1. U.S Environmental Protection Agency
Onsite Wastewater Treatment Systems Manual: A Performance Based Approach for Designing and Managing Onsite Wastewater Systems
U.S Environmental Protection Agency

2. In the beginning
And thou shalt have a Paddle upon thy Weapon, and it shall be:
When thou wilt ease thyself abroad, Thou shalt dig therewith,
and shalt Turn Back and Cover that which Cometh from Thee
Deuteronomy 23:13

3. Where we’ve been . . .

4. 2002 USEPA Onsite Manual Complements the 1980 Design Manual
Promotes the use of design performance requirements
Advocates perpetual management of all systems
Focuses on risk-
based assessments
Available on the
Internet and CD

5. How to access the OWTS Manual
CDs are available at
The online version is available at:
To order a printed version, send a request to:
U.S. EPA/NSCEP P.O. Box Cincinnati, Ohio
Send an to
or call or (513)

6. Summary of manual contents
Background and use of OWTSs
Management of onsite systems
System performance requirements
Treatment processes and technologies
Treatment system selection

7. Note:
The Onsite Wastewater Treatment Systems Manual is not intended to determine appropriate or inappropriate uses of land.
The manual presents information that can be used to select appropriate technologies and management strategies to minimize risks to human health and water resources in areas not connected to centralized sewage systems.

8. Background and use of OWTSs

9. Current shortcomings Lack of clear performance requirements
Few O&M or management programs
Watershed/regional impacts often ignored
Poor public outreach and education
Little coordination with planning, zoning, water resource, and other agencies and stakeholders

10. Reasons for concern
Public health
Water quality
Property values
Community quality-of-life

11. OWTS pollutants of concern

12. Nutrients and bacteria from a variety of sources are primary pollutants in the U.S.
Onsite systems are a source of nutrients and bacteria

13. Onsite system malfunction rates
U.S. Census Bureau Reports %
National Small Flows Clearinghouse 10%
Nelson, Dix, Shepard Survey up to 70% ???
Best professional judgement;
failure definitions varied
A significant number of community water systems list onsite systems as a potential contaminant source for drinking water supplies . . .

14. Buttermilk Bay Assessment

15. Increasing demand for groundwater
POPULATION GROWTH
100% increase in public water withdrawals ( )
Food production needs
URBAN SPRAWL
Concentrates demand
Leads to reductions in ground water recharge
ECOSYSTEM MAINTENANCE
Water supplies are needed to maintain sensitive ecosystems and/or endangered species (e.g., Pacific NW, FL)
1. Agriculture (irrigation) represents the single largest
source of demand for water; more than half the total
ground water withdrawn annually.

16. Elevated nitrate concentrations in groundwater in Kent County, MI
Nitrogen sources include agriculture and lawn fertilizers, atmospheric deposition, onsite systems
Source: Kent County Health Dept.

17. Source Water Assessment & Protection Program
(168,000 PWSs Must Have Complete Assessments By 2003)
2,156 (98%)
4,211
(96%)
1,347 (95%)
2,103
(98%)
2,023
(97%)
550
(96%)
8,352
(98%)
2,645
(96%)
1,628 (85%)
11,724
(99%)
10,630
(97%)
2,080
(98%)
718
(96%)
12,350
(98%)
479 (94%)
736
(97%)
10,389
(97%)
3,705 (98%)
1,932
(94%)
4,279 (95%)
1,329
(97%)
5,939
(95%)
675
(95%)
4,837
(96%)
5,801
(93%)
551 (97%)
953
(91%)
1,414
(94%)
2,101
(95%)
3,776
(96%)
3,815 (98%)
8,146
(91%)
1,079
(93%)
2,701
(94%)
712 (67%)
7,511
(97%)
1,173 (79%)
1,732
(93%)
1,527
(90%)
1,274
(95%)
1,199
(89%)
1,687
(94%)
1,645
(98%)
1,485
(88%)
702
(63%)
2,572
(92%)
Puerto Rico
490 (74%)
1,820
(87%)
6,865
(89%)
Required assessments in 50 States, Puerto Rico and D.C. are now underway.
Goal is to achieve all assessments finished for 168,000 systems in 2003.
That is daunting task. Only 9 states are 20% or more of the way there by 9/30/01, but all are currently scheduled to get there in 2003.
Regions are reviewing how these assessments are progressing and how they are leading to local prevention efforts.
Prevention is progressing in the states for some systems, particularly the larger public water systems, whether using ground water or surface water, because of their greater resources for watershed and wellhead protection activities.
141
(74%)
6,607
(94%)
1996 SDWA
Source Water Assessments
Source Water Protection
2003
1. Delineate Source Water area
5. Establish local SW protection risk
management measures
2. Contamination source inventory
6. Develop Contingency Plans
3. Susceptibility Determinations
4. Public distribution & discussion of findings

18. Management of onsite systems
Chapter 2 of the OWTS manual deals with system management
The USEPA Office of Water has developed guidelines and a handbook for managing onsite and clustered systems

19. Management: traditional management focus . . . .
Permitting: prescribed limits on acceptable sites; prescribed system designs
Installation: oversight of construction and installers and/or licensing, registration
O & M: homeowner booklets and brochures, tank pumping info
Corrective actions: repair or replacement upon receipt of verified complaints

20. Performance-based management focus:
Performance requirements based on relative risk to valued surface and ground water resources
Management of all systems based on technology and risk assessments
Simple systems installed at low densities farther away from valued resources = lower management intensity
Complex systems or those installed at high densities near valued resources = managed more intensively

21. Performance-based management elements
Cooperative watershed planning: specifying the necessary water quality to permit a specific use at a specific location downstream of the onsite treatment systems
Performance-based design: requiring specific treatment levels
Operation: renewable system permits, periodic inspections
Maintenance: requiring tank pumping at regular intervals, maintenance contracts
Corrective actions: replacement requires new performance-based designs

22. What constitutes a performance-based approach?
Siting and design:
Designing a system that meets performance requirements based on site conditions
rather than requiring the site to meet prescriptive criteria (lot size, soil permeability, depth to groundwater, etc.) needed for the approved system type
System management:
Management programs that provide perpetual system oversight
to protect public health, water resources, property values

23. Overview of performance-based approach
Wastewater characterization
Site evaluation
Design boundary identification & characterization
Regulatory requirements for system performance

24. Residential wastewater sources/flows

25. Residential wastewater characterization: flow and strength analyses
Estimate:
average daily flows (or use meter info)
hourly and instantaneous peak flows
wastewater strength (composition) using similar-facility comparisons or sampling info

26. Wastewater strength can vary considerably

27. Assessing site conditions
Preliminary review
Soil surveys, aerial photos, geology, slopes
Info from adjacent systems, installers
Reconnaissance survey
Landscape position, vegetation, buildings, drainage, topography
Identification of prospective sites

28. Assessing site conditions
Consider broader planning needs
Clustering of systems can improve performance, lower capital & O/M costs
Detailed evaluation
Soil profile analyses via backhoe pit
Characterize subsurface wastewater flow path
Groundwater assessment (redox, wells, maps, etc.)

29. Identify design boundaries
... places where conditions change abruptly… in subsurface infiltration systems, the soil is part of the treatment system.
Infiltrative surface (biomat location)
Restrictive horizons; perched
water tables
Surface of saturated zone (groundwater)
Point at which performance must meet water quality goals (SW/GW discharge, point of re-use, spray irrigation, etc. as required by regs)

30. Common design boundaries

31. Close-up of trench system design boundaries

32. Identify desired performance requirements of regulatory agencies
Assess cumulative ecosystem impacts
TMDLs, 303(d) lists
Source water protection (MCLs)
Watershed restoration action strategies
Anti-degradation requirements

33. Identify desired performance requirements (cont.)
Protection of public health
No surfacing or well pollution
Protection of water resources
Groundwater (pathogens, nitrate)
Surface waters (pathogens, nutrients)
Meet overall water quality standards
Consider existing/planned system requirements and impacts
System densities, critical areas
Water resource sensitivities

34. Consider source water protection areas when establishing performance requirements
Ground Water
Surface Water
1. Source Water Protection includes prevention efforts for
both ground waters and surface waters.
2. Source Water Assessments are delineating current
sources of drinking water for all public water wells and
surface water intakes in the country.
3. While these areas are clearly the highest priority
geographic areas for protecting drinking waters
currently used for public water, OW is also concerned
about waters used by private water users, and with all
potential drinking waters regardless of when they will
become current sources.

35. Performance requirements should also consider watershed-scale impacts

36. Assess design boundary loadings
Loadings to treatment system components
controls sizing, technology selection
Loadings to the infiltrative surface
controls size of infiltration system
Loadings to restrictive horizons
controls vertical placement of SWIS
Loadings to groundwater
controls vertical placement, may limit type

37. Lateral view of an effluent plume showing its movement through the soil toward design boundaries

38. Typical treatment train components
Septic tank(s)
Single or multiple compartments
Watertight; sized for peak flows
Equipped with effluent screen to protect SWIS
Subsurface wastewater distribution
Trenches filled with gravel
Gravelless trenches (chambers)
Pressure-dosed systems
Alternative systems

39. Treatment train components (cont.)
Alternative systems
Mounds, at-grades, intermittent or recirculating filters
Aerobic units
Vegetated submerged beds

40. Chapter 4 topics: processes & technologies
Conventional OWTSs
Soil based treatment and distribution systems
Use of alternative and advanced pretreatment systems
Fact sheets for classes of alternative treatment systems and special issues

41. Treatment processes: components of a conventional soil-based system

42. Desirable SWIS characteristics
Width: < 3 ft. wide
Length: Must meet contour load limits
Orientation: Along landscape contours
Vert. Placement: High in soil profile; 2 ft GW/BR
Dosing: Uniform over infiltrative surface
Landscape pos: Ridge lines, hilltop, shoulder slopes
Drainage: Moderate- to well-drained site

43. Loadings

44. How well does soil treatment work?
Very well IF the topography, soil types, and groundwater levels meet requirements.

45. Dispersal system options: drip irrigation
Drip lines high in the soil profile enhance treatment
Can be used on sloping sites with trees, etc.
Source: University of Minnesota Extension

46. Other Chapter 4 topics Aerobic treatment units (ATUs)
Media filters (ISFs and RSFs)
Fact sheets for about a dozen families/classes of available treatment units

47. Chapter 5: Treatment system selection
New system design approach
Rehabilitation of failed onsite system

48. Failure analysis: types of failure and effects

49. Failure analysis: onsite wastewater failure diagnosis and correction procedure

50. Failure analysis: onsite wastewater failure diagnosis and correction procedure (cont.)

52. Onsite manual relationship to clustered treatment systems
Systems with capacity to serve 20 or more people per day defined as Class V Injection Wells under US EPA’s Underground Injection Control (UIC) Program
Registration and groundwater protection
States may have more stringent requirements
Site evaluation issues
Design issues
Management issues

53. Cluster site evaluation
Evaluation of ground water mounding potential
Additional contour loading and performance boundary analysis
Additional downstream flow and plume analysis

54. Cluster system design
Multiple fields (totaling ~ 200% sizing) rotated into/out of service
Greater need for uniform distribution (pressure or drip)
Monitoring well requirements

55. Cluster system management
Responsible management entity generally required
Proactive inspection and monitoring program required
Additional involvement in planning and oversight of residuals management, land use planning, and O & M programs

57. Status of EPA Alternative Sewers Manual
EPA supplies are presently exhausted for hard copy distribution
Manual can be viewed on web at by browsing publications and typing in 625/1-91/024

58. Cluster systems planning handbook is posted at http://www. ndwrcdp