An On-Site Wastewater Treatment System (OWTS), commonly known as a septic system, treats the wastewater on an individual’s property. Septic systems are installed on properties that cannot be served by a wastewater utility. Arapahoe County Public Health permits the installation, repair, and use of these systems in the County.
Arapahoe County OWTS Regulations
Septic Permit Process
A septic permit is required for new installations, expansions, and repairs. Begin by applying for a septic permit and providing all required information below:
- Application for an On-site Wastewater Treatment System Permit
- Directions to Property
- Site Evaluation and Design Document Checklist (recommended)
- Percolation Test Summary and Data Form (if applicable)
- Soil Profile Test Pit Log
- Conventional OWTS Design Worksheet (if applicable)
- Tank Replacement Worksheet
- Application to Install a Lift Station
- Record Drawing
- Application for a Variance for an On-site Wastewater Treatment System
Permit applications may be sent to the Environmental Health offices or emailed.
Find an OWTS Professional
- Find a septic system professional
- Find a transfer of title/user permit inspector from the National Association of Wastewater Technicians
A Use Permit is required for:
- A sale or change of ownership of a property
- A change in use of the property (i.e., a residence to a business)
- Any addition of bedrooms
- An addition of a separate "modular" home
- Other reasons deemed necessary by the department
To obtain a permit, the following is required:
- Application for a Septic Use Permit
- Use Permit Inspection Form
- Use Permit Repair Verification Form (if applicable)
- Agreement to Forego Expansion (if applicable)
- Agreement to Repair a Septic (if applicable)
Use permit inspections must be conducted by a Certified NAWT Inspector.
New/Renewal Applications for Professionals
All Onsite Wastewater Treatment System designers, soil evaluators, installers, inspectors, operation and maintenance providers, and pumpers will be required to obtain the National Association of Wastewater Technicians (NAWT) training course for the discipline they want to work in.
- Application for a License to Install Onsite Wastewater Treatment Systems
- Application for a License to Clean Onsite Wastewater Treatment Systems
Permit applications may be sent to any of our Environmental Health offices or via email.
15400 E. 14th Pl., Suite 115
Aurora, CO 80011
6162 S. Willow Dr., Suite 100
Greenwood Village, CO 80111
Phone: 303-795-HLTH (4584)
- Under what conditions must an OWTS be designed by a Colorado Licensed Professional Engineer?
A Colorado Licensed Professional Engineer must design a system if any of the following occur:
- The following soil types are identified within 4 feet below the depth of the proposed soil treatment area (STA): 0, 3A, 4, 4A, 5, R-O, R-1, R-2; treatment levels TL2, TL2N, TL3, and TL3N as specified in tables 10 and 11 of Regulation O-17.
- Groundwater, bedrock, or other limiting layer is present within 4 feet below the depth of the proposed STA.
- The ground slope at the area of the proposed STA is greater than 20%, or (d) the proposed system is a commercial system, (e) the proposed system utilizes pressure distribution.
- I am selling my property and need to get my waste water system certified. What should I do?
The seller of the property is required to obtain a use permit prior to the sale of the property.
- What is the minimum lot size for an on-site wastewater treatment system (OWTS)?
We do not have a minimum lot size requirement. Local planning agencies do have minimum lot sizes in their zoning codes. They typically recommend a minimum of one acre for lots supplied by central water and 2.5 acres for lots with wells.
- How often do I need to pump my septic tank?
We require that septic tanks be inspected every four years and pumped when scum and sludge accumulate to greater than 25% of the effective volume of the tank. Dosing tanks shall be inspected and pumped if sludge accumulation is observed. If your OWTS receives higher than average use, as determined by your licensed cleaner, you may want to consider a more frequent pumping interval. All pumping and evaluation of septic tanks should be done by a licensed cleaner.
- Will I be able to irrigate or have horses where my Soil Treatment Area (STA) is located?
We recommend that an STA be left largely untouched by homeowners. Irrigated landscaping is not recommended, since it has the possibility to saturate an STA causing the septic system to fail prematurely. You may consider planting buffalo grass or other natural grasses which do not require irrigation. Mow any grasses planted on the STA area regularly. Horses or other livestock should not be placed on an STA, because compaction of the soils may occur causing premature failure of your absorption area.
- Can I install a bathroom in a garage, barn, etc., and connect it to my existing on-site wastewater treatment system (OWTS)?
We generally allow connection to the existing septic system, provided the owner notifies Arapahoe County Public Health in advance, and we approve the connection. An inspection of the new plumbing and applicable fee(s) is required. Prior to final approval, the existing record drawing of the system must also be amended to show new buildings and plumbing. For more information, contact our Environmental Health office prior to starting your project.
- I am unsure where my on-site waste water treatment system (OWTS) is located. Do you have records of my system?
We maintain online records for existing septic systems in Arapahoe County which contain record drawings identifying OWTS locations. Please keep in mind that we may not have records of all septic systems due to age or permit status. In this case it may be necessary to contact a licensed installer or a certified Use Permit inspector or surveyor to locate your system.
- I accidentally damaged some components of my septic system. Who should I call to inspect and repair the damage? Do I need a permit?
In this situation it would be best to have the system evaluated by a licensed septic contractor. If the damage is relatively minor such as damage to a single pipe or chamber, it likely will not require a permit, but the repair will need be done by a licensed contractor, and all repairs will need to be inspected by Arapahoe County Public Health prior to being covered. Inspection fees may apply. If the damage is more extensive such as damage to the tank or extensive damage to the soil treatment area (STA), it may require a repair permit. Consult with your contractor and Arapahoe County Public Health.