Which Junction Loss Methodology Do We Use?

Roger Kilgore, P.E.
Kilgore Consulting and Management
2963 Ash Street
Denver, Colorado 80207
(303) 333-1408
RKilgore@KCMwater.com
And
Joseph S. Krolak
Federal Highway Administration

There are many approaches to estimating energy losses in storm drain junctions and manholes. Within the FHWA there are at least two different approaches documented in current publications. HYDRAIN (version 6), and its documentation, uses the methods developed in the research report "Energy Losses through Junction Manholes" (FHWA-RD-94-080, November 1994) while HEC-22 uses a methodology of unknown origin. The author is also formulating another approach that classifies junctions and their hydraulic conditions in a manner analogous to inlet and outlet control analyses of culverts and applies equations in appropriate forms for the given classification. One hypothesis for this new approach is that a flaw in most of the existing methods is that they attempt to develop a single equation form for very different hydraulic conditions resulting in problematic results in some situations.

The paper would report on progress of the following activities:

1. Application of the HEC-22 and research report methodologies to selected existing FHWA laboratory data to compare their predictions of hydraulic grade lines in the incoming pipes.

2. Discussion of HYDRA junction loss approach.

3. Presentation of the author's classification approach.

The overall objective of the paper is to stress the need for, and make progress toward, a unified, technically-based method for estimating junction energy losses.