HomeMy WebLinkAboutDesign Report 09.07.2019ALL
SIRVIfI
33 Four Wheel Drive Rd
Carbondale, CO 81623
970-309-5259
September 7, 2019 Project No. C1355
Roger Giard
rgiard(a7rof.net
Subsurface Investigation and Onsite Wastewater Treatment System Design
7 -Bedroom Residence
Big Mountain Ranch
TBD CR 230
Garfield County, Colorado
Roger,
ALL SERVICE septic, LLC performed a subsurface investigation and completed an onsite wastewater
treatment system (OWTS) design for the subject residence. The 1000+ acre property is located outside
of Rifle, in an area where OWTSs and wells are necessary. The original OWTS design dated February
19, 2018 was installed and inspected. The residence was still under construction. A change to the house
plans includes an additional bedroom. There will be a total of 7 -bedrooms in the residence and therefore
capacity must be added to the system to accommodate the additional bedroom. This design addressed
the necessary addition to the OWTS.
Legal Description: Section: 19 Township: 3 Range: 93 LOTS 1, 2, 3 AND 4, E1/2W1/2, W1/2E1/2,
E1/2NE, SESE. SECTION 30: LOTS 1 & 2, E1/2NW, N1/2NE. TOWNSHIP 3: RANGE 94: SECTION 24:
S1/2SW LYING EAST OF COUNTY ROAD 252, S1/2SE. SECTION 25: E1/2NW LYING EAST OF
COUNTY ROAD 252, N1/2NE, SWNE. ALSO A TR. OF LAND CONT. 27 AC.+/- AS DESCRIBED IN
RECEPTION #555469. EXCEPT A TR. OF LAND CONT. 27 AC.+/- AS DESCRIBED IN RECEPTION #
555470. EXCEPT A TR. OF LAND CONT. 40 AC.+/- AS DESCRIBED IN RECEPTION # 610789.
PARCEL CAN NOT BE SOLD SEPARATELY FROM SIBLING ACCOUNT 1877-253-00-032.
Parcel ID: 1877-251-00-029
SITE CONDITIONS
A 7 -bedroom, single-family residence is presently under construction.
There is a private well located north of the residence greater than 50 -feet from the proposed septic tank
and greater than 100 -feet from the proposed soil treatment area (STA).
The proposed STA location has an approximate 15% slope to the southwest. The proposed area is
covered with native grasses.
SUBSURFACE
The subsurface was investigated on January 24, 2018 by digging two soil profile test pit excavations (Test
Pits). A visual and tactile soil analysis was completed by Carla Ostberg at the time of excavation.'
' Carla Ostberg holds a Certificate of Attendance and Examination from the CPOW Visual and Tactile
Evaluation of Soils Training.
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The materials encountered in the Test Pit #1 consisted of dark brown clay loam with moderate structure
grade and some cobbles to 6 -feet, underlain by medium to light brown clay loam with weak structure
grade to a maximum depth explored of 8.0 -feet. No bedrock or groundwater was encountered.
The materials encountered in the Test Pit #2 consisted of dark brown clay loam with moderate structure
grade and some cobbles to 4 -feet, underlain by medium to light brown clay loam with weak structure
grade to a maximum depth explored of 8.0 -feet. No bedrock or groundwater was encountered.
A tactile analysis of the soils was taken from Test Pit #1 at 3 -feet below grade. The soil formed a ball
and a ribbon approximately 1 to 2 -inches in diameter before breaking. The texture of the soil was both
gritty and smooth. Soil structure shape was blocky, soil structure grade was moderate, and consistence
was firm. Structure grade of the soil below 6 -feet in Test Pit #1 and below 4 -feet in Test Pit #2 was weak.
STA sizing is based on Soil Type 3A, Clay Loam with weak structure grade. A long term acceptance
rate (LTAR) of 0.3 gallons per square foot will be used to design the OWTS, in accordance with
Table 10-1 Soil Type 3A presented in the Garfield County On -Site Wastewater Treatment System
Regulations, adopted April 14, 2014.
Weak Structure Grade below 6 -feet
Sieved sample
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Weak structure grade begins at 4 -feet in Test Pit #2 Backfill
DESIGN SPECIFICATIONS
Design Calculations:
Average Design Flow = 75 GPD x 2 people/bedroom x 3 Bedrooms + 300 GPD (4th -7th bedrooms) = 750
GPD
LTAR = 0.3 GPD/SF
750 GPD / 0.3 GPD/SF x 0.8 (pressure dosed trenches) x 0.7 (chambers) = 1400 SF
The OWTS design is based on 7 -bedrooms. An average daily wastewater flow of 750 GPD will be used.
A 4 -inch diameter SDR -35 sewer pipe with a double -sweep cleanout will be installed with a minimum 2%
fall from the house to the septic tank.
The system installation will include a 2000 -gallon, two-compartment Valley Precast concrete septic tank
followed by a 500 -gallon, concrete pump chamber with an Orenco® ProPak pumping system and
PF3005 pump. The floats must be set to dose approximately 80 gallons each pump cycle.
Risers must be installed on the septic tank manholes to bring access to grade. Handle extensions on
both the effluent filter and float tree must be installed if the riser height exceeds 1 -foot. The control
panel must be located within line of sight of the septic tank. We recommend Valley Precast out of
Buena Vista perform start up on the pumping system.
A 1.5 -inch diameter Schedule 40 pump line must be installed from the pump to an Orenco® automatic
distributing valve (ADV), model 6606. 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 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.
Effluent will be pressure dosed through 1.5 -inch diameter pipes to six trenches, each with 20 `Quick 4'
Low Profile Infiltrator® chambers, for a total of 120 chambers and 1440 square feet of infiltrative
area. There must be at least 6 -feet of undisturbed soil between each trench. Shallow installation
(between 1 and 3 -feet below grade) will allow the infiltrative area to be placed in the more moderate
structure grade of the soil.
Effluent will be pressure dosed to 1.5 -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 drilled 3 -feet on center. Each lateral must end in a 90
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degree ell facing up with a ball valve for flushing. Valves may be placed in a valve box, accessible from
grade, for access. Inspection 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.
The component manufacturers are typical of applications used by contractors and engineers in this area.
Alternatives may be considered or recommended by contacting our office. 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.
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 irritation 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 backfilled STAs. 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.
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 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.
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INSTALLATION OBSERVATIONS
ALL SERVICE septic, LLC 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. ALL SERVICE septic,
LLC should be notified 48 hours in advance to observe the installation.
LIMITS:
The design is based on information submitted. If soil conditions encountered are different from conditions
described in report, ALL SERVICE septic, LLC 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,
ALL SERVICE septic, LLC
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Carla Ostberg, MPH, REHS
Reviewed By:
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