New option for fewer laterals on some sloped-top at-grades

With the latest release of Sewers (2021.06.21) we have added a preference that may allow you to use fewer laterals for some widths of sloped-top at-grades.

In previous versions of Sewers the distance between the most downslope lateral and the edge of the downslope aggregate was set at 6 feet. 6 feet is the minimum distance allowed by the DEP Alternate Guidance document “At-Grade Absorption Area” at paragraph II.C.5.a.iii. The document does not specify a maximum, so it appears some unspecified designer discretion is allowed. We have added a preference that allows you, the designer, to set that maximum at 6, 7, or 8 feet. The preference is set to 6 feet by default, so if you do not want to use this new feature you do not have to do anything.

If you change the setting to 7 ft, a 14 ft wide system will now be designed with 2 laterals instead of 3; a 20 ft wide system will have 3 laterals instead of 4.

If you change the setting to 8 ft, a 14 or 15 ft wide system will now be designed with 2 laterals instead of 3; a 20 or 21 ft wide system will have 3 laterals instead of 4.

If you leave the preference alone (6 ft), sloped-top at-grades will be designed as they always have been.

The new preference is on the “Overrides” tab of the Preferences Editor.