HomeMy WebLinkAboutOWTS Installation Observations 11.01.2023RE:
November 7, 2O2
Steven & Christine Nilsson,
787 Canyon Creek Dr,
Glenwood Sptittgs CO 8160
"Client EM address"
Design Report-Onsite Wastewater Treatment System (OWTS), Nilsson Residence, 167 Shore Dr, Silt CO,
Lot 2, Riverview Ranch Subdivision, Garfield County, Colorado, Parcel No: 217912301002
SE Job No. 32029.01. Garfield County OWTS Permit No. SEPT-08-22-7743
Dear Steven:
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 fînal backfill and after all installations were completed. The installed absorption field
and tank was desigrred and constructed to serve the 4-bedroom residential property.
Sopris Engineering performed site visits to inspect and document the as-constructed conditions of the OWTS.
Inspections were coordinated with the property owner and the Contractor, which installed the new system
components. The as-constructed conditions and installation of the new OWTS components is in compliance with
Garfield County Regulations; the recommendations and specifications delineated on the civil Cl OWTS plan drawing
dated 07-08-2022by Sopris Engineering. The desigr criteria and system sizing information is summarized below.
The As-Constructed OWTS components were completed as delineated on the design construction document plan
previously submitted for permit.
OWTS Conditions and Desisn Criteria
The O'WTS is designed for a treatment capacity of 525 gallons per day based on the design wastewater flow to serve
a 4-bedroom residence in accordance with Table 6-2 values, Section 43.6, A.4. The OWTS utilizes a 1,250 gallon
two-compartment concrete septic tank installed off the south westerly corner of the structure. Sealed ribbed PVC
risers with lids are installed on the new septic tank along with appropriate pipe connection to the new tank utilizing
the appropriate fitting adaptor rings for the tank and riser. The new 1,250 gallon 2-compartment septic tank was
installed with the appropriate sanitary tees, outlet effluent filter with risers and lids at the surface. A gravity shedule-
40 PVC sewer pipe section with a two-way cleanout was installed from the dwelling to the tank inlet.
The STU consists of leaching chamber trenches that provide 624 S.F. of total absorption area. The septic tank
effluent is discharçd via gravity througþ a -inch Shed-40 PVC pipe, installed at l.5Yo slope, to the STU via a
plastic distributionbor The effluent is equally distributed from the distribution box via 4" distributionpipes
connected to the head end cap of each chamber trench. Observation ports with caps were installed on the proximal
and distal ends of each chamber trench. The design is in compliance with the current County regulations with design
calculations based on the soil type, texture and structure with an appropriate long term acceptance rate (LTAR). The
installed system meets all required setbacks and is installed within the general location indicated on the plan.
5O2 //lain 5þreeþ a îuiþe â3 . Carbondale, CO 81623
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$oPnrs IttGmIIRmG o 11G civil consulþants
OWTS Nilsson Residence,
167 Shore Dr, Silt, CO
SE Job No. 32029.01
Novcmber 1,202:3
Page2
Desisn Flow
The design flow was calculated as follows for the minimum desigr capacity of an equivalent 4-bedroom residential
dwelling.
Minimumpopulation based on4 bedrooms at 2 persons per bedroom and a fourth beclroom at 1 person per
each additional bedroom over 3, equatingto 7 persons.
The Design flow is calculated based on residential usage of 75 gallpersorVday, No PF
Max. Desigr flow (Qd) gallons/day: (# of people) x (avg. flow) ga1/person/day.
Design flow Qd :7*75:525 Wd
Sub Surface Conditions and Testins
A previous subsurface soil investiption was performed by Kumar & Associates, Inc. June gth,2022. The result of
the soils evaluation is presented in the subsoil study for foundation desigr and percolation test, proposed residence
of loL2, river view ranch subdivision at 167 shore drive in Garfield County Colorado. The subsurface conditions
were evaluated by excavation ofthree exploratory borings in the building envelope. The soils encountered in the
borings consisted very stifl sligþtly clayey, slightly sandy to sandy silt in all three test borings. Based on the
geotechnical report the soils are assumed to be a sandy silt loam with slightly blocþ and granular structure with
moderate structural grade having an LTAR of 0.60 g/sfld.
A sr¡bsurlncc soil invcstigtrtion ancl sitc asscssmcnt was pcrformccl by Sopris Enginccring in on July 2.0, ?.022.. Thc
soils in the proposed field envelope area were sampled and characterized by application of the USDA visual/tactile
soil texture method analysis from samples in two profile pits. Generally the soils below approximately l8 -24
inches of previously placed fill consist of medium dense silt loam texture soil with slightly blocþ to granular
structure to the profile pit depth of 8 feet. The soils contain less than 5olo scattered gravel or rock content to the 8-
feet depth explored below the surface grades. No free water was encountered in the pit excavatiors. No evidence of
seasonal higþ ground water or redox conditions was observed in the profile pits. Seasonal higþ Groundwater levels
are expected to be below 20 feet from the existing surface grades on the relatively flat terrain.
The west central portion of the lot was previously filled and graded with the placement of approximately 18 -24
inches of clay loam soils. The depth is variable with evidence of this imported fill overþing the previous vegetated
surface and remnants of a topsoil layer. The native soils sampled from the pits, 2-3 feet below the surface, in the
vicinity ofthe proposed field, are characterized as a soil type 2 consisting of silt loam texture with granular structure.
This soil has an effective loading rate for conventional soil treatment of 0.6 Gal/S .F.lday for a level 1 conventional
treatment systenr
Long Term Accentance Rate (LTAR)
Considering the application of the state regulation 43:
Receiving Wastewater Treatment Level I;
LTAR; (Table 10-1 Soil type 2loading ratc for a silt loam is (0.6 gal./S.F./day);
DesignFlow; Qd: flow (gal/day): 525 gpd
Ioading factors; (Table 10-2, Gravity applicationtrenches, L.F.1 : 1.0)
(Table 10-3, Gravelless chambers,L.F.2 : 0.7)
STU absorption treaûnent area; A : Area S.F.;
A(sÐ Od xL.F.1 xL.F.2
LTAR
A(sÐ: 525 æd x 1.0 x 0.7 : 612.5 S.F
0.6 Gal/S.F./t1ay
ÖWTS Nilsson Residence,
167 Slrore Dr, Silt, C0
SE Job No. 32029.01
Noveniber 1,2023
Page3
Nuùer of Quick4 lnfiltnator chãrúers 4'x3kl2"clqr¡ùers:
6t2.5 :5t chauùsrs; Use 52 clnmbers
X2 S-FJCharnber
U$od 52 Quisk4 lnfilhator ct¡ambers ir 4 tremhss 54' lorg by 3' wide wiü l3 chambers units per trench plus two
ed caps as delirrcated on tLe plan to pmvide 4proxirmtely 625 S-F- of absorptive area.
(}ll-S Oneretion end llainteneme
Omæmhip of tln systern and respo'rsibility for rminternnce and repair will remain with the property Owrær. The
$n¡ner is erxouragsd to retain th services of qualified persorrrel to inspect the OWTS and to perforrn all
mnirüenarcs ard repain rncçssary to Eßsure fut thË system conryorrrús are mairúained in good operating condition
ad suitable veçtative çovsr is esøblished ontüs fields. The cornpomnts of the OWTS system should inspected
wittin 30 days of beirrg plased fuÉo operation ard shoutd been inspected and mainf'ained bi-annually. The tank,
absorption field ard otlrr system corrçorcnts should be visually inspccted bi-arurually for debris, damage, leaks, or
dfor potential problenrs- ln gemra[ for a properþ utiliæd syst€rr! septic hnks should be purrped every 3 - Syears.
Th effluent filter should be cleaned every six nnrük ard at tln tinp of pumping Absorption fields should be
nnoir¡taired with suitable vegetative cover and kept firse ofrn¡rt invasive plants. Positive surface drainage away from
fu absorption freld slxruld he nnirûafuFd-
ffi'you have any qrnstion or need ar¡y additional infomntion, please calX-
Simerely,
SOPRIS ENGTNEERING. IIC
Fdut E- Rutledge
DesþEngirner Princþl
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