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City of Casper briefs council on stormwater planning, council presses on subsurface and development risks
Summary
City engineers reviewed the 2013 stormwater master plan and the city's development-review process; councilors raised concerns about aging manuals (1983 design manual), subsurface/site-specific geotechnical risks, and how the city protects residents when private development and covenants change.
City engineering staff briefed council on the city’s stormwater planning and the process for reviewing private developments on Tuesday.
The presentation described the review workflow: applicants submit site plans or subdivision applications to planning; staff circulate complete applications to relevant departments and agencies; and engineering evaluates existing site features, proposed changes, and conformity with the stormwater master plan (2013) and the city’s stormwater-design manual (1983). The staff explained the use of hydrologic and hydraulic models (modified rational method and HEC‑RAS) and the typical thresholds that trigger a detailed drainage study (generally when a proposal changes more than 10,000 square feet or materially alters runoff characteristics).
Engineers said required materials for a drainage study include a professional engineer’s stamp, pre- and post-development flow calculations for 10‑ and 100‑year storms, capacity analysis of downstream systems, and geotechnical investigations when subsurface or groundwater issues are likely. Staff noted regional detention ponds that the city manages and private detention areas that remain the developer’s responsibility. The master plan is used as a high-level guide; site-specific geotechnical reports are expected to identify subsurface risks and mitigation measures such as on-site detention or special foundation work.
Councilors pressed whether the master plan sufficiently addresses subsurface or groundwater issues raised by residents in areas such as Eagle Valley (sometimes referenced in discussion). Engineering staff said the master plan focuses on basin-level drainage and surface-runoff modeling; subsurface and groundwater concerns are typically addressed via site-specific geotechnical investigations and engineering recommendations, which the city reviews and comments on during permitting.
Councilors asked how the city can protect residents when private covenants change or when developers seek to alter land use; staff said the city’s role is to ensure safe development that conforms to codes, to require necessary studies and permits, and to identify required remediation where a review shows potential risk. Staff also noted the master plan identifies more than $50 million in capacity projects to accommodate build-out, and updates to the plan are considered when growth or funded capacity projects justify an update.
Council requested more specific review and briefings if the Eagle Valley developer returns with a new application; staff said they would provide targeted information and respond to issues raised in public comment and technical reviews.
