HomeMy WebLinkAboutEngineer's OWTS Design Plan129 CAINS LANE
CARBONDALE, CO A1623
970.309.5259
CARLA. OSTBERG@GMAIL.COM
tittl"t'I(: ( :(-) N'srt : t-'Ir I N(;
December 20,2023 Project No. C1851
Koby Kempel
kobykempel@yahoo.com
Subsurface lnvestigation and Onsite Wastewater Treatment System Design
5-Bedroom Residence + Future 1-Bedroom ADU
Lot 17, Ranch at Coulter Creek
Garfield County, Colorado
Koby,
CBO lnc. performed a subsurface investigation and completed an onsite wastewater treatment system
(OWTS) design for the subject residence. The 7.998-acre property is located outside of Carbondale, in
an area where OWTSs are necessary.
Legal Description: Section: 7 Township: 7 Range: 87 Subdivision: RANCH AT COULTER CREEK PUD
Lot: 17 AS PER FIRST AMENDED FINAL PLAT RECEPTION NUMBER 889891 7.998 ACRES
Parcel lD: 2391-072-01-017
SITE CONDITIONS
The property is currently undeveloped. A 5-bedroom residence is proposed. A 1-bedroom Accessory
Dwelling Unit (ADU) may be added in the future.
The residence will be served by a community water system. The water line will enter the property from a
curb stop in the northwest corner of the property and enter the residence from the west. The water line
will be greater than 2S-feet from any proposed OWTS component.
The proposed soil treatment area (STA) location has an approximate 2 to 3 percent slope to the
northwest. The proposed area is vegetated with sage and native grasses.
There should be no traffic or staging of material over the future STA site to avoid compaction of soib
prior to construction of the STA.
SUBSURFACE
The subsurface was investigated on December 20,2023 by digging two soil profile test pit excavations (Test
Pits). A visual and tactile soil analysis was completed by Carla Ostberg at the time of excavation.l
The materials encountered in Test Pit #1 consisted of dark brown topsoil to 2-feet, underlain by whitish to
tan calcareous clay matrix to 5.0-feet with an approximate 4-inch gravel lense at 3-feet, underlain by tan
to light brown sandy loam to a maximum depth explored of 7.5-feet. No bedrock or groundwater was
encountered.
l Carla Ostberg holds a Certificate of Attendance and Examination from the CPOWVisual and Tactile
Evaluation of Soils Training.
Page2
The materials encountered in Test Pit #2 consisted of dark brown topsoil to 3-feet, underlain by tan sandy
loam to a maximum depth explored of 8.O-feet. No bedrock or groundwater was encountered.
A sample of the soil was taken from Test Pit #1 at 3-feet below grade. Soil structure grade was
moderate. The soilformed a ball and a ribbon less than 1-inch in length before breaking. Soilstructure
shape was single-grain to blocky and consistence was friable. Soil texture was more gritty than smooth
The subsurface was investigated by Kumar and Associates, Project No.21-7-790 and is documented in a
report dated December 1 5,2021 (enclosed). Three borings were sampled for the foundation design. All
three borings in the then-proposed house location show the horizon below the topsoil as sand and clay;
stratified, scattered gravel, silty, medium dense/stiff to hard, slightly moist, light brown.
The soil is consistent with Soil Type 2 with moderate structure grade. A long-term acceptance rate
(LTAR) of 0.6 gallons per square foot will be used to design the STA.
Test Pit #1
Sieved sample Ribbon less than 1-inch
Page 3
Test Pit #1
Backfill from Test Pit #1
Test Pit #1 looking west toward Test Pil#2
Backfillfrom Test Pil#2
Page 4
Test Pit #2
DESIGN SPECIFICATIONS
Desion Calculations:
Average Design Flow = 75 GPD x 2 people/bedroom x 3 Bedrooms + 150 GPD (4th and 5th Bedrooms) +
future 1-bedroom ADU (150 GPO; = 750 GPD
LTAR = 0.6 GPD/SF
750 GPD / 0.6 GPD/SF = 1250 SF x 1.0 (gravity trenches) x 0.7 (chambers) = 875 SF
The septic tank capacity is based on S-bedrooms in the main house. Additional septic tank capacity must
be added at the time of construction of the future 1-bedroom ADU. fhe STA is designed to
accommodate both the S-bedroom residence and future 1-bedroom ADU. An average daily wastewater
flow of 750 GPD will be used.
Page 5
For the purposes of this OWTS design, Benchmark Elevation at grade 7329' has been established as
100' Finished Floor (FF) of the Barn, which is connected to the main portion of the residence with a
breezeway. The main portion of the residence has a FF elevation of 7332.0. CBO lnc. should be notified
of any discrepancies or problems with grade elevations of proposed components during installation of the
OWTS.
*Elevations are based upon standard OWTS installation practices. Component elevations may change during
installation due to site conditions. Minimum grade refers to piping between components.
The 4-inch SDR-35 sewer lines exiting the main poftion of the residence and Barn must have a double-
sweep clean outs and a minimum 2o/o grade to the septic tank. There must be a clean out at least every
1OO-feet of sewer pipe length. We recommend a minimum Schedule 40 conduit be installed under the
driveway.
The system installation must include a 1S00-gallon, two-compartment lnfiltrator@ poly septic tank with an
Orenco@ Biotube effluent filter on the outlet tee. Risers must bring the manhole lids to grade for access.
lf more than one riser is added to the septic tank, an extension handle must be installed on the effluent
filter. The septic tank has been sized for the S-bedroom residence only. When a building permit
application is submitted forthe ADU, an additional OWTS Permit Application must also be filed for a
minimum 11l}-gallon, two-compartment septic tank to serve the proposed ADU.
Effluent will gravity flow to a distribution box, and then to five gravelless chamber trenches. The
distribution box must be accessible from grade and must have flow equalizers, or similar product,
installed on each outlet pipe in the distribution box to assure equal flow to each trench.
Each trench will consist of 15 'Quick 4' Standard Plus lnfiltrator@ chambers for a total of 75 chambers
and 900 square feet of infiltrative area. There must be at least 4-feet of undisturbed soil between each
trench. lnspection ports must be installed at the beginning and end of each trench. Ports may be cut to
grade and placed in sprinkler boxes for access.
COMPONENT SPECIFICATIONS
The component manufacturers are typical of applications used by contractors and engineers in this area.
CBO lnc. must approve alternative components prior to installation of the OWTS. Requests must
be submitted, in writing, to our office for approval prior to installation. Component technical data
sheets are available upon request.
OWTS Component Minimum Elevation
Residence to Primary Tank lnlet lnvert
Barn to Primary Tank lnlet lnvert
Approximate horizontal distance 142' I min.2%falll
min. 35.5" fall
Approximate horizontal distance 67' / min. 2% fall I
min. 16.75" fall
Distribution Box Approximate horizontal distance 38' / min. 1% fall I
min. 4.75" fall
lnfiltrative Surface Approximate horizontal distance 20' to furthest
trench / min. 1Vo fall to STA / min. 2.5" fall to
furthest trench
COMPONENT MANUFACTURER MODEL NO.COMMENTS
Septic Tank lnfiltrator@ tem # |M1530-2CP 1500-gallon, 2-
compartment poly septic
tank
Effluent Filter Orenco@ 4" diameter full size
effluent filter
Distribution Box,
risers, lid and flow
equalizers
Polylok 3 or 4'Roto-flow'
Chambers lnfiltrator@ 'Quick 4' Plus Standard 75 chambers
Page 6
Construction must be according to the jurisdiction's adopted On-Site Wastewater Treatment System
Regulations, the OWTS Permit, and this design.
PERMIT APPLICATION INSTRUCTIONS
An OWTS Permit Application must be submitted to Garfield County Environmental Health Department.
https:ilwrlltrtr.qarfield-county.com/environmental-health/filesgcco/sites/16/OWTS-AppliCation-Complete-
Packet-Dec.-2019.pdf. lf the OWTS PermitApplication will be submitted with a Building Permit
Application, it should be submitted directly to Garfield County Building Department.
All questions regarding permit submission can be directed to Garfield County Environmental Health
Department, 970-945-6614 x81 50.
INSTALLATION CONTRACTOR
CBO lnc. expects that the installer be experienced and qualified to perform the scope of work outlined in this
design. The installer must review this design thoroughly and coordinate with our office in advance of
installation. Any additional conditions in this design or county permit must be completed and documented
prior to final approval of the OWTS installation. Communication between the installer and this office is
expected throughout the installation.
I NSTALLATION OBSERVATIONS
CBO lnc. must view the OWTS during construction. The OWTS observation should be performed before
backfill, after placement of OWTS components. Septic tanks, distribution devices, pumps, dosing
siphons, and other plumbing, as applicable, must also be observed. CBO lnc. should be notified 48 hours
in advance to observe the installation.
ln an effort to improve the accuracy of the record drawing, we request that the installer provide a
sketch of the installation, including path of the sewer lines, water line installation (if applicable),
septic tank location, STA location, and measurements from building corners or another fixed
objects on the property. This sketch is most easily provided on Sheet W2.0 of the OWTS Design
Packet. Photographs of the installation and final cover are also requested to supplement our installation
documentation.
PageT
REVEGETATION REQUIREMENTS
An adequate layer of good quality topsoil capable of supporting revegetation shall be placed over the entire
disturbed area of the OWTS installation. A mixture of native grass seed that has good soil stabilizing
characteristics (but without taproots), provides a maximum transpiration rate, and competes well with
successional species. No trees or shrubs, or any vegetation requiring regular irrigation shall be placed over
the STA. Untii vegetation is reestablished, erosion and sediment control measures shall be implemented
and maintained on site. The owner of the OWTS shall be responsible for maintaining proper vegetation
cover.
OPERATION INFORMATION AND MAINTENANCE
The property owner shall be responsible for the operation and maintenance of each OWTS servicing the
property. The property owner is responsible for maintaining service contracts for manufactured units,
alternating STAs, and any other components needing maintenance.
Geo-fabrics or plastics should not be used over the STA. No heavy equipment, machinery, or materials
should be placed on the backfilled STA. Machines with tracks (not wheels) should be used during
construction of the STA for better weight distribution. Livestock should not graze on the STA. Plumbing
fixtures should be checked to ensure that no additionalwater is being discharged to OWTS. For example, a
running toilet or leaky faucet can discharge hundreds of gallons of water a day and harm a STA.
lf an effluent filter or screen has been installed in the OWTS, we recommend this filter or screen be cleaned
annually, or as needed. lf the OWTS consists of a pressurized pump system, we recommend the laterals be
flushed annually, or as needed.
The homeowner should pump the septic tank every two years, or as needed gauged by measurement of
solids in the tank. Garbage disposal use should be minimized, and non-biodegradable materials should not
be placed into the OWTS. Grease should not be placed in household drains. Loading from a water softe_ner
should not be discharged into the OWTS. No hazardous wastes should be directed into the OWTS.
Mechanical room drains should not discharge into the OWTS. The OWTS is engineered for domestic waste
only.
ADDITIONAL CONSTRUCTION NOTES
lf design includes a pump, weep holes must be installed to allow pump lines to drain to minimize risk of
freezing. The pump shall have an audible and visual alarm notification in the event of excessively high-
water cbnditions and shall be connected to a control breaker separate from the high-water alarm breaker
and from any other control system circuits. The pump system shall have a switch so the pump can be
manually operated.
Excavation equipment must not drive in the excavation of the STA due to the potential to compact soil.
Extensions should be placed on all septic tank components to allow access to them from existing grade.
Backfill over the STA must be uniform and granular with no material greater than minus 3-inch.
LIMITS:
The design is based on information submitted. lf soil conditions encountered are different from conditions
described in report, CBO lnc. should be notified. All OWTS construction must be according to the county
regulations. Requirements not specified in this report must follow applicable county regulations. The
contractor should have documented and demonstrated knowledge of the requirements and regulations of
the county in which they are working. Licensing of Systems Contractors may be required by county
regulation.
Page 8
Please call with questions.
Sincerely,
CBO lnc.
(nn[n Cstbr't et)
Carla Ostberg, MPH, REHS
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THE LOCATION OF PROPOSED IMPROVEMENTS SHOWN ARE
NOT THE RESULT OF A PROPERTY SURVEY. THE LOCATIONS
ARE APPROXIMATE. IT IS THE HOMEOWNERS' DUry TO
ENSURE ALL CONSTRUCTION AND IMPROVEMENT LOCATIONS
ARE ACCURATE. PROPERW LINES AND SETBACK DISTANCES
SHOULD BE CONFIRMED PRIORTO EXCAVATION. SCALED
FOR PRINTING ON 11'X 17" PAPER.
DRAWINGS MUST BE USED IN
CONJUNCTION WITH DESIGN
LETTER DATED 1212012023 1'- 50 :o'/A SITE PLAN\v
C4 77t t ARC=776.00'
RADIUS=885.00'
Cts=57 8"4+'5+'E
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CBO lnc.
129 Cains Lane
Carbondale, Colorado 81 623
Phone 970.309.5259
carla.ostberg @g mai I. com
Kempel Residence
Lot17, Ranch at Coulter Creek
Garfield County, Colorado
Project Number: C1851
ned by: CBO
1212012023
w1 .0
Drawn by: DD Sheet 1 0F 4
'-------'.......-
CLEANOUT (MtN. EVERY 100')
WYE FITTING TO TIE INTO 4'DIA SDR-35
SEWER PIPE (MtN 2%FALLTO SEPTTC
TANK)
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SCALE: 1" = 20'-0"
/
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SEPTIC TANK WITH EFFLUENT SCREEN
sOO-GALLON, TWO.COMPARTMENT
I
6'DIA MIN. SCHD4O
CONDUIT FOR SEWER
PIPE UNDER DRIVEWAY
4' DIA SDR-35 SEWER PIPE WITH DOUBLE SWEEP CLEANOUT
MIN 2% FALL TO TANK
1'= 2O' - 0'
LINE OF EXTERIOR WALL
/a PROPOSED OWTS
0
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TP1
1
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PROPERTY LIN
4" DIA SDR-35 DISTRIBUTION
LINE TO EACH TRENCH
(MrN. 1% SLOPE TO TRENCHS)
'QUICK4' CHAMBER TRENCHES.
5 TRENCHES WITH 15 CHAMBERS PER TRENCH
FORATOTAL OF 75 CHAMBERS AND 9OO SF.
4" DIA SDR-35 INSPECTION PORT AT
BEGINNING AND END OF EACH TRENCH
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1
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BARN
(FF = 7329')
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RESIDENCE
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FALL TOo/oN(M
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DISTRIBUTION BOX
WITH ACCESS AT GRADE
IMATE LOCATION
\4" DIA SDR-35 PVC SEWER LINE
36
CBO lnc.
129 Cains Lane
Carbondale, Colorado 81623
Phone 970.309.5259
carla.ostberg @gmail.com
Kempel Residence
Lot 17, Ranch at Coulter Creek
Garfield County, Colorado
Project Number: C1851
Date: 1212012023
Designed by: CBO
Drawn by: DD
w2.0
Sheet 20F 4
FINISHED GRADE
NOTE: INFILTRATIVE AREA MUST BE INSTALLED JUST
BELOWTHE TOPSOIL HORIZON, IN THE SANDY
LOAM/CALCAREOUS CLAY MATRTX HORTZON (SO|L
coloR wHtTlsH To TAN)
4'max
4' DIA SDR-35 SEWER LINE
(MtN 2olo SLOPE TO TANK,
MrN. 1% TO STA)
SCREENED ROCK
OR SAND FOR
BEDDING
24" MtN
3" MtN.L
LIMIT
EXCAVATION
SCARIFY SURFACE
SOIL
4" DIA SDR-35 DISTRIBUTION
LINE TO EACH TRENCH
(MrN. 1% SLOPE TO TRENCH)
4'DIA SDR-35
INSPECTION
PORT
GRAVELLESS 'QUICK.4'
CHAMBER (4'x 3')
ON
2'min
_l
4
8" MtN.
BOXAND COVER BROUGHT TO GRADE
CONCRETE LID
FINSHED GRADE
COMPACT SO
BASE TO SUPPORT
BOX
USE HOLE SAW TO
CUT THRUTOPOF
-
BAFFLE OR
ANGLED PIPE
TO BE USED
AT INLET
AIL
SMALL VALVE COVER
BOX OR IRRIGATION
VALVE BOXAT GRADE
CAP ORTHREADED
CLEANOUT ASSEMBLY
4'PVC PIPE CUT TO
FIT
12120t2023
4" DIA SDR-35 INSPECTION
PORT AT BEGINNING AND
END OF EACH TRENCH
15 CHAMBERS PER TRENCH
DISTRIBUTION BOX WITH
ACCESS AT GRADE
PIPES PLACED
TOP PORT OF
CHAMBER END
PLATES
" DIA SDR-35
EFFLUENT PIPE FROM
SEPTIC TANK
GRAVELLESS 'QUICK*4
CHAMBER (4'x 3')INFILTRATOR
END PLATE
CBO lnc.
129 Cains Lane
Carbondale, Colorado 81623
Phone 970.309.5259
carla.ostberg@gmail.com
Kempel Residence
Lot 17, Ranch at Coulter Creek
Garfi eld County, Colorado
Project Number: C1851
w3.0
by: CBO
DD
BACKFILL
OUTLETS
oooo
END
IN
by:Sheet 3 0F 4
DESIGN
s.BEDROOM RESIDENCE + FUTURE 1-BEDROOM ADU
75 GPD x 2 PERSONS/BEDROOM x 3 BEDROOMS + 150 GPD (4th and sth
BEDROOMS) + 150 GPD (1-BEDROOM ADU) = 750 GPD
WASTEWATER FLOW = 750 GPD
TANK:
RESIDENCE = MlN. 1500 GALLONS
USE 1sOO-GALLON, TWO-COMPARTMENT SEPTIC TANK. ADDITIONAL TANK
CAPACITY TO BE ADDED WHEN ADU IS CONSTRUCTED.
sorL TREATMENT AREA (STA):
LONG TERM ACCEPTANCE RATE (LTAR) = 0.6 GAUSF
CALCULATED STA = Q/LTAR =750 10.6 = 1250 SF
GRAVlry, TRENCHES = 1250 SF X 1.0 = 1250 SF
CHAMBERS = 1250 SF X 0.7 = 875 SF I 12 SF / CHAMBER = 73 CHAMBERS
FIVE GRAVELLESS CHAMBER TRENCHES
15'QUICK 4' CHAMBERS IN EACH TRENCH
TOTAL 75'QUICK 4' CHAMBERS
SOIL PROFILE TEST PIT NO. 1
DARK BROWN TOPSOIL
GRAVEL LENSE
WHITISH /TAN CALCAREOUS CLAY
MATRIX
TAN TO LIGHT BROWN SANDY LOAM
NO GROUNDWATER OR BEDROCK ENCOUNTERED
DURING EXCAVATION
SOIL PROFILE TEST PIT NO. 2
DARK BROWN TOPSOIL
TAN TO LIGHT BROWN SANDY LOAM
GRAVELS INCREASING WITH DEPTH
0
1
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2
3
4
5
6
7
8
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LEGEND
t= topsoil
Fll sandy
loam
OWTS COMPONENTS AND
PHYSICAL FEATURES
MINIMUM REQUIRED
SETBACK
APPROXIMATE PROPOSED
SETBACK
HOUSE/BARN TO SEPTIC TANK 5'28',
SEPTIC TANK TO WELL 50'N/A
SEPTIC TANKTO WATER COURSE 50'N/A
STA TO HOUSE/BARN 20'55'
STATO WELL 100'N/A
STATO WATER COURSE 50'N/A
fi
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SLIP-ON PVC
DO NOT GLUE
INSULATED
TRACERWIRE
4'DIA
SEWER LINE
TO TANK
-
FINISHED GRADE
TO HOUSE
w4.0
CBO lnc.
129 Cains Lane
Carbondale, Colorado 81623
Phone 970.309.5259
carla.ostberg@gmail.com
Kempel Residence
Lot 17, Ranch at Coulter Creek
Garfi eld County, Colorado
Project Number: C1851
Date: 1212012023
Designed by: CBO
Drawn by: DD
10
Sheet 4 0F 4