DRAINAGE DISTRICT #1 Galveston County 3722 Ave J – P.O. Box 591–Santa Fe, TX 77517-0591 – Office (409) 925-5402–Fax (409) 927-2493 [email protected] – www.gcdd1.us DANIEL WOITENA - CHAIRMAN • DENNIS WAGNER SR. - SECRETARY • D.W. WOSTAL, JR. - COMMISSIONER DRAINAGE CRITERIA MANUAL ORIGINIALY RELEASED NOVEMBER, 2007 Revision on Schedule of fees as of February 2013 Revision on Private and Public Utility crossings March 2016 Revision on Rip-Rap & Drop Pipe/Crossing Policy August 2018 GALVESTON COUNTY DRAINAGE DISTRICT NUMBER ONE SCHEDULE OF FEES The following fees will be collected by the DISTRICT prior to review and acceptance of any submittals. All review fees must be submitted at the time the plan and/or plats are submitted for review. Failure to submit the fee will result in the plat and/or plans not being considered by the District. This schedule of fees is subject to review and update by the DISTRICT Commissioners. Residential Single Lot $750.00 Residential Developments Residential………………………$700.00 + $5.00/lot (2 submittals)* Residential (>200 lots)…….……$700.00 + $5.00/lot (2 submittals)* Commercial Developments Commercial (<200 acres)………..……$700.00 (2 submittals)* Commercial (>200 acres)……..………$700.00 + $50.00 per added acre (2 submittals)* Re-submittal…………………..……….. ½ original Fee** Master Drainage Plans (> 100 acres) $2,500.00 Drainage Impact for Construction plans for specific Projects $2,500.00*** Additional Submittals (over 2 reviews) $500.00 per submittal ‘* Separate fees for preliminary and final reviews ‘** Drainage plans greater than 2 years old may be required to be resubmitted if substantial development in drainage watershed has occurred. ‘*** Reviews – 2 plan reviews GDD1 DRAINAGE CRITERIA MANUAL TABLE OF CONTENTS I. INTRODUCTION A. Purpose ......................................................................................................1 B. Policy ....................................................................................................... 1 C. Jurisdiction ................................................................................................2 D. Watersheds ............................................................................................... 3 1. Dickinson Bayou .......................................................................3 2. Highland Bayou .........................................................................4 3. Willow Bayou............................................................................4 4. Cloud Bayou ..............................................................................4 5. Halls Bayou ...............................................................................4 E. Definitions.................................................................................................5 II. ADMINISTRATION A. Submittals ................................................................................................6 B. Fees ...........................................................................................................6 C. Site Visits .................................................................................................6 D. Datum ........................................................................................................6 E. Plat Review ..............................................................................................6 F. Plat Approval ............................................................................................7 G. Drainage Plan Review...............................................................................7 H. Drainage Plan Approval ............................................................................9 I. Project Acceptance. ..................................................................................9 J. Maintenance of Storm Water Detention Facilities ....................................9 K. Time Limits of Approvals ......................................................................10 L. Revisions to Drainage Plans and Plats ................................................... 10 III. PRIVATE & PUBLIC UTILITY CROSSINGS A. Utility, Pipeline and Cable Crossings ....................................................11 B. Review Procedure ..................................................................................11 C. Submittal ................................................................................................ 11 D. Notices ...................................................................................................12 i GDD1 DRAINAGE CRITERIA MANUAL IV. HYDROLOGY A. Storm Frequency .....................................................................................13 B. Peak Storm Runoff Rates ........................................................................13 C. Frequency Factor (Cf) .............................................................................14 D. Basin Time of Concentration (Tc) ...........................................................14 E. Storm Intensity (I) ...................................................................................15 V. HYDRAULICS A. Open Channel Flow ................................................................................16 B. Closed Conduit (Pipe) Flow. ...................................................................16 VI. DETENTION FACILITIES A. General Requirements .............................................................................17 B. Volume Requirements ............................................................................17 1. Coefficient Method .................................................................17 2. Triangular Hydrograph ........................................................... 18 3. Small Watershed Method ........................................................18 4. HEC-1 Computer Modeling ....................................................20 C. Outfall Restrictor Design ........................................................................20 1. Orifice ......................................................................................20 2. Outfall Pipe .............................................................................21 3. Overflow Weir ......................................................................... 21 D. Site Grading ........................................................................................... 21 VII. DISTRICT FACILITIES A. Design Frequency ...................................................................................22 B. Design Flow Velocities ...........................................................................22 C. DISTRICT Ditch Width and Ditch Depth ..............................................22 D. DISTRICT Ditch Channel Slope ............................................................ 22 E. DISTRICT Ditch Side Slope ..................................................................22 F. DISTRICT Ditch Bottom Width .............................................................23 G. DISTRICT Ditch Horizontal Curves ......................................................23 H. DISTRICT Ditch Confluences ................................................................ 23 I. DISTRICT Ditch Transitions ..................................................................23 J. DISTRICT Ditch Drop Structures ..........................................................23 K. DISTRICT Concrete Lined Channels .....................................................23 L. DISTRICT Drop pipe and Crossing policy…………………………….24 i GDD1 DRAINAGE CRITERIA MANUAL VIII. REGIONAL & SUB-REGIONAL DETENTION FACILITIES ii GDD1 DRAINAGE CRITERIA MANUAL I. INTRODUCTION Purpose This DRAINAGE CRITERIA MANUAL (the Manual) provides a design guidance for use by developers and engineers in preparation of drainage plans for development within GALVESTON COUNTY DRAINAGE DISTRICT NUMBER 1 (the DISTRICT). It establishes rules and regulations that must be consistently followed and will be enforced throughout the DISTRICT’S jurisdiction including the portions of the Dickinson Bayou, Highland Bayou, Willow Bayou, Cloud Bayou and Halls Bayou watersheds lying within the DISTRICT’S boundaries. The design methods presented in this manual are intended to provide guidance for determination of runoff rates; methods of storm water collection, conveyance, and detention; and design standards for facilities (ditches, ponds, detention basins, etc.). Methods of design and analysis other than those included in this Manual may be considered in certain cases where there may be inherent problems with the traditional methods. However, any deviation from this Manual will require consideration and acceptance by the DISTRICT before approval will be granted for any work based on these alternatives. The creation of this Manual was authorized and funded by the Galveston County Drainage District Number 1. Policy Due to the nature of the watershed hydraulics within the DISTRICT’S boundaries and the prevalent existence of flood plains that exceed the banks of the creeks, it shall be the policy of the DISTRICT to maintain zero net increase in storm water runoff rates and to insure no negative impacts attributable to new development. Although it is the DISTRICT’S long-term goal to construct and maintain facilities (i.e., channels and regional detention facilities) that will contain 100-year storm flows within drainage rights-of-way, it is recognized that further impacts to the existing system cannot be tolerated. Therefore, the current DISTRICT policy