Agenda Date: 07/02/2019
Subject:
Title
Resolution 29-2019: Granting drainage easements on the Cooley Lake property for the Wild Plum Subdivision
Body
|
Prepared by: |
Anastasia Urban, Development Services Manager |
PURPOSE:
Does city council support granting drainage easements on the Cooley Lake property for the Wild Plum Subdivision?
PRESENTATIONS:
Staff Presenter(s): Anastasia Urban, Development Services Manager, Department of Public Works
Additional Presenter(s): N/A
SUMMARY:
The Wild Plum Subdivision is a 105-acre, 95 lot single-family development located in the Town of Columbine Valley, directly west of the Littleton city boundary, and directly adjacent to Cooley Lake. The Cooley Lake property is owned by the City of Littleton and managed by South Suburban Park and Recreation District (SSPRD) and is part of the South Platte Park natural area which serves as a wildlife habitat. Access to Cooley Lake is limited to guided access only. A location map is provided below for reference.
Prior to subdivision the property was operated as a farm and horse pasture, which had eight storm water discharges directly to Cooley Lake. The Wild Plum Subdivision has been reviewed and approved by the Town of Columbine Valley and the storm water infrastructure design is consistent with the Urban Drainage and Flood Control District (UDFCD) design criteria to provide both storm water detention and storm water quality treatment. This design requires two overland spillways and four pipes/underdrains connected to Cooley Lake. As Cooley Lake is owned by the City of Littleton, easements need to be granted for the construction of these facilities.
PRIOR ACTIONS OR DISCUSSIONS:
On June 26, 2018, this topic was presented at a council study session in preparation of a formal city council agenda item. As Cooley Lake and the surrounding area is a high-quality natural area, concern of perpetual maintenance and the water quality of Cooley Lake was raised. It was also discussed that water quality monitoring should be considered. Subsequent to the study session, staff further discussed and evaluated these items with the Town of Columbine Valley and Urban Drainage and Flood Control District (UDFCD).
ANALYSIS:
Staff Analysis
Due to the sensitive nature of Cooley Lake, the storm water pond was designed to significantly exceed the required water quality area, where 4,077 square feet (s.f.) of filter area was required; however 78,710 s.f. of filter area was provided. Additional design details with the subdivision provide secondary storm water treatment throughout the subdivision by utilizing UDFCD best practices, and disconnecting impervious areas - meaning designing site grading to drain impervious areas to vegetated and landscape areas to filter the runoff prior to draining to the treatment ponds. A summary of the storm water design is provided as Attachment 1 for reference.
The storm water pond will be maintained by the Wild Plum Metropolitan District (Metro District) that has developed an on-going maintenance plan (Attachment 2), which also includes restrictions on the use of fertilizers and pesticides around the area of the pond. To address the issue of on-going maintenance if the Metro District were to fail in adequately maintaining the storm water facility, the Town of Columbine Valley amended its IGA with the Metro District such that the Town of Columbine Valley shall have the right to perform necessary work.
Overall water quality has been addressed through the combination of storm water facility design specifications and construction, the pond maintenance plan, and commitment by the Town of Columbine Valley to undertake maintenance responsibility in the event of Metro District default. Additionally, due to the design of the pond, discharges from the underdrains will be infrequent and difficult to measure through water quality sampling during runoff events since the facility is designed to infiltrate into the ground. The storm water design considerations together with the maintenance provisions are consistent with storm water quality best practices to proactively manage storm water runoff and overall water quality.
Council Goal, Objective, and/or Guiding Principle
Anchored in the features that make Littleton a truly special place and in the shared priority of parks, trails, and open space, including water ways.
Fiscal Impacts
There is no direct financial impact to granting the easements. Construction of the storm water facilities will be paid for by the developer of the Wild Plum Subdivision.
Alternatives
If the easements are not granted, the storm water needs to be rerouted, which is not a best practice. The storm water outfalls have been reviewed for compliance with storm water regulation and will have minimal impact to Cooley Lake. By granting the easements, this allows the water to continue to drain to its natural path, which is a best practice.
STAFF RECOMMENDATION:
Staff recommends approval of the grant of drainage easements and approval of Resolution 29-2019.
PROPOSED MOTION:
Proposed Motion
I move to approve the resolution granting drainage easements on the Cooley Lake property for the Wild Plum Subdivision.