTION
TR^CHLS, AND TRENCH PERFORMANCE AT 4 INTERMITTENT
S,«ND FILTER SYSTEM LOCATIONS 3-17
3-10 THE RELATIONSHIP BETWEEN GROUNDWATER LEVELS AND
WATER LEVELS OBSERVED IN DISPOSAL TRENCHES
FOLLOWING THE LA JOIE SAND FILTER FROM MAY 1977 -
MAY 1980 3-18
3-11 A COMPARISON BETWEEN INTERMITTENT SAND FILTER
SOIL ABSORPTION TRENCH EFFLUENT ACCEPTANCE
RATES AND RECOMMENDED SEPTIC TANK EFFLUENT
LOADING RATES 3-21
4-1 DESIGN CRITERIA FOR INTERMITTENT RECIRCULATIKG
SAND FILTERS 4-2
4-2 INTERMITTENT RECIRCULATING SAND FILTER
CONSTRUCTION DETAILS 4-4
4-3 AVERAGE DAILY LOADING RATES FOR 6 INTERMITTENT
RECIRCULATING SAND FILTERS 4-8
4-4 A COMPARISON BETWEEN SINGLE FAMILY RESIDENTIAL
SEPTIC TANK AND INTERMITTENT RECIRCULATING
SAND FILTER EFFLUENTS 4-9
4-5 CHARACTERISTICS OF 8 OREGON SINGLE FAMILY
RESIDENTIAL StPTIC TANX EFFLUENTS 4-10
4-6 A COMPARISON BETWEEN INTERMITTENT RECIRCULATING
SAND FILTER EFFLUENTS 4-11
4-7 A SEASONAL COMPARISON OF NITROGEN CONCENTRATIONS
IN RESIDENTIAL INTERMITTENT RECIRCULATING SANO
FILTER EFFLUENTS 4-12
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TABLES
Number
4-8 THE RELATIONSHIP BETWEEN RESIDENTIAL INTERMITTENT
RECIRCULATING SAND FILTER TREATMENT AND FILTER
ABSORPTION TRENCH MATTING; PRE-MAT DEVELOPMENT
PERIOD 4-14
4-9 THE RELATIONSHIP BETWEEN RESIDENTIAL INTERMITTENT
RECIRCULATING SAND FILTER TREATMENT AND FILTER
ABSORPTION TRENCH MATTING; AFTER A MAT FORMED 4-15
4-10 THE RELATIONSHIP BETWEEN RESIDENTIAL INTERMITTENT
RECIRCULATING SAND FILTER TREATMENT AND FILTER
ABSORPTION TRENCH MATTING; AFTER TRENCH CLOGGING
AND EFFLUENT PONDING ABOVE THE FILTER SURFACE 4-16
4-11 A COMPARISON BETWEEN INDUSTRIAL SEPTIC TANK AND
INTERMITTENT RECIRCULATING SAND FILTER EFFLUENTS
(SYSTEM 9) 4-20
4-12 THE RELATIONSHIP BETWEEN INTERMITTENT RECIRCULATING
SAND FILTER SEPTIC TANK EFFLUENT ABSORPTION BED
MATTING AND FILTER TREATMENT (SYSTEM 9) 4-21
4-13 INTERMITTENT RECIRCULATING SAND FILTER OPERATION
AND MAINTENANCE NEEDS 4-22
4-14 THE RELATIONSHIP'BETWEEN BIOMAT FORMATION IN
INTERMITTENT RECIRCULATING SANC FILTER SEPTIC
TANK EFFLUENT ABSORPTION TRENCHES WITH HYDRAULIC
LOADING, INFLUENT BODc AND SUSPENDED SOLIDS
AND FILTER SAND CHARACTERISTICS 4-27
4-15 A COMPARISON BETWEEN SINGLE FAMILY RESIDENTIAL
SEPTIC TANK AND INTERMITTENT RECIRCULATING
PEA-GRAVEL FILTER EFFLUENTS 4-34
4-16 A COMPARISON BtTWiEN 2 SINGLE FAMILY RESIDENTIAL
SEPTIC TANK AND INTERMITTENT RECIRCULATING PEA-
GRAVEL FILTER EFFLUENTS 4-35
4-17 A COMPARISON BETWEEN INDUSTRIAL SEPTIC TANK
AND INTERMITTENT RECIRCULATING GRAVEL/SAND
FILTER EFFLUENTS (SYSTEM 9) 4-40
4-18 A DESCRIPTION OF SITE CONDITIONS, SOIL ABSORPTION
TRENCHES, AND TRENCH PERFORMANCE AT 5 INTERMITTENT
RECIRCULATING SAND FILTER SYSTEM LOCATIONS 4-44
xll
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TABLE?
Page
A COMPARISON BETWEEN INTERMITTENT RECIRCULATING
SAND FILTER SOIL ABSORPTION TRENCH EFFLUENT
ACCEPTANCE RATES AND SEPTIC TANK EFFLUENT LOADING
RATES RECOMMENDED BY BOUMA AND MACHMEIER
IN SIMILAR SOILS 4-47
5-1 EFFECT OF TILE DRAINAGE ON GROUNDWATER LEVEL 5-8
5-2 EFFECT OF DISPOSAL TRENCHES ON TILE DRAINAGE WATER 5-10
6-1 DISPOSAL TRENCHES IN SOILS WITH SLOW PERMEABILITY 6-4
6-2 DISPOSAL TRENCHES IN SOILS WITH VERY SLOW
PERMEABILITY 6-5
6-3 SEEPAGE TRENCHES IN SOILS WITH VERY SLOW
PERMEABILITY 6-6
7-1 STEEP SLOPE SYSTEMS 7-4
8-1 PERFORMANCE OF DISPOSAL TRENCHES IN SOILS
SHALLOW TO WEATHERED BUDROCK (SAPROLITE) 8-5
9-1 MEAN BACKGROUND AND POWNGRADIENT GROUNDWATER
QUALITY FOR PRESSURIZED EFFLUENT DISPOSAL
SYSTEMS 9-5
11-1 SERIAL DISTRIBUTION EVAPOT&ANSPIRATION-ABSORPTION
SYSTEMS 11-5
11-2 DIKED EVAPOTRANSPIRATION-ABSORPTION SYSTEMS 11-5
11-3 FAILING SERIAL DISTRIBUTION EVAPOTRANSPIRATION-
A3SORPTION 11-6
12-1 HOUND DESIGN CRITERIA 12-2
12-2 MOUND PRESSURIZED DISTRIBUTION SYSTEM
CONSTRUCTION DETAILS 12-4
12-3 ACTUAL MOUND HYDRAULIC LOADING 12-5
12-4 MOUND SOIL ABSORPTION SYSTEM DETAILS 12-7
12-5 MOUND HATER QUALITY MONITORING DATA 12-11
12-6 A DESCRIPTION OF SITE CONDITIONS AND HOUND
PERFORMANCE 12-14
xiii
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TABLES
Number Page
13-1 A COMPARISON OF SFPTIC TANK AND RECIftuJLATING
SAND FILTER EFFLUENTS; VAN DER WERF GRAY
WATER SYSTEM 13-4
13-2 BENDER 55-GALLON PEA-GRAVEL FILTER EFFLUENT
QUALITY 13-7
13-3 FRANS GRAY WATER 198-GALLON SEPTIC TANK EFFLUENT
QUALITY 13-9
13-4 MEADOR 1000-GALLON SEPTIC TANK EFFLUENT
CHARACTERISTICS 13-10
15-1 DETAILS OF RESIDENTIAL SEPTIC TANKS 15-2
15-2 DETAILS OF INDUSTRIAL SEPTIC TANKS 15-2
15-3 CHARACTERISTICS OF 8 SINGLE FAMILY RESIDENTIAL
SEPTIC TANK EFFLUENTS 15-3
15-4 CHARACTERISTICS OF 2 INDUSTRIAL SEPTIC TANK
EFFLUENTS 15-5
16-1 OREGON ON-SITE SUBSURFACE SYSTEMS VS.
SITE CONSTRAINTS 16-2
16-2 SUBSURFACE SYSTEM CONSTRUCTION AND OPERATION
AND MAINTENANCE COSTS ($) 16-3
16-3 COST OF INDIVIDUAL COMPONENTS OF ON-SITE
SEWAGE SYSTEMS 16-5
XG1185 x1v
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ACKNOWLEDGEMENTS
This project would not have baen possible without the active participa-
tion of Department and Contract County Staff who assisted 1n system
design, supervision of construction, monitoring, and analysis of re-
sults.
The authors thank James F. Krelssl, EPA Project Officer, for assistance
1r, preparation of the grant application and constructive criticism
during the course of the study and preparation of the final report.
The authors would like to express their most sincere appreciation to
the following: ;
Contract Supervisors:
Engineering Consultant:
Monitoring Technicians:
Harold L. Sawyer, P.E., Administrator
Water Quality Division
T. Jack Osborne, R.,S., Supervisor
On-S1te Sewage Systems Section
James 1.. Van Dome!en, P.E.
j
Gregory A. Pettit
Thomas A. Berkemeler
Patrick J. Wuilliez
Reviewers: William C. Bowne, P.E.1, Douglas County Department of
Public Works !
Roy L. Burns, R.S., Lane County Planning and Community
Development Department
Sherman 0. Olson, Jr., R.S., DEQ, On-Site Sewage Systems
Section
Stephen R. Wert, C.P.S.S., northwest Soil Consulting,
Roseburg, Oregon
i
Word Processors; Linda G. W1rth ;
Bonnie L. Nasshahn
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Chapter 1
INTRODUCTION
Oregon's Administrative Rules for subsurface sewage treatment and disposal
were developed 1n 1973 when Oregon law repealed State Health Division
authority for this program. Jurisdiction was transferred to the Department
of Environmental Quality (DEQ) and a statewide site evaluation and permit
program was Initiated. These rules specified minimum requirements 1n terms
of soil, groundwater, landscape, and other parameters for approval for
on-s1te subsurface sewage disposal. The rules Included measurable site
standards but also relied on Interpretation and subjective judgment of
soil, landscapes, and groundwater for site evaluation and design of on-s1te
disposal systems.
The number of on-s1te subsurface sewage construction permits Issued 1n
Oregon Increased from 8,645 1n 1974 to 13,614 1n 1978. A tightening
economy caused a reduction 1n new construction 1n ]979, 1980 and 1981 and
the number of on-s1te subsurface sewage construction permits dropped to
10,870, 8,529, and 5,653 respectively. In spite of this, many Oregon
property owners and developers were not able to develop land and build
homes because they could not obtain permits for on-s1te subsurface sewage
systems. This situation aggravated the housing shortage, stimulated higher
prices on existing housing, and Increased pressure to develop prime
agricultural land. These trends were 1n conflict with Oregon land use
planning Goal 10 "to provide for the housing needs of the citizens of the
1-1
CD
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state" and Oregon land use planning Goal 3 "to preserve and maintain
agricultural lane's". This conflict prompted the DEQ to develop
alternatives to the standard septic tank and drainfield. In addition,
suitable alternatives were needed to repair failing systems that were
causing public health and groundwater problems.
The DEQ presented a request (SB 388) to the 1975 Legislature for $750,000
to retain Oregon State University to conduct a comprehensive study to:
(1) Analyze existing soil absorption systems to relate their performance
tj kind of soil, landscape, depth to groundwater, and ether factors;
(2) Characterize bench mark soils statewide so that dr^nfield performance
could be scientifically predicted from soil and site conditions; and
(3) Install and tect a variety of experimental systems designed to over-
come marginal soil and site conditions where standard systems could
not be approved.
The 1975 Legislature did not fund this proposal. In spite of this, the DEQ
initiated a nonfunded, scaled-down experimental program in 1975 which was
subsequently funded jointly by the 1977 Oregon Legislature and the United
States Environmental Protection Agency,
Direction and policy of the Experimental Sewage Disposal Systems program
was spelled out in detail 1n Oregon Administrative Rules (Department of
1-2
(2)
-------
Environmental Quality, 1978, Appendix A). Briefly, the intent of the
program was to develop alternatives to the standard septic tank and
drainfield through controlled experimentation. The DEQ identified problem
soil areas, either with a history of failing systems or high denial rates,
selected suitable sites according to defined criteria (Appendix B),
designed alternatives to overcome site limitations, supervised
construction, mon.tored system performance, evaluated data, and drafted
rrles to adopt alternatives that would function satisfactorily. The land
owners installed systems according to plans and specifications and allowed
DEQ access to monitor. In addition, the owners had to be willing to risk
investing mcney on experimental systems that may fail.
Sufficient data have been collected to indicate that some systems
functioned properly and others did not. As a result, mounds and
evapotranspiration systems were dropped from the experimental program. The
Oregon State Department of Commerce Plumbing Section assumed legal
jurisdiction for composting toilets October, 1977. The Evapotranspiration-
Absorption System was approved as Regional Rule C, July 1, 1979 and
subsequently adopted as an alternative system March 13, 1981. The sand
filter was adopted as an alternative system January 1, 1980 and the steep
slope system, the tile dewatering system, the split waste system, and
the low pressure distribution system were adopted as alternative systems
March 13, 1981, and revised March 8, 1982 (Appendix C). As a result, the
site evaluation approval rite statewide Increased from 72% in 1978 to over
95* during the first hal; of 1981. These systems were dropped from the
1-3
(3)
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experimental program and new site selection criteria (Appendix D) were
developed to reflect these changes.
A report on each individual kind of system appears 1n the following
chapters. Soil and site conditions, acreage estimates and climatic
Information, where applicable, are disc ssed. System designs and
monitoring methods are included. Performance is evaluated and dis-
cussed. Conclusions are drawn and recommendations made. In addition there
is a chapter on Characteristics of Residential and Industrial Septic Tank
Effluents and a chapter en Subsurface System Costs.
XG1126 1-4
(4)
-------
'<«^
CHAPTER 2
RECIRCULATING SAND FILTER SYSTEMS
There ara several minion acres of soils in Oregon (1) with one or more
limitations, other than slope that makes them not suitable for installation
of standard onsite waste disposal systems. These soils are limited either
by shallow depth to hard pans, claypans, saprolite, bedrock, and
groundwater, or by permeability rates either too rapid for adequate
treatment or permeability rates too slow for adequate disposal. Standard
soil absorption systems were not permitted 1n these soils under Oregon
Administrative Rules (2) berause of a history of surface failure and
the potential hazard of groundwater contamination. Recirculatlng sand
filters, Intermittent sand filters, and Intermittent recirculating sand
filters were installed 1n a number of these sites to determine 1f sand
filter treatment was adequate to produce effluent of high enough quality to
prevent surface failures and groundwater contamination from final disposal
in a standard disposal field. This section discusses recirculating sand
filter performance.
METHODS
Four recirculating sand filters were Installed 1n Douglas County In Western
Oregon. Sand filter system sites were located 1n foothills near the
Eastern edge of Oregon's Coast Mountain Range.
RECIRCULATING SAND FILTER DESIGN
Recirculating sand filter design was similar to H1nes and Favereau (3)
using design characteristics in Table 2-1. A pit 12 ft x 12 ft x 4 ft
2-1
-------
excavated into natural soil and underlying geological material. The pit
was lined with a 10 mil vinyl liner to prevent infiltration of
groundwaler.
TABLE 2-1. DESIGN CHARACTERISTICS FOR RECIRCULATING SAND FILTERS1
Surface Area 144 ft2
Filter Media Depth 3 ft
Media Effective Size 1.2 urn
Media Uniformity Coefficient 2.0
Maximum Design Loading Rate 3.125 g/ft2/d
No. Times Effluent Applied to 3 to 4
Filter Before Discharge minimum
No. Doses Per Day 48
No. Gallons Dcsed/ft2/Cycle 0.10-0.17 g/ft-/dose
No. Gallons Applled/Dose 15 - 25 gal
Dosing Controls Percentage
* All sand filters were designed to process up to 450 gal septic
tank effluent per day,
A 4 1n. perforated underdrain was placed in the bottom of the sand filter
container and covered with about 8 1n. of 3/4 1n. washed gravel. The
filter container was then filled with 3 ft of nickel mining slag with an
effective size of 1.2 mm and a uniformity coefficient of 2.0. The
distribution system was installed above the sand filter bed (Figure 2-1).
Very coarse sand sized media was used to allow filters to continuously
receive wastewater at a high hydraulic loading rate and still maintain
aerobic conditions for rapid treatment of septic tank effluent.
2-2
(6)
-------
Filter systems were designed so household wastewater, first treated by a
septic tank, drained into a recirculating tank. Each half hour,
approximately 20 gallons of wastewater were pumped from the redrculation
tank to the open filter surface. Pump cycles lasted 5 minutes. A 25-
minute resting period followed each pump cycle (Table 2-1). Pumping events
were regulated by time clock controls. Pumped effluent was distributed to
the exposed filter surface from 10 ft long, half sections of 4 1n. diameter
plastic pipes with downturned 1/2 in. holes on 5 1n. centers. Distribution
piping was positioned immediately above the filter surface. Piping was
supportea by trestles made of steel rebar anchored in the filter media
(Figure 2-1). After effluent drained through 3 ft of filter media and 1 ft
of gravel, 1t entered a 4 1n. diameter perforated plastic pipe underdraln
at the base of the vinyl liner. Effluent collected 1n the underdrain
flowed back to the redrculation tank. Within the recirculatiou tank, a
custom-made downturned ball check valve attached to the underdraln return
piping regulated whether filtrate drained back Into the redrculation tank
or bypassed to disposal trenches. When the liquid level 1n the
recirculaticn tank vas low enough to permit a ball to hang loosely below a
downturned "tee" opening, filtered effluent entered the redrculation
tank. When the liquid level rose sufficiently to cause the ball to float
securely against the "tee" opening, effluent bypassed the redrculation
tank and discharged to 2 ft deep, 2 ft wide soil absorption trenches which
contained 4 1n. diameter perforated plastic distribution piping bedded 1n
12 1n. of washed gravel.
2-3
(7)
-------
Recirculation
Tank
Disposal Field-
/-* ro
oo i
^ -U
4" Distribution Trough
4" Underdrain
FIGURE 2-1. RECIRCULATING SAND FILTER
-------
MONITORING
Average daily sewage flow was 209 gallons and the average daily filter
loading rate was 1.45 gal/ft (Table 2-2).
TABLE 2-2 AVERAGE DAILY SEWAGE FLOWS AND LOADING RATES FOR RECIRCULATIN6
SAND FILTERS
SYSTEM
1 (Stratton)
2 (Moody)
3 (Triplett/Perry)
Mean Values
DAILY
FLOW (gpd)
246
127
255
209
(3)1
FLOW/FILTER
SURFACE (q/ft2/d)
1.71
0.88
1.77
1.45
(3)
1
Number of samples.
Filters were monitored to determine their mechanical operation and
maintenance needs as well as their capacity to treat septic tank effluent.
Effluent samples were collected and analyzed for BOD5, SS, NCL , N02, NH-,
total kjeldahl nitrogen (TKN), total nitrogen (TN), fecal coliform (FC),
and total coliform (TC). Nitrate + nitrite-nitrogen was determined by the
hydrazine reduction method, nitrite-nitrogen was determined through
automated analysis by technicon, ammonia-nitrogen was determined by the
phenate colorimeteric method, and total kjeldahl nitrogen samples were
digested in a technicon block digester and analyzed by the automated
phenate method (4). Suspended solids were determined using U.S. EPA
methods for chemical analysis of water and wastes (4). BOD^ was determined
by the Modified Winkler method and fecal and total conforms were
determined using the membrane filter method (5).
2-5
(9)
-------
Disposal trench absorption rates were determined during the summer months
when disposal trenches were not Inundated by seasonal grountiwater.
RESULTS AND DISCUSSION
OPERATION AND MAINTENANCE
Redrculatlng sand filter surfaces were subjected to accumulation of leaves
and other fallen debris and vegetative growth. Alg*e, mosses, grasses, and
many other weed varieties grew abundantly on filter surfaces during spring,
sunnier, anr| parly fall ronths. Leaf Utter, other organic debris, algae,
and thick mats of finis also accumulated In filter distribution troughs.
Accumulated materials Clogged distribution trough drain holes when troughs
were not maintained (Table 2-3).
In mid-October 1979, Douglas County engineering staff reconstructed
System 3's effluent dlstrloutlon system, replacing distribution troughs
with a grid network of 16 shrub spray heads. After 6 weeks operation, half
the shrub spray head orifices were clogged with organic matter.
Removal of leaves and other wind blown Utter was required at least once
each fall. Filter surface weeding and distribution trough cleaning was
required at least twice annually, once during the spring and once during
summer months.
No maintenance was carried out on the filter surface and distribution
piping of System 1 to determine the effect of Utter and vegetative
growth on filter operation. During the monitoring period, weeds covered
2-6
(10)
-------
up to 601 of the filter's surface and the system's 2 distribution trough
perforations were clogged causing redrculated effluent to discharge from i
ilngle place on the edge of each trough. In spite of this, effluent from
the redrculatlon tank continued to be accepted by the filter without
ponding.
After filters had been 1n operation for a few months, wood frame box
structures covered by screen and hardware cloth were located over filter
surfaces io prevent access by animals and children and prevent debris from
falling onto filter surfaces. Even though filters were protected by these
structures, distribution trough alignment was easily disrupted. When out
of alignment, all eff^ent drained to the filter surface from one end or
edge of each trough. Although troughs could be easily returned to their
proper positions on supportive rebar trestles, system users failed to
realign distribution piping once It was out of alignment.
Faint ammonia odor was detectable near all reclrculatlng sand filters
during winter months (Table 2-3). In addition, « slight sewage oJor was
apparent at System 1.
Purap failure occurred twice at System 4 (Table 2-3). The pump's electrical
system failed when control wiring, exposed to corrosive gases, shorted.
SAND FILTER EFFLUENT QUALITY
Recirculatlng sand filters reduced BOD5 99% and decreased SS by 97%
(Table 2-4). Total nitrogen was reduced 45X. Ninety-five percent of the
2-7
(ID
-------
TAftE 2-3. RfCIROJLATirG SWC F L7I£ Cr^RAi !•>( Art) WIKTDWd NODS
ALGAL (A), M)SS (M), DISTRIBLfTICN FILTER DISTRIBUTE
VODS (W)AIAVES (L) TROUGH OR IF ICES TRCiJQG
SYSTEM
1 (Stratton)
Z(H«M
ON FILTER
SWO SUtFPCE
Yes
(A)(M)(W)(L)
Yes
(W)
CLOGGED BY
ORGMIC MATTE?
Yes
Yes
WCtf-ED Off OF
*4.IGHC(T
Yes
Yes
CDCR
Yes; sll^it
v*«7? arri ff^
1n wlnta1"
Yes; slltfrt
ti\2 In winter
FAIUUPE
.'to
%o
MDT.THS
OB^ER'/H)
46
48
TTMES
OBSER'-U)
18
16
3 (TrlpletV Yes
Perry) (A)(M)(W)(L)
Yes
No Yes; si i(tit Ho
h« 1n winter
91
Bqylls
Yes
Yes
Yes Yes; sll^tt Yes; control 10
*Vj 1n winter wiring
, 2 tknes
XG867.A
-------
^SfcSfSfiSfi&Sfr^lflPWMSlSW?
nitrogen In sand filter effluent was 1n the nitrate form compared to less
than IS 1n septic tank effluent.
TABLE 2-4. A COMPARISON BETWLEM SINGLE RMILY RESIDENTIAL SEPTIC TANK
EFFLUENTS AND RECIRCULATING SAM) FILTER EFFLUENTS1
EFFLUENT
CHARACTERISTIC
BOOj
SS
N02
»3
W3
TKN
TN
FC
TC
Nuiter
Systems
SEPTIC2
TANK
EFFLUENT
217
(70)4
146
(70)
0.02
(57)
0.4
(59)
40.6
(60)
57.1
(57)
57.5
(54)
2.6 x 1C5
(56)
1.32 x 106
(46)
5
RECIRdlLATING3
SAND FILTER
EFFLUFNT
2.7
(82)
3.8
(82)
0.06
'28)
29.9
(51)
0.45
(51)
1.1
(51)
31.5
(51)
8.5 x 103
(10&)
1.0 x 104
(46)
4
%
CHANGE
99
97
67
99
99
98
45
97
(2 logs)
99
(2 logs)
* BODc, SS and nitrogen expressed as mg/1, arithmetic mear Fecal and
total collforr, expressed as org/100 ml; geometric mean.
2 Arithmetic r<;an of 8 systems (Table 2-5).
3 Arithmetic average of 4 systems.
4 Number of samples.
Total nitrogen 1n sand filter effluent fluctuated seasonally (Table 2-6)
from a low of 23.59 mg/1 in cool moist Months (November to April) to a
2-9
(13)
-------
high of 36.80 mg/1 1n warm dry months (May to October). These data and
precipitation records (Figure 2-2) suggested that rainfall dilution was
responsible for the apparent decrease of total.nitrogen during the November
to April period. Nitrate-nitrogen concentrations were 36% lower in cool,
moist months than they were in warm, dry months (22.55 mg/1 compared to
35.5C mg/1).
TABLE 2-5. CHARACTERISTICS OF 8 OREGON SINGLE FAMILY RESIDENTIAL SEPTIC TANK EFFLUENTS
SEPTIC TWK EFFLUENT CHARACTERISTICS1
SYSTEM
1 (McCurley)
2 (Gilkey)
3 (Groans)
4 (Boettcher)
5 (Reber)
6 (McClaflin)
7 (Roberts)
8 (Anderson)
Weighted
AHtJTetlC
Average
AVh.
FU3W
(9Pd)
191
113
139
194
176
161
174
—
164
(7)
BODs
149
(8)2
197
(11)
188
(7)
222
(11)
378
(7)
125
(16)
348
(7)
322
(3)
217
(70)
SS
240
(8)
38
(11)
79
(7)
193
(11)
276
(7)
91.7
(16)
171
(7)
203
(3)
146
(70)
N&3
0.18
(9)
0.81
(10)
0.04
(7)
—
0.16
(6)
0.56
(16)
0.38
(8)
0.24
(3)
0.4
(59)
N02
0.02
(9)
0.02
(10)
0.02
(6)
—
0.03
(7)
0.02
(15)
0.02
(7)
0.02
(3)
0.02
(57)
™3
37.8
(9)
35
(10)
35.5
(7)
—
53.3
(7)
36.1
(16)
55.9
(8)
32,56
(3)
40.6
(60)
TKN
56.9
(9)
58.4
(10)
45.6
(7)
—
71.8
(6)
51.30
(16)
70.5
(7)
47.2
(2)
57.1
(57)
TN
57.1
(9)
59.20
(10)
45.67
(6)
—
71.9
(5)
51.80
(15)
70.9
(7)
47.45
(2)
57.5
(54)
FC
2.0
1.1
7.0
5.4
8.0
1.0
8.1
2.6
(
xlO4
(10)
x 105
(10)
xlO4
(6)
—
xlO5
(6)
xlO4
(14)
xlO5
(8)
xlO4
(2)
xlO5
55)
TC
1.5 x 105
(8)
1.8 x 106
(9)
7.7 x 105
(5)
—
2.1 x 105
(6)
9.9 x 105
(10)
2.5 x 105
(6)
1.3 x 105
(2)
1.32 x 106
(46)
s, SS, aid nitrogen expressed as mg/1; arithretic mean. Fecal and
total coliform expressed as org/ICO ml; geonetric mean.
2 Nuiter of samples.
2-10
(14)
-------
70
2-60
£50
0>
>.
«x
40
6
5
1 4
i—'
Q- o
Q_ 0
o>
5 2
1
0
JFMAMJJASQND
FIGURE 2-2. AVERAGE MONTHLY TEMPERATURE AND PRECIPITATION RECORDED AT THE ROSEBURG
MUNICIPAL AIRPORT, DOUGLAS COUNTY. OREGON, BETWEEN 1900 AND 1957 (6).
-------
Organically bound and free ammonia nitrogen concentrations during these
periods remained relatively constant (Data not shown). This suggested,
that either organically bound nitrogen accumulated as biomass within the
filter during cool, moist months and mineralized during the dry, warm
months, or denitrification occurred during cool, moist months when filter
media remained wetter. No biomass was observed when pits were excavated
into filter sands, so the latter explanation is more likely.
Denitrification probably occurred in anaerobic microsiles consisting of
moisture films on sand grains and at points of sand grain contact. Law (7)
reported similar denitrification of treated sewage occurred in
microanaerobic sites in gravel-filled, shallow tanks, left open to the
atmosphere. Denitrification was also possible in the zone of near
saturation in the sand bed just above the sand-gravel interface.
TABLE 2-6. A SEASONAL COMPARISON OF NITRATE AND TOTAL NITROGEN
CONCENTRATIONS IN RECIRCULATING SAND FILTERED EFFLUENT1
N03-N TOTAL N
SYSTEM
1 (Stratton)
2 (Moody)
3 (Triplett/Perry)
Weighted
Arithmetic
Average
NOV-APRIL
12.2
(8)2
27.82
(7)
29.14
(7)
22.55
(22)
MAY-OCT
26.53
(3)
49.46
(3)
34.87
(23)
35.5
(29)
NOV-APRIL
12.94
(8)
28.85
(7)
30.54
(7)
23.59
(22)
MAY-OCT
27.27
(3)
50.49
(3)
36.27
(25)
36.80
(29)
1 Nitrogen concentrations expressed as mg/1; arithmetic mean.
2 Number of samples.
2-12
(16)
-------
A small amount of nitrogen loss may also have been due to ammonia volatil-
ization, particularly during warm dry months, but data does not support
this hypothesis.
Redrculatlng sand filters reduced total and fecal conform organisms by an
average of 2 logs (Table 2-4). The ra». -f flow and the number of passes
through filter media determined the level of bacterial removal (Data not
shown). Flow rates through treatment media were controlled by media
texture and pore size. Very coarse sands allowed rapid percolation of
effluent, resulting 1n limited filtering of bacteria and little time for
bacterial reduction to take place.
Surprisingly, effluent distribution efficiency and clogging of distribution
troughs by weeds had little measurable Impact on effluent quality. Even
after holes in filter distribution troughs became clogged by organic debris,
causing effluent to spill onto the filter surface at 1 or 2 points at the
edc^es of distribution piping, no difference 1n effluent quality was detected
at System 1, When piping was out of alignment, causing effluent to spill from
a small re
-------
DISPOSAL FIELD PERFORMANCE
In spite of the fact that absorption trenches were placed on sites which
were severely limited by shallowness to groundwater or rock or slowly
permeable soils, all disposal fields functioned satisfactorily. No surface
failures occurred and disposal trenches accepted effluent at the rate of
1.89 to 2.8 gal/ft2/d (Table 2-7). Disposal trenches at System 3 were
installed to replace a failing (surfacing) disposal field. Trenches were
installed at the same time the repair sand filter was constructed. They
showed no signs of failure during or after 47 months use in spite of the
fact trench sidewalls were completely or partially inundated by surface
water infiltration 3-5 months each year. Throughout that time, trenches
received an average of 255 gal sand-filtered effluent per day.
Wert (13) reported that treatment of septic tank effluent by sand
filtration substantially reduced the rate of soil clogging. Although
investigators disagree on which causative agent plays the most active
role in clogged mat development, they all agreed that BOD5, SS,
and fecal bacterial organisms were primarily responsible (8, 9, 10,
11, 12). Sand filtration markedly decreased all of these constituents
(Table 2-4).
Table 2-8 compares the mean rates sand filter effluent was accepted by
silty clay loam and silty clay soils at three filter sites with septic tank
effluent loading rates Bouma (14) and Machmeier (15) recommended for much
deeper, better drained soils of similar texture. The effluent acceptance
rate shown for System 2 was conservative. The first disposal trench at
2-14
(18)
-------
2-7. A DESOtiPTKN OK SITE OHIITIOHS, SOU ABSORPTION TCOOCS, AHD TROCH fWOWCE AT RGdROLATUC S6M3
FILTER SYSIW LOCf,nO«
SYSTtM
FT4TIRE DESCUbED
Soil Absorption Syslan
Site LtaHatlon
Soil Texture at
Absorption Trench
S1dB*ll
Slope (X)
Av». Drain* (eld
Loat^g Rate (gpd*
"irench Tvpe. Length,*
and Sldfwall Absorp-
tion Area (ft2)
Avc. Dally Trendi
Sldaall Loading
Rate (g/fWd)
Avc. rercart Svsta?
Sldewll Used for
Absorbing Effluent
Trench installation
Date
Observation Period
Nwtw of Observations
1 (S1RATTON)
Slowly permeable clawun
si 10-19 In., weathered basalt
rt 20-36 In.; perches seasonal
Mater table at 10 1n.
ii1 In. sllty clw over weathered
basalt; 1TM5 1n. sllty clay over
clay
15-33
246
3-seHal trenches
300 I1n. n
(600)
1.89
8.3
tfylOT
May 1977-Narch 19B1
18
1 Average treeh depth MS 24 In.; trenches contained 12 1n.
distribution piping.
2(MX»f)
slowly permeable claypan
at 33 In.; suspected seasonal
grartcbater
20 In. sllty clay loan ovr
clay
4
127
3-seHal trenches
150 I1n. ft
(300)
2.5
16.6
Nmeiter 1976
March 1977-Harch 19SI
29
washed gravel » +iffm4\iw~* eawt * 41f af^ei ^f fit *ant- Mac /lofiirminAl ^•Hnn rt~tAT ctntna* mmifhc af ftiA ^ivxffnn anrf Tirinlaffr cit
since s1de>ells were often partially or totally inrdated by graunoVMter Arlrq h1(/i rainfall norths (Kovotber-ApHl). Percent $1da>al1
absorption area used to absorb effluent detcrnined In wet winter (norths.
£805(1}
-------
that system was not uncovered and no monitoring well was placed In the
trench, so the actual trench liquid level of that system was not
determined. However, effluent did not reach the system's second drop box.
Acceptance rates 1:. Table 2-8 assumed 6 1n. of the trench sldewall was
continuously inundated. Wert (IS) estimated the silty clay horizon 1n
2
System 1 accepted effluent at a rate of 0.2 gal/ft/day and the basalt
2
saprolite accepted effluent at the rate of 1.69 gal/ft /day. The effluent
acceptance rate varied along the 125 ft disposal trench in System 3 but
averaged 2.8 gal/ft2/day (13) In a silty clay loam trench sidewall.
Patterns of unequal effluent acceptance were reported by other inves-
tigators in silty soils (16). Zones of highest permeability occurred
where the soil contained a large number of macropores.
TABLE 2-8. A COMPARISON BETWEEN RECIRCULATING SAND FILTER SOIL ABSORPTION
TRENCH EFFLUENT ACCEPTANCE RATES AND SEPTIC TANK EFFLUENT LOADING
RATES RECOMMENDED BY 60UMA AND MACHMT.IER IN SIMILAR SOILS
RECOMMENDED SEPTIC TANK?
, EFFLUENT LOADING RATE (g'd/ft2)
FILTERED1
SOIL EFFLUENT ACCEPTANCE
SYSTEM TEXliJRE RATE (g/d/ft2) BOUMA MAPMEIER
1 (Stratton) silty clay over basalt 1.893 0.24 0.45
saprolite and clay
2 (Woody) silty clay loan 2.5 0.72 0.50
over clay
3 (Triplett/ siIty clay loam 2.8 0.24 0.45
Perry)
* Based on sldewall area.
2 Based on bottom area.
3 The first 60 ft of trenches were located 1n 19 in. silty clay covered weathered
basalt. The last 40 ft of trenches were installed through 10-15 in. silty clay
ove*- 10-25 In. clay over weathered tasalt.
2-16
(20)
-------
CONCLUSIONS
The surfaces of redrculatlng sand filters were subject to accumulation of
leaves, other fallen debris, and vegetative growth which tended to clog
the effluent distribution system. In spite of this, there was no rceasur-
able impact on treatment.
BOD5, SS, and total nitrogen were reduced 99*, 97*, and 4556 respectively.
Denitrlfication probably occurred 1n anaerobic moisture films on sand
grains and at points of sand grain contact and 1n the zone of near
saturation just above the sand-gravel interface.
Total and fecal collform organisms were reduced by 2 logs.
Sand filtration of septic tank effluent significantly Increased the
disposal trenches effluent acceptance rate.
2-17
(21)
-------
REFERENCES
State Water Resources B^ard, 1969. Oregon's Long-Range Requirements for
Water. Genera] Soil Map Report with Irrigable Areas. Appendices I-
1 through 1-18.
2 Department of Environmental Quality, 1975. Chapter 340, Division 71,
Standards for Subsurface and Alternate Sewage and Nonwater-Carried
Waste Disposal, Revised March 13, 1981. State of Oregon.
3 Mines, J. and R. E. Favreau. Recirculating Sand Filter: An Alternative
to Traditional Sewage Absorption Systems. In: Proceedings of the
National Home Sewage Disposal Symposium, Chicago, Illinois,
December 1974. American Society of Agricultural Engineers, St.
Joseph, Michigan, 1975. pp. 130-136.
4 U. S. Environmental Protection Agency. 1979. Methods of Chemical
Analysis of Water and Wastes, "EPA-600/4-79-020, Environmental
Monitoring and Support Laboratory, Cincinnati, Ohio.
5 American Public Health Association. 1975. Standard methods for the
examination of water and wastewater. Prepared and published
jointly by: American Water Works Association, Water Pollution
Control Ferl»ration, and American Public Health Acsociatlon, 1740
Broadway, New York, N.Y.
** Johnsgard, G. A. 1953. Temperature and the Water Balance for Oregon
Weather Stations. Special Report 150. Oregon State University
Agricultural Experiment Station, Corvallis, Oregon, p. 44.
Law, J. P., Jr. Nutrient Removal from Enriched Waste Effluent by the
Hydroponic Culture of Cool Season Grasses. Rpt. to USDI-FWQA.
Program #16080—10/69. Washington, D.C.: U. S. Gov't. Printing
Office. October 1969.
8 Laak, R. 1970. Influence of Domestic Wastewater Pretreatment on Soil
Clogging. J. Water Pollution Control Federation, 42:1495-1500.
^ Laak, R. 1973. Wastewater Disposal Systems In Unsewered Areas. Final
Report to Connecticut Research Commission, Civil Engr. Dept.,
University of Conn. Storrs, Conn.
10 McGauhey, P- H. and R. B. Krone. 1967. Soil Mantle as a Wastewater
Treatment System. Final report. SERL Report No. 67-11. Sanitary
Engineering Research Laboratory, University of California,
Berkeley, California.
11 Thomas, R. E., W. A. Schwartz and T. W. Bendlxen. 1966. Soil Chemical
Changes and Infiltration Rate Reduction Under Sewage Spreading.
Soil Sc1. Soc. of Amer. Proc. 30-641-646.
2-18
(22)
-------
12 Wlnneberqer, J. H., L. Francis, S. A. Klein and P. H. McGauhey. 1960.
Biological Aspects of Failure of Septic-Tank Percolation Systems.
Final Report. Sanitary Engineering Research Laboratory, University
of California, Berkeley, California.
13 Wert, S. Performance of Soil Absorption Fields Following Sand Filters -
Two Case Studies. Unpublished Report. Roseburg, Oregon, 1980.
39 p.
14 Bouma, J. "Unsaturated Flow During Soil Treatment of Septic Tark
Effluent," J. Environ. Eng. Div., Am. Soc. Civ. Eng.,m 101, EE 6,
967-983, Dec. 1975.
15 Machmeier, R. E. "Design Criteria for Soil Treatment Systems," paper
presented at the American Society of Agricultural Engineers' Winter
Meeting, Chicato, 111., Dec. 15-18-1975.
16 Simpson, T. W. and R. L. Cunningham 1978. Soil Morphologic and
Hydraulic Changes Associated with Wastewater Irrigation. 2nst.
for Research on Land and Water Resources. Penn. State University.
XG867 2-19
(23)
-------
CHAPTER 3
INTERMITTENT SAND FILTER SYSTEMS
Intermittent sand filters were Installed and monitored under the same
conditions as reclrculatlng sand filters. Site limitations and affected
acreages were discussed previously (Chapter 2) This section reports on
Intermittent sand filter treatment of septic tank effluent prior to
discharge Into dlsposa1 trenches Installed either 1., soils shallow to
hardpans, claypans, '.aproHte, bedrock, and groundwater, or In soils with
permeability races either too rapid for adequate treatment or too slow for
adequate disposal.
METHODS
INTERMITTENT SAND FILTER DESIGN
Seven Intermittent sand filters were Installed 1n valleys and foothills of
Western Oregon. Three kinds of Intermittent sand filters were Installed,
using design characteristics 1n Table 3-1, to biologically and physically
treat septic tank effluent in 2 ft of medium sand similar to the sand that
was used 1n construction of Wisconsin mounds (1, 2) except at least 251 was
medium sand with a diameter of 0.25 to 0.50 mm with 251 or less finer than
0.25 mm. Effluent was applied from a pressure distribution system at an
application rate not to exceed 1.23 gal/ft/day (3).
The first sand filter unit Installed consisted of 2 cells contained
within a concrete container (Figure 3-1). A 4 1n. perforated underdraln
3-1
(25)
Preceding page blank
-------
«as pUced in the bottom of each cell and covered witii about 8 1n. of
3/4 in. *«hed gravel. Both cells were filled with 2 ft of medium sand
(Table 3-2).
TA3LE 3-1. DESIGN CHARACTERISTICS FOR INTERMITTENT SAND FILTERS1
Surface Area 366 ft-
Fliter Media Depth * 2 ft
Filter Media Medium Sand
25% 0.25-0.5
-255£-<0.25 mm
Filter Surface Burled b> Soil Covsr Yes
Maximum Design Loading Rate 1.23 gal/ft2/d
No. Tlmps t'fluent Applied to 1
Filler Before Discharge
No. Doses Per Day 2 to 5
No. Gal Dosed/ft2/Cyc1e 0.25-2.36 gal/ft2/d
No. Gal Applied/Dose 100-250 gal
Dosing Controls Volumetric;
mercury float
switches
* Characteristics shown are from a sand filter designed to process up to
450 gal septic tan* effluent per day.
TABLE 3-2. SANDS USED IN OREGON INTERMITTENT FILTERS
SAND CHARACTERISTICS
SYSTEM
1
2
3
4
5
6
7
(Gllkey)
'Toiles)
La Jo1e)
McCurley)
Prooras)
L1es1rtgerJ
LBoettcher)
EFFECTIVE
SIZE (mm)
0.25
0.20
0.26
0.28
0.30
0.30
0.14
UNIFORMITY
COEFFICIENT
3.1
2.1
4.0
3.2
1.5
5.0
3.1
DEPTH
(1n.)
24
24
24
24
24
24
30
3-2
(26)
-------
Perforated pressure distribution PVC piping was bedded 1n 3/4 to 2-1/2 1n.
washed gravel on top of the sand. Distribution piping was spaced 4 ft
apart with 1/8 1n. holes every 2 ft. Holes were oriented up. Pipe size
varied from 3/4 to 2-1/2 1n. diameter. The top of the filter was covered
with 12 to 18 1n. of silt loam, crowned, and seeded with grass to Increase
runoff, reduce Infiltration, provide frost protection, and make them
Inaccessible to the public and animals. The other 2 sand filter units were
similar except one consisted of a single cell 1n a concrete container
(Figure 3-2) and the other was placed 1n an unllned trench excavated 1oto
saprolite (Figure 3-3).
Filter systems were designed so that septic tank effluent was pumped from a
dosing tank to gravel filled beds or trenches through perforated distri-
bution piping (4). Two-celled units used a duplex pump system that
alternated application to each cell. The other 2 sand filter units used
a single pump. The quantity of effluent applied with each dosing event
ranged from 100 to 250 gal (Table 3-3). The design hydraulic loading
rate was 1.23 gal/ft2/d but actual hydraulic loading varied from 0.33 to
0.88 gal/ft2/d (Table 3-3).
Pressure distribution systems were designed to provide approximately 5 ft
of head at the remotest orifice of each lateral to prevent orifice
clogging. Septic tank effluent made only one pass through the sand bed
prior to discharge. Effluent processed by filtration through sand 1n a
concrete container was collected 1n the 4 1n. diameter underdraln and
discharged 1nti conventional disposal trenches 2 ft wide and 2 ft deep
3-3
(27)
-------
Sand Fitter
Disposal Field
Pressure Piping
4" Underdrain
\ X
FIGURE 3-1. DOUBLE CELLED INTERMITTENT SAND FILTER
-------
Pressure Piping-
4" Underdrain-
7"
ii
ill
ij
ij
t
FIGURE 3-2. SINGLE CELL INTERMITTENT SAND FILTER
-------
House
(Septic tank
'Dosing Tank
Pressure Piping
±
FIGURE 3-3. INTERMITTENT SAND FILTER PLACED IN SOILS SHALLOW TO SAPROLITE OR FRACTURED ROCK
-------
TABLE 3-3 INTERMITTENT SAND FILTER HYDRAULIC LOADING CHARACTERISTICS
HYDRAULIC LOADING
FILTER
SURFACE
SYSTEM AREA (ft2)
1 (Gllkey) 1.2
2 (Tolles)
3 (LaJole)
4 (McCurley)
5 (Grooms)
6 (L1es1nger)
7 (Boettcher)
2-100
2-2'c?
2-250
400
200
200
450
DESIGN
FLOW (qpd)
300
450
450
450
450
450
450
ACTUAL
FLOW (qpd)
113
228
166
191
139
350
194
DOSE DOSING
LOADING VOLUME RATE
RATE (gal/ft2/d) (qal/dose) (gal/fWdose)
0.57
0.51
0.33
0.48
0.35
0.88
0.43
236; 112
225
166
110
100
112
250
2.36;1.12
1.01
0.66
0.28
0.25
0.28
0.56
2 cells and had total areas of 200,
1 The Gllkey, Tolles and LaJole filters were divided Into
444, and 500 ft2 respectively.
2 After several months operation, dose volune on the Gllkey filter was adjusted from
236 gal/dose to 112 gal/dose.
XG868.A
-------
containing 4 in. diameter perforated plastic distribution piping bedded in
12 in. of gravel. Unlined filters had no underdrains. They discharged
treated effluent directly into saprolite and fractured rock materials.
MONITORING
Filters were monitored to determine their mechanical operation and
maintenance ^eeds as well as their capacity to treat septic tank effluent.
Effluent samples were collected and analyzed for BODg, SS, N03, N02» NH3,
total kjeldahl nitrogen (TKN), total nitrogen (TN), fecal coliform (FC),
and total colifonfi (TC). Nitrate + nitrite-nitrogen was determined by the
hydrazine reduction method, nitrite-nitrogen was determined through
automated analysis by technicon, ammonia-nitrogen was determined by the
phenate colorimeteric method, and total kjeldahl-nitrogen samples were
digested in a technicon block digester and analyzed by the automated
phenate method (5). Suspended solids were determined using U. S. EPA
methods for chemical analyses of water and wastes (5). BOD was determined
D
by the Modified Winkler method and fecal and total conforms were
determined using the membrane filter method (6).
RESULTS AND DISCUSSION
OPERATION /.NO MAINTENANCE
Intermittent filters operated reliably throughout the 5-49 month period
they were studied. No filter required maintenance.
Five filters (Table 3-4) were excavated to the sand-gravel interface after
several months use to determine 1f a biological mat had formed. No odor,
evidence of biomat formation, or effluent ponding was apparent.
3-8
(32)
-------
TABLE 3-4. SAND CHARACTERISTICS, LOADING WES, AND SELECTED SEPTIC TANK EFFLUENT
CHARACTERISTICS OF 5 INTERMITTENT SAND FILTERS
SAND CHARACTERISTICS
SELECTED
SEPTIC TANK EFFLUENT CHARACTERISTICS1
MONTHS
SYSTEM USED
WHEN
SYSTEM EXAMINED
1 (Gllkey)
3 (La Joie)?
4 (McCurley)
5 (Grooms)
6 (Boettcher)
16
29
4
17
52
EFFECTIVE
SIZE
0.
0.
0.
0.
0.
(mm)
27
26
28
30
14
UNIFORMITY
COEFFICIENT
2
4
3
1
3
.6
.0
.2
.5
.1
AVERAGE
LOADING
RATE (g/d/ft2) BODs
0
0
0
0
0
.57
.33
.48
.70
.43
197
(ID3
—
149
(8)
188
(7)
222
(ID
SS
38
(ID
—
240
(8)
79
(7)
193
(11)
FC
1.1 x 105
(10)
—
2.0 x 104
(10)
7.0 x 104
(6)
- —
TC
1.8 x 106
(9)
—
1.5 x 105
(8)
7.7 x 104
(5)
— _ —
1 Septic tank effluent 8005 and SS values expressed as arithmetic mean. Bacterial values
expressed as geometric mean.
2 No samples of septic tank effluent were analyzed at the La Joie system.
3 Number of Samples.
X6868.B
-------
'*?fr<^ *
All pumps, dosing contro'lSj, and alarm systems functioned .-roperly.
However, equipment repair and replacement will be required periodically
because of wear on submersible effluent pumps and the corrosive action of
effluent on electrical controls. Septic tanks will also require regular
periodic pumping to prevent overflow of solids into the filter sand.
SAND FILTER EFFLUENT QUALIT/
Intermittent sand filters reduced BOD more than 98% and SS more than 93%
(Table 3-5). Suspended solids treatment was actually much better than
these data indicate because sampling techniques contaminated effluent
with sediment. Effluent samples at System 2 (Table 3-7) were collected
from a drop structure following the sand filter. Most of these samples
were taken when the filter was not discharging effluent. Consequently,
grab samples were not taken from a flowing stream of effluent but from
the drop structure. Effluent levels "ere low enough so that sediment
was resuspended into the sample from the bottom of the drop structure
during the sampling process. This resulted in SS concentrations as high
as 200 mg/1. Five samples were collected when this sand filter was
discharging effluent into the drop structure. The effluent was clear and
the SS were less than 1 mg/1.
Effluent samples were collected from a "tee" placed in a depression 1n the
line from Systsm 4 (Table 3-7). A manually operated vacuum pump was used
to obtain effluent samples. Effluent within the sampling structure was
always clear before sampling, but sediment was easily detached and sucked
Into sampling containers during the sampling process. This caused mean
3-10
(34)
-------
TABLE 3-5, A COMPARISON BETWEEN SINGLE FAMILY RESIDENTIAL SEPTIC TANK
AND IN7FRMITTENT SAND FILTER EFFLUENTS1
ECFLUENT
CHARACTERISTIC
B005
SS
N02
N03
Nh3
TKN
TN
FC
TC
Number
Systems
SEPTIC2
TANK
EFFLUEMT
217
(70)3
1*6
(70)
0.02
(57)
0.4
(59)
40.6
(60)
57.1
(57)
57.5
(54)
2.6 x 1C5
(56)
1.32 x 106
(46)
8
INTERMITTENT
SAND FILTER
EFFLUENT
3.2
(84)
9.6
(83)
0.04
(50)
29.1
(53)
0.25
(52)
1.7
(50)
30.3
(50)
407
(93)
1.84 x 104
(39)
7
%
CHANGE
99
93
50
99
99
97
47
99
(3 logs)
99
(2 logs)
* 6005, SS and nitrogen expressed as mg/1; arithmetic mean. Fecal and
total coliform expressed as org/100 ml; geometric mean.
2 Arithmetic mean of 8 systems (Table 3-6).
3 Number of samples.
SS concentrations considerably higher than they actually were 1n filtered
effluent.
Susoended sol Ids data from System 1 and System 3 provided a much better
Indication of filter treatment capacity. These systems were sampled from
3-11
(35)
-------
TABLE 3-6. QftTACTERISTICS OF 8 OREGON SINGLE FAMILY RESIDENTIAL SEPTIC TWK EFFLUENTS
SEPTIC TWK EFFUW QffiACTERISTICS1
AVE.
FUDW
SYSTEM (gpd) BO^
McCurley
Gilkey
Groans
Boettcher
Reber
HcClaflin
Roberts
Anderson
Weighted
M
113
139
194
176
161
174
__
164
Arithretic(7)
Average
149,
(8)2
197
(11)
188
(7)
222
(11)
378
(7)
125
(16)
348
(7)
322
(3)
217
(70)
SS
240
18)
38
(ID
79
(7)
193
(11)
276
(7)
91.7
(16)
171
(7)
203
(3)
146
(70)
*°3
0.18
(9)
0.81
(10)
O.U4
(7)
«.
m«
(6)
0.56
(16)
0.38
(8)
0.24
(3)
0.4
(59)
N02
0.02
(9)
0.02
(10)
0.0?
(6)
_
0.02
(7)
0.02
(15)
0.02
(7)
0.02
(3)
0.02
(57)
"b
37.8
(9)
35
(10)
35.5
(7)
..
53.3
(7)
36.1
(16)
55.9
(8)
32.55
(3)
40.6
(60)
TKN
55.9
(9)
58.4
(10)
45.6
(7)
_
83.6
(7)
51.26
(16)
70.5
(7)
47.2
(2)
58.7
(58)
TO
57.1
(9)
59.23
(10)
45.66
(6)
_
83.8
(6)
51.84
(15)
70.9
(7)
47.46
(2)
59.1
(55)
FC
2.0 xlO4
1.1
7.0
5.4
8.0
1.0
8.1
2.6
(10)
xlO5
(10)
xlO4
(6)
_
xlO5
(6)
xlO4
(14)
xlO5
(8)
xlO4
(2)
xlO5
(56)
T*»
1.5 x 1C5
(8)
1.8 x 10s
(9)
7.7 x 105
(5)
_
2.1 x 106
(6)
9.9 x 105
(10)
2.5 x 106
(6)
1.3 x 1C6
(2)
1.32 x 1C5
(46)
1 80)5, SS, and nitrogen expressed as mg/1; arltlratic nean. Fecal and total
colifonn expressed 6s org/100 ml; geonetrlc mean
2 Nutter of saiples.
drop structures similar to the one used for sampling System 2, but effluent
liquid depths in these drop boxes were high enough to prevent significant
sediment disturbance. Thus, little contamination of samples with suspended
matter occurred.
3-12
(36)
-------
TABLE 3-7. A COMPARISON BETWEEN INTERMITTENT SAND FILTER EFFLUENTS
EFFLUENT CHARACTERISTICS
AVE.
FLOW
SYSTEM (gpd) 8005!
3
1 (Gllkey)
2 (Tolles)
3 (LaJoie)
4 (McCurley)
Weighted
Arithmetic
Average
113
228
218
191
205
(7)
3
(21)4
2.7
(21)
2.7
(30)
6.4
(11)
3.2
(84)
SS
2.2
(21)
15.4
(21)
4
(30)
28
(11)
9.6
(83)
N03
40.96
(12)
25.3
(14)
25.94
(11)
28.8
(12)
29.1
(53)
N02
0.04
(12)
0.02
(14)
0.06
(11)
0.08
(12)
0.04
(50)
NH3
0.2
(11)
0.13
(13)
0.12
(11)
0.7
(12)
0.25
(52)
TKN
C.6
(12)
1.0
(13)
0.7
(11)
1.6
(12)
1.7
(50)
TN
41.6
(12)
26.5
(13)
26.7
(11)
31.2
(12)
30.3
(50)
FC2
537
(20)
94
(28)
790
(30)
30
(13)
407
193)
TC
4.0 x 10
(10)
2.8 x 103
(6)
3.2 x 104
(9)
784
(12)
1.84 x 104
(39)
1 8005, suspended solids and nutrients expressed as mg/1; arithmetic mean.
2 Total and fecal conform bacteria expressed as org/100 ml; geometric mean.
3 Mean and weighted arithmetic average values shown for the Gil key system reflect
effluent data collected at 2 dosing rates; 1.12 and 2.36 gal/ft2/dose.
4 Number of samples.
Sand filtration reduced total nitrogen by 47*. Ninety-six percent of
the nitrogen in sand filter effluent, was 1n an oxidized form compared to
less than 1% in septic tank effluent (Tables 3-5 and 3-6). Results
suggested septic tank effluent underwent 2 distinct stages of trans-
formation. First, most organically bound nitrogen was rapidly broken down
and oxidized along with ammonia as septic tank effluent passed through the
first few inches of filter sands. Denitrif1cat1on probably occurred 1n
anaerobic mlcrosites either in moisture films on sand grairn and at points
3-13
(37)
-------
of sand grain contacts or In the zone of near saturation just above the
sand-gravel Interface or sand-saprolite Interface.
Magdoff, Keeney, Bouma and Ziebell (7) suggested denltriflcation occurred
within intermittent filter sands immediately above the sand-gravel
Interface. They reported accumulations of organic nitrogen in treatment
sands just above gravel layers in their column studies.
Some denitriflcation may have resulted from the activities of facultative
anaerobes which occupied oxygen deficient microsites in moisture films on
and at sand grain contacts. Winneberger (8) suggested this mechanism was
responsible for considerable denitrification.
Denitrification may also have occurred as a result of intermittent dosing
and resting. Patrick and Reddy (9, 10) reported rapid breakdown of crganic
matter and the loss of fixed nitrogen by denitrification in soils which
were subjected to cycles of anaerobic and aerobic conditions every 6-12
hours. Intermittent filters receiving 2-4 doses of septic tank efflaent
per day would i.ave 6-12 hour aerobic resting intervals between dosing
events.
Total nitrogen losses similar to those shown 1n Intermittent filter
effluents were also noted by mound Investigators (11). However, filter
nitrogen losses were higher than reductions reported by researchers who
conducted gray water sand filter and soil column studies (12, 13).
3-14
(38)
-------
Intermittent sand filters reduced f
-------
Comparable effluent samples were not collected at Systems 5, 6, and 7
because these are bottomless sand filters placed 1n an unllned trench
excavated Into saprollte (Figure 3-3).
DISPOSAL FIELD PERFORMANCE
Intermittent sand filter effluent from Systems 1, 2, 3, and 4 was dis-
charged Into 2 ft deep, 2 ft wide soil absorption trenches which contained
4 1n. diameter perforated plastic distribution piping bedded 1n 12 1n.
washed gravel. Filtered effluent from Systems 5, 6, and 7 was discharged
directly Into saprollte or fractured basalt material Immediately below
filter sands.
T«Me 3-9 summarizes site conditions, design characteristics, and
performance of trench soil absorption systems. Disposal trenches following
Systems 1, 2, and 3 were placed 1n soils severely limited by shallowness to
weathered rock or groundwater. In spite of these unfavorable conditions,
disposal fields at these locations functioned satisfactorily. The disposal
field for System 4 also functioned properly, but was Installed 1n soils
suitable for a standard soil absorption syst«n.
During dry summer months, all effluent was absorbed by the first disposal
trench following System 1 and System 2. However, during wet winter and
spring months, the upper trench of these two systems Intercepted a small
amount of groundwater.
Effluent absorption patterns were less easy to determine at System 3 and
System 4 because both filters discharged to equal distribution systems.
3-16
(40)
-------
WIU 3-9. A WSOtlPTIW OF Sin CWDITIOHS, 30IL ABSCRPTIOH TRCNOCS. AW WOO rWFCPmCI AT 4 [KTEWITTOrT SAW f lira JYSTOI LOCAMOW
SYSTtN
FEATUW ttSCHIBED
Soil Absorption
S«ta» SHe
Italtatlon
Soil Texture it
Absorption Trench
SldeMll
Slop* («)
Average Drj Infield
loading Rate (gpd)
Trench Type, Length.!
andSldeSill ,
Absorption Aret (ft?)
Average Dally Trench
Slde.aU Loading Rite
(a/ft"/d)
Average Percent Systaa*
SI dew 1) Used for
Absorbing Effluent
Trench InsUllatlon Date
Obunritlon Period
Nurtcr of Obsenratlom
1 (GIUtT)
14-19 In. toll over
wtthered granite
14-19 In. city lo«
over withered
granite
a
it]
3-tertil trenchet
190 Hn, ft
(380)
7.7
3.S
April 1977
Dec. 1977-Mty 1980
Zt
! (TOUtS)
»Honi1 atwidMter;
•Jttllng ; during high precipitation «onths at the Sllkey and HcCurley sites.
K86B.O
-------
TABLE 3-10. THE RELATIONSHIP BETWEEN GROUNDWATER LEVELS AND WATER LEVELS
OBSERVED IN DISPOSAL TRENCHES FOLLOWING THE LA JOIE SAND FILTER
FROM MAY 1977 - MAY 1980 ,
DISTANCE FROM 3
GROUNDWATER TO
WATER ABOVE TRENCH BOTTOM (In.)1'2 GROUND SURFACE
OBSERVATION ~ ' IN MONITORING
DATE TRENCH 1 TRENCH 2 TRENCH 3 TRENCH 4 WELL (i.->.)
M
A
Y
/
0
C
T
0
B
E
R
N
0
V
E
M
B
E
R
/
A
P
R
I
L
May 23, 1977
June 6, 1977
June 20, 1977
July 11, 1977
Aug. 8, 1977
Oct. 4, 1977
May 22, 1978
June 12, 1978
July 18, 1978
Aug. 14, 1978
Sept. 19, 1978
Aug. 29, 1979
May 20, 1980
Nov. 1, 1977
Jan. 15, 1978
Feb. 14, 1978
Feb. 21, 1978
March 14, 1978
April 18, 1978
Dec. 12, 1978
Jan. 23, 1978
Feb. 27, 1979
Jan. 17, 1980
Feb. 24, 1980
Mzrch 19, 1980
April 1, 1980
2
2
2
2
2
3
2
dry
1
2
3
dry
4
4
21
17
18
18
9
2
14
7
7
7
11
13
1
2
2
2
2
2
1
dry
1
1
2
dry
2
2
22
16
17
18
9
dry
12
6
7
7
11
12
3
4
1
3
2
2
1
dry
1
1
3
dry
2
2
19
16
16
14
8
1
12
7
7
6
9
12
1
2
1
1
1
1
1
dry
1
1
2
dry
1
2
19
15
17
14
8
dry
12
7
7
6
9
12
24
25
26
26
26
24
25
dry
26
dry
dry
dry
«•— —
dry
7
11
12
15
19
dry
14
18
16
• •M>
•»_~
1 Trenches were 24 1n. wide, and 24-27 1n. deep. They contained 4 1n.
diameter perforated plastic piping bedded 1n 12 1n. washed gravel.
Gravel was backfilled with 12-15 1n. topsoll.
2 Slight variations 1n water depths were reported since measurements were
not always made from the same position of monitoring wells each time
monitoring took place and there was a small difference 1n surface
elevation at well edges due to differential soil settlement.
3 The outside monitoring well was a 4 1n. diameter, 28 1n. long plastic pipe.
Ground surface elevation at the monitoring well was approximately 2 1n. lower
than average trench well elevations.
3-18
(42)
-------
No effluent was observed in disposal trenches at System 4 but effluent was
ponded in disposal trenches at System 3 during the wet winter and spring
months when temporary groundwater inundated trenches (Table 3-10).
The treatment of septic tank effluent by sand filtration substantially
reduced the rate of soil biomat formation. Although Investigators
disagree on which causative agent plays the most active role 1n biomat
development, they all agree that BOD , SS, and fecal bacterial organisms,
are the main factors responsible (15, 16, 17, 18, 19). The first disposal
trench of System 3 was unearthed 1n February 1980, after 34 months use. No
biomat had formed at the trench's bottom or sidewalls even though that
trench's 1nfiltrat1ve surface had been partially or completely inundated by
groundwater for several months each year (Table 3-10) and trenches had
received an average of 218 gal of sand-filtered effluent per day (Table
3-7). When BOD , SS and fecal bacteria were reduced by Intermittent sand
filtration, soil absorbtion trench effluent infiltration rates remain high
(Table 3-11). Examination of disposal trenches following these sand
filters suggested that higher absorption rates occurred because blomats
were absent. These rates were considerably higher than rates reported (20,
21, 22) for septic tank effluent (Table 3-11).
CONCLUSIONS
Intermittent sand filter beds required no maintenance during the monitoring
period. All pumps, dosing controls, and alarm systems functioned properly
but periodic maintenance and repair will no doubt be required.
3-19
(43)
-------
TABLE 3-il. A COMPARISON BETWEEN INTERMITTENT SAND FILTER SOIL ABSORPTION
TRENCH EFFLUENT ACCEPTANCE RATES AND RECOMMENDED SEPTIC TANK
EFFLUENT LOADING RATES
FILTERED*
RECOMMENDED SEPTIC TANK2.3
SYSTEM
1 (611 key)
2 (Tolles)
3 (La Jo1e)
4 (McCurley)
SOIL
TEXTURE
clay loam over
weathered granite
silt loam
slightly salt cemented
sandy loam
sandy loam
EFFLUENT ACCEPTANCE
RATE (g/d/ft2)
7.7
2.8
2.3
too rapid to determine
EFFLUENT
BOUMA
0.72
0.72
0.72
0.72
LOADING RATE (g/d/ft2)
MACHMEIER
0.5
0.5
0.6
0.6
1 Based on sldewall area.
2 Adapted from Table 7-2, EPA Design Manual; Onsite Wastewater Treatment and Disposal Systems.
3 Based on bottom area; may be suitable estimates for sldewall Infiltration rates.
XG837
-------
BOOj, SS, and total nitrogen were reduced 98X, 93%, and 49X respectively.
Results for suspended solids were abnormally high because of sampling
difficulties. Den1tr1f1cat1on probably occurred 1n anaerobic moisture
films around sand grains and at points of sand grain contact and 1n the
zone of near saturation just above the sand-gravel Interface.
Total and fecal col 1 form organisms were about one log lower than they were
1n redrculatlng sand filter effluent. Total and fecal coHform reduction
was directly related to hydraulic loading rate 1n one system.
All soil absorption systems functioned properly 1n spite of the fact that 3
were Installed 1n soils severely limited by shallow depth to saprollte or
high groundwater.
Blomat formation was not a problem and sand filter absorption rates were
considerably higher than those commonly reported for septic tank effluent.
3-21
(45)
-------
REFERENCES
1 Converse, J. C., R. J. Otis and J. Bouma. 1975a. Design and
Construction Procedures for Mounds 1n Slowly Permeable Soils
With and Without Seasonally High Water Tables. Small Scale
Waste Management Project., 1 Agricultur Hall, University of
Wisconsin, Madison WI.
2 Converse, J. C., R. J. Otis and J. Bounia. 1975b. Design and
Construction Procedures for Fill Systems in Permeable Soils
With Shallow Creviced Bedrock. Small Scale Waste Management
Project., 1 Agriculture Hall, University of Wisconsin,
Madison WI.
3 Bouma, J., W. A. Ziebell, W. G. Walker, P. 6. Olcott, E. McCoy and
F. D. Hale. 1972. Soil Absorption of Septic Tank
Effluent. Information Circular No. 20. University of
Wisconsin-Extension. Geological and Natural History
Survey. 235 p.
n
* J. C. Converse, J. L. Anderson, W. A. Ziebeli, and J. Bouma,
"Pressure Distribution to Improve Soil Absorption Systems,"
Home Sewage Disposal, Proc. Am. Soc. Ag. Eng., Dec. 1974. pp
104-115.
5 U. S. Environmental Protection Agency. 1979. Methods of Chemical
Analysis of Water and Wastes, EPA-600/4-79-020,
Environmental Monitoring ard Support Laboratory, Cincinnati,
Ohio.
6 American Public Health Association. 1975. Standard Methods for the
Examination of Water and Wastewater. Prepared and published
jointly by: American Water Works Association, Water
Pollution Control Federation,, and American Public Health
Association, 1740 Broadway, New York, N.Y.
7 Magdoff, F. R., D. R. Keeney, J. Bouma, and W. A. Ziebell. 1974.
Columns Representing Mound-type Disposal Systems for Septic
Tank Effluent. II. Nutrient Transformations and Bacterial
Populations. J. Environ. Quality. 3(3):228-234.
8 Winneberger, J. T. Predicted Effects of the Proposed Subdivision
of Stumpy Meadows at Lake Edson, El Dorado County,
California. 2nd Rpt. Preliminary Issue. Berkeley,
Calif.: Office of Winneberger, Consultant. 3 April 1970.
9 Patrick, W. H. and K. R. Reddy. 1974. Effect of Alternate Aerobic
and Anaerobic Conditions on Redox Potential, Organic Matter
Decomposition and Nitrogen Loss in a Flooded Soil. J. Soil
B1ol. Fjiochem. 7:87-94.
3-22
(46)
-------
1° Patrick, W. H. and K. R. Reddy. 1976. Effect of Frequent Changes
in Aerobic and Anaerobic Conditions on Redox Potential and
Nitrogen Loss in a Flooded Soil. J. Soil Biol. Biochem.
8:491-495.
H Harkin.J. M., C. J. Fitzgerald, C. P. Duffy, and D. 6. Knoll.
1979. Evaluation of Mound Systems for Purification of Septic
T^nk Effluent. WIC WRC 79-05. Water Resources Center,
University of Wisconsin, Madison, Wis. p. 87.
12 Siegrist, R. L., W. C. Boyle, D. L. Anderson. 1981. A Field
Evaluation of Selected Water Conservation and Waste Water
Reduction Systems for Residential Applications. WIS WRC 81-
02. Water Resources Center, University of Wisconsin, Madison,
Wis. p. 96.
13 Magdoff, F- R. and D. R. Keeney. 1976. Nutrient Mass Balance in
Columns Representing Fill Systems for Disposal of Septic Tank
Effluents. Environ. Letts. 10:285-294.
14 Bouma, J., W. A. Ziebell, W. G. Walker, P. G. Olcott, E. McCoy and
F. D. Hole. 1972,, Soil Absorption of Septic Tank Effluent—
A Field Study of Some Major Wisconsin Soils. Univ. of
Wisconsin Extension Info. Circ. No. 20, Madison, WI, 235 pp.
15 Laak, R. 1970. Influence of Domestic Wastewater Pretreatment on
Soil Clogging. J. Water Pollution Control Federation, 42:1495-
1500.
16 Laak, R. 1973. Wastewater Disposal Systems in Unsewered Areas.
Final Report to Connecticut Research Commission, Civil Engr.
Dept., University of Conn. Storrs, Conn.
I7 McGauhey, P. H. and R. B. Krone. 1967. Soil Mantle as a
Wastewater Treatment System. Final report. SERL Report No.
67-11. Sanitary Engineering Research Laboratory, University
of California, Berkeley, California.
18 Thomas, R. E., W. A. Schwartz and T. W. Bendixen. 1966. Soil
Chemical Changes and Infiltration Rate Reduction Under Sewage
Spreading. Soil Sci. Soc. of Arner. Proc. 30-641-646.
19 Winr^berger, J, H., L. Francis, S. A. Klein and P. H. McGauhey.
1960. Biological Aspects of Failure of Septic-Tank
Percolation Systems. Final report. Sanitary Engineering
research Laboratory, University of California, Berkeley,
California.
3-23
(47)
-------
20 Design Manual, Onslte Wastewater Treatment and Disposal Systems.
USEPA Municipal Environmental Research Laboratory, Cincinnati,
Ohio, December 1980, p. 214.
21 Macnmeler, R. E. Town and Country Sewage Treatment. Bulletin 304,
University of Minnesota, St. Paul, Agricultural Extension
Service, 1979.
22 Otis, R. J.v G. D. Plews, and 0. K. Patterson. Design of
Conventional Soil Absorption Trenches and Beds. In;
Proceedings of the Second National Home Sewage Treatment
Symposium, Chicago, Illinois, December 1977. American Society
of Agricultural Engineers, St. Joseph, Michigan, 1978.
pp. 86-99.
X6868 3_24
(48)
-------
#3
CHAPTER 4
INTERMITTENT RECIRCULATING SAND FILTER SYSTEMS
Intermittent recircu'lating sand filters were installed and monitored under
the same conditions as recirculating sand filters. Site limitations and
affected acreages were discussed in Chapter 2. This chapter reports on
intermittent-recirculating sand filter treatment of septic tank effluent
prior to discharge into disposal trenches installed either 1n sells shallow
to hardpans, claypans, saprolite, bedrock, and groundwater, or in soils
with permeability rates either too rapid for adequate treatment or too slow
for adequate disposal.
METHODS
SYSTEM DESIGN
Intermittent recirculating sand filter systems were installed at 8 single
family residences (Systems 1-8) and a small sawmill-office building complex
(System 9). Installations were made at valley and valley foothill
locations between Western Oregon's Coast and Cascade mountain ranges.
The first 3 intermittent recirculating sand filter systems (Systems 6 to 8)
were installed in Lane County under repair permits (1). Tuey were
installed to replace failing (surfacing) disposal fields. The original
Intermittent recirculating sand filter was designed by Gary Colwell and
Craig Star*-, 2 Lane County Department of Environmental Management Staff
Engineers (2). The filter was later patented by a private Oregon
investment company (3).
4-1
(49)
-------
TABLE 4-1. DESIGN CRITERIA FOR INTERMITTENT RECIRCULATING SAND FILTERS1
Filter Media
Septic Tank Effluent
Absorption System
Distribution Technique
Absorption Trench2
Infiltrative Surface Area
Depth Filter Sand
Below STE Absorption
Trenches
Recirculation Systun
Distribution Technique
Infiltrative Surface Area
Depth Sand Bslow Infiltrative
Surface
Infiltrative Surface Open to
Atmosphere
Design Loading Rate
Dose Volume
Dosing Rate
Doling Frequency
Times Effluent Redrculated
Before Discharge
Dosing Controls
medium sand
25% 0,25-0.50 rrni
0.25 m
2-gravity fed. 10 ft long, 12 in. wide
18 in. deep absorption trenches
containing 4 in. perforated
distribution piping bed in a
12 in. layer of washed gravel
64 ft2
24 in.
4-quarter circle pattern shrub
spray heads located at filter
corners
144 ft2
42 in.
Yes
3.125 gal/ft2 1nfiltrat1ve surface/d
15-25 ga*
0.1 - 0.17 gal/ft2/dose
48 doses/day
3-4 m1n
percentage timer and free
floating mercury switches
1 Characteristics shown are for a residential sand filter designed to
process up to 450 gal wsstewater per day.
2
Infiltrative surface includes trench bottom, sidewall, and end areas.
X6897
4-2
(SO)
-------
-Disposal Field
0
t**Sf:?JK'
^P>
'W&
'•••: vi"
Wooden Fence-
Circle Shrub Spray Heads—-
O
4" Underlain
Distribution Piping —
FIGURE 4-1. INTERMITTENT RECIRCULATING SANU FILTER
-------
TABLE 4-2. INTERMITTENT RECIRCULATING SAND FILTER CONSTRUCTION DETAILS
FILTER SAND CHARACTERISTICS
SEPTIC TANK EFFLUENT
ABSORPTION TRENCH CHARACTERISTICS
EFFECTIVE
SYSTEM SIZE (mm)
1
2
3
4
5
6
7
8
9
(Turner)
(Roberts)
(McClaflin)
(Reber)
(Grooms)
(Chester)
(Matteson)
(Steidley)
(Irf -rnational Paper4
"i yoration)
0.2
0.?7
0.3
0.3
0.3
0.28
0.28
0.?8
UNIFORMITY
COEFFICIENT
2.
2.
3.
1.
1.
3.
3.
2.
—
5
0
2
5
5
6
6
2
-
NO.
FILTER DIMENSION1 TRENCHES
14'x14
12'xl2
12'xl2
14'x14
12'xl2
12'xl2
12'xl2
12'xl2
26'x26
•x3'-6"
•x3'-6"
•x3'-6"
'x3'-6°
'x.V-6"
•x3'-G"
•x3'-6"
•x3'-fi"
'x4'-10"
3
2
2
4
2
2
2
2
2
LENGTH
(ft)
12
10
10
12
10
10
10
TO
24
WIDTH
(in.)
12
12
12
12
12
8
8
8
54
OEPTH?
(in.)
18
IS
18
)8
18
16
16
16
16
NO.3
SPRAYHEADS
4
4
4
4
4
4
4
4
9
Measurements represented Indicate the dimension inside filter containers occupied by treatment media.
Trenches 1n Systems 1-5 contained 12 in. of washed gravel. Trenches in Systems 6-9 contained 10-12 in. of washed gravel.
One full circle, 4-quarter circle and 4-half circle pattern spray heads were used at the International Paper Corporation
sand filter.
Sands useu in the International Daper Corporation sand filter were similar to those used In the Chester, Matteson,
and Steidley filters.
XG1520
-------
Design criteria for a typical residential Intermittent recirculat ing sand
filter are shown In Table 4-1. Septic tank effluert entered filters
through shallow, gravity fed subsurface infiltration trenches tedded 1n
filter sands (Figure 4-1).* [ffluent passed through 24 1r. of filter sand
Into a 4 In. perforated plistic uncerdrain pipe bedded 1n a layer of washed
gravel, and drained to the recIrculatlon tank. Filter system treatment
sand and trench characteristics are shown 1n Table 4-2. Filters serving
residences with 3 or fewer bedrooms contained 2 Infiltration trenches.
Systems 2 and 4. hj,1 3 and 4 trrnc^rs rf><,prc t i vpl y beoJus» they were
connected to larger hores with higher design flows.
Each half hour, 15 to 25 gal of filter effluent were pumped from the
recirculatlon tank to the open Piter surface via 4 quarter-pattern shrub
spray heads located 1n filter corners.** Redrcul atloi cycles lasted 5
minutes.
A 25 minjte resting
-------
through the open filter surface, 1t passed downward through at least
42 In. of treatment sand and 12 In. of underdraln gravel. .» 6 1n. high
concrete partition extended from the bottom of Filters 1, 3, 4, and 5
so 3/4 of the effluent returned to the redrculatlon tank for additional
application to the filter. System 9 was similarly divided so that 2/3 of
the effluent returned to the reclrculatlon tank. A second underdraln on
the opposite side of the partition drained filtrate to soil absorption
trenches. Systens 6, 7, and 8 had a single underdraln which conveyed all
filter effluent back to the redrculatlon tank. An outlet at the end of
the tank regulated the volume of effluent discharged to soil absorption
trenches. The amount of effluent discharged during a particular time
period was equivalent to the quantity of wastewater end any Incident
precipitation that fell onto the filter during that time Interval.
All Internment reclrculatlng sand filters except System 9 and System 3
were enclosed 1n 4 ft high wood frame fences to prevent the entry of
children and animals and help confine spray to the filter area. System 9
was 1n a roofed, wood-frame structure, and a fence was never constructed
around System 3.
MONITOR IMG
Filters were monitored to determine thslr mechanical operation and
maintenance needs as well as their capacity to treat septic-tank effluent.
Effluent samples were collected and analyzed for BOO . SS, WL , NO , NH ,
total kjeldahl nitrogen (TKN), total nitrogen (TN), fecal collforw (FC),
and total collforw (TC). Nitrate * n1trite-nitrogen was determined
by the hydrazlne reduction method, nitrite-nitrogen was determined through
4-6
(54)
-------
automated analysis by technlcon, ammonia-nitrogen was determined by the
phenate colorlmeterlc method, and total kjeldahl-nltrogen samples were
digested In a technlcon block digester and analyzed by the automated
phenate method (4). Suspended solids were determined using U. S. EPA
methods for chemical analyses of water and wastes (4). 30D was determined
by the Modified Wlnkler method and fecal and total conforms were
determined using the membrane filter method (5).
RESULTS AND DISCUSSION
HYDRAULIC LOADING
o
Residential filters were loaded at an average rate of 1.12 gal/ft /d, 36X
of their design rate (Table 4-3). The Industrial filter received an
2
average of 4.44 gal/ft /d, 1.42 times Its design loading rate. That filter
occasionally received loads as high as 10,000 gpd (data not shown), 4.73
times Its peak design flow (3).
SAND FILTER EFFLUENT QUALITY
Sand filtration decreased BOD 5 and SS S8X, total nitrogen 39t, and fecal
and total conforms 4 logs (Table 4-4). In residential filter effluent,
98.61 of the nitrogen was 1n a nitrate form compared to IX 1n septic tank
effluent.
Nitrogen content In effluent from System 7 was much higher than nitrogen
levels 1n other residential filter effluents. Hastewater received by
System 7 was produced by a limited number of fixtures (toilet, shower.
4-7
(55)
-------
bathroom lavatory, and kitchen sink) used by an elderly woman visited
occasionally by two sons.
Shortly after seasonal rainfall started, considerable groundwater
infiltrated into the septic tank or sewer lines preceding System 8. This
diluted septic tank effluent and interfered with filter treatment.
For the reasons cited, filter nitrate data from System 7 and effluent data
for all parameters from System 8 were excluded from weighted residential
filter averages indicated in Tables 4-4 and 4-6.
TABLE 4-3. AVERAGE DAILY LOADING RATES FOR 6 INTERMITTENT RECIRCULATING
SAND FILTERS
1
2
3
4
5
6
7
8
9
SYSTEM
(Turner)
(Roberts)
(McClaflin)
(Reber)
(Grooms)
(Chester)1
(Matteson)
(Steidley)
(International
Corporation)
EXPOSED
FILTER
SURFACE AREA (ft2)
196
144
144
1%
144
144
144
144
Paper 676
AVERAGE
DAILY
FLOW (g)
278
174
161
176
139
—
—
.—
3,000
LOADING
RATE
(q/ft2/d)
1.42
1.20
1.12
0.90
0.97
—
— _
...
4.44
No flow data was collected from Systems 6, 7, and 8 (Chester, Matteson,
and Steidley). Lane County repair permit provisions did not require flow
measuring devices.
4-8
(56)
-------
Total nitrogen In residential sand filter effluent fluctuated 11%
seasonally (Table 4-7). Total nitrogen Concentrations averaged 32.4 mg/1
in cool, moist months and 36.4 mg/1 during warm, dry months. Similar
nitrate nitrogen fluctuations (31.8 mg/1 November to April and 35.4 mg/1
May through October) were observed during wet and dry seasons.
TABLE 4-4. A COMPARISON BETWEEN SINGLE FAMILY RESIDENTIAL SEPTIC TANK AND
INTERMITTENT RECIRCULATING SAND FILTER EFFLUENTS1
EFFLUENT
CHARACTERISTIC
BOD5
SS
N02
N03
NH3
TKN
TN
FC
TC
SEPTIC2
TANK
EFFLUENT
217
(70) 4
146
(70)
0.02
(57)
0.4
(59)
40.6
(60)
57.1
(57)
57.5
(54)
2.6 x 105
(56)
1.32 x 105
(46)
INTERMITTENT3
RECIRCULATING
SAND FILTER EFFLUENT
3.4
(56)
3.4
(100)
0.06
(38)
33.8
(45)
0.36
(36)
1.1
(35)
34.9
(45)
54.0
(112)
628
(94)
%
CHANGE
98
98
67
99
99
98
39
99
(4 logs)
99
(4 logs)
* 6005, SS and nitrogen expressed as mg/1; arithmetic mean. Fecal and
total coliform expressed as org/100 ml; geometric me^n.
2 Arithmetic mean of 8 systems (Table 4-5).
3 Arithmetic mean of 7 systems (Table 4-6).
4 Number of samples.
4-9
(57)
-------
TPBLE 4-5. CHARACTERISTICS CF 8 OREGON SINGLE FAMILY RESIDENTIAL SEPTIC TAJK EFFLUENTS1
SEPTIC TATK EFFLUENT CHARACTERISTICS
AVE.
FLOW
SYSTEM (gpd)
2 (Roberts)
3 (toClaflin)
4 (Reber)
5 (Grocns)
teCurley
Gilkey
174
161
176
139
191
113
BCD5
348
(7)2
125
(16)
378
(7)
188
(7)
149
(8)
197
(11)
SS
171
(7)
91.7
(16)
276
(7)
79
(7)
240
(8)
38
01)
M*,
0.38
(8)
0.56
(16)
0.16
(6)
0.04
(7)
0.18
(9)
0.81
(10)
»2
0.02
(7)
0.02
(15)
0.03
(7)
0.02
(6)
0.02
(9)
0.02
(10)
•«3
55.9
(8)
36.1
(16)
53.3
(7)
35.5
(7)
37.8
(9)
35
(10)
TKN
70.5
(7)
51.3
(16)
71.8
(6)
45.6
(7)
56.9
(9)
58.4
(10)
TN
70.9
(7)
51.8
(15)
71.9
(5)
45.67
(6)
57.1
(9)
59.2
(10)
FC
1.0 x ID6
(8)
8.0 xlO4
(14)
5.4 xlO5
(6)
7.0 xlO4
(6)
2.0x10*
(10)
1.1 xlO5
(10)
TC
2.5
9.9
xlO5
(6)
xlO5
(10)
2.1
7.7
1.5
1.8
xlO5
(6)
xlO5
(5)
xlO5
(8)
xlO6
(9)
Boettdw 194222193
(11) (U)
Anderson — 322 203 0.24 0.02 32.56 47.2 47.5 8.1 x ID4 1.3 x 106
(3) (3) (3) (3) (3) (2) (2) (2) (2)
Weighted 164 217 146 0.4 0.02 40.6 57.1 57.5 2.6 x 1C5 1.32 x 105
Arithmetic(7) (70) (70) (59) (57) (60) (51) (54) (56) (46)
Average
1 8005, SS and nitrogen expressed as mg/i; arithmetic mean.
Fecal and total coliform expressed as org/100 ml; geometric mean.
2 Number of samples.
Though lower, seasonal fluctuations in total nitrogen and nitrate-nitrogen
found in intermittent recirculating sand filter effluents were similar to
variations noted in recirculating sand filter effluents (Chapter 2).
4-10
(58)
-------
TABLE 4-«. A COMPARISON BETWEEN INTERMITTENT RECIRCUIATING SAW) FILTER EFFLUENTS
SAND FILTER EFaUENT CHARACTERISTICS1-2
AVE.
aow
SYSTEM (gpd)
1 (Turner) 278
2 (Roberts) 174
3 (McClaflln) 161
4 (Reber) !76
5 (Grooms) 139
6 (Cheste-) —
7 (Mattescn) —
8 (Steldley) —
Weighted 186
Arithmetic (5)
Average
(Excludes System 8)
Weighted 186
Arithmetic (5)
Average
(Includes System 8)
BO*
3.0.
(7)3
3.8
(8)
2.8
(13)
(3?
4.0
(4)
3.5
(11)
3.6
(10)
28.9
(20)
3.4
(56)
ftl
SS
3.1
(7)
3.8
(8)
5.1
(7)
fe!
5.0
(2)
3.6
2.0
(17)
21.5
(45)
3.4
(100)
9.0
(145)
N02
0.09
(5)
0.06
(8)
0.06
(14)
0.06
(5)
0.04
(4)
0.06
(2)
0.05
(9™
0.14
(19)
0.06
(38)
0.09
(57)
«32
23.2
(5)
38.4
(8)
33.2
(14)
32.4
(2)
24.4
(2)
37.1
(14)
82.0
(19)
6.5
(36)
33.3
(45)
21.7
(81)
*3
0.47
(5)
0.6
(8)
0.22
(14)
0.44
(4)
0.21
(4)
0.18
(1)
0.23
(7)
5.5
(20)
0.36
(36)
2.2
(56)
TKN
1.2
(4)
1.1
(8)
0.8
(14)
1.7
(4)
1.5
(4)
O./
(1)
0.5
(8)
12.5
(19)
1.1
(35)
5.1
(54)
TN
24.5
(5)
39.6
(8)
34.1
(14)
34.2
(2)
26
(2)
37.9
(14)
82.6
(19)
19.1
(19)
34.9
(45)
30.2
(64)
FC
54
(6)
51
(10)
113
(12)
41
(5)
17
(4)
54
(55)
29
(20)
705
(46)
54
(112)
244
(158)
TC
1.833
(2)
858
(8)
572
(7)
950
(5)
1.046
(4)
523
(54)
520
(14)
3.100
(37)
628
(94)
1.326
(f31)
1 6005. SS, and nitrogen expressed as mg/1; arithmetic mean. Fecal and
total collfon* expressed as org/100 ml; geometric mean.
2 Weighted average excludes nitrogen contents from Systan 7.
3 Number of samples.
XG922 (1)
-------
TABLE 4-7. A SEASONAL COMPARISON Of NITROGEN CONCENTRATIONS IN RESIDENTIAL INfERMITTENT RECIRCULATING SAND FILTER EFFLUENTS1
§
NOVEMBER - APRIL
SYSTEM
1 (Turner)
2 (Roberts)
3 (McClafUn)
4 (Reber)
5 (Groans)
6 (Chester)
7 (Matteson)
8 (Steldley)
Weighted
Arithmetic
Average
(Excludes Systems
N02
0.07
(I)2
0.04
(4)
0.06
(8)
0.05
(2)
—
—
0.04
(3)
0.02
(12)
0.05
(15)
7 and 8)
«3
18.8
(1)
32.6
(7)
32.4
(9)
32.3
(4)
—
—
34.8
(9)
1.7
(13)
31.8
(21)
HH3
0.9
(1)
0.76
(5)
0.19
(9)
0.14
(2)
—
—
0.1
(3)
5.3
(12)
0.4
(17)
TKN
1.4
(1)
0.55
(5)
0.63
(9)
0.44
(4)
—
—
0.63
(3)
12.5
(12)
0.6
(19)
TN
19.3
(1)
33.2
(7)
33.1
(9)
32.8
(4)
—
—
35.5
(3)
14.2
(12)
32.4
(21)
"°2
0.09
(4)
0.02
(2)
0.02
(3)
—
0.04
(2)
0.06
(2)
0.06
(6)
0.02
(6)
0.05
(13)
N03
24.3
(4)
48.6
(2)
40.5
(3)
—
24.4
(2)
37.1
(14)
123.4
(10)
11.64
(12)
35.4
(25)
MAY - OCTOBER
NH3
0.36
(4)
0.15
(2)
0.3
(3)
—
0.23
(3)
0.18
(1)
0.33
(4)
5.64
16)
0.27
(13)
TKN
1.2
(4)
(0.7)
(2)
0.7
(3)
—
1.0
(3)
0.7
(1)
48
(5)
9.7
(6)
0.92
(14)
TN
25.6
(4)
49.3
41.2
(3)
—
25.7
(3)
37.9
(14)
124
(4)
21.4
(6)
36.4
(14)
1 Nitrogen values expressed as mg/1; arithmetic means.
2 Number of samples.
XG926
-------
As was the case with recirculating sand filter affluents, organically bound
and free ammonia nitrogen in intermittent recirculating sand filter
effluent showed little seasonal variation. This suggested dilution by
precipitation, organic nitrogen accumulation during cool moist months, and
mineralization during warm dry months, or denitrification in anaerobic
microsites during moist months were responsible for annual fluctuations in
total nitrogen and nitrate-nitrogen.
Some denitrification of septic tank effluent probably occurred at the
gravel-sand interface of the filter infiltration trenches once a biological
mat (biomat) formed and effluent ponding within trenches
occurred. Denitrification also likely took place in the saturated zone
where treatment sand contacted underdrain gravel.
Although data do not support the hypothesis, a small amount of nitrogen
loss may have occurred due to ammonia volatilization during warm, dry
months.
Comparison of sand filter effluent quality data (Tables 4-8, 4-9, and 4-10)
showed 3 distinct levels of treatment which corresponded to the degree of
biomat formation and ponding.
4-13
(61)
-------
TABLE 4-8. THE RELATIONSHIP BETWEEN RESIDENTIAL INTERMITTENT RECIRCULATING SAND
FILTER TREATMENT AND FILTER ABSORPTION TRENCH MATTING; PRE-MAT
DEVELOPMENT PERIOD1
CHARACTERISTIC
SYSTEM
1 (Turner)
2 (Roberts)
3 (McClaflin)
4 (Reber)
5 (Groans)
6 (Chester)3
7 (Matteson)4
8 (Steidley)
weignted
Arithmetic
Averaae
8005
2.5.
(2)2
5.5
(2)
—
—
—
W
fa
—
3.9
(21)
SS
5.5
(12)
9.0
(2)
...
—
—
to
?i7)
4.8
(10)
5.0
(41)
N02 + N03
—
1.2
(2)
—
—
—
%f
81.5
(19)
—
12.7
(10)
NH3 TKN
—
2.5 3.9
(2) (2)
— —
— —
— —
4-1 §-3.
(8) (8)
?>f W
— —
3.8 5.4
(10) (10)
FC
...
(2)
—
—
—
ft
28
(19)
479
(11)
326
(39)
TC
...
16,000
(2)
...
—
—
1.461
(6)
1,590
(15)
3.022
(11)
2,841
(35)
1 Table includes data from the period immediately following filter systen
startup to the point when a visible mat formedat the base of filter septic
tank effluent absorption trenches.
^ Number of samples.
3 Data shown is for a 2 month interval following the diversion of septic tank
effluent into a previously unused filter absorption trench.
Weighted average excludes nitrogen species from System 7 since only a toilet,
bathroom lavatory, shower and kitchen sink were attached to the system,
causing nitrogen content to be much higher than other residences studied.
Although no visible mat appeared at the bottom of System 7's filter absorption
trenches during the period the system was monitored (probably as a result of
the limited hydraulic loading, low BODc and low suspended solids applied to
the filter) there was a definite increase in nitrogen species with time
indicating sane nitrogen had been assimilated as biomass after the filter was
placed into operation.
4-14
(62)
-------
TABLE 4-9. THE RELATIONSHIP BETWEEN RESIDENTIAL INTERMITTENT RECIRCULATING SAND FILTER
TREATMENT AND FILTER ABSORPTION TRENCH MATTING; AFTER A MAT FORMED1
CH/KACTERISTIC
SYSTEM
1 (Turner)
2 (Roberts)
3 (McClaflin)
4 (Reber)
5 (Grooms)
6 (Chester)
7 (Matteson)
8 (Steidley)
Weighted
Arithmetic
Average
B005
3.0o
(7)2
3.8
(3)
2.8
(13)
3.3
(3)
4.0
(4)
2.0
(4)
—
...
3.1
(39)
SS
3.1
(7)
3.8
(8)
5.1
(7)
1.5
(2)
5.0
(2)
3.3
(42)
—
3.0
(9)
3.5
(77)
N02 + N03
23.2
(5)
46.5
(7)
33.2
(14)
32.4
(2)
24.4
(2)
37.1
(14)
—
24.5
(9)
33.2
(53)
NH3
0.47
(5)
0.60
(8)
0.22
(14)
0.44
(4)
0.21
(4)
0.18
(1)
—
...
0.36
(36)
1KN
1.2
(5)
1.1
(8)
0.8
(14)
1.7
(4)
1.5
(4)
0.7
(1)
—
1.1
(36)
FC
54
(6)
22
(7)
113
(12)
41
(5)
17
(4)
40
(42)
—
58
(9)
51
(85)
TC
1,833
(2)
322
(6)
572
(7)
600
(5)
1,046
(4)
472
(42)
—
402
(9)
536
(75)
Data shown is from the period when trench matting first appeared to the point
just before trenches became completely clogged by a bicmat.
Number of samples.
4-15
(63)
-------
TABLE 4-10. THE RELATIONSHIP BETWEEN RESIDENTIAL INTERMITTENT RECIRCULATING SAND
FILTER TREATMENT AND FILTER ABSORPTION TRENCH MATTING; AFTER TRENCH
CLOGGING AND EFFLUENT PONDING ABOVE THE FILTER SURFACE1
CHARACTERISTIC
1
2
3
4
5
6
7
8
SYSTEM
( Turner)
(Roberts)
(McClaflin)
(Reber)
(Grooms)
(Chester)
(Matteson)
(Steidley)
BOD5 SS
47.1 61.8
(6)2 (6)
__„ „__
— -
—
—
— —
— —
28.9 33
(20) (25)
N02 + N03 NH3 TXN FC
0.26 16.4 33.4 10,895
(7) (7) (7) (9)
— __„ —
—- „.. ... _-_
— _„_ _.. ...
— - — — —
— — — —
— — —
0.27 55 12.5 1,802
(20) (20) (19) (26)
TC
.._
—
—
—
__.
—
—
1.7 x 104
(9)
1 Data shown is from the period after trenches had become completely clogged by
a biomat and vented to the filter surface.
2 Number of samples.
The first few weeks following filter use (early mat development), were
accompanied by a steady decline in total coliform, fecal coliform, ammonia
nitrogen and total kjeldahl nitrogen. During this period, fecal and total
coliform were reduced an average of 3 logs. Data suggested nitrogen
accumulated as biomass at the gravel-sand interface of filter septic tank
effluent infiltration trenches (Table 4-8). Work by Magdoff et al.t (6)
4-16
(64)
-------
support the idea that nitrogen accumulated as biomass. In their sand
column studies, they noted accumulations of nitrogen in the upper few
centimeters of sand adjacent to the sand-gravel interface.
After 60 to 90 days (depending upon hydraulic loading and influent waste
strength), a visible biomat formed at the base of septic tank effluent
infiltration trenches. When matting occurred, filter treatment increased
(Table 4-9). Further reductions 1n BOD , SS, amonia nitrogen, and total
kjeldahl nitrogen were evident. Nitrate and total nitrogen more than
doubled, and fecal and total indicators decreased an additional log. The
maximum level of treatment (data not shown) occurred just before
infiltration trench sidewalls became completely clogged with a biomat.
The biological matting of septic tank effluent infiltration trenches was
responsible for the higher level of treatment provided by the filters. A
similar relationship between mat formation and high levels of bacterial
removal were reported by Ziebell et al., (7) in their Plainfield loamy sand
column studies.
With the exception of Systems 3 and 7, infiltrative surfaces of all filter
septic tank effluent infiltration trenches eventually became clogged with
a biomat. Where filter use continued under clogged conditions (Systems
1 and 8), septic tank effluent vented from infiltration trenches and ponded
on the filter surface. When this occurred there was a sharp decline in
filter treatment (Table 4-10). BOD. and SS increased sharply. Less
5
4-17
(65)
-------
than 2% of the nitrogen in filter effluent was nitrified, and f.ical
conform levels rose 3 legs.
Since treatment sands regained moist but unsaturated at this time, ponded
effluent probably short circuited to the underdrain by channelized flaw
along the filter container wall. This theory was supported by the fact
that there was little difference in the total nitrogen content of effluent
ponded over filters and that which had passed through the filters (data not
; indicating little denitrification had occurred,
Filter effluent quality produced under ponded conditions correlated well
with work done by other investigators. Russell (8) determined a high
quantity of nitrate ion must be available if denitrification is to occur.
Studies by Bouma, et al. (9) demonstrated greater removal of chemical
impurities from septic tank effluents took place under unsaturated aerobic
conditions than under saturated anaerobic conditions, and laboratory column
findings by McCoy and Ziebell (10) showed the greatest lev«»l of bacterial
removal took place under conditions of unsaturated flow.
Although the majority of the nitrogen (98%) in effluent from System 8 was
in a reduced form once filter ponding occurred, the Influence of
groundwater infiltration was quite apparent (Table 4-10). The total
nitrogen content in effluent from System 8 was 2.6 times lower than that
found in effluent from System 1.
4-18
(66)
-------
INDUSTRIAL FILTER EFFLUENT TREATMENT
The Industrial intermittent redrculatlng sand filter (System 9) provided a
high level of effluent treatment. The filter reduced BOO, and SS 901 and
931 respectively and lowered conforms 2 logs (Table 4-11).
Since effluent sampling from System 9 was limited to Its first 9 months
operation, data were not sufficient to determine 1f nitrate-nitrogen and
total nitrogen contents fluctuated seasonally the way they did 1n
residential filter effluents.
Hydraulic loading had considerate Influence on filter nitrification.
Effluent data from System 9 (loaded at 4.44 gal/ft %) Indicated quasi-
saturated conditions In filter sands limited the degree of nitrification.
Forty-six and three-tenths percent of the nitrogen 1n System 9's effluent
was oxidized. By comparison, 96.81 of the nitrogen In residential sand
2
filter effluents (loaded at an average of 1.12 gal/ft /d) was 1n an
oxidized form.
Hydraulic loading also Influenced degree of den1tr1f1cat1on provided by
filters. Considerably greater denltrlfIcatlon (581) took place 1n
System 9, even though there was Incomplete nitrification of ammonia, since
sands 1n that filter were more saturated. Most authorities agree
denltrlflcatlon Is encouraged by poor aeration and the availability of
large amounts of nitrate 1on (11).
4-19
(67)
-------
TABLE 4-11. A COMPARISON BETWEEN INDUSTRIAL SEPTIC TANK AND INTERMITTENT
RECIRCULATING SAND FILTER EFFLUENTS (SYSTEM 9)1'2
EFFLUENT3-4
CHARACTERISTIC
B005
ss
N02
N03
NH-j
TKN
TN
FC
TC
SEPTIC
TANK
EFFLUENT
53.6
(ID5
45
(7)
0.04
(11)
0.16
(10)
49.1
(10)
76.3
(8)
76.5
(8)
3.4 x 105
CO)
7.0 x 105
(5)
INTERMITTENT
RECIRCULATING
SAND FILTER EFFLUENT
5.2
(2?)
3.1
(23)
0.43
(19)
14.3
(23)
13.6
(20)
16.9
(21)
31.8
(21)
2832
(22)
3590
(8)
t
CHANGE
90
93
91
99
72
78
58
99
(2 logs)
99
(2 logs)
* Wastiwater was from a sawmill and mill office building.
2 Characteristics are frora an Intermittent reclrculatlng sand filter (the
1st of 2 sand filters) operated frora June 1379 to July 1980.
3 BOQ5, SS and nitrogen expressed as mg/1; arithmetic mean.
Fecal and total collforra expressed as org/100 ml; geometric mean.
5 Number of samples.
4-20
(68)
-------
TABLE 4-12. THE RELATIONSHIP BETWEEN INTERMITTENT RECIRCULATING SA.NO FILTER SEPTIC TANK
EFFLUENT ABSORPTION BED HATTING AND FILTER TREATMENT (SYSTEM 9)1
PERIOD B005 SS NO? N03 NH3 TKN TN FC TC
Before Clog2
Mat Formation
After Mat4
Formation
Early Stages^
of Bed Failure
6.6
(5)3
3.6
(14)
5.3
(4)
4.6
(5)
2.9
(15)
3.0
(3)
0.27
(3)
0.36
(12)
0.52
(3)
8.43
(4)
18.0
(15)
6.1
(3)
3.4?
(1)
12.1
(15)
21.6
(4)
4.0
(1)
14.3
(15)
27.3
(4)
12.7
(4)
32.8
(15)
33.9
(4)
5.175
(5)
1,716
(14)
4,989
(3)
6,000
(3)
2,432
(3)
...
1 8005, SS and nitrogen expressed as mg/1, arithmetic mean. Fecal and
total collform expressed as org/100 ml; geometric mean.
2 The first 90 days of operation before a visible clog mat formed.
3 Number of samples.
4 168 day period between the first visible signs of mat formation and filter bed
failure.
5 A 54 day period following the first Indications of filter septic tank effluent
Injection bed failure.
XG1010
-------
matt 4-ij. IHTEHMITTOT RECIKCUUTII* vn run* OHMIICH MO NWKTDIMCI *n»
FEATIW
Systea
Weeds or leaves on1
Filter Surface
Haneovner Weeded
and RaVed Filter
Surface
Pu«p Shut Off By
Haneoxner to
Control Weeds
Orifices Clogged?
by Grit or Organic
Halter
Hoseoxner Cleared
Clogged Orlf Icn
Overspray Beyond
/— v * Filter Enclosure
•-J I
0 ts> Filter Trenches
is* Clogged by Blout
Effluent Ponded
at Filter Surface
Sewtje Odor
Outside Filter
Pump Failure
Honths Filter)
Observed
Tines Observed
1 (TUtMX)
Tn
(A)(W)(L)
No
No
Tn
(G){OM)
No
Tes
Tes
(Urn.)
Tes
Yet
No
14
14
Z(ROBDirS)
fito)
Tn
Tn
Tn
Tn
No
No
— .
No
Tn
i no am-.)
Tn
Tn
No
11
7
5 (SKXK)
Tn
No
No
No
Yes
No
No
No
No
•
S
t (OCSTO)
»n
*,
Tn
Tn
Ci)
No
Tn
1*.
(21 MM.)
No
No
No
J3
6!
; (wnta
Tn
No
No
Tn
|G)Of)
Tn
Tn
No
No
No
No
14
1*
X) B (STtlOirr)
Tn
•o
No
Trt
(G)(CM)
No
Tn
Tn
(IS CDS.)
Tn
Tn
No
21
*
f (IHT1. PVCR CO)
No
—
No
Nu
Tn
(8 -os.)
Tn
No
No
U4
24
1 (A) • algae; (U) • teedi; and (L) • leaf and needle fall.
2s* grit; and (») * earthwna and other form of orjanlc "atter.
3 NiMber of observations recorded for SystoB »-9 reflects those aade by both Lane Cowrty DepartaeRt of Envt
4 Nurter of earths observed reflects the length of ttae Systea * MS observed before It MS reconstructed
roncntal Mangmnt and KQ staffs.
ClCW
-------
Due to Its heavier hydraulic load, System 9 removed fecal Indicators less
efficiently (2 logs) than Systems 1-7 (4 logs). Bouma et al., (i») reportsd
a similar decline 1n bacterial removal under conditions of quasi-saturated
flow.
As was the case with residential sand filters, treatment provided by
System 9 Improved with the formation of a blomat and declined once
effluent ponded In the bed to vent to the filter surface (Table 4-12).
FILTER OPERATION AND MAINTENANCE
Because of their exposure to the atmosphere, filter surfaces (Systems
1 to 8) were subjected to freezing, accumulation of leaves, needles,
and other fallen debris, and weed growth (Table 4-13).
Systems 1 to 8 Iced over during a period of cold (10-20 °F) weather and
freezing rain 1n late January 1980. Effluent applied at each reclrculatlon
cycle added to the filter 1ce mass. Ice accumulated ct System 1 to the
extent It dislodged fencing which surrounded the filter. When this
occurred, sprayed effluent ran outside the filter.
Since reclrculatlon tanks were placed Immediately outside filters, no check
valves were used along pressure distribution piping between reclrculatlon
pumps and filter spray heads. This permitted effluent remaining 1n
pressure distribution piping to drain back to the reclrculatlon tank at the
end of each pump cycle and prevented spray head freezing.
4-23
(71)
-------
Algae, grasses, and many other weeds grew abundantly on filter surfaces
during spring, summer and early fall months. Leaf litter removal and
weeding were required at least once each spring and fall. System users
generally failed to provide this maintenance. Only three filter owners
(37.5X) kept their filters routinely weeded and raked. And, as a weed
control measure, three system owners turned their recirculatlon pumps off
for extended periods during summer months.
When dense weeds wers allowed to accumulate at System 1, a thin organic mat
developed over the filter surface. The mat caused sprayed effluent to pond
In a number of small local depressions. However, sands Immediately below
the filter surface remained unsaturated. Once the ir.at was punctured,
ponded effluent quickly drained Into filter sands.
Sprayhead orifices at 5 systems became clogged by grit, earthworms and
other organic matter. Recirculatlon pumps at Systems 1, 6, 7 and 8 were
placed directly on pump tank floors. Small pieces of concrete, sand, and
other gritty debris were discharged with pumped effluent for several weeks
following system startup. During that time, orifices frequently became
clogged by these materials. Recalculation pumps 1n Systems 3, 4, and 5
were placed on 8 in. high concrete blocks. Orifices 1n those systems
remained unclogged.
Earthworms occasionally clogged the sprayhead orifices of Systems 1, 7,
and 8. It appeared worms had been pumped to sprayheads from recirculatlon
tanks.
4-24
(72)
-------
Although sprayheads were reacMly removable and accessible for cleaning,
system users generally failed to perform this maintenance.
Overspray occurred at all filters open to the atmosphere except System 4
which was lined with corrugated plastic sheeting which prevented overspray
from passing outside that filter. At each recirculation cycle, a small
amount of sprayed effluent passed between board fencing which enclosed
Systems 1, 2, 5, 6, 7, and 8. Overspray also passed beyond the concrete
container wall of System 3. A fenced enclosure was never constructed
around that filter.
Spray from shrub heads displaced a minor amount of sand in all systems.
However, sand displacement did not appear to Interfere with filter
performance.
With continued use, filter septic tank effluent Infiltration trenches in
Systems 1, 2, 4, 6, 8 and 9 became completely clogged by a blomat.
A mat also formed at the base and part way up the sidewall (2 in.) of
System 3. However, complete matting did not occur at that system during
the monitoring period. System 5 was replaced with an Intermittent sand
filter (Chapter 3) following 7 months use. The degree of filter trench
matting was not determined during the time it was operated.
4-25
(73)
-------
Trench matting was never apparent In System 7. Low hydraulic loading and
wastewater with limited organic strength probably explain why clogging was
never observed.
Prolonged application of septic tank effluent to filter absorption trenches
caused a blomat to form at the trench gravel-sand Interface within a few
months (generally 60-120 days) of filter use.
Matting appeared at trench bottoms first. After absorption trench bottoms
matted, Infiltration decreased to the extent sldewall area was required to
dispose of the hydraulic load. In time, effluent ponded 1n trenches. The
depth of ponding corresponded to the height of the blomat at trench
sidewalls. Matting eventually forced over the total trench 1nf1ltrat1ve
surface. When this occurred, the effluent Infiltration rate was not
sufficient to absorb all applied effluent so ponded effluent was forced to
vent to the filter surface. Bouma et al., (9) and McGauhey and Winneberger
(12) reported similar decreases 1n Infiltration rates with blomat
formation 1n field studies where absorption trenches were subjected to
continued application of septic tank effluent.
Data (Table 4-14) suggested septic tank effluent quality had considerable
Impact on the rate of filter Infiltration trench clogging. Systems 2 and 3
received approximately the same hydraulic load and used similar filter
4-26
(74)
-------
TABLE 4-14. THE RELATIONSHIP BETWEEN BIOMAT FORMATION IN INTERMITTENT
RECIRCULATING SAND KILTER SEPTIC TANK EFFLUENT ABSORPTION
TRENCHES WITH HYDRAULIC LOADING, INFLUENT BODc AND SUSPENDED
SOLIDS AND FILTER SAND CHARACTERISTICS
FEATURE
System 2 (Roberts)
Ave. Dally Flow
(gpd)
STE - BOD5
STE - SS
Sand Effective
Size (mm)
Sand - Uniformity
Coefficient
% Co. & V. Co.
Sand in Filter Media
X Gravel in
Filter Media
Filter Absorption
174
348
(7)1
171
(7)
0.27
2.0
52
14
64
3 (McClafUn)
161
125
(16)
92
(7)
0.3
3.2
56
16
96
4 (Reber)
176
378
(7)
276
(7)
0.3
1.5
28
2
128
Trench Infiltrative
Surface (ft2)
No. Months Before
Trenches Completely
Clogged by Biomat
21
Partially Clogged
(2 in.) after 29 mos.
11
Number of samples.
sands, but received effluents that had significantly different BOD_ and
SS contents. * After 30 months use, a biomat covered 36 ft of trench
See Chapter 15 for a discussion on the abnormally low waste strength
received by System 5.
4-27
(75)
-------
Infiltrative surface in System 3. The mat caused 2 In. of effluent to pond
1n trenches. Following 21 months use, the entire filter trench
infiltrative surface (64 ft2) of System 2 became clogged by a biomat.
Matting caused permanent ponding in trenches.
Although it was difficult to determine whether BOD5 or SS affected the
rate of clogging the most, data strongly suggests septic tank effluent
waste strength had measurable impact on the rate of clog mat formation.
Several other investigators feel the concentration of BOD,, and SS impacts
the rate of mat formation (13, 14, 15, 16, 17).
A comparison of effluent received by System 2 and and System 4 supported
observations reported by Weibel et al., (15) and Laak (16) that the rate of
clogging in infiltration trenches which received septic tank effluent was
directly related to the concentrations of suspended solids in wastewater.
Although filter sands used in System 4 were finer than those used in
System 2, the infiltrative surface of Filter 4's septic tank effluent
o
infiltration trenches (128 ft ) was two times greater than that of System 2
0
ft ) (Table 4-2). Both systems received similar hydraul ic and BOD5
, but System 4 received 61% (276 mg/1 vs. 171 mg/1) more suspended
solids than System 2 (Table 4-5). Trench infiltrative surfaces in System 4
became completely clogged by a biomat 10 months sooner than infiltrative
surfaces in System 2.
4-28
(76)
-------
Data indicated hydraulic loading affected the rate of filter infiltration
trench clogging. Disposal trenches in System 1 received septic tank
effluent at an average rate of 1.42 gal/ft2/d (Table 4-3), 0.2 gal/ft2/d
greater than the clog equilibrium rate reported for medium sand by
Bouma et al., (9, 18). In addition to septic tank effluent, trenches
received an additional hydraulic load with each recirculation cycle. By
the end of eleven months, trenches in System 1 had become completely
clogged by a biomat.
System 9 was also influenced by a high hydraulic loading rate
2
(4.4 gal/ft /d). Trenches clogged after the system had been in operation 8
months. The relatively low septic tank effluent waste strength received by
System 9 (Table 4-11) probably caused the rate of biomat development to be
slower than it would have been had the filter received residential sjptic
tank effluent. Average BOD5 and SS concentrations in residential septic
tank effluents (Table 4-5) were approximately 4 times and 3 times higher,
respectively, than those contained in effluent discharged to System 9.
The influence of groundwater infiltration on biomat formation was also
apparent at System 8. Infiltrated groundwater accelerated the rate of
mat formation in that system.
No data were available to determine the influence septic tank effluent
waste strength and hydraulic loading had on the rate cf crust formation
at other filters.
4-29
(77)
-------
One to 2 months after septic tank effluent Infiltration trench biomatting
forced wastewater to vent to the filter surface (Systems 1, 4, 8, and 9), a
second biomat formed at the sand filter surface (Table 4-13). Matting
caused a mixture of septic tank and filtered effluents to pond continuously
above the filter. Sands beneath the mat remained moist, but unsaturated.
When matting was disrupted by scraping the filter surface, ponded watur
quickly drained into sands. However, matting quickly reformed. When
ponded water was allowed to stand over the surface of System 1 for 2
monthsv the biomat thickened to approximately 1/4 in.
Four to six weekr after filter surface matting appeared at Systems 1 and 8,
ponded effluent accumulated to the point it spilled over filter
containers.
A definite sewage odor accompanied surface matting and subsequent ponding
(Systems 1, 4, and 8). Since System 9 was enclosed, odors were not
apparent until one entered the structure housing that filter.
During summer months, mosquito larvae were observed 1n effluent ponded over
System 8.
Pump failures occurred at Systems 2 and 3. The redrculation pump at
System 2 burned out after 18 months operation. Failure was attributed to a
wiring short. The redrculation pump at System 3 burned out twice.
The first failure occurred after 19 months operation. A second pump
4-30
(78)
-------
failure occurred following four months use. Both failures were attributed
to motor burn out. System 3 was located in a rural area which may have
been subjected to wide variations in power. This may have been responsible
for pump motor burn out.
FILTER MODIFICATIONS
A number of modifications were made to intermittent recirculating sand
filter systems to determine if problems related to septic tank effluent,
Infiltration trench clogging, and subsequent wastewater surfacing could be
overcome.
INTERMITTENT RECIRCULATING PEA-GRAVEL FILTERS
Sands and infiltration trench gravels in System 4 were replaced with 3-6 mm
pea-gravel (Figure 4-2) shortly after wastewater surfaced from septic tank
effluent infiltration trenches. A second 12 x 12 x 3 ft 6 in. Inter-
mittent recirculating pea-gravel filter, System 10, was placed into
operation in late September 1980.
Septic tank effluent entered pea-gravel filters through 4 in. perforated
plastic piping bedded directly in pea-gravel filter media. After waste-
water drained through the pea-gravel, it collected in a 4 in. perforated
plastic pipe underdrain bedded beneath a 12 in. deep layer of 3/4 1n. to
2-1/2 in. washed gravel and flowed by gravity to a recirculation tank.
Effluent was then recirculated over the filter surface during a 1-5 minute
period each 1/2 hour. A partition at the base of the filter caused 3/4 of
the recirculated effluent to return to tha recirculation tank. The
4-31
(79)
-------
CO
IXJ
Fence
4" Distribution Pipe
42"
4" Underdrain
FIGURE 4-2. INTERMITTENT RECIRCULATING PEA-GRAVEL FILTER
-------
remainder of the effluent drained to subsurface disposal trenches.
A limited amount of data was collected to characterize pea-gravel filter
effluent quality. Pea-gravel filters lowered BOIL and SS 95% (Table 4-15).
These reductions were somewhat higher than decreases reported by University
of Illinois researchers who studied recirculating pea-gravel filters (19).
Pea-gravel filtration reduced total nitrogen 52%. Ninety-seven percent of
the nitrogen in pea-gravel filter effluent was oxidized compared to less
than 1% in septic tank effluent. These results were similar to results
obtained from recirculating sand filters and intermittent sand filters
(Chapters 2 and 3) out indicated a much higher level of nitrification than
Illinois recirculating pea-gravel filter studies (19). The higher dose
volumes (150 gal/recirculation event vs. 15-25 gal/recirculation event) and
lower dosing frequencies (5 times/d vs. 48 times/d) used in Illinois filter
studies probably account for differences in effluent findings.
Data suggested septic tank effluent underwent a period of nitrification
which was followed by a period of denitrification. Since no water ponded
at the pea-gravel, underdrain-gravel interface, observations suggested the
majority of the denitrification took place in moisture films coating
gravels and at points of gravel contact.
Pea-gravel filters reduced fecal coliforms by 2 logs and total coliforms by
1 log. The rate of flow and number of passes through filter media
determined bacterial removal (See Chapter 2).
4-33
(81)
-------
So little data was collected, It was difficult to determine what
caused the variations 1n effluent quality produced by Systems 4 and 10
(Table 4-16). Temperature and moisture conditions at the time filters were
placed Into operation may have affected their performance. System 4 was
placed Into use during warm, dry summer months while System 10 was placed
Into operation during cool, moist spring months.
TABLE 4-15. A COMPARISON BETWEEN SINGLE FAMILY RESIDENTIAL SEPTIC TANK AND
INTERMITTENT RECIRCULATING PEA-GRAVEL FILTER EFFLUENTS1
EFFLUENT
CHARACTERISTIC
BOD5
SS
N02
N03
NH3
TKN
TN
FC
TC
SEPTIC
TANK
EFFLUENT
326
(7)2
185
(6)
0.02
(6)
0.19
(7)
46.4
(7)
64.8
(6)
65.0
(6)
3.56 x 105
(5)
6.5 x 105
(5)
* 8005. SS and nitrogen expressed
total coHform expressed as orgy
INTERMITTENT
RECIRCULATING
PEA-GRAVEL
FILTER EFFLUENT
18
(7)
8.6
(5)
0.57
(6)
28.5
(6)
0.9
(6)
2.0
(5)
31.3
(6)
6.9 x 103
(5)
1.5 x 104
(5)
as mg/1; arithmetic mean.
'100 ml; geometric mean (av
*
CHANGE
95
95
96
99
98
97
52
98
(2 logs)
98
(1 loa)
Fecal and
erage of 2
systems, Table 2-16).
2 Number of samples.
4-34
(82)
-------
en
TABU 4-16. A QDffttRISOt BETtfEM 2 SWSU FAHIU RCSIDBtTIAL SEPTIC TANK AND INTERMITTENT RECIRCULAT1NC PEA-OtAVa FILTER EFFLUENTS*
SEPTIC T/WC EFFLUENT
CHARACTERISTICS
AVE2
aw
SY5TE* (gpd)
4 (Rebcr) 182
10 (Anderson) —
Weighted 182
Artttnetlc (1)
Average
BCD;
329
(*)3
322
(3)
326
(7)
SS
175
(*)
203
(2)
185
(6)
Wj
0.02
(<)
0.02
(3)
0.02
(6)
*3
0.15
(<)
0.24
(3)
0.19
(7)
*3
S5.7
;«)
32.6
(3)
46.4
(7)
TW
73.6
(*)
47.2
(2)
64.8
(6)
TH
73.8
(4)
47.5
(2)
65.0
(6)
FC
5.4 x IDS
(3)
8.1 x 10*
(2)
3.56 x 10*
(5)
TC
2.1 x 106
(3)
1.3 x 10*
(2)
6.5 x 10$
(5)
BODs
2
(4)
39.33
(3)
18
(7)
SS
2
(*)
35
(1)
8.6
(5)
•°2
0.1
(*)
0.52
(2)
0.57
(6)
PEA GRAVEL FILTER
EFRUENT CHARACTERISTICS
NtVj
37.6
(4)
10.24
(2)
28.5
(6)
*3
0.37
(4)
1.58
(2)
0.9
(6)
TKN
1.1
(4)
5.4
(2)
2.0
(5)
TN
38 .7
(4)
16.2
(2)
31.3
(6)
FC
748
(3)
16,193
(2)
6.9 x K>3
(5)
TC
1,482
(3)
36,332
(2)
1.5 x 10*
(5)
BO>5, SS. ml nitrogen expmscd n •9/1; arlttwettc «ear. Fec*l «id total col(for» expressed as
orq/100 •
? Ho riw v*s recorded for Sjrstoi 10.
3 Nwber of
K1087
-------
System 4 was located in an area where the mean annual temperature was
53.7 °F and annual precipitation ranged from 32-35 in. System 10 was
located in an area where the mean temperature averaged 51.3 °F and annual
precipitation was around 50 in. (20).
Data (not shown) also suggested the quality of effluent from System 10
improved with time, indicating mean values reported for that filter may not
be representative of that system's eventual treatment capability.
Pea-gravel filters required periodic weeding and spray head cleaning.
With each recirculation event, a small amount of sprayed effluent passed
through cracks between wooden fencing at System 10. During cool moist
months, a slight odor was also apparent in the immediate vicinity of that
filter. The inner plastic sheet lining System 4 prevented overspray
from escaping from that system. No sewage odor was detectable at
System 4.
Due to the coarse nature of their filter media, pea-gravel filters appeared
to be considerably less susceptible to filter biomat clogging and freezing
than intermittent recirculating sand filters. Pea-gravel filters showed no
indication of media clogging during the period they were monitored.
After 16 months operation a thin gray film of what appeared to be organic
matter coated pea-gravel media at System 10. A similar film was not
apparent at System 4 following 9 months use.
4-36
(84)
-------
ALTERNATE RESTING AND DOSING OF FILTER EFFLUENT ABSORPTION TRENCHES
Manually operated dosing valves (3 in. diameter recreational vehicle waste
dump valves) were Installed at Systems 6 and 8 to determine if resting of
bioinat clogged septic tank effluent infiltration trenches would restore
them to their original permeability (18). After 27 months operation, the 2
original septic tank effluent infiltration trenches in System 6 became
completely clogged by a biomat. At that time, a third, deeper (24 in. deep
with an 18 in. layer of crushed rock) wider (30 in.) effluent infiltration
trench was installed 8 in. inside existing trenches. Dump valves were
placed ahead of trenches and all flow was directed into the new trench.
After 30 days resting, the majority of the biomat which bordered the 2
original trenches had dissipated. After 60 days resting, matting had
almost completely disappeared (13). These results are similar to findings
reported by University of Wisconsin researchers (21) and Wiegand (22) in
his field studies of alternating systems in West Virginia.
Similar resting of a septic tank effluent Infiltration trench in System 8
failed to appreciably increase that trench's infiltration rate. When flow
to one of System 8's 2 trenches was blocked off, the hydraulic load to
the trench left in service was sufficient to cause effluent to surface.
This resulted 1n the formation of a second biomat and subsequent ponding
over the filter. These conditions caused sands adjacent to the rested
trench to remain anaerobic which substantially interfered with the rate of
biomat decomposition.
4-37
(85)
-------
INTERMITTENT RECIRCULATING GRAVEL-SAND FILTER
Following 11 months operation, System 9 was redesigned to process a
«y
hydraulic load of 5.9 gal/ft /d. Sands and gravels from the original
2
filter were replaced with a central 450 ft cell of coarse media (effective
size 3.2 mm; uniformity coefficient 1.68) and 2-113 ft2 polishing cells
(Figure 4-3). One polishing cell contained the same sized media as the
central cell. The other contained medium sand (effective size 0.35 mm;
uniformity coefficient 3.18).
Sepclc tank effluent Injection cycles and redrculatlon events were doubled
to offset the filter's smaller surface area. Septic tank effluent was
pumped to the large central cell 96 times par day. Filtered effluent was
reclrculated over the entire filter surface at Intervals between septic
tank effluent Injection events. Septic tank effluent injection events and
recirculation events were controlled by separate 30-mlnute time clock
controls.
A small amount of data was gathered from the intermittent recirculating
gravel-sand filter to characterize septic tank, coarse media and sand
polishing media effluents. Preliminary information indicated the filter
provided a high degree of treatment (Table 4-17). Filtration through the
gravel cell lowered BOD5 93«, SS 91X, and fecal indicators 2 logs.
4-38
(86)
-------
-Enclesure
Stacked Spray Heads
•
:.
ft
r
£ Fine Graiel J-
%m&&$&&fer
• -, - . _-;:'; Fine Gra»e 1 ' - .- ^ v ',
_^<^Jtvl6^^
*• _
',• ' • "V1- •' - ' , -:
Medium Sand
j.j^Alj-tJ^i.c^^S^^V^^
rr
.1
fj
T?
A
V
-a '-
Gravel
V A V A.
-Underdrains
FIGURE 4-3. INDUSTRIAL INTERMITTENT RECIRCULATING GRAVEL-SAND FILTER
-------
TABLE 4-17. A COMPARISON BETWEEN INDUSTRIAL SEPTIC TANK AND INTERMITTENT
RECIRCULATING GRAVEL/SAND FILTER EFFLUENTS (SYSTEM 9)1'2
INTERMITTENT RECIRCULATING
GRAVEL/SAND FILTER EFFLUENT
EFFLUENT
CHARACTERISTIC
BOD5
SS
N02
N03
NH3
TKN
TN
FC
TC
SEPTIC
TANK
EFFLUENT
69
(3)5
77
(2)
0.02
(3)
0.08
(2)
60.8
(3)
112.5
(2)
112.6
(2)
1.58 x 105
(2)
3.46 x 105
(2)
GRAVEL3
MEDIA
EFFLUENT
4.5
(2)
7.0
(1)
...
—
—
—
...
4336
(2)
9165
(2)
SAND4
MEDIA
EFFLUENT
3
(3)
11
(1)
O.C7
(3)
73.2
(3)
0.85
(3)
1.1
(1)
74.4
(1)
169
(3)
713
(3)
%
CHANGE
96
86
71
99
99
99
34
99
(3 logs)
99
(3 logs)
1 Flow averaged 5,000 gpd.
2 BOOs, SS, and nitrogen expressed as mg/1; arithmetic mean.
Fecal and total coHform expressed as org/100 ml; geometric mean.
3 Effluent from coarse cell (effective size 3.t nro; uniformity coefficient
1.68) was a mixture of wastewater that had passed through the filter one
time and effluent that had been filtered several times.
4 Effluent from the fine cell (effective size 0.36 mm; uniformity
coefficient 3.18) had been filtered at least 2 times.
5 Number of data points.
4-40
(88)
-------
Recirculation through System 9's polishing cell reduced BOD. 96% and SS
85X. Suspended solids levels were probably lower in coarse cell effluent
than they were in medium sand polishing cell effluent because clay and silt
sized particles washed from treatment sand added to solids values. Total
nitrogen in polishing cell effluent was reduced 34%. Ninety nine percent
of the nitrogen in sand filter effluent wis in the nitrate form compared to
less than 1% in septic tank effluent.
Recirculation through polishing cell sands decreased total and fecil
coliform organisms by 3 logs. It appears the pores between polishing sands
were small enough to decrease the rate of flow sufficiently to allov» good
bacterial removal to occur.
The Intermittent recirculating gravel-sand filter was observed on June 3,
1981 and March 4, 198". to determine its operating condition and maintenance
needs (3). Filter sands and sprinkler heads were not clogged. No odors
were detected within the filter enclosure or within the media Just below
the septic tank effluent injection bed. A thin, gray, "tacky" film coated
the treatment media at the interface between the pressure injection bed and
the coarse filter media. However, no biological growth appeared to clog
Interstitial areas between media. One of the septic tank effluent pressure
distribution laterals was cleaned out June 3, 1981 to determine 1f foreign
matter was present. Thsj lateral contained 2 cigarette filters and
considerable hair. As a result, a protective plastic screen was Installed
around the dosing pump to prevent neutral buoyancy articles from entering
the effluent distribution system (3).
4-41
(89)
-------
DISPOSAL FIELD PERFORMANCE
All Intermittent redrculatlng sand filters discharged effluent to 2 ft
deep, 2 ft wide soil absorption trenches which contained 4 1n. diameter
perforated plastic distribution piping bedded 1n a 12 1n. layer of washed
gravel.
Disposal trench systems behind Systems 1, 4, 5, 6, 7, and 8 were placed 1n
soils limited by shallowness to fraglpans, claypans and saprollte. These
soils had seasonal groundwater tables during wet fall, winter and spring
months. Disposal trenches at Systems 2 and 3 were located where clayey
subsoils were shallow to weathered basalt. The disposal field behind
System 9 was installed in deep, well drained silty clay loam soils.
Trench water levels were observed at Systems 1, 2, 3, 4, and 9 (Table
4-18). In spite of the fact Systems 1 to 4 were located 1n soils limited
by shallowness to subsoil pans, saprollte and/or seasonal groundwater,
disposal fields at those locations operated satisfactorily.
During wet winter months, Infiltrated ground and surface waters accumulated
1n the lower 4 to 6 in. of Systems 1 and 4. Water levels corresponded to
the depths trenches penetrated Into slowly permeable fraglpan (System 1)
and claypan (System 2) materials. Water levels receded during dry sunnier
months. At that time, the total wastewater load to each system was
absorbed by Us first disposal trench (Data not shown).
Disposal trenches at System 5 were Installed 1n heavy silty clay loam soils
4-42
(90)
-------
17 to 24 1n. to clayey subsoils. Trenches were excavated following a
period of heavy rainfall. During construction, soils bordering trench
bottoms and sldewalls were smeared and compacted. When disposal lines were
backfilled 4 to 8 in. of topsoll was scraped off the soil absorption
field. As a result, as little as 4 1n. unsettled backfill covered disposal
trench aggregate 1n several locations. The combination of smeared,
compacted soils and trench shallowness caused infiltrated ground and
surface water to seep continuously from trenches throughout the winter and
spring of 1980. Since soil damage was too extensive to permit trenches
to be reestablished 1n the initial disposal field area, System 5 was
replaced by an Intermittent sand filter at a location where well drained
soils were shallow to basa'it saprolite (Chapter 3).
Trench wetter levels were not observed at Systems 6 and 7. Both filter
systems were constructed to replace failing (surfacing) disposal fields.
System 6 drained to 2-75 ft long disposal trenches and System 7 discharged
to 100 linear ft of disposal trench. During the period filters were
monitored, no surfacing was evident in the vicinity of either system's soil
absorption trenches.
System 8 was also Installed to replace a failing disposal field. Hydraulic
overloading caused a mixture of partially treated septic tank effluent and
Infiltrated groundwater to surface from disposal trenches during wet
months. Disposal trenches were Installed 4-6 in. into a dense claypan.
System 9 data (Table 4-18) dramatically demonstrated the impact sand filter
4-43
(91)
-------
TABLE 4-18. A OESCRIPTIOH OF SITE OK)IIIe fraglpan at
silt low
10
278
4-serlal trenches
500 lin. ft.
(1000)
4.45
C.25
Noveater 1978
Jan. 1979-Har. 1980
15
2 (TOBERTSJ
20-31 In. to clayey
subsoil suspected
to be restrictive;
no Kittling evident
20-31 In. clay loan
over clay
7-9
174
6-serlal trenches
375 lln. ft.
(750>
too ryid to
detemlne
too rapid to
determine
No*e»ber 1979
No*. 1979-May 1931
13
SYSTEM
3 (MrOAHIN)
stilly pemeafale
grovel )y clay at 20 In.
20 In. cobbly, sllty
clay loa» over g. awlly
chy
25
161
5-serlal trenches
500 lin. ft
(1000)
19.3
1.66
October 1979
Jan. 1979-Aprll I960
10
24 In.: trenches contained 12 In. Mashed gravel and were gravity fed through
z Average percent side/all used for absorbing sand filtered effluent was detemtned during dryer sumer
often totally or pi't tally Inundated by grounoWta durlna high precipitation «nnthi (Hovaieer-Aprtl)
during high precipitation Months at Filter Syston ? and 5.
J Syste* «af Ir-, tailed as a repair since Insufficient area »«s callable
conventional septic tar* -sol' absorption systea.
for the Installation of a
4 (REBER)
seasonal groundwater
mottling, at 1R-20 In
dense claypan 20-35
20-35 In. sllty clay
Ion over a dense
clay pan
5
196
7-ser'al trenches
455 lln. ">..
(910)
2.25
9.52
June 1979
Nov. 1979-Har. 1961
10
9 (INT. PAPER CORP.)
in.
13 In. silt loan over
26 In. sllty clay loan
over sllty clay
5
3000
8-serlal trenches
480 lln. ft.
(960)
20.68
14.58
June 1979
July 1979-Aprl"t 1980
24
4 In. dlaneter perforated plastic distribution
•onths at Systems 1 and 4 since ' ~ench sick-walls were
. Percent sldewall absorbing effl -it IMS determined
K1107
-------
treatment had on the rate effluent was accepted by soil absorption
trenches. The first 4-1/2 months System 9 was in operation, all treated
effluent was absorbed by 60 linear ft of disposal trench. After that, in
response to periods of heavy precipitation, effluent occasionally drained
from the first drop box to a second 60 ft long disposal trench. An average
of 25 gal/fr/d sand filtered effluent was absorbed by the first disposal
trench during warm, dry months. Effluent was adsorbed by trenches at a
rate in excess of 12.5 gal/ft2/d during wet months (Novenber through March
when precipitation averaged 5.36, 6.25, 6.65, 4.5, and 4.3 in. per month
respectively) (20, 23).
During the period System 9 was being reconstructed, septic tank effluent
was routed to a drop box at the entry to the system's fifth disposal
trench. By the time filter reconstruction was completed (two months
later), septic tank effluent had ponded in three serial trenches and part
of a fourth trench (trenches 5, 6, 7, and 8). This was greater than
400 ft2 of trench sidewall. Very little (1.84 in.) rainfall fell during
the interval the filter was being reconstructed (23).
When the intermittent recirculating gravel-sand filter was placed into
operation, effluent was redirected to the first drop box. Thirteen months
after the system was placed on line all filtered effluent was being
absorbed by the first disposal trench (3).
The treatment of septic tank effluent by intermittent recirculating sand
filtration stops or substantially reduces the rate of soil biomat
4-45
(93)
-------
formation. Although investigators disagree on which factor plays the most
active role in biomat development, sand filtration markedly decreases BOD,.,
SS, and fecal bacterial organisms, the agents researchers feel are
primarily responsible for soil clogging (13, 14, 15, 16, 24, 25).
Soil absorption trenches following Systems 1, 6, and 9 were unearthed after
systems had operated 14, 31, and 8 months respectively, to determine if
biological matting had developed at trench gravel-soil Interfaces.
Observations were made during the wettest time of the year when conditions
favoring mat development were the most intensive. No indication of
organic slimes or biomat development was evident at any trench interface.
Trench gravels were unstained. Water in trenches was clear and odorless.
A pale, gray filamentous biological growth of what appeared to be slime
bacteria of the Sphaerotilus-Leptotrix group was observed on the inlet and
walls of the drop box leading to System 9's first disposal trench. No
organic sediments were found at the bottom of the box.
When BOD5 , SS, and fecal organisms were reduced by intermittent
recirculating sand filtration, soil absorption trench effluent accept-
ance rates remained high. Table 4-19 compares the mean rates filtered
effluent was accepted by disposal trenches located in silt loam, sllty
clay loam, and clay loam soils with septic tank loading rates recommended
by Bouma (26) and Machmeier (27) for deeper, better drained soils of the
4-46
(94)
-------
same texture. * Disposal trench examinations suggest filtered effluent was
absorbed at high rates because biomats were absent.
TABLE 4-19. A COMPARISON BETWEEN INTERMITTENT RECIRCULATING SAND FILTER SOIL ABSORPTION
TRENCH EFFLUENT ACCEPTANCE RATES AND SEPTIC TANK EFFLUENT LOADING RATES
RECOMMENDED BY BOUMA AND MACHMEIER IN SIMILAR SOILS
RECOMMENDED SEPTIC TANK'
3 (McClaflin)
4 (Reber)
EFFLUENT LOADING RATE (gal/d/ft*)
SYSTEM
1 (Turner)
2 (Roberts)
SOIL
TEXTURE
silt loam
clay loam
over clay
FILTERED1
EFFLUENT ACCEPTANCE
RATE (qal/d/ft2)
4.45
Too rapid to
determine
BOUMA
0.72
0.24
MACHMEIER
0.50
0.45
Cobbly silty clay
loam over
gravelly clay
silty clay loam
over claypan
9 (Int. Paper Co.) silt loam
over silty
clay loam
19,3
9.52
20.68
0.72
0.72
0.72
0.50
0.50
0.50
•"• Based on sidewall area.
Based on bottom area.
Exception: Disposal trenches following Filter 9 were placed in deep
well-drained soils.
4-47
(95)
-------
CONCLUSIONS
The surface of intermittent recirculating sand filters was subject to
freezing, accumulation of vegetative debris and growth of weeds. Spray
heads were subject to clogging by grit, earthworms and organic debris. Two
pump failures occurred because of faulty wiring. Overspray occurred at all
filters except System 4 which had the fencing lined with plastic to prevent
overspray.
BOD5, SS, and total nitrogen were reduced 98%, 98%, and 39* respectively.
Denitrification probably occurred in anaerobic moisture films in sand
grains and at points of sand grain contact and in the zone of near
saturation just above the sand-gravel interface. Total and fecal coliform
densities were reduced 4 logs.
A biomat eventually clogged septic tank effluent infiltration trenches in
all but 2 sand filters. This resulted in ponding of effluent in
infiltration trenches and on the sand filter surfaces. As a result, BOD,-
and SS increased sharply. Less than 2% of the nitrogen in filter effluent
was nitrified and fecal coliform densities increased 3 logs. Failure was
attributed mainly to hydraulic overloading.
Intermittent recirculating pea gravel sand filters reduced BODt and SS
95% and total nitrogen 52%. Fecal coliform and total coliform densities
were reduced by 2 logs and 1 log respectively.
4-48
(96)
-------
Biological clogging and freezing were not a problem because of the coarse
nature of the media.
Intermittent recirculating gravel-sand filtration reduced BODr , SS, and
J
total nitrogen 96%, 86%, and 34% respectively. Total and fecal coliform
densities were reduced 3 logs. No biological clogging has occurred to
date.
No biomat or odor occurred in disposal trenches following intermittent
recirculating sand filters. Observation of disposal trenches suggested
that sand filtration of septic tank effluent increased disposal trench
acceptance rates.
4-49
(97)
-------
REFERENCES
1 Burns, R. L. 1982. Manager, Building Services Division, Lane County
Planning and Community Development Department, Eugene, Oregon,
personal communication.
2 Colwell, 6. R. 1981. k-ter Pollution Control Engineer, Building
Services Division, Lane County Planning and Community Development
Department, Eugene, Oregon, personal communication.
3 Chickering, J. A. 1982. Property Development Consultant, Eugene,
Oregon, personal communication.
4 U. S. Environmental Protection Agency. 1979. Methods of Chemical
Analysis of Water and Wastes, EPA-600/4-79-020, Environmental
Monitoring and Support a&oratory, Cincinnati, Ohio.
5 American Public Health Asscciation. 1975. Standard Methods for the
Examination of Water and Wastewater. Prepared and published
jointly by: American iiater Works Association, Water Pollution
Control Federation, and American Public Health Association, 1740
Broadway, New York, N.Y.
6 Magdoff, F. R., D. R. Keeney, J. Bouma, and W. A. Ziebell. 19784b.
Columns Representing Mound-Type Disposal Systems for Septic Tank
Effluent. II. Nutrient Transformations and Bacterial Populations.
J. Environ. Qual. 3:228-234.
^ Ziebell, W. A., J. L. Anderson, J. Bouma, and E. McCoy. 1975a. Fecal
Bacteria: Removal from Sewage by Soils. Presented at Winter
Meetings of ASAE. Chicago, Illinois.
8 Russell, E. W. 1950. Soil Conditions and Plant Growth. Eighth Ed.
New York: Longmans, Green and Co.
9 Bouma, J., W. A. Ziebell, W. G. Walker, P. G. Olcott, E. McCoy and
F. D. Hole. 1972. Soil Absorption of Septic Tank Effluent.
Information Circular No. 20. University of Wisconsin-Extension.
Geological and Natural History Survey. 235 p.
10 McCoy, E. and W. A. Ziebell. 1975. The Effects of Effluents on
Groundwater: Bacteriological Aspects. In Proc. Second National
Conference on Individual On-S1te Wastewater Systems, National
Sanitation Foundation, Ann Arbor, MI, pp. 67-76.
11 Brady, N. C. 1974. The Nature and Properties of Soils (New York:
MacMillan, Inc.) p. 431.
4-50
(98)
-------
12 McGauhey, P. H. and J. H. Winneberger. 1964. Causes and Prevention of
Failure of Septic Tank Percolation Systems. Tech. studies Rept.
F.H.A. No. 533, Washington, D.C.
13 Winneberger, J.H., L. Francis, S. A. Hein and P. H. McGauhey. 1960.
Biological Aspects of Failure of Septic-Tank Percolation Systems.
Final Report. Sanitary Engineering Research Laboratory, University
of California, Berkeley, California.
14 Thomas, R. E., W. A. Schwartz and T. W. Bendixen. 1966. Soil
Chemical Changes and Infiltration Rate Reduction Under Sewage
Spreading. Soil Sci. Soc. of Amer. Proc. 30:641-6416.
15 Weibel, S. R., T. W. Bendixen, and J. B. Coulter. 1954. Studies on
Household Sewage Disposal Systems. Part III. Department of
Health, Education and Welfare. Public Health Service, Robert A.
Taft Sanitary Engineering Center, Cincinnati, Ohio.
16 Laak, R. 1970. Influence of Domestic Wastewater Pretreatment on Soil
Clogging. J. Water Pollution Control Federation, 42:1495-1500.
1' Laak, R. 1973. Wastewatar Disposal Systems in Unsewered Areas. Final
Report to Connecticut Research Commission, Civil Engr. Dept.,
Univ. of Conn. Storrs, Conn.
^ Bouma, J., F. Baker and P. Veneman. 1974b. Measurement of Water
Movement in Soil Pedons Above the Water Table. Univ. of Wisconsin
Extension, Geol. Nat. Hist. Surv., Info. C1rc. No. 27, Madison,
HI, 114 pp.
19 Ralph, D. J., D. H. Vanderholm, W. D. Lembke. 1979. Recirculatinq Sand
Filters for On-Site Sewage Treatment in Areas with Soils Unsuitable
for Seepage Fields. Paper No. 79-2587. Presented at the Winter
Meeting of ASAE. New Orleans, LA, 12 p.
20 U. S. Department of Commerce. 1979 & 1980. Monthly Normals of
Temperatures, Precipitation, and Heating and Cooling Degree Days
1940-70. U. S. Department of Commerce, National Oceanic and
Atmospheric Administration, Climatology of the United States No. 81
(By State). National Climatic Center, Asheville, N.C.
21 Small Scale Waste Management Project, University of Wisconsin,
Madison. 1978. Management of Small Waste Flows. EPA-600/2-78-
173, Municipal Environmental Research Laboratory, Cincinnati,
Ohio.
22 Wiegand, R. G. 1979. "Performance of Alternative On-site Sewage
Systems in Wood County, West Virginia," Jour, of Env.
Health, 42. 3, 133.
4-51
(99)
-------
24 McGauhey, P. H. and R. B. Krone. 1967. Soil Mantle as a Wastewater
Treatment System. Final report. SERL Report No. 67-11. Sanitary
Engineering Research Laboratory, University of California,
Berkeley, California.
25 Mitchell, R. and Z. Nevo. 1964. Effect of Bacterial Polysaccharide
Accumulation on Infiltration of Water Through Sand. Applied
Microbiology 12:219-223.
26 Bouma, J. 1975. "Unsaturated Flow During Soil Treatment of Septic
Tank Effluent," J. Environ. Eng. D.v., Amer. Soc. Civ. Eng., 101,
EE 6, 967-983.
27 Machmeier, R. E. 1975. "Design Criteria for Soil Treatment Systems/
paper presented at the American Society of Agricultural Engineers'
Winter Meeting, Chicago, 111.
XG906 4.52
(100)
-------
CHAPTER 5
EFFECT OF TILE DRAINAGE ON DISPOSAL OF SEPTIC TANK EFFLUENT IN WET SOILS
The Willamette Valley in Western Oregon contains about 1,500,000 acres of
soils with seasonally high water tables (1). These soils are not well
suited for treatment and disposal of septic tank effluent due to anaerobic
conditions which may occur in saturated disposal trenches. Accumulation of
organic material and other products of anaerobic decomposition reduces the
absorptive capacity of the soil system. In addition, saturated soils on
level site? may not accept the additi .ial hydraulic load from a disposal
field. This combination of factors frequently results in effluent coming
to ground surface.
Approximately 25% of the seasonally wet soils in the Willamette Valley are
moderately well to somewhat poorly drained (1). Typically, these soils are
medium to moderately fine textured, porous, and have moderate to moderately
slow permeability. As a result, they are readily drained 1f outlets
occur.
About 400,000 acres of these seasonally wet soils were drained between 1937
and 1964 (2) to increase agricultural production. Subsequently, many of
these agricultural soils were developed for residential uses. The chief
concern has been for the quality of drainage water discharged to outlets
from tile lines that are in close proximity to disposal trend.. .
5-1
(101)
-------
Reneau (3) observed that migration of organisms from disposal trenches to
an artificial drainage system did occur. He concluded that 1t was
difficult to assess the adequacy of an artificial drainage system with
respect to penetration of biological contaminants. Other researchers (4,5)
described the potential for survival and movement of fecal organisms from
septic tank effluent through a shallow, artificially saturated groundwater
system. They suggested giving more attention to the public health
implications of sewage movement through soil profiles.
Current health codes (6,7) assume that horizontal separation distances
between disposal trenches and tile drainage lines as well as vertical
separation distances between disposal trench bottoms and the highest level
attained by groundwater are adequate. However, there 1s little data to
Indicate how much movement of fecal organisms occurs from subsurface
disposal fields Into groundwater and ultimately Into tile drainage
systems.
This study was conducted to determine 1f tile lines placed 4 and 6 ft deep
with 10 and 20 ft horizontal separations, respectively, around disposal
fields were adequate to effectively lower water tables and provide aerobic
soil treatment of septic tank effluent.
MATERIALS AND METHODS
Special subsurface sewage disposal permits were Issued by the Oregon
Department of Environmental Quality to Individuals who had been denied
standard permits due to seasonally wet soil conditions. Oregon subsur-
5-2
(102)
-------
face rules require a minimum depth to temporary (seasonal) groundwater of
24 in. from ground surface. Sites .vere initially evaluated by Department soil
scientists to insure acceptable soil characteristics and adequate site relief
to allow drainage system outlets.
SITE DESCRIPTIONS
The experimental area was located primarily on soils formed in old alluvial
terraces of the Willamette Valley identified as the Senecal geomorphic surface
(8). Soils specifically studied belong to the Woodburn and Aloha series.
The Woodburn series (Aquultlc Argireroll) consists of deep, moderately well
drained soils formed in silty alluvium of mixed material or lacustrine
silts. The Aloha series (Aqulc Xerochept) consists of deep, somewhat
poorly drained soils formed 1n old alluvium or lacustrine silts. Depth to
groundwater varied from 9 to 36 in. Slope on all sites was 0-3*. Mean
annual precipitation in the Willamette Valley is 40-50 in.; mean trr.w?! air
o
temperature 1s 52 to 54 F.
SYSTEM DESIGN
Basic components of the systems studied were conventional disposal fields
consisting of 2 ft deep trenches on 10 ft centers. Disposal fields were
surrounded by 4 1n. diameter perimeter drains Installed 4 and 6 ft deep
with a gradient of 0.3 ft/100 ft (Figure 5-1). Perimeter drains 4 ft deep
were setback 10 ft from disposal trenches and perimeter drains 6 ft deep
were setback 20 ft from disposal trenches. The downgradlent junction of
the perimeter drain was tied in to a 30 in. diameter silt trap
5-3
(103)
-------
i_ en
o '
*>. •**
Tile Oraii.
/
1 _
1 —
1
— - -1
t— — — —
\
JT
Silt Trap
\
Septic Tank
4'-6'
10'-20'
FIGURE 5-1. TILE DEWATERING SYSTEM PLAN AND DETAIL OF PERIMETER DRAIN AND DISPOSAL FIELD
-------
Incoming Tile
Outlet Tile-
3C"-
4'-6'
18"
FIGURE 5-2. DETAIL OF SILT TRAP AND MONITORING PORTS
5-5
(105)
-------
(Figure 5-2). The primary function of the silt trap was to provide
monitoring points to sample drainage water.
As a further test of this approach, 3 systems with shallow (36 in. deep)
perimeter drains were permitted and installed. To facilitate groundwater
drawdown, field tile were spauid only 30 ft apart. This was accomplished
by incorporating a narrow (6 in.) disposal trench into the design along
with small diameter pressure distribution piping.
The narrow trench concept allowed for spacing of disposal trenches on 5 ft
centers rather than the usual 10 ft. Trench excavation was simplified by
using a trenching machine rather than a backhoe. Since fewer spoils were
generated during excavation than would normally be produced with standard
2 ft wide trenches, the entire system could be left open for pressure
testing of the effluent distribution system prior to final backfilling.
Construction of disposal trenches on the 5 ft spacing would have otherwise
been difficult from a practical standpoint.
WATER TABLE OBSERVATIONS
Groundwater monitoring was conducted during the months of December through
March of 1979-80 and 1980-81. Water levels were measured Inside the
perimeter drain and at points outside of the perimeter drain beyond the
drawdown influencs of the drain tile. Water levels were observed 1n 4 1n.
diameter, t>VC lined monitoring xells. Monitoring well dependability was
periodically confirmed with observations 1n fresh auger bores.
5-6
(106)
-------
DRAINAGE WATER QUALITY PARAMETERS
Two water quality samples were collected from monitoring points in the silt
trap, one upgradient and one downgradient (Figure 5-2). Samples were taken
on the same days water table observations were recorded.
Water quality parameters monitored were N03, total coliform bacteria and
fecal coliform bacteria. Nitrate was determined colorimetrically by a
cadmium reduction nethod (9). Bacterial analyses for total and fecal
coliform were conducted using a membrane filter technique (10). Total
fecal coliform densities were reported as log normalized means. Each
observation reflected the assumption that flows from inlets into the silt
trap were near equal in volume. ResuUs for each analysis were therefore
combined for each observation by averaging of the 2 numbers.
RESULTS AND DISCUSSION
WATER TABLE DRAWDOWN
Field tile perimeter drains in the disposal field area were effective in
producing groundwater drawdown (Table 5-1). Results were similar to those
obtained in adjacent agricultural lands where tile drains were designed and
installed on a maximum spacing of 70 ft according to SCS (11) recommend-
ations for effective drainage of these soils. Groundwater drawdown was
greater where a 6 ft tile depth was used. The relatively small drawdown
observed at System 4 was attributed to the influences of old field tile in
an adjacent field which maintained groundwater levels below 36 in. outside
the perimeter drain and disposal field. Soil mottling at this site
indicated that groundwater normally occurred above 24 in.
5-7
(107)
-------
Perimeter drains were installed with a minimum depth of 4 ft around
Systems 6 through 9 with a 10 ft separation distance between tile lines and
disposal trenches. Variations in relief resulted in portions of the
perimeter drain being deeper than the 4 ft minimum. Consequently, ground
water levels observed for Systems 7 and 9 were deeper than 4 ft. Ground-
water drawdown for System 7 was comparable to other systems even
though no gravel envelope was installed in the perimeter drain. Ground
water levels in the disposal field area of System 6 were high relative to
the other systems. The 33 in. mean value however is still well below the
24 in. minimum depth required under state rules (6).
TABLE 5-1. EFFECT OF TILE DRAINAGE ON GROUNDWATER LEVEL^1)
SYSTEM (Soil Texture) Groundwater Depth Draw Down
1.
2.
3.
4.
5.
6.
7.
a.
9.
(1)
ill
Min.
silty clay loam
silty clay loam
silt loam
silt loam(2)
silt loam
Min.
silt loam
silty clay loam (3)
clay loam ^'
loam
Observations taken December
Old field tile influence.
No gravel envelope.
Inside
(in.)
tile depth 6 ft
51
57
59
60
53
tile depth 4 ft
33
53
f 1 o o d e
56
through March,
5-8
(108)
Outside
(in.)
9
11
14
36
16
11
24
d
13
1980-81.
42
46
45
24
37
22
29
43
-------
System 8 was flooded by an old field tile which was intersected during
construction of the perimeter drain. The old line was excavated 20 ft
upslope from the point of intersection and backfilled. The first heavy
rains of the season caused water to surface from the line and run across
the disposal field nearly continuously. Groundwater levels were not
recorded in this system, but water quality samples were collected from
monitoring points in the silt trap to indicate performance under saturated
soil conditions.
Data for the performance of shallow (36 in. deep) perimeter drain systems
was unavailable at the time of this report. One system was influenced so
dramatically by older drainage tile in an adjacent field that no
groundwater was ever observed in the perimeter drain area. Performance
monitoring was, therefore, impossible.
TWO additional shallow perimeter drains with narrow disposal trenches were
installed but were not completed until after the monitoring season had
ended. Groundwater drawdown observations for one of these systems
indicated that the perimeter drain was effective in lowering water levels
in the disposal field area (data not shown). Further monitoring of these
systems would be very useful in determining potential as a cost-effective
alternative on poorly drained sites with shallow effective soil depth
and/or limited area.
DRAINAGE WATER QUALITY
Nitrate levels in monitored perimeter drain discharges were below the
5-9
(109)
-------
USPHS minimum drinking water standard of 10 mg/1. The disposal field for
System 7 did not receive septic tank effluent during the monitoring period
(Table 5-2). However, the system was monitored for groundwater drawdown
and drainage water was sampled for background. This system produced the
highest mean nitrate levels (Table 5-2) and suggested that the other
systems were not above background for this parameter. System 7 1s located
in a rural agricultural area and these nitrate levels were attributed to
fertilizer practices.
TABLE 5-2. EFFECT OF DISPOSAL TRENCHES ON TILE DRAINAGE WATER
System N03-N Total Coliform Fecal Coliform Observations^5)
•*i<1
1. 3.7
2. 0.6
3. 2.3(3)
4. 3.1
5. 4.1
5. 1.0
7. 5.0
3. 4.7(4)
9. 0.9
1) Arithmetic
2} Geometric
3) Septic sys
)
min.
446
1138
100
2843
3180
m1n.
3717
643
67892
93
mean.
mean.
tern unused.
tile depth 6 ft, setback 20 ft
56
83
10
60
934
tile depth 4 ft, setback 10 ft
74
18
4130
6
8
5
3
4
8
8
8
3
3
J4j Drainfield flooded.
Average value for samples from each of two Inlets on given date.
5-10
(110)
-------
Total and fecal coliform levels showed wider variation during the
monitoring period. Fecal coliform levels were largely within the 200
org/100 ml minimum required under Water Quality standards (12). Systems 5
and 8, however, showed relatively high mean values for these parameters.
System 8, as noted earlier in this discussion, was flooded during the
monitoring season. Conditions optimal for rapid saturated flow into the
perimeter drain were present because the disposal field was saturated.
Rahe et al., (4) showed that rapid translocation of organisms occurred
under saturated flow on hillside landscape positions. Although System 8
was nearly level, a hydraulic gradient was produced by drawdown to the
perimeter drain. This combination of factors presents an example of system
performance under conditions of saturated flow. Performance of System 8
was not satisfactory. The existing field tile will either be diverted
around the disposal field or be tied into the perimeter drain.
System 5 showed much lower fecal counts than the flooded system, but the
mean value for fecal coliform was considerably higher than the 200 org/100
ml minimum standard (Table 2). Hinh counts of fecal organisms were
characteristically obtained from one side of the perimeter drain only (data
not shown). Evidence of rodent activity was observed between the disposal
field and one side of the drainage system. "Short-circuiting" of effluent
through gopher burrows to the perimeter drain appeared to account for these
high fecal counts. Next season's monitoring will help determine whether
this type of phenomena can be expected to continue where it presently
exists and whether other systems will be affected. Reported fecal coliform
5-11
(ill)
-------
levels as high as 40,000 org/100 ml in urban storm runoff (13) and
seasonally high stream levels resulting from overloaded sewer plant
discharges (14) suggest that observed values for indicator organisms from
Systems 5 and 8 are not alarmingly high.
Drainage water from System 9 had very low mean values for the observed
parameters (Table 5-2). These results and those from System 6 indicate
that a 10 ft setback and 4 ft minimum perimeter drain depth provide
adequate zones of unsaturated soil for filtration and treatment of
effluent. Septic tank effluent was uniformly distributed throughout the
disposal field of System 9 via a low pressure piping system using small
diameter (2 in.) pipe. Pressure distribution may have been a contributing
factor in the good overall performance of the system. A more significant
factor, however, was probably dilution of effluent from the large volume of
groundwater flowing through this regional discharge area. These conditions
were not present at the other sites studied, where seasonal groundwater
with relatively low flow was more common.
CONCLUSIONS
Successful on-site treatment and disposal of septic tank effluent in wet
scils was obtained by surrounding disposal field areas with field tile.
Tile placed 6 ft deep lowered water tables more effectively than tile
placed 4 ft deep, but t^les placed at either depth lowered groundwater
sufficiently to prevent saturated soil conditions in disposal trench
areas. Vertical groundwater separation distances of as little as 9 in.
below disposal trench bottom and a horizontal setback of 10 ft between the
5-12
(112)
-------
perimeter drain and disposal trenches did not result in below standard
quality for drainage water. There was no apparent difference in drainage
water quality in perimeter drains setback either 10 or 20 ft from disposal
trenches. Observations on one system suggested that gravel envelopes in
perimeter drains may not be needed when drain tile are installed in soils
of the Woodburn series.
Perimeter drains installed around disposal fields did not adversely affect
drainage water quality relative to documented environmental problems, such
as urban runoff and point source discharges. Impact on receiving streams,
road ditches, and other discharge points should be considered, however,
outside of rural density areas.
Based 0" the performance cf systems utilizing 4 ft to 6 ft deep perimeter
drains, there appears to be good potential for the success of systems
designed with shallower (36 in. deep) perimeter drains on close spacings.
Pressure distribution of effluent for these systens may be a good design
precaution, particularly where coarse textured soils occur. In addition,
pressure dosing facilitates incorporation of a narrow trench design, since
concern regarding shock loads of effluent is alleviated. Application of
this concept may be useful in many situations, but the potential as a
cost-saving sand-filter alternative is particularly noteworthy.
5-13
(113)
-------
REFERENCES
1 State Mater Resources Board, 1969. Oregon's Long-Range Requirements
for Water. General Soil Map Report with Irrigable Areas.
Willamette Drainage Basin. Appendix I - 2, 131p.
2 Pacific Northwest River Basin Commission. 1969. Willamette Basin
Comprehensive Study. Willamette Basin Task Force, Appendix G,
P II - 50.
3 Reneau, R. B., Jr. 1978. Influence of Artificial Drainage on
Penetration of Coliform Bacteria from Septic Tank Effluents into
Wet Tile Drained Soils. J. Environ. Qua!. 7: 23-30.
*» Rahe, T. M., C. Hagedorn, E. L. McCoy and G. F. Kling. 1978.
Transport of ."itfbiotic-resistant Eschericia Coli Through Western
Oregon Hillslcpe Soils Under Conditions of Saturated Flow. J.
Environ. Qual. 7: 487-494.
5 Hagedorn, C., E. L. McCoy, and T. M. Rahe. 1981. The Potential for
Groundwater Contamination From Septic Effluents. J. Environ.
Qual. 10: 1-8.
6 Oregon Department of Environmental Quality. 1981. On-site Sewage
Disposal Rules. State of Oregon Administrative Rules, Chapter 340,
Division 71-220. pg. 22-23.
7 Public Health Service. 1972, Manual of Septic-Tank Practice. U.S.
Department of Health, Education, and Welfare, Health Services and
Mental Health Administration. 92p.
^ Balster, C. A. and R. B. Parsons. 1968. Geomorphology and Soils of
the Willamette Valley Oregon, Oregon State University Agr. Exper.
Sta. Special Report 265, 31p. illus.
9 U.S. Environmental Protection Agency. 1979. Nitrogen, Nitrite, p.
353.2-1. Methods of Chemical Analysis of Waste and Water. Off. of
Technol. Transf., Washington, D.C.
10 American Public Health Association. 1971. Standard Methods for the
Examination of Water and Waste Water. 13th ed. APHA, New York.
11 USDA Soil Conservation Service. 1977. Subsurface Drainage, p. 46-56.
In Willamette Valley Drainage Guide. Soil Conservation Service,
Portland, Oregon.
12 Oregon Department of Environmental Quality. 1980. Regulations
Relating to Water Quality Control in Oregon. State of Oregon
Administrative Rules, Chapter 340, Division 41-445. p. 16.
5-14
(114)
-------
13 Geldrelch, E. E., L. C. Best, B. A. Kenner, and D. J. Van Oonsel.
1968. The Bacteriological Aspects of Stormwater Pollution. J.
Water Pollut. Control Fed. 40: 1861-1872.
^ Mid-Willamette Valley Council of Governments. 1980. A report prepared
for the U.S. E.P.A. and Oregon DEQ. (Unpublished).
G0653 5-15
(115)
-------
CHAPTER 6
SEEPAGE TRENCHES IN SOILS WITH SLOW AND VERY SLOW PERMEABILITIES
There are over 200,000 acres of fine-textured soils in Oregon with slopes
between 3 and 20* (9,10). These soils are slowly and very slowly
permeable and exhibit high shrink-swell characteristics on wetting and
drying. Standard soil absorption systems are not permitted in these soils
under current health codes (2,4) because of a history of failures caused by
internal soil movement and percolation rates of 300 minutes/in, or less.
Changes in soil moisture content cause movement of soil which disrupts
disposal trenches and distribution piping (8). In addition, very slow
percolation rates cause ponding of effluent 1n disposal trenches and
surfacing of partially treated yewage during periods of prolonged.
rainfall.
On-site sewage disposal is rapidly becoming recognized as a long-term and
more cost-effective alternative to sewage collection and treatment systems
in rural and semirural areas. However, construction of standard on-s1te
sewage disposal systems for new housing and for repair of falling systems
is not justified in soil areas where experience has demonstrated that these
systems will not function properly. A need, therefore, exists to develop
suitable alternatives to allow development of nonagrlcultural land,'not
currently suitable for on-site waste disposal, and to repair 'falling
systems that are causing a public health hazard.
6-1
(117) Preceding page blank
-------
This study was undertaken to determine 1f either large dlsposai fields
using standard disposal trenches or disposal fields using seepage trenches
could be used to overcome limitations of very slow percolation rates and
the disruptive action of internal soil movement.
METHODS AND MATERIALS
SITE DESCRIPTION
Nine systems were installed in soils of the Carney series in Jackson County
and 6 systems were installed in soils of the Oxbow and Tub series 1n Grant
County. The Carney series (5) consists of moderately well drained, fine
textured soils formed 1n clayey pedlsediments derived from volcanic tuffs
and breccias. They have high shrink-swell potential and very slow per-
meability (less than 0.06 1n./hr). The Oxbow (7) and Tub (6) series
consist of well-drained gravelly and cobbly soils formed 1n old colluvlum
and sediments. Surface horizons are moderately fine textured and subsoils
are fine textured. These soils have slow permeability (0.20 to
0.06 1n./hr). Carney soils occur at elevations of 1200 to 2500 ft on
slopes that range between 10 and 20%. Oxbox and Tub soils occur at
elevations of 2700 to 3500 ft on slopes that range between 3 and 12t.
Annual precipitation ranges from 15 to 25 1n. at sites in Jackson County
and from 11 to 15 1n. at sites In Grant County. Most of the precipitation
occurs during the winter and early spring.
SYSTEM DESIGN
Each system consisted of a standard 1000 gallon septic tank, a series of
drop structures, and yravlty-fed disposal or seepage trenches. Disposal
6-2
(118)
-------
trenches were 2 ft wide and 2 ft deep with 4 in. perforated piping bedded
in 12 in. of gravel and covered with 12 in. of native :o1l.
This design was subsequently modified to use seepage trenches installed 36
to 48 in. deep. Thickness of gravel was 24 in. and thickness of soil
backfill was 12 to 24 in. This modification was made to increase the
storage capacity, increase the absorptive surface, and increase the
hydraulic head in the seepage trench. In addition, deeper excavation
resulted in removal of clay to sufficient depth that the hazard of
disruption of trenches and distribution piping was eliminated.
System sizes varied from 600 to 3000 ft2 effective sidewall absorption
area. All construction was done during the summer to reduce the hazard of
smearing of trench bottoms and sidewalls, but unfortunately 1t was
impossible to eliminate smearing. Meters were Installed on water service
lines to each residence to record water use.
SYSTEM MONITORING
Water depths in disposal and seepage trenches were monitored only during
the wet season (November through May) of 1977-78, 1978-79, 1979-80 and
1980-81. Water us3 was monitored during this same period.
Performance of each system was evaluated by comparing mean water depth 1n
each trench, during the winter months, with the height of the sidewall
absorption area. For example, a system with a mean water depth of 12 1n.
and a sldewall absorption height of 24 1n. (24 1n. of gravel filter
6-3
(119)
-------
material in the trench) had a performance of 50% of capacity.
RESULTS
All of the soil absorption systems installed in Grant County functioned
below 35% of capacity (Table 1). In addition, there were no surface
failures during periods of heavy rainfall.
TABLE 6-1. DISPOSAL TRENCHES^1) IN SOILS WITH SLOW PERMEABILITY
SIDEWALL
SYSTEM ABSORPTION AREA SEWAGE FLOW PERFORMANCE OBSERVATIONS
1
2
3
4
5
6
2
(ft )
(GRANT
600
900
900
900
900
1500
(gpd) (% Capacity) (Number)
COUNTY - 15 in. PRECIPITATION OR LESS)
106 14
185 17
123 5
158 13
33
5
6
9
7
7
6
4
(1) Disposal trenches were 24 in. deep with 12 1n. of filter
material (gravel).
System performance varied considerably in Jackson County. Systems using
24-in. disposal trenches did not function satisfactorily, but systems with
6-4
(120)
-------
seepage trenches 36 1n. deep or more functioned properly. Systems 1, 2, 3,
and 4 utilized more than 70* of the system capacity during the wet months
(Table 2). System 1 fai"!ed more than 75% of this period. The system
TABLE 6-2. DISPOSAL TRENCHES^1) IN SOILS WITH VERY SLOW PERMEABILITY
SIDEWALL
SYSTEM
ABSORPTION AREA
SEWAGE FLOW
(ft2) (gpd)
JACKSON COUNTY 15
1
2
3
4
5
1600
900
2025
1600
1200
239
126
175
162
198
PERFORMANCE
OBSERVATIONS
(% Capacity) (Number)
in. to 25 in. PRECIPITATION
93(2)
89
72(3)
73(4)
54
9
13
14
20
23
(1) Disposal trenches were 24 in. deep with 12 in. of filter material
(gravel).
(2) System 1 failed 75* of the time.
(3) System 3 failed during a period of heavy rainfall in January, 1980,
and March, 1980.
(4) System 4 failed during periods of heavy rainfall in December, 1977,
March, 1980 and April, 1981.
was repaired in April 1979 when an evapotranspiration absorption bed 6 ft
wide, 120 ft long, and 2 ft deep was added below the last disposal trench.
The entire system failed again May 10, 1979 and continued to do so until
the end of the monitoring period. System 3 failed in January 1980 and
March 1980 following periods of heavy rainfall and System 4 failed in
6-5
(121)
-------
December 1977, March 1980, and April 1981 following periods of heavy
rainfall. System 2 performed at 89* of capacity during the wet period but
no surface failures occurred.
Soil absorption systems using seepage trenches 36 in. deep or more
functioned satisfactorily during the wet winter months with no surface
failures. Systems 1, 3, and 4 used less than 5* of system capacity
(Table 3). System 2 used 63% of system capacity.
TABLE 6-3. SEEPAGES TRENCHES^1) IN SOILS WITH VERY SLOW PERMEABILITY
SYSTEM
1
2
3
4
SIDEWALL
ABSORPTION AREA SEWAGE FLOW
2
(ft )
3000
2400
1300
1200
(gpd)
(JACKSON COUNTY 15
136
186
31
150
PERFORMANCE
(% Capacity)
in. - 25 in.
5
63
5
5
OBSERVATIONS
(Number)
PRECIPITATION
24
26
6
6
(1) Trench depth varied from 36 to 48 in. with 24 in. of filter material
(gravel). System 2 had 12 in, of soil backfill, and Systems 1, 3 and
4 had 24 in. of soil backfill.
6-6
(122)
-------
DISCUSSION
Satisfactory performance of soil absorption systems in Grant County
(Table 1) was attributed to soil absorption system size, low annual
precipitation, and soil permeability rates (6,7) sufficient to accept
2
effluent without surfacing. Systems were sized at 0.5 gal/ft, of side-
wall absorption area per day, but measured sewage loading rates (Table 1)
were well below this. Annual precipitation was less than 15 in., and did
not interfere with the soils capacity to absorb effluent.
Failures in Jackson County were caused mainl.y by infiltration of surface
water, very slow soil permeability rates (a), and use of disposal trenches
too shallow to establish equilibrium hydraulic heads. System 2 (Table«2)
was monitored during December, 1977 and January and February, 1978 prior to
completion of the house and use of the septic tank and soil absorption
system. Observation of monitoring wells showed that 97% (data not shown)
of this system was filled with water. The first disposal trench contained
11 in. of water, trench 2 contained 12 in. of water, and the last trench
had water standing 4 in. from the soil surface. This system was placed
into use in March of 1978 and was near failure during March, November, and
December of 1978; February, March, April, November, and December 1979;
February, March, April, November, and December 1980; and February, March,
and April 1981. System 3 and System 4 also had a history of failure as did
System 1 in spite of enlargement of this system in April, 1979. System 5
was near failure during December, 1977; January, February, and March, 1978;
6-7
(123)
-------
and February 1979, but functioned satisfactorily during the remainder of
the monitoring period using only 4 of the 6 disposal trenches.
All of these failures were associated with periods of heavy rainfall when
runoff water infiltrated into disposal trenches. These soils were dry when
disposal trenches were installed. Consequently, much of the soil was in
the form of extremely hard clods. When disposal trenches were backfilled
with this cloddy soil material, a rough, porous backfill was formed over
each disposal trench. Surface runoff, from the first heavy rains, rapidly
infiltrated through this backfill and raised water levels in all disposal
trenches. The backfill subsequently settled and formed depressional areas
on the soil surface temporarily ponding water which ultimately infiltrated
into disposal trenches. Disposal trenches were tco shallow to allow water
levels to rise sufficiently to drive the effluent through the very slowly
permeable soils before surface failures occurred.
Soil absorption systems using seepage trenches 36 in. deep or more
functioned satisfactorily because of a combination of increased absorptive
surface, increased hydraulic head, mechanical compaction of trench
backfill, and in some systems more rapid soil permeability rates with
depth. Seepage trenches theoretically can function properly in very slowly
permeable soils if the absorptive area is adequately large (1). Seepage
trenches had twice as much sidewall absorptive surface as disposal
trenches. The effluent storage capacity was also doubled. In addition,
trenches were deep enough to allow higher hydraulic gradients. Observation
6-8
(124)
-------
of System 2 (Table 3, data not shown) showed that about 21 in. of effluent
occurred in the first trench and about 13 in. of water occurred in the
lower three trenches. Effluent had to rise to 24 in. in this system to
flow through the drop box into the next lowest line. Inspection of drop
boxes showed that only the first seepage trench of this system contained
sewage. Surface water infiltrated into the lower trenches of the system
during the first heavy rains the same way it did into systems using
disposal trenches because the backfill was loose and cloddy and only 12
in. thick. Water and sewage percolated through these soils very slowly
because of very slow permeability rates. However, as sewage levels rose in
the first trench, the effluent acceptance rate increased in response to the
increased hydraulic gradient (3) and equilibrium was apparently reached
with a hydraulic head of about 21 in. Sewage remained at this level in the
first trench and water remained at about 12 to 15 in. in the lower trenches
during the wet winter season. Water levels dropped and all but the first
trench became desaturated during the dry summer season.
Systems 1, 3, and 4 (Table 3) were dry most of the time, except for the
first line. This was true even in the winter season, during arM
immediately after periods of intense and prolonged rainfall. Infiltration
was minimized by mounding backfill over the seepage trenches and
mechanically compacting to a final thickness of 24 in. In addition,
trenches in Systems 1 and 4 were excavated into calcareous substratum that
was more permeable. System 3 had a very low daily sewage flow.
6-9
(125)
-------
CONCLUSIONS
Soil absorption systems consisting of 24 in. deep disposal trenches
installed in fine-textured soils functioned properly in Grant County where
annual precipitation was 15 in. or less. Twenty-four in. disposal trenches
were not satisfactory in Jackson County where rainfall exceeded 15 in.
Surface failures were common during periods of prolonged rainfall.
Seepage trendies 36 in. deep or more functioned satisfactorily where
annual precipitation did not exceed 25 in. Satisfactory performance
was attributed to a combination of Increased absorptive surface, increased
hydraulic head in trenches, proper trench backfill, and in some systems
more permeable soil with depth, or very low daily sewage flow.
None of the disposal trenches and some cf the seepage trenches were not
backfilled properly because of the hard cloddy naturt. of the dry clay
soils. As a result, infiltration of surface water was a problem in these
systems. Soil backfill should be mounded over trenches and mechanically
compacted, and diversion ditches should be constructed above each system to
intercept surface waters.
6-10
(126)
-------
10
REFERENCES
1 Bouma, J. 1975. Innovative On-Site Soil Disposal and Treatment
Systtns for Septic Tank Effluent. In: Proceedings of the National
Home Sewage Disposal Symposium. American Society of Agricultural
Engineers, St. Joseph, Michigan, pp. 152-162.
2 Department of Environmental Quality, 1975. Chapter 340, Division 71,
Standards for Subsurface and Alternate Sewage and Nonwater-Carried
Waste ulsposal, Revised March 13, 1981. State of Oregon.
3 Laak, R. ano K. A. Healy, 1975. Design of Leaching Field Systems.
lournp.: of Environmental Health, Volume 30, No. 3 pp. 194-197.
4 Public Health Service, 1972. Manual of Septic-Tank Practice. U.S.
Department of Health, Education, and Welfare, Public Health
Service, Health Services and Mental Health Administration, p. 92.
5 Soil Conservation Service, 1972. Soil Interpretations for Oregon,
OR-SOILS-1 Carney Series, USDA, Soil Conservation Service,
Portland, Oregon.
6 Soil Conservation Service, 1973. Soil Interpretations for Oregon, OR-
SOILS-1, Tub Series, USDA, Soil Conservation Service, Portland,
Oregon.
7 Soil Conservation Service, 1974. Soil Interpretations for Oreaon. OR-
SOILS-1, Oxbow Series, USDA, Soil Conservation Service, Portland,
Oregon.
8 Soil Survey Staff, 1975. Soil Taxonomy, a Basic System of Soil
Classification for Making and Interpreting Soil Surveys, USDA Soil
Conservation Service, Agriculture Handbook No. 436, p. 754.
9 State Water Resources Board, 1969. Oregon's Long-Range Requirements
for Water. General Soil Map Report with Irrigated Areas. John Day
Drainage Basin, Appendix 1-6, p. 101.
te Water Resources Board, 1969. Oregon's Long-Range Requirements
for Water. General Soil Map Report with Irrigated Areas. Rogue
Drainage Basin, Appendix 1-15, p. 69.
G0653.1 6-11
(127)
-------
CHAPTER 7
SEEPAGE TRENCHES ON STEEP SLOPES
Greater then 350,000 acres of deep, well-drained soils with slopes
exceeding 25% occur in Oregon, principally west of the Cascades. Standard
disposal field construction was prohibited on these sites in the past, due
to concern for effluent seepage downslope. Practical considerations
regarding equipment operation and construction under these conditions
discouraged regulators from considering whether on-site disposal was
actually feasible.
Slope steepness, however, does not necessarily limit satisfactory
performance of septic tank effluent disposal fields. Where other site
conditions such as soil depth, permeability, and drainage are favorable,
deep disposal trenches (seepage trenches) may provide adequate treatment
and disposal. This study was conducted to determine if seepage trenches
would function satisfactorily when installed 1n suitable soils on slopes
in excess of 25%.
METHODS
Four seepage trench disposal fields were installed on sites with slopes
ranging from 30 to 45X. Soils at each site had a minimum 60 in. effective
civ»pth, were well to moderately well drained, and occurred on planar or
convex slopes. Seepage trench design (Figure 7-1) consisted of 2 ft wide,
level bottom trenches installed 30 to 36 in. deep. An 18 in. gravel
envelope was placed in the trench bottom with a 4 in. PVC distribution
7-1
U29) Preceding page blank
-------
Septic Tank
House
Seepage Trench
FIGURE 7-1. STEEP SLOPE SYSTEM PLAN AND DETAIL OF SEEPAGE TRENCH
-------
pipe located in the upper 6 1n. Hand labor was required to varying degrees
in trench excavation, gravel placement, and backfilling due to equipment
operating limitations. Three to four hundred linear ft of seepage trench
2
were installed per system providing up to 1200 ft of effective sidewall
seepage area. Systems were conservatively oversized to alleviate concern
about performance.
RESULTS AND DISCUSSION
Seepage trench disposal fields installed on slopes up to 45% performed
satisfactorily (Table 7-1). The performance rating listed in the table
is based on observed in-trench liquid levels. The percentages were based
on the amount of sidewall seepage area being utilized. The data indicated
that slope steepness in itself was not a limitation to successful treatment
and disposal of effluent. In addition, no seepage or surfacing of effluent
occurred downslope in any of the systems. Since other site and soil
characteristics were favorable, this was not unexpected.
Calculated performance ratings and monitoring observations suggested that
these systems were greatly oversized. Current Oregon Rules for on-site
waste disposal require a minimum of 225 linear ft of disposal trench
(75 ft/150 gal sewage) with these soil conditions with no slope
limitation. Seepage trenches with 50% greater effective seepage area
(18 in. gravel envelope vs. 12 in.) and a smaller disposal field .in the
order of 150 linear ft (450 ft2) appears reasonable. Tne smaller system
would reduce construction costs particularly where hand labor is involved.
7-3
(131)
-------
TABLE 7-1. STEEP SLOPE SYSTEMS
SYSTEM
1. Mel cher
2. Bergstrom
3. Bantilan
4. Nelson
SIZE FLOW
(ft2) (gpd)
900 131
1080 122
138
1200 300
PERFORMANCE
(% capacity)
0
0
20
6
CONCLUSION
Seepage trenches functioned satisfactorily on slopes up to 45%. All of the
disposal fields were significantly larger than necessary for satisfactory
performance. A minimum effective soil depth of 60 in. was not a necessary
criteria for system success. No surfacing of effluent occurred downslope
from any systems. Operation of excavating equipment on slopes over 30% is
difficult and may be impossible on some sites.
Future experimental systems on steep slopes will be installed where minimum
effective soil depth 1s 42 in. Seepage trenches will be sized at 50 linear
ft per 150 gal projected daily flow.
G0184.A 7.4
(132)
-------
CHAPTER 8
DISPOSAL TRENCHES IN SOIL SHALLOW TO WEATHERED AND FRACTURED BEDROCK
Shallow soil depth is a common site limitation for on-s1te sewage disposal
systems in Oregon. The primary concern was that septic tank effluent would
not be adequately treated and absorbed where shallow soil occurred. The
current Oregon on-iite sewage disposal rules required a 30 in. minimum
effective soil depth.
Weathered bedrock ur saprolite often has desirable characteristics for
treatment and disposal of septic tank effluent. Although structural
properties are different than soil and organic matter contents are lower,
permeability characteristics are often favorable. The introduction of
nutrients from the household waste stream is likely to stimulate biological
activity and subsequent treatment in this medium much the same as takes
place in soil material.
Several million acres of soils shallow to weathered bedrock exist
throughout the state. These areas are of special Interest where they occur
in foothills adjacent to agricultural land. Since preservation of deeper,
more arable land is a designated land use. goal, development and use of
shallow soils for on-site sewage disposal is increasingly attractive.
An additional consideration is the validity of denying shallow soil s,1tes
from a public health standpoint. Characteristically, shallow soils 1n
8-1
U33)
-------
Western Oregon are associated with upland landscape positions. Usable
groundwater 1s typically 100 to 300 ft deep so concern regarding lack of
treatment by permeable weathered rock may not be justified. Variable
topography often limits development density, and this factor may further
diminish valid concern regarding groundwater protection.
This study was Initiated to evaluate performance of disposal fields 1n
soils shallow to weathered bedrock.
METHODS
Seven on-site disposal systems were installed on upland sites with shallow
effective soil depth in Western Oregon. Typically soils were classified as
Philomath or Dlxonville series 1n Soil Conservation Service surveys.
Effective soil depth varied from 29 1n. to as little as 12 1n., with
underlying weathered bedrock of volcanic or sedimentary origin.
Soil absorption fields consisted of gravity-fed disposal trenches 2 ft deep
and 2 ft wide with 4 in. perforated piping bedded 1n 12 1n. of gravel
(Figure 8-1). Systems were conservatively oversized with up to 600 linear
ft of disposal field being Installed to satisfy Initial concerns regarding
permeability. (At the time these systems were designed and Installed, on-
site permits were commonly denied based on the assumption that the
weathered substratum was restrictive or Impermeable.)
An additional system was Installed 1n Malhuer County 1n Eastern Oregon
where rainfall fs less than 10 in. per year. Effective soil depth wai
8-2
(134)
-------
House
Septic Tank
t— CO
04 I
U1 tj
Diposal Trench
Drop Box
FIGURE 8-1. SAPROLITE SYSTEM PLAN AND DETAIL OF DISPOSAL TRENCH
-------
limited to 20 in. by a duripan. The pan was fractured during trench
construction. Semi-consolidated bedrock (unweathered due to arid climatic
conditions) at shallow depths is also common.
Water levels in disposal trenches were monitored in 4 in. in-trench
monitoring wells or 2 in. in-trench piezometers. On sloping sites,
downgradient monitoring wells were installed but sampling was found to be
generally impractical since almc;t no water collected in them on thsse well
drained sites.
Performance ratings compared the mean water level in each disposal trench
during the wet season to the height of the sidewall absorption area.
RESULTS AND DISCUSSION
Monitoring data indicated generally satisfactory performance. Table 8-1
lists sites studied and compares system size, household water use and
performance ratings.
System 6 performed poorly during the monitoring (wet) season. Underlying
geologic material on the site was evidently less permeable than predicted.
Seasonal perched groundwater Infiltration may have been partially
responsible for the high liquid levels recorded in the disposal field. A
groundwater interceptor was Installed upslope, but further measures may be
needed. Four out of the 6 disposal trenches were dry or nearly dry 9
months of the year. No water supplies or property are threatened down-
gradient on this site so public health effects were not a concern.
8-4
(136)
-------
TABLE 8-1. PERFORMANCE OF DISPOSAL TRENCHES IN SOILS SHALLOW TO WEATHERED
BEDROCK (SAPROLITE).
SYSTEM DISPOSAL FIELD SIZE WATER USE PERFORMANCE
1.
2.
3.
4.
5.
6.
7.
(Cameron)
(Gibbs)
(Liming)
(Jager)
(Byers)
(Escalera)
(Eager)
Mean
(ft^sidewall area)
1200
1200
1280
1210
800
900
1208
TO~3T
(gal/day)
79-80
-. * .
175
298
247
185
196
144
T5J
80-81
242
94
166
-
-
189
T79
(% capacity)
79-80 80-81
35
32
21
19
0
89
0
25
40
8
14
0
88
7
26
Other systems performed at much less than 50% of capacity during the
monitoring season suggesting that they were larger than necessary.
Groundwater was not encountered in any downgradient monitoring wells. This
suggested that net downward movement of effluent occurred under the
disposal field rather than downslope with the exception of System 6.
Extreme depth of domestic wells in the area and sparse population density
suggested that groundwater sampling and concern about groundwater
contamination were unwarranted.
No water was observed in disposal trenches in the system in Eastern Oregon
(data not shown). Although this system was installed in subsoil that was
slowly permeable, the lack of seasonal moisture indicated that household
wastewater constituted the only source of hydraulic loading. This system
was evidently larger than necessary with 300 linear ft of disposal trench.
However, the conservative size may have acted as a buffer against shock
loading and insured longer system life.
8-5
(137)
-------
CONCLUSIONS AND RECOMHENDATIONS
Shallow effective soil depth is not an essential limiting factor for
on-site sewage disposal. Weathered bedrock allowed effective absorption
and disposal of effluent in Western Oregon upland soils such as Dixonville
and Philomath. Effective treatment or attenuation of effluent components
was probable but difficult to verify due to sampling limitations. Depth of
groundwater and low development density suggested that groundwater
contamination was not a concern.
Effective soil depth was even less a concern in arid counties in Eastern
Oregon. Slow substratum permeability was offset by adequate sizing of
disposal fields.
Rules should be revised to allow installation of disposal trenches in well
drained soils that are shallow to weathered bedrock (saprolite) and
duripans where other site characteristics are favorable.
G0184.D 8-6
(138)
-------
CHAPTER 9
PRESSURE DISTRIBUTION SYSTEMS IN SOILS WITH SHALLOW GROUNDWATER
Conventionally designed septic tank effluent disposal fields rely on a zone
of unsaturated aerobic soil to provide treatment and filtration. Where
shallow groundwater occurs the depth of unsaturated soil beneath disposal
field trenches may be inadequate. This is particularly true in soils with
moderate to very rapid permeability where gravity distribution methods may
create effluent saturation zones in the first few feet of disposal
trenches.
A possible means of preventing bacterial contamination of groundwater by
saturated flow ("shortcircuiting") of incompletely treated septic t-r.^
effluent, may be through control 11 rig effluent dosing rates and providing
uniform effluent distribution throughout the entire disposal field using a
low pressure distribution system. Effluent pumped through small diameter
plastic piping perforated by 1/8 in. orifices can be dosed uniformly
throughout an entire soil absorption system. The level of effluent
treatment and filtration should vary witii the thickness and texture of
unsaturated soil above groundwater.
The objective of this study was to test several vertical separation
distances between the bottom of disposal trenches and groundwater where
pressure distribution systems were installed. The impact of effluent on
9-1
(139)
-------
groundwater quality was monitored and assessed. Proper sizing, design, and
overall performance of low pressure distribution systems were chacterized.
METHODS
Effluent disposal systems fed by low pressure distribution were constructed
at 6 sites. Soil characteristics at 3 system installation sites corre-
sponded with the broad textural catagory defined in DEQ On-Site Sewage
Disposal Rules as Soil Group A (sand, loamy sand, and sandy loam). These
systems were constructed in Klamath and Jackson counties. System design
(Figure 9-1) consisted of 240 linear ft of 2 x 2 ft disposal trench with
2 in. diameter pressure distribution piping bedded in 12 in. of gravel.
Three additional systems were installed at sites with soil corresponding to
Soil Group B (silt loam, loam, and clay loam) in Union and Jackson Counties
to assess differences in treatment and filtration through finer textured
material. Systems were similar to those installed in coarser soils.
Total and fecal coliform, nitrate-nitrogen and groundwater levels were
monitored via shallow well groundwater sampling upgradient and
downgradient from the systems. Samples were taken December through
April 1980-81. One of the 3 systems for each soil group was surrounded
by a perimeter drain (see Section C for design specifications) which
served a dual purpose of controlling groundwater level and insuring capture
of effluent contaminants which could enter the saturated zone.
9-2
(140)
-------
House
Dosing Tank-
Septic Tank
2" Pressure Pipe
Diposal Trench
FIGURE 9-1. LOW PRESSURE DISTRIBUTION SYSTEM PLAN AND DETAIL OF DISPOSAL TRENCH
-------
The need for pressure distribution to achieve equal distribution and
acceptable treatment levels in medium textured (Soil Group B) soil was
considered. Results from a system with gravity fed trenches surrounded by
a perimeter drain (Chapter 5) were compared to systems with pressure
distribution trenches to determine the effect of soil texture and
distribution technique on effluent treatment and absorption.
RESULTS AND DISCUSSION
Data collected indicated that the systems studied did not have an adverse
impact on groundwater where adequate separation distances from disposal
trench bottom were maintained (Table 9-1). Groundwater contamination was
apparent in Soil Group B at System 4. Mean groundwater levels were 10 in.
higher than predicted by soil characteristics (mottling) observed during
the initial site evaluation. As a result, little separation between trench
bottom and groundwater was present during the monitoring period. Effluent
drained through the thin (2 in.) layer of unsaturated soil almost directly
into groundwater. Downgradient water samples indicated considerable
contamination by total and fecal coliform when compared to background
levels collected from upgradient wells.
Other systems studied produced more satisfactory results. Where reasonable
separation distances were maintained, mean fecal coliform levels were less
than 100 org/100 ml. These values were comparable to or less than
background levels. Downgradient samples collected at Systems 2 and 3
actually showed lower values than background for this parameter. Higher
total coliform levels from Systems 1 and 5 may not have been related to
9-4
(142)
-------
effluent, disposal fields. Lack of high corresponding fecal coliform levels
for those systems suggested total coliform contamination could have
resulted from some other source such as animal manure.
Table 9-1. MEAN BACKGROUND AND DOWNGRADIENT GROUNDWATER QUALITY FOR
PRESSURIZED EFFLUENT DISPOSAL SYSTEMS.
System
1 (a)
(b)
2 (a)
(b)
3 (a)
(b)
4 (a)
(b)
5 (a)
(b)
6 (a)
(b)
7 (a)
(b)
FOOTNOTES
(a
(b
(1
Separation Distance NH4-N N03-N Total C Fecal C
(inches) mg/ljjj #0rg/100mlj_|_
Soil Group A
29 16.3 0.2 10,488 100
0.5 1.1 177 17
39 2.3 0.5 1,000 22
0.1 14.6 1,000 100
48 0.1 1.8 149 10
0.1 1.8 100 12.5
Soil Group B
2 0.02 6,468 1229
0.03 234 17
24 0.6 2,928 70.6
1.2 246 61.8
32 0.9 93 6
15 0.9 11,441 38.9
1.0 7,032 67.9
Downgradient,
Upgradient
Arithmetic mean
#0bb.
2
5
4
4
6
5
4
4
5
5
3
6
6
(2) Geometric mean
9-5
(143)
-------
Data for Systems 2 and 3 in Soil Group A indicated no groundwater impact
where a 39 in. to 48 in. separation between trenches and groundwater was
maintained. These results suggested that low pressure disposal systems
offer an advantage in Soil Group A where gravity systems might create local
saturated flow and subsequent groundwater contamination.
Systems 5 and 6 in Soil Group B performed well when only 24 in. and 32 in.,
respectively, separation distances between trenches and groundwater were
maintained. System 6 had lower mean fecal coliform levels than background
for any of the other systems. Groundwater dilution due to a relatively
high flow rate through the area may partially account for observed values.
Nonetheless, performance indicated that system installation, where these
site conditions exi:t, was feasible.
Since permeabilities in Soil Group B are likely to be slower, 1t is
conceivable that equal distribution throughout the disposal trenches could
be achieved by gravity flow. Data for performance of conventional
gravity distribution trenches with respect to required separation
distances are not available. The assumption that 4 ft of unsaturated
soil is necessary for effluent treatment and filtration is made in Oregon
on-site sewage disposal rules.
Comparison of data from pressurized systems with data from System 7
(Table 9-1) which had gravity distribution, indicated pressure
distribution may not be necessary for adequate system performance. Even
though separation distances were less (15 in.) for System 7, fecal coliform
9-6
(144)
-------
levels were comparable to those obtained from pressurized systems Installed
in similar soils. This comparison was not anticipated at the onset of the
program, so similar relationships for Soil Group A were not included in the
experimental design. However, experience with groundwater contamination
from gravity systems in coarse textured soils suggested that pressure
distribution was probably more effective.
CONCLUSIONS AND RECOMMENDATIONS
Pressurized effluent disposal fields offered an advantage in obtaining
equal distribution of effluent in moderately coarse to coarse textured
soils where potential groundwater contamination was of concern. Controlled
application rates and regulated dosing cycles prevented rapid saturated
flow into groundwater from localized areas in the disposal field. The
resulting treatment and filtration of effluent created little or no
groundwater contamination where a separation distance of at least 30 1n.
was maintained.
The advantage of pressure distribution in medium and finer textured soil
material (Soil Group B) was less obvious. Where well developed soil
profiles occurred, pressure distribution might prevent shortclrcuiting of
effluent through macropores and structural voids. Where soil structure was
more weakly expressed or undeveloped, equal distribution may take place 1n
a gravity flow system. In addition, retention and treatment of potential
contaminants in the unsaturated zone would be greater for medium and fine
textured soil due to relatively slow hydraulic conductivity regardless of
distribution technique.
G0184.C 9-7
(145)
-------
CHAPTER 10
EVAPOTRANSPIRATION SYSTEMS
There are several million acres of soil in semi arid and arid regions of
Central and Eastern Oregon. These soils are not suitable for installation
of standard subsurface treatment and disposal systems because of shallow
depth, very slow permeability, or high groundwater tables. Non-discharg-
ing evapotranspiration (ET) beds appeared to be an appealing alternative.
This study was undertaken to determine if evapotranspiration beds could be
used to overcome these soil limitations.
METHODS
Sixteen Armon Sysi,a.;s of Oregon, Inc. (evapotranspiration beds) were
installed in Jackson County and one non-Armon ET system was installed in
Baker County. Potential evapotranspiration exceeds precipitation by more
than 10 in. in areas of these 2 counties where ET systems were Installed.
The Armon ET system consisted of a uniquely constructed downflowing two-
compartment fiberglass septic tank. Effluent discharged through the bottom
and flowed up through gravel surrounding the outside of the tank Into the
ET bed lined with a 4 mil plastic Uner. The tank was located 1n the
center of the bed. The ET bed was 36 in. deep and contained 12 1n. of
3/4 to 2-1/2 1n. drainfleld rock covered by 24 1n. of sand. The beds were
crowned with a slope of 3X. Bed sizes varied from 1200 to 3000 ft2.
10-1
Preceding page blank
-------
One monitoring well was located in the center of the bed adjacent to the
septic tank. Two underdrains were installed beneath the ET bed and
connected in a V-pattern to a monitoring well located outside of fhe bed.
The non-Armon ET bed was 30 in. deep and contained one ft of 3/4 to
2-1/2 in. drain-rock covered by 18 in. of silt loam. The ET bed was lined
with a 20 mil factory welded PVC liner. Bed size was 7500 ft2 of surface
area. One monitoring well was located inside the bed and one was located
outside the bed and connected to an underdrain to check the integrity of
the liner.
Water levels, sewage flow, fecal coliform, and chloride were monitored
once per month during the winter and spring month? from January 1977 to
May 1979.
RESULTS AND DISCUSSION
Thirteen Armon ET beds in Jackson County showed evidence of leakage. High
fecal coliform counts occurred in monitoring wells immediately outside of
the beds. Chloride concentration failed to build up inside of the beds,
but was inversely correlated to rainfall. waiter levels in the beds
fluctuated in response to precipitation and free water in the surrounding
soils. Most of these beds were installed in well and moderately well
drained soils and water levels dropped rapidly inside and outside of beds
when periods of heavy precipitation terminated. As a result, leakage of
effluent did not create a potential health hazard because it was absorbed
and treated in surrounding soil.
10-2
(148)
-------
One system, installed in poorly drained soil, was Inundated when rising
groundwater seeped into the bed. This occurred before the house was
completed and connected to the system. A community sewer was extended and
connectsd to this house in 1980.
Another ET bed was installed in an impervious sandstone. The bed filled up
and o>-erflowed after 4 months of use.
2
The 7500 ft non-Armon ET system in Baker County functioned properly with
no evidence of leakage.
CONCLUSIONS
Armon Systems of Oregon, Inc. ET systems did not perform satisfactorily In
Oregon. The 4 mil plastic liner was of such poor quality that all of the
systems leaked untreated effluent out of the bed and into the soil system.
This created no potential health hazards in well and moderately well
drained soils but was a distinct problem 1n poorly drained soils. Annon ET
beds were much too small to function safely on evapotranspiration. Bed
size would have to be increased about 3 times to function successfully 1n
Oregon. As a result, ET systems were dropped from the experimental program
1n 1979.
6090 10-3
(149)
-------
Chapter 11
EVAPOTRANSPIdATION ABSORPTION SYSTEMS
There are over 100,000 acres of fine-textured soils in Oregon where annual
evapctranspiration exceeds annual precipitation. These soils have per-
meability rates of less than 0.20 in./hr. Oregon On-site Sewage Disposal
Rules do not allow installation of standard soil absorption systems in
these soils because of concern for surface failures. Evapotranspiratior-
Absorption (ETA) beds were installed in these soils to determine if the
combination of soil absorption and evapotranspiration would overcome fie
limitation of slow and very slow permeability and allow an on-site
treatment and disposal system to function properly.
METHODS
Evapotranspiration-Absorption systems consisted of a septic tank followed
by an unlined seepage bed. Seepage bods were constructed 24 in. deep with
12 1n. of gravel and 12 in. of backfill. Texture of the backfill was clay
2
loam or clay. ETA bed size ranged from 1500 to 2880 ft of bottom area.
Square or rectangular seepage beds were used on nearly level terrain.
These beds were elevated, and contained within soil dikes (Figure 11-1).
This allowed placement of systems on shallow soils and prevented
infiltration of surface runoff. Long narrow beds ware used on sloping
sites (Figure 2). These were excavated into the ground. System 4 (Table
11-1) used equal distribution and the remainder of the ETA Beds used serial
distribution. Ten ETA beds were installed and effluent levels in each bed
11-1
(151)
-------
House
ETA Bed
Septic Tank
_
u.
j _
"I
-I
-1
.J
A "*•
^^ft^?^' ? o iJ C r o * n v'}^^'; >
-------
House
.
>
co
0
Septic Tank
Drop Box PI
DH
ETA Bed
FIGURE 11-2. SERIAL DISTRIBUTION EVAPOTRANSPIRATION ABSORPTION SYSTEM PLAN
-------
were monitored during the wet season. Performance of each system was
evaluated by comparing mean effluent depth in each bed to the height of the
gravel filter material in the bed.
RESULTS AND DISCUSSION
Properly constructed ETA beds functioned satisfactorily in fine-textured
soils where annual precipitation was 25 in. or less (Tables 11-1 and
11-2). Systems 1, 2 and 3 functioned at 8%, 4%, and 16% of capacity
respectively using only the first of 3 beds in each system (Table 11-1).
The lower 2 beds of Systems 1 and 2 were dry. System 4 (Table 11-1)
functioned at 4% of capacity using two 750 ft beds. Single, diked beds
functioned at 75% and 25* of capacity (Table 11-2) with no surface
failures. This was attributed to the presence of soil dikes (embankments)
around each bed which prevented infiltration of surface water.
Three serial distribution ETA beds did not function properly. The upper,
middle, and lower beds of System 8 functioned at 75%, 33%, and 42% of
capacity respectively (Table 11-3). The upper and lower beds of this
system failed in January of 1980 and February of 1981. In addition the
lower bed of this system failed in March and April of 1981 even though the
upper bed functioned during this period at 83% of capacity or less. The
middle bed of this system did not fail at any time during the monitoring
period. The upper, middle, and lower beds of System 9 functioned at 100%,
50%, and 100% of capacity respectively (Table 11-3).
11-4
(154)
-------
Table 11-1. SERIAL DISTRIBUTION EVAPOTRANSPIRATION-ABSORPTION SYSTEMS
System
1. Holmes
2. Robertson
3. Rogers
4. Kimball(2)
Sewage Flow
System Size
Performance
(gpd) (ft2) (% capacity)
Jackson County - 15 in. to 25 in. Precipitation
169 1680 (560)t1) 8
71 2880 (720) 4
Union County - 20 in. to 25 in. Precipitation
1C8 2040 (510) 16
Grant County - 15 in. Precipitation or Less
127 1500 (750) 4
(1) The first number is the total surface area (bed bottom area) of the
system. The number in parentheses is the surface area of each
individual bed.
(2) System 4 used equal distribution to one bed on each side of a
distribution box.
Table 11-2. DIKED EVAPOTRANSPIRATION-ABSORPTION SYSTEMS
System
Sewage Flow
System Size
Performance
(gpd) (ft2) (% capacity)
Jackson County - 15 in. to 25 in. Precipitation
5. Lake 205 2550 75
6. Petti grew 125 1900 25
7. Wilson 89 1700 25
11-5
(155)
-------
Table 11-3. FAILING SERIAL DISTRIBUTION EVAPOTRANSPIRATION-ABSORPTION
SYSTEMS
System Sewage Flow
8.
9.
10.
Fletcher
Shainbaugh
Smith
(gpd)
143
145
108
System Size
Performance
Bed 1
(ft2) -- %
1890
2550
1800
(630)^)
(830)
(600)
75
100
50
Bed 2
Bed 3
Capacity --
33
50
58
42
100
100
(1) The first number is the total surface area (bed bottom area) of the
system. The number in parentheses is the surface area of each
individual bed.
The upper and lower beds of this system were saturated with surface water
most of the winter and early spring months. The middle bed was at near
capacity in February, 1979; November, 1979; January, 1980; and April, 1980;
but was at less than 35% of capacity during the remainder of the monitoring
period. The upper, middle and lower beds of System 10 functioned at 50*,
58%, and 100% of capacity respectively (Table 11-3). Surface water
infiltrated into System 10 and resulted in 7 in. of water ir> the middle bed
and 16 in. of water in the lower bed during the winter and spring months.
Water seeped from the bottom bed of this system during rain storms in
December, 1979; January, 1980; February, 1980; and March, 1980. This
seepage occurred even though the middle bed contained less than 10 in. of
water and the top bed contained less than 7 in. of sewage (data not
shown). A surface diversion ditch was constructed above System 10 during
the surnner of 1980 and no seepage occurred during the winter wet season of
1980-81.
11-6
(156)
-------
System 8 (Table 11-3) failed mainly because beds were not installed level
and drop structures were either installed improperly or the shrinking and
swelling of the clay soil disrupted the drop structures so they did not
function properly. Infiltration of surface water was also a problem
because an adequate surface water diversion ditch was not constructed. In
addition, monitoring data was erratic (2 wells in the same bed showed water
level variations of 13 in.) because of improper installation of monitoring
wells. System 9 (Table 11-3) was installed in a somewhat poorly drained
soil that was not suitable for an Evapotranspiration-Absorption bed. A
permit was issued for this system prior to adop-ion of site selection
criteria January, 1978, limiting ETA construction to sites with well and
moderately-well drained soils. An inadequate surface water diversion ditch
also allowed water to infiltrate into the upper and lower beds resulting in
seepage during most of the winter and early spring months. System 10
failed because of infiltration of surface water. This problem was
corrected by construction of a surface water diversion ditch.
High water levels in ETA beds and seepage failures were associated with
the winter wet season. Water levels rose rapidly and surface failures
occurred in response to periods of heavy rainfall. Precipitation on
the surface of ETA beds and infiltration of surface water exceeded
storage capacity in some beds and surface failures resulted. However,
most ETA beds functioned properly during the wet winter months even
though precipitation exceeded potential evapotranspiration by as much as
8.7 in. (Agricultural Experiment Station Special Report 150, 1963). At no
time were water levels high enough in the gravel portions of beds in
11-7
(157)
-------
Systems 1, 2, 3 and 4 (Table 11-1) and Systems 5, 6 and 7 (Table 11-2) to
come in contact with the soil backfill. In addition, there was no evidence
of salt accumulation on the surface of any ETA Bed. These observations
suggest that very little evaporation and transpiration took place and that
ETA Beds functioned almost entirely as soil absorption beds.
CONCLUSIONS
Properly designed and constructed ETA beds functioned satisfactorily in
suitable soils in areas where annual precipitation was 25 in. or less.
Infiltration of surface water caused failure of 3 serial-distribution ETA
beds but was not a problem in diked systems. Poor construction of ETA
beds, drop structure instability, and ineffective diversion ditches were
contributing factors.
Somewhat poorly drained soils were not suitable for installation of ETA
systems.
ETA beds functioned almost entirely as soil absorption bsds with little
or no evapotranspiration.
Seepage trenches were a better alternative for fine textured soils because
they functioned bettc*-, were easier to construct, and used less than half
as much filter material (gravel). In addition, seepage trenches maximized
absorption and minimized infiltration because they had a smaller ratio
of surface area to absorptive surface.
G0237 11-8
(158)
-------
CHAPTER 12
MOUND SYSTEMS
There ara more than 1,000,000 acres of soils in Oregon on plane or convex
slopes of 12% or less (1) which are too shallow to fragipans, claypans,
hardpans, saprolite, bedrock, or groundwater to permit installation of
standard septic-tank soil absorption systems under Oregon Administrative
Rules (2). Three mounds were installed in somewhat poorly drained soils in
the north part of the Willamette Valley during 1976 and 1977 to determine
if they could adequately treat and dispose of septic tank effluent during
the winter wet season. A fourth mound was installed on a hillcrest in
Southwestern Oregon in mid 1976 to determine if septic tank effluent would
receive adequate treatment before absorption into soils shallow to
metamorphosed sandstone.
METHODS
MOUND DESIGN
Mound systems consisted of a standard septic tank, dosing tank with
submersible effluent pump and mercury float switches, and a pressure
distribution system located in a soil crowned medium sand fill. Oregon
mounds were patterned after mounds in Wisconsin (3, 4) using design
criteria in Table 1. The sand treatment medium was at least 25%
medium sand with a diameter of 0.25 to 0.5 mm and 25% or less with a
diameter finer than 0.25 mm. Because of the pronounced winter wet season
(5) in Northwestern Oregon (60% of Western Oregon's precipitation falls
between November and April), Bouma (6) and Converse (7) recommended the
12-1
(159)
-------
placement of at least 30 in. of medium sand fill below mound pressure
distributon trenches or beds.
TABLE 12-1. MOUND DESIGN CRITERIA1
Surface Area
Treatment Media
Media Depth
366 ft*
Medium Sand
25% 0.25-0.5 mm
«25* •* 0.25 mm
30 in. - where annual ppt.
24 in. - where annual ppt.
35 in./yr.
35 in./yr.
Maximum Design Loading Rate2 1.23 gal/ft^/d
No. Times Effluont
Filtered Through Treatment
Sand
Dosing Frequency
Dosing Rate
Dose Volume
Dose Controls
Media Surface Protected
With Soil Cover
2-5 times/day
0.25 - 0.6 gal/ft2/dose
90 - 225 gal/dose
Volumetric; mercury float switches
Yes
* Features shown apply to a mound designed to process up to 450 gal
septic tank effluent per day.
^ Based on pressure distribution bed or trench bottom area only.
Greater fill depth was recommended to provide some assurance that the
distance separating mound pressure distribution systems and high ground-
water tables would be sufficient to allow most of the treatment sand to
remain unsaturated during periods of high precipitation.
Mounds operated on the same principal as Oregon intermittent sand filters
12-2
(160)
-------
(Chapter 3). However, mounds discharged treated wastewater to the natural
topsoil below fill sands for final effluent purification and disposal while
sand filters discharged treated effluent to disposal trenches placed into
subsoils or permeable geological materials.
Intermittent doses of septic tank effluent were pumped from a dosing tank
to a network of perforated plastic distribution pipes bedded in 12 in. of
washed 3/4 in. to 2-1/2 in. gravel. Construction details for pressure
distribution systems appear in Table 12-2 and Table 12-3. Information on
hydraulic loading appears in Table 12-3. After dosed effluent passed
through fill sand, it entered the natural topsoil, downgradient from the
mound's pressure distribution system, for final treatment and disposal.
Pressure distribution systems were used in mounds to spread effluent evenly
throughout the entire absorption bed or trench system, prevent saturated
flow through filter media, and retard the development of biological
clogging at the gravel-sand interface (8). Distribution systems were
designed to operate with approximately 5 ft of head at the remotest orifice
of each distribution lateral to keep orifices from clogging with organic
matter. Pressure distribution system dose volumes were set so the majority
of septic tank effluent applied at each pump cycle would be absorbed
through the gravel-sand interface at the base of bed or trench gravel.
Fill sands were placed over native topsoil at the base of mounds after
vegetation and debris had been removed and the soil had been plowed,
perpendicular to the slope, to a depth of at least 6 in.
12-3
(161)
-------
TABLE 12-2. MOUND PRESSURIZED DISTRIBUTION SYSTEM CONSTRUCTION DETAILS
TYPE SYSTEM BOTTOM LATERAL ORIFICE ORIFICE
SYSTEM SYSTEM DIMENSIONS AREA (FT?) DIA. (1n) DIA. (in) SPACING (1n. c-c)
1 (Nowodworski) Trenches 4-2'xSO'xl' 400 1.25 0.25
2 (Obrlst) Trenches 4-2'x50'xl' 400 1.5 0.25
3 (Royland) Trenches 3-2'x42'xr 252 1.5 0.25
4 (Suiter) Beds 20'x20'xl1 400 1.0 0.25
24
30
24
30
X6943.A
2/23/82
-------
TABLE 12-3. ACTUAL KXJND HYDRAULIC LOADING
SYSTEM
1 (NoMOdworskl)
2 (Obrist)l
: (Roy! and)
4 (Suiter)
1 Dally flow
XG943.A
2/23/82
SAND
INFILTRATIVE
SURFACE AREA
(ft*)
400
400
252
400
estimated.
DESIGN
FLOW
(gpd)
450
450
300
450
ACTUAL
aow
(gpd)
47
130-225
103
319
LOADING
RATE
(g/ft2/d)
0.1
0.28 - 0.50
0.34
0.71
DOSE
VOLUME
(g/dose)
110
225
210
215
DOSING
RATE
(g/ft2/dose)
0.28
0.56
0.83
0.54
DOSING
FREQUENCY
(doses/day)
0.43
0.58 - 1.0
0.49
1.48
-------
Mound D^sal areas were sized so all treated effluent and incident
precipitation would be absorbed by the topsoil before it reached the fill
edge. Details identifying mound basal area characteristics are shown
in Table 12-4.
Mounds were crowned with locally available topsoil to provide a barrier
against freezing and exposure to the public and animals, increase runoff,
and provide a medium for growing a protective vegetative cover.
Three mounds (Figure 12-1) were constructed on moderately permeable,
somewhat poorly drained soils. The annual precipitation at these sites
ranged from 37.61 to greater than 50 in. (5, 9). These mounds used
trenches placed above 30 in. of sand fill to keep wastewater dispersed
over a broad area and keep pressure distribution systems elevated far
enough over groundwater to provide an adequate zone for septic tank
effluent treatment during storm cycles.
One mound (Figure 12-2) was constructed on a well drained ridgetop over
moderately permeable soils shallow to metamorphosed sandstone. The annual
precipitation at the site averaged less than 31 in. (5). Soils at this
location were well drained so there was little concern groundwater would
rise into fill material during storm cycles. Consequently, a bed was
placed above 24 in. of fill sand.
12-6
(164)
-------
TABLE 12-4. MOUND SOIL ABSORPTION SYSTEM DETAILS
TOPSOIL
SYSTEM
1 (Nowodworski)
2 (Obrist)
3 (Royland)
4 (Suiter)
MOUND BASAL
AREA (ft?)
6,150
6,000
?,360
4,850
INFILTRATION PERMEABILITY
RATE (in/hr) (in/hr)
0.3
0.3
0.3
0.3
0.6
0.6
0.6
0.6
- 2.0
- 2.0
- 2.0
- 2.0
TEXTURE
silt loam
silt loam
silty clay loam
silt loam
XG943.A
2/23/82
-------
House
E
Stptic Tanfc
Dosing Tank
d
d
Pressure Piping
FIGURE 12-1. SAND FILL MOUND WITH PRESSURE DISTRIBUTION TRENCHES
-------
House
Septic Tank
Pressure Distribution Piping
Dosing Tank
i I
1
i !
FIGURE 12-2. MOUND WITH PRESSURIZED DISTRIBUTION BED
-------
MONITORING
Water samples were collected from monitoring ports 20 ft upgradient,
below the center of the mound, and 20 ft downgradient and analyzed for
total coliform, fecal coliform (10) and nitrate-nitrogen (11).
RESULTS AND DISCUSSION
MOUND TREATMENT
Although data (Table 12-5) indicated there was little evidence of serious
bacterial or chemical contamination in groundwater, it was difficult to
assess the actual degree of treatment which took place in mounds since
groundwater dilution significantly lowered nitrate and coliform
concentrations.
During the 10 times (November 1978 through February 1980), System 1 was
monitored, fill sands remained unsaturated. Groundwater was never detected
immediately above the fragipan even though soil mottling indicated seasonal
groundwater was present in the past. The reason for the absence of
groundwater was not determined. Perhaps, scarification of the mound's
basal area during system construction altered the normal soil drainage
pattern in that vicinity. The mound's small hydraulic loading rate (47
gal/d, 10% of the mound's design capacity) was probably partially
responsible for the lack of a discernible groundwater table at that point.
Water samples collected near Syscem 2 indicated the system had little
measurable impact on groundwater. In spite of the fact groundwater levels
remained an average of 11 in. below pressure distribution trenches during
12-10
(168)
-------
TABLE 12-5. MOUND WATER QUALITY MONITORING DATA
MONITORING UELL LOCATIONS
20' UPGRADIENT OF BELOW CENTER OF
PRESSURE DIST. SYSTEM PRESSURE DIST. SYSTEM
SYSTEM N032 FC3
1 (Nowodworski) none none
2 (Obrist) 0.25 13
(2)* (19)
3 (Roy land) none none
4 (Suiter) none none
1 None = no monitoring well installed
Dry = monitoring wen always dry at
2 Nitrate nitrogen expressed as mg/1;
3 Fecal and total ooliform expressed
4 Number of samples
XG943.B (1)
2/23/82
TC N03 FC TC
none dry dry dry
580 1.29 105 2,565
(5) (2) (21) (6)
none none none none
none none none none
time of observations.
arithmetic mean.
as mg/1; geometric mean.
20' DOWNGRADIENT OF
PRESSURE DIST. SYSTEM
N03 FC TC
none none none
0.47 29 1,098
(1) (18) (5)
1.83 210 3,195
(4) (5) (3)
5,000 9.000
(1) (l)
-------
high rainfall months (data not shown), a high degree of bacteriological and
chemical treatment took place as septic tank effluent moved through fill
sand.
Data indicated treated effluent underwent further dilution by grcundwater
as it moved away frcn the mound's pressure distribution system. Fecal
coliform (105 org/100 ml) detected in groundwater in samples collected
below the center of the mound's pressure distribution system were nearly 4
times higher than fecal concentrations (29 org/100 ml) found 20 ft
downgradient from pressure distribution trenches. Total coliform and
nitrate nitrogen numbers showed similar declines with distance as effluent
moved from the pressure distribution system.
Bacterial and nitrate nitrogen concentrations detected in groundwater 20 ft
downgradient from System 3 indicated that system had little adverse impact
on the environment.
Groundwdter was observed on one occasion at System 4. Bacterial analysis
indicate some saturated flow may have occurred between the pressure
distribution bed and groundwater. Several rodent burrows in the immediate
vicinity of the downgradient monitoring well suggested bacterial numbers
were probably due to short circuiting of partialy treated effluent into the
monitoring well.
12-12
(170)
-------
MOUND OPERATION AND MAINTENANCE
Table 12-6 shows site conditions at mound locations and general performance
of mound soil absorption systems observed during the 20-55 month period
systems were studied. Although effluent surfacing was not apparent
downgradient from any mound, during periods of heavy rainfall, surface
water often appeared within a few feet of System 2 and System 3 toeslopes.
However, saturated soil extended evenly across a broad area downgradient
from these mounds so wetness appeared to be due to a combination of heavy
rainfall and change in relief rather than the influence of mound effluent.
The pressure distribution bed at System 4 (the mound receiving the greatest
average daily flow 319 gpd), was unearthed to determine the condition of
fill sand (effective size 0.25; uniformity coefficient 3.4) at the bed's
gravel-sand interface after 45 months of operation. No biological mat had
developed at the base of the bed. This observation suggested mound
pressure distribution systems may operate indefinitely without clogging
provided they are not hydraulically overloaded or subjected to effluents
with unusually high waste strengths.
During the 55 month period System 2 was observed, 2 submersible effluent
pumps failed. The first failure occurred after 37 months of operation.
The second submersible pump failed after 18 month's use when a mercury
float on-off switch connected to the pumps by a fixed rod detached. Free
floating switches required in the system's original permit were replaced
with the fixed arm float when the system's second pump was installed. Pump
failures were not observed at other mound installations.
12-13
(171)
-------
TABLE 12-6. A DESCRIPTION OF SITE (DDITIONS AND MUN) PERFORMANCE
SYSTEM
FEATIKE DESCRIBED
Soil Absorption Systan
Site Limitation
Soil Texture
Below Mound Base
Slqpe («)
Average Mound
Loading Rate (gpd)
Annual
Precipitation
Efflierr Absorption
By Topsoi^
Mound Installation
Date
Observation ?«riod
Muter of Observations
1 (NOWODWDRSKI)
Seasonal groundwater;
mottling at 15-22 in.;
cfense fragipan at
17-25 in.
silt loam
7
47
39.91
Satisfactory
October 1977
Nov. 1978-July 1980
14
2 (OBRIST)
Seasonal groundwater;
mottling at 8-12 in.;
dense fragipan at
12-14 in.
silt loam
4
130-2251
39.91
Satisfactory
Decsrfcer 1976
Dec. 1976-July 1931
21
3 (ROYLAND)
Seasonal groundwater;
mottling at 4-6 in.;
cfense c lay pan at
10-17 in.
silty clay loam
12
108
59.35
Satisfactory
August 1976
August 1976-Nov. 1980
12
4 (SUITER)
12-18 in. to fractured
weathered basalt
silt loam
2-12
319
30.96
Satisfactory
July 1976
March 1978-Oec. 1981
8
1 Flew estimated.
XB943.C
-------
CONCLUSION
Mounds functioned satisfuctorily on nearly level to sloping Western Oregon
sites where medium textured or coarser soils were shallow to groundwater or
fractured rock and the annual precipitation was less than 50 in. However,
landform, sand cost, and availability of natural topsoil substantially
limited the practical application of mounds at many Oregon locations where
sand filter systems were suitable for site development.
Consequently, no mounds were permitted in the experimental program after
1977. Further mound testing was abandoned for the following reasons:
1. Few Oregon sites, which were not acceptable for standard septic tank
soil absorption system development, had topographic features (i.e.,
simple slopes of less than 12%) or topsoil characteristics (medium or
coarser textured soils) with high enough infiltration rates to absorb
septic tank effluent plus all precipitation which fell annually
between November and April;
2. Many soils, based on the recommendation of Bouma and Wisconsin mound
designers, were too shallow, (less than 24 in.) to seasonal
groundwater, fractured or weathered rock, or hardpans to be suitable
to absorb both septic tank effluent and seasonal precipitation;
3. The actual level of treatment provided by mound filtration was
difficult to evaluate because of the influence of groundwater
dilution; •
12-15
(173)
-------
2
4. Large quantities of sand (up to 600 yds ) were required in mound
construction and nearby s*nd sources with desirable media
characteristics were not always readily available, adding
substantially to construction costs; and
5. Extensive field testing of mounds was already underway in
Wisconsin.
12-16
(174)
-------
REFERENCES
1 State Water Resources Board, 1^69. Oregon's Long-Ranqe
Requirements for Water. General Soil Map Report with Irrigable
Areas. Willamette Drainage Basin, Appendix 1-2 through 1-18.
2 Department of Environmental Quality, 1975. Chapter 340, Division
71, Standards for Subsurface and Alternate Sewage and Nonwater-
Carried Waste Disposal, Revised March 13, 1981. State of Oregon.
3 Bouma, J., J. C. Converse, R. J. Otis, W. G. Walker and W. A. Ziebell.
1975. A mound system for on-site disposal of septic tank effluent in
slowly permeable soils with seasonally perched water tables. J. Env.
Qual., pp 382-1388.
4 Bouma, J., J. C. Converse, W. A. Ziebell and F. R. Magdoff. 1974. An
experimental mound system for disposal of septic tank effluent in
shallow soils over creviced bedrock. Proceedings Intl. Conf. on Land
for Waste Management. Ottawa, Canada.
5 U. S. Department of Commerce. 1960. U. S. Department of Commerce
Weather Bureau. Climatology of the United States No. 60-35, Climate of
Oregon, Washington, D. C.
6 Bouma, J. A., personal confivjnicatiqn. 1975. Assoc. Prof, of Soil
Science, University of Wisconsin, Madison.
' Converse, J. C., personal communication. 1977. Associate Professor of
Agricultural Engineering, University of Wisconsin, Madison.
^ J. C. Converse, J. L. Anderson, W. A. Ziebell, and J. Bouma, "Pressure
Distribution to Improve Soil Absorption Systems," Home Sewage Disposal,
Proc. Am. Soc. Ag. Eng., Dec. 1974. pp 104-115.
" U. S. Department of Commerce. 1973. Monthly Normals of Temperatures,
Precipitation, and Heating and Cooling Degree Days 1940-70. U. S.
Department of Commerce, National Oceanic and Atmospheric Administration,
Climatology of the United States No. 81 (By State). National Climatic
Center, Asheville, N.C.
10 American Public Health Association. 1975. Standard methods for the
examination of wastes and wastewater. Prepared and published jointly
by: American. Water Works Association, Water Pollution Contrc1
Federation, and American Public Health Associations, 1740 Broadway, New
York, N. Y.
11 U. S. Environmental Protection Agency. 1979. Methods of chemical
analysis of water and wastes, EPA - 600/4-79-020, Environmental
Monitoring and Support Laboratory, Cincinnati, Ohio.
XG943 * 12-17
(175)
-------
CHAPTER 13
GRAY WATER
Nearly 35* of the total wastewater generated in a house is derived !rom the
toilet (1). Composting toilets (Chapter 14) were used in Oregon to
eliminate water transport of toilet wastes to conserve water and reduce the
potential for groundwater pollution.
Gray water was pretreated by a number of devices to determine their
capacity to remove suspended and settleable solids and to protect soil
absorption trenches against premature clogging caused by these substances
(2,3). Since gray water contains a variety of objectionable chemical and
bacteriological characteristics, gray water effluents were discharged to
disposal trenches for final treatment and disposal (4,5,6). Due to the
reduced hydraulic load which resulted from compost toilet use; gray water
disposal fields were 50% smaller than they would have been had water flush
toilets been used.
A 198-gal septic tank, 55-gal pea-gravel filter, 132-gal trickle rock
("roughing") filter, and a small recirculatlng sand filter preceded by a
750-gal septic tank were installed and monitored to determine which would
produce the highest quality effluent. BOD , SS, nitrogen and coliform
densities in effluents from these "treatment devices were compared with
effluent produced by the treatment of gray water in a standard 1,000-gal
septic tank.
13-1
Preceding page blank
-------
RESULTS AND DISCUSSION
RECIRCULATING SAND FILTER
2
A 64-ft recirculating sand filter (Figure 13-1) preceded by a 750-gal
septic tank was used to treat gray water from a shower, lavatory, and
kitchen sink. Effluent drained from the septic tank into a recirculation
tank, which contained a s^all submersible effluent pump, and mixed with
previously filtered effluent. Mixed wastewater was applied to the open
sand filter surface 5 times daily through 5 spray heads. Spray cycles
lasted 2 minutes. Recirculation events were regulated by a percentage
timer. Treated effluent discharged into two 125-ft long disposal trenches.
The recirculating sand filter (Table 13-1) produced a ligher quality
effluent than other graywater pretreatment systems. BOCL , SS, and fecal
colitorm averaged 2.22 mg/1, 10.5 mg/1, and 15 org/100 ml respectively.
Total nitrogen was 5.02 mg/1. Most nitrogen was in the nitrate form. The
sand filter reduced total phosphate from 2.14 mg/1 to 0.19 mg/1. Phosphate
removal was attributed to phosphate fixation 1n filter sand (7,8).
Dosing the recirculating sand filter for 10 'ninutes each day resulted in
aerobic treatment and better quality effluent than was produced in similar
studies in Wisconsin (9,10,11). The residents had no children, worked away
from home during the day, followed a diet that included a small amount of
meat, and used an organic low phosphate soap. In addition, average daily
hydraulic loading rates (27 gpd) were very low and much of the effluent
evaporated as it was recirculated through the sprinkler head to the sand
filter surface during warn1, dry, summer months.
13-2
(178)
-------
Sand Filter
Disposal Field
Inderdraiir
FIGURE 13-1. GRAY WATER RECIRCUIATING SAND FILTER SYSTEM
13-3
(179)
-------
TABLE 13-1. A COMPARISON OF CEPTIC TANK AND RECIRCULATING SAND FILTER EFFLUENTS;
VAN DER WERF GRAY WATER SYSTEM1
EFFLUENT CHARACTERISTIC2
DATE
10-17-79
10-25-79
11-15-79
12-13-79
1-3-80
5-8-80
5-22-80
6-4-80
8-21-80
10-30-80
Mean
Septic
Tank
Effluent
BOD
2
-
1
1
1
1
3
3
7
1
2.22
(9)3
103
(13)
5 GS
6
1
5
7
30
8
5
1
17
25
10.5
(10)
207
(13)
TP04
0.239
0.247
0.180
0.169
-
0.077
0.244
0.169
-
-
0.19
(7)
2.14
(9)
N02
0.02
0.02
0.02
0.02
0.02
0.02
0.02
0.02
-
0.02
0.02
(9)
0.02
(13)
N03
4.41
3.76
5.02
5.56
4.71
-
2.21
7.25
-
-
4.70
(7)
0.15
(13)
NH3
0.06
0.18
0.20
0.09
0.08
0.04
0.06
0.07
0.05
0.08
0.09
(10)
5.74
(13)
7KN
0.3
0.5
-
0.4
0.4
0.2
0.2
0.3
0.9
0.5
0.41
(9)
18.18
(13)
TN
4.73
4.28
-
5.98
5.13
-
2.43
7.57
-
-
5.02
(6)
18.35
(13)
rc
100
10
10
2
10
10
10
20
10
120
15
(10)
8,150
(10)
TC
-
-
-
-
-
100
100
200
-
20,000
737
(3)
1.6 x 106
(3)
1 Flow averaged 27 gpd.
2 6005, SS, and Ffy and nitrogen expresseo as mg/1; arithmetic mean. CoHform
densities expressed as org/100 ml; geometric mean.
3 Number of samples.
13-4
(180)
-------
PEA-GRAVEL FILTER
The 56-gal pea-gravel filter (Figure 13-2) was preceded by a nylon filter
stocking to remove gross solids. After gray water drained through the
filter stocking, it trickled onto a splash plate at the filter surface and
passed through a layer of medium sand and a gravel covered underdrain into
a sample collection box. Overflow discharged to a sanitary sewer.
Gray water was generated from a lavatory, wash basin, bathroom tub/shower,
and kitchen sink. Dishes were washed manually using biodegradable
detergent. System users consumed very little meat and were careful to keep
greases, fats, and oils out of the treatment and disposal system.
The pea-gravel filter was not preceded by a septic tank. As a result,
effluent quality data (Table 13-2) were quite variable. BOD5 rangtJ from 5
mg/1 to 243 mg/1 and SS ranged from 20 mg/1 to 1086 mg/1. Similar
variations were observed in M3, N03 , TN, TKN, and fecal coliform
densities. The broad range ir effluent quality was attributed to the
varied nature of the waste gtnerating events and lack of effluent
stabilization due to the absence of a septic tank or surge tank.
TRICKLE ROCK FILTER
A gravel filled, gravity-fed, 132-gal "roughing filter", similar in design
to the trickle filter, hjd little effect on gray water treatment. BOD
D
and SS (Data not shown) wire considerably higher than levels that occurred
in the 1,000-gal septic .ank effluent (Table 13-4). Observations indicate
the roughing filter did not provide adequate treatment.
13-5
(181)
-------
Inlet
Splash Plate
•Outlet
FIGURE 13-2. PEA-GRAVEL FILTER
13-6
(182)
-------
TABLE 13-2. BErCER 55-GALLON PEA-GRAVEL FILTER EJ-FLUENT QUALITY
EFFLUENT CHARACTERISTIC2
DATE
7-19-79
11-7-79
1-2-80
1-16-80
3-20-80
4-8-80
5-14-80
5-22-80
10-29-80
12-3-80
Mean
B005
51
5
28
44
44
10
141
63
19
243
65
(10)3
SS
1086
20
99
292
173
33
705
190
46
65
271
(10)
N02
0.03
0.03
0.08
0.26
0.04
-
0.02
-
0.02
0.02
0.06
(8)
N03
0.74
3.53
1.09
11.64
9.94
1.74
4.90
1.59
52.80
0.60
8.85
(10)
W3
0.4
0.25
3.2
1.1
0.5
0.31
1.0
0.7
0.31
0.41
0.82
(10)
TKN
34.0
3.7
24.0
51.0
17.0
1.3
34.0
21.0
30.0
27.3
24.3
(10)
TN
34.8
7.3
25.2
62.9
27.0
3.0
38.9
22.6
82.8
27.9
33.2
(10)
FC
3.0 x 105
400
1.0 x 106
1.0 x 106
1.3 x 104
100
2000
4500
10
1.4 x 104
6.75 x 103
(10)
TC
-
-
-
-
-
3.2 x 105
4.0 x 105
2.8 x 1C6
100
3.3 x 105
1.1 x 105
(5)
Flow averaged 49 gpd. System used by 2 adults and 1 child.
2 8005, SS, and nitrogen expressed as mg/1; arithmetic mean. Col1fonus
expressed as org/100 ml; geometric mean.
3 Number of samples.
CIPAX 198-SALLON SEPTIC TANK
This system consisted of a 198-gal septic tank (Figure 13-3) followed by 3
disposal trenches 50 ft long. Hastewater was generated from a kitchen
sink, 2 lavatories, a bathtub, a shower, and an automatic clothes washer.
13-7
(183)
-------
Inlet
Outlet
FIGURE 13-3. CIPAX 198-GALLON SEPTIC TANK
13-8
(184)
-------
Septic tank effluent quality (Table 13-3) indicated that the 198-gal septic
tank provided reasonable surge stability. Wastewater residence time was
about 45 hours based on an average daily flow of 106 gal (Table 13-3;
Footnote 1). BODj and SS were high (268 mg/1 and 167 mg/1) but not as
variable as they were in the trickle sand filter (Table 13-3) and gravity
fed gravel filter which lacked surge protection.
TABLE 13-3. FRANS GRAY WATER 198-GALLON SEPTIC TANK EFFLUENT QUALITY l
EFFLUENT CHARACTERISTIC2
DATE
11-7-79
1-9-80
2-6-80
4-30-80
5-28-80
6-12-80
8-20-80
11-28-80
1-14-81
2-12-81
Mean
BOD5
230
306
219
198
263
327
348
185
348
260
268,
do)3
SS
192
100
416
120
64
102
228
50
228
-
167
(10)
N02
-
0.03
0.02
0.02
0.02
0.02
0.02
0.02
0.02
-
0.02
(8)
N03
0.81
0.67
0.59
0.02
2.14
0.18
0.23
0.10
0.21
0.10
0.5
(10)
NH3
0.75
2.55
1.64
2.26
4.9
2.27
0.84
2.29
0.45
2.33
2.0
(10)
TKN
7.0
12.0
10.4
11.5
16.8
11.6
12.8
9.2
0.7
9.25
10.3
(10)
TN
7.87
12.7
11.01
11.54
18.96
11.8
13.5
9.32
2.93
9.35
10.9
(10)
FC
4.8 x 105
1.0 x 105
1.0 x 106
1.0 x 105
1.3 x 104
-
1.0 x 106
-
1.0 x 106
-
3.1 x 105
(7)
TC
1.0 x 105
1.0 x 106
1.0 x 107
8.0 x 106
-
-
1.0 x 107
-
1.0 x 107
-
3.0 x 106
(6)
1 Flow averaged 106 gpd. System used by 2 adults and a child.
2 BOD5, SS, and nitrogen expressed as mg/1; arithmetic mean. Conforms
expressed as org/100 ml; geometric mean.
3 Number of samples.
13-9
(185)
-------
STANDARD 1000-GALLON SEPTIC TANK
This system was used by one adult who produced an average of 17.5 gal
of wastewater per day. Wastewater from a kitchen sink, automatic
dishwasher (seldom used), automatic clothes washer, two lavatories, and a
bathtub/shower combination drained into a 1000-gal septic tank.
TABLE 13-4. MEADOR 1000-GALLON SEPTIC TANK EFFLUENT CHARACTERISTICS1
EFFLUENT CHARACTERISTIC2
DATE
1-9-80
2-6-80
4-23-80
5-28-80
6-11-80
7-25-80
8-20-80
11-28-30
1-14-81
2-11-81
3-11-81
Mean
BOD5
135
160
438
254
324
336
171
390
170
135
62
234,
(ID3
SS
1
64
33
14
33
104
20
52
20
23
13
34
(ID
N02
0.02
0.02
0.02
0.02
0.02
0.02
0.02
0.02
0.02
-
0.02
0.02
(10)
N03
0.2
0.14
0.57
1.64
0.04
0.01
0.02
0.08
0.02
0.10
0.02
0.26
(11)
NH3
1.12
0.21
0.23
0.18
1.0
5.41
0.94
7.05
2.63
2.08
2.22
2.1
(ID
TKN
4.1
3.0
5.6
5.6
4.6
11.6
9.8
10.5
6.8
6.0
8.0
7
(11)
TN
4.32
4.06
6.19
6.26
4,66
11.63
9.82
10.6
6.82
6.1
8.?
7.26
(ID
1.0
1.0
3.5
2.2
3.0
2.1
1.0
7.5
3.0
1.0
FC
x 105
x 106
x 104
x 105
x 104
-
x 105
-
x 105
x 1.0s
x 102
x 105
(9)
TC
1
3.1
9
2.8
2
3.9
2.2
1.0
6.5
1.1
x 106
x 106
x 105
x 105
x 105
x 1C5
x 105
-
x 107
x 10*
x 106
6.3 x 105
(10)
1 Flow averaged 17.5 gpd. System used by 1 adult.
2 6005, SS, and nitrogen expressed as mg/1; arittrnetic mean. Coliforms
expressed as org/100 ml; geometric mean.
Number of samples.
13-10
(186)
-------
Effluent from the septic tank was discharged into five 45-ft long disposal
trenches.
Results of the study (Table 13-4) are similar to those reported in
Wisconsin (11) and Canada (12) except BOD5 values were somewhat higher
and TKN values were about half. When compared to septic tank effluent
generated from total residential wastewater flow (4), gray water con-
tained lower concentrations of nitrogen and somewhat higher concentrations
of BODg . In addition, total and fecal coliform densities were one log
1ower.
CONCLUSIONS
Gray water treatment systems did not eliminate the necessity for subsurface
disposal fields. Data showed that gray water had comparable or higher
levels of fecal coliform, 6005, and SS than combined waste streams.
Although these components were attenuated through pretreatment devices, the
only justification for different permit standards for split waste systems
should be based on reduced hydraulic loading.
The most economical and practical method for grty water disposal was a
standard septic tank with a reduced size disposal fir;d.
13-11
(187)
-------
REFERENCES
1 Siegrist, R. L., 1978. Waste Segregation to Facilitate On-site
Wastewater Disposal Alternatives. In: Proceedings of the Second
National Home Sewage Treatment Symposium. American Society of
Agricultural Engineers, St. Joseph, Michigan, pp. 271-231.
2 Bendixen, T. W., M. Berk, J. P. Sheeny and S. R. Weibel. 1950.
Studies on Household Sewage Disposal Systems. Part II. Federal
Security Agency, Public Health Service, Environmental Health
Center, Cincinnati, Ohio.
3 Laak, R. 1970. Influence of Domestic Wastewater Pretreatment on
Soil Clogging. J. Water Pollution Control Federation, 42:1495-
1500.
4 Small Scale Waste Management Project. 1978. Management of Small
Waste Flows. University of Wisconsin, EPA-600/2-78-173, Municipal
Environmental Research Laboratory, Office of Research and
Development, Cincinnati, Ohio.
5 Witt, M., R. Siegrist, and W. C. Boyle. 1975. Rural House-
hold Wastewater Characterization. In: Proceedings of the National
Home Sewage Disposal Symposium. American Society of Agricultural
Engineers, St. Joseph, Michigan, pp. 79-88.
6 Bennett, E. R., K. D. Lindstedt, and J. T. Felton. 1975. Rural
Home Wastewater Characteristics. In: Proceedings of the National
Home Sewage Disposal Symposium. American Society of Agricultural
Engineers, St. Joseph, Michigan, pp. 74-78.
7 Beek, J. and F. A. M. deHaan. 1973. Phosphate Removal by Soil 1n
Relation to Waste Disposal, Proc. of Internet. Conf. on Land for
Waste Management, Ottawa, Canada.
^ Sikora, L. J. and R. B. Corey. 1976. Fate of Nitrogen and Phosphorus
in Soils Under Septic Tank Waste Disposal Fields, Transactions,
ASAE, 19, 866.
9 Siegrist, R. L., W. C. Boyle, ar.d D. L. Anderson. 1981. A field
Evaluation of Selected Water Conservation and Wastewater Reduction
Systems for Residential Applications. Technical Report WIS WRC 81-
02. Water Resources Center, University of Wisconsin, Madison,
Wisconsin, pp 74-99.
10 Otis, R. J., W. C. Boyle, and D. K. Sauer. 1975. The performance of
Household Wastewater Treatment Units Under Field Conditions. In:
Proceedings of the National Home Sewage Disposal Symposium.
American Society of Agriculturel Engineers, St. Joseph, Michigan,
pp. 191-201
13-12
(188)
-------
11 Siegrist, R. L., and W. C. Boyle. 1982. Onsite Reclamation of
Residential Greywater. In: Proceedings of the Third National
Symposium on Individual and Small Community Sewage Treatment, ASAF
Publication 1-R2. American Society of Agricultural Engineers, St.
Joseph, Michigan, pp 176-136.
12 Brandes, M. 1978. Characteristics of Effluents From Septic Tanks
Treating Gray and Black Waters from the Same House. J. Wat.
Poll. Cont. Fed. 50: 2547-2659.
XG1071 13-13
(189)
-------
CHAPTER 14
COMPOSTING TOILETS
One of the main sources of pollution associated with modern houses is the
large amount of water used to transport toilet waste to the septic tank.
If water transport can be eliminated, it would not only reduce the
potential problem of pollution, but would also result in water
conservation. In addition, use of smaller disposal fields may be practical
as well as use of marginal soils for disposal of gray water. These
considerations have generated considerable interest in the idea of
separating toilet waste from the remainder of the household waste stream.
Forty-one permits were issued for installation of composting toilets.
Twenty-eight toilets were installed. Many toilet users had difficulty
learning how to use and maintain their units properly. Some users were
pleased with their composting toilet but many were not. Many complained of
solid and liquid waste buildup, odors, and flies. Six users removed their
units and replaced them with conventional toilets because of these
problems. Compost toilet performance and user acceptance is discussed in
detail in progress reports February 28, 1978 (Appendix E), January 30, 1979
(Appendix F) and December 30, 1979 (Appendix G).
Composting toilets were dropped from the experimental program October, 1977
when the Oregon Department of Commerce assumed legal jurisdiction.
G0658 14-1
(191) Preceding page blank
-------
CHAPTER 15
CHARACTERISTICS OF RESIDENTIAL AND INDUSTRIAL SEPTIC TANK EFFLUENTS
The seotic tank is a very simple device for treatment of household waste
prior to discharge into a soil absorption system. Its main function is to
remove settleable solids and floating scum and change the character of
non-settleable solids by anaerobic digestion. The effluent discharged is
relatively free of settleable solids but contains non-settleable solids and
soluble organic matter.
The septic tank and disposal field are used extensively iii Oregon for
treatment and disposal of household waste, but little has been done to
characterize septic tank effluent. This study was undertaken to determine
the quality of household and industrial effluents in order to design and
evaluate on-site treatment and disposal alternatives.
METHODS
Effluent was characterized from 8 residential systems and 2 industrial
systems. Double compartment tanks were used in residential Systems 1, 2,
and 7 (Table 15-1). Single compartment tanks were used for the rest of the
residential systems and the 2 industrial systems (Table 15-2). Industrial
System 1 used a 2,000 gal tank for the sawmill and a 1,500 gal tank for the
office building. Sewer lines from these 2 facilities flowed into a pump
tank where effluent samples were collected.
15-1
C193) Preceding page blank
-------
TABLE 15-1. DETAILS OF RESIDENTIAL SEPTIC TANKS.
System Tank Vol. (gal) Compartments1 Const. Material Fittings
1
2
3
4
5
6
7
8
(McCurley)
(Gilkey)
(Grooms)
(Boettcher)
(Reber)
(McClaflin)
(Roberts)
(Anderson)
1?50
1250
1000
1000
1000
1000
1250
1000
2
2
1
1
1
1
2
1
Concrete
Concrete
Concrete
Concrete
Concrete
Concrete
Concrete
Concrete
Cast Iron
Cast Iron
Cast Iron
Cast Iron
Cast Iron
Cast Iron
Cast Iron
Cast Iron
* Two compartment tanks had a liquid capacity of 825 gal in the first
chamber and 425 gal in the second chamber.
TABLE 15-2. DETAILS OF INDUSTRIAL SEPTIC TANKS.
Tank Compart- Const.
System Facility Vol. (gal) ments Material Fittings
1. (International Sawnill
Paper Co.) Office Bldg. 2000, 15001 1 Concrete Cast Iron
2. (Weyerhaeuser Watchman's
Ore-Aqua Inc.) Trailer, 1000 1 Fiberglass SCH 40 ABS
Operations Bldg.
1 The 2000 gal septic tank served the sawmill and the 1500 gal
septic tank served the office building.
Average daily flow was recorded for each system except residential System 8
and effluent samples were collected and analyzed for BOD5 , SS, N03, NH3,
total kjeldahl nitrogen (TKN), total nitrogen (TN), fecal coliform (FC),
and total coliform (TC). (1, 2).
15-2
(194)
-------
RESULTS AND DISCUSSION
RESIDENTIAL SEPTIC TANK EFFLUENT QUALITY
Average flow from residential systems was 164 gpd (Table 15-3).
TABLE 15-3. CHARACTERISTICS OF 8 SINGLE FAMILY RESIDENTIAL SEPTIC TANK
EFFLUENTS
SEPTIC TANK EFFLUENT CHARACTERISTICS *
Ave.
Flow
System (gpd) BOD5 SS N02 N03 NH3 TKN TN FC TC
1 (McCurley)
2 (Gilkey)
3 (Grooms)
4 (Boettcher)
5 (Reber)
6 (McClaflin)
7 (Roberts)
8 (Anderson)
Weighted
Arithmetic
Average
191
113
139
194
176
161
174
«•
164
(7)
149,
(8)2
197
(11)
188
(7)
222
(11)
378
(7)
125
(16)
348
(7)
322
(3)
217
(70)
240
(8)
38
(11)
79
(7)
193
(11)
276
(7)
91.7
(16)
171
(7)
203
(3)
146
(70)
0.02
(9)
0.02
(10)
0.02
(6)
_
0.03
(7)
C.02
(15)
0.02
(7)
0.02
(3)
0.02
(57)
0.18
(9)
0.81
(10)
0.04
(7)
„
0.16
(6)
0.56
(16)
0.38
(8)
0.24
(3)
0.4
(59)
37.8
(9)
35
(10)
35.5
(7)
_
53.3
(7)
36.1
(16)
55.9
(8)
32.56
(3)
40.6
(60)
56.9
(9)
58.4
(10)
45.6
(7)
_
71.8
(6)
51.3
(16)
70.5
(7)
47.2
(2)
57.1
(57)
57.1
(9)
59.20
(10)
45.67
(6).
_
71.9
(5)
51.80
(15)
70.9
(7)
47.45
(2)
57.5
(54)
2.0 x 104
(10)
1.1 x 105
(10)
7.0 x 104
(6)
_
5.4 x 105
(6)
8.0 x 104
(14)
1.0 x 106
(8)
8.1 x 104
(2)
2.6 x 105
(56)
1
1
7
2
9
2
1
1
.5 x 105
(8)
.8 x 106
(9)
.7 x 105
(5)
_
.1 x 107
(6)
.9 x 105
(10)
.5 x 106
(6)
.3 x 106
(2)
.32 x 106
(46)
6005, SS, and Nitrogen expressed as mg/1 (arithmetic mean) and collform
densities expressed as org/100 ml (geometric mean).
Nunber of samples.
15-3
(195)
-------
This was about 36% of the design flow. The mean BOD concentration
was 217 mg/1. Corresponding BOO^. values of 138 mg/1 (1), 132 mg/1 (2).
and 152 ng/1 (3) reported in Wisconsin and 120 mg/1 (4) reported in
Connecticut were somewhat lower but a study in Canada (5) reported a value
of 240 mg/1. Suspended solids concentration in Oregon septic tank
effluents averaged 146 mg/1. This ranged from 1.7 to 4.2 times higher than
Corresponding SS concentrations reported in Wisconsin,
Connecticut, and Canada (3, 4, 5, 6, 7).
BOD,, and SS values lror System 6 (Table 15-3) were abnormally low. The home
owners I'ollowed the practice of flushing a septic tank treatment tablet
down the toilet each day. The tablet manufacturer alleged the product
would increase septic tank treatment effectiveness. Special biodegradable
toilet paper was used exclusively. In addition, no household garbage
disposal unit was used and grease, oils, and fats were removed from dishes
and pans and discarded prior to washing. These factors may have lowered
the BODc and SS concentration in the septic tank effluent.
The total nitrogen concentration was 57.5 mg/1 (Table 15-3). Studies in
Wisconsin (3, 4, 5, 8) reported concentrations that ranged from slightly
below to slightly above this value. More than 99X of the inorganic
nitrogen was in the reduced form indicating the anaerobic nature of the
septic tank.
Total coliform and fecal colifortn concentrations were similar to those
commonly reported (9, 10, 11).
15-4
(196)
-------
INDUSTRIAL SEPTIC TANK EFFLUENT QUALITY
Characterltics of 2 industrial septic tank effluents are shown 1n
Table 15-4.
TABLE 15-4. CHARACTERISTICS OF 2 INDUSTRIAL SEPTIC TANK EFFLUENTS.
SEPTIC TANK EFFLUENT CHARACTERISTICS1
Ave.
Flow
Systan (gpd) ECCV SS ND-> N
03 HF3 TKW TN FC TC
1. (International 3000 53.6. 39.6 O.CX 1.18 49 76.3 77.47 3.4X105
Paper Corp.) (11)? (8) (11) (10) (3) (8) (8) (10) (6)
ri.-wT 3D 161 33 0.05 0.65 50 72.8 73.5 9.5x10* 5.M05
Ire.) (9) (9) (9) (9) (9) (9) (9) (9) (9)
1550 102 36.1 0.04 0.9» 49.5 74.4 75.4 ZJxlO5 4.4x10?
(2) (3D) (17) (2)) (33) (19) (17) (17) (18) (7)
AriUrvtlc
AWT age
' BCDt;, SS, and Nitrogen exprr'.scd as ir«yi farlthrrtlc mean) and fecal and total
coWorm opressed as org/100 ml (gDcnrtrlc rnwn).
' Nurfcer of sarpls.
Total conform and fecal conform concentrations were similar to household
septic tank effluent because of the toilet facilities, but total nitrogen
and armonla nitrogen were considerably higher. Average BOD and SS
concentrations were 501 and 25X of those 1n household waste streams.
Unfortunately, no data from comparable Industrial facilities were available
for comparison.
15-5
(197)
-------
REFERENCES
U. S. Environmental Protection Agency, 1970. Methods of Chemical
Analysis of Water and Wastes, EPA-6CO/4-79-020, Environmental
Monitoring and Support Laboratory, Cincinnati, Ohio.
American Public Health Association. 1975. Standard Methods for
Examination of Water and Wastewater. Prepared and published
jointly by: American Water Works Association, Water Pollution
Control Federation, and American Public Health Association, 1740
Broadway, New York, N.Y.
Small Scale Waste Management Project. 1978. University of Wisconsin-
Madison, Management of Small Waste Flows. EPA-600/2-78-173,
Municipal Environmental Research Laboratory, Office of Research and
Development, U. S. Environmental Protection Agency, Cincinnati,
Ohio.
Harkln, J. M., C. J. Fitzgerald, C. P. Duffy, and D. G. Knoll. 1979.
Evaluation of Mound Systems for Purification of Septic Tank
Effluent. WIC WRC 79-05. later Resources Center, University of
Wisconsin, Madison, Wisconsin, pp. 87.
Otis, R. J., W. C. Boyle, and D. K. Sauer, 1974. The Performance of
Household Wastewater Treatment Units 'Jnder Field Conditions: In
Proceedings of the National Home Sewage Disposal Symposium,
American Society of Agricultural Engineers, St. Joseph, Michigan,
pp. 191-201.
Laak, R., 1973. Wastewater Disposal Systems 1n Unserfered Areas. Final
Report to Connecticut Research Commission, Civil Engineering
Department, University of Connecticut, Storrs, Connecticut.
Bernhart, A. P., 1967. Wastewater from Homes. University of Toronto,
Toronto, Canada.
Thomas, R. E. and T. W. Bendixen. 1969. Degradation of Wastewdter
Organlcs 1n Soil. JWPCF 41(5):808.
Zlebell, W. A., D. H. Nero, J. F. Deinlnger, and E. McCoy. 1975. Use
of Bacteria in Assessing Waste Treatment and Soil Disposal
Systems. In: Home Sewage Disposal, ASAE publ. PROC-175, St.
Joseph, Michigan.
15-6
(198)
-------
10 Bouma, J.. J. C- Converse, W. A. Zlebell and F. R. Magdoff. 1973. An
Experimental Mound System for Disposal of Septic Tank Effluent 1n
Shallow Soils Over Creviced Bedrock. International Conference on
Land for Waste Management. Ottawa, Canada.
11 Sauer, D. K., 1976. Treatment Systems Required for Surface Discharge
of On-S1te Wastewater. Individual On-S1te Wastewater Systems,
NSF. Proceedings from Third National Conference, Ann Arbor,
Michigan, 1977, p. 120.
G0670 15-7
(199)
-------
CHAPTER 16
SUBSURFACE SYSTEM COST
Selecting the proper on-site subsurface treatment and disposal system
involves the process of evaluating technical feasibility, environmental
acceptability, and cost effectiveness of various alternatives.
Professional staff have responsibility for realistically applying
regulations (Appendix C) to insure adequate long-term sewage treatment and
disposal with a minimum hazard to the environment. As a result, some
individual property owners are denied freedom to use their property as they
choose. More often, they are denied a permit to install a standard
«
subsurface treatment and disposal system but are given the option of
installing an alternative system designed to overcome specific limitations
of their site. Table 16-1 assists in selection of options applicable to
various site limitations. Once the options are identified the property
owner can determine which system is the most feasible to construct.
Alternative systems are usually more complex and more expensive to
construct and maintain than standard subsurface systems. Estimates of
capital and operation and maintenance costs of each on-site system allows
the owner to decide if it is economically feasible to develop his property
and which alternative is the most cost effective.
Cost estimates were developed primarily from information obtained from
construction and operation of on-site systems developed in the On-site
16-1
(201)
Preceding page blank
-------
TAflLE 16-1. OREGON ON-SITE SUBSURFACE SYSTEMS VS. SITE CONSTRAINTS
Is)
o
SITE CONSTRAINTS
a
a
a
a
a
a
b
b
b
b
b
b
VERY RAPID
SYSTEM RAPID
Standard Subsurface System
Capping fills X
Evapotranspir alien
Absorption
Pressurized Distribution X
Intermittent Sand Filter X
System
Steep Slope System
Tile Dewatering Systea X
Split Waste System
Disposal Trenches in Soils
with Slo. and Very Slow
Permeabilities
Seepage Trenches in Soils
with Slow arid Very Slow
Permeabilities
Disposal Trenches in Soils
Shallow to Our 1 pans.
saproliteor fractured
bedrock
Pressurized Distribution X
Trenches in Soils Shallow
to Grounowater
Evaportranspiratton Bed X
Hounds X
SOLID BEDROCK
SOIL PER-€A3ILITY OR SOIL PANS
MODERATELY SLOW
HfflERATE VERY SLOW
MODERATELY RAPID SLOW SHALLOW DEEP
X X
X XX
X X
X X
X X XX
X X
X X
X X
X XX
X X
XXX
X X
X X XX
X X
DEPTH TO SAPROLITE
Oft FRACTLRED BEDROCK
SHALLOW DEEP
X
X X
X
X
X X
X
X
X
X X
X
X
X
X X
X
GROUNDUATER SLOPE
SHALL
SHALLOW DEEP 0-12* 12-30* 30-45X LOT
XXX
XXX
X X (15t)
XXX
XXX X
X X
X (3X)
XXX
X X (20*)
XXX
(10J «1n)
XXX
x (a)
XXX
X X
* Means system can function effectively with that constraint.
» Alternative systems established on the basis of Oregon i Experimental Progrjn.
b Experimental systems which have not been adopted as alternative systems.
-------
Experimental Systems Program. Plans and specif Ications were prepared by
the Department of Environmental Quality (DEQ) staff. Systems w^ra
constructed either by the individua- land owner or by a licensed installer
contracted by the land owner. Cost ranges reflect variations in labor and
material costs. All costs were based on 1981 dollars.
RESULTS AND DISCUSSION
The standard system had the lowest construction cost and operation and
maintenance cost (Table 16-2). Construction costs were low because of the
Table 16-2. SUBSURFACE SYSTEM CONSTRUCTION AND OPERATION
_ AND MAINTENANCE COSTS ($)
SYSTEM
CONSTRUCTION1
OPERATION AND
MAINTENANCE
Standard
Recirculating Sand Filter
Intermittent Sand Filter
Bottomless (No Disposal Field)
Concrete Lined Sand Filter
Intermittent Recirculating Sand Filter
Tile Dewatering
Seepage Trench
Steep Slope
Saprolite
Pressure Distribution
Evapotranspiration
Evapotranspi rat ion-Absorption
Mound
Compost Toilet
Gray Water
Septic Tank and Disposal Field
Trickle Filter ar.j Disposal Field
Sand Filter and Disposal Field
1,000 -
4,000 -
2,500 -
6,500 -
5,100 -
3,500 -
1,900 -
2,400 -
1,250 -
2,200 -
5,400 -
3. COO -
5,500 -
800 -
600 -
200 -
3,500 -
2,500
5,300
3,500
10,000
9,600
5,500
3,700
5,000
3,000
3,500
6,500
6,500
6,500
1,600
1,600
1,200
5,500
10.00
31.50
28.50
28.50
31.50
10.00
10.00
10.00
10.00
28.50
10.00
10.00
28.50
3.00
5.00
5.00
22.50
- 25. OO2
- 65. OO3
- 62. OO3
- 62. OO3
- 65. OO3
- 25. OO2
- 25. OO2
- 25. OO2
- 25 OO2
- 62. OO3
- 25. CO2
- 25. OO2
- 62. OO3
- 5.004
- 12.50$
- 12.505
- 50. OO6
1 Based on cost of individual components (Table 16-3).
2 Annual cost based on pumping septic tank every 5 years.
3 Annual cost based on power at 4£/KWH, pump replacement every 10 years, and
pumping septic tank every 5 years.
4 Annual cost based on power at 4^/KWH and fan replacement every 10 years.
\ Annual cost based on pumping septic tank every 30 years.
6 Annual cost based on power at 4^/KWH, pump replacement every 10 years, and
pumping septic tank every 10 years.
16-3
(203)
-------
simplicity of the system. The only operation and maintenance cost was
pumping the septic tank every 5 years. Systems installed in saprolite were
slightly more expensive to install because saprolite was more difficult to
excavate than sell. The steep slope system utilized the same components as
the standard system, but the construction cost was considerably higher.
This was due to added labor cost associated with installing a disposal
field on slopes up to 45%. Hand labor was required to dig most of the
disposal trenches and wooden retaining walls were constructed to retain
soil backfill on the steep slopes. Gravel filter material and backfill was
installed by hand in most systems. Seepage trenches in soils with slow and
very slow permeability (Chapter 6) also used the same components as a
standard system, but construction costs were higher because deeper trenches
were used requiring more gravel filter material. In addition, the fine-
textured soils were more difficult to work and more equipment time was
required to excavate and Backfill seepage trenches.
The tile dewatering system used, in addition to the same components as a
standard system, a tile drainage system installed around the disposal
field. This increased the construction cost about $2,500.
Sand filter systems were the most expensive to construct, operate, and main-
tain because of the complexity of the system, cost of additional components
(Table 16-3), and operation and maintenance costs. The bottomless inter-
mittent sand filter (Chapter 3) was the least expensive of the sand filters
because the sand bed was placed into an excavation in saprolite. No liner
was us id and no disposal field was installed. Treated effluent discharged
16-4
(204)
-------
TABLE 16-3. COST OF INDIVIDUAL COMPONENTS OF ON-SITE SEWP5E SYSTEMS
COMPONENT
Septic Tank
Septic Tank Installation
Drop Box, Distribution Box
Disposal Trench (Per Foot)
Sand and Gravel (Per Yard)
Concrete (Per Yard in Place)
Pump
Electrical Controls
Pump Tank (Installed)
Vinyl Liner and Boots
COST
350.00
100.00
30.00
4.50
8.5C
95.00
165.00
150,00
350.00
150.00
($)
- 450.00
- 200.00
- 40.00
- 5.50
- 11.00
- 125.00
- 350.00
- 200.00
- 500.00
- 300.00
directly into underlying saprolite. The concrete-lined intermittent sand
filter and the concrete-lined intermittent rec .culating sand filter were
the most expensive. The vinyl-lined recirculating sand filter was
intermediate in cost. Construction costs for the mound system were about
the same as they were for the viyl-lined intermittent sand filter.
Operation and maintenance cost for these systems ranged from $28 to $65
per year (Table 16-2).
Pressure distribution systems were about $1,000 more expensive to install
than a standard system because of component costs (Table 16-3) and
additional labor costs.
16-5
(205)
-------
The evapotranspiration system was a proprietary system and the cost was set
by the manufacturer. The evapotransplratlon-absorption system was
expensive because of its size and the amount of gravel filter material
used.
An on-site sewage system consisting of a composting toilet and gray water
system was more expensive than a standard system because of the cost of the
composting toilet.
CONCLUSIONS
The standard system is the most cost-effective and trouble-free system if
suitable soils occur on the site. If suitable soils do not occur on-site,
a detailed site evaluation report identifies suitable alternative system
options. If more than one alternative system is feasible, final selection
car De based on cost analyses.
XG1125 16-6
(206)
-------
APPENDIX A
OREGON ADMINISTRATIVE RULES
CKAPTER 340 - DEPARTMENT OF ENVIRONMENTAL QUALITY
DIVISION 74
EXPERIMENTAL SEWAGE DISPOSAL SYSTEMS
Statement of Pel icy
340-74-004 The Environmental Quality Commission recogni^s:
(1) Alternative technologies to conventional septic and drainfield
sewage disposal systems are needed in areas planned for rural or low
density development.
(2) Standards for alternative disposal systems must be de .-a loped
based on information obtained from a controlled program of field testing
and evaluation.
(3) Funds available to the State of Oregon for testing the
acceptability of alternative systems are limited. Careful selection of the
types and numbers of systems to be studied is necessary.
10-15-78 A-l
(207)
-------
OREGON ADMINISTRATIVE RULES
CHAPTER 340 - DEPARTMENT OF ENVIRONMENTAL QUALITY
(4) The testing of alternative systems requires the cooperation of
citizens willing to risk investing money on an experimental system which
may fail and require replacement.
(5) An experimental program is not intended to serve as the last
resort for obtaining an on-site sewage disposal permit where all other
attempts to get a permit fail.
(6) Any program of experimentation must be carried out with the
recognition failures will occur. Appropriate steps must be taken to insure
adequate protection of public health, safety, welfare, and the potential
purchasers of properties where experimental systems are installed.
Therefore, it is the policy of the Commission that the Department
pursue a program of experimentation to obtain sufficient data for the
development of alternative disposal systems, rules and standards which may
benefit significant numbers of people in areas of need within Oregon.
Statutory Authority: ORS 454.625
Hist: Filed and Eff. 3-1-78 as DEQ 1-1978
340-74-005 Filed 9-2-75 as OEQ 98,
Eff. 9-25-75
Repealed by DEQ 1-1978,
Filed and Eff. 3-1-78
10-15-78 A-2
(208)
-------
OREGON ADMINISTRATIVE RULES
CHAPTER 340 - DEPARTMENT OF ENVIRONMENTAL QUALITY
Definitions
340-74-010 All definitions under ORS 468.700 and OAR 340-71-010 and
34Q-74-010 shall apply as applicable.
Statutory Authority: ORS 454.625
Hist: Filed and Eff. 3-1-78 as DEQ 1-1978
Minimum Criteria for Selecting Experimental Sites
340-74-011 The Commission recognizes minimum criteria are necessary
for selecting experimental disposal systems sites. Sites may be considered
for experimental permit issuance where:
(1) Soils, climate, groundwater, or topographical conditions are
common enough to benefit large numbers of people. Sites will not be
considered for permit where soils, climate, groundwater, or landscape have
little in common with other areas.
(2) A specific acceptable backup alternative is available in the
event the experimental system fails.
Backup alternatives may include, but are not limited to, repair,
expansion, connection to a sewer, installation of a different system, or
abandonment of site.
(3) For absorption systems, soils in both original development and
expansion areas are similar.
(4) Installation of a particular system is necessary to provide a
sufficient data sampling base.
10-15-73 A-3
(209)
-------
OREGON ADMINISTRATIVE RULES
CHAPTER 340 - DEPARTMENT OF ENVIRONMENTAL QUALITY
(5) Zoning, planning, and building requirements allow system
installation.
(6) A single family dwelling or its waste water producing equivalent
will be served.
(7) The permitted system will be used on a continuous basis during
the life of the test project.
(8) Resources for monitoring, sample collection, and laboratory
testing are available.
(9) Legal and physical access for construction inspections and
monitoring are available to the Department.
(10) The property owner will record an affidavit notifying prospective
purchasers of the existance of an experimental system.
Statutory Authority: ORS 454.625
Hist: Filed and Eff. 3-1-78 as DEQ 1-1978
Preliminary Experimental System Proposals
340-74-012 The Commission and Department desire to minimize expenses
for potential experimental systems applicants until it can be determined
there is strong potential a proposal can be accepted for approval.
Therefore, the following procedures shall apply:
(1) A preliminary experimental proposal shall be directed to the
Department for review to determine if they meet minimum site selection
10-15-78 A-4
(210)
-------
OREGON ADMINISTRATIVE RULES
CHAPTER 34Q - DEPARTMENT OF ENVIRONMENTAL QUALITY
criteria. The Department will e/aluate the proposed experimental site to
help determine 1f It meets minimum site selection criteria.
(2) Where the Department finds a preliminary proposal meets minimum
site selection criteria, It will advise the prospective experimental
applicant to complete and file an application for permit pursuant to OAR
340-74-015. The Department will advise and assist the applicant to the
extent possible in this process.
(3) Where the Department finds minimum site selection criteria are
not met, the prospective experimental applicant will be advised against
making permit application.
Statutory Authority: ORS 454.625
Hist: F1l3d and Eff. 3-1-7S as DEQ 1-1978
Permit Required for Construction
340-74-013 Without first obtaining a specifically conditioned permit,
from the Department, no person shall construct or install an experimental
on-site treatment and disposal system.
Statutory Authority: ORS 454.625
H1st: Filed and Eff. 3-1-78 as DEQ 1-1978
10-15-78 A-5
(211)
-------
OREGON ADMINISTRATIVE RULES
CHAPTER .tap - DEPARTMENT OF ENVIRONMENTAL QUALITY,
340-74-015 Filed 9-2-75 as OEQ 98.
Eff. 9-25-75
Repealed by OEQ 1-1979,
Filed and Eff. 3-1-78
Procedures for Issuance or Denial of Pprmlts
340-74-016 (1) Application for permit shall be made on forms approved
and provided by the Department. All application forms must be completed 1n
full, si'jnrj by the applicant or his legally authorized representative, and
Accompanied by a fee as required under ORS 468.065(2).
Applicants shall Include detailed design specifications and plans, all
available laboratory or field test data and any additional Information the
Department considers necessary.
(2) The applicant shall agree In writing to hold the State of Oregon,
Its officers, employees, and agents harmless of any and all loss and damage
caused by defective Installation or operation of the proposed experimental
(3) The permit shall:
(a) Specify the method and manner of disposal system Installation,
operation, and maintenance.
(b) Specify the method, manner, and duration of the disposal
systems's testing and monitcrlng.
(c) Identify when and where system inspection.
10-15-78 A-6
(212)
-------
OREGON ADMINISTRATIVE RULES
CHAPTER 340 - DEPARTMENT OF ENVIRONMENTAL QUALITY
(d) Require prompt submission of monitoring and test data to the
Department.
(e) Require the permittee to have recorded under deed records in the
county where the experimertal system is located:
\A) An affidavit which informs future purchasers:
(i) That an experimental system has been installed on the site and is
undergoing Department evaluation;
(ii) That neither the Commission nor the Department imply, express, or
warrant the experimental system will operate satisfactorily; and
(iii) That if the Department finds the experimental system does not
operate satisfactorily and as a result threatens to create a public health
hazard or pollute state waters, the Department will require the system be
repaired so as to function properly, replaced, or be abandoned.
(B) An easement which provides the Department legal access for
monitoring the experimental system.
(4) Permits may be issued by the Water Quality Division Aviministrator
when the Department receives a completed experimental application and has
determined minimum criteria for experimental site selection can be met.
(5) Permits are not transferable. Permits shall be issued directly
to applicants.
(6) System construction and use are required within one (1) year of
permit issuance.
10-15-78 A-7
(213)
-------
OREGON ADMINISTRATIVE RULES
CHAPTER 340 - DEPARTMENT OF ENVIRONMENTAL QUALITY
(7) If the proposed experimental system is determined Ineligible, the
Hater Quality Division Administrator will notify the applicant of denial of
the permit and the reasons for denial.
(8) The decision by the Water Quality Division Administrator to
either issue or deny a permit may, upon request, be reviewed by the
Director of DEQ. The Director has the prerogative of affirming or
reversing the decision, or referring the matter to the Commission for a
decision.
Statutory Authority: ORS 454.625
Hist: Filed and Eff. 3-1-78 as DEQ 1-1978
W0956
10-15-78 A-8
(214)
-------
APPENDIX B
SITE SELECTION CRITEIA, 1978
1. Disposal Trenches in Soils Shallow to Duripans, Saprolite, and
Fractured Bedrock
A. Less Than 15 Inches Annual Precipitation
Minimum of 12 inches of soil.
Well drained soils.
Plane or convex slope at least 100 feet long with a gradient
of 25 percent or less.
B. 15 Inches to 35 Inches Annual Precipitation
Minimum of i2 inches of soil.
Well drained soils.
Plane or convex slope at least 100 feet long with gradient of
20 percent or less.
C. 35 Inches to 60 Inches Annual Precipitation
Minimum of 18 inches of soil.
Well drained soils.
Plane or convex slope at least 200 feet long with gradient of
20 percent or less.
2. Disposal Trenches in Subsoils with Slow or Very Slow Permeability
A. Less Than 15 Inches Annual Precipitation.
Minimum of 24 inches of soil.
Moderately well or well drained soils.
Plane or convex slope at least 200 feet long with gradient of
20 percent or less.
B-l
-------
1°
IS
I
B. 15 inches to 25 Inches Annual Precipitation
Minimum of 36 inches fine textured soil.
Moderately well or well drained soils.
Plane or convex slope at least 200 feet long with gradient of
10 to 20 percent.
3. Gray Waste Water Disposal Trenches
Minimum depth to restrictive or impervious layer 18 inches.
Minimum depth to temporarily perched groundwater 18 inches.
Minimum depth to permanent groundwater 48 inches.
Plane or convex slope at least 100 feet long with gradient of
25 percent or less.
For south facing slopes, up to 30 percent.
4. Mound
Permanent water table at least 36 inches below the soil surface.
Temporary water tabio at l°ast 18 inches below the soil surface.
Minimum of 18 inches of soil to a restrictive or impervious
1 ayer .
Plane or convex slope at least 200 feet long with gradient of
12 percent or less.
5. Evapotranspiration System
Potential evapotranspiration exceeds precipitation by at least
5 inches.
Plane or convex slope at least 200 feet long with gradient of
12 percent or less.
6. Evapotranspiration - Absorption System
A. Less Than 15 Inches of Annual Precipitation.
Minimum of 12 inches of soil.
Moderately well and well drained soils.
Plane or convex slone at least 200 feet long with gradient of
15 percent or less.
B-2
(216)
-------
B. 15 Inches to 25 Inches Annual Precipitation.
Minimum of 18 inches of soil.
Moderately well and well drained soils.
Plane or convex slope at least 200 feet long with gradient of
15 percent or less.
7. Sand Filter Followed by Disposal Trenches
Minimum depth to restrictive or impervious layer 18 inches.
Minimum depth to temoorary water 18 inches.
Minimum depth to pennanent water 42 inches.
Plane or convex slope at least 100 feet long with gradient of
25 percent or less.
8. Sand Filter in Gravelly Terrace Soils with Duripan
Minimum depth of groundwater 15 feet.
Plane or convex slope at least 100 feet long with gradient of 3
percent or less.
9. Seepage Trenches in Soils on Steep Slopes
Well drained soils.
Permeable soils with no restrictive or impervious layer within
5 feet of soil surface.
Plane or convex slope at least 100 feet long with gradient
between 25 percent to 45 percent.
10. Pressure Distribution System in Sandy and Gravelly Soils
A. Soils Less Than 30 Inches Deep to Coarse Grain Materials.
Minimum depth to groundwater 10 feet.
Plane or convex slope at least 100 feet long with gradient of
12 percent or less.
B-3
(217)
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B. Soils with iron cemented duripans that are rippable.
Somewhat poorly to well drained soils.
Soil that is rippable to depth of 48 inches.
Minimum depth to groundwater 10 feet.
Plane or convex slope at least 100 feet long with gradient of
12 percent or less.
11. Disposal Trenches in Drainabie Wet Soils
Site must have a natural outlet that will allow a field tile
to daylight when installed at least 6 feet deep in the area of
the proposed drainfield.
Drainabie soils with no restrictive or impervious layer within
6 feet of soil surface.
Plane or convex slope with gradient of 3 percent or less.
12. Low Pressure Distribution in Soils with High Water Tables
A. Silty Clay Loam, Silt./ Clay, Sandy Clay, and Clay Soil Textures,
30 inches or greater to groundwater utilizing a soil cap.
Less than 45 inches annual precipitation.
Plane or convex slope at least 100 feet long with a gradient
of 3 percent or less.
1 acre minimum.
8, Loam, Silt Loam, Clay Loam, and Sandy Clay Loam Soil Textures
36 inches or greater to groundwater utilizing a soil cap.
Less than 45 inches annual precipitation.
Plane or convex slope at least 100 feet long with a gradient
of 3 percent or less.
1 acre minimum.
B-4
(218)
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C. Sand, Loamy Sand, and Sandy Loam Soil Textures
42 Inches or greater to ground water utilizing a soil cap, or
30 inches to 42 inches to ground water utilizing a soil fill.
Plane or convex slope at least 100 feet long with a gradient
of 3 percent or less.
Less than 45 inches annual precipitation.
1 acre minimum for systems utilizing a soil cap.
Sufficient acreage, utilizing soil fills, so that borrow will
not be taken closer than 100 feet from the toe of the fill.
B-5
(219)
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APPENDIX C
STATE OF OREGON
DEPARTMENT OF ENVIRONMENTAL QUALITY
Oregon Administrative Rules
Chapter 340 - Division 71
Rules 260 - 320
(Alternative Systems)
Rules Current
as of
March 8, 1982
Preceding page blank
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APPENDIX C
TABLE OF CONTENTS
BY OAR NUMBER
DIVISION 71
OAR NUMBER TITLE PAGE
340-71-260 Alternative Systems, General C-3
340-71-265 Capping Fills C-3
340-71-270 Evapotranspiration-Absorption Systems .... C-5
340-71-275 Pressurized Distribution Systems C-6
340-71-280 Seepage Trench System C-10
340-71-285 ' Redundant Systems C-10
340-71-290 Sand Filter Systems C-ll
340-71-295 Conventional Sand Filter Design C-14
340-71-300 Other Sand filter Designs C-16
340-71-305 Sand Filter System Operation & Maintenance . C-17
340-71-310 Steop Slope Systems C-17
340-71-315 Tile Dewatering Systems C-18
340-71-320 Split Waste Systems C-19
C-2
(222)
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340-71-260 ALTERNATIVE SYSTEMS, GENERAL.
(1) For the purpose of these rules "Alternative system" means any
Commission approved on-site sewage disposal system used 1n Heu
of, including modifications of, the standard subsurface system.
(2) "Sewage Stabilization Ponds" and "Land Irrigation of Sewage"
are alternative systems available through the Water Pollution
Control Facilities (WPCF) permit program.
(3) Unless otherwise noted, all rules pertaining to the siting,
construction, and maintenance of standard subsurface systems
shall apply to alternative systems.
(4) General Requirements
(a) Periodic Inspection of Installed Systems. Where required by
rule of the Commission, periodic inspections of Installed
alternative systems shall be performed by the Agent. An
Inspection fee may be charged.
(b) A report of each inspection shall be prepared by the Agent.
The report shall 11st system deficiencies and correction
requirements and timetables for correction. A copy of the
report shall be provided promptly to the system owner.
Necessary follow-up •Intoections shall be scheduled.
340-71-265 CAPPING FILLS (Diagram 10^
(1) For the purposes of this rule, "Capping Fill" means a system
where the disposal trench effective sidewall 1s Installed a
minimum of twelve (12) Inches Into natural soil below a soil
cap of specified depth and texture.
(2) Criteria for Approval. In order to be approved for a capping
fill system, each site must meet all the following conditions:
(a) Slope does not exceed twelve (12) percent.
(b) Temporary water table !s not closer than eighteen (18)
Inches to the ground surface at anytime during the year.
A six (6) Inch minimum separation must be maintained between
the bottom of the disposal trench and the temporary water
table.
(c) Where a permanent water table 1s present, a minimum four
(4) feet separation shall be maintained between the bottom
of the disposal trench and the water table.
C-3
(223)
-------
(d) Where material with rapid or very rapid permeability is
present, a minimum eighteen (18) inches separation shall
be maintained between the bottom of the disposal trench
and soil with rapid or very rapid permeability.
(e) Effective soil depth is eighteen (18) inches or more below
the natural soil surface.
(f) So^l texture from the ground surface to the layer that
limits effective soil depth is no finer than silty clay
loan.
(g) A minimum six (6) inch separation shall be maintained
between the bottom of the disposal trench and the layer
that limits effective soil depth.
(h) The system can be sized according effective soil depth in
Table 4.
(3) Installation Requirements. The cap shall be constructed pursuant
to permit requirements. Unless otherwise required by the Agent,
construction sequence shall be as follows:
(a) The soil shall be examined and approved by the Agent prior
to placement. The texture of the soil used for the cap
shall be of the same textural class, or of one textural
class finer, as the natural topsoll.
(b) Construction of capping fills shall occur between June 1
and October 1 unless otherwise allowed by the Agent. The
upper eighteen (18) inches of natural soil must not be
saturated or at a moisture content which causes loss of
soil structure and porosity when worked.
(c) The drainfield site and the borrow site shall be scarified
to destroy the vegetative mat.
(d) Drainfield ihall be installed as specified in the
construction permit. There shall be a minimum ten (10)
feet of separation between the edge of the fill and the
nearest trench sidewall.
(e) Fill shall be applied to the fill site and worked in so
that the two (2) contact layers (native soil and fill) are
mixed. Fill material shall be evenly graded to a final
Jepth of sixteen (16) Inches over the gravel. Both initial
cap and repair cap may be constructed at the same time.
(f) The site shall be landscaped according to permit conditions
and be protected from livestock, automotive traffic or other
activity that could damage the system.
C-4
(224)
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(4) Required Inspections. The following minimum inspections shall
be performed for each capping fill installed:
(a) Both the drainfield site and borrow material must be
inspected for scarification, soil texture, and moisture
content, prior to cap construction.
(b) Pre-cover inspection of the installed drainfield.
(c) After cap is placed, to determine that there is good contact
between fill material and native soil (no obvious contact
zone visible), adequate depth of material, and uniform
distribution of fill material.
(d) Final inspection, after landscaping. A Certificate of
Satisfactory Completion may be issued at this point.
340-71-270 EVAPOTRANSPIRATION-ABSORPTION (ETA) SYSTEMS. (Diagram 6 & 7)
(1) For the purpose of these rules "Evapotranspiration-Absorption
System" means an alternative system consisting of a septic tank
or other treatment facility, effluent sewer and a disposal bed
or disposal trenches, designed to distribute effluent for
evaporation, transpiration by plants, and by absorption into
the underlying soii.
(2) Criteria for Approval. Installation permits may be issued for
evapotranspiration-absorption (ETA) systems on sites that meet
all of the following conditions:
(a) Mean annual precipitation does not exceed twenty-five (25)
inches.
(b) There exists a minimum of thirty (30) inches of moderately-
well to well drained soil. The subsoil at a depth of twelve
(12) inches and below shall be fine textured.
(c) Slope does not exceed fifteen (15) percent. Exposure may be
taken into consideration.
(3) Criteria for System Design. ETA beds shall be designed under the
following criteria:
(a) Beds shall be sized using a minimum eight hundred fifty
(850) square feet of bottom surface area per one hundred
fifty (150) gallons of projected daily sewage flow in areas
*here annual precipitation is fifteen (15) to twenty-five
(25) Inches, or six hundred (600) square feet of bottom
surface area per one hundred fifty (150) gallons of
projected daily sawage flow in areas where annual
precipitation is less than fifteen (15) inches.
C-5
(225)
-------
(b) Beds shall be Installed not less than twelve (12) Inches nor
deeper than twenty-four (24) Irches Into natural fine
textured soil on the downhill side and not more than thirty-
six (36) Inches deep on the uphill side.
(c) A mlninr.um of one (1) distribution pipe shall be placed 1n
each bed.
(d) The surface shall to be seeded according to permit
conditions.
(e) Other bed construction standards contained 1n Diagrams 6
and 7 shall apply.
340-71-275 PRESSURIZED DISTRIBUTION SYSTEMS.
(1) Pressurized distribution systems may be permitted on any site
meeting requirements for Installation of standard subsurface
sewage disposal systems, or other sites where this method of
effluent distribution 1s desired.
(2) Except as provided 1n OAR 340-71-220(2)(c), pressurized
distribution systems shall be used where depth to soil as defined
1n OAR 340-71-105 (84) (a) and (b) 1s less than thirty (36)
Inches and the minimum separation distance between the bottom of
the disposal trench and soil as defined 1n OAR 340-71-105 (84)
(a) and (b) 1s less than eighteen (18) Inches.
(3) Pressurized distribution systems Installed 1n soil as defined 1n
OAR 340-71-105 (34) (a) and (b) In areas with permanent water
tables shall not discharge more than four hundred fifty (150)
gallons of effluent per one-half (1/2) acre per day except where:
(a) A gray water system 1s proposed for lots of record existing
prior to January 1, 1974, which have sufficient area to
accommodate a gray water pressurized distribution system,
or
(b) Groundwater is degraded and designated as a nondevelopable
resource by the State Department of Water Resources, or
(c) A detailed hyd-ogeological study discloses loading rates
exceeding four hundred fifty (450) gallons per one-half
(1/2) acre oer day would not increase the nitrate-nitrogen
concentratorn in the groundwater beneath the site, or at
any down pr
-------
(A) All materials used 1n pressur1r°d •j'Stams shall be
structurally sound, durable, and caoable of
withstanding normal stresses Incidental to Installation
and operation.
(B) Nothing 1n these rules shall be construed to set aside
applicable building, electrical, or other codes. An
electrical permit wid Inspection from the Department
of Ccrr»rce or the municipality with Jurisdiction (ar
defined In ORS 456.750(5)) Is required for pump wiring
Installation.
(b) Pressurized Distribution Piping. Piping, valves and
fittings for pressurized systems shall meet the following
minimum requirements:
(A) All pressure transport, manifold, lateral piping, and
fittings shall meet or exceed the requirements for
Class 160 PVC 1120 pressure pipe as Identified 1n ASTM
Specification D2241.
(B) Pressure transport piping shall be uniformly supported
alonri tne trench bottom, and at the discretion of the
A^eat, it shall be bedded in sand or other material
approved by the Agent.
(C) Orifices shall be located en top of the pipe, except
In areas of extended frozen soil conditions 1n which
case the Agent may specify orifice orientation.
(D) The ends of lateral piping shall be provided with
threaded plugs or caps.
(E) All Joints 1n the manifold, lateral piping, and
fittings shall be solvent welded, using the appropriate
Joint compound for the pipe material. Pressure
transport piping may be solvent welded or rubber ring
Jointed.
(F) A gate valve shall be placed on the pressure transport
pipe, 1n or near the dosing tank, when appropriate.
(G) A check valve shall be placed between the pump and the
gate valve, when appropriate.
(c) Trench Construction.
(A) Minimum trench length required sha1! be not less than
that specified 1u Tables 4 and 5.
C-7
(227)
-------
(B) Drain-field trenches shall be constructed using the
specifications for the standard drainfield trench
unless otherwise allowed by the Department on a
case-by-case basis.
(C) Pressure lateral piping shall have not less than six
(6) inches of filter material below, nor less than
four (4) inches of filter material above the piping.
(D) The sides of ihe trench and top of the filter material
shall be lined or covered with filter fabric, or other
nondegrac'able material permeable to fluids that will
not allow passage of soil particles coarser than very
fine sand. In soils finer textured than loamy sand,
lining th3 sidewall may not be required.
(d) Seepage Bed Construction.
(A) Seepage beds may only be used in soil as defined in
OAR 340-71-105 (84) (a) and (b) as an alternative to
the use of disposal trenches.
(B) The effective seepage area shall be based on the bottom
area of the seepage bed. The minimum area shall be
not less than that specified in Table 9.
(C) Beds shall be installed not less than eighteen (IS)
inches (twelve (12) inches with a capping fill) nor
deeper than thirty six (36) inches into tiie natural
soil. The seepage bed bottom shall be levet.
(D) The top of the filter material shall be lined or
covered with filter fabric, or other nondegradable
material that is permeable to fluids but will not allow
passage of soil particles coarser than very fine sand.
(E) Pressurized distribution piping shall have not less
than six (6) inches of filter material below, nor
less than four (4) inches of filter material above the
piping.
(F) Pressurized distribution piping shall be horizontally
spaced not more than four (4) feet apart, and not more
than two (2) feet away from the seepage bed sidewall.
At least two (2) parallel pressurized distribution
pipes shall be placed in the seepage bed.
(G) A minimum of ten (10) feet of undisturbed earth shall
be maintained between seepage beds.
C-8
(228)
-------
(e) Notwithstanding other requirements of this rule, when the
projected daily sewage flow 1s greater than two thousand
five hundred (2500) gallons the Department may approve other
design criteria and standards it deems appropriate.
(5) Hydraulic Design Criteria. Pressurized distribution systems
shall be designed for appropriate head and capacity.
(a) Head calculations shall include maximum static lift, pipe
friction and orifice head requirements.
(A) Static lift where pumps are used shall be measured from
the minimum dosing tank level to the level of the
perforated distribution piping.
(B) Pipe friction shall be based upon \ Hazen Williams
coefficient of smoothness of 150. All pressure lateral
piping and fittings shall have a minimum diameter
of two (2) inches unless submitted plans and
specifications show a smaller diameter pipe is
adequate. The head loss across a lateral with multiple
evenly spaced orifices may be considered equal to one-
third (1/3) of the head loss that would result 1f the
entrance flow were to pass through the length of the
lateral.
(C) There shall be a minimum head of five (5) feet at the
remotest orifice and no more than a fifteen (15)
percent head variation between nearest and remotest
orifice in an individual unit.
(b) The capacity of a pressurized distribution system refers to
the rate of flow given in gallons per minute (gpm).
(A) Lateral piping shall have discharge orifices drilled
a minimum diameter of one-eighth (1/8) inch, and evenly
spaced at a distance not greater than twenty four (24)
inches in coarse textured soils or greater than four
(4) feet in finer textured soils.
(B) The system shall be dosed at a rate not to exceed
twenty (20) percent of the projected daily sewage
flow.
(C) The affect of back drainage of the total volume of
effluent within the pressure distribution system shall
be evaluated for Its Impact upon the dosing tank and
system operation.
C-9
(229)
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340-71-280 SEEPAGE TRENCH SYSTEM.
(1) For the purpose of these rules "Seepage Trench System1' means
a system with disposal trenches with more than six (6) inches
of filter material below the distribution pipe.
(2) Criteria for Approval. Construction permits may be issued by
the Agent for seepage trench systems on lots created prior to
January 1, 1974, for sites that meet all the following
conditions:
(a) Groundwater degradation would not result.
(b) Lot or parcel is inadequate in size to accommodate standard
subsurface system disposal trencnes.
(c) All other requirements for standard subsurface systems can
be met.
(3) Design Criteria. Seepage trench system dimensions shall be
determined by the following formula:
Length of seepage trench = (4) (length of disposal trench)/
(3 + 2D) where D = depth of filter material below distribution
pipe in feet. Maximum depth of filter material (D) shall be
two (2) feet.
340-71-285 REDUNDANT SYSTEMS. (Diagram 11)
(1) For the purpose of these rules "Redundant Disposal Field System"
means a system in which two (2) complete disposal systems are
installed, the disposal trenches of each system alternate with
each other and only one system operates at any given time.
(2) Criteria for Approval. Construction installation permits may be
Issued by the Agent for redundant disposal field systems to serve
single family dwellings on S'tes that meet all the following
conditions:
(a) The lot or parcel was created prior to January 1, 1974, and
(b) There is insufficient area to accommodate ? standard
system.
(3) Design Criteria.
(a) Each redundant disposal system shall contain two (2)
complete disposal fields.
(b) Each disposal field shall be adequate in size to accommodate
the projected daily sewage flow from the dwelling.
C-10
(230)
-------
:^¥***!3C9H(mT$!^«9''t%f£?&«n!]^^
(c) A minimum separation of ten (10) feet (twelve (12) feet on
centers) shall be maintained between disposal trenches
designed to operate simultaneously, and a minimim separation
of four (4) feet (six (6) feet on centers) sJaall be
maintained between adjacent disposal trenches.
340-71-290 SAND FILTER SYSTEMS.
(1) For the purpose of these rules:
(a) "Conventional sand filter" means a filter with two (2) tset
of medium sand designed to filter and biologically treat
septic tank or other treatment unit effluent from a pressure
distribution system at an application rate not to exceed one
and twenty-three hundredths (1.23) gallons per square foot
sand surface area per day, applied at a dose riot to exceed
twenty (20) percent of the projected daily sewage flow.
(b) "Medium sand" means a mixture of sand with 100 percer.t
passing the 3/8 inch sieve, 90 percent to 100 percent
passing the No. 4 sieve, 62 percent to 100 percent passing
the No. 10 sieve, 45 percent to 82 percent passing the
No. 16 sieve, 25 percent to 55 percent passing the No. 30
sieve, 5 percent to 20 percent passing the No. 50 sieve,
10 percent or less passing the No, 60 sieve, and 4 percent
or less passing the No. 100 sieve.
(c) "Sand filter system" means the combination of septic tank
or other treatment unit, a closing system with effluent
pump(s) and controls or dosing siphon, piping and fittings,
sand filter, absorption facility or effluent reuse method
used to treat sewage.
(2) Inspection Requirements. Each sand filter system installed under
this rule, ?nd those filters installed under OAR 340-71-038,
may be inspected annually. The Department may waive the annuel
evaluation fee during years when sand filter field evaluation
work is not performed.
(3) Sites Approved for Sand Filter Systems. Sand filters may be
permitted on any site meeting requirements for standard
subsurface sewage disposal systems contained under OAR 340-71-
220, or where disposal trenches (Including shallow subsurface
Irrigation trenches) woulJ be used, and all the following minimum
site conditions can be met:
(a) The highest level attained by temporary water would be:
C-11
(231)
-------
(A) Twelve (12) inches or more below ground surface where
gravity equal distribution trenches are used.
Pressurized distribution trenches may be used to
achieve equal distribution on slopes up to twelve (12)
percent; or
(B) Twelve (12) inches or more below ground surface on
sites requiring serial distribution where distribution
trenches are covered by a capping fill, provided:
trenches are excavated twelve (12) inches into the
original soil profile, slope-, are twelve (12) percent
or less, and the capping fill is constructed according
to provisions under OAR 340-71-265(3) and 340-71-265
(4)(a) through (c). A construction-installation permit
shall not be issued until the fill is in place and
approved by the Agent; or
(C) Eighteen (18) inches or more below ground surface on
sites requiring serial distribution where standard
serial distribution trenches are used.
(b) The highest level attained by a permanent water table would
be equal to or more than distances specified below:
*Minimum Separation
Distance from Bottom
Soil Groups Effective Seepage Area
(A) Gravel, sand, loamy sand,
sandy loam 24 inches
(B) Loam, silt loam, sandy
clay loam, clay loam 18 inches
(C) Silty clay loam, silty
clay, clay, sandy clay 12 'inches
*NOTE:
Shallow disposal trencht" (placed not less than twelve (12)
inches into the original soil profile) may be used with a
capping fill to achieve separation distances from permanent
groundwater. The fill shall be placed in accordance to
the provisions of OAR 340-71-265(3) and 340-71-265(4)(a)
through (c). A construction-installation pe;mit shall not
be issued until the fill is in place and approved by the
Agent.
C-12
(232)
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(c) Permanent water table levels shall be determined in
accordance with methods contained in subsection
340-71-220(1 )(d). Sand filters installed in soils as
defined in OAR 340-71-105 (84), in areas with permanent
water tables shall not discharge more than four hundred
fifty (450) gallons of effluent per one-half (1/2) acre
per day except where:
(A) A gray water system is proposed for lots of record
existing prior to January 1, 1974, which have
sufficient area to accommodate a gray water sand filter
system, or
(B) Groundwater is degraded and designated as a non-
developable resource by the State Department of Water
Resources, or
(C) A detailed hydrogeo logical study discloses loading
rates exceeding four hundred fifty (450) gallons per
one-half (1/2) acre per day would not increase nitrate-
nitrogen concentration in the groundwater beneath the
site, or any down gradient location, above five (5)
milligrams per liter.
(d) Soils, fractured bedrock or saprolite diggable with a
backhoe occur such that a standard twenty-four (24) inch
deep trench can be installed.
(e) Where slope is thirty (30) percent or less.
(4) Minimum Length Disposal Trench Required. The minimum seepage
area required for sand filter absorption facilities is indicated
in the following table:
Minimum Length (Linear Feet)
Disposal Trench Per One Hundred
Fifty (150) Gallons Projected
Soil Groups Daily Sewage Flow _
Minimum
(a)
(b)
Gravel, sand, loamy sand, sandy loam 35
Loam, silt loam, sandy clay loam,
clay loam 45
(c) Silty clay loam, silty clay,
sandy clay, clay 50
(d) Saprolite or fractured bedrock 50
(e) High shrink-swell clays (Vertisols) 75
C-13
(233)
-------
NOTE: Sites with saprolite, fractured bedrock, gravel or soil
textures of sand, loamy sand, or sandy loam in a
continuous section at least two (2) feet thick in contact
with and below the bottom of the sand filter, that meet
all other requirements of section 340-71-290(3), may
utilize either a conventional sand filter without a bottom
or a sand filter in a trench that discharges biologically
treated effluent directly into those materials. The
application rate shall be based on the design sewage flow
in OAR 340-71-295(1) and the basal area of the sand in
either type of sand filter. A minimum twenty-four (24)
inch separation shall be maintained between a water table
and the bottom of the sand filter.
(5) Materials and Construction.
(a) All materials used in sand filter system construction shall
be structurally sound, durable and capable of withstanding
normal installation and operation stresses. Component parts
subject to malfunction or excessive wear shall be readily
accessible for repair and replacement.
(b) All filter containers shall be placed over a stable level
base.
(c) In areas of temporary groundwater at least twelve (12)
inches of unsaturatecl soil shall be maintained between the
bottom of the sand filter and top of the disposal trench.
(d) Piping and fittings for the sand filter distribution system
shall be as required under pressure distribution systems,
OAR 340-71-275.
340-71-295 CONVENTIONAL SAND FILTER DESIGN AND CONSTRUCTION.
(Diagrams 8 and 9)
(1) Sewage Flows:
(a) Design sewage flows for a system proposed to serve a
commercial facility shall be limited to six hundred (600)
gallons or less per day unless otherwise authorized in
writing by the Department.
(b) Design sewage flows for a sy*;tan proposed to serve a single
family dwelling shall not be less than four hundred fifty
(450) gallons per day, except as provided in subsection (c).
(c) Design sewage flows for a system proposed to receive gray
water only from a single family dwelling shall not be less
than three hundred (300) gallons per day.
C-14
(234)
-------
(2) Minimum Filter Area. Sand filters shall be sized based on an
application rate of no more than one and twenty-three hundredths
(1.23) gallons septic tank effluent per square foot medium sand
surface per day.
(3) Sand filter container, piping, medium sand, gravel, gravel cover,
and soil crown material for a sand filter system discharging to
disposal trenches shall meet minimum specifications indicated in
Diagrams 8 and 9 unless otherwise authorized by thu Department.
(4) Container Design and Construction.
(a) A reinforced concrete container consisting of floor and
walls as shown in Diagrams 8 and 9 is required where water
tightness is necess iry to prevent groundwater from
infiltrating into the filter.
(b) Container may be constructed of materials other than
concrete where equivalent function, workmanship,
watertightness and at least a twenty (20) year service life
can be documented.
(A) Flexible membrane liner (FML) materials must have
properties which are at least equivalent to thirty (30)
mil unreinforced polyvinyl chloride (PVC) described in
OAR 340-73-085. To be approved for filter
installation, FML materials must:
(i) Have field repair instructions and materials which
are provided to the purchaser with the liner; and
(ii) Have factory fabricated "boots" suitable for field
bonding onto the liner to facilitate the passage
of piping through the liner in a waterproof
manner.
(B) Where accepted for use, flexible sheet membrane liners
shall be placed against relatively smooth, regular
surfaces. Surfaces shall be free of sharp edges,
corners, roots, nails, wire, splinters and other
projections which might puncture, tear, or cut the
liner. Where a smooth, uniform surface cannot be
assured in the field, filter system plans must include
specifications for liner protection. A four (4) inch
bed of clean sand or a non-degradable filter fabric
acceptable to the Agent, shall be used to provide liner
protection.
C-15
(235)
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340-71-300 OTHER SAND FILTER DESIGNS.
0) Other sand filters which vary in design from the conventional
sand filter may be authorized by the Department if they can be
demonstrated to produce comparable effluent quality.
(2) Pre-Application Submittal. Prior to applying for a construction
permit for a variation to the conventional sand filter the
Department must approve the design. To receive approval the
applicant shall submit the following required information to
the Department:
(a) Effluent quality data. Filter effluent quality samples
shall be collected and analyzed by a testing agency
acceptable to the Department using procedures identified
in the latest edition of "Standard Methods for the
Examination of Wastewater," published by the American Public
Health Association, Inc. The duration of filter effluent
testing shall be sufficient to ensure results are reliable
and applicable to anticipated field operating conditions.
The length of the evaluation period and number of data
points shall be specified in the test report. The following
parameters shall be addressed:
(A) BOD5
(B) Suspended solids
(C) Fecal coliform
(b) A description of unique technical features and process
advantages.
(c) Design criteria, loading rates, etc.
(d) Filter media characteristics.
(e) A description of operation and maintenance details and
requirements.
(f) Any additional information specifically requested by the
Department.
(3) Construction! Procedure. Following pre-appl ication approval, a
permit application shall be submitted in the usual manner.
Applications shall include applicable drawings, details and
written specifications to fully describe proposed construction
and allow system construction by contractors. Included must be
the specific site details peculiar to that application, including
C-16
(236)
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soils data, groundwater type and depth, slope, setbacks, existing
structures, wells, roads, streams, etc. Applications shall
include a manual for homeowner operation and maintenance of the
system.
340-71-305 SAND FILTER SYSTEM OPERATION AND MAINTENANCE.
(1) Sand filter operation and maintenance tasks and requirements
shall be as specified on the Certificate of Satisfactory
Completion. Where a conventional sand filter system or other
sand filter system with comparable operation and maintenance
requirements is used, the system owner shall be responsible for
the continuous operation and maintenance of the system.
(2) The owner of any sand filter system shall provide the Agent
written verification that the system's septic tank has been
pumped at least once each forty-eight (48) months by a licensed
sewage disposal service business. Service start date shall be
assumed to be the date of issuance of the Certificate of
Satisfactory Completion. The owner shall provide the Agent
certification of tank pumping within two (2) months of the date
required for pumping.
(3) No permit sha1! be issued for the installation of any other sand
filter which in the judgment of the Department would require
operation and maintenance significantly greater than the
conventional sand filter unless arrangements for system operation
and maintenance meeting the approval of the Director have been
made which will ensure adequate operation and maintenance of the
system. Each permitted installation may be inspected by the
Agent at least every twelve (12) months and checked for necessary
corrective maintenance. The Agent may waive the annual system
evaluation fee during years when the field evaluation work is not
performed.
340-71-310 STEEP SLOPE SYSTEMS.
(1) General conditions for approval. On-site system construction
permits may be issued by the Agent for steep slope systems on
slopes in excess of thirty (30) percent provided all the
following requirements can be met:
(a) Slope does not exceed forty-five (45) percent.
(b) The soil is well drained with no evidence of saturation.
(c) The soil has a minimum effective soil depth of sixty (60)
inches.
C-17
(237)
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(2) Construction requirements.
(a)
Seepage trenches shall be installed at a minimum depth of
thirty (30) inches and at a maximum depth of thirty-six
(36) inches below the natural soil surface on the downhill
side of the trench, and contain a minimum of eighteen (18)
inches of filter material and twelve (12) inches of native
soil backfill.
(b)
The system shall be
linear feet per one
daily sewage flow.
sized at a minimum of one hundred (100)
hundred fifty (150) gallons projected
340-71-315 TILE OEWATERING SYSTEM.
(1) General conditions for approval. On-site system construction
permits ,iiay be issued by the Agent for tile dewatering systems
provided the following requirements can be met:
(a) The site has a natural outlet that will allow a field tile
(installed on a proper grade around the proposed drainfield
area at a depth of not less than sixty-six (66) inches)
to daylight above annual high water.
(b) Soils must be silty clay loam or coarser textured and be
drainable, with a minimum effective soil depth of at least
sixty-six (66) inches.
(c) Slope does not exceed three (3) percent.
(d) All other requirements for standard on-site systens, except
depth to groundwater, can be met.
(2) Construction Requirements.
(a) Field collection drainage tile shall be installed a minimum
of sixty-six (66) inches deep on a uniform grade of two-
tenths to four-tenths (0.2-0.4) feet of fall per one hundred
(100) feet.
(b) Maximum drainage
center to center.
tile spacing shall be seventy (70) feet
(c) Minimum horizontal separation distance of drainage tile
from disposal trenches shall be twenty (20) feet center
to center.
(d) Field collection drainage tile shall be rigid smooth wall
perforated pipe with a minimum diameter of four (4) inches.
C-18
(238)
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(e) Field collection drainage tile shall be enveloped in clean
filter material to within thirty (30) inches of the soil
surface. Filter material shall be covered with filter
fabric, treated building paper or other nondegradable
material approved by the Agent.
(f) Outlet tile shall be rigid smooth wall solid PVC pipe with
a minimum diameter of four (4) inches. The outlet end shall
be protected by a short section of Schedule 80 PVC or ABS
or metal pipe, and a flap gate.
(g) A silt trap with a thirty (30) inch minimum diameter shall
be installed between the field collection drainage tile
and the outlet pipe. The bottom of the silt trap shall
be a minimum twelve (12) inches below the invert of the
drainage line outlet.
(h) The discharge pipe and dewatering system is an integral
part of the system.
(i) The Agent has the discretion of requiring demonstration
that a proposed tile dewatering site can be drained prior
to issuing a construction installation permit.
340-71-320 SPLIT WASTE SYSTEMS.
(1) For the purpose of these rules:
(a) "Split waste system" means a system where "black waste"
sewage and "gray water" sewage from the same dwelling or
building are disposed of by separate methods.
(b) "Black waste" means human body wastes including feces,
urine, other extraneous substances of body origin and toilet
paper.
(c) "Gray water" means household sewage other than "black
wastes", such as bath water, kitchen waste water and laundry
wastes.
(2) Criteria for Approval. In split waste systems wastes may be
disposed of as follows:
(a) Black wastes may be disposed of by the use of state
Department of Commerce approved nonwater-carried plumbing
units such as red rail ating oil flush toilets or compost
toilets.
(b) Gray water may be disposed of by discharge to:
(A) An existing on-site system which is not failing; or
C-19
(239)
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(B) A new on-slte s/stem with a soil absorption system
two-thirds (2/3) normal size. A full size Initial
dralnfield area and replacement area of equal size
are required; or
(C) A public sewerage system.
C-20
APPEND.C (240)
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APPENDIX 0
SITE SELECTION CRITERIA, 1981
1. Disposal Trenches 1n Drainable Soils with High Water Tables
A. Permanent Groundwater
Site must h,jve a natural outlet that will allow a field tile
to daylight when Installed at least 4 feet deep in the area of
the proposed dralnfleld.
Drainable soils with an effective soil depth of 4 feet.
Plane or convex slope with gradient of 3 percent or less.
Pressure Distribution = 80 feet/150 gallons
Gravity Distribution » 100 feet/150 gallons
8. Tenporary Groundwater
Site must have a natural outlet that will allow a field tile
to daylight when Installed at least 2 1/2 feet deep in the area
of the proposed drainfleld.
Drainable soils with an effective soil depth of 2 feet.
Plane or convex slope with gradient of 30 percent or less.
Pressure Distribution = 80 feet/150 gallons
Serial Distribution « 100 feet/150 gallons
2. Seepage Trenches in Soils on Steep Slopes
A. Less than 25 inches annual precipitation
Well drained, permeable soils with an effective soil depth of
2 1/2 feet.
D-l
(241)
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Plane or convex slope at least 100 feet long with gradient up
to 45 nprrpnt
to 45 percent.
50 feet-30 inch (18 inches gravel and 12 inches backfill) serial
seepage trench/150 gallons.
B. Greater than 25 inches annual precipitation
Well drained permeable soils with an effective soil depth of
3 1/2 feet.
Plane or convex slope at least 100 feet long with gradient up
to 45 percent.
50 feet-30 inches (18 inches gravel & 12 inches backfill) serial
seepage trench/150 gallons.
3. Seepage Trenches in Soils with Slow or Very Slow Permeability
A. 15 inches annual precipitation
Minimum of 24 inches of fine textured soil.
Moderately well or veil drained soils.
Plane or convex slope with gradient of 30 percent or less.
100 feet 36 to 42 inch (2 feet (minimum) gravel & 12 inches
backfill) serial seepage trench/150 gallons.
B. 15 to 40 inches annual precipitation
Minimum of 36 inches fine textured soil.
Moderately well or well drained soils.
Plane or convex slope with gradient of 10 to 30 percent.
150 feet 36 to 42 inch (2 feet (minimum) gravel & 12 inches
backfill) serial seepage trench/150 gallons.
D-2
(242)
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4. Disposal Trenches in Soils Shallow to Durlpans, Saprollte, or
Fractured Bedrock
A. Less than 15 Inches annual precipitation
Minimum of 6 Inches of soil dlggable to a depth of 24 Inches.
Well drained soils.
Plane or convex slope with a gradient of 30 percent or less.
100 feet serial disposal trench/150 gallons.
B. 15 Inches to 40 Inches Annual Precipitation
Minimum of 12 Inches of soil diggable to a depth of 24 Inches.
Well drained soils.
Plane or convex slope with gradient of 30 percent or less.
125 feet serial disposal trench/150 gallons.
5. Disposal Trenches with Low Pressure Distribution 1n Soils with High
Water Tables
A. Disposal Trenches in Natural Soil
1. Sand, loamy sand, and sandy loam soil textures.
Minimum depth to groundwater 4 feet.
Plane or convex slope with a gradient of 3 percent, or less.
2. Loam, silt loam, clay loam, and sandy clay loam soil
textures.
Minimum depth to groundwater 3 1/2 feet.
Plane or convex slope with a gradient of 3 percent, or less.
D-3
(243)
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"/I
3. Silty clay loam, silty clay, sandy clay, and clay soil
textures.
Minimum depth to groundwater 3 feet.
Plane or convex slope with a gradient of 3 percent or less.
80 feet pressure distribution trench/150 gallons.
B. Disposal Trenches Utilizing a 12 Inch Soil Cap
1. Sand, loony sand, and sandy loam soil textures.
Minimum depth to ground water 3 feet.
Plane or convex slope with a gradient of 3 percent or less.
2. Loam, silt loam, clay loam, and sandy loam soil textures.
Minimum depth to ground water 2 1/2 feet.
Plane or convex slope with a gradient of 3 percent or less.
80 feet pressure distribution trench/150 gallons.
C. Disposal Trenches Utilizing a Soil Fill
1. Sand, loamy sand, and sandy loam soil textures.
Minimum depth to ground water 2 feet.
Similar kind of soil borrow available to install a fill 2
feet thick.
Plane or convex slope with a gradient of 3 percent or less.
80 feet pressure distribution trench/150 gallons.
, x "
G0184.E (2) (244)
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APPENDIX E
PROGRESS REPORT
COMPOSTING TOILETS
February 28, 1978
By February 28, 1978, the Department of Environmental Quality had Issued
33 permits for composting toilets and gray wastewattr treatment and
disposal systems under the Experimental On-Site Program.
Staff contacted 22 permittees between February 3 and March 3, 1978. At
that time, 4 individuals stated they elected not to install their permitted
experimental systems, 12 had not completed construction on their homes,
11 compost toilets were in use, and 1 family had their compost toilet
(Biu-let) removed because of odor and liquid buildup problems.
Of the 11 units in use, 4 had fly problems (3 Clivus Multrums and 1 Toa-
Throne) during the summer months; 5 had odor problems (4 Ecolets and
1 Biu-Let); 7 have had liquid problems (2 B1u-Lets, 4 Ecolets and 1 Clivus
Multrum; twice, rising seasonal water tables leaked through an air intake
of 1 Clivus Multrum's compost chamber, filling the lower portion of the
chamber); and 1 Biu-Let became dehydrated (the owner had to add tap
water to the system from time-to-time).
The Department had issued permits for:
4 Toa-Thrones
19 Clivus Multrums (2 Toilets Authorized Under 1 Permit)
4 Biu-Lets
10 Ecolets (3 Toilets Authorized Under 1 Permit and
? on Another)
1 Drum Privy
The following toilets were in use:
1 Toa-Throne
5 Ecolets
1 Biu-Let
4 Clivus Multrums
E-l
(245)
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APPENDIX F
PROGRESS REPORT
COMPOSTING TOILETS
January 30, 1979
By January 30, 1979, 39 permits authorizing 42 compost toilet installations
had been issued under DEQ's Experimental Program.
Four individuals decided not to install their permitted toilets; 1 had been
deleted from the experimental program, and 11 people had not installed
their permitted toilets, but intended to do so.
Twenty-eight toilets were installed. They included:
2 Biu-Lets
3 The Compost Toilets
9 Ecolets
2 Toa-Thrones
11 Clivus Multrums
1 Drum Privy
Twenty toilets were in use; 2 had recently been installed and would soon be
used; ard 5 toilets, 1 Biu-Let and 4 Ecolets, were removed after owners
encountered severe operating difficulties.
In late December and early November 1978, twenty-three permittees who had
installed toilets were asked to complete a questionnaire to determine their
impression of toilet performance.
The following was reported:
I Flies - Fly problems were evident, especially when toilets were
initially used by 15 individuals. Toilets involved included:
7 Ecolets
2 The Compost Toilets
4 Clivus Multrums
2 Toa-Thrones
II Other insects - In 31 Instances, insects other than flies were
observed in:
1 Ecolet (gnats)
2 Clivus Multrums (spiders)
F-l
(247)
Preceding page blank
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Ill Excess liquid buildup was reported in 16 toilets
2 Biu-Lets
7 Ecolets
1 The Compost Toilet
1 Toa-Throne
5 Clivus Multrums
Owner estimates of excess liquid volumes were:
2 Biu-lets
1 unit filled to the top of the unit. The toilet was later
removed by the owner.
1 unit accumulated approximately 1 gallon excess liquid in
the front compost retrieval tray each month while its back
tray remained dry. The owner had to remove excess liquid at
2-month intervals.
1 The Compost Toilet
The owner reported 5 to 10 gallons excess liquid buildup per
month.
7 Ecolets
3 units filled to their tops. All were removed after
several bailings failed to control excess buildup problems.
2 units trays filled and had to be emptied by owners.
1 user reported a 1 to 1-1/2 gallon buildup following
initial use.
Another owner has had to remove 3 gallons of excess liquid.
1 Toa-Throne
The amount was not reported. The system owner concluded
moisture entered the toilet as rainfall through the unit's
vent stack.
5 Clivus Multrums
1 person had to remove 40 gallons twice. He attributed
buildup to rainfall and condensation entering the vent
stack.
F-2
(248)
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1 individual reported a 4" liquid buildup in the base of
the unit after startup. The level subsided with continued
toilet use.
1 owner has removed approximately 10 gallons of liquid
twice. He attributed liquid excess to periodic heavy use by
several people.
1 person removed 20 gallons he felt resulted from rainfall
entering the vent stack.
1 unit had to be bailed twice (approximately 40 gallons each
time) after seasonally perched groundwater entered through
its air intakes.
IV Excess waste accumulation was reported by 6 owners using:
1 Biu-Let
The unit filled to the top. The toilet was removed by the
owner.
5 Ecolets
1 unit filled partially. The owner had to remove excess
material.
4 units filled to the top. All wer^ eventually removed by
their owners.
V Compost was removed from the retrieval trays of 1 Biu-Let every 4
months. Some composted material was removed by a Toa-Throne
user.
VI Owners report using the following materials as carbon sources:
Material No. Using Material
Woodshavings, barkdust or sawdust 9
Kitchen Scraps 14
Peat Moss 18
Grass/Hay Clippings 2
Garden Litter 6
F-3
(249)
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VII Cost estimates for toilets - Costs include the amount paid to
purchase the unit in 1979. In some instances, installation costs
are included.
Toilet Average Cost
Biu-Let $ 613
The Compost Toilet 1400
Ecolet 670
Toa-Throne 1000
Clivus Multrum 1415
Drum Privy 50
F-4
(250)
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APPENDIX G
PROGRESS REPORT
Composting Toilets
December 18, 1979
In January 1979, the Department conducted a third survey on composting
toilet performance.
33 of 21 compost toilet users surveyed responded to a Department
questionnaire. Respondents represented the following toilets:
Type Number
Ecolet 6
The Compost 5
Clivus Multrum 9
Carousel 2
Biulet 1
Drum Privy 1
The toilets had been installed 3 to 42 months, and had been in use an
average of 19.3 months.
The total ccst for materials and installation ranged from $50 to $3,200
with an average of $1,058.
Materials placed in these units as carbon source materials Included:
Material Responses
Peat Moss 12
Straw 6
Trash 2
Garbage 12
Garden Debris 9
Other 6
Responses to questions about insect pests and their frequency of occurrence
follow:
Pest Constant Intermittent Initially Once or Twice None
7 5
2 12
1 15
0 16
Fruit Flies
House Files
Spiders
Beetles
0
0
1
0
3
2
0
0
6-1
(251)
2
1
0
1
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Problems with insect pests occurred during the following months:
Time Responses
June 5
July 6
August 5
September 2
February 1
In addition, 1 person reported problems during periods when his toilet was
not in use and another noticed insects after adding grass clippings.
Insect presence was reported as follows:
Status Responses
Disappeared Naturally 4
Eliminated by Pesticides 9
Remain all the time 2
The following pesticides were used by toilet owners:
Shell No-Pest Strips 4
Baytex 1
Rotenone 2
Ortho 1
Black Flat 2
Pyrethrin 1
Fly Paper 1
Excess liquid buildup was reported by 11 people, no buildup by 5.
2 people reported having had to remove and bury excess mass waste
materials.
15 users reported they could detect odors; 2 reported no obvious odors.
Odors were charcterized as:
Earthy 6
Sulfurous 1
Septic Tank Odor 1
Rotting Garbage 3
Other (not able to describe) 4
6-2
(252)
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Odors detected:
Inside the Toilet 9
Outside, Near Toilet 1
When Compost Collection Hatch 3
was Opened
Outside Near Toilet Vent 7
Stack
Other (undefined) 2
Toilet users were asked to express their views on overall toilet
acceptance. The following responses were reported:
The ratings were:
Corresponding Number
Uncertain 7
Unacceptable 1
Poor 2
Good 3
Very Good 4
Excellent 11
Users were asked if they would install a "composting toilet" in their next
home. The following responses were received:
Response No. Responding
Yes 12
No 2
Not Certain 2
Yes, as a backup toilet only 1
XG1162 G'3
(253)
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