We are grateful to Alice Harkness for sharing her notes from visiting the City's November 16 Open House on the Mill Creek Daylighting initiative. (The city published this background info.)
Dear Keepers and friends of the Keepers of Mill Creek,
I went yesterday to the Daylighting meeting held by the City at Coverdale Hall. Although most of the displays in the room concerned the daylighting initiative, there were also a couple of displays concerned with the connecting tunnel/ wetland/ low-impact development (LID) proposal that the City has put forward to reduce erosion in Mill Creek. I talked at length with Kerri Robinson, the City employee present to explain these options. She’s a really nice, engaged person who was able to answer a number of the questions that have been raised by your responses to my last e-mail. So this is what I learned:
In regards to the connecting tunnel option: it would actually be done using directional digging, so there would be much less surface disruption than what I had imagined. The sites that would be disrupted (i.e. the staging sites for the digging) would be at: the outflow tunnel north of Argyll (where the pipe is set to begin); the inflow tunnel south of Whyte; and possibly (if they need to add more pipe lower down) near the lower inflow tunnel. The pipe used would be 3 meters in diameter and be placed 30 meters below ground. In regards to the maintaining of the water level of Mill Creek itself, the mechanism used would be a simple overflow arrangement. This means that this connecting tunnel could not help sustain the creek level during dry periods, it could only divert heavy flows. (There is an option the City has put out for a small wetland in the staging area north of Argyll. I don’t know if there is any thought about whether this wetland would be able to help maintain the water level of the creek.)
Some of you wondered about Fulton Creek, whether it could be returned to its original creek bed instead of its current state of being funneled into Mill Creek. Kerri said that there is so much development in that area that that is not an option.
In regards to the low-impact development option (i.e. using a variety of strategies that allow rainfall to be absorbed into the ground rather than be funneled into the sewer system) Kerri is a part of the group that is looking into this option. Her enthusiasm was really encouraging to me. I had gotten the impression from the last City meeting (Nov. 3) that this option had been all but shelved, but it turns out that the timeline for decision-making will remain open for another year. So in the meantime the LID sub-group has hired a consulting firm from Minnesota (where the climactic challenges are similar) and are considering all the options available to them for reducing the quantity of storm-water that enters the sewer system. It seems that in their perspective to imagine that they can reduce run-off levels to the point of making the connecting tunnel obsolete would be setting a (probably) unachievable goal, so they imagine a combination of connecting tunnel and LID will be the likely solution. However, the amount that they can achieve depends heavily on us - on the public’s show of support for this option. (So if you have not yet filled out the Mill Creek Water Quality Survey DO SO BEFORE THE DEADLINE TOMORROW!) She also mentioned that the City has already undertaken a number of LID solutions elsewhere in the city, so they are developing a knowledge of and trust in this alternative.
Finally, I asked Kerri the question that I set out before you in my earlier e-mail, in regards to a concern that if we keep on funneling off our rainwater, are we creating a rain shadow for the Edmonton area, especially everywhere there are expanses of buildings and pavement, that could potentially really compromise Edmonton as a sustainable, livable city? She agreed with me completely, and said that this is one of the arguments they are putting forward to the City in favor of this option.
One more clarifying point: the project of installing Oil and Grit Separators began a couple years ago and is on track to continue. They are installed underneath roads in the Mill Creek watershed area, so they do not cause any disruption to the park itself.
Best regards,
Alice
Dear Keepers and friends of the Keepers of Mill Creek,
I went yesterday to the Daylighting meeting held by the City at Coverdale Hall. Although most of the displays in the room concerned the daylighting initiative, there were also a couple of displays concerned with the connecting tunnel/ wetland/ low-impact development (LID) proposal that the City has put forward to reduce erosion in Mill Creek. I talked at length with Kerri Robinson, the City employee present to explain these options. She’s a really nice, engaged person who was able to answer a number of the questions that have been raised by your responses to my last e-mail. So this is what I learned:
In regards to the connecting tunnel option: it would actually be done using directional digging, so there would be much less surface disruption than what I had imagined. The sites that would be disrupted (i.e. the staging sites for the digging) would be at: the outflow tunnel north of Argyll (where the pipe is set to begin); the inflow tunnel south of Whyte; and possibly (if they need to add more pipe lower down) near the lower inflow tunnel. The pipe used would be 3 meters in diameter and be placed 30 meters below ground. In regards to the maintaining of the water level of Mill Creek itself, the mechanism used would be a simple overflow arrangement. This means that this connecting tunnel could not help sustain the creek level during dry periods, it could only divert heavy flows. (There is an option the City has put out for a small wetland in the staging area north of Argyll. I don’t know if there is any thought about whether this wetland would be able to help maintain the water level of the creek.)
Some of you wondered about Fulton Creek, whether it could be returned to its original creek bed instead of its current state of being funneled into Mill Creek. Kerri said that there is so much development in that area that that is not an option.
In regards to the low-impact development option (i.e. using a variety of strategies that allow rainfall to be absorbed into the ground rather than be funneled into the sewer system) Kerri is a part of the group that is looking into this option. Her enthusiasm was really encouraging to me. I had gotten the impression from the last City meeting (Nov. 3) that this option had been all but shelved, but it turns out that the timeline for decision-making will remain open for another year. So in the meantime the LID sub-group has hired a consulting firm from Minnesota (where the climactic challenges are similar) and are considering all the options available to them for reducing the quantity of storm-water that enters the sewer system. It seems that in their perspective to imagine that they can reduce run-off levels to the point of making the connecting tunnel obsolete would be setting a (probably) unachievable goal, so they imagine a combination of connecting tunnel and LID will be the likely solution. However, the amount that they can achieve depends heavily on us - on the public’s show of support for this option. (So if you have not yet filled out the Mill Creek Water Quality Survey DO SO BEFORE THE DEADLINE TOMORROW!) She also mentioned that the City has already undertaken a number of LID solutions elsewhere in the city, so they are developing a knowledge of and trust in this alternative.
Finally, I asked Kerri the question that I set out before you in my earlier e-mail, in regards to a concern that if we keep on funneling off our rainwater, are we creating a rain shadow for the Edmonton area, especially everywhere there are expanses of buildings and pavement, that could potentially really compromise Edmonton as a sustainable, livable city? She agreed with me completely, and said that this is one of the arguments they are putting forward to the City in favor of this option.
One more clarifying point: the project of installing Oil and Grit Separators began a couple years ago and is on track to continue. They are installed underneath roads in the Mill Creek watershed area, so they do not cause any disruption to the park itself.
Best regards,
Alice
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