Case Study: Boulder Creek, Colorado

Case Study Summary

Overall Project Goal: Restore the full use of the creek reach as a warmwater fishery, create recreational opportunities, and ensure the effectiveness of capital improvements to the Boulder wastewater treatment plant in lowering un-ionized ammonia levels.

Restoration Techniques and Parameters of Concern: See table below.

                         ----------Parameter of Concern----------



Restoration Technique/      DO    Sediment



Functional Attribute      Levels  Loadings  Temperature  pH  NH3







==============Riparian Zone and Habitat Restoration==============







Restore reaeration



     potential              u         o           o      ud   d



Stabilize stream



     banks                  u         d           d       d   d



Construct wetlands          u         d           o       d   d



Reroute irrigation



     flow                   u         d           d       d   d



Increase channel depth,



     undercut banks,



     and narrow stream



     width                  u         o           d       d   d







==============Capital Improvements at Boulder WWTP==============







Solid and liquid



     waste treatment        u         o           o       o   d



Nitrification



     trickling filter       u         o           o       o   d

Highlight on Techniques to Address Degradation of Riparian Zone and In-Stream Habitat: A four-phase ecological restoration plan was necessary to ensure that capital improvements to the Boulder wastewater treatment plan were sufficient to reduce levels of un-ionized ammonia to meet state standards in the creek. The restoration plan had a number of complementary elements which reinforced one another. For example, the riparian zone in a cattle-grazing area was fenced off to allow revegetation efforts to take hold. A number of other stream-bank stabilization efforts were undertaken, such as construction of rock/willow jetties to break up erosive currents. The plan featured the construction of new wetlands and the protection of existing wetlands acreage to reduce the impact of irrigation return flows and lower sediment loadings from run-off.

For a more complete project description, including techniques to address additional parameters of concern, refer to Chapter 6.