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Case Study: Boulder Creek, Colorado

Case Study Summary

Considerations for Using Ecological Restoration: Elevated Concentrations of Un-Ionized Ammonia

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


     trickling filter       u         o           o       o   d

u means that the restoration technique increases water quality parameter;
d means that the restoration technique decreases water quality parameter;
ud means that site-specific conditions can dictate increase or decrease in parameter;
o means that the restoration technique has a negligible effect on water quality parameter.

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.

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