Private Sewage Systems Standard of Practice Proposed Revisions

Transcription

1 Private Sewage Systems Standard of Practice Proposed Revisions The Government of Alberta is currently reviewing the Standard of Practice (SOP) for Private Sewage Systems. To this end, the Alberta government proposed a series of revisions to the Standard and asked for public input. The proposed changes are designed to ensure the effective treatment of wastewater while providing sustainable solutions for the increasing amount of rural development in the province. They can be found at The revisions will address the introduction of new technologies used in private sewage systems and advances in the science applied to the design of these onsite wastewater treatment systems. The AAMDC Standing Issues Committee on Infrastructure, Resources and the Environment discussed the changes and provided a series of recommendations that were subsequently approved by the AAMDC Board to form the official Association position. The committee reviewed the document and made the following comments: The AAMDC is in favour of point 6 on the key changes summary relating to removing the minimum property size of ½ acre. The Association feels that the soil and land characteristics are a much more valid factor in determining if a property can support a private sewage system than is property size. The AAMDC is not in favour of point 7 on the key changes summary and believes that the municipality must provide permission to allow the use of a holding tank. A municipality will consider a number of factors outside the SOP in allowing a holding tank, which contributes to the well-being of the entire municipality and allows the local government to work private sewage infrastructure into its municipal plans. The AAMDC would like further clarification on point 34 of the key changes summary related to restrictions on the use of Open Discharge Systems. In particular, the Association would like to know if this rule will apply to the rebuilding of existing pits, whether this rule will apply equally to residential and commercial properties, and what is the scientific justification for the 30-acre distinction. There is some concern that 30 acres is too high a number and that this restriction is excessive. Point 35 of the key changes summary referring to lagoon sizing led the AAMDC to question how overflow situations will be addressed. Enquiries may be directed to: Andre Tremblay, AAMDC Director of Advocacy, Policy and Communications (780) Attachment Karissa Potiuk, AAMDC Policy Analyst (780) Mark Oberg, AAMDC Director District 3 (780)

2 Summary of Key Revisions Proposed for the Alberta Private Sewage Systems Standard of Practice Why revisions are needed: Revisions to the Private Sewage Systems Standard of Practice 1999 are required to address new technologies industry has brought forward for use in private sewage systems, and advances in the science applied to the design of these onsite wastewater treatment systems. The proposed changes will help ensure these onsite wastewater treatment systems effectively treat wastewater and provide sustainable solutions for the increasing amount of rural development in Alberta. This summary has been developed for the purpose of stakeholder consultation. The proposed revisions reflect comments and recommendations for changes received since the Standard was published in The Private Sewage Task Group that provides advice to the Safety Codes Plumbing Technical Council has met 4 times over the past 2 years to review revisions and provide advice on developing this revised draft Standard. This summary reflects the March 1, 2007 draft of the revised Private Sewage Systems Standard of Practice. This summary is not a complete listing of the changes in the Standard of Practice. The summary identifies changes thought to be substantial or that have been identified as needing more stakeholder input. Stakeholders are encouraged to obtain and review the complete draft of the Standard of Practice. Key Changes Summary 1. Maximum daily wastewater volume or on-property restrictions to which the Standard applies are no longer included in the Standard of Practice. These limits are set by the regulation adopting the Standard and should not be repeated in the Standard. It is not expected the limits set out in the current Safety Codes Act Regulation will change. Removing this from the scope of the Standard accommodates the possibilities of Alberta Environment using the standard for large volume systems or where property lines may be crossed. Currently the Safety Codes Act Regulation adopting the Standard of Practice limits its application to a development where peak daily wastewater volumes are less than 25 cubic meters per day and where the system is contained wholly on the property it serves. 2. The Standard of Practice has been substantially reorganized. Stakeholders asked that it be reorganized for the purpose of easier navigation. There have been substantial changes made to some

3 sections and new sections added. Article headings will assist the user in locating requirements. 3. The new draft Standard focuses more on objectives and design requirements. However, the standard still includes prescriptive requirements which must be followed unless it is demonstrated that the design and installation will achieve the objectives and design requirements have been met. 4. Definitions, thresholds and requirements have been harmonized with Alberta Environment s and Alberta Health s regulations and standards. 5. A high water level alarm is required for all systems. This includes holding tanks. The alarm is needed to warn the occupant of system problems and an imminent backup of sewage into their home or building. See Articles and Removing a provision that relates to the minimum property size of ½ acre is being considered. Considerations to removing this requirement include: Municipalities often set larger minimum parcel sizes when private sewage is used. The parcel size does not have a direct technical impact on the suitability of a system. In fact in many cases the lot must be larger than ½ acre. This is often the case when development density increases. Developments vary in size and the amount of wastewater generated which are key factors in deciding if a property can support a private sewage system. The standard still includes a requirement that the land and area available must be suitable for using a private Sewage Treatment System. 7. Removing provisions that a municipality must provide permission to allow the use of a holding tank is being considered. This is an administrative provision that relates to the impact on a municipalities infrastructure of roads and wastewater treatment facilities when holding tanks are used for private sewage systems. It may not be appropriate in a technical standard such as this. Feedback from municipalities is needed on this issue. 8. The Standard requires additional system controls for systems serving developments that generate more than 5 m 3

4 (1,100 gal) per day and on all systems that are designed to treat the effluent to a secondary standard before application to the soil infiltration surface. Control systems must manage the operation, and record the information regarding operation. These requirements have been set out to enable the effective ongoing operation and evaluation of system effectiveness. For large volume systems control systems, monitoring ports and groundwater wells are required. Monitoring wells enable confirmation that required vertical separations are maintained during operation and enable esting of groundwater quality impact. See Section 2.4. Note: a 6 bedroom home would be assigned a peak flow of 675 gal per day. It is far less than the value of 1,100 gal per day established for additional controls under this revision. 9. Required septic tank volume has increased significantly. The reason for the increase is to ensure the effluent quality does not decrease as sludge and scum (septage) accumulates in the tank over time. Effluent quality will improve. The period of time between a required pump out of septage will be extended. Longer periods between pump outs result in increasing rates of septage digestion in the tank. This will result in an overall decrease in the total amount of septage hauled to municipal facilities. The tank volumes proposed in this draft are based on current science and are consistent with many other jurisdictions. See Article An example of the increase in septic tank working volume for a for 4 bedroom home is shown below: Old standard = 600 gallon vs. Revised standard = 990 gallons. 10. An effluent filter must be provided for all systems. Whether primary or secondary treatment is achieved by the initial treatment components, an effluent filter must be provided. An effluent filter improves effluent quality from a septic tank and protects against poor quality effluent during brief periods of high flow rates. When secondary treatment is used, filters are needed to protect the pressure effluent distribution system. The standard requires filter selection be based on providing a 2 year period between servicing at the projected flow volume from the development. 11. Buried access to tanks is no longer acceptable. The access openings to tanks must be extended to the ground surface. This is an important change to facilitate servicing as well as ultimately locating the tank, especially in winter when emergency service may be required. Tanks with buried access are often forgotten about which minimizes servicing and results in great difficulty in locating the tank, especially when the property changes ownership. See for general, for holding tanks, for septic tanks, for effluent tanks, and for settling tanks.

5 12. Piping connections to tanks must be made with flexible connectors. Tanks shift after installation. Hard connections currently made by gluing the rigid piping to the cast-in tank connection will break causing leakage, or may result in a complete separation. A flexible connector will ensure that a water tight joint is maintained at the piping connection. Flexible connectors have been available for a number of years and are preferred by many designers and installers. See Shallow buried tanks must be insulated. Prescriptive requirements set out that a tank having less than 4 feet of earth cover must be insulated over the top of the tank and to a depth of 4 feet on the sides. The insulation must provide an R8 insulation value, which is equivalent to approximately 2 inches of expanded polystyrene. The access opening must also be insulated. 14. Pressure Distribution must be used for all systems receiving secondary treated effluent. The maximum orifice spacing is 2 feet in this case. This is needed to reduce localized overloading of effluent on the soil. This occurs because secondary treated effluent does not create a substantial biomat that restricts infiltration and causes the effluent to spread and equalized loading over the infiltration surface. Increased orifice spacing may be used if it can be demonstrated that the system will effectively spread the effluent so localized overloading does not occur. See and Pressure distribution must be used for all systems installed on coarse textured soils such as Sand and loamy Sand soils. The maximum orifice spacing is 2 feet on these soils. This minimizes localized overloading on the soil infiltration surface preventing saturated flow through the soil. Saturated flow causes insufficient retention time in the soil reducing effective treatment of the effluent. See A minimum flow velocity of 0.6 meters (2 feet) per second is required for all pressurized piping systems. This will minimize the build up of slime and organic matter in the piping that contributes to orifice plugging. A maximum flow rate of 1.5 meters (5 feet) per second has also been established. This is reflected in the piping pressure loss tables in the appendix. See (1)(b) and (c). 17. The maximum length of a pressure effluent distribution lateral is 20m (65 feet) as set out by the prescriptive requirements in the Standard. Objectives and design requirements will allow longer lengths if it can be demonstrated that the volume of effluent applied per orifice per dose does not vary by more than 15% over the entire

6 system. Consideration of the time difference between the start of discharge and end of discharge between orifices must be considered. See The orifices in pressure distribution laterals must be located a minimum of 50mm (2 ) above the infiltrative surface. When not encased in gravel the distribution lateral piping must be supported at intervals not exceeding 1200mm (4 feet). This is required so that the potential of drain back into the laterals is minimized during periodic ponding of effluent on the infiltration surface. The distance above the infiltration surface should be maximized wherever possible. The supports ensure the piping maintains its grade for effective draining which prevents freezing of piping. See and An overall objective for pressure distribution lateral systems is set out in the revised Standard. That objective is to achieve a soil moisture content that does not change more than 20% over the infiltration area as measured at a depth of 75mm 125mm (3-5 inch) below the infiltration surface. See The end of all pressure distribution laterals must be readily accessible from the ground surface. This is needed to accommodate checking the residual squirt height and for flushing or cleaning of the lines in a pressure distribution lateral system. An irrigation box access cover at the end of lines would provide adequate access and also protect the pipe from damage. See (1)(i) 21. Minimum site and soil evaluation requirements are now clearly set out in the Standard. A percolation test is no longer used to determine the required infiltration area. Soil structure and texture are used to determine effluent loading rates. The new Standard explicitly requires a site evaluation that includes a minimum of 2 soil test pits to determine soil suitability and system design needs. The existing Standard implicitly required test pits or bore holes to determine depth to saturated soils based on soil colors and characteristics and to determine there is no limiting layer in the soil, although it was often not carried out. The new proposed Standard clarifies the site evaluation requirements. The soil profile must be described to the depth of the system design boundary and its characteristics used to confirm suitable vertical separations and determine effluent loading rates. See Part Plumbing fixtures that increase daily flow volume or result in high instantaneous flow must be considered and the daily peak flow for design adjusted accordingly. An example is the release of the water held in a large jetted tub which occurs over a very short period of

7 time. This rush of water can cause suspended particles to be washed through the septic tank or treatment plant. See The strength of wastewater must be considered and addressed by the design. This is a critical design requirement for systems. It must be considered for all types of development and the system design adjusted accordingly. It is not often that it will need to be applied to a residential development. An example of wastewater strength consideration required for a residence is when an in-sink garbage grinder is installed. See Groundwater mounding below a system must be estimated and accommodated in the system design. Thisisa particular concern for larger soil based treatment systems and is a design aspect that is not now considered in most designs. Groundwater mounding may result in insufficient vertical separation between the infiltration surface and saturated soils. This situation reduces treatment effectiveness. If the development generates less than 5m 3 per day and prescriptive linear loading limits are applied, groundwater mounding will not have to be modeled and estimated. See Effluent treatment objectives are set out in the proposed Standard. Objectives are set for key points along the treatment train, including in the soil below the onsite wastewater treatment system. 26. Additional levels of secondary treatment have been established. There are now 5 treatment levels defined for the effluent before it is applied to the soil for final treatment and return to the environment. The treatment levels align with NSF (National Sanitation Foundation) and BNQ (Bureau de Nominalisation du Québec) effluent standards for treatment plants. Using treatment plants that achieve a higher level of treatment allow locations that have seasonally saturated conditions at shallow depths to be served with a private sewage system by allowing reduced vertical separation distances. Treatment plants certified to the BNQ Standard or the NSF Standard are acceptable. See Part 4, 5, and The linear loading capacity of the soil must be considered. The linear loading rate considers the rate effluent can move horizontally through the soil. It must be considered where there are limiting soil layers below the systems soil infiltration surface. Treatment mounds are often used to address site that have tight soils or near surface saturated soil conditions. The consideration of linear loading limits will result in treatment mounds being longer. Designs that consider linear loading improve the success and sustainability of onsite wastewater treatment systems.

8 28. Effluent loading rates are reduced to 0.3 gallons/sq. foot (15L/m 2 ) on coarse textured soils such as Sands and Loamy Sands. Reduced loading rates are needed to ensure adequate retention time in coarse textured soils that have a low moisture holding capacity. It is consistent with an objective established in the Standard that requires an effluent travel time of 1-week to a depth of 1m (40 inch) of soil based on the mobile water content of the soil. See Table A. 29. Treatment Mounds - the effluent loading rate on the sand layer has been reduced to 0.8 gallons per sq. ft. (40L/m 2 ). This change is consistent with the effluent loading rate used in U.S. states when differences between the Imperial and U.S. gallon and differences in the projected flow from a development are considered. This change will extend the life of treatment mounds and reduce the occurrence of failures. See Provisions have been included that allow a reduced vertical separation between the infiltration surface and a limiting layer. Vertical separations can be reduced, if it can be shown in the design that the wastewater will come into contact with an equivalent volume of soil and that the effluent travel time to the vertical separation boundary equals or exceeds the minimum required travel time based on the mobile water content of the soil. Vertical separations may never be less than 600mm (2 ft.). Effluent loading rates will need to be reduced by an amount that corresponds to the reduction in separation distance. See Effluent loading rates must be reduced where the soil has a significant content of coarse fragments (gravel sized particles). Dispersal of effluent to sand, loamy coarse sand and coarse sand having more than 60% coarse fragments will not be permitted. As well, in these same soils if the coarse fragment content exceeds 35% the effluent loading rate must be reduced. 32. Modified treatment mounds that receive secondary treated effluent are included in the standard. This change will allow low profile mounds that require less sand and gravel. In many cases the sand and gravel is difficult to obtain or is very costly and owners often prefer the less obtrusive design the low profile mound presents. 33. Sub-surface drip dispersal / irrigation systems are included in the proposed standard. These systems can be used to realize a beneficial reuse of the effluent for irrigation. Restrictions are included to address winter operation concerns. See Section 8.5.

9 34. Further restrictions on the use of Open Discharge Systems have been established. The restrictions are related to the density of surrounding development. Clearance distances to property lines, water sources and buildings remains the same. However, an open discharge system is not allowed on a property of less than 30 acres if an adjacent property having a common property line is less than 30 acres in area. This still allows a parcel that is approximately 10 acres in area to have an open discharge when it is not bordered by a small parcel (something less than 30 acreas. It also allows an open discharge to be used on a large parcel (something exceeding 30 acres) even though it may have a common property line with a small parcel of land. There has been significant stakeholder feedback over the past years suggesting that limits should be placed on open discharge systems to ensure they are used only in areas of low density, not where there are a number of lots developed together. This is a proposed solution. The wording of the article is shown below. Article Open Discharge Prohibited 1) An open discharge shall not be installed on a property that is less than 30 acres in area, if an adjoining property having a common property line is also less than 30 acres in area. 35. Lagoon sizing is now based on average flow volumes rather than peak volumes. Due to the design and function of a lagoon it is more appropriate to size lagoons based on average volume. Using peak flow over 365 days incorporates too great a safety factor. See Article Privies (outhouses) are included in this standard. Privies were previously addressed in the building code. See Part 10.

10 COMMENT FORM 2007 Private Sewage Systems Standard of Practice Proposed Revisions Please provide comment on the following form or in a similar format. Article Number Key Change Item number Describe Concern: Proposed alternate wording of article or resolution to concern: Name, address, , phone number of person making submission: Submit to: Safety Codes Council Chief Inspector/ Administrator Private Sewage Systems Suite 800, Avenue Edmonton, Alberta T5J 3M1 Phone: Fax: privatesewage@safetycodes.ab.ca