I-35 Corridor Development Wastewater Feasibility: How to Avoid the Most Common TCEQ Errors in Hays County

Why is wastewater feasibility harder in Hays County?

Because three constraints stack on the same parcel. The Edwards Aquifer rules, a patchwork of service providers and changing terrain each decide which wastewater options are real.

Hays County is one of eight counties under TCEQ's Edwards Aquifer rules in 30 TAC Chapter 213. On the recharge zone, 30 TAC §213.6 prohibits new municipal and industrial discharges that would add pollutant loading. It also prohibits land application that relies on percolation, except licensed private sewage facilities. Irrigation is reviewed case by case and needs at least secondary treatment.

Upstream of the recharge zone, new or increased discharges within five miles must meet 5 mg/L CBOD, 5 mg/L TSS, 2 mg/L ammonia nitrogen and 1 mg/L phosphorus as 30-day averages (§213.6(c)(1)). A discharge plan that works elsewhere in Texas may not work here at all.

Service is the second layer. Land along I-35 may sit in a city's extraterritorial jurisdiction, in a provider's certificated service area, or in neither. The PUC's CCN mapping resources show who holds a certificate. A certificate tells you who may serve, not that capacity exists, so ask the provider in writing.

Terrain is the third. The county runs from flatter land east of I-35 to Hill Country west of it, so gravity sewer that works on one tract can need a lift station on the next.

Why do generic flow assumptions draw TCEQ questions?

Because the reviewer checks your flow against the design rules, not a rule of thumb. TCEQ's design criteria in 30 TAC §217.32 set how design flow and peak flow are calculated, with flows by source in Table B.1, and call for site-specific data for peak flow where it exists.

Build the flow from the actual program: unit counts and types, commercial space and any process water. A per-acre factor borrowed from another project invites a notice of deficiency.

Flow by phase matters too. TCEQ's Domestic Technical Report (form TCEQ-10054) asks for the design flow, two-hour peak flow and estimated start dates of each phase: Interim I, Interim II and Final.

When should the feasibility study happen?

During due diligence, with a program specific enough to size flows. Too early, and the study answers a question about a project you will not build. Too late, after closing and a fixed lot layout, and it can only justify a decision already made. Done in between, it can still change the site plan, the phasing and the price.

What does TCEQ need from the receiving water evaluation?

A real picture of the stream at low flow. The 2022 Texas Surface Water Quality Standards define the critical low flow as the seven-day, two-year low flow (7Q2). Where flow records exist, a stream with a 7Q2 under 0.1 cubic feet per second is intermittent.

Many small streams in the corridor are intermittent. One with perennial pools is presumed to have a limited aquatic life use and the dissolved oxygen criteria that go with it (§307.4(h)(4)). Those details drive the effluent limits, so a generic evaluation invites more questions. Plan for site-specific stream work when the record is thin.

Why plan for the operator during design?

Because the permit holder must have a licensed operator before the plant runs. Under 30 TAC §30.350, the permit holder employs or contracts with licensed operators. The chief operator's license must equal or exceed the facility's category, and the plant must be operated at least five days a week by an operator holding the required license.

Decide who will own and run the plant, whether a district, a utility or a contract operator, while you design it. Our post on package plant operator staffing covers the license levels.

How do land application areas end up too small?

They are sized from assumptions instead of soil and water balance data. For irrigation with effluent, 30 TAC §309.20 requires a soil survey of the application areas, a water balance, a nitrogen cap on the annual loading, and storage sized for a design rainfall year with at least a 25-year return frequency.

Each of those can grow the footprint, and every acre of disposal area is an acre that is not lots. Get site soil data before the site plan is set.

Why do lift stations and force mains show up late?

Because the collection layout was drawn before anyone surveyed the ground. A topographic survey and a preliminary collection layout during feasibility show where gravity fails and pumping starts, while the budget can still absorb it.

On the recharge zone, a sewage collection system also needs an approved plan before construction under 30 TAC §213.5(c). New gravity lines of six inches or more and all new force mains are tested for leakage, certified by an engineer and retested every five years.

How should phasing appear in the application?

Explicitly, phase by phase. State each phase's capacity, what triggers the next one and how the plant expands. That gives the reviewer something to check instead of something to ask about.

Phasing carries on after the permit. Under 30 TAC §305.126, when flow reaches 75% of the permitted flow for three consecutive months, the permittee must start engineering and financial planning for expansion. At 90% for three consecutive months, it must obtain TCEQ's authorization to build the added capacity.

What makes an application administratively incomplete?

Missing forms, sections and attachments, the most avoidable delay of all. TCEQ checks completeness before technical review starts. Under 30 TAC §281.18, the agency sends at least one notice of deficiency with 30 days to respond before it may return an incomplete application.

Edwards Aquifer plans run on their own clock. Under 30 TAC §213.4(e), TCEQ has 30 days to declare a plan administratively complete or deficient, then 90 days to review a complete one. Since October 16, 2023, TCEQ's Edwards Aquifer Protection Program has handled all applications through its Austin Regional Office.

Before you submit, run this check. Every answer should be yes; any no is a likely deficiency or a later redesign:

1. Has the provider confirmed in writing whether it can serve the site, and with what capacity?
2. Do you know whether the site is on the Edwards recharge, transition or contributing zone?
3. Is the flow built from the actual unit mix and uses, phase by phase?
4. Does the receiving water evaluation use real low-flow data for the actual stream?
5. Is the land application area sized from site soil data and a water balance?
6. Has a topographic survey confirmed where lift stations are needed?
7. Are the plant's owner and licensed operator decided?
8. Has the package been checked against TCEQ's current forms and instructions?

Take every no to your engineer as the agenda for your next project meeting.

This post is general education on TCEQ rules as published in October 2026. TCEQ decides each application, and your site may raise issues not covered here, so confirm the current rules with your engineer before you file.

Frequently asked questions

How early should wastewater feasibility start on a Hays County tract?

As soon as the tract is a serious candidate. A preliminary answer before the due diligence period ends can still shape the price, the contract contingencies or the decision to close. A detailed study follows before the lot layout is fixed.

Can a new plant discharge to a stream on the Edwards recharge zone?

Not if the discharge would add pollutant loading: §213.6(a)(1) prohibits new municipal and industrial discharges on the recharge zone. Irrigation is reviewed case by case, and discharges up to five miles upstream must meet the tighter limits above.

I'm buying land near Kyle and the city hasn't committed to sewer service. Should I start on a private plant permit while we keep talking to the city?

Often yes, as far as feasibility and a permit strategy, so your schedule does not hang on one answer. Hold construction spending until service is settled, and keep the city informed of the parallel track.

I'm a Texas civil engineer preparing my first land application permit for a Hays County subdivision. What should I get right first?

Completeness, then the basis of design. Build the flow under §217.32, support the application area with a soil survey and water balance under §309.20, and state whether the site is on an Edwards zone.

Related resources

• Edwards Aquifer Recharge Zone Development: What Austin Area Developers Must Do Differently for Wastewater
• Texas Land Application Permits Explained: Spray Irrigation, Subsurface Drip, and Evaporation Ponds
• What Engineers Submit to TCEQ and Why Your Application Gets Rejected
• Flow Rate Projections: How to Size a Wastewater Treatment Plant for Your Development Without Over-Building

Evaluating wastewater feasibility for a Hays County site?

We answer the service, Edwards and permitting questions during due diligence, so the application you file is built on the site you actually have.

We specialize in:

• Site feasibility and due diligence
• Wastewater flow projections and treatment plant design
• TCEQ wastewater permitting, TPDES and TLAP
• Land application and reuse system design
• Lift station, force main and collection system design
• Construction administration

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