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How do I understand the use of aerial photographs to adjust stormwater rates based on impervious surfaces?
REALLY EXTENSIVE emails have been received on this topic:
overestimates of impervious surfaces for stormwater rates
"Blischke, Michael A." <michael.blischke@gd-ais.com>
to JHieftje, JLowenstein, SRapundalo, LGreden, SKunselman, MHiggins, wwoods, MTeall, CEasthope, RJohnson, rsuarez
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Oct 10
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Councilmembers and Mayor
I am writing regarding the method used in estimating the amount of impervious surface on properties of Ann Arbor residents. These estimates are used to calculate the stormwater rates residents are paying. The method of using aerial photographs is resulting in significantly overestimating the amount of impervious surface on residents’s lots. The Stormwater rate page lists a few areas that may result in overestimates: Wood chips, shadows, and decks. In my case (see the attached image), I found that bare soil and vegetation, even when not in shadow, were counted as impervious surface. More troubling, since the pictures are taken at an angle, rather than directly overhead, they are also inlcuding the side and front of my house as impervious area, and counting some area where the roof above is also counted. This is analogous to including the area of walls and the ceiling when calculating the floorspace of a room. Further, the property lines are misregistered, so there are impervious surfaces included that are not even on my property.
All told, the impervious surface on my property was overestimated by almost 50 percent. This is a huge error. I believe the city has a moral duty to provide better estimates of impervious area. I feel it is unrealistic to put the burden of correcting these problems on the homeowners, or to even expect that all residents would be able to look at the picture provided online and be able to find the errors.
Finally, since the city is using these figures to charge residents, I believe the city also has a legal duty to not overcharge its residents. I suspect that all the photos used for calculating impervious area will all be taken at an angle, so that every lot in the city will have a significant overestimate of its impervious area. There are likely several thousand properties where the overestimates are pushing a property into the next higher payment tier, and none with underestimates. This strikes me as a case ripe for a class-action lawsuit against the city, which will cost all of us money. The longer the current estimates are used, the greater the damage will be when this occurs.
If the city is to charge its residents based on impervious area, it will need to find an accurate way of measuring that area. The method being used now is simply too inaccurate to use.
Michael A. Blischke
(734) 480-5046
Stormwater_errors.JPG
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"Hieftje, John"
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Hello:
I appreciate your concerns with the data that has been collected and I will pass this letter on to city staff who are working on this program for their information and comment.
Thank you for writing.
John Hieftje
- Show quoted text -
-----Original Message-----
From: Blischke, Michael A. [mailto:michael.blischke@gd-ais.com]
Sent: Wednesday, October 10, 2007 1:23 PM
To: Hieftje, John; Lowenstein, Joan; Rapundalo, Stephen; Greden, Leigh; Kunselman, Stephen; Higgins, Marcia; Woods, Wendy A; Teall, Margie; Easthope, Christopher; Johnson, Robert; Suarez, Ron
Subject: overestimates of impervious surfaces for stormwater rates
Councilmembers and Mayor
I am writing regarding the method used in estimating the amount of impervious surface on properties of Ann Arbor residents. These estimates are used to calculate the stormwater rates residents are paying. The method of using aerial photographs is resulting in significantly overestimating the amount of impervious surface on residents’s lots. The Stormwater rate page lists a few areas that may result in overestimates: Wood chips, shadows, and decks. In my case (see the attached image), I found that bare soil and vegetation, even when not in shadow, were counted as impervious surface. More troubling, since the pictures are taken at an angle, rather than directly overhead, they are also inlcuding the side and front of my house as impervious area, and counting some area where the roof above is also counted. This is analogous to including the area of walls and the ceiling when calculating the floorspace of a room. Further, the property lines are misregistered, so there are impervious surfaces included that are not even on my property.
All told, the impervious surface on my property was overestimated by almost 50 percent. This is a huge error. I believe the city has a moral duty to provide better estimates of impervious area. I feel it is unrealistic to put the burden of correcting these problems on the homeowners, or to even expect that all residents would be able to look at the picture provided online and be able to find the errors.
Finally, since the city is using these figures to charge residents, I believe the city also has a legal duty to not overcharge its residents. I suspect that all the photos used for calculating impervious area will all be taken at an angle, so that every lot in the city will have a significant overestimate of its impervious area. There are likely several thousand properties where the overestimates are pushing a property into the next higher payment tier, and none with underestimates. This strikes me as a case ripe for a class-action lawsuit against the city, which will cost all of us money. The longer the current estimates are used, the greater the damage will be when this occurs.
If the city is to charge its residents based on impervious area, it will need to find an accurate way of measuring that area. The method being used now is simply too inaccurate to use.
Michael A. Blischke
(734) 480-5046
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"McMurtrie, Thomas" <TMcMurtrie@a2gov.org>
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Oct 11
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Mayor and Council:
This is an interesting case. If you look at the aerial impervious area interpretations (attached), I would come to the conclusion that our system has worked fairly well. There are a few small areas in shadows that we missed, as well as a small grassy area out front. These might total a few hundred square feet, and would not change his rate. He is currently at 3908 square feet, and would have to drop to 2187 square feet to move to another tier.
I'm not sure where Mr. Blischke came up with the claim that we overstated his impervious area by 50%. Looking at the assessor's website, his building foot print is 2161 square feet -- but this does not include his driveway, sidewalk, patios, roof overhangs, or any other impervious area. We have never received any communications from Mr. Blishke asking for an adjustment to his impervious area or his rate.
Residents have made extensive use of our online imagery. We have received hundreds of requests for adjustments. Any adjustment that is made will be saved as a GIS image layer, so that in future flights, we will be able to identify those adjustments and apply them.
Please do not hesitate to contact me if you have any questions or comments.
Thanks!
Tom McMurtrie
Ann Arbor Systems Planning Unit-Public Services
P.O. Box 8647 / 100 N. Fifth Ave.
Ann Arbor, MI 48107
734.994.6581 Fax: 734.996.3064
www.a2gov.org
From: Hieftje, John
Sent: Wednesday, October 10, 2007 2:08 PM
To: 'Blischke, Michael A.'; Lowenstein, Joan; Rapundalo, Stephen; Greden, Leigh; Kunselman, Stephen; Higgins, Marcia; Woods, Wendy A; Teall, Margie; Easthope, Christopher; Johnson, Robert; Suarez, Ron
Subject: RE: overestimates of impervious surfaces for stormwater rates
- Show quoted text -
Hello:
I appreciate your concerns with the data that has been collected and I will pass this letter on to city staff who are working on this program for their information and comment.
Thank you for writing.
John Hieftje
-----Original Message-----
From: Blischke, Michael A. [mailto:michael.blischke@gd-ais.com]
Sent: Wednesday, October 10, 2007 1:23 PM
To: Hieftje, John; Lowenstein, Joan; Rapundalo, Stephen; Greden, Leigh; Kunselman, Stephen; Higgins, Marcia; Woods, Wendy A; Teall, Margie; Easthope, Christopher; Johnson, Robert; Suarez, Ron
Subject: overestimates of impervious surfaces for stormwater rates
Councilmembers and Mayor
I am writing regarding the method used in estimating the amount of impervious surface on properties of Ann Arbor residents. These estimates are used to calculate the stormwater rates residents are paying. The method of using aerial photographs is resulting in significantly overestimating the amount of impervious surface on residents’s lots. The Stormwater rate page lists a few areas that may result in overestimates: Wood chips, shadows, and decks. In my case (see the attached image), I found that bare soil and vegetation, even when not in shadow, were counted as impervious surface. More troubling, since the pictures are taken at an angle, rather than directly overhead, they are also inlcuding the side and front of my house as impervious area, and counting some area where the roof above is also counted. This is analogous to including the area of walls and the ceiling when calculating the floorspace of a room. Further, the property lines are misregistered, so there are impervious surfaces included that are not even on my property.
All told, the impervious surface on my property was overestimated by almost 50 percent. This is a huge error. I believe the city has a moral duty to provide better estimates of impervious area. I feel it is unrealistic to put the burden of correcting these problems on the homeowners, or to even expect that all residents would be able to look at the picture provided online and be able to find the errors.
Finally, since the city is using these figures to charge residents, I believe the city also has a legal duty to not overcharge its residents. I suspect that all the photos used for calculating impervious area will all be taken at an angle, so that every lot in the city will have a significant overestimate of its impervious area. There are likely several thousand properties where the overestimates are pushing a property into the next higher payment tier, and none with underestimates. This strikes me as a case ripe for a class-action lawsuit against the city, which will cost all of us money. The longer the current estimates are used, the greater the damage will be when this occurs.
If the city is to charge its residents based on impervious area, it will need to find an accurate way of measuring that area. The method being used now is simply too inaccurate to use.
Michael A. Blischke
(734) 480-5046
2355 Foxway Image.pdf
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"Hieftje, John"
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Oct 11
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Thanks Tom:
Are you going to reply to this resident or should I forward this to him?
John
From: McMurtrie, Thomas
Sent: Thursday, October 11, 2007 7:42 AM
To: Hieftje, John; Lowenstein, Joan; Rapundalo, Stephen; Greden, Leigh; Kunselman, Stephen; Higgins, Marcia; Woods, Wendy A; Teall, Margie; Easthope, Christopher; Johnson, Robert; Suarez, Ron
Cc: Hupy, Craig; McCormick, Sue; Gih, Brandi
- Show quoted text -
Subject: RE: overestimates of impervious surfaces for stormwater rates
- Show quoted text -
Mayor and Council:
This is an interesting case. If you look at the aerial impervious area interpretations (attached), I would come to the conclusion that our system has worked fairly well. There are a few small areas in shadows that we missed, as well as a small grassy area out front. These might total a few hundred square feet, and would not change his rate. He is currently at 3908 square feet, and would have to drop to 2187 square feet to move to another tier.
I'm not sure where Mr. Blischke came up with the claim that we overstated his impervious area by 50%. Looking at the assessor's website, his building foot print is 2161 square feet -- but this does not include his driveway, sidewalk, patios, roof overhangs, or any other impervious area. We have never received any communications from Mr. Blishke asking for an adjustment to his impervious area or his rate.
Residents have made extensive use of our online imagery. We have received hundreds of requests for adjustments. Any adjustment that is made will be saved as a GIS image layer, so that in future flights, we will be able to identify those adjustments and apply them.
Please do not hesitate to contact me if you have any questions or comments.
Thanks!
Tom McMurtrie
Ann Arbor Systems Planning Unit-Public Services
P.O. Box 8647 / 100 N. Fifth Ave.
Ann Arbor, MI 48107
734.994.6581 Fax: 734.996.3064
www.a2gov.org
From: Hieftje, John
Sent: Wednesday, October 10, 2007 2:08 PM
To: 'Blischke, Michael A.'; Lowenstein, Joan; Rapundalo, Stephen; Greden, Leigh; Kunselman, Stephen; Higgins, Marcia; Woods, Wendy A; Teall, Margie; Easthope, Christopher; Johnson, Robert; Suarez, Ron
Subject: RE: overestimates of impervious surfaces for stormwater rates
Hello:
I appreciate your concerns with the data that has been collected and I will pass this letter on to city staff who are working on this program for their information and comment.
Thank you for writing.
John Hieftje
-----Original Message-----
From: Blischke, Michael A. [mailto:michael.blischke@gd-ais.com]
Sent: Wednesday, October 10, 2007 1:23 PM
To: Hieftje, John; Lowenstein, Joan; Rapundalo, Stephen; Greden, Leigh; Kunselman, Stephen; Higgins, Marcia; Woods, Wendy A; Teall, Margie; Easthope, Christopher; Johnson, Robert; Suarez, Ron
Subject: overestimates of impervious surfaces for stormwater rates
Councilmembers and Mayor
I am writing regarding the method used in estimating the amount of impervious surface on properties of Ann Arbor residents. These estimates are used to calculate the stormwater rates residents are paying. The method of using aerial photographs is resulting in significantly overestimating the amount of impervious surface on residents’s lots. The Stormwater rate page lists a few areas that may result in overestimates: Wood chips, shadows, and decks. In my case (see the attached image), I found that bare soil and vegetation, even when not in shadow, were counted as impervious surface. More troubling, since the pictures are taken at an angle, rather than directly overhead, they are also inlcuding the side and front of my house as impervious area, and counting some area where the roof above is also counted. This is analogous to including the area of walls and the ceiling when calculating the floorspace of a room. Further, the property lines are misregistered, so there are impervious surfaces included that are not even on my property.
All told, the impervious surface on my property was overestimated by almost 50 percent. This is a huge error. I believe the city has a moral duty to provide better estimates of impervious area. I feel it is unrealistic to put the burden of correcting these problems on the homeowners, or to even expect that all residents would be able to look at the picture provided online and be able to find the errors.
Finally, since the city is using these figures to charge residents, I believe the city also has a legal duty to not overcharge its residents. I suspect that all the photos used for calculating impervious area will all be taken at an angle, so that every lot in the city will have a significant overestimate of its impervious area. There are likely several thousand properties where the overestimates are pushing a property into the next higher payment tier, and none with underestimates. This strikes me as a case ripe for a class-action lawsuit against the city, which will cost all of us money. The longer the current estimates are used, the greater the damage will be when this occurs.
If the city is to charge its residents based on impervious area, it will need to find an accurate way of measuring that area. The method being used now is simply too inaccurate to use.
Michael A. Blischke
(734) 480-5046
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"McMurtrie, Thomas" <TMcMurtrie@a2gov.org>
to Michael, John, Joan, Stephen, Leigh, Stephen, Marcia, Wendy, Margie, Christopher, Robert, Ron, Craig, Sue, Brandi
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Oct 11
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Mr. Blischke,
Thank you for your feedback on our stormwater rates system. I am sorry to hear about your displeasure with it.
In looking at the image for your property, I would appreciate it if you could help me understand how you came up with the 50% error figure that you stated in your letter. I see some discrepencies in the shaded areas, a small grassy area in the front of your house, and the sidewalk at the front of your property (which is part of the right of way) These alone are not close to the 50% error figure, and would not be enough to change your rate. You are currently at 3908 square feet, and would need to drop to 2187 square feet to move to another tier.
Looking at the assessor's website, it shows that your building footprint is 2161 square feet. Any other impervious areas on your property would also need to be added. This would include but not be limited to: your driveway, sidewalks on your property, patios, and roof overhangs.
If you print your attached impervious area image, and highlight areas that we have incorrectly identified, we would be happy to make adjustments. If you have questions, or would like us to conduct a site visit to help with the analysis, please call me directly at 994-6581 and we would be more than willing to arrange that.
Thanks again,
Tom McMurtrie
Ann Arbor Systems Planning Unit-Public Services
P.O. Box 8647 / 100 N. Fifth Ave.
Ann Arbor, MI 48107
734.994.6581 Fax: 734.996.3064
www.a2gov.org
- Show quoted text -
-----Original Message-----
From: Blischke, Michael A. [mailto:michael.blischke@gd-ais.com]
Sent: Wednesday, October 10, 2007 1:23 PM
To: Hieftje, John; Lowenstein, Joan; Rapundalo, Stephen; Greden, Leigh; Kunselman, Stephen; Higgins, Marcia; Woods, Wendy A; Teall, Margie; Easthope, Christopher; Johnson, Robert; Suarez, Ron
Subject: overestimates of impervious surfaces for stormwater rates
Councilmembers and Mayor
I am writing regarding the method used in estimating the amount of impervious surface on properties of Ann Arbor residents. These estimates are used to calculate the stormwater rates residents are paying. The method of using aerial photographs is resulting in significantly overestimating the amount of impervious surface on residents’s lots. The Stormwater rate page lists a few areas that may result in overestimates: Wood chips, shadows, and decks. In my case (see the attached image), I found that bare soil and vegetation, even when not in shadow, were counted as impervious surface. More troubling, since the pictures are taken at an angle, rather than directly overhead, they are also inlcuding the side and front of my house as impervious area, and counting some area where the roof above is also counted. This is analogous to including the area of walls and the ceiling when calculating the floorspace of a room. Further, the property lines are misregistered, so there are impervious surfaces included that are not even on my property.
All told, the impervious surface on my property was overestimated by almost 50 percent. This is a huge error. I believe the city has a moral duty to provide better estimates of impervious area. I feel it is unrealistic to put the burden of correcting these problems on the homeowners, or to even expect that all residents would be able to look at the picture provided online and be able to find the errors.
Finally, since the city is using these figures to charge residents, I believe the city also has a legal duty to not overcharge its residents. I suspect that all the photos used for calculating impervious area will all be taken at an angle, so that every lot in the city will have a significant overestimate of its impervious area. There are likely several thousand properties where the overestimates are pushing a property into the next higher payment tier, and none with underestimates. This strikes me as a case ripe for a class-action lawsuit against the city, which will cost all of us money. The longer the current estimates are used, the greater the damage will be when this occurs.
If the city is to charge its residents based on impervious area, it will need to find an accurate way of measuring that area. The method being used now is simply too inaccurate to use.
Michael A. Blischke
(734) 480-5046
2355 Foxway Image.pdf
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"Blischke, Michael A." <michael.blischke@gd-ais.com>
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Oct 11
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Tom
I measured the area of my house, and my sidewalk and driveway, and came up with a little over 2600 square feet. 50 percent over 2600 is 3900. Perhaps you weren’t forwarded the JPEG image I sent to the mayor and Council, so I’m including it again. It shows all the errors mentioned in my original email, labeled and color-coded.
I did not write to Council because I expected my rates to be affected. I wrote because I believe the errors in your method of estimating impervious surface will result in systematically overestimating the error, resulting in thousands of homes across the city being charged a greater rate than is appropriate. In my case, it won’t matter, because my true impervious surface area is at the low end of the tier I am in, and your errors merely bump me into the high end of the tier.
Other residents, however, may be at the high end of their tier, and the errors of the sort on my property will bump them into the next tier. Since the city is charging us based on the area, I believe the city has a duty to prevent overestimates from happening. Instead, it seems the city has a system that will systematically overestimate residents’s impervious areas, then places the burden on all of us to find those errors and complain. And who’s to say that every resident will even be capable of realizing that, for example, including the side and front of a house is an error. Even you didn’t seem to notice that.
As long as I’m writing, what level of accuracy are you expecting from your system? Have you taken a random sample of homes, and compared the estimated areas to the true areas?
Michael
From: McMurtrie, Thomas [mailto:TMcMurtrie@a2gov.org]
Sent: Thursday, October 11, 2007 9:12 AM
To: Blischke, Michael A.
Cc: Hieftje, John; Lowenstein, Joan; Rapundalo, Stephen; Greden, Leigh; Kunselman, Stephen; Higgins, Marcia; Woods, Wendy A; Teall, Margie; Easthope, Christopher; Johnson, Robert; Suarez, Ron; Hupy, Craig; McCormick, Sue; Gih, Brandi
Subject: RE: overestimates of impervious surfaces for stormwater rates
- Show quoted text -
Mr. Blischke,
Thank you for your feedback on our stormwater rates system. I am sorry to hear about your displeasure with it.
In looking at the image for your property, I would appreciate it if you could help me understand how you came up with the 50% error figure that you stated in your letter. I see some discrepencies in the shaded areas, a small grassy area in the front of your house, and the sidewalk at the front of your property (which is part of the right of way) These alone are not close to the 50% error figure, and would not be enough to change your rate. You are currently at 3908 square feet, and would need to drop to 2187 square feet to move to another tier.
Looking at the assessor's website, it shows that your building footprint is 2161 square feet. Any other impervious areas on your property would also need to be added. This would include but not be limited to: your driveway, sidewalks on your property, patios, and roof overhangs.
If you print your attached impervious area image, and highlight areas that we have incorrectly identified, we would be happy to make adjustments. If you have questions, or would like us to conduct a site visit to help with the analysis, please call me directly at 994-6581 and we would be more than willing to arrange that.
Thanks again,
Tom McMurtrie
Ann Arbor Systems Planning Unit-Public Services
P.O. Box 8647 / 100 N. Fifth Ave.
Ann Arbor, MI 48107
734.994.6581 Fax: 734.996.3064
www.a2gov.org
-----Original Message-----
From: Blischke, Michael A. [mailto:michael.blischke@gd-ais.com]
Sent: Wednesday, October 10, 2007 1:23 PM
To: Hieftje, John; Lowenstein, Joan; Rapundalo, Stephen; Greden, Leigh; Kunselman, Stephen; Higgins, Marcia; Woods, Wendy A; Teall, Margie; Easthope, Christopher; Johnson, Robert; Suarez, Ron
Subject: overestimates of impervious surfaces for stormwater rates
Councilmembers and Mayor
I am writing regarding the method used in estimating the amount of impervious surface on properties of Ann Arbor residents. These estimates are used to calculate the stormwater rates residents are paying. The method of using aerial photographs is resulting in significantly overestimating the amount of impervious surface on residents’s lots. The Stormwater rate page lists a few areas that may result in overestimates: Wood chips, shadows, and decks. In my case (see the attached image), I found that bare soil and vegetation, even when not in shadow, were counted as impervious surface. More troubling, since the pictures are taken at an angle, rather than directly overhead, they are also inlcuding the side and front of my house as impervious area, and counting some area where the roof above is also counted. This is analogous to including the area of walls and the ceiling when calculating the floorspace of a room. Further, the property lines are misregistered, so there are impervious surfaces included that are not even on my property.
All told, the impervious surface on my property was overestimated by almost 50 percent. This is a huge error. I believe the city has a moral duty to provide better estimates of impervious area. I feel it is unrealistic to put the burden of correcting these problems on the homeowners, or to even expect that all residents would be able to look at the picture provided online and be able to find the errors.
Finally, since the city is using these figures to charge residents, I believe the city also has a legal duty to not overcharge its residents. I suspect that all the photos used for calculating impervious area will all be taken at an angle, so that every lot in the city will have a significant overestimate of its impervious area. There are likely several thousand properties where the overestimates are pushing a property into the next higher payment tier, and none with underestimates. This strikes me as a case ripe for a class-action lawsuit against the city, which will cost all of us money. The longer the current estimates are used, the greater the damage will be when this occurs.
If the city is to charge its residents based on impervious area, it will need to find an accurate way of measuring that area. The method being used now is simply too inaccurate to use.
Michael A. Blischke
(734) 480-5046
Stormwater_comparison.JPG
207K View Download
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"Kunselman, Stephen"
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Oct 11
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Tom,
If an overestimate is found to be valid and a determination is made to drop the assigned Tier to a lower level Tier, will a refund be issued by the City for the overestimation regardless of when the overestimation is corrected?
Also, can you explain what relevance a “roof overhang” has to do with imperviousness – the ground is still pervious underneath and is obviously available for infiltration of stormwater. If a house doesn’t have gutters, the stormwater hits the ground coming of the roof overhang and infiltrates on both sides of the roof overhang “plane.” Seems to me that is a little overzealous in calculating the impervious surface around the house and is quite subjective.
I’ve been overestimated too, so you’ll be hearing from me soon. Especially since my dog house and other yard art is included in my stormwater area calculation!!
Thanks, Steve
From: McMurtrie, Thomas
Sent: Thursday, October 11, 2007 7:42 AM
To: Hieftje, John; Lowenstein, Joan; Rapundalo, Stephen; Greden, Leigh; Kunselman, Stephen; Higgins, Marcia; Woods, Wendy A; Teall, Margie; Easthope, Christopher; Johnson, Robert; Suarez, Ron
Cc: Hupy, Craig; McCormick, Sue; Gih, Brandi
- Show quoted text -
Subject: RE: overestimates of impervious surfaces for stormwater rates
- Show quoted text -
Mayor and Council:
This is an interesting case. If you look at the aerial impervious area interpretations (attached), I would come to the conclusion that our system has worked fairly well. There are a few small areas in shadows that we missed, as well as a small grassy area out front. These might total a few hundred square feet, and would not change his rate. He is currently at 3908 square feet, and would have to drop to 2187 square feet to move to another tier.
I'm not sure where Mr. Blischke came up with the claim that we overstated his impervious area by 50%. Looking at the assessor's website, his building foot print is 2161 square feet -- but this does not include his driveway, sidewalk, patios, roof overhangs, or any other impervious area. We have never received any communications from Mr. Blishke asking for an adjustment to his impervious area or his rate.
Residents have made extensive use of our online imagery. We have received hundreds of requests for adjustments. Any adjustment that is made will be saved as a GIS image layer, so that in future flights, we will be able to identify those adjustments and apply them.
Please do not hesitate to contact me if you have any questions or comments.
Thanks!
Tom McMurtrie
Ann Arbor Systems Planning Unit-Public Services
P.O. Box 8647 / 100 N. Fifth Ave.
Ann Arbor, MI 48107
734.994.6581 Fax: 734.996.3064
www.a2gov.org
From: Hieftje, John
Sent: Wednesday, October 10, 2007 2:08 PM
To: 'Blischke, Michael A.'; Lowenstein, Joan; Rapundalo, Stephen; Greden, Leigh; Kunselman, Stephen; Higgins, Marcia; Woods, Wendy A; Teall, Margie; Easthope, Christopher; Johnson, Robert; Suarez, Ron
Subject: RE: overestimates of impervious surfaces for stormwater rates
Hello:
I appreciate your concerns with the data that has been collected and I will pass this letter on to city staff who are working on this program for their information and comment.
Thank you for writing.
John Hieftje
-----Original Message-----
From: Blischke, Michael A. [mailto:michael.blischke@gd-ais.com]
Sent: Wednesday, October 10, 2007 1:23 PM
To: Hieftje, John; Lowenstein, Joan; Rapundalo, Stephen; Greden, Leigh; Kunselman, Stephen; Higgins, Marcia; Woods, Wendy A; Teall, Margie; Easthope, Christopher; Johnson, Robert; Suarez, Ron
Subject: overestimates of impervious surfaces for stormwater rates
Councilmembers and Mayor
I am writing regarding the method used in estimating the amount of impervious surface on properties of Ann Arbor residents. These estimates are used to calculate the stormwater rates residents are paying. The method of using aerial photographs is resulting in significantly overestimating the amount of impervious surface on residents’s lots. The Stormwater rate page lists a few areas that may result in overestimates: Wood chips, shadows, and decks. In my case (see the attached image), I found that bare soil and vegetation, even when not in shadow, were counted as impervious surface. More troubling, since the pictures are taken at an angle, rather than directly overhead, they are also inlcuding the side and front of my house as impervious area, and counting some area where the roof above is also counted. This is analogous to including the area of walls and the ceiling when calculating the floorspace of a room. Further, the property lines are misregistered, so there are impervious surfaces included that are not even on my property.
All told, the impervious surface on my property was overestimated by almost 50 percent. This is a huge error. I believe the city has a moral duty to provide better estimates of impervious area. I feel it is unrealistic to put the burden of correcting these problems on the homeowners, or to even expect that all residents would be able to look at the picture provided online and be able to find the errors.
Finally, since the city is using these figures to charge residents, I believe the city also has a legal duty to not overcharge its residents. I suspect that all the photos used for calculating impervious area will all be taken at an angle, so that every lot in the city will have a significant overestimate of its impervious area. There are likely several thousand properties where the overestimates are pushing a property into the next higher payment tier, and none with underestimates. This strikes me as a case ripe for a class-action lawsuit against the city, which will cost all of us money. The longer the current estimates are used, the greater the damage will be when this occurs.
If the city is to charge its residents based on impervious area, it will need to find an accurate way of measuring that area. The method being used now is simply too inaccurate to use.
Michael A. Blischke
(734) 480-5046
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Michael,
Thank you for the clarification.
Yes, our consultant did a pilot analysis of this process, analyzing automated analysis systems from 2 vendors compared with a manual analysis. The result of this pilot recognized that there would be some manual corrections required. Generally, we found that the corrections would be smaller in scope than those required on your property.
That is why we made the system as user friendly as possible. If you have access to the internet, it's a very simple process to mark up your image and send it in for an adjustment. If you don't have access to the internet, a simple phone call will get that document in the mail to you.
Once a property owner has submitted that adjustment, we are recording it as a GIS layer on our mapping. That means that in future aerial flights, we will encorporate that adjustment into the impervious area analysis. It is our intent to conduct these flights every two to three years, to capture impervious area changes from new construction and additions.
One other point I would like to make is that the tier system we are using minimizes the impact of small oscillations in the impervious area analyses. The adjustment has to be large enough to get over a tier break. We will be happy to make the adjustments in your impervious area analysis. However (as you point out), there will not be a change in the rate.
Thanks again.
Tom
From: Blischke, Michael A. [mailto:michael.blischke@gd-ais.com]
Sent: Thursday, October 11, 2007 11:51 AM
To: McMurtrie, Thomas
- Show quoted text -
Cc: Hieftje, John; Lowenstein, Joan; Rapundalo, Stephen; Greden, Leigh; Kunselman, Stephen; Higgins, Marcia; Woods, Wendy A; Teall, Margie; Easthope, Christopher; Johnson, Robert; Suarez, Ron; Hupy, Craig; McCormick, Sue; Gih, Brandi
Subject: RE: overestimates of impervious surfaces for stormwater rates
- Show quoted text -
Tom
I measured the area of my house, and my sidewalk and driveway, and came up with a little over 2600 square feet. 50 percent over 2600 is 3900. Perhaps you weren’t forwarded the JPEG image I sent to the mayor and Council, so I’m including it again. It shows all the errors mentioned in my original email, labeled and color-coded.
I did not write to Council because I expected my rates to be affected. I wrote because I believe the errors in your method of estimating impervious surface will result in systematically overestimating the error, resulting in thousands of homes across the city being charged a greater rate than is appropriate. In my case, it won’t matter, because my true impervious surface area is at the low end of the tier I am in, and your errors merely bump me into the high end of the tier.
Other residents, however, may be at the high end of their tier, and the errors of the sort on my property will bump them into the next tier. Since the city is charging us based on the area, I believe the city has a duty to prevent overestimates from happening. Instead, it seems the city has a system that will systematically overestimate residents’s impervious areas, then places the burden on all of us to find those errors and complain. And who’s to say that every resident will even be capable of realizing that, for example, including the side and front of a house is an error. Even you didn’t seem to notice that.
As long as I’m writing, what level of accuracy are you expecting from your system? Have you taken a random sample of homes, and compared the estimated areas to the true areas?
Michael
From: McMurtrie, Thomas [mailto:TMcMurtrie@a2gov.org]
Sent: Thursday, October 11, 2007 9:12 AM
To: Blischke, Michael A.
Cc: Hieftje, John; Lowenstein, Joan; Rapundalo, Stephen; Greden, Leigh; Kunselman, Stephen; Higgins, Marcia; Woods, Wendy A; Teall, Margie; Easthope, Christopher; Johnson, Robert; Suarez, Ron; Hupy, Craig; McCormick, Sue; Gih, Brandi
Subject: RE: overestimates of impervious surfaces for stormwater rates
Mr. Blischke,
Thank you for your feedback on our stormwater rates system. I am sorry to hear about your displeasure with it.
In looking at the image for your property, I would appreciate it if you could help me understand how you came up with the 50% error figure that you stated in your letter. I see some discrepencies in the shaded areas, a small grassy area in the front of your house, and the sidewalk at the front of your property (which is part of the right of way) These alone are not close to the 50% error figure, and would not be enough to change your rate. You are currently at 3908 square feet, and would need to drop to 2187 square feet to move to another tier.
Looking at the assessor's website, it shows that your building footprint is 2161 square feet. Any other impervious areas on your property would also need to be added. This would include but not be limited to: your driveway, sidewalks on your property, patios, and roof overhangs.
If you print your attached impervious area image, and highlight areas that we have incorrectly identified, we would be happy to make adjustments. If you have questions, or would like us to conduct a site visit to help with the analysis, please call me directly at 994-6581 and we would be more than willing to arrange that.
Thanks again,
Tom McMurtrie
Ann Arbor Systems Planning Unit-Public Services
P.O. Box 8647 / 100 N. Fifth Ave.
Ann Arbor, MI 48107
734.994.6581 Fax: 734.996.3064
www.a2gov.org
-----Original Message-----
From: Blischke, Michael A. [mailto:michael.blischke@gd-ais.com]
Sent: Wednesday, October 10, 2007 1:23 PM
To: Hieftje, John; Lowenstein, Joan; Rapundalo, Stephen; Greden, Leigh; Kunselman, Stephen; Higgins, Marcia; Woods, Wendy A; Teall, Margie; Easthope, Christopher; Johnson, Robert; Suarez, Ron
Subject: overestimates of impervious surfaces for stormwater rates
Councilmembers and Mayor
I am writing regarding the method used in estimating the amount of impervious surface on properties of Ann Arbor residents. These estimates are used to calculate the stormwater rates residents are paying. The method of using aerial photographs is resulting in significantly overestimating the amount of impervious surface on residents’s lots. The Stormwater rate page lists a few areas that may result in overestimates: Wood chips, shadows, and decks. In my case (see the attached image), I found that bare soil and vegetation, even when not in shadow, were counted as impervious surface. More troubling, since the pictures are taken at an angle, rather than directly overhead, they are also inlcuding the side and front of my house as impervious area, and counting some area where the roof above is also counted. This is analogous to including the area of walls and the ceiling when calculating the floorspace of a room. Further, the property lines are misregistered, so there are impervious surfaces included that are not even on my property.
All told, the impervious surface on my property was overestimated by almost 50 percent. This is a huge error. I believe the city has a moral duty to provide better estimates of impervious area. I feel it is unrealistic to put the burden of correcting these problems on the homeowners, or to even expect that all residents would be able to look at the picture provided online and be able to find the errors.
Finally, since the city is using these figures to charge residents, I believe the city also has a legal duty to not overcharge its residents. I suspect that all the photos used for calculating impervious area will all be taken at an angle, so that every lot in the city will have a significant overestimate of its impervious area. There are likely several thousand properties where the overestimates are pushing a property into the next higher payment tier, and none with underestimates. This strikes me as a case ripe for a class-action lawsuit against the city, which will cost all of us money. The longer the current estimates are used, the greater the damage will be when this occurs.
If the city is to charge its residents based on impervious area, it will need to find an accurate way of measuring that area. The method being used now is simply too inaccurate to use.
Michael A. Blischke
(734) 480-5046
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Steve,
When a property owner requests an adjustment, we will apply that adjustment effective immediately. We don't typically issue credits for previous stormwater invoices. With some adjustments (such as the removal of a driveway or structure), there is usually no way to prove when that adjustment occured.
The reason that a roof overhang counts as impervious is that most roofs have gutters and concentrate water that creates a greater runoff. In addition, there is no practical way from aerial photographs to determine what is an overhang vs. what is the footprint.
We will be happy to make an adjustment to your impervious area analysis. We look forward to receiving your feedback.
Thanks!
Tom
From: Kunselman, Stephen
Sent: Thursday, October 11, 2007 12:55 PM
To: McMurtrie, Thomas
Cc: Hupy, Craig; McCormick, Sue; Gih, Brandi; Hieftje, John; Lowenstein, Joan; Rapundalo, Stephen; Greden, Leigh; Higgins, Marcia; Woods, Wendy A; Teall, Margie; Easthope, Christopher; Johnson, Robert; Suarez, Ron
- Show quoted text -
Subject: RE: overestimates of impervious surfaces for stormwater rates
- Show quoted text -
Tom,
If an overestimate is found to be valid and a determination is made to drop the assigned Tier to a lower level Tier, will a refund be issued by the City for the overestimation regardless of when the overestimation is corrected?
Also, can you explain what relevance a “roof overhang” has to do with imperviousness – the ground is still pervious underneath and is obviously available for infiltration of stormwater. If a house doesn’t have gutters, the stormwater hits the ground coming of the roof overhang and infiltrates on both sides of the roof overhang “plane.” Seems to me that is a little overzealous in calculating the impervious surface around the house and is quite subjective.
I’ve been overestimated too, so you’ll be hearing from me soon. Especially since my dog house and other yard art is included in my stormwater area calculation!!
Thanks, Steve
From: McMurtrie, Thomas
Sent: Thursday, October 11, 2007 7:42 AM
To: Hieftje, John; Lowenstein, Joan; Rapundalo, Stephen; Greden, Leigh; Kunselman, Stephen; Higgins, Marcia; Woods, Wendy A; Teall, Margie; Easthope, Christopher; Johnson, Robert; Suarez, Ron
Cc: Hupy, Craig; McCormick, Sue; Gih, Brandi
Subject: RE: overestimates of impervious surfaces for stormwater rates
Mayor and Council:
This is an interesting case. If you look at the aerial impervious area interpretations (attached), I would come to the conclusion that our system has worked fairly well. There are a few small areas in shadows that we missed, as well as a small grassy area out front. These might total a few hundred square feet, and would not change his rate. He is currently at 3908 square feet, and would have to drop to 2187 square feet to move to another tier.
I'm not sure where Mr. Blischke came up with the claim that we overstated his impervious area by 50%. Looking at the assessor's website, his building foot print is 2161 square feet -- but this does not include his driveway, sidewalk, patios, roof overhangs, or any other impervious area. We have never received any communications from Mr. Blishke asking for an adjustment to his impervious area or his rate.
Residents have made extensive use of our online imagery. We have received hundreds of requests for adjustments. Any adjustment that is made will be saved as a GIS image layer, so that in future flights, we will be able to identify those adjustments and apply them.
Please do not hesitate to contact me if you have any questions or comments.
Thanks!
Tom McMurtrie
Ann Arbor Systems Planning Unit-Public Services
P.O. Box 8647 / 100 N. Fifth Ave.
Ann Arbor, MI 48107
734.994.6581 Fax: 734.996.3064
www.a2gov.org
From: Hieftje, John
Sent: Wednesday, October 10, 2007 2:08 PM
To: 'Blischke, Michael A.'; Lowenstein, Joan; Rapundalo, Stephen; Greden, Leigh; Kunselman, Stephen; Higgins, Marcia; Woods, Wendy A; Teall, Margie; Easthope, Christopher; Johnson, Robert; Suarez, Ron
Subject: RE: overestimates of impervious surfaces for stormwater rates
Hello:
I appreciate your concerns with the data that has been collected and I will pass this letter on to city staff who are working on this program for their information and comment.
Thank you for writing.
John Hieftje
-----Original Message-----
From: Blischke, Michael A. [mailto:michael.blischke@gd-ais.com]
Sent: Wednesday, October 10, 2007 1:23 PM
To: Hieftje, John; Lowenstein, Joan; Rapundalo, Stephen; Greden, Leigh; Kunselman, Stephen; Higgins, Marcia; Woods, Wendy A; Teall, Margie; Easthope, Christopher; Johnson, Robert; Suarez, Ron
Subject: overestimates of impervious surfaces for stormwater rates
Councilmembers and Mayor
I am writing regarding the method used in estimating the amount of impervious surface on properties of Ann Arbor residents. These estimates are used to calculate the stormwater rates residents are paying. The method of using aerial photographs is resulting in significantly overestimating the amount of impervious surface on residents’s lots. The Stormwater rate page lists a few areas that may result in overestimates: Wood chips, shadows, and decks. In my case (see the attached image), I found that bare soil and vegetation, even when not in shadow, were counted as impervious surface. More troubling, since the pictures are taken at an angle, rather than directly overhead, they are also inlcuding the side and front of my house as impervious area, and counting some area where the roof above is also counted. This is analogous to including the area of walls and the ceiling when calculating the floorspace of a room. Further, the property lines are misregistered, so there are impervious surfaces included that are not even on my property.
All told, the impervious surface on my property was overestimated by almost 50 percent. This is a huge error. I believe the city has a moral duty to provide better estimates of impervious area. I feel it is unrealistic to put the burden of correcting these problems on the homeowners, or to even expect that all residents would be able to look at the picture provided online and be able to find the errors.
Finally, since the city is using these figures to charge residents, I believe the city also has a legal duty to not overcharge its residents. I suspect that all the photos used for calculating impervious area will all be taken at an angle, so that every lot in the city will have a significant overestimate of its impervious area. There are likely several thousand properties where the overestimates are pushing a property into the next higher payment tier, and none with underestimates. This strikes me as a case ripe for a class-action lawsuit against the city, which will cost all of us money. The longer the current estimates are used, the greater the damage will be when this occurs.
If the city is to charge its residents based on impervious area, it will need to find an accurate way of measuring that area. The method being used now is simply too inaccurate to use.
Michael A. Blischke
(734) 480-5046
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Tom,
Thank you for responding (and I apologize if my comments are a bit terse). I beg to differ that the City gets to arbitrarily collect overestimated storm water charges until the overestimation is discovered and then keep all the prior overestimated charges. That is a significant burden to the working families of this community who hadn’t the resources to address their stormwater rate before they got their first water bill. I just saw my stormwater rate go from $0.42/day to $0.74/day and because I didn’t get it corrected (my assessment record has my house footprint at 1116 sqft and my gravel drive way is about 900 sqft – and no sidewalks, which puts me in Tier 1, not Tier 2 as I am charged) before this first water bill came out I’m penalized? Doesn’t seem fair, nor does it seem right - I’ll be debating this policy further.
Also, just because a gutter concentrates the flow of water on a property, does not imply that it is impacting the city stormwater system with any greater volume. There are way too many variables in stormwater management to be using simplistic statements such as “gutters concentrate water contributing to greater water runoff” – regardless of the concentration of storm flow coming off the house, it’s the volume of water reaching the city system that is the issue, hence why would you give credits for rain barrels and rain gardens, but not gutter-less houses?
Thanks,
Steve
From: McMurtrie, Thomas
Sent: Friday, October 12, 2007 10:26 AM
To: Kunselman, Stephen
- Show quoted text -
Cc: Hupy, Craig; McCormick, Sue; Gih, Brandi; Hieftje, John; Lowenstein, Joan; Rapundalo, Stephen; Greden, Leigh; Higgins, Marcia; Woods, Wendy A; Teall, Margie; Easthope, Christopher; Johnson, Robert; Suarez, Ron
Subject: RE: overestimates of impervious surfaces for stormwater rates
- Show quoted text -
Steve,
When a property owner requests an adjustment, we will apply that adjustment effective immediately. We don't typically issue credits for previous stormwater invoices. With some adjustments (such as the removal of a driveway or structure), there is usually no way to prove when that adjustment occured.
The reason that a roof overhang counts as impervious is that most roofs have gutters and concentrate water that creates a greater runoff. In addition, there is no practical way from aerial photographs to determine what is an overhang vs. what is the footprint.
We will be happy to make an adjustment to your impervious area analysis. We look forward to receiving your feedback.
Thanks!
Tom
From: Kunselman, Stephen
Sent: Thursday, October 11, 2007 12:55 PM
To: McMurtrie, Thomas
Cc: Hupy, Craig; McCormick, Sue; Gih, Brandi; Hieftje, John; Lowenstein, Joan; Rapundalo, Stephen; Greden, Leigh; Higgins, Marcia; Woods, Wendy A; Teall, Margie; Easthope, Christopher; Johnson, Robert; Suarez, Ron
Subject: RE: overestimates of impervious surfaces for stormwater rates
Tom,
If an overestimate is found to be valid and a determination is made to drop the assigned Tier to a lower level Tier, will a refund be issued by the City for the overestimation regardless of when the overestimation is corrected?
Also, can you explain what relevance a “roof overhang” has to do with imperviousness – the ground is still pervious underneath and is obviously available for infiltration of stormwater. If a house doesn’t have gutters, the stormwater hits the ground coming of the roof overhang and infiltrates on both sides of the roof overhang “plane.” Seems to me that is a little overzealous in calculating the impervious surface around the house and is quite subjective.
I’ve been overestimated too, so you’ll be hearing from me soon. Especially since my dog house and other yard art is included in my stormwater area calculation!!
Thanks, Steve
From: McMurtrie, Thomas
Sent: Thursday, October 11, 2007 7:42 AM
To: Hieftje, John; Lowenstein, Joan; Rapundalo, Stephen; Greden, Leigh; Kunselman, Stephen; Higgins, Marcia; Woods, Wendy A; Teall, Margie; Easthope, Christopher; Johnson, Robert; Suarez, Ron
Cc: Hupy, Craig; McCormick, Sue; Gih, Brandi
Subject: RE: overestimates of impervious surfaces for stormwater rates
Mayor and Council:
This is an interesting case. If you look at the aerial impervious area interpretations (attached), I would come to the conclusion that our system has worked fairly well. There are a few small areas in shadows that we missed, as well as a small grassy area out front. These might total a few hundred square feet, and would not change his rate. He is currently at 3908 square feet, and would have to drop to 2187 square feet to move to another tier.
I'm not sure where Mr. Blischke came up with the claim that we overstated his impervious area by 50%. Looking at the assessor's website, his building foot print is 2161 square feet -- but this does not include his driveway, sidewalk, patios, roof overhangs, or any other impervious area. We have never received any communications from Mr. Blishke asking for an adjustment to his impervious area or his rate.
Residents have made extensive use of our online imagery. We have received hundreds of requests for adjustments. Any adjustment that is made will be saved as a GIS image layer, so that in future flights, we will be able to identify those adjustments and apply them.
Please do not hesitate to contact me if you have any questions or comments.
Thanks!
Tom McMurtrie
Ann Arbor Systems Planning Unit-Public Services
P.O. Box 8647 / 100 N. Fifth Ave.
Ann Arbor, MI 48107
734.994.6581 Fax: 734.996.3064
www.a2gov.org
From: Hieftje, John
Sent: Wednesday, October 10, 2007 2:08 PM
To: 'Blischke, Michael A.'; Lowenstein, Joan; Rapundalo, Stephen; Greden, Leigh; Kunselman, Stephen; Higgins, Marcia; Woods, Wendy A; Teall, Margie; Easthope, Christopher; Johnson, Robert; Suarez, Ron
Subject: RE: overestimates of impervious surfaces for stormwater rates
Hello:
I appreciate your concerns with the data that has been collected and I will pass this letter on to city staff who are working on this program for their information and comment.
overestimates of impervious surfaces for stormwater rates
"Blischke, Michael A." <michael.blischke@gd-ais.com>
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Councilmembers and Mayor
I am writing regarding the method used in estimating the amount of impervious surface on properties of Ann Arbor residents. These estimates are used to calculate the stormwater rates residents are paying. The method of using aerial photographs is resulting in significantly overestimating the amount of impervious surface on residents’s lots. The Stormwater rate page lists a few areas that may result in overestimates: Wood chips, shadows, and decks. In my case (see the attached image), I found that bare soil and vegetation, even when not in shadow, were counted as impervious surface. More troubling, since the pictures are taken at an angle, rather than directly overhead, they are also inlcuding the side and front of my house as impervious area, and counting some area where the roof above is also counted. This is analogous to including the area of walls and the ceiling when calculating the floorspace of a room. Further, the property lines are misregistered, so there are impervious surfaces included that are not even on my property.
All told, the impervious surface on my property was overestimated by almost 50 percent. This is a huge error. I believe the city has a moral duty to provide better estimates of impervious area. I feel it is unrealistic to put the burden of correcting these problems on the homeowners, or to even expect that all residents would be able to look at the picture provided online and be able to find the errors.
Finally, since the city is using these figures to charge residents, I believe the city also has a legal duty to not overcharge its residents. I suspect that all the photos used for calculating impervious area will all be taken at an angle, so that every lot in the city will have a significant overestimate of its impervious area. There are likely several thousand properties where the overestimates are pushing a property into the next higher payment tier, and none with underestimates. This strikes me as a case ripe for a class-action lawsuit against the city, which will cost all of us money. The longer the current estimates are used, the greater the damage will be when this occurs.
If the city is to charge its residents based on impervious area, it will need to find an accurate way of measuring that area. The method being used now is simply too inaccurate to use.
Michael A. Blischke
(734) 480-5046
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Hello:
I appreciate your concerns with the data that has been collected and I will pass this letter on to city staff who are working on this program for their information and comment.
Thank you for writing.
John Hieftje
- Show quoted text -
-----Original Message-----
From: Blischke, Michael A. [mailto:michael.blischke@gd-ais.com]
Sent: Wednesday, October 10, 2007 1:23 PM
To: Hieftje, John; Lowenstein, Joan; Rapundalo, Stephen; Greden, Leigh; Kunselman, Stephen; Higgins, Marcia; Woods, Wendy A; Teall, Margie; Easthope, Christopher; Johnson, Robert; Suarez, Ron
Subject: overestimates of impervious surfaces for stormwater rates
Councilmembers and Mayor
I am writing regarding the method used in estimating the amount of impervious surface on properties of Ann Arbor residents. These estimates are used to calculate the stormwater rates residents are paying. The method of using aerial photographs is resulting in significantly overestimating the amount of impervious surface on residents’s lots. The Stormwater rate page lists a few areas that may result in overestimates: Wood chips, shadows, and decks. In my case (see the attached image), I found that bare soil and vegetation, even when not in shadow, were counted as impervious surface. More troubling, since the pictures are taken at an angle, rather than directly overhead, they are also inlcuding the side and front of my house as impervious area, and counting some area where the roof above is also counted. This is analogous to including the area of walls and the ceiling when calculating the floorspace of a room. Further, the property lines are misregistered, so there are impervious surfaces included that are not even on my property.
All told, the impervious surface on my property was overestimated by almost 50 percent. This is a huge error. I believe the city has a moral duty to provide better estimates of impervious area. I feel it is unrealistic to put the burden of correcting these problems on the homeowners, or to even expect that all residents would be able to look at the picture provided online and be able to find the errors.
Finally, since the city is using these figures to charge residents, I believe the city also has a legal duty to not overcharge its residents. I suspect that all the photos used for calculating impervious area will all be taken at an angle, so that every lot in the city will have a significant overestimate of its impervious area. There are likely several thousand properties where the overestimates are pushing a property into the next higher payment tier, and none with underestimates. This strikes me as a case ripe for a class-action lawsuit against the city, which will cost all of us money. The longer the current estimates are used, the greater the damage will be when this occurs.
If the city is to charge its residents based on impervious area, it will need to find an accurate way of measuring that area. The method being used now is simply too inaccurate to use.
Michael A. Blischke
(734) 480-5046
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Mayor and Council:
This is an interesting case. If you look at the aerial impervious area interpretations (attached), I would come to the conclusion that our system has worked fairly well. There are a few small areas in shadows that we missed, as well as a small grassy area out front. These might total a few hundred square feet, and would not change his rate. He is currently at 3908 square feet, and would have to drop to 2187 square feet to move to another tier.
I'm not sure where Mr. Blischke came up with the claim that we overstated his impervious area by 50%. Looking at the assessor's website, his building foot print is 2161 square feet -- but this does not include his driveway, sidewalk, patios, roof overhangs, or any other impervious area. We have never received any communications from Mr. Blishke asking for an adjustment to his impervious area or his rate.
Residents have made extensive use of our online imagery. We have received hundreds of requests for adjustments. Any adjustment that is made will be saved as a GIS image layer, so that in future flights, we will be able to identify those adjustments and apply them.
Please do not hesitate to contact me if you have any questions or comments.
Thanks!
Tom McMurtrie
Ann Arbor Systems Planning Unit-Public Services
P.O. Box 8647 / 100 N. Fifth Ave.
Ann Arbor, MI 48107
734.994.6581 Fax: 734.996.3064
www.a2gov.org
From: Hieftje, John
Sent: Wednesday, October 10, 2007 2:08 PM
To: 'Blischke, Michael A.'; Lowenstein, Joan; Rapundalo, Stephen; Greden, Leigh; Kunselman, Stephen; Higgins, Marcia; Woods, Wendy A; Teall, Margie; Easthope, Christopher; Johnson, Robert; Suarez, Ron
Subject: RE: overestimates of impervious surfaces for stormwater rates
- Show quoted text -
Hello:
I appreciate your concerns with the data that has been collected and I will pass this letter on to city staff who are working on this program for their information and comment.
Thank you for writing.
John Hieftje
-----Original Message-----
From: Blischke, Michael A. [mailto:michael.blischke@gd-ais.com]
Sent: Wednesday, October 10, 2007 1:23 PM
To: Hieftje, John; Lowenstein, Joan; Rapundalo, Stephen; Greden, Leigh; Kunselman, Stephen; Higgins, Marcia; Woods, Wendy A; Teall, Margie; Easthope, Christopher; Johnson, Robert; Suarez, Ron
Subject: overestimates of impervious surfaces for stormwater rates
Councilmembers and Mayor
I am writing regarding the method used in estimating the amount of impervious surface on properties of Ann Arbor residents. These estimates are used to calculate the stormwater rates residents are paying. The method of using aerial photographs is resulting in significantly overestimating the amount of impervious surface on residents’s lots. The Stormwater rate page lists a few areas that may result in overestimates: Wood chips, shadows, and decks. In my case (see the attached image), I found that bare soil and vegetation, even when not in shadow, were counted as impervious surface. More troubling, since the pictures are taken at an angle, rather than directly overhead, they are also inlcuding the side and front of my house as impervious area, and counting some area where the roof above is also counted. This is analogous to including the area of walls and the ceiling when calculating the floorspace of a room. Further, the property lines are misregistered, so there are impervious surfaces included that are not even on my property.
All told, the impervious surface on my property was overestimated by almost 50 percent. This is a huge error. I believe the city has a moral duty to provide better estimates of impervious area. I feel it is unrealistic to put the burden of correcting these problems on the homeowners, or to even expect that all residents would be able to look at the picture provided online and be able to find the errors.
Finally, since the city is using these figures to charge residents, I believe the city also has a legal duty to not overcharge its residents. I suspect that all the photos used for calculating impervious area will all be taken at an angle, so that every lot in the city will have a significant overestimate of its impervious area. There are likely several thousand properties where the overestimates are pushing a property into the next higher payment tier, and none with underestimates. This strikes me as a case ripe for a class-action lawsuit against the city, which will cost all of us money. The longer the current estimates are used, the greater the damage will be when this occurs.
If the city is to charge its residents based on impervious area, it will need to find an accurate way of measuring that area. The method being used now is simply too inaccurate to use.
Michael A. Blischke
(734) 480-5046
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Thanks Tom:
Are you going to reply to this resident or should I forward this to him?
John
From: McMurtrie, Thomas
Sent: Thursday, October 11, 2007 7:42 AM
To: Hieftje, John; Lowenstein, Joan; Rapundalo, Stephen; Greden, Leigh; Kunselman, Stephen; Higgins, Marcia; Woods, Wendy A; Teall, Margie; Easthope, Christopher; Johnson, Robert; Suarez, Ron
Cc: Hupy, Craig; McCormick, Sue; Gih, Brandi
- Show quoted text -
Subject: RE: overestimates of impervious surfaces for stormwater rates
- Show quoted text -
Mayor and Council:
This is an interesting case. If you look at the aerial impervious area interpretations (attached), I would come to the conclusion that our system has worked fairly well. There are a few small areas in shadows that we missed, as well as a small grassy area out front. These might total a few hundred square feet, and would not change his rate. He is currently at 3908 square feet, and would have to drop to 2187 square feet to move to another tier.
I'm not sure where Mr. Blischke came up with the claim that we overstated his impervious area by 50%. Looking at the assessor's website, his building foot print is 2161 square feet -- but this does not include his driveway, sidewalk, patios, roof overhangs, or any other impervious area. We have never received any communications from Mr. Blishke asking for an adjustment to his impervious area or his rate.
Residents have made extensive use of our online imagery. We have received hundreds of requests for adjustments. Any adjustment that is made will be saved as a GIS image layer, so that in future flights, we will be able to identify those adjustments and apply them.
Please do not hesitate to contact me if you have any questions or comments.
Thanks!
Tom McMurtrie
Ann Arbor Systems Planning Unit-Public Services
P.O. Box 8647 / 100 N. Fifth Ave.
Ann Arbor, MI 48107
734.994.6581 Fax: 734.996.3064
www.a2gov.org
From: Hieftje, John
Sent: Wednesday, October 10, 2007 2:08 PM
To: 'Blischke, Michael A.'; Lowenstein, Joan; Rapundalo, Stephen; Greden, Leigh; Kunselman, Stephen; Higgins, Marcia; Woods, Wendy A; Teall, Margie; Easthope, Christopher; Johnson, Robert; Suarez, Ron
Subject: RE: overestimates of impervious surfaces for stormwater rates
Hello:
I appreciate your concerns with the data that has been collected and I will pass this letter on to city staff who are working on this program for their information and comment.
Thank you for writing.
John Hieftje
-----Original Message-----
From: Blischke, Michael A. [mailto:michael.blischke@gd-ais.com]
Sent: Wednesday, October 10, 2007 1:23 PM
To: Hieftje, John; Lowenstein, Joan; Rapundalo, Stephen; Greden, Leigh; Kunselman, Stephen; Higgins, Marcia; Woods, Wendy A; Teall, Margie; Easthope, Christopher; Johnson, Robert; Suarez, Ron
Subject: overestimates of impervious surfaces for stormwater rates
Councilmembers and Mayor
I am writing regarding the method used in estimating the amount of impervious surface on properties of Ann Arbor residents. These estimates are used to calculate the stormwater rates residents are paying. The method of using aerial photographs is resulting in significantly overestimating the amount of impervious surface on residents’s lots. The Stormwater rate page lists a few areas that may result in overestimates: Wood chips, shadows, and decks. In my case (see the attached image), I found that bare soil and vegetation, even when not in shadow, were counted as impervious surface. More troubling, since the pictures are taken at an angle, rather than directly overhead, they are also inlcuding the side and front of my house as impervious area, and counting some area where the roof above is also counted. This is analogous to including the area of walls and the ceiling when calculating the floorspace of a room. Further, the property lines are misregistered, so there are impervious surfaces included that are not even on my property.
All told, the impervious surface on my property was overestimated by almost 50 percent. This is a huge error. I believe the city has a moral duty to provide better estimates of impervious area. I feel it is unrealistic to put the burden of correcting these problems on the homeowners, or to even expect that all residents would be able to look at the picture provided online and be able to find the errors.
Finally, since the city is using these figures to charge residents, I believe the city also has a legal duty to not overcharge its residents. I suspect that all the photos used for calculating impervious area will all be taken at an angle, so that every lot in the city will have a significant overestimate of its impervious area. There are likely several thousand properties where the overestimates are pushing a property into the next higher payment tier, and none with underestimates. This strikes me as a case ripe for a class-action lawsuit against the city, which will cost all of us money. The longer the current estimates are used, the greater the damage will be when this occurs.
If the city is to charge its residents based on impervious area, it will need to find an accurate way of measuring that area. The method being used now is simply too inaccurate to use.
Michael A. Blischke
(734) 480-5046
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Mr. Blischke,
Thank you for your feedback on our stormwater rates system. I am sorry to hear about your displeasure with it.
In looking at the image for your property, I would appreciate it if you could help me understand how you came up with the 50% error figure that you stated in your letter. I see some discrepencies in the shaded areas, a small grassy area in the front of your house, and the sidewalk at the front of your property (which is part of the right of way) These alone are not close to the 50% error figure, and would not be enough to change your rate. You are currently at 3908 square feet, and would need to drop to 2187 square feet to move to another tier.
Looking at the assessor's website, it shows that your building footprint is 2161 square feet. Any other impervious areas on your property would also need to be added. This would include but not be limited to: your driveway, sidewalks on your property, patios, and roof overhangs.
If you print your attached impervious area image, and highlight areas that we have incorrectly identified, we would be happy to make adjustments. If you have questions, or would like us to conduct a site visit to help with the analysis, please call me directly at 994-6581 and we would be more than willing to arrange that.
Thanks again,
Tom McMurtrie
Ann Arbor Systems Planning Unit-Public Services
P.O. Box 8647 / 100 N. Fifth Ave.
Ann Arbor, MI 48107
734.994.6581 Fax: 734.996.3064
www.a2gov.org
- Show quoted text -
-----Original Message-----
From: Blischke, Michael A. [mailto:michael.blischke@gd-ais.com]
Sent: Wednesday, October 10, 2007 1:23 PM
To: Hieftje, John; Lowenstein, Joan; Rapundalo, Stephen; Greden, Leigh; Kunselman, Stephen; Higgins, Marcia; Woods, Wendy A; Teall, Margie; Easthope, Christopher; Johnson, Robert; Suarez, Ron
Subject: overestimates of impervious surfaces for stormwater rates
Councilmembers and Mayor
I am writing regarding the method used in estimating the amount of impervious surface on properties of Ann Arbor residents. These estimates are used to calculate the stormwater rates residents are paying. The method of using aerial photographs is resulting in significantly overestimating the amount of impervious surface on residents’s lots. The Stormwater rate page lists a few areas that may result in overestimates: Wood chips, shadows, and decks. In my case (see the attached image), I found that bare soil and vegetation, even when not in shadow, were counted as impervious surface. More troubling, since the pictures are taken at an angle, rather than directly overhead, they are also inlcuding the side and front of my house as impervious area, and counting some area where the roof above is also counted. This is analogous to including the area of walls and the ceiling when calculating the floorspace of a room. Further, the property lines are misregistered, so there are impervious surfaces included that are not even on my property.
All told, the impervious surface on my property was overestimated by almost 50 percent. This is a huge error. I believe the city has a moral duty to provide better estimates of impervious area. I feel it is unrealistic to put the burden of correcting these problems on the homeowners, or to even expect that all residents would be able to look at the picture provided online and be able to find the errors.
Finally, since the city is using these figures to charge residents, I believe the city also has a legal duty to not overcharge its residents. I suspect that all the photos used for calculating impervious area will all be taken at an angle, so that every lot in the city will have a significant overestimate of its impervious area. There are likely several thousand properties where the overestimates are pushing a property into the next higher payment tier, and none with underestimates. This strikes me as a case ripe for a class-action lawsuit against the city, which will cost all of us money. The longer the current estimates are used, the greater the damage will be when this occurs.
If the city is to charge its residents based on impervious area, it will need to find an accurate way of measuring that area. The method being used now is simply too inaccurate to use.
Michael A. Blischke
(734) 480-5046
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Tom
I measured the area of my house, and my sidewalk and driveway, and came up with a little over 2600 square feet. 50 percent over 2600 is 3900. Perhaps you weren’t forwarded the JPEG image I sent to the mayor and Council, so I’m including it again. It shows all the errors mentioned in my original email, labeled and color-coded.
I did not write to Council because I expected my rates to be affected. I wrote because I believe the errors in your method of estimating impervious surface will result in systematically overestimating the error, resulting in thousands of homes across the city being charged a greater rate than is appropriate. In my case, it won’t matter, because my true impervious surface area is at the low end of the tier I am in, and your errors merely bump me into the high end of the tier.
Other residents, however, may be at the high end of their tier, and the errors of the sort on my property will bump them into the next tier. Since the city is charging us based on the area, I believe the city has a duty to prevent overestimates from happening. Instead, it seems the city has a system that will systematically overestimate residents’s impervious areas, then places the burden on all of us to find those errors and complain. And who’s to say that every resident will even be capable of realizing that, for example, including the side and front of a house is an error. Even you didn’t seem to notice that.
As long as I’m writing, what level of accuracy are you expecting from your system? Have you taken a random sample of homes, and compared the estimated areas to the true areas?
Michael
From: McMurtrie, Thomas [mailto:TMcMurtrie@a2gov.org]
Sent: Thursday, October 11, 2007 9:12 AM
To: Blischke, Michael A.
Cc: Hieftje, John; Lowenstein, Joan; Rapundalo, Stephen; Greden, Leigh; Kunselman, Stephen; Higgins, Marcia; Woods, Wendy A; Teall, Margie; Easthope, Christopher; Johnson, Robert; Suarez, Ron; Hupy, Craig; McCormick, Sue; Gih, Brandi
Subject: RE: overestimates of impervious surfaces for stormwater rates
- Show quoted text -
Mr. Blischke,
Thank you for your feedback on our stormwater rates system. I am sorry to hear about your displeasure with it.
In looking at the image for your property, I would appreciate it if you could help me understand how you came up with the 50% error figure that you stated in your letter. I see some discrepencies in the shaded areas, a small grassy area in the front of your house, and the sidewalk at the front of your property (which is part of the right of way) These alone are not close to the 50% error figure, and would not be enough to change your rate. You are currently at 3908 square feet, and would need to drop to 2187 square feet to move to another tier.
Looking at the assessor's website, it shows that your building footprint is 2161 square feet. Any other impervious areas on your property would also need to be added. This would include but not be limited to: your driveway, sidewalks on your property, patios, and roof overhangs.
If you print your attached impervious area image, and highlight areas that we have incorrectly identified, we would be happy to make adjustments. If you have questions, or would like us to conduct a site visit to help with the analysis, please call me directly at 994-6581 and we would be more than willing to arrange that.
Thanks again,
Tom McMurtrie
Ann Arbor Systems Planning Unit-Public Services
P.O. Box 8647 / 100 N. Fifth Ave.
Ann Arbor, MI 48107
734.994.6581 Fax: 734.996.3064
www.a2gov.org
-----Original Message-----
From: Blischke, Michael A. [mailto:michael.blischke@gd-ais.com]
Sent: Wednesday, October 10, 2007 1:23 PM
To: Hieftje, John; Lowenstein, Joan; Rapundalo, Stephen; Greden, Leigh; Kunselman, Stephen; Higgins, Marcia; Woods, Wendy A; Teall, Margie; Easthope, Christopher; Johnson, Robert; Suarez, Ron
Subject: overestimates of impervious surfaces for stormwater rates
Councilmembers and Mayor
I am writing regarding the method used in estimating the amount of impervious surface on properties of Ann Arbor residents. These estimates are used to calculate the stormwater rates residents are paying. The method of using aerial photographs is resulting in significantly overestimating the amount of impervious surface on residents’s lots. The Stormwater rate page lists a few areas that may result in overestimates: Wood chips, shadows, and decks. In my case (see the attached image), I found that bare soil and vegetation, even when not in shadow, were counted as impervious surface. More troubling, since the pictures are taken at an angle, rather than directly overhead, they are also inlcuding the side and front of my house as impervious area, and counting some area where the roof above is also counted. This is analogous to including the area of walls and the ceiling when calculating the floorspace of a room. Further, the property lines are misregistered, so there are impervious surfaces included that are not even on my property.
All told, the impervious surface on my property was overestimated by almost 50 percent. This is a huge error. I believe the city has a moral duty to provide better estimates of impervious area. I feel it is unrealistic to put the burden of correcting these problems on the homeowners, or to even expect that all residents would be able to look at the picture provided online and be able to find the errors.
Finally, since the city is using these figures to charge residents, I believe the city also has a legal duty to not overcharge its residents. I suspect that all the photos used for calculating impervious area will all be taken at an angle, so that every lot in the city will have a significant overestimate of its impervious area. There are likely several thousand properties where the overestimates are pushing a property into the next higher payment tier, and none with underestimates. This strikes me as a case ripe for a class-action lawsuit against the city, which will cost all of us money. The longer the current estimates are used, the greater the damage will be when this occurs.
If the city is to charge its residents based on impervious area, it will need to find an accurate way of measuring that area. The method being used now is simply too inaccurate to use.
Michael A. Blischke
(734) 480-5046
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Tom,
If an overestimate is found to be valid and a determination is made to drop the assigned Tier to a lower level Tier, will a refund be issued by the City for the overestimation regardless of when the overestimation is corrected?
Also, can you explain what relevance a “roof overhang” has to do with imperviousness – the ground is still pervious underneath and is obviously available for infiltration of stormwater. If a house doesn’t have gutters, the stormwater hits the ground coming of the roof overhang and infiltrates on both sides of the roof overhang “plane.” Seems to me that is a little overzealous in calculating the impervious surface around the house and is quite subjective.
I’ve been overestimated too, so you’ll be hearing from me soon. Especially since my dog house and other yard art is included in my stormwater area calculation!!
Thanks, Steve
From: McMurtrie, Thomas
Sent: Thursday, October 11, 2007 7:42 AM
To: Hieftje, John; Lowenstein, Joan; Rapundalo, Stephen; Greden, Leigh; Kunselman, Stephen; Higgins, Marcia; Woods, Wendy A; Teall, Margie; Easthope, Christopher; Johnson, Robert; Suarez, Ron
Cc: Hupy, Craig; McCormick, Sue; Gih, Brandi
- Show quoted text -
Subject: RE: overestimates of impervious surfaces for stormwater rates
- Show quoted text -
Mayor and Council:
This is an interesting case. If you look at the aerial impervious area interpretations (attached), I would come to the conclusion that our system has worked fairly well. There are a few small areas in shadows that we missed, as well as a small grassy area out front. These might total a few hundred square feet, and would not change his rate. He is currently at 3908 square feet, and would have to drop to 2187 square feet to move to another tier.
I'm not sure where Mr. Blischke came up with the claim that we overstated his impervious area by 50%. Looking at the assessor's website, his building foot print is 2161 square feet -- but this does not include his driveway, sidewalk, patios, roof overhangs, or any other impervious area. We have never received any communications from Mr. Blishke asking for an adjustment to his impervious area or his rate.
Residents have made extensive use of our online imagery. We have received hundreds of requests for adjustments. Any adjustment that is made will be saved as a GIS image layer, so that in future flights, we will be able to identify those adjustments and apply them.
Please do not hesitate to contact me if you have any questions or comments.
Thanks!
Tom McMurtrie
Ann Arbor Systems Planning Unit-Public Services
P.O. Box 8647 / 100 N. Fifth Ave.
Ann Arbor, MI 48107
734.994.6581 Fax: 734.996.3064
www.a2gov.org
From: Hieftje, John
Sent: Wednesday, October 10, 2007 2:08 PM
To: 'Blischke, Michael A.'; Lowenstein, Joan; Rapundalo, Stephen; Greden, Leigh; Kunselman, Stephen; Higgins, Marcia; Woods, Wendy A; Teall, Margie; Easthope, Christopher; Johnson, Robert; Suarez, Ron
Subject: RE: overestimates of impervious surfaces for stormwater rates
Hello:
I appreciate your concerns with the data that has been collected and I will pass this letter on to city staff who are working on this program for their information and comment.
Thank you for writing.
John Hieftje
-----Original Message-----
From: Blischke, Michael A. [mailto:michael.blischke@gd-ais.com]
Sent: Wednesday, October 10, 2007 1:23 PM
To: Hieftje, John; Lowenstein, Joan; Rapundalo, Stephen; Greden, Leigh; Kunselman, Stephen; Higgins, Marcia; Woods, Wendy A; Teall, Margie; Easthope, Christopher; Johnson, Robert; Suarez, Ron
Subject: overestimates of impervious surfaces for stormwater rates
Councilmembers and Mayor
I am writing regarding the method used in estimating the amount of impervious surface on properties of Ann Arbor residents. These estimates are used to calculate the stormwater rates residents are paying. The method of using aerial photographs is resulting in significantly overestimating the amount of impervious surface on residents’s lots. The Stormwater rate page lists a few areas that may result in overestimates: Wood chips, shadows, and decks. In my case (see the attached image), I found that bare soil and vegetation, even when not in shadow, were counted as impervious surface. More troubling, since the pictures are taken at an angle, rather than directly overhead, they are also inlcuding the side and front of my house as impervious area, and counting some area where the roof above is also counted. This is analogous to including the area of walls and the ceiling when calculating the floorspace of a room. Further, the property lines are misregistered, so there are impervious surfaces included that are not even on my property.
All told, the impervious surface on my property was overestimated by almost 50 percent. This is a huge error. I believe the city has a moral duty to provide better estimates of impervious area. I feel it is unrealistic to put the burden of correcting these problems on the homeowners, or to even expect that all residents would be able to look at the picture provided online and be able to find the errors.
Finally, since the city is using these figures to charge residents, I believe the city also has a legal duty to not overcharge its residents. I suspect that all the photos used for calculating impervious area will all be taken at an angle, so that every lot in the city will have a significant overestimate of its impervious area. There are likely several thousand properties where the overestimates are pushing a property into the next higher payment tier, and none with underestimates. This strikes me as a case ripe for a class-action lawsuit against the city, which will cost all of us money. The longer the current estimates are used, the greater the damage will be when this occurs.
If the city is to charge its residents based on impervious area, it will need to find an accurate way of measuring that area. The method being used now is simply too inaccurate to use.
Michael A. Blischke
(734) 480-5046
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Michael,
Thank you for the clarification.
Yes, our consultant did a pilot analysis of this process, analyzing automated analysis systems from 2 vendors compared with a manual analysis. The result of this pilot recognized that there would be some manual corrections required. Generally, we found that the corrections would be smaller in scope than those required on your property.
That is why we made the system as user friendly as possible. If you have access to the internet, it's a very simple process to mark up your image and send it in for an adjustment. If you don't have access to the internet, a simple phone call will get that document in the mail to you.
Once a property owner has submitted that adjustment, we are recording it as a GIS layer on our mapping. That means that in future aerial flights, we will encorporate that adjustment into the impervious area analysis. It is our intent to conduct these flights every two to three years, to capture impervious area changes from new construction and additions.
One other point I would like to make is that the tier system we are using minimizes the impact of small oscillations in the impervious area analyses. The adjustment has to be large enough to get over a tier break. We will be happy to make the adjustments in your impervious area analysis. However (as you point out), there will not be a change in the rate.
Thanks again.
Tom
From: Blischke, Michael A. [mailto:michael.blischke@gd-ais.com]
Sent: Thursday, October 11, 2007 11:51 AM
To: McMurtrie, Thomas
- Show quoted text -
Cc: Hieftje, John; Lowenstein, Joan; Rapundalo, Stephen; Greden, Leigh; Kunselman, Stephen; Higgins, Marcia; Woods, Wendy A; Teall, Margie; Easthope, Christopher; Johnson, Robert; Suarez, Ron; Hupy, Craig; McCormick, Sue; Gih, Brandi
Subject: RE: overestimates of impervious surfaces for stormwater rates
- Show quoted text -
Tom
I measured the area of my house, and my sidewalk and driveway, and came up with a little over 2600 square feet. 50 percent over 2600 is 3900. Perhaps you weren’t forwarded the JPEG image I sent to the mayor and Council, so I’m including it again. It shows all the errors mentioned in my original email, labeled and color-coded.
I did not write to Council because I expected my rates to be affected. I wrote because I believe the errors in your method of estimating impervious surface will result in systematically overestimating the error, resulting in thousands of homes across the city being charged a greater rate than is appropriate. In my case, it won’t matter, because my true impervious surface area is at the low end of the tier I am in, and your errors merely bump me into the high end of the tier.
Other residents, however, may be at the high end of their tier, and the errors of the sort on my property will bump them into the next tier. Since the city is charging us based on the area, I believe the city has a duty to prevent overestimates from happening. Instead, it seems the city has a system that will systematically overestimate residents’s impervious areas, then places the burden on all of us to find those errors and complain. And who’s to say that every resident will even be capable of realizing that, for example, including the side and front of a house is an error. Even you didn’t seem to notice that.
As long as I’m writing, what level of accuracy are you expecting from your system? Have you taken a random sample of homes, and compared the estimated areas to the true areas?
Michael
From: McMurtrie, Thomas [mailto:TMcMurtrie@a2gov.org]
Sent: Thursday, October 11, 2007 9:12 AM
To: Blischke, Michael A.
Cc: Hieftje, John; Lowenstein, Joan; Rapundalo, Stephen; Greden, Leigh; Kunselman, Stephen; Higgins, Marcia; Woods, Wendy A; Teall, Margie; Easthope, Christopher; Johnson, Robert; Suarez, Ron; Hupy, Craig; McCormick, Sue; Gih, Brandi
Subject: RE: overestimates of impervious surfaces for stormwater rates
Mr. Blischke,
Thank you for your feedback on our stormwater rates system. I am sorry to hear about your displeasure with it.
In looking at the image for your property, I would appreciate it if you could help me understand how you came up with the 50% error figure that you stated in your letter. I see some discrepencies in the shaded areas, a small grassy area in the front of your house, and the sidewalk at the front of your property (which is part of the right of way) These alone are not close to the 50% error figure, and would not be enough to change your rate. You are currently at 3908 square feet, and would need to drop to 2187 square feet to move to another tier.
Looking at the assessor's website, it shows that your building footprint is 2161 square feet. Any other impervious areas on your property would also need to be added. This would include but not be limited to: your driveway, sidewalks on your property, patios, and roof overhangs.
If you print your attached impervious area image, and highlight areas that we have incorrectly identified, we would be happy to make adjustments. If you have questions, or would like us to conduct a site visit to help with the analysis, please call me directly at 994-6581 and we would be more than willing to arrange that.
Thanks again,
Tom McMurtrie
Ann Arbor Systems Planning Unit-Public Services
P.O. Box 8647 / 100 N. Fifth Ave.
Ann Arbor, MI 48107
734.994.6581 Fax: 734.996.3064
www.a2gov.org
-----Original Message-----
From: Blischke, Michael A. [mailto:michael.blischke@gd-ais.com]
Sent: Wednesday, October 10, 2007 1:23 PM
To: Hieftje, John; Lowenstein, Joan; Rapundalo, Stephen; Greden, Leigh; Kunselman, Stephen; Higgins, Marcia; Woods, Wendy A; Teall, Margie; Easthope, Christopher; Johnson, Robert; Suarez, Ron
Subject: overestimates of impervious surfaces for stormwater rates
Councilmembers and Mayor
I am writing regarding the method used in estimating the amount of impervious surface on properties of Ann Arbor residents. These estimates are used to calculate the stormwater rates residents are paying. The method of using aerial photographs is resulting in significantly overestimating the amount of impervious surface on residents’s lots. The Stormwater rate page lists a few areas that may result in overestimates: Wood chips, shadows, and decks. In my case (see the attached image), I found that bare soil and vegetation, even when not in shadow, were counted as impervious surface. More troubling, since the pictures are taken at an angle, rather than directly overhead, they are also inlcuding the side and front of my house as impervious area, and counting some area where the roof above is also counted. This is analogous to including the area of walls and the ceiling when calculating the floorspace of a room. Further, the property lines are misregistered, so there are impervious surfaces included that are not even on my property.
All told, the impervious surface on my property was overestimated by almost 50 percent. This is a huge error. I believe the city has a moral duty to provide better estimates of impervious area. I feel it is unrealistic to put the burden of correcting these problems on the homeowners, or to even expect that all residents would be able to look at the picture provided online and be able to find the errors.
Finally, since the city is using these figures to charge residents, I believe the city also has a legal duty to not overcharge its residents. I suspect that all the photos used for calculating impervious area will all be taken at an angle, so that every lot in the city will have a significant overestimate of its impervious area. There are likely several thousand properties where the overestimates are pushing a property into the next higher payment tier, and none with underestimates. This strikes me as a case ripe for a class-action lawsuit against the city, which will cost all of us money. The longer the current estimates are used, the greater the damage will be when this occurs.
If the city is to charge its residents based on impervious area, it will need to find an accurate way of measuring that area. The method being used now is simply too inaccurate to use.
Michael A. Blischke
(734) 480-5046
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"McMurtrie, Thomas" <TMcMurtrie@a2gov.org>
to Stephen, Craig, Sue, Brandi, John, Joan, Stephen, Leigh, Marcia, Wendy, Margie, Christopher, Robert, Ron
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Oct 12
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Steve,
When a property owner requests an adjustment, we will apply that adjustment effective immediately. We don't typically issue credits for previous stormwater invoices. With some adjustments (such as the removal of a driveway or structure), there is usually no way to prove when that adjustment occured.
The reason that a roof overhang counts as impervious is that most roofs have gutters and concentrate water that creates a greater runoff. In addition, there is no practical way from aerial photographs to determine what is an overhang vs. what is the footprint.
We will be happy to make an adjustment to your impervious area analysis. We look forward to receiving your feedback.
Thanks!
Tom
From: Kunselman, Stephen
Sent: Thursday, October 11, 2007 12:55 PM
To: McMurtrie, Thomas
Cc: Hupy, Craig; McCormick, Sue; Gih, Brandi; Hieftje, John; Lowenstein, Joan; Rapundalo, Stephen; Greden, Leigh; Higgins, Marcia; Woods, Wendy A; Teall, Margie; Easthope, Christopher; Johnson, Robert; Suarez, Ron
- Show quoted text -
Subject: RE: overestimates of impervious surfaces for stormwater rates
- Show quoted text -
Tom,
If an overestimate is found to be valid and a determination is made to drop the assigned Tier to a lower level Tier, will a refund be issued by the City for the overestimation regardless of when the overestimation is corrected?
Also, can you explain what relevance a “roof overhang” has to do with imperviousness – the ground is still pervious underneath and is obviously available for infiltration of stormwater. If a house doesn’t have gutters, the stormwater hits the ground coming of the roof overhang and infiltrates on both sides of the roof overhang “plane.” Seems to me that is a little overzealous in calculating the impervious surface around the house and is quite subjective.
I’ve been overestimated too, so you’ll be hearing from me soon. Especially since my dog house and other yard art is included in my stormwater area calculation!!
Thanks, Steve
From: McMurtrie, Thomas
Sent: Thursday, October 11, 2007 7:42 AM
To: Hieftje, John; Lowenstein, Joan; Rapundalo, Stephen; Greden, Leigh; Kunselman, Stephen; Higgins, Marcia; Woods, Wendy A; Teall, Margie; Easthope, Christopher; Johnson, Robert; Suarez, Ron
Cc: Hupy, Craig; McCormick, Sue; Gih, Brandi
Subject: RE: overestimates of impervious surfaces for stormwater rates
Mayor and Council:
This is an interesting case. If you look at the aerial impervious area interpretations (attached), I would come to the conclusion that our system has worked fairly well. There are a few small areas in shadows that we missed, as well as a small grassy area out front. These might total a few hundred square feet, and would not change his rate. He is currently at 3908 square feet, and would have to drop to 2187 square feet to move to another tier.
I'm not sure where Mr. Blischke came up with the claim that we overstated his impervious area by 50%. Looking at the assessor's website, his building foot print is 2161 square feet -- but this does not include his driveway, sidewalk, patios, roof overhangs, or any other impervious area. We have never received any communications from Mr. Blishke asking for an adjustment to his impervious area or his rate.
Residents have made extensive use of our online imagery. We have received hundreds of requests for adjustments. Any adjustment that is made will be saved as a GIS image layer, so that in future flights, we will be able to identify those adjustments and apply them.
Please do not hesitate to contact me if you have any questions or comments.
Thanks!
Tom McMurtrie
Ann Arbor Systems Planning Unit-Public Services
P.O. Box 8647 / 100 N. Fifth Ave.
Ann Arbor, MI 48107
734.994.6581 Fax: 734.996.3064
www.a2gov.org
From: Hieftje, John
Sent: Wednesday, October 10, 2007 2:08 PM
To: 'Blischke, Michael A.'; Lowenstein, Joan; Rapundalo, Stephen; Greden, Leigh; Kunselman, Stephen; Higgins, Marcia; Woods, Wendy A; Teall, Margie; Easthope, Christopher; Johnson, Robert; Suarez, Ron
Subject: RE: overestimates of impervious surfaces for stormwater rates
Hello:
I appreciate your concerns with the data that has been collected and I will pass this letter on to city staff who are working on this program for their information and comment.
Thank you for writing.
John Hieftje
-----Original Message-----
From: Blischke, Michael A. [mailto:michael.blischke@gd-ais.com]
Sent: Wednesday, October 10, 2007 1:23 PM
To: Hieftje, John; Lowenstein, Joan; Rapundalo, Stephen; Greden, Leigh; Kunselman, Stephen; Higgins, Marcia; Woods, Wendy A; Teall, Margie; Easthope, Christopher; Johnson, Robert; Suarez, Ron
Subject: overestimates of impervious surfaces for stormwater rates
Councilmembers and Mayor
I am writing regarding the method used in estimating the amount of impervious surface on properties of Ann Arbor residents. These estimates are used to calculate the stormwater rates residents are paying. The method of using aerial photographs is resulting in significantly overestimating the amount of impervious surface on residents’s lots. The Stormwater rate page lists a few areas that may result in overestimates: Wood chips, shadows, and decks. In my case (see the attached image), I found that bare soil and vegetation, even when not in shadow, were counted as impervious surface. More troubling, since the pictures are taken at an angle, rather than directly overhead, they are also inlcuding the side and front of my house as impervious area, and counting some area where the roof above is also counted. This is analogous to including the area of walls and the ceiling when calculating the floorspace of a room. Further, the property lines are misregistered, so there are impervious surfaces included that are not even on my property.
All told, the impervious surface on my property was overestimated by almost 50 percent. This is a huge error. I believe the city has a moral duty to provide better estimates of impervious area. I feel it is unrealistic to put the burden of correcting these problems on the homeowners, or to even expect that all residents would be able to look at the picture provided online and be able to find the errors.
Finally, since the city is using these figures to charge residents, I believe the city also has a legal duty to not overcharge its residents. I suspect that all the photos used for calculating impervious area will all be taken at an angle, so that every lot in the city will have a significant overestimate of its impervious area. There are likely several thousand properties where the overestimates are pushing a property into the next higher payment tier, and none with underestimates. This strikes me as a case ripe for a class-action lawsuit against the city, which will cost all of us money. The longer the current estimates are used, the greater the damage will be when this occurs.
If the city is to charge its residents based on impervious area, it will need to find an accurate way of measuring that area. The method being used now is simply too inaccurate to use.
Michael A. Blischke
(734) 480-5046
Reply Reply to all Forward Invite Thomas to Gmail
Reply
Reply to all Reply to allForward Forward Print Add Stephen to Contacts list Delete this message Report phishing Show original Message text garbled?
"Kunselman, Stephen"
to Stephen, Thomas, Craig, Sue, Brandi, John, Joan, Stephen, Leigh, Marcia, Wendy, Margie, Christopher, Robert, Ron
show details
Oct 12
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Display images below - Always display images from SKunselman@a2gov.org
Tom,
Thank you for responding (and I apologize if my comments are a bit terse). I beg to differ that the City gets to arbitrarily collect overestimated storm water charges until the overestimation is discovered and then keep all the prior overestimated charges. That is a significant burden to the working families of this community who hadn’t the resources to address their stormwater rate before they got their first water bill. I just saw my stormwater rate go from $0.42/day to $0.74/day and because I didn’t get it corrected (my assessment record has my house footprint at 1116 sqft and my gravel drive way is about 900 sqft – and no sidewalks, which puts me in Tier 1, not Tier 2 as I am charged) before this first water bill came out I’m penalized? Doesn’t seem fair, nor does it seem right - I’ll be debating this policy further.
Also, just because a gutter concentrates the flow of water on a property, does not imply that it is impacting the city stormwater system with any greater volume. There are way too many variables in stormwater management to be using simplistic statements such as “gutters concentrate water contributing to greater water runoff” – regardless of the concentration of storm flow coming off the house, it’s the volume of water reaching the city system that is the issue, hence why would you give credits for rain barrels and rain gardens, but not gutter-less houses?
Thanks,
Steve
From: McMurtrie, Thomas
Sent: Friday, October 12, 2007 10:26 AM
To: Kunselman, Stephen
- Show quoted text -
Cc: Hupy, Craig; McCormick, Sue; Gih, Brandi; Hieftje, John; Lowenstein, Joan; Rapundalo, Stephen; Greden, Leigh; Higgins, Marcia; Woods, Wendy A; Teall, Margie; Easthope, Christopher; Johnson, Robert; Suarez, Ron
Subject: RE: overestimates of impervious surfaces for stormwater rates
- Show quoted text -
Steve,
When a property owner requests an adjustment, we will apply that adjustment effective immediately. We don't typically issue credits for previous stormwater invoices. With some adjustments (such as the removal of a driveway or structure), there is usually no way to prove when that adjustment occured.
The reason that a roof overhang counts as impervious is that most roofs have gutters and concentrate water that creates a greater runoff. In addition, there is no practical way from aerial photographs to determine what is an overhang vs. what is the footprint.
We will be happy to make an adjustment to your impervious area analysis. We look forward to receiving your feedback.
Thanks!
Tom
From: Kunselman, Stephen
Sent: Thursday, October 11, 2007 12:55 PM
To: McMurtrie, Thomas
Cc: Hupy, Craig; McCormick, Sue; Gih, Brandi; Hieftje, John; Lowenstein, Joan; Rapundalo, Stephen; Greden, Leigh; Higgins, Marcia; Woods, Wendy A; Teall, Margie; Easthope, Christopher; Johnson, Robert; Suarez, Ron
Subject: RE: overestimates of impervious surfaces for stormwater rates
Tom,
If an overestimate is found to be valid and a determination is made to drop the assigned Tier to a lower level Tier, will a refund be issued by the City for the overestimation regardless of when the overestimation is corrected?
Also, can you explain what relevance a “roof overhang” has to do with imperviousness – the ground is still pervious underneath and is obviously available for infiltration of stormwater. If a house doesn’t have gutters, the stormwater hits the ground coming of the roof overhang and infiltrates on both sides of the roof overhang “plane.” Seems to me that is a little overzealous in calculating the impervious surface around the house and is quite subjective.
I’ve been overestimated too, so you’ll be hearing from me soon. Especially since my dog house and other yard art is included in my stormwater area calculation!!
Thanks, Steve
From: McMurtrie, Thomas
Sent: Thursday, October 11, 2007 7:42 AM
To: Hieftje, John; Lowenstein, Joan; Rapundalo, Stephen; Greden, Leigh; Kunselman, Stephen; Higgins, Marcia; Woods, Wendy A; Teall, Margie; Easthope, Christopher; Johnson, Robert; Suarez, Ron
Cc: Hupy, Craig; McCormick, Sue; Gih, Brandi
Subject: RE: overestimates of impervious surfaces for stormwater rates
Mayor and Council:
This is an interesting case. If you look at the aerial impervious area interpretations (attached), I would come to the conclusion that our system has worked fairly well. There are a few small areas in shadows that we missed, as well as a small grassy area out front. These might total a few hundred square feet, and would not change his rate. He is currently at 3908 square feet, and would have to drop to 2187 square feet to move to another tier.
I'm not sure where Mr. Blischke came up with the claim that we overstated his impervious area by 50%. Looking at the assessor's website, his building foot print is 2161 square feet -- but this does not include his driveway, sidewalk, patios, roof overhangs, or any other impervious area. We have never received any communications from Mr. Blishke asking for an adjustment to his impervious area or his rate.
Residents have made extensive use of our online imagery. We have received hundreds of requests for adjustments. Any adjustment that is made will be saved as a GIS image layer, so that in future flights, we will be able to identify those adjustments and apply them.
Please do not hesitate to contact me if you have any questions or comments.
Thanks!
Tom McMurtrie
Ann Arbor Systems Planning Unit-Public Services
P.O. Box 8647 / 100 N. Fifth Ave.
Ann Arbor, MI 48107
734.994.6581 Fax: 734.996.3064
www.a2gov.org
From: Hieftje, John
Sent: Wednesday, October 10, 2007 2:08 PM
To: 'Blischke, Michael A.'; Lowenstein, Joan; Rapundalo, Stephen; Greden, Leigh; Kunselman, Stephen; Higgins, Marcia; Woods, Wendy A; Teall, Margie; Easthope, Christopher; Johnson, Robert; Suarez, Ron
Subject: RE: overestimates of impervious surfaces for stormwater rates
Hello:
I appreciate your concerns with the data that has been collected and I will pass this letter on to city staff who are working on this program for their information and comment.
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