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
Storm Drainage Design Manual Update on Final Edits (15 Minutes)
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:
Receive an update on final edits to the Storm Drainage Design Manual
SUMMARY STATEMENT:
At the May 24th 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 storm water. Washes shall not be realigned except as approved by the Town Engineer and Community Development Director when necessary to accommodate storm water 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 for 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 language, town staff relocated the tiered system for alterations with the additional verbiage 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 is proposing 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 Hillside Wash, was incorporated to ensure consistency with the recently updated Hillside Code.
BUDGETARY IMPACT:
N/A
ATTACHMENT(S):
Attachment A - Storm Drainage Design Manual Dated 6.14.18 Clean Version
Attachment B - Storm Drainage Design Manual Dated 6.14.18 Redline Version
Attachment C - Storm Drainage Design Manual PowerPoint Presentation
Attachment D - Ordinance 2018-14
Attachment E - Resolution 2018-16