20210714FLS to Staff 18.pdf

Rates & Regulatory Affairs
FLS-W-21-01
Falls Water Company Application for Approval of Three Capital Projects
Data Request Response

Request No.: FLS-W-21-01 IPUC DR 18

REQUEST NO. 18: Please provide the modeling results for each scenario (i.e. low flow
condition, peak hour condition, and maximum day plus fire flow condition) of the “future
water system” considered in Section 3.4 Hydraulic Model Analysis of the 2019 Drinking
Water Capital Facilities Plan. Please include the following information for each scenario:

a. A distribution system graphical representation showing the primary components (i.e.
pumps, wells, storage, pipe network, and users);
b. Primary component parameters (elevation, size, horsepower, operating curve);
c. Piping segment materials, lengths, and diameters;
d. Piping nodal elevations; and
e. Operating scenario parameters

i. Nodal pressures
ii. Piping segment flows
iii. Pump operating parameters
iv. Well static water level
v. Storage tank level.

Response:
The response to Request No. 18 was prepared by Ryan Christensen of S&A
Engineering. He conducted the hydraulic modeling for the 2019 Falls Water Company
Drinking Water Capital Facilities Plan.
There is no model to provide data for this request in a similar manner to that done for
Request No. 17. The future system initially discussed in section 3.4 would essentially be
the existing model, without improvements, but with future demands added. The
projected peak hour flow under future conditions is about 19,700 gpm. Without any
improvements, the model will not produce useful results with a demand of that
magnitude. For that reason, no intermediate model was saved for that step. The general
process in addressing future needs was to start with the existing model, add the future
demands, and then add projects addressing deficiencies. Source deficiencies were
addressed first, followed by pipeline capacity and other deficiencies. A general rule in
FLS-W-21-01 IPUC DR 18
NWN Response
Page 2 of 2

addressing pipeline deficiencies was to keep flow velocities to a maximum of about 5
fps. The results of this iterative approach were the future models associated with
Requests No. 19 and No. 20.