100-Year Stormwater Capacity Verification – 24-Inch City Storm Drain, S 12th Street (Gunnison, CO) Stormwater Capacity Verification – Storm Drain
Budget: $250 – $750 USD
100-Year Stormwater Capacity Verification – 24-Inch City Storm Drain, S 12th Street (Gunnison, CO)
Company: Gunnison Warehouse LLC / Colorado Real Holdings
Location: 629 S 12th Street, Gunnison, Colorado
LICENSED COLORADO CIVIL P.E.
Project Background
We are developing two industrial warehouse buildings at 629 S 12th Street, directly adjacent to 625 S 12th Street, in Gunnison, Colorado. The City of Gunnison Site Development Review (Oct 7, 2025) confirmed that our on-site stormwater management meets requirements; however, the City now requests verification of the off-site 24-inch storm drain running parallel and east of our property along S 12th Street to confirm compliance under a 100-year storm event.
Our Site Plan V15 (09/30/25) provides existing grades, setbacks, and drainage features for reference.
Scope of Work
• Perform hydrology calculations for the 100-year storm event, per City of Gunnison and CDOT design criteria.
• Determine peak flow (Q100) from the contributing drainage area along S 12th Street and our property.
• Conduct hydraulic capacity analysis of the 24-inch line (slope, flow velocity, Manning’s n).
• Prepare summary tables showing inflow, outflow, slope, and pipe capacity vs Q100.
• Provide a schematic or drainage basin map identifying runoff flow direction and connection to the City main.
• Deliver a sealed PDF report or memo suitable for City submission.
Deliverables
• Engineering memo (PDF) with full hydrology & hydraulics calculations.
• Drainage basin map (CAD or PDF).
• Spreadsheet or model file (Hydraflow, HEC-RAS, StormCAD, or Civil 3D Hydrology).
Site Information
• Address: 629 S 12th Street, Gunnison CO 81230
• Adjacent pipe: 24-inch City storm drain (east of parcel, along S 12th Street).
• Elevation data: Provided on Site Plan V15 (09/30/25) – PDF available.
• Zoning: Industrial (per City of Gunnison LDC).
• Timeline: Completion within 7 days of award.
Preferred Qualifications
• Licensed Civil Engineer (PE); Colorado familiarity preferred.
• Experience with City of Gunnison/CDOT stormwater design.
• Proficient in HEC-RAS, Hydraflow, StormCAD, or Civil 3D.
• Capable of producing a concise, City-ready submittal.
Proposal Requirements
• Describe relevant stormwater or drainage analysis experience.
• State software tools to be used.
• Provide an example of a similar drainage memo/report.
Company: Gunnison Warehouse LLC / Colorado Real Holdings
Location: 629 S 12th Street, Gunnison, Colorado
LICENSED COLORADO CIVIL P.E.
Project Background
We are developing two industrial warehouse buildings at 629 S 12th Street, directly adjacent to 625 S 12th Street, in Gunnison, Colorado. The City of Gunnison Site Development Review (Oct 7, 2025) confirmed that our on-site stormwater management meets requirements; however, the City now requests verification of the off-site 24-inch storm drain running parallel and east of our property along S 12th Street to confirm compliance under a 100-year storm event.
Our Site Plan V15 (09/30/25) provides existing grades, setbacks, and drainage features for reference.
Scope of Work
• Perform hydrology calculations for the 100-year storm event, per City of Gunnison and CDOT design criteria.
• Determine peak flow (Q100) from the contributing drainage area along S 12th Street and our property.
• Conduct hydraulic capacity analysis of the 24-inch line (slope, flow velocity, Manning’s n).
• Prepare summary tables showing inflow, outflow, slope, and pipe capacity vs Q100.
• Provide a schematic or drainage basin map identifying runoff flow direction and connection to the City main.
• Deliver a sealed PDF report or memo suitable for City submission.
Deliverables
• Engineering memo (PDF) with full hydrology & hydraulics calculations.
• Drainage basin map (CAD or PDF).
• Spreadsheet or model file (Hydraflow, HEC-RAS, StormCAD, or Civil 3D Hydrology).
Site Information
• Address: 629 S 12th Street, Gunnison CO 81230
• Adjacent pipe: 24-inch City storm drain (east of parcel, along S 12th Street).
• Elevation data: Provided on Site Plan V15 (09/30/25) – PDF available.
• Zoning: Industrial (per City of Gunnison LDC).
• Timeline: Completion within 7 days of award.
Preferred Qualifications
• Licensed Civil Engineer (PE); Colorado familiarity preferred.
• Experience with City of Gunnison/CDOT stormwater design.
• Proficient in HEC-RAS, Hydraflow, StormCAD, or Civil 3D.
• Capable of producing a concise, City-ready submittal.
Proposal Requirements
• Describe relevant stormwater or drainage analysis experience.
• State software tools to be used.
• Provide an example of a similar drainage memo/report.