Monday, March 28, 2016

Historic Dams: Juggling history, energy, ecology and liability

It is with mixed feelings that I see the Bloede Dam in Patapsco State Park removed as early as next month.

For sure, there have been public hearings and an environmental impact analysis. Signs were posted long enough. I never registered an objection, probably because whatever objection I have is more emotional and doesn't withstand rational argument.
Bloede dam as seen from the Howard County side of the Patapsco River

I like to hear the water crashing down the 26.5' drop audible from some distance and then watch the raw power of it close-up from the adjacent trail. The fluctuating levels of energy in the different seasons, water volume varying from an impressive waterfall to just a measly trickle, the drastic shift from the complacent almost still water above the dam to the rush of a rocky mountain stream below it.

Then there is my own history: I grew up in a factory town in which the dominant employer was a water turbine manufacturer, my dad worked there and so did I for a summer job. I learned about the various turbine types and was told that hydro-electric energy is clean energy. Bloede Dam is named after a German born engineer who was president of the nearby Avalon waterworks. In 1904 a new type turbine was installed submerged inside the spillway inside the dam, reinforced concrete structure, all very innovative at the time. However, the experiment failed when the silty Patapsco gummed the the turbines up according to some sources. Others say the power plant, which had been constructed to provide energy to outlying areas not served by the main power company, fell victim to the corporate buy-out by Consolidated Gas Electric Light and Power (later BGE, now Constellation) which bought the facility in 1912 and closed in 1924 because other bigger plants provided enough energy elsewhere.

Either way, the dam has not produced any electricity since 1924. In 1972 hurricane Agnes ransacked the Patapsco Valley and in its wake also gave the final blow to the installations still present when it damaged the head-houses beyond repair and the dam interior had to be gutted as well.  In 1992 a fish ladder had been constructed to allow fish to go upstream for spawning, but experts say that the ladder mostly doesn't work as intended.
Overview Plan

Certainly, there is nothing left to turn back on. Yet, anybody watching the water drop can see that a lot of energy goes to waste right now that may be quite in the same range as what a wind turbine may produce. But the question whether the power of Maryland's streams could once again be part of clean energy production has not even been asked, possibly because hydro-electric energy obtained from dams is not considered all that green anymore.

Environmentalists across the country have overseen the removal of those types of dams to return rivers to a more natural state. (62 dams were removed in 2015 alone). Two damns have been already removed at the Patapsco River in other locations (Union Dam and Simkins Dam).

The massive amounts of sediment (312,000 cubic yards or 26,000 dump trucks full) behind the Bloede dam are expected to naturally deposit downstream in what is called "passive sediment management". DNR expects up to 7' sediment below the damn, certainly a drastic change of the current riverbed characterized by rocks and granite blocks between which water rushes like in a mountain stream. A lot of this sediment will, no doubt also wind up at the already silted Middle Branch, maybe a matter in which the Port Covington planners should be interested.
The Patapsco downtstream from the dam, earlier this year
(photo: ArchPlan Inc.)

As part of the dam removal an exposed 42" sewer line conveniently following gravity at the edge of the riverbed will be relocated underneath the Grist Mill trail, still directly next to the river and once again under threat should another Agnes hit the area. The overall impacts on the river valley that come from all this construction will be massive and include among other things the removal of about 4 acres of forest, the extended closure of the popular river trail and about a about 10 year recovery period. In the words of DNR's own presentation:
Areas below the dam will become covered with sediment, some areas immediately downstream of the dam could be as high as 7 feet deep for short periods of time.
Sediment will bury favorable fish and benthic organism habitats for several months to several years. The areas closest to the dam will be hit the hardest, but will also recover the quickest.
-Impacts will change as sediment moves through the river. Not all impacts will occur simultaneously, and some areas will have a chance to recover while new areas are temporarily impacted. Areas behind the dam will begin evacuating sediment immediately following the removal of the dam. The evacuation of the impounded sediment is expected to take 1 to 7 months depending on how much and how frequently we get rain events following the removal. This area will also be the first area to recover and to be recolonized by fish and benthic organisms. Areas that were previously deep water habitats with sand and mud bottoms will return to swift water habitats with more favorable cobble and boulder substrate.
-Impacts to areas downstream following dam removal may disrupt spring trout stocking, especially for the first year following removal.
It is difficult for lay people to determine if the cost benefit analysis warrants the significant intervention. Certainly, the balance of the pros and cons depends on what set of issues gets the highest priority. Since the matter is handled by DNR, the arguments are largely environmental, even though DNR has closely collaborated with with historic preservationists and the Patapsco Valley Heritage Greenway non-profit.
Bloede Dam 1907 with headhouses

Turbine unit of Bloede Dam
As a result a small portion of the dam is considered for preservation on the Howard County side and some observation platforms and explanatory panels are supposed to be installed.

The three main arguments for the dam removal are a mix of environmental and human centric:
1. the fish
2. the river
3. swimmer safety (several people drowned when swimming in the pool below the current dam)

The somewhat unhappy mix of ecology, history, economy and liability issues is quite visible in an article of American Rivers, the group that also had prepared the initial "Alternatives Analysis" in 2012:
While the primary driver for this restoration effort is the opening of more than 65 miles of spawning habitat for migratory fish, safety and the need for ongoing maintenance are just as critical at this site.Removal of the Bloede Dam is an investment in Maryland’s future. It solves a critical infrastructure issue that has plagued the state since at least the 1980’s— costing Maryland millions of dollars in repairs, studies, and staffing over time. If the dam remains in place, the cost of repairs needed to comply with Maryland Dam Safety requirements could exceed $1 million. Removing the Bloede Dam enables the restoration of a natural, resilient river system and eliminates any future financial obligations by the State for repairs and long-term maintenance.Located within the Patapsco Valley State Park, one of the most popular state parks in Maryland, the dam is also an attractive nuisance that has played a significant role in more than nine deaths and untold injuries since the 1980s, including two in the last two years. (full article)
Careless people like these have caused many rescue actions and unfortunately
also have become victims of drowning in the whirl below the dam
The benefits as described by DNR
When removing a dam, there are many long-term positive benefits that you can expect to see, they include:
• Healthier populations of native fish species.
• Increase in the diversity of aquatic insects.
• Cooler, oxygen rich waters that fish thrive in.
• Safer recreational opportunities.
• A more scenic, natural setting.
One thing is sure: For contemplative weekend hikes I will have to see out other areas for a good while.

Klaus Philipsen, FAIA

DNR website about the dam
2012 Alternatives Analysis (American Rivers)
DNR Open House posters
DNR Responses to public concerns
DNR biochemicals report
DNR sediment memo
American Rivers article about Bloede Dam

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