No Post‑Decree Cure: Colorado Supreme Court Requires Well‑Specific, “Reasonably Accurate” Depletion Modeling Before Conditional Groundwater Rights Are Decreed

Case: Town of Firestone v. BCL Colorado LP, et al. (In re Concerning the Application for Water Rights of Town of Firestone), 2025 CO 33, No. 24SA109 (Colo. May 27, 2025)

Court: Colorado Supreme Court (en banc)

Author: Justice Berkenkotter; Chief Justice Márquez, Justices Hood, Hart, and Samour joining; Justice Gabriel, joined by Justice Boatright, dissenting

Disposition: Orders of the Water Court (Division 1) affirming partial dismissal without prejudice of three well‑field claims and rejecting reliance on retained jurisdiction to prove non‑injury later

Introduction

This decision addresses how precisely an applicant must define its proposed tributary groundwater wells and associated depletion modeling when seeking conditional groundwater rights with an augmentation plan in an over‑appropriated basin. The Town of Firestone pursued conditional rights for five wells or well fields and an augmentation plan on the St. Vrain Creek system, part of the South Platte River basin. After three days of trial, the Water Court partially granted St. Vrain Sanitation District’s C.R.C.P. 41(b)(1) motion, dismissing without prejudice Firestone’s claims for three “well fields” whose well locations and unit response functions (URFs) were modeled using estimated or representative locations rather than well‑specific data. The Water Court also rejected Firestone’s proposal to use retained jurisdiction as a vehicle to supply specific locations and updated URFs after entry of a decree.

On appeal, Firestone argued the Water Court misapplied the “reasonably accurate” standard from City of Aurora (2005), erred in declining to retain jurisdiction, wrongly allowed St. Vrain to contest issues listed as “undisputed” in a pretrial Rule 11 statement, and clearly erred in factual findings. The Colorado Supreme Court affirmed, clarifying that:

Non‑injury must be proven at the time of adjudication; retained jurisdiction cannot be used to postpone that burden.
Quarter‑quarter section descriptions can suffice in some contexts, but where well location uncertainty materially affects depletion timing and amount, well‑specific URFs are necessary to satisfy “reasonable accuracy.”
A Water Court may repudiate or disregard a conditional Rule 11 stipulation and allow litigation of non‑injury because injury is a question of law and the Rule 11 language reserved the right to revisit issues.
On this record, the Water Court’s factual findings were supported by trial testimony and not clearly erroneous.

Summary of the Opinion

The Supreme Court affirmed both the Water Court’s 2023 order partially granting St. Vrain’s Rule 41(b)(1) motion and its 2024 decree. The core holdings are:

Case‑by‑case application: Conditional groundwater rights accompanied by augmentation plans are evaluated case‑specifically; no bright‑line rule requires a completed well, but the applicant must demonstrate non‑injury with sufficiently reliable, well‑tied modeling when local hydrology makes that necessary.
“Reasonably accurate” means well‑specific when it matters: Where URFs materially depend on precise well locations, orientation (vertical vs. horizontal), and site conditions (e.g., gravel pits, distance to the stream), modeling based on “representative” quarter‑quarter centroids is not reasonably accurate.
No use of retained jurisdiction to prove non‑injury later: Retained jurisdiction under section 37‑92‑304(6) exists to reconsider injury after a non‑injury finding and operational experience, not to defer the applicant’s initial burden.
Stipulations do not bind courts on questions of law: The Water Court did not abuse its discretion by allowing St. Vrain to contest non‑injury despite a conditional Rule 11 “undisputed” statement; injury is ultimately a legal question and Rule 11 language expressly reserved objections.
Factual findings supported: Testimony showed that small changes in well location (e.g., 150 feet) could multiply near‑term depletions, that URFs varied across a quarter‑quarter, and that Firestone’s planned well numbers and orientations were unsettled for three fields. The Water Court’s conclusion that Firestone had not met its burden was supported by the record.

The dissent would have reversed, concluding the Water Court demanded “exact locations” inconsistent with City of Aurora’s “reasonable accuracy,” and that the record showed sufficient specificity to permit a non‑injury determination.

Detailed Analysis

Precedents Cited and How They Shaped the Decision

City of Aurora ex rel. Util. Enter. v. Colorado State Engineer, 105 P.3d 595 (Colo. 2005): Sets the “reasonably accurate” standard and allocates burdens in augmentation adjudications. An applicant must establish timing and location of depletions and availability of replacement water to make a prima facie showing of non‑injury; retained jurisdiction exists to reconsider injury after a non‑injury finding and actual operations. The majority applies Aurora to require well‑specific URFs where location uncertainty materially affects depletions and to reject using retained jurisdiction to cure initial proof gaps.
Buffalo Park Dev. Co. v. Mountain Mutual Reservoir Co., 195 P.3d 674 (Colo. 2008): Reinforces that reliable evidence on quantity, time, location of depletions and legally available replacement water is the applicant’s responsibility and “cannot be postponed to occur under retained jurisdiction.” The majority relies on Buffalo Park to affirm dismissal where the evidence did not permit a reasonably accurate non‑injury finding at the outset.
Upper Eagle Regional Water Auth. v. Wolfe, 230 P.3d 1203 (Colo. 2010): Clarifies retained jurisdiction’s function: to allow reconsideration of injury determinations already made, in light of real‑world operations. The Court uses Upper Eagle to hold that retained jurisdiction presupposes an initial non‑injury determination and cannot replace it.
City & County of Denver ex rel. Board of Water Commissioners v. Colorado River Water Conservation District, 696 P.2d 730 (Colo. 1985): Emphasizes an ad hoc, context‑specific approach to diversion structure specificity for conditional rights. The majority invokes this to reject any bright‑line rule either requiring a completed well or allowing loose siting; context governs.
City of Thornton v. Bijou Irrigation Co., 926 P.2d 1 (Colo. 1996): Notice does not demand a precisely located point of diversion in all settings. The majority distinguishes those contexts from augmentation for new tributary wells where injury analysis turns on exact location.
Farmers Reservoir & Irrigation Co. v. Consolidated Mutual Water Co., 33 P.3d 799 (Colo. 2001): Defines “injury” as diminution of water available to a senior at the time, place, and amount of the decreed right. This frames why timing and location of depletions (and corresponding replacement) are critical.
Centennial Water & Sanitation Dist. v. City & County of Broomfield, 256 P.3d 677 (Colo. 2011): Describes augmentation as replacing out‑of‑priority depletions, including delayed “lagged” effects from pumping.
Lake Meredith Reservoir Co. v. Amity Mutual Irrigation Co., 698 P.2d 1340 (Colo. 1985): Whether to give effect to a stipulation lies within trial court discretion. Supports the Water Court’s decision to let St. Vrain contest non‑injury at trial.
Bar 70 Enters., Inc. v. Tosco Corp., 703 P.2d 1297 (Colo. 1985): Parties cannot stipulate questions of law. Because the injury inquiry is a question of law (Buffalo Park), the Water Court was not bound by a conditional Rule 11 “undisputed” statement.
Burlington Ditch Reservoir & Land Co. v. Metro Wastewater Reclamation Dist., 256 P.3d 645 (Colo. 2011) and Anderson v. City of Bessemer City, 470 U.S. 564 (1985): Standards for deference to trial court fact findings.
People v. Hall, 496 P.3d 804 (Colo. 2021): Judges in bench trials may actively question to clarify facts as fact‑finders; cited to support the Water Court’s probing of expert assumptions about URFs and Paragraph 48.

Legal Reasoning

1) No bright‑line completion requirement; but “reasonable accuracy” can demand well‑specifics

The Court expressly disclaimed creating a bright‑line rule that a well must be built before a conditional groundwater right can be decreed. Instead, it reaffirmed that specificity is context‑dependent. For conditional tributary groundwater rights in an over‑appropriated basin, where the augmentation plan’s injury analysis turns on the exact distance to and interaction with the stream, the majority held that “reasonable accuracy” requires well‑specific URFs when generalized or centroid‑based modeling would materially misstate timing and magnitude of depletions.

Here, several facts made well‑specific URFs indispensable:

Experts acknowledged URFs vary within a single forty‑acre quarter‑quarter; moving a well 150 feet could increase one‑day depletions nine‑fold.
Whether wells would be vertical or horizontal affected depletion patterns.
Local features (e.g., unlined gravel pits, proximity to St. Vrain Creek) could materially alter stream capture and lag.

Given those sensitivities, the Water Court reasonably found that Firestone’s representative/centroid‑based URFs did not allow a reasonably accurate non‑injury determination for three well fields.

2) Retained jurisdiction cannot replace the applicant’s initial burden

Firestone’s proposed Paragraph 48 would have allowed it, post‑decree, to add or refine well locations and update URFs under retained jurisdiction. The Court rejected this approach as contrary to section 37‑92‑304(6) and controlling precedent. Retained jurisdiction is a supervisory tool to revisit an injury determination already made after observing real‑world operations; it cannot be used to postpone or outsource the initial showing of non‑injury that is a condition precedent to decree an augmentation plan. City of Aurora and Buffalo Park compelled that result.

3) Stipulations and the Water Court’s discretion

Although the parties’ water court Rule 11 statement listed certain URFs as “adequate to prevent injury,” it expressly reserved objections and noted the list reflected current understanding. The Water Court permitted St. Vrain to challenge non‑injury at trial. Because non‑injury is a question of law, and because stipulations cannot bind a court on legal questions, the Water Court acted within its discretion to repudiate the conditional stipulation and hear the evidence.

4) Factual findings were not clearly erroneous

The record showed meaningful uncertainty as to the number, location, and orientation of wells for three fields, and expert concessions established that small siting shifts could materially change depletions. The Water Court credited that testimony and concluded the URFs offered were not reliable for a non‑injury finding. Under Burlington Ditch and Anderson, those fact findings had adequate record support and were not clearly erroneous.

The Dissent

The dissent would have reversed and remanded, emphasizing two points:

The Water Court, in the dissent’s view, effectively demanded “exact locations,” exceeding City of Aurora’s “reasonably accurate” standard and ignoring that augmentation adjudications unavoidably involve uncertainty.
The record, the dissent argued, showed that Firestone did identify approximate locations, distances from the creek (e.g., 100 feet; 4,101 feet; 250 feet), likely well types for some fields (vertical in two fields; horizontal in one), and even a single‑well plan for the St. Vrain field, which should have sufficed for a reasonably accurate analysis.

The majority responded implicitly that uncertainty here was not merely routine but outcome‑determinative: URFs were shown to be highly sensitive to precise siting and well configuration, making generalities insufficient to protect senior rights at the decreeing stage.

Impact and Practical Implications

For applicants and municipal planners

Applicants seeking conditional tributary groundwater rights in over‑appropriated basins should expect to present well‑specific URFs tied to reasonably definite locations, orientations, and counts whenever local hydrology makes URFs location‑sensitive.
Quarter‑quarter legal descriptions may still suffice for notice or for less location‑sensitive contexts (e.g., certain surface diversions or storage), but they will not carry the non‑injury burden where URFs turn on precise siting.
Do not rely on retained jurisdiction to fill modeling gaps. The non‑injury showing is front‑loaded.
Financing and construction sequencing should anticipate earlier site characterization (test borings, pilot wells, refined siting corridors) to support well‑specific modeling at adjudication.

For engineering practice

Use site‑specific URFs calibrated to proposed well coordinates and configurations; where uncertainty remains, bracket with bounding URFs and propose protective, conservative replacement schedules keyed to the worst‑case URF.
Explicitly account for local features (unlined gravel pits, alluvial variability, aquifer thickness and transmissivity) that materially influence stream depletions.
Demonstrate that multiple wells will be spaced to minimize interference, and quantify how spacing affects URFs and depletion timing.

For litigation and case management

Be cautious with pretrial Rule 11 “undisputed” statements; reserve rights clearly, and do not assume such statements will bar legal challenges at trial, especially on injury questions.
Opposers can press a C.R.C.P. 41(b)(1) motion after the applicant’s case‑in‑chief if the non‑injury showing is inadequate.
Expect Water Courts to probe retained‑jurisdiction language that would allow post‑decree location changes or URF updates without an initial non‑injury determination.

Complex Concepts Simplified

Augmentation plan: A court‑approved program allowing a junior to divert out‑of‑priority, provided they replace depletions in time, place, and amount so seniors are not injured.
Lagged depletions: Groundwater pumping from a stream‑connected aquifer reduces streamflow later in time; the lag and magnitude depend on distance to the stream and aquifer properties.
Unit Response Function (URF): An engineering tool that predicts how much and when stream depletions will occur in response to a unit of pumping at a particular well. URFs are location‑specific.
Glover equation: A commonly used analytical method to estimate stream depletions from pumping based on aquifer characteristics and well‑to‑stream distance.
Quarter‑quarter section: A forty‑acre subdivision of a section used for land descriptions. A centroid within that area may not reflect a specific well’s depletion behavior.
Retained jurisdiction: Statutory authority for Water Courts to revisit and adjust a decree after a non‑injury finding and real‑world operation reveal unforeseen injury. It is not a device to defer the applicant’s initial proof.
C.R.C.P. 41(b)(1): Involuntary dismissal after the plaintiff rests if the evidence is legally insufficient to warrant relief; used here after Firestone’s case‑in‑chief.

Conclusion

This decision does not create a categorical rule that wells must be built before conditional rights are decreed. It does, however, clarify and sharpen the “reasonable accuracy” requirement for augmentation plans tied to new tributary groundwater rights: when the injury analysis turns materially on precise well siting, configuration, and local conditions, an applicant must present well‑specific modeling at adjudication. The Court also underscores that retained jurisdiction cannot be used to postpone the initial non‑injury showing and that Water Courts retain discretion to repudiate conditional stipulations on questions of law.

Key takeaways:

Non‑injury is a threshold determination; you must prove it now, not later.
Well‑specific URFs are required where siting materially affects depletions; centroid or representative modeling will not suffice in such contexts.
Retained jurisdiction is for recalibrating decreed plans based on operational experience, not for curing proof defects in the initial adjudication.
Pretrial stipulations cannot bind the court on the ultimate legal question of injury.

In the broader Colorado water law landscape, Town of Firestone reinforces a disciplined, evidence‑driven approach to new municipal groundwater development in over‑appropriated basins. It will likely prompt earlier and more granular engineering work and sharpen the focus of augmentation plan trials on well‑specific hydrologic realities to ensure protection of senior rights.