Introduction
1.1 Authorization
This report was authorized by the Urban Drainage and Flood Control District (UDFCD) under joint sponsorship with the City of Arvada under the March 2014 agreement regarding “Major Drainageway Plan for Leyden Creek”, Agreement No. 14-03.06. Notice to proceed for Agreement No. 14-03.06 with ICON Engineering, Inc. was provided by UDFCD on March 26, 2014. Although not a sponsor, Jefferson County was a significant stakeholder and participant in this study.
1.2 Purpose and Scope
The purpose of this study is to provide updated hydrologic information for Leyden Creek. The watershed is bounded to the south by the Ralston Creek watershed, to the north by both Big Dry Creek and Little Dry Creek watersheds. The majority of the Leyden Creek watershed is located within the City of Arvada with the remaining areas lying within unincorporated Jefferson County.
The following is a summary of the scope of work for this study:
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Coordinate meetings with UDFCD and project stakeholders
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Obtain and review previously developed hydrologic information
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Review and provide adjustments to land use parameters based on obtained land use, zoning maps
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Determine subwatershed boundaries and parameters
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Develop existing and future conditions hydrologic models utilizing the UDFCD Colorado Urban Hydrograph Procedure (CUHP) v.1.4.3 spreadsheet and the U.S. Environmental Protection Agency’s Storm Water Management Model (EPA SWMM) v. 5.0.022 for the 2-, 5-, 10-, 25-, 50-, and 100-year recurrence intervals
1.3 Planning Process
The planning process began with reviewing previous studies for the Leyden Creek watershed. Hydrology was originally developed as part of Ralston/Leyden Creek Major Drainageway Plan dated September 1977. An update to the hydrology was completed prior to the Ralston Creek – Leyden Creek FHAD dated June 2004.
Progress meetings were held to discuss the project status and methodology with stakeholders. Minutes for all meetings held during the project can be found in APPENDIX A - Project Correspondence (PDF version only).
March 20, 2014 Project Kickoff Meeting: The project sponsors were introduced and identified. An introduction to the project to understand goals for the Leyden Creek Major Drainageway Plan was provided.
May 5, 2014 Progress Meeting: The project status was presented. This meeting reviewed land use within the watershed and approach for detention, including Leyden Lake. Follow up questions regarding the lake’s outlet elevations resulted in survey being completed by the City of Arvada’s surveyors.
August 13, 2014 Hydrology Review / Alternative Kick-Off Meeting: Comments provided by the public and project sponsors were reviewed. The project team reviewed the Hydrologic Engineering Center River Analysis System (HEC-RAS) model that will be utilized during the project. Key locations within the watershed were discussed for possible alternatives.
September 24, 2014 Croke Canal Alternative Analysis: The project team met with a representative from the Farmers Reservoir and Irrigation Canal Company (FRICO) to discuss alternatives for the Leyden Creek crossing with the Croke Canal.
December 1, 2014 Alternative Analysis Progress Meeting: The project team discussed alternatives and evaluated which alternatives best matched the project goals.
January 27, 2015 Citizen’s Review Committee Meeting: The project team met with three residents of Cameo Estates, Jennie Ridgley, Jonathan Nelson, and Kevin Klinkerfues to discuss their comments on the DRAFT Alternative Analysis Report.
February 17, 2015 Public Meeting: A public meeting was held at Van Arsdale Elementary School to discuss the recommended plan and gather community input.
September 15, 2015 Conceptual Design Progress Meeting: The project team met to discuss the comments on the DRAFT Conceptual Design Report.
1.4 Mapping and Surveys
Geographic Information System (GIS) layers were collected from the City of Arvada and Jefferson County. The layers provided included city and county boundaries, storm sewer information, zoning and parcel data.
Project mapping was based on regional LiDAR mapping with the following attributes:
Geographic Area: Colorado, Denver Metropolitan Region
Coverage: Denver Metropolitan Region, approx. 947 sq. mi.
Capture Date: Fall 2013 – Spring 2014
Collection Resolution: 0.7 meter ground sampling distance
Horizontal Datum: NAD 83
Vertical Datum: NAVD1988
A combination of aerial imagery was utilized on the project. Environmental Systems Research Institute (ESRI) resource center which provides 0.3 meter resolution within the continental United States was used along with 1 meter resolution 2012 aerial imaginary provided by UDFCD.
The City of Arvada survey staff performed a survey on the spillway for Leyden Lake as part of this study. Based on discussions with project sponsors, no other structures were surveyed; however ICON completed field measurements on the Ralston Valley High School and at Lamplighter Park ponds.
1.5 Data Collection
Previous reports for the study area were obtained from multiple sources. Previous FHAD and MDP reports were obtained through UDFCD’s Electronic Data Management (EDM) system. The Flood Insurance Study (FIS) was obtained through the Federal Emergency Management Agency (FEMA) website. The Water and Earth Technologies (WET) reconstruction report and City of Arvada Comprehensive Plan was accessed from the City of Arvada’s website. All other documents were provided by project sponsors. Reports collected are referenced in Table 1-1 below.
Table 1-1: Data Collected
| Document Title | Date | Author |
|---|---|---|
| Major Drainageway Planning Ralston/Leyden Creek | September 1977 | Wright-McLaughlin Engineers |
| Ralston Van Bibber and Leyden MDP | February 1986 | Wright Water Engineers |
| Flood Control Improvements for Leyden Lake Dam | December 2001 | URS Greiner Woodward Clyde |
| Hydrology Report Ralston/Leyden Creeks | April 2003 | Boyle Engineering Corporation |
| Flood Hazard Area Delineation Ralston Creek-Leyden Creek | June 2004 | Boyle Engineering Corporation |
| Church Ditch 82nd and Quaker Street Leyden Crossing Construction Drawings | December 2013 | SM&RC Structural Engineers Inc. |
| Ward Road Extension Preliminary Design | January 2014 | Atkins |
| Flood Insurance Study - Jefferson County, Colorado | February 2014 | Federal Emergency Management Agency |
| September 11-13, 2013 Arvada Flood Event Reconstruction and Documentation | March 2014 | Water & Earth Technologies |
| Arvada Comprehensive Plan | October 2014 | City of Arvada |
1.6 Acknowledgments
This report was prepared with the cooperation of the UDFCD, the City of Arvada, and Jefferson County. The representatives who were involved with this study are listed in Table 1-2 below:
Table 1-2: Project Participants
| Name | Representing | Assignment |
|---|---|---|
| Shea Thomas, P.E. | UDFCD | Senior Project Engineer, Master Planning Program |
| Patrick Dougherty, P.E., CFM | City of Arvada | Special Projects Engineer |
| John Conn, P.E. | Jefferson County | Department of Transportation |
| Craig D. Jacobson, P.E., CFM | ICON | Principal-in-Charge |
| Brian LeDoux, P.E., CFM | ICON | Project Manager |
| Jeremy Deischer, E.I. | ICON | Project Engineer |