Gwinnett County’s Post Development Stormwater Management Program

1. Gwinnett County’s Post Development Stormwater Management Program

2. 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

3. Post Development • Customer Service • 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

4. 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

5. Broken Structures

6. Clogged Structures

7. Failed Pipe

8. Siphon Holes

9. 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

10. Investigations

11. 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

12. Construction Project

13. Lining Contractor

14. Finishing Up

15. 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

16. Replacement Project

17. Impact of Collapse

18. Excavation

19. New System

20. Finishing Up

21. 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

22. 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*

23. 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

24. 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.

25. Affects of Urbanization

26. Lake Haven

27. Lake Haven

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

29. Illicit Discharge