Reach one extends from the confluence of St. Vrain Creek with Boulder Creek, upstream to the eastern corporate limits of the City of Longmont. This portion of the creek has been realigned over time through numerous sand and gravel mining sites. During the September 2013 flood, the St. Vrain Creek left its channel and entered reclaimed and active gravel mining sites. Sediment was deposited along the southern bank of the creek. Although the new flowpath does not adversely affect infrastructure, the stream is in a state of disequilibrium and continues to change in an attempt to find a stable form.
Sandstone Ranch Reach
The Sandstone Reach follows St. Vrain Creek from County Line Road downstream (eastward) about 2.5 miles to the point where the St. Vrain meets Boulder Creek near Highway 119. During the September 2013 flooding, floodwater flows through this area caused the St. Vrain Creek to jump its banks and create a new channel. The City has hired L and M Enterprises, Inc., to complete construction work within the reach. Construction began at the end of 2016 and will continue through 2018. Activities in the Sandstone area will focus on bank stabilization and restoring the St. Vrain Greenway Trail.
The City of Longmont has selected a concept for the reach that:
Minimizes construction impact to wildlife by maintaining the post-flood channel alignment
Maximizes the opportunity for nature to heal itself and future enhance this quality habitat area
Allows natural meanders and floodplain terraces to develop for naturally regenerated cottonwoods and wetlands
Reconnects the Greenway Trail to Sandstone Ranch Park.
You can find more information about the Sandstone Ranch Reach on their website and on the document linked here.