20210714FLS to Staff 23.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 23

REQUEST NO. 23: Regarding transitioning the Falls Water system into a two-pressure
zone system:

a. Please provide the analysis and justification for a two-pressure zone system.

b. Please explain why the 2019 Drinking Water Capital Facilities Plan does not address
transitioning the Falls Water system into a two-pressure zone system.

Response:
The response to Request No. 23 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. The materials referenced in the reply below are
found in FLS-W-21-01 IPUC DR 23 Attachment 1 (Exhibit 12).
a. Figure 8 from the 2019 capital facilities plan has been included for reference. On
Figure 8 the 4,800-foot contour line is called out. Falls Water Company can
provide water to customers up to the 4,800-countour without the need for a
second pressure zone. Above elevation it is recommended that a second zone
be considered.

b. The green shaded areas in Figure 8 show where development was projected to
occur when preparing the future system analysis. Aside from a small sliver in the
top center of the map, all the green shaded areas are at a low enough elevation
that a second pressure zone would not be needed. Moreover, the 4,800-foot
contour is not intended as a hard rule, but rather a trigger indicating that
additional care is needed to ensure homes around that elevation that are served
by the existing pressure zone will have adequate pressure. Since it was not
projected that development would occur above 4,800 feet no detailed analysis
was included for adding a higher-pressure zone.

IPUC DR 23
ATTACHMENT 1
FALLS WATER CO., INC.

Hydraulic Modeling Data

(1 PAGE)

FALLS WATER COMPANY
PROJECTED GROWTH
FIGURE 8
Falls Water Company
20-Year Planning Area
Ammon
Idaho Falls
Iona
IBSD-IF Agreement Boundary
20-Year Growth Areas (EDUs)
10-foot Elevation Contour
(4,800-foot Contour Bolded)
Planned Future Boundary
Ammon
Idaho Falls
Legend
U.S. Hwy 26
N
25th East
ID Hwy 43
Ammon Rd
1st St
15th East
Crowley Rd
Lincoln Rd
Iona Rd
49th North