Due Diligence

Infill Developments May Have Trickier Utility Connections?

Having been involved in numerous infill projects, I have noticed that the planning and engineering of utilities can tend to have a few more issues than your typical suburban tracts.  While the existing sewer or water lines may be adjacent to your property in the city streets, the connection to these utilities may have to deal with other existing infrastructure that is in the way.  During the tentative tract map or preliminary engineering design, these connection issues might get overlooked.  And as one seasoned land veteran once said, “the devil is in the details”.  Even though the design might be in this preliminary engineering phase, a good civil engineer will understand these potential issues that may come up during the final engineering design.  And as a developer, you will be better prepared for potential cost impacts.

As example, we were working on a 40-lot infill project and the existing sewer main was adjacent to the property.  However, a 96-inch storm drain line was in the connection path and posed a problem in maintaining gravity flow from the new sewer lines to be installed.  Our civil engineer’s initial suggestion was that we raise the grade of the site by approximately two feet and then the sewer line could flow over this large storm drain pipe and connect to the existing sewer main.  To raise the site, though, would have required some substantial dirt import at a significant cost.  We then looked at going under the 96-inch storm drain, but quickly realized we would be below the existing sewer main and would not be able to maintain gravity flow.  The eventual solution was to replace approximately 700 lineal feet of this existing sewer main with a new main that was maybe three feet lower and could accommodate the gravity flow from the new tract sewer lines.  At 700 lineal feet downstream, the grade eventually caught up with the existing sewer line and gravity prevailed.

While we did not like the cost of having to replace perfectly good existing sewer lines, this solution was maybe 10 – 15% the cost of importing dirt.   I have seen other similar situations where the actual final design has to deal with the existing infrastructure and therefore has cost impacts.  It has been my experience that homebuilders prefer to buy parcels with the final engineering completed so that all these details can be understood and costed out.  Again, “the devil is in the details”.

If you have any similar experience, comments, or questions, we welcome you to share with us below.