HomeMy WebLinkAboutSubsoil Study and OWTS Design33 FoUR WHEEL DRIVE RoAD
C¡ReoNo¡LE, CO A1623
970.309.5259
CARLA.OSTBERG@GMATL.coM
Httl,'l.Ic (:l)ñrsil._f I.'l! I¡Í(;
May 31 ,202'l Project No. C1529
Erich Kaiter
ekaitertOcololq.com
Subsurface lnvestigation and Onsite Wastewater Treatment System Design
2-Bedroom Accessory Dwelling Unit (ADU) / Shop
4-Bedroom Residence
7484CR 100 (Parcel B)
Garfield County, Colorado
Erich,
CBO lnc. performed a subsurface investigation and completed an onsite wastewater treatment system
(OWTS) design for the subject residence. The 7.98-acre property is located outside of Carbondale, in an
area where OWTSs and wells are necessary.
Legal Description: Section: 1B Township: 7 Range: 87 TR lN LOT 147.98 ACRES (PARCEL B)
Parcel lD: 2391-181-00-025
SITE CONDITIONS
The property has recently been subdivided. The proposed development will take place on Parcel B. A
detached shop and 2-bedroom Accessory Dwelling Unit (ADU) is proposed. A future 4-bedroom
residence is also proposed but will not be constructed at this time.
The residences will be served by a private well located near the north property boundary. The well is
located at least S0-feet from the proposed septic tanks and at least 1OO-feet from the proposed soil
treatment area (STA).
A ditch bisects the property north and south. The proposed Shop/ADU will be located to the west of the
ditch and the STA to the east of the ditch. No OWTS component will come within S0-feet of the ditch,
and the sewer line will cross over the ditch above an existing culvert. The sewer line will be encased per
W3.0/5 Encasement Detail in minimum Schedule 40 pipe within 5O-feet of the open portion of the ditch.
The proposed soil treatment area (STA) location has an approximate 25 percent slope to the west. The
proposed area vegetated with native grasses, sage, and scrub oak.
There should be no traffic or staging of material over the future STA site to avoid compaction of soils
prior to construction of the STA.
Page2
SUBSURFACE
The subsurface was investigated on June 9,2020 by digging two soil prof¡le test pit excavations (Test Pits).
A visual and tactile soil analysis was completed by Carla Ostberg at the time of excavation.I At the time the
Test Pits were excavated, there was limited access due to existing vegetation on the hillside and the
machine was staged on the existing road.
The materials encountered in Test Pit #1 consisted of medium brown topsoil to 2.O-feet, underlain by light
brown to tan calcareous clay matrix to a maximum depth explored of 7.O-feet. No bedrock or groundwater
was encountered.
The materials encountered in Test Pit #2 consisted of medium brown topsoil to 2.O-feet, underlain by light
brown to tan calcareous clay matrix to a maximum depth explored of 7.O-feet with less rock than Test Pit
#1. No bedrock or groundwater was encountered.
A sample of the soils was taken from Test Pit #1 at 3-feet below grade. Soil structure grade below 3.0-
feet was weak. The soil formed a ball and a ribbon less than 1-inch in length before breaking. Soil
structure shape was blocky and consistence was friable. Soil texture was more gritty than smooth.
Soils are consistent with Soil lype 2 with moderate structure grade. A long term acceptance rate
(LTAR) of 0.6 gallons per square foot will be used to design the OWTS.
DESIGN SPECIFICATIONS
Desiqn Calculations:
ADU = 75 GPD x 2 people/bedroom x 2 Bedrooms = 300 GPD
Main House = 75 GPD x 2 people/bedroom x 4 Bedrooms = 600 GPD
Average Daily Flow = 900 GPD
LTAR = 0.6 GPD/SF
900 GPD / 0.6 GPD/SF x 0.8 (pressure dosed trenches) x 0.7 (chambers) = 840 SF
The OWTS design is based on 2-bedrooms in the Shop/ADU and 4-bedrooms in the future main house.
An average daily wastewater flow of 900 GPD will be used.
For the purposes of this OWTS design, Benchmark Elevation has been established as finished floor of
the Shop/ADU as 100'. CBO lnc. should be notified of any discrepancies or problems with grade
elevations of proposed components during installation of the OWTS.
The sewer line exiting the Shop/ADU must have a double-sweep clean out and a minimum 2o/o grade to
the septic tank. The system installation will include a 1OO0-gallon, two-compartment lnfiltrator@ poly
septic tank with an Orenco@ Biotube Effluent Filter on the outlet tee. A 4-inch diameter SDR-35 sewer
I Carla Ostberg holds a Certificate of Attendance and Examination from the CPOW Visual and Tactile
Evaluation of Soils Training.
OWTS Gomponent Minimum Elevation
Primary Tank lnlet lnvert Approximate horizontal distance 9' / min. 2o/o fall to
septic tank / min.2.25" fal/.
Pump Chamber Approximate horizontal distance 137' I min. 1% fall I
min.17.125" tall
Automatic Distributing Valve Approximate horizontal distance 90'/ min. 1o/o rise I
min. 11.25" rise for drain back
lnfiltrative Surface Approximate horizontal distance to lowest trench
40' / min. 1% fall / min. 5" fall to Iowest trench
Page 3
line must be installed existing the septic tank and will cross the ditch over the existing culvert. The 4-inch
diameter sewer line must be encased per W3.0/5 Encasement Detail within 5O-feet of any open portion of
the ditch. Additionally, if the length of the sewer line between the tanks exceeds 1O0-feet, a clean out
should be installed. This office should be contacted once the sewer line route is established to
determined if an additional clean out is warranted as installation of a clean out will not allow encasement
of the pipe at the clean out location.
An additional septic tank must be installed to serve the proposed 4-bedroom main house at the
time of construction. An OWTS Permit must be obtained with the building permit for the main
residence prior to installation.
A 5O0-gallon lnfiltrator@ poly pump chamber will be installed with an Orenco@ Biotube Pump Vault and an
Orenco@ PF3005 pump in the second compartment of the septic tank. The floats should be set to dose
approximately 80 gallons each pump cycle, allowing approximately 10 gallons of drain back after each
pump cycle. A pump curve is enclosed. The control panel for the pump must be located within line of sight
of the septic tank. We recommend Valley Precast out of Buena Vista be contracted for staft-up of the
pumping system.
Table
A 1.5-inch diameter Schedule 40 pump line must be installed from the pump to an Orenco@ automatic
distributing valve (ADV), model 6605. This pump line must have a minimum 1o/o grade for proper drain back
into the tank after each pump cycle. The ADV must be placed a high point in the system and be placed in
an insulated riser with access from grade. Screened rock must be placed below the ADV to support the
ADV and to assure the clear pipes existing the ADV remain visible for future inspection and maintenance.
Effluentwill be pressure dosed through 1.S-inch diameter pipes to five trenches, each with 14'Quick 4'
Standard Plus lnfiltrator@ chambers, for a total of 70 chambers and 840 square feet of infiltrative area.
There must be at least 4-feet of undisturbed soil between each trench. Effluent will be pressure dosed to
1.S-inch diameter laterals, which must be hung with zip ties from the underside of the chambers. Laterals
will have 5/32-inch diameter orifices facing up, with the exception of the first and last holes facing
down for drainage. Orenco@ Orifice Shields may be placed under each downward-facing orifice. The
orifices must be placed 2.5-feet on center. Each lateral must end in a 90 degree ell facing up with a ball
valve for flushing. Valves may be placed in a valve box, accessible from grade, for access. lnspection
ports must be placed at the beginning and end of each trench. Ports may be cut to grade and covered
with a valve box for access.
COMPONENT SPECIFICATIONS
The component manufacturers are typical of applications used by contractors and engineers in this area.
GBO 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.
Max = 235 gal. (900 GPD x25o/o
+ 10 oal drain back)
Min. 50 gal. (10 galx 4) + 10 gal
drain back
Dose Range
Dose Setting B0 gallons/dose 10 gallons drain back (90' / 1.5"
diameter pumo line)
Float Separation 500 gallon single-compartment
lnfiltrator@ poly pump chamber
6" on/off float separation
15.7 gallons per minute (GPM)27.7 feet total dynamic head
fiDH)
Pump Criteria
Page 4
Construction must be according to Garfield County On-Site Wastewater Treatment System Regulations, the
OWTS Permit provided by Garfield County Building Department, and this design.
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 additionalconditions 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.
INSTALLATION 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.
COMPONENT MANUFACTURER MODEL NO COMMENTS
Septic Tank lnfiltrator@ tem # lM-'l060-2CP 1000-gallon,2-
:ompartment poly septic
lank
Effluent Filter Orenco@ 4-inch diameter, full size
filter and housinq
Pump Tank lnfiltrator@ Item # lM-540-HH 50O-gallon, single
compartment poly pump
chamber
Pump Orenco@ PF300511%HP
120 Volt
Biotube ProPak Pump
Packaoe
Orenco@ BPP30DD Vault, Filter, Control Panel
ldemand dose)
Tank Risers and Lids Orenco@ Douþle-walled PVC l-(tsers and
Lids (24" diameter)
ADV Orenco(Ð v66054 1.5" lnlet and Outlets
ADV Riser and Lid Orenco@ Double-walled PVC Risers
and Lids (30" diameter)
Orifice Shields Orencoc)os150 1.5 inch diameter (10 total)
Flushing Assembly Orenco@ 1.5" d¡ameter (2) 45" or 90" long sweep only
(5 total)
Chambers lnfiltrator@ Low Profile 70 'Quick 4' Standard Plus
Chambers
Page 5
REVEGETATION REQU IREMENTS
An adequate layer of good qual¡ty 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. Until 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 softener
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 conditions 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 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 6
Please call with questions.
Sincerely,
CBO lnc.
Carla Ostberg, MPH, REHS
fuj"tø-*xe<Ng
Reviewed By:
Romeo A. Baylosis, PE
I
I3fi6t$
6-4-2021.*
Pump Selection for a Pressurized System - Single Family Residence Project
Kaiter/Ogden Residence / 7484 CR 100 / Parcel B
Peremeters
Discharge Assembly S¡ze
Transport Length Before Valve
Transport P¡pe Class
Transport Line Size
Distr¡but¡ng Valve l\rodel
Transport Length After Valve
Transport Pipe Class
Transport Pipe Size
Max Ëlevation L¡ft
Manifold Length
Manifold Pipe Class
Manifold P¡pe S¡ze
Number of Laterals per Cell
Late.al Length
Lateral Pipe Class
Lateral Pipe Size
Orifce S¡ze
Or¡l¡ce Spac¡ng
Residual Head
Flow Mete¡
'Add-on' Frict¡on Losses
Calculations
90
40
L50
6605
40
40
1.50
13
0
40
1.50
56
40
L50
5t32
2.5
5
None
0
¡nches
feet
inches
feet
inches
¡nches
leet
inches
inches
300
250
200
150
100
50
0
feet
feet
feet
feet
inches
feet
ItIt¡IL
t.E:l-
.E
!dÉ-
,.ä
EF
:r+
'lfü
Êt&
M¡nimum Flow Rate per Orifìce
Number of Or¡f¡ces per Zone
Total Flow Rate per Zone
Number of Laterals per Zone
% Flow Different¡al lst/Last Or¡f¡ce
Transport Velocity Bêfore Valve
Transport Veloc¡ty After Valve
Frictional Head Losses
0.68
23
15.7
1
2.9
gpm
gpm
o/o
fps
fps
Loss through Discharge
Loss in Transport Before Valve
Loss th¡ough Valve
Loss ¡n Transport afrer Valve
Loss in Manifold
Loss in Laterals
Loss lhrough Flowmeter
'Add-on' Frict¡on Losses
Pipe Volumes
1.4
5.6
0.6
0.0
0.3
0.0
0.0
feet
feet
feet
feet
feet
feet
feet
feet
Vol ofTrânsport Line Before Valve
Vol ofTransport L¡¡e Aíler Valve
Vol of Manifold
Vol of Laterals perZone
Total Vol Before Valve
Totâl Vol Afler Valve
gals
gals
gals
gals
gals
gals
9.5
4.2
0.0
5.9
10.2
0 10
Minimum Pump Requirements
15 20 25
Net Discharge (gpm)
30 35 40
System Curye:
Pump_ Curye:
Pump OptimaLEange:
Operat¡69:Poinl:
DesiSboint:
Design Flow Rate
Totãl Dynamic Head
15.7
27.7
gpm
feet PumpData Legend
PF3005 High Head Effluent Pump
30 GPM, I/2HP
1151230V 1ø 60H2,2O0V 3ø 60Hz
PF3007 High Head Ef¡uent Pump
30 GPM, 3/4HP
230V 1ø 6OHz,2001460v 3ø 60Hz
PF30l0 High Head Effluent Pump
30 GPM, ,IHP
23OV 1ø 60H2,2001460V 3ø 60Hz
PF30'15 High Head Efiluent Pump
30 GPM, l-1l2HP
230v 1ø 6oHz,2O0l23Ol460V 3Ø 6oHzK,ørcø**Eñ
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# qFublic.net'" Garfield County, CO
Overuiew
Legend
] Parcels
Roads
Parcel/Account
Numbers
Highways
: LimitedAccess
* Highway
Major Road
' Local Road
."" Minor Road
Other Road
Ramp
" Ferry
Pedestrian Way
Owner Name
iLakes&Rivers
* County Boundary
Line
AccountNumber RO7722O
Parcel Number 239tlB7OOO25
Acres I
Land SqFt 0
TaxArea 011
2019 Mill Levy 75.5380
Date created:5/8/2O27
Last Data Uploaded: 5/8/2O27 3:O5:I7 AM
D eve rope d or É) 9."å,9,å'r4pf
Physical Address 7484 100COUNTY RD
CARBONDALE 8T623
Owner Address KAITER, ERICH L
1710 13TH STREET
BOULDER CO BO3O2
2Ol9TotalActualValue $8ó5,930 Last2Sales
Date Price
3/17/2027 $O
3/77/2027 $O