HomeMy WebLinkAbout09-27-21 Public Comment - D. Sauther - Canyon GateFrom:Ross Knapper
To:Diana Sauther; Jacob Miller
Cc:Agenda; Jack Sauther
Subject:RE: Canyon Gate proposal -- storm water concerns
Date:Monday, September 27, 2021 11:19:34 AM
Dear Diana,
Thank you for contacting the City of Bozeman and for submitting your public comment for this
project. Your comments have been added to the project record.
Best,
Ross Knapper | Development Review Coordinator, Community DevelopmentCity of Bozeman | 20 East Olive St. | P.O. Box 1230 | Bozeman, MT 59771406.582.2968 | (C) 406.451.6803 | rknapper@bozeman.net | www.bozeman.net
The Department of Community Development is revising its operations until further notice to address COVID-19. We
appreciate your patience and are working hard to maintain the stability of our operations. There may be delays in
responding to inquiries. We continue to receive and review development applications. Some application types may
see delays in their review times due to the suspension of public meetings.
From: Diana Sauther <diana@tophandadvisors.com>
Sent: Friday, September 24, 2021 5:24 PM
To: Jacob Miller <jamiller@BOZEMAN.NET>
Cc: Ross Knapper <rknapper@BOZEMAN.NET>; Agenda <agenda@BOZEMAN.NET>; Jack Sauther
<jack@tophandadvisors.com>
Subject: Canyon Gate proposal -- storm water concerns
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Hi Jacob,
I understand that you are the planner assigned to the Canyon Gate proposed development atthe corner of Story Mill and Bridger. I live in the neighboring Legends neighborhood. Areyou aware that the Legends subdivision's Storm Water Master Plan to channel run-off andoverflow from Bridger Creek (and save homes from flooding) ultimately drains onto theCanyon Gate parcel? The design, approved by the City, retained the historical flows, whichmoved from the Legends area onto the Canyon Gate parcel. In fact, it appears that three of thefour historic outfalls along the western boundary of the Legends flow onto the Canyon Gateparcel. What provisions are being made to accommodate this flow? Given theunpredictability of our rapidly warming climate with its bigger and more devastating storms,proper plans and facilities for accommodating what used to be 100-year storms is even moreimportant.
Attached are both the preliminary and final plans -- as well as a side-by-side screenshot Imocked up to better visualize the drainage plan with the developed neighborhood. Below is
my layman's summary of the the key points.
Any water that overtops the banks on the south side of Bridger Creek is expected to
flow initially south and then west toward the Legends property line. Of the 4 historicoutfalls along the western boundary of the Legends, three of them flow onto theCanyon Gate parcel. "When large precipitous of flood hazard events occur, it islikely these existing flow paths or routes represent the major drainage system forthe area." (p.4 of May 2006 report) I've attached a screen shot comparing the flowsdepicted in the report side by side with the Legends as developed.
The Legends was designed with a substantial system of culverts, swales, retentionponds, etc., to:
reduce the downstream peak runoff to levels that existed pre-subdivisionbuild off of the existing topography, taking advantage of the many natural
features the contribute to storm water managementcreate three retention ponds designed to retain the 10-year post-development
runoff volume while releasing excess flow at a rate not to exceed the 10-year pre-development rate.
Pond A is 36,000 cubic ft. -- 34 acres -- and abuts the Canyon Gateproperty.
Ponds B and C are in the creek corridor near the playground area -- 6,132and 1,157 cubic ft, totaling 5.9 and 1.1 acres respectively.Overflows for precipitation events exceeding the 10-yr 2-hour willproceed downgrade along historical flow patterns.
road culverts within the Legends greenspace corridors are designed to conveyrunoff from a 25-year event without overtopping the roadway
Storms greater than a 100-yr event are expected to pass over roadways or throughemergency overflow areas
Bottom line: Any development on the Canyon Gate parcel MUST take into account thehistorical flows and be able to accommodate them through proper storm water management.
The proposal the Canyon Gate developer gave to the Legends HOA board does not seem toaddress this -- I see no retention ponds, and only 2 acres of "parkland" to be used as a trail.
On a separate note: The developer shows a new Canyon Gate Lane road tying intoNorthview. To do this, he would have to cross over Legends HOA open space; he doesn't own
that land, and thus has no right to it.
Best,
Diana
--
Diana Sauther
Top Hand Realty Advisors, Inc.
403 W. Main Street, Suite 1 Bozeman, MT 59715 Office: 406-586-0356 Cell: 406-599-3433 Fax: 406-551-1008 Diana@TopHandAdvisors.com www.TopHandAdvisors.com