TO: Mayor Collins and Town Council Members
FROM: Kevin Burke, Town Manager
Brent Skoglund, Public Works Director
Jeremy Knapp, Engineering Services Analyst
DATE: March 23rd, 2017
DEPARTMENT: Public Works and Engineering Department
Staff Contact Jeremy Knapp, Engineering Services Analyst
480-348-3622
End
AGENDA TITLE:
Title
Storm Drainage Design Manual Revisions Summary and Update
Body
Council Goals
Storm Water - Identify the scope, scale and possible solution to recurring storm water management issues.
SUMMARY STATEMENT:
At the February 9th Town Council Meeting staff presented the proposed Storm Drainage Design Manual, highlighting some of the updates and changes. 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 20th. 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 Paradise Valley Independent, and placed ads on the TV screens at Town Hall. On March 21st, staff held a public meeting in the Community Room to present the draft and receive public input. A summary of the input will be presented at the March 23rd Council Meeting.
Several Council questions required additional information which will be presented, including a request to highlight any new requirements and possible costs associated with implementing them. Staff has prepared a table summarizing both.
Two options are outlined to adopt the document. The first, recommended option, is to adopt the manual as presented which includes the following policy decisions:
1. Use the distrurbed area only for flatland retention calculations
2. Hillside retention requirements on a tiered scale
3. Addition of first flush requirement for first ½” of rainfall
The second option is to adopt the manual as presented but remove the three recommended policy decisions and continue to enforce current policy until a new Town Engineer is selected and had an opportunity to get up to speed. The current policy is:
1. Use the entire site for flatland retention calculation
2. Calculate hillside retention as current code states “is required but may be waived in cases where the average slope of the property exceeds 5%”
3. Do not require first flush retention for first ½” of rainfall
Text from February 9th Council Memo:
The Storm Drainage Design Manual is a document utilized by Town staff to review and approve improvement plans and storm water master plans on a day-to-day, lot-by-lot basis. It sets Town specific standards utilized by developers and builders to design and implement 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 current Storm Drain Design Manual was adopted in 1987 and has never been amended. One of Dibble Engineering’s (consulting engineer) tasks associated with the on-going watershed studies project is 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. The revised updated manual is being presented in Work Study Session for comment and direction on adoption process.
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. Storm water 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.
Policy decisions are requested regarding first flush requirements, flatland retention requirements for single family residences and non-residential development, and hillside retention requirements.
ATTACHMENT(S):
Storm Drainage Design Manual
Storm Drainage Design Manual PowerPoint Presentation