HomeMy WebLinkAboutOWTS Engineer's Design129 Cains Lane
Carbondale, CO 81623
970.309.5259
carla.ostberg@gmail.com
June 19, 2023 Project No. C1811
Ian Young
ityoungpainting@yahoo.com
Subsurface Investigation and Onsite Wastewater Treatment System Design
Triplex – 5 total bedrooms
182 Darrow Street
Garfield County, Colorado
Ian,
CBO Inc. performed a subsurface investigation and completed an onsite wastewater treatment system
(OWTS) design for the subject residence. The 10,453-square foot property is located outside of
Glenwood Springs, in an area where OWTSs are necessary.
Legal Description: Section: 27 Township: 6 Range: 89 Subdivision: CARDIFF, TOWNSITE-REPLAT
Block: 1 Lot: D 10454 SQ FT
Parcel ID: 2185-271-06-004
SITE CONDITIONS The property is currently developed with the existing structure that was mixed residential and commercial
use. A remodel of the structure is proposed that will result in a triplex with a total of 5 bedrooms.
The residence is served by a cesspool, which will be abandoned.
The structure is served potable water from a community water system. The water line enters the house
from the south and will not come within 10-feet of the proposed septic tank or 25-feet from the proposed
soil treatment area (STA).
We did a search on the Division of Water Resources website and it appears the nearest well is located
over 200-feet to the northeast of the proposed STA.
An electric line runs along the western portion of the property. Care should be taken to assure this is
properly located prior to excavation. A 15-foot easement runs along the northern property boundary.
Efforts should be made to avoid installation of any OWTS components within the easement.
With limited space on the property, the septic tank will need to be positioned between the structure and
the property line to the east. There may be slight encroachment on either the 5-foot setback to the
structure or the 10-foot setback to the property line.
The proposed soil treatment area (STA) location takes up most of the yard area to the north with 10-foot
setbacks to the property lines. The existing shed may need to be relocated. The proposed area is
vegetated with native grasses.
Page 2
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.
SUBSURFACE
The subsurface was investigated on May 30, 2023 by digging one soil profile test pit excavation (Test Pit). A
visual and tactile soil analysis was completed by Carla Ostberg at the time of excavation.1 Only one Test Pit
was excavated due to limited space on the property.
The materials encountered in Test Pit #1 consisted of road base to 6-inches, underlain by medium brown
topsoil, underlain by medium brown sandy loam with 35 to 65% cobbles to a maximum depth explored of
6.0-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 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.
The soil is consistent with Soil Type 2, Sandy Loam, with moderate structure grade. With rock content
between 35 and 65%, soils are classified as R-1. A pressure-dosed, over-excavated, unlined sand filter
system is specified with a minimum 2-feet sand filter material (Secondary Sand). A long-term
acceptance rate (LTAR) of 0.8 gallons per square foot will be used to design the STA.
Test Pit #1 Topsoil backfill
1 Carla Ostberg holds a Certificate of Attendance and Examination from the CPOW Visual and Tactile
Evaluation of Soils Training.
Page 3
Sieved sample
Sandy Loam with cobbles below 2-feet Backfill
DESIGN SPECIFICATIONS The existing cesspool will be abandoned by pumping any wastewater and solids and the remaining void
filled with onsite material.
Design Calculations:
Average Design Flow = 75 GPD x 2 people/bedroom x 5 Bedrooms = 750 GPD
LTAR = 0.8 GPD/SF
750 GPD / 0.8 GPD/SF = 937.5 SF
The OWTS design is based on 5-bedrooms. An average daily wastewater flow of 750 GPD will be used.
For the purposes of this OWTS design, Benchmark Elevation has been established as 100’ as the
elevation of the sewer line existing the residence. CBO Inc. should be notified of any discrepancies or
problems with grade elevations of proposed components during installation of the OWTS.
Page 4
OWTS Component Minimum Elevation
Primary Tank Inlet Invert Approximate horizontal distance 26’ / min. 2% fall /
min. 6.5” fall
Automatic Distributing Valve Approximate horizontal distance 4’ / min. 1% rise /
min. 0.5” rise
Infiltrative Surface Approximate horizontal distance to furthest bed 33’
/ min. 1% fall to STA / min. 4.125” fall
*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 existing sewer line should be entirely replaced with a new, 4-inch SDR-35 sewer line with a minimum
2% grade to the septic tank and a double-sweep clean out, which can be located outside of the concrete
patio area.
The system installation will include a 2000-gallon, two-compartment Valley Precast concrete septic tank
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 83 gallons each pump cycle, allowing
approximately 1 gallon of drain back. 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 start-up of the
pumping system.
Pump Table
Dose Range Max = 188.5 gal. (750 GPD x
25% + 1 gal drain back)
Min. 61 gal. (15 gal x 4) + 1 gal
drain back
Dose Setting 83 gallons/dose 22.5 gallons drain back (214’ /
1.5” diameter pump line)
Float Separation 2000 gallon 2-compartment
Valley Precast concrete septic
tank
6” on/off float separation
Pump Criteria 35.2 gallons per minute (GPM) 28.1 feet total dynamic head
(TDH)
Effluent will be pumped through a 1.5-inch diameter pump line from the pump chamber to an Orenco®
automatic distributing valve (ADV), model 6403. This pump line must have a minimum 1% grade for proper
drain back into the tank after each pump cycle. The ADV must be placed at a high point in the system 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 exiting the ADV remain visible for future inspection and maintenance.
Effluent will be pressure dosed to through 1.5-inch diameter distribution lines to three 12’ x 26’ bed. This
results in a total of 312 square feet per bed, and a total of 936 square feet. This is 1.5 square foot short of
the required area; however, given the constraints of the lot and the fact that this system replaces a cesspool,
the shortage will not adversely impact the overall functioning of the STA.
A minimum of 2-feet of sand filter material will be installed in the over-excavated footprints. Sand filter
material must be clean, coarse sand, all passing a screen having four meshes to the inch. The sand must
have an effective size between 0.15 and 0.60 mm. The uniformity coefficient must be 7.0 or less. Material
meeting ASTM 33, for concrete sand, with three percent or less fines passing 200 mesh sieve may be used.
A gradation of the sand media must be submitted to this office prior to obtaining the sand.
Laterals must be 1.5-inches in diameter with 5/32-inch diameter orifices facing down, spaced 2-feet on
center, installed on the GeoMat™ with the filter fabric over the laterals. Laterals should be placed 2-feet
from the edges of the bed with 3.0-feet between the laterals. Laterals will be connected with 1.5-inch
diameter level manifolds. Four 39” wide GeoMats™ must be placed on the 12-foot wide bed. All material
Page 5
associated with the GeoMat™ installation must be proprietary products associated with the GeoMat™,
including orifice shields and geotextile fabric. Manufacturer instructions must be followed regarding
installation of the GeoMat™.
Each 1.5-inch diameter lateral must end in a sweeping ell facing up with a ball valve for flushing. Valves
should be placed in a 10-inch sprinkler box for access. Laterals must be covered by a soil separation
fabric and at least 1-foot of topsoil or other suitable soil able to support vegetative growth. There shall be no
cobble-sized (>2.5”) or greater rock in final cover over the GeoMat™. Inspection ports must be placed at
each corner of each bed. 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.
CBO Inc. 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.
COMPONENT MANUFACTURER MODEL NO. COMMENTS
Septic Tank Valley Precast Item # 2000T-2CP-HH 2000-gallon, 2-
compartment concrete
septic tank with high
head pump
Pump Orenco® PF300511 ½ HP
120 Volt
Biotube ProPak Pump Package Orenco® BPP30DD Vault, Filter, Control Panel (demand dose)
Tank Risers and Lids Orenco® Double-walled PVC Risers and Lids (24” diameter)
ADV Orenco® V6403A 1.5” Inlet and Outlets
ADV Riser and Lid Orenco® Double-walled PVC Risers
and Lids (30” diameter) Flushing Assembly Orenco® 1.5” diameter (2) 45° or 90° long sweep only (12 total) GeoMat™ GeoMatrix Systems, LLC GeoMat™ and Orifice Shields 312’ GeoMat™ (39”) and 144 Orifice Shields
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://www.garfield-county.com/environmental-health/filesgcco/sites/16/OWTS-Application-Complete-
Packet-Dec.-2019.pdf. If the OWTS Permit Application 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 x8150.
Page 6
INSTALLATION CONTRACTOR
CBO Inc. 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.
INSTALLATION OBSERVATIONS CBO Inc. 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 Inc. should be notified 48 hours
in advance to observe the installation.
In 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.
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. 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 additional water 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.
If an effluent filter or screen has been installed in the OWTS, we recommend this filter or screen be cleaned
annually, or as needed. If 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.
Page 7
ADDITIONAL CONSTRUCTION NOTES If 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 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. If soil conditions encountered are different from conditions
described in report, CBO Inc. 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.
Please call with questions.
Sincerely,
CBO Inc.
Carla Ostberg, MPH, REHS
Pump Selection for a Pressurized System - Multiple Family Residence Project
Compass Peak Properties / 182 Darrow Street
Parameters
Discharge Assembly Size
Transport Length Before Valve
Transport Pipe Class
Transport Line Size
Distributing Valve Model
Transport Length After Valve
Transport Pipe Class
Transport Pipe Size
Max Elevation Lift
Manifold Length
Manifold Pipe Class
Manifold Pipe Size
Number of Laterals per Cell
Lateral Length
Lateral Pipe Class
Lateral Pipe Size
Orifice Size
Orifice Spacing
Residual Head
Flow Meter
'Add-on' Friction Losses
1.25
4
40
1.50
6403
33
40
1.50
3
8
40
1.50
12
24
40
1.50
5/32
2
5
None
0
inches
feet
inches
feet
inches
feet
feet
inches
feet
inches
inches
feet
feet
inches
feet
Calculations
Minimum Flow Rate per Orifice
Number of Orifices per Zone
Total Flow Rate per Zone
Number of Laterals per Zone
% Flow Differential 1st/Last Orifice
Transport Velocity Before Valve
Transport Velocity After Valve
0.68
52
35.2
4
0.4
5.6
5.6
gpm
gpm
%
fps
fps
Frictional Head Losses
Loss through Discharge
Loss in Transport Before Valve
Loss through Valve
Loss in Transport after Valve
Loss in Manifold
Loss in Laterals
Loss through Flowmeter
'Add-on' Friction Losses
8.7
0.3
8.6
2.3
0.2
0.1
0.0
0.0
feet
feet
feet
feet
feet
feet
feet
feet
Pipe Volumes
Vol of Transport Line Before Valve
Vol of Transport Line After Valve
Vol of Manifold
Vol of Laterals per Zone
Total Vol Before Valve
Total Vol After Valve
0.4
3.5
0.8
10.2
0.4
14.5
gals
gals
gals
gals
gals
gals
35.2
28.1
gpm
feet
0 5 10 15 20 25 30 35 40
0
50
100
150
200
250
300
Net Discharge (gpm)
PumpData
PF3005 High Head Effluent Pump
30 GPM, 1/2HP
115/230V 1Ø 60Hz, 200V 3Ø 60Hz
PF3007 High Head Effluent Pump
30 GPM, 3/4HP
230V 1Ø 60Hz, 200/460V 3Ø 60Hz
PF3010 High Head Effluent Pump
30 GPM, 1HP
230V 1Ø 60Hz, 200/460V 3Ø 60Hz
PF3015 High Head Effluent Pump
30 GPM, 1-1/2HP
230V 1Ø 60Hz, 200/230/460V 3Ø 60Hz
Legend
System Curve:
Pump Curve:
Pump Optimal Range:
Operating Point:
Design Point:
2,257
376.2
Map Viewer
This product is for informational purposes and may not have been prepared for, or be suitable for legal,
engineering, or surveying purposes. Users of this information should review or consult the primary data and
information sources to ascertain the usability of the information.
1,7541:
Feet2920
Legend
146
Notes
Location
292
Date Prepared: 6/19/2023 11:45:22 AM
Well Constructed
Final Permit
County
40.0'
50
.
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40.0'
50
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SHED
TWO STORY
DUPLEX
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182 DARROW
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FOUND REBAR &
1-1/4" ORANGE
PLASTIC CAP
SURVCO PLS27619
FOUND REBAR &
1" YELLOW PLASTIC
CAP SOLAR LS14111
PAVED ROADWAY
36
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OVERHEAD POWER LINE
LOT D
LOT C
LOT E
GAS METERG
LEGEND
IMPROVEMENT LOCATION CERTIFICATE
I HEREBY STATE THAT THIS IMPROVEMENT LOCATION CERTIFICATE WAS PREPARED BY TRUE NORTH COLORADO, LLC FOR EMILY LONGFELLOW
THAT IT IS NOT A LAND SURVEY PLAT OR AN IMPROVEMENT SURVEY PLAT, AND THAT IT IS NOT TO BE RELIED UPON FOR THE
ESTABLISHMENT OF FENCE, BUILDING, OR OTHER FUTURE IMPROVEMENT LINES.
I FURTHER STATE THAT THE IMPROVEMENTS ON THE ABOVE DESCRIBED PARCEL ON THIS DATE OF APRIL 3, 2023. EXCEPT UTILITY
CONNECTIONS, ARE ENTIRELY WITHIN THE BOUNDARIES OF THE PARCEL, EXCEPT AS SHOWN, THAT THERE ARE NO ENCROACHMENTS UPON
THE DESCRIBED PREMISES BY IMPROVEMENTS ON ANY ADJOINING PREMISES, EXCEPT AS INDICATED, AND THAT THERE IS NO APPARENT
EVIDENCE OR SIGN OF ANY EASEMENT CROSSING OR BURDENING ANY PART OF SAID PARCEL, EXCEPT AS NOTED.
RODNEY P. KISER
LICENSED PROFESSIONAL LAND SURVEYOR
COLORADO REGISTRATION NO. 38215
PROJECT NO: 2023-177
DATE: April 5, 2023
DRAWN
RPK
SURVEYED
DJB
SHEET
1 OF 1
TRUENORTH
A LAND SURVEYING AND MAPPING COMPANY
PROPERTY DESCRIPTION
LOT D, BLOCK 1
A REPLAT OF A PORTION OF THE TOWNSITE OF CARDIFF
RECORDED JANUARY 9, 1985 AS RECEPTION NO. 358620
COUNTY OF GARFIELD, STATE OF COLORADO
TRUE NORTH COLORADO LLC.
A LAND SURVEYING AND MAPPING COMPANY
P.O. BOX 614 - 386 MAIN STREET UNIT 3
NEW CASTLE, COLORADO 81647
(970) 984-0474
www.truenorthcolorado.com
SCALE: 1" = 30'
N
ELECTRIC PEDESTAL
POWER POLE
Gar eld County, CO
Developed by
Account
Number
R080685
Parcel
Number
218527106004
Acres 0
Land SqFt 10,453
Tax Area 008
2019 Mill Levy 80.5200
Physical
Address
182 DARROW ST
GLENWOOD SPRINGS 81601
Owner
Address
COMPASS PEAK PROPERTIES
LLC
PO BOX 3555
GLENWOOD SPRINGS CO
81602
2019 Total Actual
Value
$623,180 Last 2 Sales
Date Price
5/23/2023 $665,000
7/6/2018 $100
Date created: 6/19/2023
Last Data Uploaded: 6/19/2023 2:08:26 AM
94 ft
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