To: Honorable Mayor and Members of Town Council
Through: David L. Corliss, Town Manager
From: Mark Marlowe, Director of Castle Rock Water
David Van Dellen, Stormwater Manager
Erik Dam, Project Manager
Title
Resolution Approving a Service Agreement with Anderson Consulting Engineers, Inc., for the Mitchell Gulch Retention Pond Improvements Project [Mitchell Gulch just north of Mikelson Boulevard]
Body
________________________________________________________________________________
Executive Summary
The purpose of this memo is to request Town Council approval of a Resolution approving the Services Agreement with Anderson Consulting Engineers, Inc. for the Mitchell Gulch Retention Pond Improvements Project (see Attachment A). The scope of work generally includes engineering design, surveying, geotechnical investigation, alternatives analysis, dam construction and environmental permitting, subsurface utility engineering, conditional letter of map revision (CLOMR) preparation and submittal and easement preparation for this project, located within the Mitchell Gulch Drainageway directly north of Mikelson Boulevard (see Attachment B). The cost for these services is $407,480 plus a town-managed 10% contingency in the amount of $40,748 for a total authorization of $448,228. This is less than the amount budgeted for design, see table below. Services under this agreement are anticipated to be completed by September 2024.
|
Design |
Wetlands Mitigation |
Construction |
Total |
|
$450,000 |
$200,000 |
$2,000,000 |
$2,650,000 |
The timing of bidding and construction has not yet been determined and will be dependent largely on available funding.
Notification and Outreach Efforts
The Town will hold to open houses to present the proposed project improvements and solicit feedback. The Town will utilize the normal Town outreach channels including social media and email to notify the public of the open houses.
History of Past Town Council, Boards & Commissions, or Other Discussions
On December 19, 2006, Town Council passed, approved, and adopted a resolution approving the Mitchell Gulch Drainageway Master Plan.
Discussion
Located directly north of Mikelson Blvd on the Mitchell Gulch tributary to Cherry Creek is an existing stock pond, whose outlet structure is undersized and prone to clogging from debris. Additionally, there is not a defined overflow spillway and the pond suffers from excessive vegetation and sedimentation that has reduced the ponds volume and is not favorable for aquatic species habitat. In 2022, the State Engineer required that a water right be acquired for the pond. Castle Rock Water (CRW) invested $26,000 in securing an augmentation plan (water right) for the pond and is now required to monitor and report to the State Engineer on the plan and the water rights associated with the plan.
This design project will address these and other issues as follows:
• Evaluate recommendations in the Mitchell Gulch Watershed Master Plan for this reach of the Drainageway.
• Perform an alternatives analysis consisting of three possible solutions; (1) Lowering the pond embankment such that the dam would not be considered jurisdictional, (2) Maintaining the existing pond embankment height as it currently exists requiring jurisdictional hazard classification, and (3) Removing the existing dam embankment and pond and returning the channel to a natural condition with grade control features to stabilize the channel.
• Explore the opportunity for including regional water quality and detention storage in the pond.
• Enhance public recreational amenities for the area, including the addition of soft surface trails and fishing platforms to access the pond.
• Preserve valuable and sensitive riparian habitat and develop a comprehensive revegetation plan for areas of disturbance.
• Remap the floodplain within the project limits to reflect the proposed/constructed improvements and secure approval from FEMA.
• Design improvements to provide long-term protection of adjacent public infrastructure.
The Parks Department will be included in the Town team with respect to some of the design aspects that will be evaluated regarding use of the pond long term for recreation. The Town issued a Request for Proposals (RFP) to accomplish these objectives, and four (4) proposals were received, reviewed and ranked based on a weighted set of criteria included in the RFP document. The proposal fees for services ranged from $217,351 to $505,601. The top ranked firm from this selection process was Anderson Consulting Engineers, Inc. Their proposal and fee combination represented the best value for the Town in terms of project approach and understanding, technical expertise and scope of services provided.
Budget Impact
Funds for this design agreement will be charged to the account below and will require a budget transfer from stormwater capital account 212-4475-444.75-52 which has a budget of $2,700,000 in 2023. Additionally, there is approximately $10 million available in capital reserves to complete this project and maintain other priorities in the coming year.
|
Fund |
Account Number |
Amount |
Contingency |
Total |
|
Mitchell Gulch |
212-4475-444.75-75 |
$407,480 |
$40,748 |
$448,228 |
Staff Recommendation
Staff recommends approval of the Services Agreement with Anderson Consulting Engineers, Inc. for the Mitchell Gulch Retention Pond Improvements Project at a cost of $407,480 plus a town-managed 10% contingency in the amount of $40,748 for a total authorization of $448,228.
Proposed Motion
“I move to approve the Resolution as introduced by title.”
Alternative Motions
“I move to approve the resolution as introduced by title, with the following conditions: (list conditions).
“I move to continue this item to the Town Council meeting on _____ date to allow additional time to (list information needed).”
Attachments
Attachment A: Resolution
Exhibit 1: Services Agreement
Attachment B: Site Map