Design Standards

Rules of the Washtenaw County Water Resources Commissioner

Procedures and Design Criteria for Storm Water Management Systems

Pursuant to Section 105(c) of Act 591 of the Public Acts of Michigan of 1996, as Amended and The Michigan Drain Code Public Act of 1956, as Amended

May 15, 2000

Janis A. Bobrin
Washtenaw County Drain Commissioner

 

Table of Contents


I. Introduction

i

PART 1:  PROCEDURES FOR SUBMISSION AND REVIEW OF PLATS AND CONSTRUCTION PLANS 

I. Purpose   1.1
II.   Preliminary Plat Submission and Approval   1.2
III.  Construction Plan Approval   1.5
IV.  Final Plat Approval  (Drain Commissioner Certificate)  1.8
V.   Drains Under Jurisdiction of the Drain Commissioner  1.10
VI.  Appeal Procedures  1.11

PART 2:  DESIGN CRITERIA FOR SUBDIVISION STORM WATER  MANAGEMENT SYSTEMS

I.  Subdivision Site Drainage - General Requirements   2.1
A.  Storm Water Discharge   2.2
B.  Determination of Surface Runoff   2.2
II.   Design Standards for Constructed Storm Water Management Facilities   2.3
A.  Retention and Detention Systems   2.4
  1.  General Requirements   2.4
  2.  Permanent Retention Ponds  2.8
  3.  Wet Detention Basins   2.9
  4.  Extended Detention Basins  2.10
  5.  Storm Water Wetland Systems  2.10
B.  Storm Water Conveyance  2.11
  1.  Natural Streams and Channels  2.11
  2.  Vegetated Swales/Open Ditches 2.11
  3.  Enclosed Drainage Structures  2.12
  4.  Determination of Channel Size  2.13
  5.  Determination of Culvert Size 2.14
C.  Additional Storm Water Management BMPs  2.15
  1.  Infiltration Trenches  2.15
2.  Sand Filters 2.17
III.   Natural Wetlands  2.18
IV.   Lot Grading  2.19
V. Soil Erosion, Sedimentation and Pollution Control 2.19
A.  Soil Erosion/Sedimentation Control 2.19
  1.  During Construction  2.19
  2.  Permanent Erosion Control Measures  2.20
  B.  Other Pollution Control  2.20
VI.   Buffer Strips  2.21
VII.  Floodplains  2.21
VIII. Easements 2.22
IX.   Safety Considerations 2.23
X. Storm Water Management System Maintenance  2.23

 

 

PART 3:  APPENDICES 

A. Glossary of Terms 
B. Major Categories of Nonpoint Source Pollutants 
C. Special Areas of Concern 
D. Schematics of Structural Storm Water Management Facilities 
E. Storm Water Pollutant Hotspots 
F. Criteria for Community Drain Fields 
G. Engineer's Certificate of Construction 
H. Example Extended Detention Pond Volume Calculations and Outlet Design
I. Hydrograph Soil Groups for Washtenaw County 
J. Rainfall Precipitation Data 
K. Hydrologic Soil Groups for Washtenaw County 
L. Typical Easement Language:  Subdivisions and Site Condominiums 
M. Agreement for Establishment of Private Drainage Systems as County Drains
N. Selected References for Storm Water Best Management Practices
O. Review and Inspection Fees 
P. Sample Storm Water Management System Maintenance Plan 
Q. Engineer's Certificate of Outlet 
R. General Guide to Native Plant Species 
S. Example Three Stage Outlet Design 
T. Legal Opinion Regarding Need for Easements Downstream of Drainage District Outlets; Sample Easement Form 

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