Big Creek Watershed Study Update City of Alpharetta Engineering / Public Works 1790 Hembree Road Alpharetta , Georgia 30009
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LETTER OF TRANSMITTAL October 10, 2011 JOB NO. ATTENTION: Ms. Jill Bazinet TO: Ms. Jill Bazinet P.E. RE: Final Draft Big Creek Watershed Study Update City of Alpharetta Engineering / Public Works 1790 Hembree Road Alpharetta , Georgia 30009 WE ARE SENDING YOU ATTACHED ELECTRONICALLY UNDER SEPARATE COVER THE FOLLOWING ITEMS: SHOP DRAWINGS PRINTS PLANS CERTIFICATION COPY OF LETTER PAYROLLS REPORT CD COPIES DATE NO. DESCRIPTION 1 10.10.2011 Final Draft Big Creek Watershed Study Update THESE ARE TRANSMITTED AS CHECKED BELOW FOR APPROVAL NO EXCEPTION TAKEN SUBMIT COPIES FOR DISTRIBUTION FOR YOUR USE/FILES MAKE CORRECTIONS NOTED RETURN CORRECTED COPIES AS REQUESTED AMEND AND RESUBMIT RESUBMIT COPIES FOR APPROVAL FOR REVIEW AND COMMENT REJECTED - (SEE REMARKS) RETURN APPROVED COPIES REMARKS: COPY TO: File SIGNED: Amanda Lester IF ENCLOSURES ARE NOT AS NOTED, KINDLY NOTIFY US AT ONCE 580 W. Crossville Road Suites 101-102 Roswell, Georgia 30075 October 10, 2011 Jill Bazinet P.E. City of Alpharetta, Georgia Engineering / Public Works 1790 Hembree Road Alpharetta, GA 30009 Re: Final Big Creek Watershed Study Update Dear Ms. Bazinet: River To Tap (R2T) is pleased to provide the attached final draft of the Big Creek Watershed Study Update for the Cities of Alpharetta and Roswell. This update includes information and activities related to water supply watershed protection that have been implemented since the Big Creek Watershed Study was developed in 2000. The final draft identifies updated land use percentages for the Department of Community Affairs Part 5 Criteria for Environmental Planning. John West of the DCA was contacted to confirm that the impervious percentages would not limit the Cities ability to comply with the Part 5 Criteria. Other updates in the final draft include best management practices identified specifically within Wills Park a City of Alpharetta owned property. R2T, Inc. is committed to providing the municipalities with a quality Big Creek Watershed Study Update that will be used to comply with existing State and regional plans and regulations. Please call me at (770) 569‐7038 ext. 103 if you have any questions on our qualifications, the scope of work, project schedule or cost. Sincerely, R2T, INC. Amanda Lester cc: Kimberly Ajy Project Engineer Project File 580 W. Crossville Road Suites 101-102 Roswell, Georgia 30075 Big Creek Watershed Study Update Executive Summary This study presents an update to the Big Creek Watershed Study prepared by Camp Dresser & McKee in 2000 under the guidance of the Atlanta Regional Commission (ARC). The purpose of this document is to ensure that active participants, including the Cities of Alpharetta and Roswell, comply with the current federal, state, and local requirements. The Big Creek basin is located in Cities of Alpharetta, Roswell, Milton, Johns Creek, Cumming, and Forsyth, Fulton and Cherokee Counties of Georgia. The watershed provides recreational and scenic value to the various jurisdictions and serves as a water supply source for the City of Roswell. The southern portion of the watershed is more developed than the northern portion as it lies within the Cities of Alpharetta and Roswell. Developed areas in the northern portion of the watershed are primarily within the City of Cumming. The watershed occupies an area of approximately 99 square miles at the Roswell water treatment plant intake. The characteristics of the Big Creek watershed summarized in this study include location, soil type, topography and land use. Water quality data from the Cities of Alpharetta and Roswell are included to summarize the health of the streams within the Big Creek watershed. Potential pollution sources within the watershed have also been identified using GIS mapping and local resources. Historically, ordinances and regulations regarding water quality varied between jurisdictions located in the watershed. However, each jurisdiction in the Big Creek watershed is now a member of the Metropolitan North Georgia Water Planning District (District). One of the District’s goals is to provide consistency and regulatory compliance and accountability among jurisdictions in the greater Atlanta area to benefit water quality. The watershed management requirements of the District are identified in Section 3 of this report. The official code of Georgia and the Georgia Planning Act establishes requirements for small water supply watersheds. The requirements for these watersheds are identified in this study, as well as necessary measures the Big Creek jurisdictions can take to meet these requirements. Future land use conditions that are managed by improved ordinances and include stormwater best management practices (BMPs) throughout the watershed provides the best opportunity to achieve water quantity, water quality and community goals. Recommendations for source and treatment controls to implement within the Big Creek watershed are identified in Section 6 and are presented by three categories in Table EX.1, including Public Awareness and Public Involvement, Non‐structural Measures and Structural Measures. i TableEX.1 Big Creek Watershed Study Recommended BMPs for Big Creek Watershed Newsletter Public Awareness and Public Awareness to Reduce FOGs Public Involvement School Education Activities Homeowner Education Workshops Septic Tank Elimination Program Increased Water Quality Monitoring Debris Removal from Structures Non‐structural Measures Bacteria Source Tracking Neighborhood of Environmental Excellence Greenspace Acquisition and Management Stormwater Detention Basin – Wills Park Stormwater Detention Basin – Liberty Square Stormwater Detention Basin – Carriage Station Stormwater Detention Basin Retrofits Structural Measures Rain Gardens – Wills Park, Waller Parks Rain Barrels – Wills Park, Waller Parks Stream Bank Restoration (Various Locations) Disconnect Impervious Surfaces Reduce Impervious Surfaces Low Impact Development/Redevelopment and Green Infrastructure Alum Treatment of Regional Detention Ponds ii Table of Contents Section 1 Introduction .................................................................................................................................. 1 1.1 Overview ............................................................................................................................................. 1 1.2 Purpose ............................................................................................................................................... 1 1.3 Background ......................................................................................................................................... 1 1.4 Goals and Objectives ........................................................................................................................... 4 Section 2 Watershed Characteristics ............................................................................................................ 5 2.1 Description of the Watershed ............................................................................................................. 5 2.2 Topography ......................................................................................................................................... 7 2.3 Climate ................................................................................................................................................ 7 2.4 Soils ..................................................................................................................................................... 9 2.5 Land Use ............................................................................................................................................ 11 2.5.1 Existing Land Cover .................................................................................................................... 11 2.5.2 Future Land Cover ...................................................................................................................... 11 2.6 Potential Pollution Sources ............................................................................................................... 14 2.7 Sanitary Sewer Overflows and Septic Tanks ..................................................................................... 17 2.8 Water Quality Data ........................................................................................................................... 17 2.8.1 Water Quality Monitoring.......................................................................................................... 19 Section 3 Regulatory Review....................................................................................................................... 24 3.1 Introduction ...................................................................................................................................... 24 3.2 Metropolitan North Georgia Water Planning District....................................................................... 25 3.3 Part 5 Environmental Criteria ........................................................................................................... 26 3.3.1 Requirement ‐ 1 Area within a Seven Mile Radius .................................................................... 26 3.3.2 Requirement – 2 Areas outside a Seven Mile Radius ................................................................ 27 3.3.3 Requirement 3 – Entire Watershed ........................................................................................... 28 Section 4 Estimating