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Letter from Audubon Society 

TO: Boulder City Council
SUBJECT: Proposed Annexation at 6500 Arapahoe Road

Members of the City Council,


The Board of Directors of Boulder County Audubon Society (BCAS) submits the following comments regarding the property at 6500 Arapahoe Road, specifically the proposed annexations and Intergovernmental Agreement (IGA) for the purpose of
constructing an affordable housing modular factory.


We are concerned about the potential impacts of the proposed annexations and factory development on Sombrero Marsh, and we contend that protection of the marsh and adjacent open space is of the utmost importance. Sombrero Marsh is unique and valuable, as one of only two naturally occurring water bodies on the plains of Boulder County, the other being Little Gaynor Lake. Both are prairie playas, which have supported shorebird and other water-dependent bird, mammal, and amphibian communities for thousands of years, including long-billed curlew (now extirpated from Boulder County) and northern leopard frog. The natural significance of Sombrero Marsh is clearly recognized in the Boulder Valley Comprehensive Plan, the Boulder County Comprehensive Plan, and the City of Boulder Open Space and Mountain Parks Visitor Master Plan (VMP). The VMP designated Sombrero Marsh as a Habitat Conservation Area. As a rare alkali marsh, Sombrero Marsh provides essential habitat for shorebirds, wading birds, and diving birds. It is a vital spring and fall stopover for migrating birds along the Rocky Mountain Flyway to rest and feed. The marsh supports a diversity of microorganisms, vertebrates, and invertebrates that provide an important food source for resident birds and other animals. In addition to the immense natural values of the marsh, the educational value is exceptional. Thorne Nature Experience, located at the marsh and operating since 1954, provides the only on-site prairie learning experience for children in Boulder County. The success of the extensive array of programs offered depends on the health of the marsh and the numerous organisms it supports.
BCAS recognizes the importance of the proposed modular homes and student training to the community. At the same time, we ask that Council ensure that all feasible alternate sites have been thoroughly explored. If the project moves forward at 6500 Arapahoe Road, we urge Council to prioritize protection of the unique and irreplaceable natural and educational values of Sombrero Marsh. To that end, we support the recommendations made by OSBT Chair Karen Hollweg on behalf of OSBT, submitted verbally and in writing for the November 17, 2022 Council meeting. Additionally, BCAS offers the following specific measures to minimize impacts to Sombrero Marsh and surrounding Open Space lands:


1. Noise - Because of the importance of sound in sustaining birds, insects, and other organisms at Sombrero Marsh, we support the noise mitigation measures included in the IGA which include the City hiring an acoustical engineer to understand potential impacts to neighbors and Sombrero Marsh.  In addition, BCAS strongly recommends that the annexation agreement include implementation of recommendations the engineer may make to minimize noise impacts to the marsh, and ongoing assessment of such measures to verify that the desired results are achieved in the short and long

2. Lighting - We support the inclusion of lighting requirements in the annexation agreement to minimize light pollution and comply with Boulder’s Dark Sky ordinance.


3. Site drainage – Surface water drainage from the developed site and access roads should be contained onsite or conveyed directly into the City’s sewer system without impacting the adjoining OSMP land.


4. Surface disturbance – No surface disturbance should be permitted on OSMP lands for water/sewer lines, electrical lines or roadways. No staging or dumping of construction material or debris onto OSMP land should be

5. Access to site – Access should be from Arapahoe Road on 65th Street, instead of 63rd Street where the road is within10 feet of the boundary of Sombrero Marsh Open Space. This change would reduce impacts to the marsh from dust deposition, pollution from vehicular fluids, and disturbance to the marsh and its inhabitants from additional vehicle traffic during factory construction and operations.


Thank you for your consideration.
BCAS Board of Directors
cc: Boulder Valley School District Board of Education

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