Buying a Colorado Package Wastewater Plant: Settle Limits, Outlet and Operator Before the Purchase Order

Before you order a package wastewater plant in Colorado, you need a likely discharge limit from CDPHE, a known outlet, a named certified operator and a plan for who pays to run it. A vendor quote does not cover any of those. This recap walks through the order of operations we covered on the show, for small systems that are replacing aging lagoons.

Why are small Colorado systems looking at package plants?

Many small Colorado systems run lagoons or evaporation ponds, and the limits they face have tightened since those plants were built.

A lot of these lagoons date to the 70s and 80s. Nitrogen limits may not have existed then. Colorado also gets cold, so denitrification is hard to do in a basic lagoon plant.

That is why boards start shopping for a package plant. The risk is shopping before the approvals are understood.

Can you order the plant while approvals are still underway?

You can work approvals in parallel, but ordering equipment too early is risky. Parts of the approval can change the plant you need.

The CDPHE discharge permitting team can feel like a black box. Few people understand the modeling behind the limits, or how the discharge location affects them. I have seen plants built and then wait years on final items like chemicals or the last pieces of the discharge permit.

So ask any vendor whether they have actually built a plant in Colorado, and whether they know what limits are likely on different discharges around the state.

Site design and approval runs under Regulation 22 through the Water Quality Control Division. You get the site application approved, then the process design report approved. Most people do the site application first and the PDR after.

Both can run while the discharge permit moves on its own track. Start the discharge permit on day one and the site application right away. For Texas plants, we handle preliminary engineering reports and TCEQ design submittals in a similar way.

One way to estimate your limits is to look at what upstream and downstream dischargers on the same stream receive. Under 1 MGD, limits are typically a little more favorable. If you are under 1% of the stream's total, you should be getting dilution credits.

We are seeing modular systems come in, most commonly MBR. They handle a wide range of flows well, including low flows that still need to hit decent limits.

Who will own the permit and run the plant?

Two questions matter in Colorado: who physically treats the water, and who owns the permit and pays for it.

A developer may build the plant and a district may take it over. The district manager and chief operator then carry the operation and monitoring requirements long after the developer and vendor are gone. If someone offers to build and hand you a plant, ask who will hold the permit and who will pay to operate it.

Approval is just the start. You could run this plant for decades.

The plant's classification sets the operator level you need. In rural Colorado, talk to the contract operators around you, see what certification they hold and how it affects your contract cost.

The discharge permit also sets sampling and reporting. Decide who is responsible and what budget that takes.

The state also expects a plan to expand as flows grow. In a high growth area, account for the additional train in your site plan and process plan.

How should you split the money and check readiness?

Think of the costs in three places: the build and approvals, the operation, and the debt and reserves.

Operation includes power, sludge removal and parts. Debt and reserves means deciding who carries them. There is no single figure, because it depends on the situation, and the agreement between the parties is more a financing matter than an engineering one.

As a readiness check for the board: if you are not sure of your discharge route, the likely limits, the approval steps and your certified operator, you are probably not ready to order a plant.

Also ask what you will do if the limits come back tighter than the vendor assumed. I have seen clients order equipment and later find they could not use it at all.

One more option: if a neighboring system is close and it makes sense, ask whether you could use their permit. It is not common in Colorado because systems are so spread out.

Your one action item this week is to confirm your discharge limits and receiving water before any purchase order goes in. Utilities and municipalities we work with often start from the design basis, separate from any one vendor.

Watch the full episode

The full episode is on YouTube: https://www.youtube.com/watch?v=SR0iVAKnpcs

Frequently asked questions

What approvals does a Colorado package plant need?

A site application and a process design report under Regulation 22, plus a discharge permit. The discharge permit runs on its own track and can be started on day one.

Should I pick a vendor before the limits are known?

No. If limits come back tighter than the vendor assumed, you may be stuck. Start with the design basis and discharge route.

Do I need a certified operator?

Yes. The plant's classification sets the operator level required. In rural areas, check which contract operators are available and what certification they hold.

I'm a district manager in rural Colorado with an old lagoon and new nitrogen limits. Where do I start before asking vendors for quotes?

Work out your likely discharge limits and route, start the discharge permit and site application, and talk to local contract operators about certification. Then give vendors that information to quote against.

I'm a developer in Colorado who wants to build a plant and hand it to a district. What should the district ask me?

Ask who will hold the permit at the end and who will pay to operate it. The district manager and operator carry the monitoring and discharge limits long after the developer leaves.

Related Resources

• Colorado Package Wastewater Treatment Plant Permitting: CDPHE Approval, Operations, and Compliance
• Domestic Wastewater Treatment Works Design Criteria: The CDPHE Engineering Standards Package Plants Must Meet
• Colorado Water Quality Control Commission Basin Specific Standards: Why the Same Discharge Limit Does Not Apply Statewide

Not sure what limits your Colorado plant will face?

We start with the design basis and discharge route, separate from any one vendor. If you have picked a vendor, we work with them on sizing data, flows and likely limits, and help coordinate permits.

We specialize in:

• Package and modular wastewater plant design
• Extended aeration and MBR systems
• Design basis and discharge route studies
• Permit coordination with agencies and subconsultants
• Wastewater engineering for utilities and municipalities

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