HomeMy WebLinkAboutEngineer's As-built Report 10.18.2018October 18, 2018
Wirkler, Norman E & Margaret & Chris
PO Box 1030
Carbondale, CO, 81623
nwirkler@yahoo.com
RE: AS -BUILT, Onsite Wastewater Treatment System (OWTS), Wirkler Residence, 9663 State
Highway 82, Garfield County, Colorado
SE Job No. 18020.01 Parcel Number: 2393-202-00-111
Garfield County Septic permit # SEPT -04-18-5184
Dear Norm:
Pursuant to County requirements, this letter provides documentation that the new Onsite Wastewater
Treatment Systems (OWTS) 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 at various times during construction, prior to final backfill and after all installations
was completed. The system constructed on site was designed and built to serve the existing residential
structure with a combined total dwelling space of approximately 3000 S.F. The basis of design is for a
3 -bedroom residence with the potential addition of future bedrooms and ability to upgrade the system to
serve another single family dwelling.
Sopris Engineering performed site visits to inspect and document the as -built conditions of the constructed
system. Inspections were coordinated with the earthmoving contractor, Great Lakes Construction. The as -
built conditions and installation of the upgraded and new OWTS components is in compliance with
Garfield County Regulations; the recommendations and specifications delineated on the civil C 1 OWTS
plan & profile and the C2-OWTS-DETAILS drawing dated 4-9-2018, by Sopris Engineering. The design
criteria and system sizing information is summarized below. An As -built OWTS record drawing is
attached delineating the As -built descriptions and locations of the components.
Design Criteria and As -built System Component Installation
The system was designed based on the design criteria approved for use of Soil Treatment Unit (STU)
systems. The existing OWTS was upgraded with a replacement absorption field, sewage pump station and
new septic tank designed based on the design flow for a 3 -bedroom residential capacity with expansion
potential.
The existing 1250 gallon single compartment concrete septic tank was converted to a sewage pump station
that pumps raw sewage to the new septic tank. The existing tank was cleaned prepared for the placement of
a new manhole access riser with ladder steps consisting of a 4' diameter concrete barrel section and an
eccentric 4' diameter by 2' depth conic section with iron ring and cover at the surface. A'h HP sewage
(solids handling) pump was installed in the tank with associated discharge/control components.
Approximately 100' of 2" schedule 40 PVC pressure transport pipe was installed from the pump station to
a new 1500 gallon 2 -compartment reinforced plastic septic tank installed east of the existing house and out
502 Main Street • Suite A3 • Carbondale, CO 81623 • (970) 704-0311 • Fax (970) 704-0313
SOPRIS ENGINEERING • LLC
civil consultants
AS -BUILT, OWTS
Wirkler Residence
SE Job No. 18020.01
October 18, 2018
buidings. This 2" pipe was installed at an approximate 2.5% slope to allow for drainback of effluent to the
pump station tank. The soil treatment unit (STU), consists of 3 leaching chamber trenches that provide
650 S.F. of total absorption area. The septic tank effluent is equally distributed by gravity, via a
distribution box, to the STU. The new concrete distribution box was installed with risers and lid at the
surface and individual distribution pipes connected to the head end cap of each chamber trench.
Observation ports with caps were installed on each end chamber unit. 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).
Sub Surface Conditions and observation
Subsurface soil investigations and USDA soil texture method tests were performed by Sopris Engineering.
The soils in the area of the proposed absorption field were sampled and characterized by application of the
USDA soil texture method analysis. The soils were tested to determine the hydraulic loading rate and the
appropriate absorptive surface depth in the native soils. The soils below 6 to 8 inches of topsoil consist of
medium dense silt loam with moderate blocky to granular structure overlying deep cobbles and gravel in a
sandy clay loam matrix to the 7 foot depth explored. These soils appear to consist of glacial outwash
materials consisting of sand, silt, clay, gravels, cobbles and small boulders.
The native soils sampled from 1-2 feet below the surface are characterized as a soil type 2 consisting of silt
loam texture with moderate blocky to granular structure. This soil has an effective loading rate for
conventional soil treatment of 0.60 gal/S.F./day for a level 1 conventional treatment system. The equivalent
percolation rate is approximately 16-25 minutes per inch. Increased quantities of cobbles and gravel are
encountered at depths below 5 feet. Groundwater levels are expected to be well below 10 feet below the
existing surface grades. The soils were found suitable for a conventional shallow absorption field
consisting of gravelless infiltration chamber units. No free water was encountered in excavations on site.
No excessive boulders or cobbles were encountered during excavation. Observations of the soils, in the
excavation during construction, appeared to be consistent with the previous subsurface soil investigation.
Design Flow
The design flow is calculated as follows:
From the Garfield County OWTS Regulation 43 ;
Minimum population based on 3 bedrooms @ 2 person /bedroom = 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 & Pump Station Installaion
A 1500 gallon 2 -compartment reinforced plastic septic tank was installed with sealed HDPE risers and lids
installed at the surface. The tank was installed with inlet and outlet sanitary tees. The existing septic tank
was upgraded to serve as a raw sewage pump station to lift sewage to the new septic tank. The sewage
pump is a Grunflos model PFSW5011, 1/2 HP, 115V, 2" Solids Handling Pump,
AS -BUILT, OWTS
Wirkler Residence
SE Job No. 18020.01
October 18, 2018
installed with a 2" Hose & Valve Assembly with quick disconnect and float tree assembly. The pump
station is controlled by an Orenco Systems, model 5 1ETMCT Simplex Panel, installed in line of site on the
exterior wall near the northeast corner of the house.
Treatment -Soil Treatment Unit/ Absorption System Design
The treatment/absorption field was designed based on utilizing the effective Long Term Acceptance Rate
(LTAR) for the native soils and the application of appropriate loading factors for a soil treatment unit
system utilizing gravity distribution to gravelless chamber trenches. The new treatment system and
absorption field consist of gravity distribution of septic tank effluent via a distribution box to individual
chamber trenches with treatment across the native soil absorptive surface.
Long Term Acceptance Rate (LTAR)
Considering the application of the new state regulation 43:
Receiving Wastewater Treatment Level 1; loading rate for silt loam is (0.60 gal./S.F./day) for soil type
2A.; Loading factors; (Table 10-2, Gravity application trenches = 1.0) and
(Table 10-3, gravelless chambers = 0.7)
A(sf) = Qd x L.F.: A = Area;
LTAR LTAR = 0.50 Gal/S.F./day for silt loam
Qd = flow (gal/day) = 450 gpd
L.F.1=1.0 Gravity Distribution
L.F.2=0.7 Chambers
A(sf) = 450 gpd x 1.0 x 0.7 = 525 S.F.
0.60 Gal/S.F./day
Number of quick -4 chambers:
525S.F = 44 chambers Use 54 chambers
12 S.F./Chamber
54 chambers x 12 S.F./chamber provides 648 S.F. of absorption/treatment area that equates to a Design
Capacity of 555 gpd suitable for an additional bedroom on the existing residence or to be used as partial
capacity for a future dwelling up to a 3 bedroom capacity with the addition of 2 additional trenches and
tank.
54 Quick -4 chambers were installed in three shallow trenches 74' long by 3' wide with 18 chambers units
per trench plus two end caps as delineated on the AB Record drawing plan. The septic tank effluent is
gravity distributed to the head of each chamber row via individual distribution pipes from the distribution
box.
AS -BUILT, OWTS
Wirkler Residence
SE Job No. 18020.01
October 18, 2018
OWS Operation and Maintenance
Ownership of the system and responsibility for maintenance and repair will remain with the property
Owner. The Owner is encouraged to retain the services of qualified personnel to inspect the OWTS and to
perform all maintenance and repairs necessary to ensure that the system components are maintained in
good operating condition and suitable vegetative cover is established on the fields. The components of the
OWTS system were inspected by the engineer within 30 days of being placed into operation and should
been inspected and maintained bi-annually. The tank, absorption field and other system components
should be visually inspected bi-annually for debris, damage, leaks, or other potential problems. In general,
for a properly utilized system, septic tanks should be pumped every 3 - 5years. The effluent filter should
be cleaned every six months and at the time of pumping. Absorption fields should be maintained with
suitable vegetative cover and kept free of root invasive plants. Positive surface drainage away from the
absorption field should be maintained.
If you have any question or need any additional information, please call.
Sincerely,
SOPRIS ENGINEERING, LLC
Paul E. Rutledge
Design Engineer
Yancy Nichol, PE
Principal