Rule Change Update MPCA 1/13/05

1. Rule Change UpdateMPCA1/13/05

2. 7081 Mid-Sized ISTS (MSTS)

3. I. Scope • A. Standards to reasonably protect surface water, ground water, and public health, safety, and general welfare.

4. I. Scope • B. Mainly performance outcomes provided with some prescriptive design, construction, and operational standards.

5. I. Scope • C. Systems designed under this part may require additional design requirements pursuant to EPA Class V regulations.

6. I. Scope • Chapter 7081 - mid-sized ISTS (MSTS) • Multiple dwellings or Other Establishments - 2,500 to 10,000 gpd

7. I. Scope • Sewage collection system • Piping, lift stations or components that conveys sewage • On-lot sewage tank = MSTS

8. I. Scope • H. Administration of chapter 7081 standards is done by local permitting authorities.

9. SDS Permit Threshold • One or more systems • Average daily flow of greater than 10,000 gallons per day • ½ mile radius • Single ownership • ????????????????????

10. SDS Permit Threshold • Any system the commissioner has determined needs a SDS permit. • Flow amounts to determine if an SDS permit is required must be per 7081.0110

11. Performance and Compliance Criteria • No contact with sewage. • Safe systems - protection from physical injury and harm. • Accepted no hazardous material.

12. Performance and Compliance Criteria • Groundwater protection • No fecal organism in groundwater • Systems that comply with any nitrogen or phosphorus standard

13. Performance and Compliance Criteria • Other conformance • In conformance with the operating permit.

14. IV. Professional Requirements. • A. MSTS Designer • B. Installer • C. MSTS Inspector • D. Maintainer • E. Service Provider

15. Sewage Flow Determination • Dwellings • Use Type II flows for 10+ dwellings

16. V. Sewage Flow Determination • Other • Include 200 gallons of infiltration and inflow per inch of collection pipe diameter per mile per day.

17. VI. Soil And Site Evaluation • Normal preliminary evaluation plus: • Distance to surface water • Waste strength

18. Soil And Site Evaluation • Soil pits required - one pit per corner and one the center, plus one additional soil pit per 10,000 ft2.

19. Soil And Site Evaluation • Must determine perc rate by both water testing and texture, structure and consistence.

20. Groundwater Investigation • A preliminary groundwater evaluation for all MSTS

21. Groundwater Investigation • A determination of : • shallow groundwater setting • regional groundwater setting • aquifer(s) used for water supply • wells • groundwater flow direction

22. Groundwater Investigation • A determination if contaminant plumes may intersect water supply wells capture zones

23. Groundwater Investigation • An estimation of the extent of groundwater mounding from the operating system. • The accuracy of the approximation shall be determined

24. Groundwater Investigation • The designer must consult with the permitting authority for the extent of any further investigation or monitoring

25. Design Standards. • A flow measure device must be employed on all MSTS.

26. Design Standards. • The system must be designed with sufficient access and ports to monitor the system as applicable.

27. IX. Sewage Tanks. • Septic tank size = average daily flow by 3.0. • Septic tank size under pressure = the average daily flow by 4.0.

28. Sewage Tanks. • Septic tank capacity prior to other treatment devices, shall be per manufacturer’s requirements or accepted engineering principals.

29. Sewage Tanks. • Tanks shall be connected in series. Parallel OK if sufficient justification is provided and adequate monitoring is provided.

30. Sewage Tanks. • All tanks used for MSTS shall be tested for water tightness. • Food preparation facility, shall install an external grease trap.

31. Distribution Of Effluent. • Distribution in accordance with 7080.0160 • Designed for a 2 foot head.

32. DOSING OF EFFLUENT. • Dosing in accordance with 7080.0160

33. Final Treatment and Disposal. • Systems setback from site boundaries, downgradient of groundwater flow 50’ + ((average design flow – 1500) x .03’)

34. Final Treatment and Disposal. • Sized with a 50% increased plus 50% reserve. (not for less than 2,500 gpd).

35. Final Treatment and Disposal. • Sizing • Hydraulic • flow • soil • gw mounding • Nitrogen • Phosphorus • Organics (biomat) • Pathogen removal

36. Final Treatment and Disposal.

37. Final Treatment and Disposal. • Separation Distance depends on: • Soil texture • Loading rate • Dosing frequency • System width and depth • Capillary fringe • Groundwater mounding • Concentrations of contaminants • Hydraulic head • Factor of safety

38. Final Treatment and Disposal. • An unsaturated zone must be maintained. • Measure the height of the seasonally saturated soil during operation. • Systems might need to employ nitrogen and phosphorus reduction methods.

39. XConstruction • Designer must observe critical periods of system construction

40. Operation and Maintenance. • Operated under a local operating permit

41. System Ownership and Responsibility • Apply for and obtain construction and operating permits; • Ensure submittal of required reporting and compliance status to the permitting authority; • Negotiate contracts as necessary; • - recover costs of damages to the system; • - able to obtain financing

42. System Ownership and Responsibility • Provide annual education to users on suitable discharges; • Monitor compliance with local ordinances requirements • - financial instrument to continue the operation, maintenance, management, repairs, of the system for a period of one year