HomeMy WebLinkAboutOWTS Installation Observations 10.09.2023October 9, 2023
502 Main Street • Suite A3 • Car bondale, CO 81623 • (970) 704 -0311 • Fax (970) 704 -0313
S OPRIS E NGINEERING • LLC civil consultants
Jordan Kobielusz
J&C services
Martin Ranch II LLC
PO Box 654,
Carbondale, CO81624
"Jordan Kobielusz" jcservices21@yahoo.com (970)319-9918
RE: As-Constructed Report, On-site Wastewater Treatment System (OWTS), 3602 County RD 108,
Carbondale Garfield County, CO, Lot 2. AKA Parcel 1 Martin Exemption
SE Job No. 33027.01, Parcel No: 239536400152. Garfield County EHD Permit # SEPT-8164
Dear Jordan:
Pursuant to County requirements, this letter provides documentation that the Onsite Wastewater Treatment
System (OWTS) upgraded components recently installed at the above referenced site is in compliance with
the permitted design. Sopris Engineering inspected the excavations, soils, materials and the installation of
the system components during construction, prior to final backfill and after all installations were
completed. The replacement absorption field and pump dosing/ distribution component installations were
designed and constructed to serve the proposed usage on the subject property.
Sopris Engineering performed site visits to inspect and document the as-constructed conditions of the
OWTS. Inspections were coordinated with the property owner that installed the system components. The
as-constructed conditions and installation of the OWTS components is in compliance with Garfield County
regulations. The installed system with specifications is delineated on the civil as-constructed exhibit, C3-
OWTS Plan dated 06-16-2023, by Sopris Engineering.
OWTS Conditions and Design Criteria
Constructed OWTS System
The system was constructed to provide for demand dosing of septic tank effluent to an engineered soil
treatment area (STA) pursuant to Regulation 43 design criteria. The OWTS includes gravity sewer service
pipe from the dwelling to a 1,250-gallon concrete 2-compartment septic tank. The tank lids risers and lids
were extended to the finish surface. The new tank will be equipped with a high head pump assembly to
provide full pressure dosing of the STA field.
The STA system is designed based on the current design criteria for the use of pressure dosed chamber
trench system. Specifically the preferred treatment technology is individual pressure dosed gravelless
chambers installed in native soils with custom perforated distribution laterals. The sizing is based on
utilizing applicable multiplier loading rates for pressure dosed chamber distribution in trench configurations
per the estimated design flow capacities. The system is in compliance with area calculations based on the
LTAR loading rate for the in-situ soils utilizing shallow pressure dosed low profile infiltrator chamber
trenches set level on the native soil infiltrative surface .
OWTS Upgrade Design and Construction
3602 County RD 108
SE Job No. 33027.01
October 9, 2023
Page 2
The system includes the installation of an Orenco System bio tube simplex effluent pump assembly for
pressure distribution of septic tank effluent to the pressure dosed chamber trenches. The effluent discharge
piping from the pump assembly has been installed to connect to a distribution tee connecting at the center
of a common manifold pipe with individual distribution pipes to the head of each chamber trench. Each
trench has appropriate inspection ports and appurtenances installed on the head and distal ends of each
trench.
Design Calculations OWTS
The onsite wastewater treatment system (OWTS) was installed to serve a 3-bedroom residential facility.
The design flow treatment capacity is calculated as follows for a minimum equivalent 3-bedroom single
family residence.
From the Regulation 43 usage table:
Minimum population based on 3 bedrooms = 6 persons.
Gallons per day per person = 75 gal/person/day, No peaking factor
Max. Design flow (Qd) gallons/day = (# of people) x (avg. flow) gal/person/day.
Design flow Qd = 6*75=450 gpd
Septic Tank Design:
Installed a 1250 gallon, two compartment concrete septic tank with a high head pump assembly in the
second chamber.
Preliminary Sub Surface Conditions and Testing
A subsurface soil investigation and site assessment was performed by Kumar & Associates on February 10,
2023. The soils in the proposed field envelope area were sampled and characterized by application of
hydrometer and sieve analysis from samples from three 4-5 foot deep profile pits the shallow soils in these
excavations were sampled, observed and tested at 2-3, and 4-5 foot depths.
The soils below a foot of topsoil consist of relatively dense, sandy silt loam. Soils on the easterly side of the
building envelope had some gravels and scattered cobble size sandstone rock fragments. The soils in the
vicinity of the installed STA appear to be consistent to across the trench field area to 6-7 feet depth and did
not have any significant rock content as compared to excavations to the east. No free water was
encountered in the pit excavations and soils were slightly moist to moist. Seasonal high groundwater levels
are expected to be below 15 feet from the existing surface grades in the area of the proposed field.
The native soils sampled from 2-5 feet below the surface, in the vicinity of the 4 parallel trench, are
characterized as a soil type 2 sandy silt loam with rock content less than10%. The soils have an effective
loading rate for of 0.6 Gal/S.F./day for a level 1 treatment system. The equivalent percolation rate is
assumed to be 16-25 minutes per inch.
Soil Treatment Area/ Pressure dosed chamber trench Absorption System Design
OWTS Upgrade Design and Construction
3602 County RD 108
SE Job No. 33027.01
October 9, 2023
Page 3
The treatment/absorption trenches were designed based on utilizing the effective Long Term Acceptance
Rate (LTAR) for native soils and the application of appropriate loading factors for a new soil treatment
area system utilizing pressure dosed chamber trenches with custom perforated distribution laterals installed
in native soil, in accordance with Regulation 43 design criteria for this technology.
Long Term Acceptance Rate (LTAR)
Considering the allowable application of the OWTS regulation 43 and CDPHE approved Distribution
Product for Infiltrator Water Technologies, Quick4 Infiltrators product:
Receiving septic tank effluent, the treatment level-1 for Quick4 Chambers requires the infiltrative surface
being at least 4-feet above a limiting layer (43.8, Table 7-2.4); Maximum hydraulic loading rate for TL1
effluent is the long term acceptance rate of the Type 2 receiving soil is 0.6 gal./S.F./day) (Table 10-1 &10-
1A.).
A(sf) = Qd x L.F.1 x L.F.2.: A = Area;
LTAR LTAR = 0.6 gal/S.F./day for silt loam
Qd = flow (gal/day) for OWTS = 450 gpd
L.F.1=0.8 pressure dosed trench application
L.F.2=0.7 Gravelless chambers
OWTS: A(sf) = 450 gpd x 0.8 x 0.7 = 420 S.F.
0.6 Gal/S.F./day
Number of Quick-4 LP Infiltrator chambers 4'x3'x8"chambers:
420 S.F = 35 Infiltrator Quick-4 chambers; Use 40 Quick-4 LP chambers
12 S.F./Chamber
A total of 40 Quick-4 Low Profile Infiltrator chambers were installed in four trenches (42' long by 3' wide)
with 10 chambers per row plus. The trenched were installed with end caps and inspection ports as
delineated on the As-Constructed Record drawing. The septic tank effluent was pressure distributed to the
head of each trench via distribution pipe manifolds from a high head pump discharge assembly in the
second compartment of the 1,250 gallon tank.
Effluent Distribution System
Filtered effluent discharges to the trench laterals via a 1.5 inch diameter transport pipe from the high head
pump biotube discharge assembly to the distribution pipe manifolds between the septic/dosing tank and the
head of the STA trenches.
The distribution system was installed to allow for effluent to be equally distributed across the absorption
surface in each trench via individual custom perforated full pressure distribution laterals connected to the
manifold pipes at the head of each trench installed on the native soil surface along the entire length of the
individual trenches. A ball valve was installed on the terminal end of each distribution lateral centered