Storm and Sanitary Sewer Permitting for Colorado Developments

In Denver, a development's storm and sanitary sewer work clears several DOTI wastewater approvals before the last one, the Denver SUDP (Sewer Use and Drainage Permit), is issued for each building. First come a CASDP when the site disturbs an acre or more, an approved drainage report and sanitary sewer study, and an SSPR for larger sites or shared private sewers. Design follows DOTI's criteria manuals and its April 2026 wastewater standard details.

Who needs Denver DOTI wastewater review?

Any new major development or redevelopment with storm or sanitary work. The owner has to provide adequate storm and sanitary sewer service to the site.

Denver's Wastewater Engineering and Permitting page lists the triggers: sites of one half acre or more, sanitary sewer lines, storm lines, drainage channels and water quality facilities. Development Services and DOTI's Wastewater Management Division manage the work together, and the page lays out five steps: the CASDP, submittal requirements, the SUDP, standards and details, and fees. Grading or construction that disturbs more than half an acre can also bring a drainage report or sanitary study, so that line is the first thing developers and builders should check on an infill lot.

When does Denver require a CASDP?

When construction, including demolition, disturbs one acre or more. Smaller sites can need one if they are part of a larger plan, have high erosion potential, disturb contaminated soils or place fill in waters of the U.S.

Denver's CASDP requirements (DOTIPT-401.3, August 2024) set the details:

• The Stormwater Management Plan (SWMP) has a narrative and site maps per section 15.7 of the storm drainage criteria manual, with two-foot contours.
• The cover sheet carries Denver's ten standard notes and a professional engineer's stamp.
• Self-inspections run at least every 7 days and after significant rain or snowmelt.
• The CASDP must be issued before Denver releases permits for any structure.
• It goes void if work does not start within 12 months.

It does not replace the state permit. The same document says a project disturbing an acre or more may also need CDPHE's construction stormwater permit (COR400000).

What does the Denver drainage report have to show?

That the storm system meets Denver's criteria, certified by a Colorado-licensed engineer. The final report and construction drawings must be approved before the SUDP is issued.

The Denver Storm Drainage Design and Technical Criteria Manual (April 2024) governs. Approval lasts one year, and construction has to start inside it (section 2.3.2). The 2024 revision changed design: detention must be full spectrum detention, including the excess urban runoff volume. Every project needs runoff reduction, and sites disturbing an acre or more also need permanent stormwater control measures (section 14.2).

What does a Denver sanitary sewer study cover?

The project's flows and their effect downstream. It is required for every development tributary to Denver's sewers before the SUDP, unless DOTI waives it.

The Sanitary Sewer Design Technical Criteria Manual dates from 2008 but is still the one DOTI posts. Section 2.06 requires a Colorado PE's seal, average, peak and infiltration flows at each connection, and a capacity check down to the first significant outfall. Reviewers check the public sewer criteria too:

• No public sewer under 8 inches; private on-site sewers may be 6 inches (section 3.06.1).
• Peak flow no deeper than 0.80 of the diameter, with Manning's n of 0.013 (sections 3.06.2 and 3.06.3).
• A minimum depth of 9 feet, and manholes no more than 500 feet apart on 8 to 36 inch pipe (sections 3.01.1 and 3.10).

What is a Denver SUDP, and how do you apply?

It is the DOTI wastewater permit for a building, reviewed for sanitary, storm drainage and groundwater. You file it with the building permit in E-Permits, never on its own.

Per DOTI's Sewer Use and Drainage Permits page, review covers sanitary, storm grading, floodplain, groundwater and pretreatment devices, and starts once the building permit application is accepted. The SUDP entrance requirements for commercial and multi-residential projects (May 2025) add the details that catch people:

• Each building or structure needs its own SUDP.
• Where they apply, the SSPR must be approved and the CASDP issued before the SUDP is approved.
• Plans must say "For Construction."
• Groundwater within 4 feet of the lowest construction point means a groundwater management system plan.
• Building sewer laterals are 4 inches minimum.
• Plans revised after issuance need a supplemental SUDP.

New commercial and multi-residential work also needs a site development plan, so it helps to know how Denver's site development review process works.

When does a project need an SSPR?

When it is larger than half an acre, or when more than one structure (other than an ADU) shares a private sanitary or storm system tied to a public main.

The Sanitary and Storm Project Review covers public and private sewer construction, easements and abandonments. DOTI's application to construct a storm sewer, sanitary sewer or right-of-way improvement commits the owner to a Colorado PE responsible for the plans, construction observation by or under a Colorado PE who certifies the as-builts, and a three-year warranty. Private on-site work needs those certifications and a final city inspection before the certificate of occupancy is validated. The SSPR allows no building connection; that still takes the SUDP.

Which Denver DOTI wastewater standards and details apply?

The current storm and sanitary manuals, the April 2026 wastewater standard details and the April 2026 construction specifications, all on DOTI's Standards and Details page.

The April 2026 Wastewater Standard Details apply to all storm and sanitary sewer construction under DOTI's jurisdiction, from trenching and bedding to manholes and inlets. This set added four modified Number 16 inlets for endwall pipes up to 24-inch RCP. Where a detail conflicts with the specifications, the specifications govern. Check the date on any detail copied from an old plan set.

What changes outside Denver?

The local jurisdiction or district sets its own criteria. Two state rules still apply anywhere in Colorado.

• Construction stormwater. Under Regulation 61, the Colorado Discharge Permit System regulations (5 CCR 1002-61), a site disturbing one acre or more, or a smaller site within a larger common plan that reaches an acre, needs permit coverage for its stormwater discharges (sections 61.3(2)(e)(iii)(J) and 61.3(2)(f)(ii)(A)).
• Lift stations and interceptors. Regulation 22, the site location and design regulations (5 CCR 1002-22), covers lift stations and certain interceptors designed for more than 2,000 gallons per day (section 22.1(2)). A new lift station needs a site location application (section 22.9). An eligible interceptor can certify instead, with notice 90 days before construction and the treatment entity's capacity certification (section 22.8(2)).

So ask the receiving utility about capacity early. It is a site feasibility question, best answered before you close on the land.

Is your Denver submittal ready?

Check this before you upload. The storm manual lets Denver return an incomplete submittal without review (section 2.2.6).

1. Do you know whether the site disturbs an acre or more, counting demolition and any larger plan?
2. Is the SWMP built to section 15.7, with Denver's standard notes?
3. Does the drainage report carry the Colorado PE certification and use full spectrum detention unless the manual exempts the site?
4. Does the sanitary study check capacity to the first significant outfall?
5. Have you settled whether the project needs an SSPR?
6. Is every detail from the April 2026 set?

Pass rule: every answer is yes before you upload. Then ask your engineer which approval sits on the critical path and who provides Colorado PE construction observation.

Scope note: this summarizes Denver DOTI documents and Colorado regulations posted as of October 2026. Criteria and forms change, and the plan reviewer's comments govern your project.

Frequently asked questions

Does a Denver project need both a CASDP and a state stormwater permit?

Often, yes. Denver's CASDP document says a project disturbing an acre or more may also need CDPHE's construction stormwater permit. One does not cover the other.

How long is a Denver drainage report approval good for?

One year, under section 2.3.2 of the storm manual. After that, re-approval is case by case against current criteria.

I'm a developer with a 0.8-acre infill lot in Denver and two buildings sharing one private sewer. Do I need an SSPR as well as the SUDP?

Very likely. DOTI's entrance requirements call for an SSPR on a project over half an acre, or where more than one structure shares a private sewer tied to a public main, and your lot meets both. Each building also needs its own SUDP.

I run a small civil firm in Colorado and we're designing a lift station for a subdivision outside Denver. Does CDPHE get involved, or just the local utility?

Both, if the design capacity is above 2,000 gallons per day. Regulation 22 requires a site location application, sent first to local governments and the 208 planning agency for comment, then design review. The utility's own criteria apply on top.

Related resources

• First Steps to Getting Your Project Approved with Denver Water
• Adams County Project Review Process
• CDPHE Site Application vs. Discharge Permit Application: The Two-Step Process Colorado Developers Often Confuse Into One
• Lift Stations and Collection Systems: What the Plant Needs Upstream to Function Properly

Sorting out storm and sanitary sewer permits for a Colorado site?

The order of approvals is easiest to set while the site plan can still move. MES is licensed in Colorado, has an office in Golden, and prepares the drainage, sanitary and stormwater documents these reviews ask for.

We specialize in:

• Storm drainage reports and construction drawings
• Sanitary sewer studies and collection system design
• Construction stormwater management plans
• Lift station design
• Site civil engineering for land development
• Construction administration

Modern Engineering Solutions, McKinney, Texas. Contact: (214) 833-6748 or mod-eng.com