U.S. patent application number 11/151547 was filed with the patent office on 2006-12-14 for drain field systems and methods for implementing same.
This patent application is currently assigned to Ring Industrial Group, L.P.. Invention is credited to Dennis Koerner, Carl D. Ring.
Application Number | 20060280557 11/151547 |
Document ID | / |
Family ID | 37524241 |
Filed Date | 2006-12-14 |
United States Patent
Application |
20060280557 |
Kind Code |
A1 |
Ring; Carl D. ; et
al. |
December 14, 2006 |
Drain field systems and methods for implementing same
Abstract
A drain field system including a trench having two sidewalls and
a floor, one or more perforated drainage pipes, and one or more
contained aggregate bundles placed in the vicinity of the drainage
pipe. In one application, a system includes two aggregate bundles
disposed on the floor of a trench with a drainage pipe placed
between the two bundles on the trench floor. In another
application, a drainage pipe is placed on top of two contained
aggregate bundles that have been placed side by side in a
trench.
Inventors: |
Ring; Carl D.; (Oakland,
TN) ; Koerner; Dennis; (Oakland, TN) |
Correspondence
Address: |
SUGHRUE MION, PLLC
2100 PENNSYLVANIA AVENUE, N.W.
SUITE 800
WASHINGTON
DC
20037
US
|
Assignee: |
Ring Industrial Group, L.P.
|
Family ID: |
37524241 |
Appl. No.: |
11/151547 |
Filed: |
June 14, 2005 |
Current U.S.
Class: |
405/43 ;
405/36 |
Current CPC
Class: |
E02B 11/005 20130101;
E03F 1/002 20130101 |
Class at
Publication: |
405/043 ;
405/036 |
International
Class: |
E02B 11/00 20060101
E02B011/00 |
Claims
1. A drain field system comprising, a trench having a first
sidewall, a second sidewall, and a floor; at least one perforated
drainage pipe; and at least one contained aggregate bundle, wherein
the at least one perforated drainage is pipe placed in the vicinity
of and outside of the at least one aggregate bundle.
2. The drain field system according to claim 1, wherein a first one
of the at least one contained aggregate bundle is disposed on the
floor of the trench and is in contact with the first sidewall of
the trench, wherein a second one of the at least one contained
aggregate bundle is disposed on the floor of the trench and is in
contact with the first one of the at least one contained aggregate
bundle, and wherein a first one of the at least one perforated
drainage pipe is disposed on the first and second ones of the at
least one contained aggregate bundle at a location above the point
where the second one of the at least one contained aggregate bundle
is in contact with the first one of the at least one contained
aggregate bundle.
3. The drain field system according to claim 2, wherein the second
one of the at least one aggregate bundle is in contact with the
second sidewall of the trench.
4. The drain field system according to claim 2, wherein a third one
of the at least one contained aggregate bundle is disposed on the
floor of the trench and is in contact with the second one of the at
least one contained aggregate bundles.
5. The drain field system according to claim 4, wherein the third
one of the at least one contained aggregate bundle is in contact
with the second sidewall of the trench.
6. The drain field system according to claim 5, wherein a second
one of the at least one perforated drainage pipe is disposed on the
second and third ones of the at least one contained aggregate
bundle at a location above the point where the third one of the at
least one contained aggregate bundle is in contact with the second
one of the at least one contained aggregate bundle.
7. The drain field system according to claim 1, wherein a first one
of the at least one contained aggregate bundle is disposed on the
floor of the trench, and wherein a first one of the at least one
perforated drainage pipe is located on the floor of the trench and
is in contact with the first one of the at least one contained
aggregate bundle.
8. The drain field system according to claim 7, wherein the first
one of the at least one contained aggregate bundle is in contact
with the first sidewall of the trench.
9. The drain field system according to claim 8, wherein a second
one of the at least one contained aggregate bundle is disposed on
the floor of the trench and is in contact with the first one of the
at least one perforated drainage pipe.
10. The drain field system according to claim 9, wherein the second
one of the at least one contained aggregate bundle is in contact
with the second sidewall of the trench.
11. The drain field system according to claim 10, wherein the first
one of the at least one perforated drainage pipe has approximately
the same diameter as the first and second ones of the at least one
contained aggregate bundle.
12. The drain field system according to claim 7, wherein a second
one of the at least one perforated drainage pipe is disposed on the
floor of the trench and is in contact with the first one of the at
least one drainage pipe.
13. The drain field system according to clam 12, wherein a second
one of the at least one contained aggregate bundle is disposed on
the floor of the trench and is on contact with the second one of
the at least one perforated drainage pipe.
14. The drain field system according to claim 13, wherein a third
one of the at least one perforated drainage pipe is disposed above
and in contact with the first one of the at least one perforated
drainage pipe, and is in contact with the first one of the at least
one contained aggregate bundle, and wherein a fourth one of the at
least one perforated drainage pipe is disposed above and in contact
with the second one of the at least one perforated drainage pipe,
and is in contact with the second one of the at least one contained
aggregate bundle.
15. The drain field system according to claim 1, wherein each of
the at least one contained aggregate bundles comprises: a plurality
of lightweight aggregates; and a porous sleeve.
16. The drain field system according to claim 15, wherein the
plurality of lightweight aggregate is comprised of at least one of
expanded polystyrene and Styrofoam.
17. The drain field system according to claim 16, wherein the
plurality of lightweight aggregates comprise a first annular area
containing a first aggregate material and a second circular area
within the first annular area containing a second aggregate
material.
18. The drain field system according to claim 17, wherein the first
aggregate material is expanded polystyrene and the second aggregate
material is rubber chips.
19. The drain field system according to claim 1, wherein
drainfields having dimensionally similar characteristics to
conventional gravel trenches provide a percent increase in volume
per trench foot of at least 5%.
20. The drain field system according to claim 1, wherein
drainfields having dimensionally similar characteristics to
conventional gravel trenches provide a percent increase in volume
below the pipe invert of at least 5%.
21. A method of installing a drain field comprising: excavating a
trench, placing at least one contained aggregate bundle on the
floor of the trench, and placing at least one perforated drainage
pipe on top of the at least one contained aggregate bundle.
22. The method according to claim 21, wherein: a first one of said
at least one contained aggregate bundle is placed on the floor of
the trench in proximity to a first sidewall of the trench, a second
one of said at least one contained aggregate bundle is placed on
the floor of the trench in proximity to a second sidewall of the
trench, the first and second ones of said at least one contained
aggregate bundle contact one another a first one of the at least
one perforated drainage pipe is placed on top of and in between the
first and second ones of said contained aggregate bundles.
23. The method according to claim 21, wherein: a first one of said
at least one contained aggregate bundle is placed on the floor of
the trench in proximity to a first sidewall of the trench, a second
one of said at least one contained aggregate bundle is placed on
the floor of the trench in proximity to a second sidewall of the
trench, a first one of the at least one perforated drainage pipe is
placed on the floor of the trench between the first and second ones
of said at least one contained aggregate bundle.
24. A method of installing and operating a drain field, the method
comprising: placing at least one contained aggregate bundle in a
trench; placing at least one perforated drainage pipe over the at
least one contained aggregate bundle; running organic matter
through the perforated drainage pipe to allow the organic matter to
penetrate the at least one contained aggregate bundle, wherein the
contained aggregate bundle is used to disperse organic material
over the aggregate, and wherein aggregate contained in the at least
one contained aggregate bundle is used to provide surface area for
attached microbial growth and subsequent treatment and breakdown of
the organic material.
25. The method according to claim 24 wherein the perforated
drainage pipe is placed in direct contact with a soil interface of
the trench.
Description
FIELD OF THE INVENTION
[0001] This invention relates to drain field systems in which
preassembled aggregate bundles are arranged together with drainage
pipes in trenches used in fields, including fields used for
exfiltration or infiltration applications, and methods employing
the same.
BACKGROUND OF THE INVENTION
[0002] Gravel-based drain field systems are one of the oldest and
most prevalent types of liquid drainage systems. Gravel-based drain
fields are constructed by placing a layer of gravel 18a in an
excavation or trench 16 as shown, for example, in FIGS. 1A-1B. A
drainage pipe 20, e.g., a 4-inch diameter pipe, made from any
number of well-known materials, including polyvinyl chloride (PVC)
or high density polyethylene (HDPE), and containing distribution
holes or perforations, is then placed on top of the gravel 18a. The
perforated drainage pipe 20 is then covered with additional gravel
18b. Finally, soil or other suitable backfill 19 is placed on top
of the gravel 18b. The popularity of gravel-based drain field
systems can be attributed to their characteristics. For example,
gravel-based drain field systems, such as those shown in FIGS.
1A-1B, have the following characteristics: [0003] the gravel
provides for underground void volume to contain and convey liquid
surge events; [0004] the gravel surrounding the drain pipe prevents
soil intrusion into the void spaces due to the tortuosity of the
void space path; [0005] the gravel provides for excellent
structural integrity and support of the surrounding soil as
compared to non-aggregate systems, thereby insuring a relatively
long useful life for the system; [0006] liquids flow through the
gravel both horizontally and vertically, insuring that both the
trench sidewalls and the trench bottom are used as effective
infiltrative and exfiltrative surface areas, whereas other
alternative drainage systems may rely primarily on the trench
bottom area only or have a limited hydraulic head which results in
reduced flow through the sidewall portion of the system; [0007] in
exfiltration applications, the gravel displaces some of the volume
in the trench so that each dosing event will cause a higher
hydraulic pressure which in turn increases the wetted perimeter of
the trench, and increases the infiltrative surface area, thereby
promoting faster absorption of the media-contained liquid into the
surrounding soil; and [0008] gravel-based drainage systems
typically have a higher soil interface to volume ratio than other
non aggregate type drain field products such as a pipe, a
multi-pipe bundle or a chamber system due to the lower porosity of
the gravel. This increased soil interface to volume ratio is
desirable for distribution of liquids containing organic matter
such as septic tank effluent as systems having such a higher ratio
allows for faster absorption of liquid over an extended period of
time due to reduced rates of microbial growth in the soil.
[0009] Despite their popularity, gravel-based drain field systems
suffer from significant limitations. For example, gravel systems
are relatively heavy and require significant labor to be properly
placed in a trench. Due to its weight, shipping heavy gravel to an
installation site can be a daunting undertaking, particularly in
remote locations or in locations where heavy vehicle travel is
difficult. Also, due to its weight, placement of gravel in a trench
requires either heavy machinery or difficult and time consuming
manual labor. The heavy weight of the gravel when placed into the
trench can also embed into the soil and cause compaction of the
soil at the trench bottom. This compaction or embedment of the
gravel into the soil at the trench bottom reduces the ability of
the system to exfiltrate the effluent into the soil at the trench
bottom by restricting the area of undisturbed soil available for
exfiltration. Another limitation of the gravel is that it contains
fines that can significantly reduce the flow rate of effluent into
the soil. Even cleaned, screened, and washed gravel contains small
quantities of fines. Over time, these fines settle to the bottom of
the trench and increase the flow resistance of the effluent into
the surrounding soils, thereby reducing the effectiveness of the
system. In addition, gravel can be an expensive material and its
use results in damage to the environments and in some areas,
depletion of a limited resource.
[0010] The limitations of a gravel drainage system are well known
and have been addressed in the marketplace with range of
alternative products including chambers, pipe systems and
lightweight aggregate systems. In U.S. Pat. No. 5,015,123 to Houck
et al. (the '123 patent), the disclosure of which is hereby
incorporated by reference, certain improvements to the design of
the gravel-based drain field systems were disclosed. The '123
patent disclosed a preassembled unit for a sewage nitrification
fields made of loose, lightweight plastic aggregate material
enveloped and bound by a plastic sleeve with a horizontal conduit
or perforated drainage pipe located within the plastic sleeve. See,
for example, the abstract and FIG. 2 of the '123 patent. These
preassembled units allow for relatively easy installation in
comparison to gravel drain field systems, while providing savings
in machinery and labor costs related to delivery and
installation.
[0011] Additional benefits provided by the use of the '123 patent
include greater void volume per unit of trench foot and improved
performance due to the absence of fines and no embedment of the
lightweight plastic aggregate material or compaction of the soil at
the trench bottom.
[0012] The disclosure of the '123 patent, however, is limited to
drain field systems containing a perforated drainage pipe located
entirely within the plastic sleeve, i.e., entirely within the
aggregate bundle as shown in FIG. 2 of the '123 patent. This
design, while an improvement over gravel drain field systems, has
significant performance limitations associated with it. For
example, systems designed in accordance with the '123 patent's
disclosure have less ability to store liquid below the pipe invert
during peak wastewater flows and require additional drainfield to
match the volume storage capacity of gravel-based drain field
systems as required by state and municipal onsite rules and
regulations. Systems consistent with the '123 patent's disclosure
utilize only the trench perimeter below the pipe invert for the
dispersal of organics, and it is this area where trench clogging
materials often accumulate. This relatively small area available
for the dispersal of organics and the accumulations of clogging
materials shortens the life and diminishes the performance of
drainfield systems. An increase in the area available for organic
growth would substantially increases the life of the drainfield
system by spreading the organics and the clogging material over a
larger area.
[0013] An additional limitation of the '123 patent disclosure is
the ability to place the conduit pipe and subsequent void channel
in a desired location. For example, typically in a French drain
used to dewater a foundation, the drainage pipe is placed on the
bottom of the trench and in direct contact with the soil.
Subsequently the gravel is placed on top of the pipe. In a septic
effluent dispersal system the drain pipe is placed towards the top
of the gravel in the trench. In the '123 patent, placement of the
pipe to extreme top or the extreme bottom of the aggregate is
prevented because the pipe is contained inside of the aggregate.
The '123 patent cannot be used to place the pipe in direct contact
with a soil surface associated with the trench.
[0014] Accordingly, a need existed in drain field technology for a
drain field system having improved performance, namely, increased
void volume per trench foot, increased void volume below the pipe
invert, increased hydraulic gradient, increased wetted soil
perimeter, increased media area for attached microbial growth,
increased soil interface area for dispersal of organic materials,
prevention or reduction of soil intrusion, and increased soil
interface area to volume ratios.
SUMMARY OF THE INVENTION
[0015] In view of the limitations of conventional drain field
systems, Applicant invented and discloses herein novel and
non-obvious drain field systems and methods for implementing the
same to overcome the limitations of gravel and '123 patented drain
field systems disclosed in the '123 patent. The systems and related
methods disclosed herein relate to a drain field system wherein the
efficiency and effectiveness of the system is significantly
improved by precise location of volume (in the form of aggregate
bundles) relative to perforated drainage pipes. The location of
volume relative to the drainage pipes and the trench infiltrative
area has a dramatic effect on critical performance measures and
regulatory acceptance of drain field systems.
[0016] The systems and related methods disclosed herein include a
one or more preassembled drainage line members consisting of
bundles of contained light-weight aggregate placed in the vicinity
of one or more perforated drainage pipes. These preassembled
bundles of contained aggregate can be of a size or length as needed
for the particular application. This system represents a
substantial improvement over gravel-based systems and systems as
disclosed in the '123 patent in that it allows for:
[0017] increased void volume per trench foot;
[0018] increased void volume below the pipe invert;
[0019] increased hydraulic gradient;
[0020] increased wetted soil perimeter;
[0021] increased media area for attached microbial growth;
[0022] prevention or reduction of soil intrusion; and
[0023] increased soil interface area to volume ratios.
[0024] Increased dispersal of organic materials
[0025] While the enhancement of these important performance
measures results in an improved drainage field system and broader
regulatory acceptance, the system remains cost effective both in
terms of material and labor costs. As those of skill in the art
would readily appreciate, these performance measures are highly
desirable in drainage field systems. The drainage industry has
experienced a long felt, yet unmet need for such cost-effective
drainage field systems having these improved performance measures.
These improved performance measures are not, however, at the
expense of other important properties of gravel and disclosed in
the '123 patent (e.g., structural integrity, high resistance to
soil intrusion and maximum exposure to air for treatment of liquids
containing organic materials).
BRIEF DESCRIPTION OF THE DRAWINGS
[0026] Further details of the invention will now be described, by
way of a non-limiting example, with reference to preferred
embodiments of the invention depicted in the attached drawings in
which:
[0027] FIGS. 1A and 1B are cross-sectional views of conventional
gravel-based drain field systems.
[0028] FIGS. 2A and 2B are cross section view of conventional drain
field systems wherein the perforated drainage pipe is located
completely inside an aggregate bundle.
[0029] FIGS. 3A-3E are cross-sectional views of drain field systems
in accordance with the present invention.
[0030] FIGS. 4A-4C illustrate exemplary embodiments of aggregate
bundles which may be may utilized to create volume in the drain
field systems in accordance with the present invention.
DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS
[0031] The systems and related methods disclosed herein employ one
or more contained aggregate bundles to effectively place volume in
the vicinity of a drainage pipe having holes therein to allow
drainage material to exit or enter the pipe, as needed depending on
the application. As shown in FIG. 4A-B, these aggregate bundles can
be made using porous sleeve 50, such as a nylon netting or mesh
that is filled with an aggregation of discrete, water impervious,
crush resistant lightweight elements 51. For example, the
aggregation can be expanded polystyrene, Styrofoam or any number of
other materials, including materials used in crush-resistant
packing. Alternatively, as shown in FIG. 4C, the aggregate bundle
can have multiple aggregate regions. For example, the aggregate
bundle illustrated in FIG. 4C has an annular ring 51 with a first
aggregate material, and a region containing a second aggregate
material 52. Depending on the necessary properties of the drain
field system, one or more aggregate bundles is placed near a
drainage pipe. The aggregate bundles in conjunction with the
drainage pipe, when placed in an excavation or trench, create the
drain field system.
[0032] One example of a drainage field system according to the
present invention is shown in FIG. 3A. In this system, indicated as
system N-2A, three 12-inch diameter bundles 32a, 32b and 32c are
placed side by side on the bottom 12 of a 3-foot wide trench 16.
Two 4-inch diameter pipes 20a and 20b are then placed on top of the
three aggregate bundles 32a, 33b and 32c as shown in FIG. 3A. Soil
or other suitable backfill material 19 is then placed on top of the
aggregate bundles 32a, 32b and 32c and pipes 20a and 20b. Other
exemplary systems consistent with the present invention are shown
in FIGS. 3B-3E and indicated as systems N-1, N-2B, N-2C, and N-3.
While these exemplary embodiments are provided to help explain the
present invention, the present invention is not limited to these
exemplary embodiments.
[0033] Also to help better explain the present invention by way of
comparison, a discussion is provided of the gravel systems shown in
FIGS. 1A-1B, which are indicated as systems G-1 and G-2, and drain
field systems disclosed in the '123 patent wherein a perforated
drainage pipe is disposed within a contained aggregate bundle shown
in FIGS. 2A-2B and indicated as systems H-1 and H-2.
[0034] As discussed above, gravel-based drain field systems are
limited by their structure and materials, thereby hindering the
creation of efficient drain field systems. As demonstrated in more
detail below, the systems disclosed in the '123 patent are limited
in comparison with the drainage systems of the present invention.
For example, the gravel-based systems and the systems disclosed in
the '123 patent have inferior void volume per trench foot, inferior
void volume below the pipe invert, less hydraulic head potential,
less total wetted soil perimeter below the pipe invert, less media
surface area for attached microbial growth, and smaller soil
interface area to volume ratios.
A. Gravel-Based Drain Field Systems
[0035] FIG. 1A illustrates a gravel drainage system (hereinafter,
system G1), including a 4-inch diameter pipe 20 in 24-inch by
12-inch trench 16 filled with gravel 18a and 18b. To calculate
various performance measures, it is necessary to know the relative
dimensions of the drain field system and several calculated
properties, for example, total void volume and trench area. A total
void volume and trench area can be calculated according to
equations 1-9, below: VOID .times. .times. .times. VOLUME .times.
.times. .times. CALCULATION Void .times. .times. .times.
coefficient .times. .times. in .times. .times. gravel .times.
.times. .times. given .times. .times. .times. at .times. .times. 40
.times. % [ 1 ] O . D . .times. of .times. .times. .times. 4 "
.times. .times. pipe = 4.625 .times. .times. in [ 2 ] Void .times.
.times. .times. volume .times. .times. .times. of .times. .times.
.times. pipe .times. .times. .times. per .times. .times. .times.
linear .times. .times. .times. foot = 3.14 * ( 2.3125 .times.
.times. in 12 .times. .times. in .times. / .times. ft ) 2 * 1
.times. .times. ft = 0.117 .times. .times. ft 3 [ 3 ] Void .times.
.times. .times. volume .times. .times. in .times. .times. gravel =
.times. [ ( 24 .times. .times. in 12 .times. .times. in .times. /
.times. ft * 12 .times. .times. in 12 .times. .times. in .times. /
.times. ft ) - ( 3.14 .times. ( 2.3125 .times. .times. in 12
.times. .times. in .times. / .times. ft ) 2 ) ] * .40 * 1 .times.
.times. ft = 0.753 .times. .times. ft 3 [ 4 ] Total .times. .times.
void .times. .times. volume - 0.117 + 0.753 = .870 .times. .times.
ft 3 .times. / .times. ft [ 5 ] Gallons .times. .times. .times. per
.times. .times. ft = .870 7.48 = 6.51 .times. .times. gallons
.times. .times. per .times. .times. linear .times. .times. foot [ 6
] ##EQU1## Projected Trench Area Side (2 sidewalls)=2*12=2.0
ft.sup.2/ft [7] Bottom=24=2.0 ft.sup.2/ft [8] Total Projected
Trench Area=4.0 ft.sup.2/ft [9]
[0036] The void coefficient for gravel is based on the February
2002, USEPA Onsite Wastewater Treatment Systems Manual, Chapter 4,
Section 4.3, which states that "the porous medium maintains the
structure of the excavation, exposes the applied wastewater to more
infiltrative surface, and provides storage space for the wastewater
within its void fractions (interstitial spaces, typically 30 to 40
percent of the volume) during peak flows with gravity systems."
[0037] FIG. 1B illustrates a gravel-based drain field system
(hereinafter, system G2), including a 4-inch diameter pipe 20
disposed in 36-inch by 12-inch trench 16 filled with gravel 18a and
18b. For system G-2, a total void volume and trench area can be
calculated according to equations 10-18, below.
Void Volume Calculation Void Coefficient in Gravel given at 40%
[10] O.D. of 4'' pipe=4.625 in [11] Void .times. .times. .times.
volume .times. .times. .times. of .times. .times. pipe .times.
.times. .times. per .times. .times. .times. linear .times. .times.
ft . = 3.14 * ( 2.3125 .times. .times. in 12 .times. .times. in
.times. / .times. ft ) 2 * 1 .times. .times. ft = 0.117 .times.
.times. ft 3 [ 12 ] Void .times. .times. .times. volume .times.
.times. in .times. .times. gravel = .times. [ ( 36 .times. .times.
in 12 .times. .times. in .times. / .times. ft * 12 .times. .times.
in 12 .times. .times. in .times. / .times. ft ) - ( 3.14 .times. (
2.3125 .times. .times. in 12 .times. .times. in .times. / .times.
ft ) 2 ) ] * .40 * 1 .times. .times. ft = 1.153 .times. .times. ft
3 [ 13 ] ##EQU2## Total void volume=0.117+1.153=1.27 ft.sup.3/ft
[14] Gallons per ft=1.27.times.7.48=9.50 gallons per linear ft [15]
Projected Trench Area Sides=2*12 inches=2.0 ft.sup.2/ft [16]
Bottom=36 inches=3.0 ft.sup.2/ft [17] Total Projected Trench
Area=5.0 ft.sup.2/ft [18]
[0038] As will be demonstrated in TABLES 1-7, below, the
gravel-based drain field systems are inferior to the systems of the
present invention when measured by such performance factors as void
volume per trench foot, void volume below the pipe invert,
hydraulic gradient, wetted soil perimeter below the pipe invert,
media area for attached microbial growth, ability to prevent or
reduce of soil intrusion, and soil interface area to volume
ratios.
B. Conventional Drain Field Systems with Aggregate Bundles
Containing a Perforated Drainage Pipe
[0039] FIG. 2A illustrates a cross-section of a drain field system
disclosed in the '123 patent (hereinafter, system H-1) wherein a
perforated drainage pipe 20 is located entirely within an aggregate
bundle 30b. Two aggregate bundles 30a and 30c are disposed on
either side of aggregate bundle 30b. All three aggregate bundles
30a, 30b and 30c rest on the floor 12 of trench 16. Aggregate
bundles 30c and 30a are in contact with the sidewalls 14 and 10 of
the trench 16, respectively. Aggregate bundle 30b is on contact
with aggregate bundles 30c and 30a on either side. The void volume
and trench area for this system can be calculated according to
equations 19-32, below.
[0040] The void coefficient in the aggregate is based upon testing
of EZflow.TM. beads under ASTM standards C29-91a and C127-88 by Law
Engineering, project No. 50161-8-2142-01-831. The void coefficient
of the EZflow.TM. bead under no load conditions was an average of
57.4%. VOID .times. .times. VOLUME Void .times. .times. .times.
coefficient .times. .times. in .times. .times. .times. aggregate
.times. .times. .times. given .times. .times. .times. at .times.
.times. 57.4 .times. % [ 19 ] O . D . .times. of .times. .times. 4
" .times. .times. pipe = 4.625 .times. .times. in [ 20 ] Void
.times. .times. volume .times. .times. .times. per .times. .times.
.times. linear .times. .times. .times. foot = 3.14 * ( 2.3125
.times. .times. in 12 .times. .times. in .times. / .times. ft ) 2 *
1 .times. .times. ft = 0.117 .times. .times. ft 3 [ 21 ] O . D .
.times. of .times. .times. center .times. .times. .times. cylinder
= 12.5 .times. .times. in [ 22 ] Void .times. .times. .times.
volume .times. .times. in .times. .times. .times. aggregate .times.
.times. .times. of .times. .times. .times. center .times. .times.
.times. cylinder = ( 3.14 * ( 6.25 .times. .times. in 12 .times.
.times. in .times. / .times. ft ) 2 - 3.14 * ( 2.3125 .times.
.times. in 12 .times. .times. in .times. / .times. ft ) 2 ) * .574
= .422 .times. .times. ft 3 [ 23 ] O . D . .times. of .times.
.times. .times. outside .times. .times. cylinders = 12 .times.
.times. in [ 24 ] Void .times. .times. .times. volume .times.
.times. in .times. .times. outside .times. .times. .times.
cylinders = 2 * 3.14 .times. ( 6 .times. .times. in 12 .times.
.times. in .times. / .times. ft ) 2 * .574 = .901 .times. .times.
ft 3 [ 25 ] Void .times. .times. volume .times. .times. .times. at
.times. .times. .times. bottom .times. .times. .times. between
.times. .times. .times. cylinders = .times. [ ( 24 .times. .times.
in 12 .times. .times. in .times. / .times. ft * 6 .times. .times.
in 12 .times. .times. in .times. / .times. ft ) - ( 3.14 .times. (
6 .times. .times. in 12 .times. .times. in .times. / .times. ft ) 2
) ] = 0.215 .times. .times. ft 3 [ 26 ] Void .times. .times.
.times. volume .times. .times. .times. at .times. .times. .times.
outside .times. .times. .times. bottom .times. .times. .times.
corners .times. .times. ( 1 2 .times. .times. of .times. .times.
.times. void .times. .times. volume .times. .times. .times. between
.times. .times. cylinders ) = 0.215 / 2 = 0.108 .times. .times. ft
3 [ 27 ] Total .times. .times. .times. void .times. .times. .times.
volume = 0.117 + 0.422 + 0.901 + 0.215 + 0.108 = 1.76 .times.
.times. 3 .times. .times. ft 3 .times. / .times. ft [ 28 ] Gallons
.times. .times. .times. per .times. .times. .times. foot = 1.763
7.48 = 13.2 .times. .times. gallons .times. .times. per .times.
.times. .times. linear .times. .times. ft [ 29 ] ##EQU3## Projected
Trench Area Sides (2 Sidewalls)=2*12 in=2.0 ft.sup.2/ft [30]
Bottom=36 inches=3.0 ft.sup.2/ft [31] Total Projected Trench
Area=5.0 ft.sup.2/ft [32]
[0041] FIG. 2B illustrates a cross-section of a drain field system
disclosed in the '123 patent (hereinafter, system H-2) wherein a
perforated drainage pipe 20 is located within an aggregate bundle
30d. A second aggregate bundle 30a is disposed next to aggregate
bundle 30d. Both aggregate bundles rest on the bottom surface 12 of
the trench 16 and are in contact with the respective sidewalls 14
and 10 of trench 16. The void volume and trench area for this
system can be calculated according to equations 33-46, below. VOID
.times. .times. .times. VOULME .times. .times. .times. CALCULATION
Void .times. .times. coefficient .times. .times. in .times. .times.
.times. aggregate .times. .times. .times. given .times. .times.
.times. at .times. .times. 57.4 .times. % [ 33 ] O . D . .times. of
.times. .times. 4 " .times. .times. pipe = 4.625 .times. .times.
inches [ 34 ] Void .times. .times. .times. volume .times. .times.
.times. per .times. .times. .times. linear .times. .times. ft . =
3.14 * ( 2.3125 .times. .times. in 12 .times. .times. in .times. /
.times. ft ) 2 * 1 .times. .times. ft = 0.117 .times. .times. ft 2
[ 35 ] O . D . .times. of .times. .times. .times. cylinder .times.
.times. .times. with .times. .times. .times. pipe = 12.5 .times.
.times. in [ 36 ] Void .times. .times. .times. volume .times.
.times. in .times. .times. .times. aggregate .times. .times.
.times. of .times. .times. cylinder = ( 3.14 * ( 6.25 .times.
.times. in 12 .times. .times. in .times. / .times. ft ) 2 - 3.14 *
( 2.3125 .times. .times. in 12 .times. .times. in .times. / .times.
ft ) 2 ) * .574 = 0.422 .times. .times. ft 2 [ 37 ] O . D . .times.
of .times. .times. .times. cylinder .times. .times. .times. without
.times. .times. .times. pipe = 12 .times. .times. in [ 38 ] Void
.times. .times. .times. volume .times. .times. in .times. .times.
aggregate .times. .times. .times. of .times. .times. .times.
cylinder = 3.14 .times. ( 6 .times. .times. in 12 .times. .times.
in .times. / .times. ft ) 2 * .574 = 0.451 .times. .times. ft 3
.times. / .times. ft [ 39 ] Void .times. .times. .times. volume
.times. .times. .times. at .times. .times. .times. bottom .times.
.times. .times. between .times. .times. cylinders = .times. [ ( 12
.times. .times. in 12 .times. .times. in .times. / .times. ft * 6
.times. .times. in 12 .times. .times. in .times. / .times. ft ) - (
3.14 .times. ( 6 .times. .times. in 12 .times. .times. in .times. /
.times. ft ) 2 * 1 2 ) ] = 0.108 .times. .times. ft 2 [ 40 ] Void
.times. .times. .times. volume .times. .times. .times. at .times.
.times. .times. outside .times. .times. .times. bottom .times.
.times. corners .times. .times. ( same .times. .times. .times. as
.times. .times. .times. void .times. .times. .times. volume .times.
.times. .times. between .times. .times. .times. cylinders ) = 0.108
.times. .times. ft 2 [ 41 ] Total .times. .times. .times. void
.times. .times. .times. volume = 0.117 + 0.422 + 0.451 + 0.108 +
0.108 = 1.2 .times. .times. ft 3 .times. / .times. ft [ 42 ]
Gallons .times. .times. .times. per .times. .times. ft = 1.2 7.48 =
9.02 .times. .times. gallons .times. .times. per .times. .times.
linear .times. .times. ft [ 43 ] ##EQU4## Projected Trench Area
Sides (2 sidewalls)=2*12 inches=2.0 ft.sup.2/ft [44] Bottom=24
inches=2.0 ft.sup.2/ft [45] Total Projected Trench Area=4.0
ft.sup.2/ft [46]
C. Exemplary Embodiments of the Present Invention
[0042] FIG. 3A illustrates yet another exemplary embodiment of a
drainage system (hereinafter, RING system N-2A) in accordance with
the present invention. In system N-2A, a first perforated drainage
pipe 20a is disposed between and on top of a first aggregate bundle
32a and a second aggregate bundle 32b. A second drainage pipe 20b
is disposed between and on top of a second aggregate bundle 32b and
a third aggregate bundle 32c. All three aggregate bundles rest on
the floor 12 of trench 16. For this system, a void volume and a
projected trench area can be calculated according to equations
47-58, below.
Void Volume Void coefficient in aggregate given at 57.4% [47] O.D.
of 4'' Pipe--4.625 in [48] Void .times. .times. .times. Volume
.times. .times. .times. per .times. .times. .times. linear .times.
.times. ft . = 2 * 3.14 * ( 2.3125 .times. .times. in 12 .times.
.times. in .times. / .times. ft ) 2 * 1 .times. .times. ft = 0.233
.times. .times. ft 3 [ 49 ] O . D . .times. of .times. .times.
Aggregate .times. .times. .times. Bundles = 12 .times. .times. in [
50 ] Void .times. .times. .times. Volume .times. .times. in .times.
.times. Aggregate .times. .times. .times. Bundles = 3 * 3.14 * (
6.00 .times. .times. in 12 .times. .times. in .times. / .times. ft
) 2 * 0.574 = 1.352 .times. .times. ft 3 [ 51 ] ##EQU5## Void
Volume Between Aggregate Bundles & Pipes=0.035 ft.sup.3
(Determined by CAD Software). [52] Void Volume at Bottom=0.323
ft.sup.3 [53] Total Void Volume=0.233+1.352+0.035+0.323=1.943
ft.sup.3/ft [54] Gallons per Trench Foot=1.943.times.7.48=14.53
[55] Projected Trench Area Sides (2 Sidewalls)=2*12 in=2.0
ft.sup.2/ft [56] Bottom=36 in =3.0 ft.sup.2/ft [57] Total Projected
Trench Area=5.0 ft.sup.2/ft [58]
[0043] FIG. 3B illustrates still another exemplary embodiment of a
drainage system (hereinafter, system N-1) consistent with the
present invention. In system N-1, four 4-inch diameter drainage
pipes 20c, 20d, 20e and 20f are stacked between two aggregate
bundles 32d and 32e. Drainage pipes 20e and 20f are located on the
trench floor 12 and drainage pipes 20c and 20d are stacked on top
of drainage pipes 20f and 20e, respectively. In system N-1, a void
volume and a projected trench area can be calculated according to
equations 59-71, below.
Void Volume Void coefficient in aggregate given at 57.4% [59] O.D.
of 4'' Pipe=4.625 inches [60] Void .times. .times. .times. Volume
.times. .times. .times. per .times. .times. .times. linear .times.
.times. ft . = 4 * 3.14 * ( 2.3125 .times. .times. in 12 .times.
.times. in .times. / .times. ft ) 2 * 1 .times. .times. ft = 0.467
.times. .times. ft 3 [ 61 ] O . D . .times. of .times. .times.
.times. Aggregate .times. .times. .times. Bundles = 13 .times.
.times. in [ 62 ] Void .times. .times. Volume .times. .times. in
.times. .times. Aggregate .times. .times. .times. Bundles = 2 *
3.14 * ( 6.50 .times. .times. in 12 .times. .times. in .times. /
.times. ft ) 2 * 0.574 = 1.058 .times. .times. ft 3 [ 63 ] ##EQU6##
Void Volume Between Aggregate Bundles & Pipe=0.170 ft.sup.3 (As
Determined by CAD Software). [64] Void Volume at Bottom
Corner=0.063 ft.sup.3 [65] Void Volume Between 4-inch
Pipes=6*0.008=0.048 ft.sup.3 [66] Total Void
Volume=0.467+1.058+0.170+0.063+0.048=1.806 ft.sup.3/ft [67] Gallons
per Trench Foot=1.806.times.7.48=13.51 [68] Projected Trench Area
Sides (2 sidewalls)=2*13 in=2.167 ft.sup.2/ft [69] Bottom=36 in=3.0
ft.sup.2/ft [70] Total Projected Trench Area=5.17 ft.sup.2/ft
[71]
[0044] FIG. 3C illustrates one exemplary embodiment of a drainage
system (hereinafter, system N-2B) in accordance with the present
invention. In system N-2B, a 4-inch diameter perforated drainage
pipe 20a is disposed between and on top of two aggregate bundles
32a and 32b. A third aggregate bundle 32c is disposed to one side
of aggregate bundle 32b. All three aggregate bundles 32a, 32b, and
32c rest on the floor 12 of the trench 16 For this system, a void
volume and a projected trench area can be calculated according to
equations 72-83, below.
Void Volume Void Coefficient in Aggregate given at 57.4% [72] O.D.
of 4'' Pipe=4.625 inches [73] Void .times. .times. .times. Volume
.times. .times. .times. per .times. .times. .times. linear .times.
.times. ft . = 3.14 * ( 2.3125 .times. .times. in 12 .times.
.times. in .times. / .times. ft ) 2 * 1 .times. .times. ft = 0.117
.times. .times. ft 3 [ 74 ] O . D . .times. of .times. .times.
.times. Aggregate .times. .times. .times. Bundles = 12 .times.
.times. in [ 75 ] Void .times. .times. Volume .times. .times. in
.times. .times. Aggregate .times. .times. .times. Bundles = 3 *
3.14 * ( 6.00 .times. .times. in 12 .times. .times. in .times. /
.times. ft ) 2 * 0.574 = 1.352 .times. .times. ft 3 [ 76 ] ##EQU7##
Void Volume Between Aggregate Bundles & Pipes=0.018 ft.sup.3
(As Determined by CAD Software). [77] Void Volume at Bottom=0.323
ft.sup.2 [78] Total Void Volume=0.117+1.352+0.018+0.323=1.810
ft.sup.3/ft [79] Gallons per Trench Foot=1.810.times.7.48=13.54
[80] Projected Trench Area Sides (2 sidewalls)=2*12 in=2.0
ft.sup.2/ft [81] Bottom=36 inches=3.0 ft.sup.2/ft [82] Total
Projected Trench Area=5.0 ft.sup.2/ft [83]
[0045] FIG. 3D illustrates another exemplary embodiment of a drain
filed system (hereinafter, system N-2-C) in accordance with the
present invention. In system N-2C, a 4-inch diameter pipe 20g is
disposed between and on top of two aggregate bundles 32g and 32f.
For this system, a void volume and a projected trench area can be
calculated according to equations 84-95, below.
Void Volume Void Coefficient in Aggregate given at 57.4% [84] O.D.
of 4'' pipe=4.625 in [85] Void .times. .times. .times. Volume
.times. .times. .times. per .times. .times. .times. linear .times.
.times. ft . = 3.14 * ( 2.3125 .times. .times. in 12 .times.
.times. in .times. / .times. ft ) 2 * 1 .times. .times. ft = 0.117
.times. .times. ft 3 [ 86 ] O . D . .times. of .times. .times.
.times. Aggregate .times. .times. .times. Bundles = 12 .times.
.times. in [ 87 ] Void .times. .times. Volume .times. .times. in
.times. .times. Aggregate .times. .times. .times. Bundles = 2 *
3.14 * ( 6.00 .times. .times. in 12 .times. .times. in .times. /
.times. ft ) 2 * 0.574 = 0.902 .times. .times. ft 3 [ 88 ] ##EQU8##
Void Volume Between Aggregate Bundles & Pipes=0.018 ft.sup.3.
(As Determined by CAD Software). [89] Void Volume at Bottom=0.216
ft.sup.3. [90] Total Void Volume=0.117+0.902+0.018+0.216=1.253
ft.sup.3/ft [91] Gallons per Trench Foot=1.253.times.7.48=9.37 [92]
Projected Trench Area Sides=2 Sidewalls=2*12 inches=2.0 ft.sup.2/ft
[93] Bottom=24 inches=2.0 ft.sup.2/ft [94] Total Projected Trench
Area=4.0 ft.sup.2/ft [95]
[0046] FIG. 3E illustrates one exemplary embodiment of a drain
field system (hereinafter, system N-3) in accordance with the
present invention. In system N-3, a 12-inch diameter pipe 22 is
disposed between two aggregate bundles 32h and 32i. In this system,
the perforated drainage pipe 22 has substantially the same outside
diameter as the aggregate bundles 32h and 32i. For this system, a
void volume and a projected trench area can be calculated according
to equations 96-104, below.
Void Volume Calculation Void Coefficient in Aggregate given at
57.4% [96] O.D. of 10'' pipe=12'' [96] Void .times. .times. volume
.times. .times. .times. of .times. .times. .times. pipe .times.
.times. .times. per .times. .times. .times. linear .times. .times.
ft = 3.14 * ( 5.50 .times. .times. in 12 .times. .times. in .times.
/ .times. ft ) 2 * 1 .times. .times. ft = 0.660 .times. .times. ft
3 [ 97 ] Void .times. .times. .times. volume .times. .times. in
.times. .times. aggregate .times. .times. bundles = 2 * 3.14 * (
6.00 .times. .times. in 12 .times. .times. in .times. / .times. ft
) 2 * 0.574 = 0.902 .times. .times. ft 3 [ 98 ] Void .times.
.times. volume .times. .times. .times. at .times. .times. .times.
between .times. .times. .times. bundles = 6 * [ ( 6.0 .times.
.times. in 12 .times. .times. in .times. / .times. ft * 6.0 .times.
.times. in 12 .times. .times. in .times. / .times. ft ) - ( 3.14
.times. ( 6.0 .times. .times. in 12 .times. .times. in .times. /
.times. ft ) 2 * 1 4 ) ] = 0.322 .times. .times. ft 3 [ 99 ]
##EQU9## Total void volume=0.660+0.902+0.321=1.883 ft.sup.3/ft
[100] Gallons per ft=1.883.times.7.48=14.08 gallons per linear ft
[101] Projected Trench Area Sides (2 sidewalls)=2*12 in=2.0
ft.sup.2/ft [102] Bottom=36 inches=3.0 ft.sup.2/ft [103] Total
Projected Trench Area=5.0 ft.sup.2/ft [104]
[0047] As can be seen from the above equations and as will be
described in greater detail below by reference to the exemplary
embodiments of the present invention (in comparison to
comparably-sized gravel drain field systems), key performance
measures for drain field systems in accordance with the present
invention are greatly improved.
1. Increased Void Volume Per Trench Foot
[0048] Void volume per trench foot is one measure of drain field
performance relied upon by those of skill in the art to determine
the efficiency of a drain field system. Gravel-based drainage
systems, such as systems G-1 or G-2, have void volume per trench
foot equal to approximately 6 gallons per trench foot in a two foot
wide trench and 9 gallons per foot in a 3 foot wide trench. Storage
volume (i.e., void volume) is needed to accommodate peak flows into
the drainfield and to temporarily store the liquid that accumulates
during the peak flow, allowing time for the liquid to infiltrate
into the soil. Storage volume per trench foot requirements are
sometimes imposed by some state and municipal onsite rules and
regulations.
[0049] This low void volume per trench foot values of the
gravel-based drain field systems are a result of the lower porosity
of the aggregate. While systems as disclosed in the '123 patent,
such as systems H-1 and H-2, result in an increased void volume per
trench foot ratio, this measure still is significantly less than
that of the exemplary embodiments of the present invention, namely
systems N-1, N-2B, N-2C, and N-3.
[0050] Gravel aggregate void volumes can typically be in the range
of 30-40% with a commonly accepted average of 35%. A table of void
volume per trench foot for the above described exemplary
embodiments of the present invention and comparable gravel drain
field systems is shown below: TABLE-US-00001 TABLE 1 SYSTEM VOLUME
(gal.)/TRENCH FOOT 3-foot Trench Width N-2A 14.53 N-3 14.08 N-2B
13.54 N-1 13.51 H-1 13.20 G-2 9.50 2-foot Trench Width N-2C 9.37
H-2 9.02 G-1 6.51
[0051] As shown in TABLE 1, the exemplary embodiments of the
present invention result in a greater void volume per trench foot
than conventional systems. For example, system N-2A results in a
52.9% increase over a comparable gravel-based drain field system,
system G-2. In comparison to system H-1, system N-1 results in a
2.3% increase over system H-1 whereas system N-2A results in a
10.0% increase in comparison to the same system. Void volume per
trench foot ratios obtained in systems N-1, N-2A-C and N-3 could
not be achieved in a conventional system wherein the drainage pipes
are completely contained within an aggregate bundle as in systems
H-1 and H-2, for example. In a system having dimensionally similar
measurements to gravel trenches, preferred embodiments consistent
with the present invention provide a percent increase in volume per
trench foot of at least 10%. A 10% increase represents a
substantial improvement over volumes per trench foot achieved using
gravel-based systems and systems as disclosed in the '123
patent.
2. Increased Volume Below the Pipe Invert
[0052] When used in septic applications, some state environmental
regulations determine system size based on volume below the pipe
invert. In accordance with many state and municipal onsite rules
and regulations, the more storage volume below the invert allows
for a shorter installed trench length. This shorter trench length
allows for system installation on smaller lot sizes, which in turn
saves the homeowner and the installer time and money. Placing the
pipe outside of the aggregate bundles as in systems N-2A, N-2B, and
N-2C dramatically increases volume below the pipe invert in
comparison to comparable conventional systems. For example, for a
3-foot wide trench, system N-2A results in an increase of 49.4%
increase in volume below the pipe invert over system H-1 and a
147.66% increase over system G-2. In a system having dimensionally
similar measurements to gravel trenches, preferred embodiments
consistent with the present invention provide a percent increase in
volume below the pipe invert of at least 25%. A 25% increase
represents a substantial improvement over volumes below the pipe
invert achieved using gravel-based systems and systems as disclosed
in the '123 patent. TABLE-US-00002 TABLE 2 VOLUME (Gal) BELOW THE
PIPE SYSTEM INVERT 3-foot Trench Width N-2A 11.12 N-2B 10.98 H-1
7.35 G-2 4.49 2-foot Trench Width N-2C 7.49 H-2 4.87 G-1 2.99
3. Increased Pressure Head With Increased Volume
[0053] Placing drainage pipes in the vicinity of aggregate bundles
as disclosed herein, as opposed to in a gravel-filled trench or
inside aggregate bundles results in increasing volume and pressure
head, the pressure head being defined as the water level above the
soil and below the invert of the drainage pipe. In a septic
drainfield, the presence of an aggregate displaces a volume of
liquid to a greater height, while utilizing more surface area, than
non-aggregate systems with the same quantity of liquid introduced
into the drainfield. The height of the displaced liquid creates a
pressure head, which, because of the pressure, forces the liquid
into the surrounding soil at a greater rate.
[0054] TABLE 3, below, illustrates the increase in pressure head
for systems in accordance with the present invention in comparison
to comparable gravel-based drain field systems and systems
disclosed in the '123 patent. TABLE-US-00003 TABLE 3 SYSTEM
PRESSURE HEAD (in.) 3-foot Trench Width N-2A 8.0 N-2B 8.0 H-1 6.0
G-2 6.0 2-foot Trench Width N-2C 8.0 H-2 6.0 G-1 6.0
[0055] In the examples given above, the pressure head below the
invert for a 3-foot wide system increases for systems N-2A and N-2B
33% over the pressure head for either system H-1 or G-2. Similar
results are obtained for a 2-foot wide trench.
4. Increased Wetted Soil Perimeter Below the Pipe Invert
[0056] Another key metric for evaluating the performance of a drain
field system is the wetted soil perimeter below the pipe invert. In
drainfields systems, an increased wetted soil perimeter below the
pipe invert is desirable as it allows for a larger area for the
dispersal of organics, and less trench clogging material per unit
area. This increase in the area available for organic growth
increases the life of the drainfield system substantially by
spreading the organics and the clogging material over a larger
area, and lessens the organic loading rate per unit area.
Gravel-based drain field systems and systems as disclosed in the
'123 patent have a reduced wetted soil perimeter in comparison to
comparable systems embodying the present invention. By locating
drainage pipe(s) on the top of aggregate bundles, the wetted soil
perimeter below the pipe invert is increased, resulting in enhanced
drainage characteristics.
[0057] For example, as shown in TABLE 4, for a 3-foot wide trench,
systems H-1 and G-2 have a wetted soil perimeter below the pipe
invert of 4 feet, whereas systems N-2A and N-2B each have a wetted
soil perimeter below the pipe invert of 4.33 feet, an 8.25%
increase over the conventional systems. For a 2-foot wide trench,
system N-2C results in an 11.0% increase over the wetted soil
perimeter below the pipe invert for comparable conventional systems
H-2 and G-1. This substantial increase in wetted soil perimeter
below the pipe invert greatly enhances drainage characteristics of
drain field systems. TABLE-US-00004 TABLE 4 WETTED SOIL PERIMETER
BELOW SYSTEM THE PIPE INVERT (ft) 3-foot Trench Width N-2A 4.33
N-2B 4.33 H-1 4.00 G-2 4.00 2-foot Trench Width N-2C 3.33 H-2 3.00
G-1 3.00
5. Increased Media Surface Area for Attached Microbial Growth
[0058] Placement of liquid distribution pipes on the top of
contained aggregate bundles allows for the use of the media as an
attachment site for bacteria (which treat liquids containing
organic matter) to grow. As shown below in TABLE 5, for a 3-foot
wide and a 2-foot wide trench, the increase in media surface area
below the pipe invert per trench foot is increase by 20% and 25%
respectively. This substantial increase significantly improves that
ability of bacteria to grow, thereby having a parallel impact on
the ability of those bacteria to treat liquids containing organic
matter. TABLE-US-00005 TABLE 5 MEDIA SURFACE AREA (ft.sup.2) BELOW
THE PIPE INVERT PER TRENCH SYSTEM FOOT 3-foot Trench Width N-2A 60
N-2B 60 H-1 50 2-foot Trench Width N-2C 40 H-2 32
6. Prevention or Reduction of Soil Intrusion into High-Volume
Systems
[0059] Drainage products such as pipes, multiple pipes or chamber
systems require protection from soil intrusion into the system's
open space. This protection is generally provided in one of two
ways: a pipe system has a fabric or geo-textile wrap used to cover
system openings, and chamber systems employ a louver with an angle
of repose and/or fabric. Placement of aggregate bundles alongside
pipes eliminates the need for a geo-textile wrap, thereby reducing
material and labor costs. Placement of aggregate bundles alongside
a chamber system side wall also greatly improves the chamber
system's resistance to soil intrusion.
7. Improved Oxygen Diffusivity for High-Volume Systems
[0060] High volume systems such as pipe system or chamber system
provide relatively little open exposure of liquid to the soil. This
is especially true for sidewalls. Open exposure is important in
biologically-active systems, e.g., septic drainfields, where oxygen
is used to treat organic matter, and is related to soil content
area. Use of systems embodying the present invention in conjunction
with a pipe system allows for an increase in volume and an increase
in soil exposure at the sidewall and surface interface areas.
TABLE-US-00006 TABLE 6 VOLUME BELOW SYSTEM INVERT (gal/ft) SOIL
EXPOSURE (ft) G-1 2.99 3.00 H-2 4.87 3.00 N-2C 7.49 3.33 G-2 4.49
4.00 H-1 7.35 4.00 N-2A 11.12 4.33 N-2B 10.98 4.33
8. Volume Placement
[0061] The use of contained aggregate bundles in a drain field
system as disclosed herein enables volume to be easily and
efficiently added at the desired location within the drain field.
In drain field systems, volume per se does not necessarily enhance
the performance of the system--the volume must be appropriately
located. For example, in conventional system H-1, to add volume
under the invert of pipe 20, a larger aggregate bundle can be used
or an additional aggregate bundle can be used. A larger aggregate
bundler results in wasted material as the aggregate above the pipe
not efficiently used and is, therefore, wasted. An additional
aggregate bundle results in additional and unneeded material and
labor costs. However, as illustrated in FIGS. 3B-D, exemplary
embodiments of the present invention allow for efficient
utilization of volume by allowing for volume placement where it is
most effective--under the pipe invert--without creating excessive
wasted volume above the pipe invert and without the use of multiple
contained aggregate bundles.
9. Increased Soil Interface to Volume Ratio for High-Volume
Systems
[0062] Gravel-based drain field systems and systems as disclosed in
the '123 patent typically have a higher soil interface area per
unit volume ratio than non aggregate type drain field products such
as a pipe, multiple pipe or chamber systems. This higher soil
interface area to volume ratio is due to the lower porosity of the
aggregate. Gravel volumes can be typically in the range of 25 to
50% with a commonly accepted average of 35%. A table of soil
interface area to volume ratios for various drainage systems is
given below. TABLE-US-00007 TABLE 7 SOIL INTERFACE AREA TO SYSTEM
WIDTH (ft) VOLUME RATIO N-2A 3 2.907 N-3 3 2.817 N-2B 3 2.710 H-1 3
2.640 N-2C 2 2.343 H-2 2 2.255 G-2 3 1.901 G-1 2 1.628
[0063] As evident from TABLE 7. the drain field systems in
accordance with the present invention have significantly better
soil interface area to volume ratios over the conventional systems.
Higher soil interface area to volume ratios, such as those provided
by the systems of the present invention, are desirable as they
allow a drainfield system to be sized and installed with a higher
organic loading rate per trench foot, and thus a trench length
reduction compared to conventional gravel-based systems. This is
because systems consistent with the invention disclosed herein
utilize the higher soil interface area and the increased pressure
head to move the liquid out of the drainfield and into the soil at
a faster rate. The use of a higher soil interface area increases
the lifespan of the system per trench foot installed. The system
also contains enough storage capacity to handle peak flows when
sized at a higher organic loading rate.
[0064] The above description of exemplary embodiments has been
given by way of example. From the disclosure given, those skilled
in the art will not only understand the present invention and its
attendant advantages, but will also find apparent various changes
and modifications to the structures and methods disclosed. It is
sought, therefore, to cover all such changes and modifications as
fall within the spirit and scope of the invention, as defined by
the appended claims, and equivalents thereof.
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