2020-01 - Frederick and Dacono Outfall System Plan

The current Southwest Weld County Master Drainage Plan (MDP) was completed by Anderson
Consulting Engineers, Inc. (ACE) in 1999. The 1999 MDP covers two (2) watersheds (drainage
basins) identified as intersecting the 1999 Planning Area Boundaries (PABs) of the Town of
Frederick, Town of Dacono, Town of Firestone, and the Town of Erie. After development of
existing and future condition hydrology, the 1999 MDP presented a suite of proposed
improvements to solve existing and future drainage problems at major road crossings and in
areas where development was present in 1999.

During the last 20 years development has continued; creating the need for additional detention
and stormwater improvements. Additionally, the Towns and their private partners have
completed numerous regional improvements, some of which were originally identified in the
1999 MDP. Development pressures have now begun in areas where drainage improvements
were not previous planned and in other areas where the need for future improvements have
only recently been identified. For these reasons, the Towns of Frederick and Dacono have
requested updates to the 1999 MDP and the evaluation of several new watersheds located
within their respective current PABs as shown in Attachment A Figure 1 Study Area Map.

Additional considerations for updating the 1999 MDP include: a) the NOAA rainfall data were
updated in 2013; b) hydrologic software and guidelines have been updated and revised since
1999; c) both Frederick’s and Dacono’s Planning Area Boundaries (PAB) have expanded since
1999; and d) since the 2013 Flood in Northern Colorado, construction costs have increased
dramatically; bringing into question the existing identified project costs and the finance plans’
ability to fund currently identified improvements.