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Anatomy of a Development Proposal - Part IV Geology, Stormwater, Wetlands and Watershed

By Guest writerOn Jul 15, 2013
• In Bellingham, Planning, WWU,

Guest writer Gaythia Weis is a resident of the Puget Neighborhood and serves as the president of the neighborhood association. Her views below are entirely her own and do not necessarily represent those of the Puget Neighborhood Board.

[Note: The Ambling University Development Group documents referenced in the article below can be found at the city’s website. Click here.]

The geology of the proposed University Ridge site has some unique challenges for determining appropriate development. The eastern slope of this property is designated as having 40 to 100% slopes on the City of Bellingham geologic hazards map, raising the potential for landslides (click here). Natural springs are also mapped on or near this site. To the north are the wetlands of the Hawley Open Space.

To appropriately determine the impact of this large development on the hydrology of the watershed, I believe a full basin study of the Lincoln Creek watershed needs to be conducted. At the same time, the developer should be required to submit a variance for encroachment onto the wetlands. This would allow for a full evaluation of the impact the construction of these buildings will have on this particular wetland, and allow review of other significant watershed issues.

The height variance request implies an increase in the mass of the building over what might otherwise be allowed. Before such a variance is granted, a more in-depth soil and geologic survey ought to be obligatory.

Geologic Assessment:

On the SEPA checklist, the developer describes the site as “hilly.” I would say “steep slopes” would be a more appropriate description, and one more attune to the City of Bellingham’s maps. Especially incongruous are the developer's own requests to vacate Consolidation Avenue due to the steepness of the grade, and not to connect to Puget Street, again because of steepness. The next line item asks: “What is the steepest slope on the site?” The average slope grade for the entire site is the answer given. This is not an answer to the question as it was asked. I see it as an answer that appears an attempt to obscure the steepness of much of the site.

As noted above, the eastern slope of this property is identified as a potential landslide hazard, with 40 to 100% slopes on the City of Bellingham geologic hazards map. You can view the map here

.The Geological Hazardous Site Assessment, prepared by the firm GeoEngineers and submitted to the city, indicates they have only dug test pits to a depth of 10 to 12 feet. The geo-technical report document is specifically stamped “not for construction,” demonstrating the preliminary nature of this report. At the developer’s first public meeting at Cozier Elementary School on January 3, 2013, I raised questions as to the nature of the soils, geology studies performed and the test depths. Even then, I questioned the 12’ answer I was given. It was my understanding that after this meeting, the developers were to address questions raised. Disappointingly, no further test pit work seems to have been done; this despite the fact that the west to east cross section profile diagram for the development clearly shows cuts that will be held by retaining walls having changes in grade that are up to 17 feet tall.

In the report, the comments for TP-3, the test pit closest to the eastern boundary of the development, indicate that rapid groundwater seepage was observed at 8 and 11 feet, moderate caving was observed from 7 to 11 feet and disturbed soils were obtained from many levels of this pit. Again, this raises my concerns about the stability of the hillside. I see these test pit results as a clear indication of the need for more test pits in the upper area of this property, and they should be dug well beyond the depth that will be disturbed by construction. Ideally, the pits should also determine the depth to the bedrock of the Chuckanut Formation.

Landslides would seem to be a likely and particular risk during construction, before retaining walls can be put into place. The GeoEngineers report validates this, stating that the primary hazard will be from temporary conditions during construction. They indicate stormwater runoff prevention methods should be employed. I do not see them as addessing how such stormwater would be redirected, or cleaned, before running further downhill. They do not directly address the issue of disruption of perched groundwater aquifers and the additional volume of water from these aquifers. They do not appear to address the possible effect of these aquifers on soil stability and landslide potential. This seems to be true even though the existence of these aquifers is mentioned elsewhere. I usggest that these issues should be addressed.

The glacial till that presumably covers much of this site, as it does much of our (Puget) neighborhood, is likely composed of well-rounded glacial cobbles. There are numerous examples of landslides occurring in this material throughout Whatcom County and the Puget Sound, especially when it is wet.

In some parts of the neighborhood, the Chuckanut Formation is near the surface. Why isn't this bedrock being used as a stable anchor, particularly if heavy buildings are involved? I do not understand why the builder would not want to at least know the depth to bedrock. Stability of the site impacts the appropriateness of large scale and heavy buildings and thus is relevant to the height variance requested by the developer.

Stormwater Assessment:

Drainage from this site could create serious negative impacts on the neighborhoods and ecosystems below. The stormwater plan submitted appears to only address surface water and apparently does not recognize any potential for additional water collected as drainage from groundwater aquifers. This plan was prepared by a firm other than the one that did the geohazards work, and seems to be written independently of the geohazard findings.

It is also not clear to me that the stormwater vault and rain garden proposed by the developer will have the capacity to handle the additional flow that may come from the groundwater aquifers. This issue is not addressed by the stormwater plan, which appears to only be a fairly standard assessment of the effects of impervious surfaces. Including the groundwater could significantly increase the sizing requirements for these facilities.

Downhill from this site, it is not apparent that the stormwater management facilities and piping were designed to handle large amounts of additional flow. Already, the Parks Department has had to come out to clear an existing stormwater management facility that directly impacts the homes of some Puget neighborhood residents. In the Puget neighborhood plan, Nevada Street, in the older section between Lakeway Drive and Edwards Street, is listed as a drainage problem area. Additionally, there is an area behind a nearby commercial zone where the stormwater apparently flows through a private system. The capacity of the entire system to handle potential impacts from increasing flows needs evaluation.

While not directly related to this site, a member of Public Works has described the current condition of the stormwater retention facilities under the Fred Meyer complex as “aging,” thus having an impact on its capacity and the overall flood potential downstream. When combined with added water from the new University Ridge development, I believe that downstream consequences would be magnified.

I personally have participated in a cleanup of Lincoln Creek under the auspices of the Public Works Department. In the area of Lincoln Creek east of Lakeway Dr., and prior to its entry into park land near Fraser St., this stream has a very narrow bed. I observed areas where very little additional flow would be needed to flood wide swathes of people’s yards, or even adjacent apartments.

Wetlands and Watershed:

Under the category of water, the SEPA checklist asks if there are any surface water withdrawals or diversions. But for this development, there are also questions to be raised about groundwater aquifer withdrawals and diversions. According to the City of Bellingham geohazards map, there are a series of natural springs along this ridge. These springs likely feed the adjacent wetlands. In the construction of this facility, good engineering practices seem to necessitate draining any perched groundwater aquifers encountered in order to provide a stable platform for building. These drainages may affect the groundwater aquifers flowing into adjacent wetlands and impinge their viability. The drainage of these aquifers would also impact stormwater volumes.

The Lincoln Creek watershed is a contributor to the watershed of Whatcom Creek. The Critical Areas Assessment report for this development describes a drainage on the property of the proposed University Ridge, as being surrounded by forested species such as sword fern, stinging nettle, trailing blackberry, salmonberry, red alder and Western red cedar. The report goes on to say that this drainage then soaks into the subsurface. The importance of this drainage is discounted since it is not a natural stream. But it is a component of the Lincoln Creek watershed, one that in its current state helps to filter the water and retard its downward flow. It is not clear that a rain garden of the size indicated is an adequate replacement for a hillside forest as described here.

The City of Bellingham Wildlife and Habitat Plan describes the mouth of Lincoln Creek (where it meets Whatcom Creek) as “an important spawning area and a refugia for resident fish.” I believe this spawning area could be seriously impaired by unnatural and abnormally high floodwaters.

Conclusion:

A full, basin wide, assessment of the Lincoln Creek watershed needs to be made before this large-scale building is allowed to proceed. Additionally, more work needs to be done to assess the geology of this site before permission is granted for buildings of the mass proposed.

About Guest writer

Writer • Member since Jun 15, 2008

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