City hears plan to expand Casper Aquifer monitoring network; initial baseline testing estimated at about $150,000/year

Laramie — Consultants from Trihydro Corporation presented the City Council with a plan to formalize and expand monitoring of the Casper Aquifer, proposing a five‑year baseline sampling program, continued monitoring of about 10 existing wells and a set of additional sentinel and gap‑filling wells around production fields and potential contaminant sources.

The work would establish a water‑quality baseline for the Casper Aquifer within the city’s protection area, develop a sampling and analysis plan and identify wells that could serve as early warning or sentinel sites upstream of production wells, consultants said. Ryan Athey, a consultant with Trihydro Corporation, told the council the effort builds on the Casper Aquifer protection plan adopted earlier and “would develop that frequency and time frame” for regular monitoring of existing wells and any newly installed points.

Why it matters: The monitoring network is intended to give city water managers earlier data about groundwater quality and hydrologic connections so they can identify changes and, where possible, take operational steps — for example changing which production wells are pumped — before contaminants reach the city’s production wells. Council members repeatedly framed the project as preventive: collecting a robust baseline makes it easier to spot and respond to anomalies and to seek outside funds for investigations if contamination appears.

Most important details

- Program design and scope: Trihydro recommended quarterly sampling during an initial roughly five‑year baseline period across a broad set of wells (the consultant described roughly 25–30 wells as the near‑term sampling inventory), with the option to reduce the number of wells and analytes after the baseline period based on observed trends.

- Existing monitoring points: The consultant identified about 10 wells the city or partners monitor now (for water levels and some sampling) that would form the backbone of a formal monitoring network; additional existing wells monitored by Mountain Cement and others could be used as downstream or fault‑zone monitoring points.

- New monitoring wells: Trihydro suggested drilling a small number of new wells to fill spatial gaps and to provide sentinel coverage upgradient of production wellfields (the consultant identified a proposed Turner well and a Telephone Canyon/I‑80 well among priority candidates). New wells near higher elevations would be deeper and more expensive than shallower wells nearer town.

- Sampling and analytes: Quarterly sampling for an extensive suite of analytes was proposed during the baseline period; the consultant recommended less frequent testing for expensive analyses (pesticides/herbicides) and targeted follow‑up sampling when total petroleum hydrocarbons (TPH) or other broad screens indicate a potential hit.

- Costs and schedule: Trihydro estimated roughly $150,000 per year for the initial sampling program (sampling labor, lab analysis and supplies) when sampling 25–30 wells quarterly. The consultant said ongoing costs could be lowered after the baseline period — potentially to around $50,000 per year — by reducing analyte lists and sampling frequency. Drilling cost guidance cited by Trihydro was roughly $200–$250 per foot; shallower infill wells were estimated at $20,000–$30,000 each while deeper outcrop wells could be on the order of $100,000 each.

Council discussion and staff context

Council members pressed on how the data would be used, what could be done if contamination were detected, and who would pay. The city manager reviewed current budget lines tied to aquifer protection and told the council the adopted biennial budget includes $326,546 in the water rights section to cover Trihydro work and drilling costs if the council moves forward, $25,000 for a hazmat/spill response plan and $125,000 in a capital project fund intended to support monitoring near I‑80 rights of way. The manager characterized ongoing sampling costs as an operations expense that would need to be funded in future budgets if the council chooses to continue the full program after the baseline period.

Councilor questions also covered hydrogeologic connectivity and aquifer capacity. A consultant summarized the Casper formation as interbedded sandstone and limestone with faults and fractures that can provide preferential flow paths; he estimated saturated thickness varying by location and said he had not calculated a firm long‑term volumetric capacity but noted the aquifer has historically provided production wells that the city has relied on during surface‑water shortfalls. Hydrogeologist Chris Moody, speaking during public comment, said he has worked on the aquifer since 1993 and encouraged council members to take an on‑the‑ground tour to better understand geology and vulnerability.

What the council directed or decided

No formal motion or vote was taken during the presentation. Councilors asked for clarification and budget context; staff provided those numbers and flagged that some of the one‑time and capital funds to pay for consulting and initial drilling already appear in the adopted biennium budget. The presentation concluded with staff and council indicating interest in next steps (finalizing a sampling plan and prioritizing well locations) but no formal action was recorded.

Ending

Council members and staff discussed scheduling follow‑up and public outreach; multiple councilors expressed interest in the planned aquifer field tour and in considering a reduced recurring sampling schedule after an initial baseline period. The council moved on to the next work session item, mosquito control.