Next steps in Paradise Valley storm water management appear muddled

Paradise Valley officials gather Thursday, Feb. 9 at Town Hall to discuss potential storm water mitigation efforts. (Independent Newsmedia/Terrance Thornton)

The severity of property damage that could be caused by storm events typical for the Town of Paradise Valley appears to be largely unknown.

Paradise Valley Town Council held a study session discussion Thursday, Feb. 9 at Town Hall, 6401 E. Lincoln Drive, to hear the details of the Cheney Watershed Alternatives Analysis.

Town staff, along with Bob Haneline of Dibble Engineering, presented to town council four options — each varying significantly in cost — to help mitigate flood issues up to a 10-year storm event in the town identified watersheds.

The Cheney and Cherokee watersheds are largely bound by Scottsdale Road to the east, Indian Bend Road through Mummy Mountain to the south, along Tatum Boulevard to the West and up to Doubletree Ranch Road to the north.

A major focus of the Feb. 9 discussion was updating the 1987 Storm Drain Design Manual, which will now be dubbed the Storm Drainage Design Manual, and how revisions speak directly to retention requirements on what town officials call, “Hillside Properties.”

Over the last 18 months, the Town of Paradise Valley has been conducting a water flow study specific to both the Cheney and Cherokee watersheds — an effort to understand where the water flows in that part of town.

On Sept. 8, 2014 the Town of Paradise Valley experienced a level of rain exceeding what is known as a 100-year storm event that left an estimated 80 homes flooded in what town officials have coined the Cheney and Cherokee watersheds.

That flood and one that occurred in 2013 of a similar magnitude spurred an interest in where water flows within town limits, town leaders agree.

A flood level, or flood stage, is the level at which water is risen to a sufficient level — typically measured at 100-year events — to flood areas not normally covered by water, causing a threat to life or property.

Kevin Burke

“The town could start looking at creating infrastructure that reduces inundation. We also could work in partnership with Maricopa County on mutual projects,” said Town Manager Kevin Burke at the Feb. 9 work session. “They are looking at implementing a tax that would be on the macro level.”

Turns out, the Maricopa County Flood District is conducting its own study based on 10-year flood levels due to funding restrictions, Paradise Valley town officials say.

“We are looking at the information and choices defined by the Cheney and Cherokee watersheds,” Mr. Burke said of the town study working parallel with Maricopa County.

“With each and every application, we are looking at the storm manual and trying to address and mitigate some of those impacts. There are some policy choices in there on just how many mitigation levels you want. While storm water is serious and impactful, we don’t want to rush these decisions.”

The Town of Paradise Valley — up until about 18 months ago — was allowing all new or remodeled homes on what town officials designated as a “hillside property” to skip storm water retention requirements as allowed per town code, officials contend.

The Paradise Valley Hillside Committee was created in 1996 and is governed by Article XXII of the town’s zoning ordinance whereas members are charged with reviewing applications for building permits in the Hillside Development Area.

Membership on the committee consists of three members of the Planning Commission and two residents appointed by the mayor and confirmed by town council.

This graphic depicts the general area of both the Cheney and Cherokee watershed study areas. (Submitted graphic)

Wait and see

Jeremy Knapp, Paradise Valley engineering analyst, presented the options to help mitigate a 10-year flood level in the Cheney Watershed.

Jeremy Knapp

The program would be a series of infrastructure improvements to certain areas of the perimeter of the Cheney watershed. Depending on the level of inundation needed to correct, the town could spend somewhere between $11 and $19 million.

“One of the options is to use mapping and data collection to act as a policy guide for future development,” Mr. Knapp said at the work session discussion. “Essentially it relies upon the Storm Drainage Design Manual to give guidelines for all private development.”

Each of the options ranged from do nothing to the pursuit of new infrastructure projects to mitigate flood waters.

“The Maricopa County flood district is basing all of its policies on a 10 year-event due to funding,” Mr. Knapp pointed out of the baseline data used for the Dibble Engineering flood models.  “That’s a much larger effort than what we got. This mapping helps us identify where there are issues generally.”

The data presented had Paradise Valley Councilman Paul Dembow scratching his head.

“I don’t know how to make any sense of the data that you have provided,” he said pointing to data for a 10-year event while the town is experiencing levels of flooding that far exceed that saturation level. “I feel badly and I would definitely map it but I know everybody in this room knows they have a problem.”

Mr. Dembow says money spent on the current studies may not be addressing the unique issue the Town of Paradise Valley faces.

“Is it going to get better if we spend this money or is that something we can’t quantify?” he asked of the infrastructure options. “The money that we spent on these studies doesn’t address the problem?”

Paradise Valley Vice Mayor Jerry Bien-Wilner says he wants to see the maps created and data collected be used when evaluating all future private development within town limits.

“I think option four was something I always envisioned when these studies were approved,” he said of using current data to evaluate building pursuits in the private sector. “I can’t imagine a reason not to do that.”

Northeast Valley Managing Editor Terrance Thornton can be contacted at tthornton@newszap.com

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