Field comparison of rock-filled and chambered trench systems

A field evaluation was conducted in Minnesota to identify whether there is a statistical difference in performance between chambered and rock-filled trench systems. This was achieved by a large-scale survey of over 100 selected onsite systems of both rock-filled and chambered trenches. Each system type was studied within three major soil permeability categories (fast, medium, and slow) and the percentage of the system in use at the time of the site visit was determined. Adjusting both types of systems to a standard size datum, the ponding levels were compared. Nearly 60% of the systems visited during the study of ages 5-10 years did not have any ponding observed at the end of the first trench segment. When the amount of ponding was compared between rock-filled and chambered systems, the data did not prove the hypothesis that chambered systems of a similar age as rock-filled systems utilize 25% less area than rock systems at 10% significance level.