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Detention: what the rules say, and what the districts actually do
Detention ponds are often the largest shared cost between neighboring districts. This page sets out how the cost is supposed to be shared, and compares that with each district's actual arrangement.
What detention is
When land is developed, roofs and pavement send rain off faster than open ground does. A detention pond holds that water and releases it slowly, so new development doesn't raise flood levels downstream. Harris County requires new development to provide detention. The required volume depends mainly on the size of the land and how much of it is paved or built on (its "impervious cover").
A regional pond often serves several districts, so its cost has to be divided twice: once for building it (capital) and once for running it every year (mowing, maintenance, repairs).
What is meant to happen
| Rule | What it says | Status |
|---|---|---|
| 30 TAC §293.44(a)(2) (TCEQ) | When districts share a facility, each district's share of the cost is to follow the benefit it receives, measured by the capacity designed for it. | Law (TCEQ rule) |
| 30 TAC §293.44(a)(8) (TCEQ) | A district may pay for capacity beyond its own needs (oversizing) only under an agreement that gives it adequate payment for that extra capacity. | Law (TCEQ rule) |
| Water Code §49.213 | Districts may contract with each other to build and run shared facilities. The contract sets each district's share. | Law |
| Tex. Const. art. III §52 (Gift Clause); Att'y Gen. Ops. KP-0283, KP-0234 | A district that pays toward another body's facility must serve its own public purpose, get a return benefit, and keep enough control to make sure it does. | Law |
| Annual running costs | No statute or TCEQ rule we have found sets how running costs are divided. The districts' contract decides. | Set by contract |
"Law" means the requirement is in a statute, rule or the constitution. Practices engineers commonly use are listed separately below and labeled as practice.
Common ways to divide detention costs (practice, not law)
| Basis | How it works | Who it favors |
|---|---|---|
| Drainage area | Each district pays in proportion to the acres that drain to the pond. | Neutral between homes and commercial land. |
| Runoff-weighted area | Acres weighted by how much is paved, so a paved shopping center counts more per acre than lots with yards. | Closest to cost causation: whoever creates the runoff pays for holding it. |
| Detention volume allotted | The engineer's drainage study assigns each tract a share of the pond's volume, and costs follow it. | Follows the design (the §293.44 "design capacity" approach). |
| Taxable value (overlay district) | A separate drainage district covers all the land and taxes it by value. This is how Bridgeland funds drainage, through Harris County WCIDs 157 to 159. | Everyone in the area pays, in proportion to property value. |
| Connections (ESFC) | Costs follow water and sewer connections ("equivalent single-family connections"). | Standard for water and sewer. For drainage, it charges undeveloped or commercial land very little until it connects. |
Fairness tests
- Cost causation: does each district pay for the runoff its land creates?
- Benefit: does each district pay for the protection it gets?
- Design: does the split match the capacity the engineer designed for each district (§293.44)?
- Timing: if one district pays more now because the other isn't built out, is there a true-up or buy-in later?
- Openness: is the basis written down where residents can see it?
Actual arrangement: Dunham Pointe (HCID 13 and HCID 14)
All homes are in HCID 14. HCID 13 is the US 290 commercial frontage (about 212 acres). HCID 13 owns and runs the regional ponds under a 2018 Joint Facilities Agreement and a 2022 Cost Sharing Agreement, restated April 15, 2025. Both districts use the same engineer and general counsel.
| Item | What is meant to happen | What the records show | Open question |
|---|---|---|---|
| Building Pond "AB" (capital) | Share by the capacity designed for each district (§293.44(a)(2)). | HCID 14's design share was 41%. HCID 14's 2022 bonds paid 60.43% of grading ($1,868,291) and about 60% of the land ($2,042,180). The pond is titled to HCID 13. | What changed from 41% to 60.43%, and is there an agreement giving HCID 14 adequate payment for the difference (§293.44(a)(8))? |
| Running costs, FY2024 | Set by the contract. | HCID 13 paid 38% (budget) or 21% (actual) of detention costs. | — |
| Running costs, FY2025 onward | Set by the contract. | The April 2025 restatement moved most detention lines (mowing $450,000; lake maintenance $64,300) to a per-connection basis. HCID 13 has almost no connections. Its share fell to about 8%: $38,978 in FY2025, against $169,340 the year before. FY2026: HCID 14 $906,700 of $982,000. | Why connections for drainage? Detention handles runoff from land, not water use. |
| Comparison on land bases | (Practice) drainage area or runoff-weighted area. | On district acreage, HCID 13's share would be about 20%. On land that actually drains to the ponds, about 20 to 24%. Weighted for runoff from paved commercial land, higher still. That is about $120,000 to $160,000 a year more than HCID 13 pays now. | What basis does the engineer's allocation (Exhibit A) use, and why? |
| Land outside both districts | Land that drains to a pond would normally pay toward it. | About 290 acres are in neither district. About 147 acres of HCID 13-owned land, including Pond AB's reserve, sit inside HCID 14's boundary, adding acreage but no taxable value. | Does that land drain to the regional ponds? Harris County's drainage plans are due about Nov 24, 2026 (request R050932). |
Documents that would resolve this
- Exhibit A of the restated Cost Sharing Agreement (April 15, 2025): the allocation table and its basis.
- The April 15, 2025 board materials explaining the change to per-connection detention costs.
- The engineer's drainage study: the detention volume allotted to each district or tract.
- Any agreement compensating HCID 14 for the share of Pond AB above its 41% design share.
All four are covered by records requests to HCID 13 and HCID 14. Sources: HCID 13 audits FY2024 and FY2025; HCID 13 Regional Facilities Budgets FY2024 to FY2026; HCID 14 official statements 2022 to 2026A; TCEQ and HCAD boundary data. These are open questions, not findings: the documents above may explain the arrangement.
How Bridgeland does it
Bridgeland funds regional drainage through separate water control and improvement districts (WCIDs 157, 158 and 159) laid over its MUDs. Every property in the overlay pays the WCID tax by value, homes and commercial land alike: about $0.35 to $0.415 per $100 in 2025. That spreads drainage costs over all the land that benefits, without a contract between districts deciding the split.