Type III Systems. MOWA Winter Convention 2015 MPCA

Transcription

1 Type III Systems MOWA Winter Convention 2015 MPCA

2 Introduction Generally, a Type III system is a Type I system that has to deviate due to soil, site or waste strength problems.

3 Type I System Deviations from Type I must be submitted to the local unit of government for approval or denial.

4 Rule Language TYPE III SYSTEMS has many references to other rule parts

5 Core Requirements The core requirements (basic performance outcomes) are found in subpart 2. All system Types need to meet these.

6 Core Requirements Meet other state rules Floodplain Setbacks No exposed sewage No pathogens in ground water Maintain unsaturated zone Nitrogen requirements (2.5 5k gpd)

7 Type I Requirements

8 Type I Requirements Type III systems need to meet the following Type I requirements:

9 Flow Must use Type I flow values as they are used for system classification (ISTS, Large ISTS, MSTS, SDS Permit) Can t use Type III design lower the classification

10 Flow Example: the calculated design flow is 3,000 gpd, therefore nitrogen treatment may be a part of the design. Can t be creative with the flow and then label the system as Type III (this is true for all classifications even Type V).

11 Distribution System Type III s must meet Type I distribution requirements. Supply pipes Gravity distribution Pressure distribution

12 Distribution System So above ground Type III systems need to have pressure distribution

13 Distribution System Changing the distribution system is a Type V system.

14 Tanks Type III s must meet Type I tank requirements Registered tanks Size Location Baffling etc

15 Tanks Changing tank requirements is a Type V system.

16 Dosing Type III s must meet Type I dosing requirements Timed dosing can be used

17 Other General Type I Requirements Type III systems must: Use Registered products Long lasting structural components Three-foot vertical separation distance

18 Other General Type I Requirements cont.

19 Other General Type I Requirements Account for rock fragments (35 to 50% and >50%)

20 Other General Type I Requirements Treatment zone within seven feet of final grade Soil Treatment Zone 7 feet

21 Other General Type I Requirements 30 hydraulic head in media

22 Other General Type I Requirements cont. No media contact with fast per-rate soils

23 Other General Type I Requirements cont. Fabric on top of rock media

24 Other General Type I Requirements cont. Six inches of topsoil cover

25 Other General Type I Requirements cont. Good vegetative cover

26 Other General Type I Requirements If not meeting these requirements, the system is a Type V

27 Specific Type I Requirements

28 Specific Type I Requirements Specific spec would be the use of clean sand for mounds

29 Review Review Type III systems need to be the ALL Type I requirements (general and specific).

30 Type III Differences

31 Type III Differences We will now go over the specific areas where Type III s can differ.

32 Flow Measurement Type III s must have flow measurement

33 Flow Measurement Since Type III s mainly deal with hydraulic ones, flow measurement is required for troubleshooting potential problems

34 Flow Measurement Therefore an operating permit is suggested which has regular readings of the measured flow along with periodic observation of hydraulic problems.

35 Original Soil A Type III system does not need to be in/on original soil

36 Original Soil "Original soil" means naturally occurring soil that has not been cut, filled, moved, smeared, compacted, altered, or manipulated to the degree that the loading rate must be reduced from that associated with natural soil conditions.

37 Original Soil The disturbance can occur in the past and identified in the design, or The disturbance can happen after the design (requires re-design)

38 Original Soil Disturbance in the past Cut Filled Compacted

39 Original Soil System construction damage includes: Plastic limit Equipment damage Rainfall damage

40 Original Soil Normal agricultural activities do constitute soil damage, unless: End rows Pasture Feed lot Field lane Obvious damage

41 Type III Sizing Type III systems must start out by trying to size according to Table IX Texture/Structure/Consistence or Table Ixa Perc Test

42 Type III Sizing There are three reasons the sizing is unique: 1. The site is too small 2. The natural (undamaged) soil has too fast or too slow perc rate 3. The soil has been damaged

43 Type III Sizing Small Site Site is too small

44 Type III Sizing Small Site If the site is too small, then build the system as large as practical and then use a timer so as not to exceed the flow.

45 Type III Sizing Small Site The other option is to use pretreatment and get a size reduction under Type IV (~ 25% reduction). But will need room for the extra tanks.

46 Type III Sizing Poor Natural Soil The natural (undamaged) soil has too fast or too slow permeability

47 Type III Sizing Poor Natural Soil Too fast permeability

48 Type III Sizing Poor Natural Soil If the soil has greater than 35% rock fragments in the absorption area. Install media in different horizon Liner Mound

49 Install media in different horizon

50 Install media in different horizon

51 Liner Clean Sand

52 Mound

53 Type III Sizing Poor Natural Soil Too slow permeability (natural soil that is clay, silty clay, etc.) No value given in Table IX Default do a perc test

54 Table IX USDA soil texture Clay, sandy clay, silty clay Soil structure and grade Treatment Level C Absorption area loading rate (gpd/ft 2 ) Treatment Level C Mound absorption ratio Treatment Level A, A- 2, B, B-2 Absorption area loading rate (gpd/ft 2 ) Treatment Level A, A- 2, B, B-2 Mound absorption ratio*** - ** ** ** **

55 Type III Sizing Poor Natural Soil If you don t get a fast enough perc rate to be within Table IXa then: Use your best estimate Type IV system no clogging mat may help (system is now both a Type III and Type IV) Holding tank

56 Percolation rate (MPI) Treatment level C absorption area loading rate (gpd/ft 2 ) Treatment level C mound absorption ratio Treatment levels A, A- 2, B, and B-2 absorption area loading rate (gpd/ft 2 ) Treatment levels A, A- 2, B, and B-2 mound absorption ratio >

57 Type III Sizing - Damage Soil The soil has been damaged

58 Type III Sizing - Damage Soil If the soil has been damaged the structure will be damaged so cannot use Table IX

59 Type III Sizing - Damage Soil The default is to do a perc test If you get a perc number (less than 60 or 120 depending on system design), then size based on that number (however if perc rate is higher than what is expected of that soil, then it is a Type III).

60 Soil Texture = sandy loam Soil has been compacted, natural soil structure is gone Perc test is done, perc rate is 46 to 60 MPI (a normal perc rate for a clay loam). System = Type III

61 Type III Sizing - Damage Soil If you don t get a fast enough perc rate to be within Table IXa then: Use your best estimate Type IV system no clogging mat may help (system is now both a Type III and Type IV) Holding tank

62 High Strength Waste A Type III soil dispersal system can receive higher strength waste BOD > 170 mg/l CBOD > 125 mg/l TSS > 60 mg/l O & G > 25 mg/l

63 High Strength Waste These systems are now termed atrisk systems Can make modifications to Type I design to make the waste strength loading to the soil the same as Type I.

64 Contour Loading Rate A Type III system can exceed a CLR of 12 and exceed other recommend CLR

65 Operating Permit It is suggested that Type III and Type at-risk systems should be under an operating permit to periodically check for hydraulic performance.

66 Questions