HomeMy WebLinkAboutEngineer's OWTS Design Plan
________________________________________________________________________________________________________
826 ½ Grand Avenue, Glenwood Springs, CO 81601
P: 970.945.5544 F: 970.945.5558 www.mountaincross-eng.com
April 7, 2026
Tekton Consulting, LLC
787 River Bend Way
Glenwood Springs, CO 81601
c/o Mr. Kurt Peterson
RE: Mountain Springs Ranch, Lot 29, Garfield County, CO – OWTS Report
Dear Mr. Peterson:
The purpose of this correspondence is to inform you about the onsite wastewater treatment system
(OWTS) designed for the residence proposed at Mountain Springs Ranch, Lot 29.
The residence will drain by gravity to a conventional septic tank where a pump will pressure dose
to a leach field comprised of a sand filter bed. There is no lower/basement level proposed. If a
basement is constructed in the future, it will need a sewer ejector to pump into the OWTS. The
residence will be served from an existing well. The OWTS is not within a 100-year flood plain
boundary. There are practical constraints that you should be aware of when considering the proper
design, construction, and operation.
Subsurface
The soil was determined to be rocky soils; as reported by Kumar and Associates, though no soils
analysis was performed. USDA soil mapping yields rocky, sandy clay loam. This corresponds to
a long-term acceptance rate (LTAR) approximated as 0.30 gallons per day per square foot
(GPD/sq.ft.). Two profile holes will need to be excavated and an inspection performed to verify
that the OWTS location has similar soils and that that no bedrock nor groundwater is within an 8’
depth of the leaching area. A copy of the soils report is attached.
Design Calculations
The residence is proposed to be 3 bedrooms. Using Garfield County Table 6-1 for a 3-bedroom
residence, this yields 450 gallons per day (GPD) total. The design calculations for sizing of the
septic system and the leach field follow:
• Residence: 3 bedrooms = 450 GPD
• Based on USDA soil mapping, LTAR = 0.30 GPD/sq.ft. (to be verified)
• Minimum absorption area = 450 GPD / 0.30 = 1,500 sq. ft.
• No reductions are allowed for rocky soils.
• Required septic tank volume = 1,000 gallons per Garfield County Table 9-1
• Dosing frequency = 4 doses per day; dose volume = 450 GPD / 4 doses = 113 gal./dose
• Pump(s) should provide 30 gpm at 10’ of Total Dynamic Head
• 2” PVC lateral supply and 1-1/2” distribution pipes should be Schedule 40.
• Each lateral pipe should have sixteen 1/8” diameter holes drilled in the lateral at 4’ spacing
with the first hole located at 30” from the start of the bed.
MSR Lot 29
April, 2026
Page 2 of 3
Mountain Cross Engineering, Inc.
Civil and Environmental Consulting and Design
826 ½ Grand Avenue, Glenwood Springs, CO 81601
P: 970.945.5544 F: 970.945.5558 www.mountaincross-eng.com
The components manufacturers are typical for the area. Alternatives may be considered by
contacting this office. Construction must be in accordance with the specifications of Garfield
County Environmental Health, the OWTS permit, and this design.
Topsoil should be placed over the OWTS and planted with native grasses. No large vegetation
and/or plants with taproots should be planted over the absorption area nor grasses that require
excessive irrigation. Calculations are attached.
Setbacks
The location for the septic and dosing tanks are limited by setback requirements per Garfield
County and the State of Colorado. These include:
• 50’ FROM WELL
• 10’ FROM WATER SUPPLY LINE
• 5’ FROM BUILDING WITH BASEMENT
• 10’ FROM PROPERTY LINE
• 10’ FROM LINED POND, DITCH, OR STREAM
• 50’ FROM WATER BODY
• 10’ FROM CREST OF BANK
• 5’ FROM LEACH FIELD
The leach field setback requirements are:
• 100’ FROM WELL
• 25’ FROM WATER SUPPLY LINE
• 20’ FROM BUILDING WITH BASEMENT
• 10’ FROM PROPERTY LINE
• 10’ FROM LINED POND, DITCH, OR STREAM
• 50’ FROM WATER BODY
• 25’ FROM CREST OF BANK
• 5’ FROM SEPTIC TANK
The setback requirements deal primarily with buildings and potential contamination from the
septic tank, dosing tank, and leach field to either culinary water or surface water. These setbacks
have been included on the plans for reference.
Operation Information and Maintenance
The Owner will need to be responsible for the operation and management of the OWTS. Geo-
fabrics or plastics should not be used over the absorption area. No heavy equipment, parking of
machinery, or materials should be placed on the absorption area. Livestock should not graze on
the absorption area. Plumbing fixtures should be checked to ensure that no additional water is
being discharged to OWTS; for example, running toilets or leaky faucets can discharge hundreds
of gallons of water a day and harm the absorption area.
DOSING DESIGN CALCULATIONS, for
Mountain Springs Ranch Lot 29, Garfield County, CO
4/7/2026
Step 1: Flows
3 Bedrooms Table 6-1
0 Bedroom (future)
6 assumed people Septic Tank Size:
450 gallons per day 1000 gallons per Table9-1
0.5 average day in gallons per minute
4 doses per day 0.94 peak day in gallons per minute
113 gallons per dose 1.88 peak hour in gallons per minute
Step 2: BOD5
6 persons
450 gpd used by residence
BOD5 for domestic uses:
0.2 lb/person/day from CDPHE 1.2 lb BOD5/day
Step 3: Dosing Basin
Third Compartment of Septic Tank
60 inch length
40.5 inch width
16.88 square feet 126.2 gallons per foot of depth
depth of dose volume =0.89 feet of depth in manhole
Invert at dosing tank 8133.20
Sump = bottom of third compartment 8129.12
Pump "Off"1 8130.12
Pump On "Lead" Float 1.89 8131.01
Pump On "Lag" Float 2.39 8131.51
High Alarm (min)2.89 8132.01
High Alarm (max) in -12" 1.00 8132.20
minutes of run time per dose = 3.8 30 gpm
(5 minute rule of thumb)
Step 4: Elevations, Orifices, and Head loss
Septic Tank Rim Elevation =8136.5
High Point Elevation =8113
Invert at dosing tank= 8133.2
Sump =8129.12
Elev Diff =-16.1 feet Design analysis for only one of leaching areas
Length from pump to leach field of 2" =95 feet
Length of 1-1/2" in leach field =260 feet
2" fittings in equivalent pipe length:
check 90 90 check 90 gate tee 4-45 check 2 - tee
17.2 5.2 5.2 17.2 5.2 1.4 10.3 11.2 17.2 20.6 110.7 feet
Equivalent 2" Length from pump =189.6 feet
from Fig F, using 1.81 ft of friction head per 100' of 2" plastic pipe = 3.4 head loss @ 30 gpm
from Fig F, using 0.5 ft of friction head per 100' of 1-1/2" plastic pipe = 1.3 head loss @ 7.5 gpm
Dynamic Head (TDH)-11.4 system condition use TDH of 10 feet
1/8 " dia. orifice @ 5' of Head yields 0.45 gpm
4 Laterals 16 orifices per lateral 28.8 gpm
Step 5: Velocity verification
30 gpm in 2 inch pipe
0.022 = area
0.067 = flow in cfs
3.064 = velocity in feet per second, must be greater than 2.0 feet per second
but less than 10 feet per second
7.5 gpm in 1.5 inch pipe
0.012 = area
0.017 = flow in cfs
1.362 = velocity in feet per second
Step 6: Pipe Volume & Drain Back
no drain back
Pump Selection for a Pressurized System - Single Family Residence Project
Parameters
Discharge Assembly Size
Transport Length
Transport Pipe Class
Transport Line Size
Distributing Valve Model
Max Elevation Lift
Manifold Length
Manifold Pipe Class
Manifold Pipe Size
Number of Laterals per Cell
Lateral Length
Lateral Pipe Class
Lateral Pipe Size
Orifice Size
Orifice Spacing
Residual Head
Flow Meter
'Add-on' Friction Losses
2.00
95
40
2.00
None
5
12
40
1.50
4
62
40
1.50
1/8
4
5
None
0
inches
feet
inches
feet
feet
inches
feet
inches
inches
feet
feet
inches
feet
Calculations
Minimum Flow Rate per Orifice
Number of Orifices per Zone
Total Flow Rate per Zone
Number of Laterals per Zone
% Flow Differential 1st/Last Orifice
Transport Velocity
0.43
64
27.7
4
0.7
2.7
gpm
gpm
%
fps
Frictional Head Losses
Loss through Discharge
Loss in Transport
Loss through Valve
Loss in Manifold
Loss in Laterals
Loss through Flowmeter
'Add-on' Friction Losses
1.5
1.3
0.0
0.2
0.1
0.0
0.0
feet
feet
feet
feet
feet
feet
feet
Pipe Volumes
Vol of Transport Line
Vol of Manifold
Vol of Laterals per Zone
Total Volume
16.6
1.3
26.2
44.1
gals
gals
gals
gals
Minimum Pump Requirements
Design Flow Rate
Total Dynamic Head
27.7
13.1
gpm
feet
0 10203040506070
0
5
10
15
20
25
30
35
Net Discharge (gpm)
PumpData
PKP350 Effluent Pump
1/2HP, 115V 1Ø
Legend
System Curve:
Pump Curve:
Pump Optimal Range:
Operating Point:
Design Point:
U.S. Environmental Protection Agency
TM
Do your Part—
Be SepticSmart!
A Homeowners’Guide
to Septic Systems
A Homeowners’ Guide to Septic Systems | www.epa.gov/septicsmart 2
Maintaining Your
Septic System:
Good for your wallet. Good for your health.
Good for the environment.
Did you know that one-quarter of all U.S. homes have septic systems? Yours may be
one of them. If you’re not properly maintaining your septic system, you’re not only
hurting the environment, you’re putting your family’s health at risk—and may be
flushing thousands of dollars down the drain!
First Things First:
What Is a Septic System?
Common in rural areas without centralized sewer systems, septic systems are
underground wastewater treatment structures that use a combination of nature
and time-tested technology to treat wastewater from household plumbing produced
by bathrooms, kitchen drains, and laundry.
Do You Have a Septic System?
You may already know you have a septic system. If you don’t know, here are tell-tale
signs that you probably do:
• You use well water.
• The waterline coming into your home doesn’t have a meter.
• You show a “$0.00 Sewer Amount Charged” on your water bill.
• Your neighbors have a septic system.
A Homeowners’ Guide to Septic Systems | www.epa.gov/septicsmart 3
How To Find Your Septic System
Once you’ve determined that you have a septic system, you can find it by:
• Looking on your home’s “as built” drawing.
• Checking your yard for lids and manhole covers.
• Contacting a septic inspector/pumper to help you locate it.
Why Should You Maintain Your Septic System?
Maintaining Your Septic System…
Saves You Money
Regular maintenance fees of $250 to $300 every three to four years is a bargain
compared to the cost of repairing or replacing a malfunctioning system, which can
cost between $3,000 and $7,000. The frequency of pumping required for your system
depends on how many people live in your home and the size of the system.
Protects Your Property Value
An unusable septic system or one in disrepair will lower your property value, not to
mention pose a potentially costly legal liability.
Keeps You and Your Neighbors Healthy
Household wastewater is loaded with disease-causing bacteria and viruses, as well
as high levels of nitrogen and phosphorus. If a septic system is well-maintained and
working properly, it will remove most of these pollutants. Insufficiently treated sewage
from septic systems can cause groundwater contamination, which can spread disease
in humans and animals.
Improperly treated sewage also poses the risk of contaminating nearby surface waters,
significantly increasing the chance of swimmers contracting a variety of infectious
diseases, from eye and ear infections to acute gastrointestinal illness and hepatitis.
Service provider coming? Here’s what you need to know.
When you call a septic service provider, he or she will inspect for leaks and examine the scum and sludge
layers in your septic tank.
Your septic tank includes a T-shaped outlet which prevents sludge and scum from leaving the tank and
traveling to the drainfield area. If the bottom of the scum layer is within six inches of the bottom of the
outlet, or if the top of the sludge layer is within 12 inches of the outlet, your tank will need to be pumped.
Remember to note the sludge and scum levels determined by the septic professional in your operation
and maintenance records, as this will help determine how often pumping is necessary.
The service provider should note any repairs completed and the tank condition in your system’s service
report. If additional repairs are recommended, be sure to hire someone to make them as soon as possible.
The National Onsite Wastewater Recycling Association (NOWRA) website has a septic locator that
makes it easy to service professionals in your area. Visit www.septiclocator.com and enter your ZIP
code to get started!
A Homeowners’ Guide to Septic Systems | www.epa.gov/septicsmart 4
Protects the Environment
More than four billion gallons of wastewater is dispersed below the ground’s
surface every day. That’s a lot of water! Groundwater contaminated by poorly or
untreated household wastewater doesn’t just pose dangers to drinking water—it
poses dangers to the environment. Malfunctioning septic systems release bacteria,
viruses, and chemicals toxic to local waterways. When these pollutants are released
into the ground, they eventually enter streams, rivers, lakes, and more, harming local
ecosystems by killing native plants, fish, and shellfish.
Maintaining Your Septic System:
The Basics
Septic system maintenance isn’t complicated, and it doesn’t need to be expensive.
Upkeep comes down to four important elements:
• Inspection and pumping
• Water efficiency
• Proper waste disposal
• Drainfield care
Inspect and pump frequently
The average household septic system should be inspected at least every three years
by a septic service professional. Household septic tanks are typically pumped every
three to five years. Alternative systems with electrical float switches, pumps, or
mechanical components need to be inspected more often, generally once a year.
A service contract is important since alternative systems have mechanized parts.
Four major factors influence the frequency of septic pumping:
• Household size
• Total wastewater generated
• Volume of solids in wastewater
• Septic tank size
Beware of septic tank additives!
Some makers of septic tank additives claim their products break down septic tank sludge in order to
eliminate the need for pumping. But the effectiveness of additives has not been determined; in fact,
many studies show that additives have no significant effects on a tank’s bacterial populations.
Septic tanks already contain the microbes they need for the effective breakdown of household
wastewater pollutants. Periodic pumping is the only true way to ensure that septic systems work
properly and provide many years of service.
A Homeowners’ Guide to Septic Systems | www.epa.gov/septicsmart 5
Use water efficiently
Did you know that average indoor water use in a typical single-family home is nearly
70 gallons per individual, per day? And just a single leaky toilet can waste as much
as 200 gallons of water per day?
All of the water a household sends down its pipes winds up in its septic system.
This means that the more water a household conserves, the less water enters the
septic system. Efficient water use can not only improve the operation of a septic
system, but it can reduce the risk of failure as well. Learn more about simple ways
to save water and water-efficient products by visiting EPA’s WaterSense Program
at www.epa.gov/watersense.
• High-efficiency toilets: Toilet use accounts for 25 to 30 percent of household
water use. Most older homes have toilets with 3.5- to 5-gallon reservoirs,
while newer, high-efficiency toilets use 1.6 gallons of water or less per flush.
Replacing existing toilets with high-efficiency models is an easy way to quickly
reduce the amount of household water entering your septic system.
• Faucet aerators and high-efficiency showerheads: Faucet aerators help
reduce water use as well as the volume of water entering your septic system.
High-efficiency showerheads or shower flow restrictors also reduce water use.
• Washing machines: Washing small loads of laundry on your washing machine’s
large-load cycle wastes water and energy. By selecting the proper load size,
you’ll reduce water waste. If you’re unable to select a load size, run only full
loads of laundry.
Another tip? Try to spread water use via washing machine throughout the week.
Doing all household laundry in one day might seem like a time-saver, but it can
be harmful to your septic system, as it doesn’t allow your septic tank time to
adequately treat waste and could potentially flood your drainfield.
Consider purchasing an ENERGY STAR® clothes washer, which uses 35 percent
less energy and a whopping 50 percent less water than a standard model.
Learn more about ENERGY STAR appliances by visiting www.energystar.gov.
Small leaks can lead to big problems!
When it comes to water fixtures, a couple of quick fixes can save you serious problems down the road!
Check to see if your toilet’s reservoir is leaking into your toilet bowl by adding five drops
of liquid food coloring to the toilet reservoir before bed. If the dye is in the toilet bowl the
next morning, the reservoir is leaking and repairs are needed.
Think a leaky faucet is no big deal? Think again. A small drip from a faucet adds gallons
of unnecessary water to your septic system every day.
To see how much a leak adds to your water usage, place a cup under the drip for 10 minutes.
Multiply the amount of water in the cup by 144 (the number of minutes in 24 hours, divided by 10).
Just one cup of leaky faucet water every 10 minutes equals 36 wasted gallons of water a day—
and they all end up in your septic system.
New faucets and toilet reservoirs are easily accessible and inexpensive. Choose to make a small
investment for a big difference in your septic system.
A Homeowners’ Guide to Septic Systems | www.epa.gov/septicsmart 6
• Proper waste disposal: Whether you flush it down the toilet, grind it in the
garbage disposal, or pour it down the sink, shower, or bath, everything that goes
down your drains ends up in your septic system. And what goes down the drain
can have a major impact on how well your septic system works.
Toilets Aren’t Trash Cans!
Your septic system is not a trash can. An easy rule of thumb? Don’t flush anything
besides human waste and toilet paper.
Never flush:
• Feminine hygiene products
• Condoms
• Dental floss
• Diapers
• Cigarette butts
• Coffee grounds
• Cat litter
• Household chemicals like gasoline, oil, pesticides, antifreeze, and paint
• Pharmaceuticals
For a complete list, visit water.epa.gov/septicsmart.
1
2
3
4
How does a septic system work?
This is a simplified overview of how a septic system works.
All water runs out of your house from one main drainage pipe into a septic tank.
The septic tank is a buried, water-tight container usually
made of concrete, fiberglass or polyethylene.
Its job is to hold the wastewater long enough to
allow solids to settle down to the bottom
(forming sludge), while the oil and grease
floats to the top (as scum). Compartments
and a T-shaped outlet prevent the
sludge and scum from leaving the tank
and traveling into the drainfield area.
The liquid wastewater then exits the
tank into the drainfield. If the drainfield
is overloaded with too much liquid,
it will flood, causing sewage to flow to
the ground surface or create backups
in toilets and sinks.
Finally, the wastewater percolates
into the soil, naturally removing harmful
bacteria, viruses, and nutrients.
Groundwater
Soil
Drainfield Soil
PipeSeptic Tank 12
3
4
Groundwater
Well
A Homeowners’ Guide to Septic Systems | www.epa.gov/septicsmart 7
Take care at the drain
Your septic system contains a collection of living organisms that digest and treat
household waste. Pouring toxins down your drain can kill these organisms and harm
your septic system. Whether you’re at the kitchen sink, bathtub, or utility sink:
• Avoid chemical drain openers for a clogged drain. Instead,
use boiling water or a drain snake.
• Never pour cooking oil or grease down the drain!
• Never pour oil-based paints, solvents, or large volumes of toxic cleaners
down the drain. Even latex paint waste should be minimized.
• Eliminate or limit the use of a garbage disposal, which will significantly
reduce the amount of fats, grease, and solids that enter your septic tank
and ultimately clog its drainfield.
Maintain your drainfield
Your drainfield—a component of your septic system that removes contaminants from
the liquid that emerges from your septic tank—is an important part of your septic
system. Here are a few things you should do to maintain it:
• Never park or drive on your drainfield.
• Plant trees the appropriate distance from your drainfield to keep
roots from growing into your septic system. A septic service
professional can advise you of the proper distance, depending on
your septic tank and landscape.
• Keep roof drains, sump pumps, and other rainwater drainage
systems away from your drainfield area, as excess water slows
down or stops the wastewater treatment process.
Own an RV, boat or mobile home?
If you spend any time in a recreational vehicle (RV) or boat, you probably know of the problem of
odors from sewage holding tanks. Learn more about proper and safe wastewater disposal—download
EPA’s factsheet at www.epa.gov/region9/water/groundwater/uic-pdfs/rv-wastewater.pdf or
call The National Small Flows Clearinghouse’s Septic System Care hotline toll-free at 1-800-624-8301.
A Homeowners’ Guide to Septic Systems | www.epa.gov/septicsmart 8
Failure Causes
Pouring household and home improvement chemicals down your drains, flushing
garbage down toilets, excessive water use, and failure to provide proper maintenance
aren’t the only culprits for septic system failure. Take note of these additional causes
of septic failure:
Hot tubs
Hot tubs may be a great way to relax, but when it comes to emptying them, your
septic system should avoided. Emptying a hot tub into your septic system stirs the
solids in the tank, pushing them into the drainfield, causing it to clog and fail.
Drain cooled hot tub water onto turf or landscaped areas far away from your
septic tank and drainfield, and in accordance with local regulations. Use the
same caution when draining swimming pools.
Water purification and softening systems
Some freshwater purification systems, including water softeners,
unnecessarily pump water into septic systems. Such systems can
send hundreds of gallons of water to septic tanks, causing agitation
of solids and excess flow to drainfields. When researching water
purification and softening systems, check with a licensed plumbing
professional about alternative routing for such treatment systems.
Garbage disposals
Consider eliminating or limit the use of garbage disposals. While convenient,
frequent use of garbage disposals significantly increases the accumulation of sludge
and scum in septic tanks, resulting in the need for more frequent pumping.
Improper design or installation
The proper design and installation of a septic system is essential for it to
correctly function. A home’s groundwater table, soil composition, and a properly
leveled drainfield are just a few factors to ensure a well-functioning septic system.
Be sure to do your research when hiring septic professionals.
Failure symptoms: Mind the signs!
A foul odor isn’t always the first sign of a malfunctioning septic system. Call a septic professional
if you notice any of the following:
• Wastewater backing up into household drains.
• Bright green, spongy grass on the drainfield, even during dry weather.
• Pooling water or muddy soil around your septic system or in your basement.
• A strong odor around the septic tank and drainfield.
Mind the signs of a failing system. One call to a septic professional could save you thousands of dollars!
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U.S. Environmental Protection Agency
TM
For more information on how you can
be SepticSmart, please visit:
www.epa.gov/septicsmart
EPA-832-B-12-005
September 2012
For more information about
septic systems, contact:
U.S. Environmental Protection Agency
Www.epa.gov/owm/septic
Date system installed
Installer
Phone
Tank size gallons
Capacity bedrooms
Type conventional
alternative (type)
Scheduled
Activity
inspection
Activities
Completed
inspection
Comments
sludge layer okay-may need
pumping next year
Pumping Co./
Phone
Joe Pumper 555-1234
Place on electrical box (fuse box) or other convenient location.
Things to keep in mind:
[Regularly inspect your system and pump your
tank as necessary.
[Use water efficiently.
[Don’t dispose of household hazardous wastes
in sinks and toilets.
[Plant only grass over and near your septic
system. Roots from nearby trees or shrubs
might clog and damage the drainfield.
[Don’t drive or park vehicles on any
part of your septic system.
Doing so can compact the
soil in your drainfield or
damage the pipes, tank, or
other septic system
components.
Next
Service
Septic System Maintenance Record
Jan. 2003
Septic System Description
Contact your local authority if you don’t have this
information.
Homeowner Septic System Checklist