TO: Mayor Collins and Town Council Members
FROM: Kevin Burke, Town Manager
Paul Mood, P.E., Town Engineer
Jeremy Knapp, Engineering Services Analyst
DATE: June 14th, 2018
DEPARTMENT: Engineering
Staff Contact Paul Mood, P.E., Town Engineer, 480-348-3573
End
AGENDA TITLE:
Title
Adoption of Ordinance 2018-14 Amending Chapter 5 Building and Construction, Section 5-10-3, Storm Drain Design of the Town of Paradise Valley Town Code and Adoption of Resolution 2018-16 Declaring Said Document a Public Record
Body
Town Value(s):
☐ Primarily one-acre, residential community
☐ Limited government
☐ Creating a sense of community
☐ Partnerships with existing schools and resorts to enhance recreational opportunities
☐ Improving aesthetics/creating a brand
☒ Preserving natural open space
Several sections of the Storm Drainage Design Manual require the preservation of washes in their natural state
Council Goals or Statutory Requirements:
For efficient and effective execution, review and seek improvements for planning, timing, and coordination of infrastructure maintenance and enhancement
RECOMMENDATION:
Recommendation
Adopt Ordinance 2018-14 and Resolution 2018-16
Background
SUMMARY STATEMENT:
Between the years of 2012 and 2015 the Town of Paradise Valley and the Phoenix Metro Region experienced a number of intense storm events, causing damage to private and public property. In February and April of 2015 the Town Council held Community Conversations to better understand the issues, concerns of residents, and potential challenges. Recognizing a need to address these concerns and challenges, the Town Council awarded a contract to Dibble Engineering in October of 2015 to study the town’s watersheds and update the town’s Storm Drainage Design Manual (SDDM).
The SDDM is a document utilized by Town staff to review and approve improvement plans and stormwater master plans on a day-to-day basis. It sets Town specific standards utilized by developers and builders to design, implement, and maintain drainage improvements on private property. In addition, the Town uses it for guidance on stormwater improvements included in Town designed and constructed projects.
The Town’s previous Storm Drain Design Manual was adopted in 1987 and has never been amended. One of Dibble Engineering’s tasks associated with the watershed studies project was to update the manual. Town staff received a first draft of the updated manual in August of 2016. A staff stormwater committee, which consisted of representatives from the Building Department, Planning Department, Code Enforcement, Engineering, Public Works, and the Town Manager, reviewed the document and provided comments. In February of 2017 town staff presented the first draft of the SDDM to Town Council.
The revised document addresses many new regulations enacted since 1987 as well as some policy decisions. The new regulations include:
1. First flush requirements;
2. Stormwater quality during and after construction;
3. Updated rainfall data and engineering practices;
4. Incorporation of all aspects of stormwater management (floodplain management, erosion hazards, etc.);
5. Introduction of low impact development; and,
6. Specific guidance on drainage reports, plans, easements, etc.
Major policy decisions were necessary regarding first flush requirements, flatland retention requirements for single family residences and non-residential development, hillside retention requirements, and low impact development incentives. The discussion led to several Town Council questions which needed further input as well as council request for public comment.
The Engineering Department began publicizing the draft document, advertising a public meeting, and soliciting public comment the week of February 20, 2017. Staff utilized the town’s website, e-mailed the notify me builders list, placed flyers at the Building and Engineering Departments counters, published a noticed in the March 8th 2017 Paradise Valley Independent, and placed ads on the TV screens at Town Hall. On March 21, 2017 staff held a public meeting in the Community Room to present the draft and received public input. A summary of the input was presented at the March 23, 2017 Council Meeting.
In light of comments received by Council and the addition of a new Town Engineer, it was staff’s recommendation to address the outstanding policy issues before the summer recess with Town Council. During the summer recess staff continued to address non policy Council comments, text clean up, and final formatting and presented a revised version in the fall of 2017.
The outstanding policy issues included:
Retention Basin Easements (Section 7-1):
Eliminate the requirement for retention basin and access easements and utilize a recordable document that documents stormwater facilities on private property that would show up on Schedule B of a title report.
First Flush (Section 3-2-B.2):
First flush requirements are required in two circumstances:
1. SUP properties; and,
2. Hillside Properties that do not provide any retention due to their building pad slope (above 30%)
Parking Lot Storage (Section 3-2.B.16):
Parking lot storage is permitted only for SUP properties.
Natural Wash Preservation (Section 3-6.A.2)
There are currently Town Code sections that require property owners to maintain washes in their natural state as they cross private property to preserve open space and natural character of the town. The proposed Storm Drainage Design Manual furthers these town code sections with additional clarifications on when washes can be altered. Generally speaking, the preservation of natural washes is an important town value, but it is also recognized that sometimes it is necessary to alter certain washes to accommodate private property development. The manual was updated to include a three tier approach to washes and their alteration.
At the May 24, 2018 Town Council Meeting Town Council provided staff direction on the policy of wash modification and preservation to incorporate into the Storm Drainage Design Manual (SDDM). The direction received was to re-write section 3-6 of the SDDM to reflect current town code requirements regarding said modification and preservation. The updated SDDM Section 3-6 reads as follows:
Washes are to remain in an undisturbed state except for modifications approved by the Town Engineer that are required to accommodate stormwater. Washes shall not be realigned except as approved by the Town Engineer and Community Development Director when necessary to accommodate stormwater or to restore a disturbed wash to a more natural state. When assessing if a wash can be modified, the Town Engineer and Community Development Director will use the guidelines set forth in Appendix 1-C - Wash Alteration Request Guidelines.
In all cases, wash alterations must maintain the locations of inflow onto the property and outfall from the property and have no adverse impacts on other property owners as documented in a drainage report signed and sealed by a professional engineer. Additionally, a drainage easement for protection and access of the wash shall be dedicated to the Town per Section 7, Drainage Easements and Recorded Agreements.
Washes that are located on properties designated as Hillside and meet the definition of a Hillside Wash, shall not be diverted, relocated or moved from its present position to another location, however, a Hillside Wash may be bridged by a structure so long as the structure does not impede the flow of the Hillside Wash in accordance with hillside regulations.
Consistent with this direction, town staff relocated the tiered system with the additional language for modification within a fenced-in backyard to an appendix titled “Wash Alteration Request Guidelines” for consideration by the Town Engineer and Community Development Director when processing such requests for modification.
Furthermore, town staff has proposed language to specify how cross sections of existing washes are utilized to calculate the washes width and depth. The proposal is:
To determine if a wash meets the definition of a Natural Wash or Hillside Wash, five cross sections of the wash equally spaced across the property shall be provided. If three or more of the cross sections are at least 2 feet deep from the top of the bank and 5 feet wide to the top of the bank, the wash is considered a Natural Wash or Hillside Wash.
One final edit, revision of the definition of Natural Wash, was incorporated to ensure consistency with the recently updated Hillside Code.
BUDGETARY IMPACT:
N/A
ATTACHMENT(S):
Attachment A - Ordinance 2018-14
Attachment B - Resolution 2018-16
Attachment C - Storm Drainage Design Manual Dated 6.14.18 Clean Version
Attachment D - Storm Drainage Design Manual Dated 6.14.18 Redlined Version
Attachment E - Storm Drainage Design Manual PowerPoint Presentation