The public health risk from unapproved septic systems arises from a number of key risk factors. Adequate treatment of wastewater is dependent on the soil, type of treatment system, and characteristics of the wastewater.

An example of a high-risk area in Boulder County is the Eldorado Springs town site. Eldorado Springs presents all of the following risk factors in the densely clustered town site. Many unapproved and old septic systems are located on lots with steep slopes and poor, if any, available soil. In addition to the Eldorado Springs example, there are other communities that pose a similar risk because of their dense clusters of unapproved and aging septic systems that are in close proximity to shallow drinking water wells and surface water.

The key risk factors identified by Boulder County Public Health (BCPH) were:

1) Unapproved Systems (PDF 134 KB)

Unapproved septic systems have not been reviewed by public health professionals; therefore, there is no guarantee that they are constructed to current standards, and thus, they may be more likely to have negative water quality impacts.

2) Density of Systems (PDF 134 KB)

Pollution from septic systems in urban or semi-urban watersheds have been identified by local, state, and federal agencies as an area of concern. Few current management tools are applied to them, potentially compounding their risk.

3) Age of Systems (PDF 151 KB)

Age is an important factor to consider when dealing with an onsite wastewater system (OWS), or septic system. There are two factors when dealing with age: 1) Every system has a limited life; and 2) The older the system, the more likely that it does not meet adequate wastewater treatment standards.

4) Distance to Groundwater (PDF 143 KB)

When a septic system is not provided with enough filtering soil between the bottom of the system and groundwater, the groundwater can be negatively affected.

5) Drinking Water (PDF 54 KB)

Domestic wells and private drinking water sources can become contaminated by septic systems.

6) Soil (PDF 53 KB)

Generally, septic systems are best used on large, relatively level, well-drained lots with deep, moderately permeable soil.

7) Slope (PDF 48 KB)

The steeper the slope, the greater the risk of septic system failure.

8) Distance to Surface Water (PDF 53 KB)

The greater the distance between surface water (i.e., creeks, streams, rivers, and lakes) and a septic system, the smaller the chance of surface water contamination.

If you own and operate a septic system, you can help to protect our water by properly maintaining an approved system. Check your system today at: www.SepticSmart.org/check.

 Glossary | Return to Home