Rural septic systems move on to the public radar

Pressures Increased rural subdivision is increasing attention 
on the need for systems that protect the environment

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Over the years that Alberta farmers and ranchers have been completing Environmental Farm Plans (EFPs), farm waste management has consistently ranked among the top five environmental challenges concerns identified by producers.

“We know that many municipalities across the province are facing pressures to better manage water quality,” says Alberta Environmental Farm Plan program co-ordinator, Perry Phillips. “They are dealing with issues such as grandfathering of older, substandard septic systems, application of sewage sludge to agricultural lands, as well as separation distances, particularly with regards to subdivision of farmsteads from the rest of the farmland. There are a range of concerns from esthetics to human health and groundwater protection.”

Those two situations hold a message for rural areas in the years ahead, he says. Expect more pressure on rural septic systems.

Developing an EFP for a farm or ranch is an excellent way to assess risks to human health and groundwater associated with on-site sewage treatment systems, says Phillips. But producers will also want to know their responsibilities in developing new or revamping existing systems with regards to standards of practice, permits and regulations.

Farm workhorse

It is always amazing to consider how much work a farm septic system does. Alberta Municipal Affairs estimates the average person produces 340 litres of waste water that flows through a sewage treatment system every day. A family in a three-bedroom house, using the basic code design calculation of 1.5 persons per bedroom, produces 1,530 litres per day or half a million litres per year.

Most landowners want to develop an effective, properly designed system, says Joe Petryk, senior field inspector for Alberta Municipal Affairs, who is a specialist in the septic area.

In Alberta, standards for the design, installation and material requirements of on-site private sewage systems are provided by the Private Sewage Systems Standard of Practice under the Safety Codes Act. However, standards are just part of the picture. Ultimately, a septic system must meet the needs of the people living on the farm.

For this reason, knowledge of the property and your family’s lifestyle is key, says Petryk.

“Any given septic system is as unique as the property it serves. Site gradients, the number of people living on the property, water usage/conservation and soil characteristics are just some of the factors that must be considered when deciding the kind of septic system to install.”

Pressure versus gravity

Pressure-fed and gravity-fed systems are the two common choices when it comes to septic system discharge, with pressure fed generally preferred.

In a gravity-fed system, sewage flows out of the tank or is pumped from the tank into a lower-elevation treatment field, taking the effluent underground where it is absorbed by the infiltration area within the subsurface field. A gravity system can also be applied to an open-discharge system (surface discharge).

“Pressure-fed systems use a pump set in the effluent chamber that forces the effluent into the treatment field or treatment mound, distributing it evenly throughout the field. We generally recommend pressure-fed systems because of this,” says Petryk.

Septic tank size

An estimate of the septic tank size can be calculated using a simple formula, says Petryk. “In single-family dwellings, the average volume of sewage per day is estimated at 340 litres per person. To get a general idea of the size of tank required, multiply the number of bedrooms by the number of prescribed people in the code per bedroom and then multiply the result by 340. For example, two persons in a two-bedroom home would be “two multiplied by two multiplied by 340” to equal the number of litres required. The Standard of Practice should be referenced for any additional design requirements.”

Site evaluation key

Making the right decision on a treatment system depends to a large degree on soil characteristics of the site. The Standard of Practice requires a site evaluation to be conducted. Part of the evaluation requires test pits to be dug to produce a soil profile. A soil sample of the most limiting condition within the proposed treatment zone is collected and sent to a laboratory for analysis to determine the texture of the soil. The soil texture classification is now the approved method to determine the effluent soil loading rates for the treatment system design.

A soils percolation rate test is no longer acceptable to determine the soils capacity to take on effluent and will only be used in support of a design that is based on a soil profile investigation.

More detailed information on rural septic systems is available in a feature article with Joe Petryk, Build an effective farm septic system, available on the Alberta Environmental Farm Plan website

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