HomeMy WebLinkAboutOWTS Installation ObservationCBO Inc.
129 Cains Lane
Carbondale, CO 81623
970.309.5259
carla.ostberg@gmail.com
November 17, 2025 Project No. C1927
Caet May
caetm@redroom-design.com
Onsite Wastewater Treatment System (OWTS) Installation Observations
11749 CR 311
Garfield County, Colorado
Permit SEPT-9070
Caet,
CBO Inc. observed the installation of the onsite wastewater treatment system (OWTS) on August 28,
2025 for the subject property. High Country Building installed the system.
The OWTS design is based on 2-bedrooms. An average daily wastewater flow of 300 GPD was used.
The well and cistern, which were not included in our original plans, have been identified on the site plan
and setbacks verified.
The 4-inch SDR-35 sewer line exiting the residence had a double-sweep clean out and a minimum 2%
grade to the septic tank.
The system installation included a 1000-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 are set to dose 54 gallons each pump cycle. The control panel for the pump is
located within line of sight of the septic tank. Valley Precast out of Buena Vista performed start-up of the
pumping system.
Effluent is pumped through a 1.5-inch diameter pump line from the pump chamber to an Orenco®
automatic distributing valve (ADV), model 6402. The ADV was placed at a high point in the system in an
insulated riser with access from grade.
Effluent is pressure dosed to through 1.5-inch diameter distribution lines to a 13’ x 42’ bed. The depth of
the excavation does not exceed 4-feet below native grade. A minimum of 2-feet of sand filter material
was installed in the over-excavated footprint. A gradation of the sand media is enclosed.
A 30 mil PVC liner was placed on the uphill side of the excavation for the sand filter. The liner extends
from the top to the bottom of the sand filter on the north (uphill side) of the sand filter to provide protection
from any upgradient drainage.
Laterals are 1.5-inches in diameter with 5/32-inch diameter orifices facing down, spaced 3-feet on center,
installed on the GeoMat™ with the filter fabric over the laterals. Laterals are placed 2-feet from the edges of
the bed with 3.0-feet between the laterals. Laterals are connected with 1.5-inch diameter level manifolds.
Four 39” wide GeoMat™ sheets were placed on the 13-foot wide bed.
Each 1.5-inch diameter lateral ends in a sweeping ell facing up with a ball valve for flushing. Valves were
placed in a 10-inch sprinkler box for access. Inspection ports were placed at each corner of the bed.
Ports may be cut to grade and covered with a valve box for access.
The OWTS was generally installed according to specifications. This observation is not a guarantee of
workmanship and/or parts and materials. CBO Inc. should be notified if changes are made to the OWTS
in the future. Any additional OWTS construction must be according to the county regulations.
LIMITS: Observations are limited to components that are visible at the time of the inspection. The installer must
have documented and demonstrated knowledge of the requirements and regulations of the county in
which they are working. The quality of the installation is dependent on the expertise of the installer, soil
type, and weather conditions.
Please call with questions.
Sincerely,
CBO Inc.
Carla Ostberg, MPH, REHS
Sewer line out of house, clean out under deck
Septic tank Pump in second compartment
Inlet tee Distribution lines to manifolds
ADV
STA Water cistern on east side of house
Control panel Well setback verified
10/10/2025
To Whom It May Concern:
We have been to the following site:
11749 CR 311, Silt, Garfield County
We have verified that the system was started properly. The System went
through several cycles with no issues.
- Amperage and voltage of control panel, floats, and pump are all within
manufacturers specifications and tolerance at start up.
- Floats verified for functionality.
- The high-level alarm functions upon activation at control panel.
If you have any questions, please do not hesitate to call me at 719-395-6764,
ext. 13.
Sincerely,
Scott McIntosh
Service Manager
832‐R‐13‐002