HomeMy WebLinkAboutEngineer's OWTS Design-Revised 12.02.24 2789 Riverside Parkway
Grand Junction, Colorado 81501
Phone: 970-255-8005
Info@huddlestonberry.com
December 2, 2024
Project#02388-0002
Mr. Shane Wade
PO Box 425
Silt, Colorado 81652
Subject: OWTS Design
1650 County Road 237 Tract 44A
Silt, Colorado
Dear Mr. Wade,
At your request, Huddleston-Berry Engineering & Testing, LLC completed design of an Onsite
Wastewater Treatment System (OWTS) for a single-family residence at 1650 County Road 237
Tract 44A in Silt, Colorado. The site location is shown on Figure 1 – Site Location Map. A site
plan is included as Figure 2.
Site Description
At the time of the investigation, the northwest and northeast portions of the site were occupied
by existing residences. The remainder of the site was open and gradually sloping down towards
the south. Site topography is shown on Figure 2. Vegetation in the vicinity of the investigated
area consisted primarily of weeds and grasses. The site was bordered to the north and east by
residential/agricultural properties, to the south by 250 Road, and to the west by Harvey Gap
Road.
Subsurface Investigation
As indicated on the logs, the subsurface conditions at the site were fairly consistent. Using
visual-tactile classification methods, the soil profile consisted of 0.5 feet of topsoil above tan to
brown, moist, medium dense silt loam soils with a moderate granular structure that extended to
the bottom of the excavation in TP-1 and to a depth of 5.5 feet in TP-2, (Soil Type 2). The silt
loam soils in TP-2 were underlain by brown, moist, medium stiff, structureless sandy clay loam
soils (Restrictive Layer).
Groundwater was not encountered in the subsurface at the time of the investigation. However,
saturated soils were observed at a depth of 4.5 feet in the test pits. In general, based upon the
results of the subsurface investigation, HBET believes that the seasonal high groundwater
elevation is deeper than 4.5 feet below the existing grade at this site.
The locations of the test pits are shown on Figure 2. Copies of the test pit logs are included in
Appendix A.
1650 CR237 Tract 44A
#02388-0002
12/2/24
V:\2008 ALL PROJECTS\02388 - Shane Wade\02388-0002 1650 County Road 237 Tract 44A\200 - Geo\02388-0002 OWTS120224.doc 2
Onsite Wastewater Treatment System
The seasonal high groundwater elevation is an important factor in determining the suitability of
the site for Onsite Wastewater Treatment Systems. For OWTS suitability, the seasonal high
groundwater elevation should be at least four feet below the bottom of the proposed Soil
Treatment Area (STA). As discussed previously, HBET believes the seasonal high groundwater
elevation is deeper than 4.5 feet below the existing grade at this site. As a result, the bottom of
the STA can be no deeper than 0.5 feet below existing grade at this site. Therefore, a mounded
system will be required at this site. This should be considered when establishing the elevation of
the house to make certain that adequate fall to the STA can be achieved.
Seepage Bed Design
The design of the absorption system generally follows the requirements of the Garfield County
Department of Public Works as outlined in the Garfield County On-Site Wastewater Treatment
System Regulations, effective July 2018. The proposed construction at the site is anticipated to
include a four-bedroom home. However, the proposed construction contains an office with a
closet. Therefore, the design will consider five bedrooms.
Based upon the visual tactile classification of the soils, a Long-Term Acceptance Rate (LTAR)
of 0.6 will be utilized for the absorption field design. Infiltrator Systems Quick4 Standard
Chambers are proposed. The daily flow of the sewage disposal system is calculated below and a
plan and profile of the absorption system are shown on Figure 3.
Average Daily Flow = (8 persons)(75 GPD/person)
= 600 GPD
Soil Treatment Area = (600 GPD / 0.6) = 1,000 Square Feet
Adjusted Soil Treatment Area = (1,000 SF)(1.2)(0.7) = 840 Square Feet
# of Quick4 Chambers = (840 / 12) = 70 Chambers; Use 72 Chambers
System Installation
The installation of the septic tank, plumbing lines, Infiltrators, etc. should be completed in
accordance with the Garfield County On-Site Wastewater Treatment System Regulations and
Infiltrator Systems, Inc. specifications. In addition, the following construction procedures are
recommended:
The septic tank and distribution box should be placed level over native soils that have
been scarified to a depth of 8 to 12 inches, moisture conditioned, and recompacted to
a minimum of 95% of the standard Proctor maximum dry density, within ±2% of
optimum moisture content. However, up to 3-inches of washed rock or pipe bedding
passing the 1-inch sieve may be used as a leveling course under the septic tank and/or
distribution box.
The bottoms of trenches and backfill around the septic tank and distribution box
which will support sewer or effluent lines should be compacted to at least 90 percent
of the standard Proctor maximum dry density, within ±2% of optimum moisture
content. Pipe bedding should have a maximum particle size of 1-inch.
Vehicular or heavy equipment traffic and placement of structures should not encroach
within 10 feet of the septic tank or distribution box.
1650 CR237 Tract 44A
#02388-0002
12/2/24
V:\2008 ALL PROJECTS\02388 - Shane Wade\02388-0002 1650 County Road 237 Tract 44A\200 - Geo\02388-0002 OWTS120224.doc 3
Inspection Schedule
Huddleston-Berry Engineering & Testing LLC should be retained to monitor the construction of
the OWTS. The following schedule of observation and/or testing should be followed:
Observe the absorption bed excavation prior to placement of Infiltrator chambers.
Observe placement of the septic tank, distribution box, and all connecting sewer and
effluent lines prior to backfill. Verify proper fall between inverts.
Observe and verify installation of the absorption bed prior to placement of cover and
backfill.
In conformance with Garfield County regulations, HBET will be required to provide the Garfield
County Health Department with documentation certifying that the OWTS was placed in
conformance to the plan and profile and Garfield County regulations.
General Notes
The OWTS design was based upon the results of the subsurface investigation and on our local
experience. The design is valid only for the proposed construction.
We are pleased to be of service to your project. Please contact us if you have any questions or
comments regarding the contents of this report.
Respectfully Submitted:
Huddleston-Berry Engineering and Testing, LLC
Wayne D. Anderson, P.E.
Project Engineer
FIGURES
2789 Riverside Parkway
Grand Junction, CO 81501
Project No.: 02388-0002
Date: 12/2/24
By: WDA
1650 CR 237 TRACT 44A
PARCEL#212725400042
FIGURE 2 - SITE PLANTEST PIT
C.I. = 2 FT
SCALE: 1" = 50'
**NOTE:TANK AND BED LOCATIONS APPROXIMATE AND MAY SHIFT SOME DURING
CONSTRUCTION BASED UPON SITE TOPOGRAPHY, OWNER PREFERENCE, AND/OR OTHER
FACTORS AS LONG AS APPLICABLE SETBACKS ARE MET. ACTUAL LOCATION OF TANK AND
BED WILL BE INDICATED ON AS-BUILT DRAWINGS.**
TP-1
58
1
6
58
1
8
58
1
4
58
1
2
58
2
0
58
1
8
58
1
6
58
1
8
TP-2
~21'
~29'
91.5'
~65'
28'
(20' MIN)
11'
(10' MIN)
11'
(10' MIN)
5' MIN
72'
12'
28'
(25' MIN)
NEW RESIDENCE
SEPTIC TANK
WITH MINIMUM
1,500 GALLON
CAPACITY
REPAIR AREA
STA
WATER LINE
EXISTING DRIVEWAY
2789 Riverside Parkway
Grand Junction, CO 81501
Project No.: 02388-0002
Date: 12/2/24
By: WDA
MINIMUM SETBACKS
(UNITS = FT)
**OTHER SETBACKS NOT LISTED HERE SHOULD BE IN ACCORDANCE WITH GARFIELD COUNTY OWTS REGULATIONS
**USE SWEEP 90'S OR
TWO 45'S AT 90
DEGREE BENDS**
DETAIL AREA
SCALE: 1" = 30'
1650 CR 237 TRACT 44A
PARCEL#212725400042
FIGURE 3 - SEPTIC SYSTEM
DETAILS
INSPECTION PORTS
72'
5' MIN
20'
MIN
SEPTIC TANK WITH
MINIMUM 1,500
GALLON CAPACITY
WATER LINE
12'
SYSTEM MOUND ENVELOPE
3H:1V SLOPES FROM SPECIFIED
2-FOOT SHOULDER
TOP OF SLOPE
BOTTOM OF SLOPE
GENERALIZED SYSTEM PROFILE
GENERALIZED BED PROFILE
COVER SOIL; NATIVE SOILS OR OTHER SUITABLE
TOPSOIL. GRADE TO CARRY SURFACE WATER
AWAY FROM BED.
NONWOVEN, NEEDLE PUNCHED, GEOTEXTILE
FABRIC IMMEDIATELY ABOVE CHAMBERS
INFILTRATOR SYSTEMS QUICK4
STANDARD CHAMBERS
**BOTTOMS OF CHAMBERS 0.5 FEET
BELOW EXISTING GRADE MAX -
VERIFY TOPSOIL REMOVED AND
BOTTOMS OF CHAMBERS PLACED
ON NATIVE SOILS
FILTER BED DIMENSIONS = ONE 12'X72' BED
4 ROWS OF 18 QUICK4 STANDARD INFILTRATORS OR
ENGINEER APPROVED EQUAL
2'
MIN
MAX. 3H:1V SLOPE
NATIVE NON-FREE
DRAINING MATERIAL
2'
MIN
MAX. 3H:1V SLOPE
NEW
RESIDENCE
4-INCH DIAMETER SEWER AND
EFFLUENT PIPE MEETING ASTM D1785,
SCHEDULE 40 OR SDR 35
DISTRIBUTION BOX THAT
ENSURES EVEN DISTRIBUTION
OF EFFLUENT
4 ROWS OF 18 QUICK4
STANDARD INFILTRATORS OR
ENGINEER APPROVED EQUAL
EXISTING GRADE
0.5'
MAX
APPENDIX A
Typed Test Pit Logs
Sandy Clay with Organics (TOPSOIL)
Silt Loam, tan to brown, moist, medium dense, moderate granular
structure (Soil Type 2)
**Saturated Soils at 4.5 Feet
Bottom of test pit at 5.5 feet.
NOTES
GROUND ELEVATION
LOGGED BY TC
EXCAVATION METHOD Trackh/Backhoe AT TIME OF EXCAVATION Dry
AT END OF EXCAVATION Dry
AFTER EXCAVATION ---
TEST PIT SIZE
EXCAVATION CONTRACTOR Client GROUND WATER LEVELS:
CHECKED BY MAB
DATE STARTED 9/26/24 COMPLETED 9/26/24
DE
P
T
H
(f
t
)
0.0
2.5
5.0
GR
A
P
H
I
C
LO
G
ATTERBERG
LIMITS
MATERIAL DESCRIPTION
SA
M
P
L
E
T
Y
P
E
NU
M
B
E
R
FI
N
E
S
C
O
N
T
E
N
T
(%
)
RE
C
O
V
E
R
Y
%
(R
Q
D
)
BL
O
W
CO
U
N
T
S
(N
V
A
L
U
E
)
PO
C
K
E
T
P
E
N
.
(t
s
f
)
DR
Y
U
N
I
T
W
T
.
(p
c
f
)
MO
I
S
T
U
R
E
CO
N
T
E
N
T
(
%
)
LI
Q
U
I
D
LI
M
I
T
PL
A
S
T
I
C
LI
M
I
T
PL
A
S
T
I
C
I
T
Y
IN
D
E
X
PL
A
S
T
I
C
I
T
Y
IN
D
E
X
PAGE 1 OF 1
TEST PIT NUMBER TP-1
CLIENT Shane Wade
PROJECT NUMBER 02388-0002
PROJECT NAME 1650 County Road 237 Tract 44A
PROJECT LOCATION Silt, CO
GE
O
T
E
C
H
B
H
C
O
L
U
M
N
S
0
2
3
8
8
-
0
0
0
2
1
6
5
0
C
O
U
T
R
Y
R
O
A
D
2
3
7
T
R
A
C
T
4
4
A
.
G
P
J
G
I
N
T
U
S
L
A
B
.
G
D
T
1
1
/
3
0
/
2
4
Huddleston-Berry Engineering & Testing, LLC
2789 Riverside Parkway
Grand Junction, CO 81501
970-255-8005
Sandy Clay with Organics (TOPSOIL)
Silt Loam, tan to brown, moist, medium dense, moderate granular
structure (Soil Type 2)
**Saturated Soils at 4.5 Feet
Sandy Clay Loam, brown, moist, medium stiff, structureless
(**Restrictive Layer**)
Bottom of test pit at 5.5 feet.
NOTES
GROUND ELEVATION
LOGGED BY TC
EXCAVATION METHOD Trackh/Backhoe AT TIME OF EXCAVATION Dry
AT END OF EXCAVATION Dry
AFTER EXCAVATION ---
TEST PIT SIZE
EXCAVATION CONTRACTOR Client GROUND WATER LEVELS:
CHECKED BY MAB
DATE STARTED 9/26/24 COMPLETED 9/26/24
DE
P
T
H
(f
t
)
0.0
2.5
5.0
GR
A
P
H
I
C
LO
G
ATTERBERG
LIMITS
MATERIAL DESCRIPTION
SA
M
P
L
E
T
Y
P
E
NU
M
B
E
R
FI
N
E
S
C
O
N
T
E
N
T
(%
)
RE
C
O
V
E
R
Y
%
(R
Q
D
)
BL
O
W
CO
U
N
T
S
(N
V
A
L
U
E
)
PO
C
K
E
T
P
E
N
.
(t
s
f
)
DR
Y
U
N
I
T
W
T
.
(p
c
f
)
MO
I
S
T
U
R
E
CO
N
T
E
N
T
(
%
)
LI
Q
U
I
D
LI
M
I
T
PL
A
S
T
I
C
LI
M
I
T
PL
A
S
T
I
C
I
T
Y
IN
D
E
X
PL
A
S
T
I
C
I
T
Y
IN
D
E
X
PAGE 1 OF 1
TEST PIT NUMBER TP-2
CLIENT Shane Wade
PROJECT NUMBER 02388-0002
PROJECT NAME 1650 County Road 237 Tract 44A
PROJECT LOCATION Silt, CO
GE
O
T
E
C
H
B
H
C
O
L
U
M
N
S
0
2
3
8
8
-
0
0
0
2
1
6
5
0
C
O
U
T
R
Y
R
O
A
D
2
3
7
T
R
A
C
T
4
4
A
.
G
P
J
G
I
N
T
U
S
L
A
B
.
G
D
T
1
1
/
3
0
/
2
4
Huddleston-Berry Engineering & Testing, LLC
2789 Riverside Parkway
Grand Junction, CO 81501
970-255-8005