Gwinnett County’s Post Development Stormwater Management Program

Three Stage of Stormwater Management Stage One: Plan Review Approve designs Assure proper erosion and sediment control Check calculations and drainage areas Make necessary comments for revision Stage Two: Development Conducts detention pond inspections Assure compliance with codes and regulations Issue violations and fines Stage Three: Post Development Maintenance of infrastructure Citizen complaints Post development detention pond inspections Compile post development statistics

Post Development Customer Service Construction & Maintenance Drainage Complaints Construction & Maintenance County Crews and Demand Contractors Engineering Department Creates the Designs for County Projects Watershed Improvement Watershed Assessments and Stream Restoration Environmental Compliance Illicit Discharge and Water Quality Monitoring

Customer Service Gwinnett County maintains all the pipes and structures within and connected to the Public right-of-way* *Do not maintain drainage structures on commercial property *Do not maintain drainage structure within city limits, except Lilburn Citizens may call or go on-line to report a problem Broken structures Clogged pipes Failed pipe Siphon holes Illicit discharge, part of environmental compliance

Broken Structures

Clogged Structures

Failed Pipe

Siphon Holes

Investigative Tools GIS data is extremely helpful The Final Plat is the official record of property and inventory Our camera is definitely the most useful tool Basic equipment- Gloves, manhole hook, safety vest, flashlight, and map book

Investigations

Construction and Maintenance Service ticket is turned in Construction manager assigns project County work crews Demand Contractor List completed by priority Emergencies first Received date

Construction Project

Lining Contractor

Finishing Up

Cost of Project Lined 467 feet of pipe, replaced 1 headwall, and rocked ditches Estimated Cost $214,000 Actual Cost $142,000 Cost per foot ≈ $304.07

Replacement Project

Impact of Collapse

Excavation

New System

Finishing Up

Cost of Project Replaced approximately 100 ft. of pipe Set two new junction boxes Replaced water vault and relocated sewer line Excavation and repaving Estimated Construction $325,000 Actual Cost ??? Cost per foot ≈ $3,250

Cost Benefit for Developer Always the bottom line Do the bare minimum Use the cheapest pipe possible HDPE: 18”x20’ $141.20 Cost per foot $7.06 CMP: 18”x20’ $250.80 Cost per foot $12.54 RCP: 18”x8’ $110.88 Cost per foot $13.86 Installation costs are much lower with the CMP*

Gwinnett County Infrastructure Gwinnett County is 437 square miles Population of nearly 800,000 Approx. 2,091.5 miles of stormwater pipes 53.4% Corrugated Metal 25.6% Aluminized Steel 18.8% Reinforced Concrete 2% HDPE/PVC .2% Miscellaneous Gwinnett maintains 1,296.2 miles Approx. 178,914 stormwater structures Gwinnett Maintains 111,575 structures

Gwinnett County Strategic Asset Management Plan “To plan, create, acquire, maintain, operate, rehabilitate, replace and dispose of assets in the most cost-effective manner while providing established level of service for present and future generations.” Rate or grade pipes and/or pipe systems on the following criteria Corrosive Soils Age, % of remaining useful life Material Number of Recorded Failures Maintenance History Goal: Ensure that desired service levels and other operational objectives are achieved at optimal cost.

Affects of Urbanization

Lake Haven

Lake Haven

Total cost including engineering and construction $426,805 Post Construction Total cost including engineering and construction $426,805

Illicit Discharge