Engineering ReportENGINEERING REPORT
SILVERBROOK ESTATES
PRELIMINARY PLAT II
Phase 2a, 2b, 2c and 2d
PREPARED FOR;
93 Church LLC
December 29, 2008
Prepared By:
13 N. 23`d Street
Billings MT 59101
and
121 South Main Street
Livingston MT 59047
WWW.CTAGROUP.C]M
TABLE OF CONTENTS
CHAPTER 1— INTRODUCTION
1.1
OBJECTIVES OF THE ENGINEERING REPORT..........................................................
1-1
1.2
BACKGROUND AND SCOPE.........................................................................................
1-1
1.3
AREA DESCRIPTION.......................................................................................................
1-1
1.4
REPORT ORGANIZATION..............................................................................................
1-2
CHAPTER 2 — WASTEWATER
2.1
FUTURE WASTEWTAER FLOWS AND LOADS.........................................................
2-1
2.2
LAND USE AND LOAD SOURCES................................................................................
2-1
2.2.1 Population Projection..............................................................................................
2-1
2.2.2 Future Flow Projection...........................................................................................
2-2
2.3
LAND REQUIREMENTS...................................................................................................
2-3
2.4
CONSTRUCTION CONSIDERATIONS...........................................................................
2-3
2.4.1 Required and Provided Pipe Capacity....................................................................
2-4
2.5
WASTEWATER LIFT STATION.....................................................................................2-4
CHAPTER 3 — WATER
3.1
FUTURE WATER FLOWS..............................................................................................
3-1
3.2
LAND USE AND LOAD SOURCES................................................................................
3-1
3.2.1 Population Projection..............................................................................................
3-1
3.2.2 Future Flow Projection...........................................................................................
3-2
3.3
LAND REQUIREMENTS...................................................................................................
3-3
3.4
CONSTRUCTION CONSIDERATIONS...........................................................................
3-3
3.4.1 Required and Provided Pipe Capacity....................................................................
3-4
CHAPTER 4 — STORM WATER
4.1 STORMWATER SUMMARY........................................................................................... 4-1
4.2 METHODOLOGIES.......................................................................................................... 4-1
4.3 EXISTING CONDITIONS................................................................................................. 4-1
4.4 PROPOSED CONDITIONS............................................................................................... 4-2
APPENDICES
Appendix A Silverbrook Capacity Documents
LIST OF TABLES
Table 2-1: POPULATION PROJECTION................................................................................. 2-1
Table 2-2: PROJECTED INFLUENT WASTEWATER FLOWS ............................................. 2-2
Table 2-3: PROJECTED INFLUENT WASTEWATER FLOWS ............................................. 2-3
Table 2-4: DESIGN vs. PROVIDED FLOW............................................................................. 2-4
Table 3-1:
POPULATION PROJECTION.................................................................................
3-1
Table 3-2:
PROJECTED WATER DISTRIBUTION FLOWS ..................................................
3-2
Table 3-3:
PROJECTED WATER DISTRIBUTION FLOWS ..................................................
3-3
Table 4-1:
SUMMARY OF PRE -DEVELOPED RUNOFF ......................................................
4-2
Table 4-2:
SUMMARY OF POST -DEVELOPED RUNOFF ....................................................
4-2
Table 4-3:
SUMMARY OF POST DEVELOPED STORAGE REQUIREMENTS BASED
10-YEAR...................................................................................................................
4-3
LIST OF FIGURES
Figure 1-1: SILVERBROOK ESTATES Development Phasing Plan ...................................... 1-3
Figure 4-1: SILVERBROOK ESTATES Development Phasing Plan ...................................... 4-4
Figure 4-2: SILVERBROOK ESTATES Pre -Development Drainage Basins .......................... 4-5
Figure 4-3: SILVERBROOK ESTATES Post -Development Drainage Conditions .................. 4-6
CHAPTER 1
INTRODUCTION
This chapter introduces Silverbrook Estates Preliminary Plat II, with Phase 2a, 2b, 2c
and 2d. This chapter will also state the objectives of the report, the scope of work, the
planning area under consideration, and the report organization.
1.1 OBJECTIVES OF THE ENGINEERING REPORT
The objective of this Engineering Report is to provide the information necessary to
authorize an expansion of The City of Kalispell's water and wastewater systems by a
system extensions and connections to existing City water and wastewater systems.
1.2 BACKGROUND AND SCOPE
Off Site Improvements:
Silverbrook Estates is a multi phase development that was the impetus for a major utility
extension of water and wastewater systems north from the City's system at West
Reserve Drive along Highway 93. The water and wastewater extensions were
constructed in 2007 and 2008 and were engineered to serve a future population of
13,515. All engineering plans and the constructed improvements meet the City of
Kalispell standards and DEO requirements. The HWY 93 system extensions are
complete, conveyed to and operated by the City of Kalispell.
On -Site Improvements:
Silverbrook Estates Phase 1 and 1A have been plated through the Preliminary Plat
and infrastructure has been constructed. The final plat for Phase 1 has been filed and
Phase 1A Final Plat will be filed before the end of 2008.
All wastewater flows from Phase 2a and Phase 2b will be connected to the existing 12-
inch sewer line associated with Silverbrook Estates Phase 1 and Phase 1A as
constructed in 2007 and 2008. The 12-inch sewer line was designed approved and
construction with these wastewater flows and future off site wastewater flows
incorporated into the design.
All water distribution for Phase 2c and Phase 2d will be connected to the existing 14-
inch water line associated with Silverbrook Estates Phase 1 and Phase 1A as
constructed in 2007 and 2008. The 14-inch water line was designed approved and
construction with these water flows and future off site water flows incorporated into the
design.
Future On site Improvements:
This report addresses improvements for Preliminary Plat II and Phases 2a, 2b, 2c and
2d. All phases are part of Preliminary Plat II. Infrastructure improvement will include
water system extensions, waster water extensions, storm water systems streets,
sidewalks, rails, parks, open space and landscape amenities.
1-1
Silverbrook Estates Preliminary Plat II, Kalispell, Montana
2007 Engineering Report Chapter 1 — Introduction
1.3 AREA DESCRIPTION
The planning area for Preliminary Plat II was developed in concert with City staff and is
a portion of the Planned Unit Development (PUD) for Silverbrook Estates as approved
by the City of Kalispell. The Development Phasing Plan is located at the back of this
chapter. Preliminary Plat II consists of the following Phases as defined in the PUD.
Phase 2a
Commercial
Phase 2b
Town homes
Phase 2c
Residential
Phase 2d
Residential
1.4 REPORT ORGANIZATION
This report is organized into separate sections and sub -sections as summarized in the
Table of Contents. Figures and tables are numbered consecutively within each section.
Figures and tables are included within each section after the page in which they are first
referenced. A complete list of figures and tables appears at the end of the Table of
Contents.
The report also contains a number of appendices. The appendices provide
documentation to support the evaluation of the wastewater facilities such as
correspondence between the City and MDEQ.
The following Chapters will address wastewater, water, and storm drainage.
1-2
P"T
'A .s
LANDWORKS
Silverbrook Estates Preliminary Plat II, Kalispell, Montana
2008 Engineering Report Chapter 2 — Wastewater
CHAPTER 2
WASTEWATER
2.1 Future Wastewater Flows and Loads
This section summarizes the projected planning area characteristics, along with
projected population growth. This data is then used to project future wastewater flows
for the system extension.
2.2 Land Use and Load Sources
Preliminary Plat II with; Phase 2a - Commercial and Neighborhood Commercial,
Phase 2b - Town home, Phase 2c and 2d will be Suburban Residential.
2.2.1 Population Projection
Projections of future populations serve as a basis for the planning and design of
collection and treatment systems and for financial planning purposes. Several methods
may be used to project population growth. No method is exact and all have limited
reliability and must be tempered by knowledge of the area, its industry, employment
potential, economic conditions, trade area, and state of development. Extraordinary
events cannot be foreseen and, should they occur, will necessitate revision of plans.
Table 2-1 summarizes the Silverbrook Estates Preliminary Plat II area population
projections. The population projections were based on Kalispell planning department
criteria of 2.5 residents per dwelling unit.
TABLE 2-1
PRELIMINARY PLAT II - POPULATION PROJECTION
Population Projections
Property
Block
Description
Lots
Parking
Stalls
Pop /
Unit
Population
Notes
Phase 2a
Commercial
13
470
10
**
Phase 2b
Town homes
90
2.5
225
Phase 2c
Residential
85
2.5
213
Phase 2d
Residential
112
2.5
280
Total
300
728
Note: ** Population equivalent is estimated to approximate flow from DEQ 4.
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Silverbrook Estates Preliminary Plat II, Kalispell, Montana
2008 Engineering Report Chapter 2 — Wastewater
2.4.1 Required and Provided Pipe Capacity
Table 2-4 shows the required design flows and the flow capacity provided. 8-Inch
gravity sewer will provide adequate capacity for all phases of the development.
TABLE 2-4
DESIGN FLOW vs. PROVIDED FLOW
DESIGN NODES AND FLOW CHARACTERISTICS.
Flow
Node
Design
Floe-
Required
a xl)
Dia
D
in
Manning
n
Slope
ft/ft
Area
Sq ft
Pipe
Full
Floe,
Cap.
cfs
Pipe
Frill
Floii
Cap.
ni Td
Design
Floe-
Provided
g xl)
Pipe
Full
Floe
Cap.
T m
Velocity
at Full
Floe-
ft/sec
Phase 2a
3,995
8
0.012
0.0040
0.35
0.83
0.537
536,563
373
14
Phase 2b
101,639
8
0.012
0.0040
0.35
0.83
0.537
536,563
373
2.4
Phase 2c
90,312
8
0.012
0.0040
0.35
0.83
0.537
536,563
373
2.4
Phase 2d
203,806
8
0.012
0.0040
0.35
0.83
0.537
536,563
373
2.4
2c & 2d
294,118 1 8 0.012 0.0040 1 0.35 1 0.83 0.537 536,563 1 373 2.4
2.5 Wastewater Lift Station
A wastewater lift station (WVVLS) will be provided near the Southeast corner of Phase
2d and adjacent to Silverbrook Drive. The WVVLS will serve Phase 2c and Phase 2d.
An 8-inch force main was installed under the natural ravine on the west side of the
Silverbrook Drive Bridge during Phase 1 construction and is connected to the gravity
sewer in Phase 1. As such the Phase 1 WVVLS has been sized and constructed to take
these flows. This Phase 2c & 2d VVWLS will provide a connection to that force main.
Note that earlier in this chapter it was stated that Phase 2a and Phase 2b will flow into
the existing 12-inch gravity sewer that exists between Phase 2c and Phase 2a & 2b.
I110IK
2-4
Silverbrook Estates Preliminary Plat II, Kalispell, Montana
2008 Engineering Report Chapter 3 — Water
CHAPTER 3
WATER
3.1 Future Water Flows
This section summarizes the projected planning area characteristics, along with
projected population growth. This data is then used to project future water flows for the
system extension.
3.2 Land Use and Load Sources
Preliminary Plat II with; Phase 2a — Commercial and Neighborhood Commercial,
Phase 2b — Town home, Phase 2c and 2d will be Suburban Residential.
3.2.1 Population Projection
Projections of future populations serve as a basis for the planning and design of
treatment, storage and distribution systems and for financial planning purposes.
Several methods may be used to project population growth. No method is exact and all
have limited reliability and must be tempered by knowledge of the area, its industry,
employment potential, economic conditions, trade area, and state of development.
Extraordinary events cannot be foreseen and, should they occur, will necessitate
revision of plans.
Table 3-1 summarizes the Silverbrook Estates Preliminary Plat II area population
projections. The population projections were based on Kalispell planning department
criteria of 2.5 residents per dwelling unit.
era 3111114BINi
PRELIMINARY PLAT II — POPULATION PROJECTION
Population Projections
Property
Block
Description
Lots
Parking
Stalls
Pop /
Unit
Population
Notes
Phase 2a
Commercial
13
470
10
**
Phase 2b
Town homes
90
2.5
225
Phase 2c
Residential
85
2.5
213
Phase 2d
Residential
112
2.5
280
Total
300
728
Note: ** Population equivalent is estimated to approximate flow from DEQ 4.
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Silverbrook Estates Preliminary Plat II, Kalispell, Montana
2008 Engineering Report Chapter 3 — Water
3.4.1 Required and Provided Pipe Capacity
During the design of Phase 1, a model of the Kalispell water system was run to look at
peak flows and fire flows. It was determined that fire flows were met in the residential
areas with an 8 inch diameter water main network. The exact pipe sizes will need to be
determined in the commercial area depending on use
END
3-4
CHAPTER 4
STORMWATER
4.1 STORMWATER SUMMARY
This report analyzes stormwater drainage for the proposed Silverbrook Phase II
Preliminary Plat to be located in Kalispell, MT. Figure 1 at the end of this chapter
contains a Development Phasing Map of the area. Phase 1 and Phase 1A are currently
constructed under Preliminary Plat I, with the exception of Phase 1A Block 55. Block 55
of Phase 1A will be addressed as a portion of Phase 2D for the purposes of this
chapter. Phase 2A and Phase 2B drainage design was incorporated with Preliminary
Plat I.
4.2 METHODOLOGIES
Peak storm water run-off was calculated using the SCS Curve Number method as
described in the City of Kalispell Storm Water Facility Update Plan (SFUP), March 2008.
Peak runoff is determined for the 2-year, 10-year, and 100-year 6-hour storms. The
detention is determined based on the current City of Kalispell Design and Construction
Standards for the difference in the pre and post development volume for the 10-year 6-
hour storm with total precipitation of 1.2". StormNET software was used in determining
the calculations. The Storm Water Report will address the measures take to meet the
requirements of the Montana Pollution Discharge Elimination System (MPDES) MS4
Phase II Storm Water Management Plan for the City of Kalispell, as it applies to the site.
4.3 EXISTING CONDITIONS
Phase 2C and Phase 2D comprise 108 acres of the existing site that will be impacted by
development. Historical land use for both phases is agricultural. Based on the United
States Department of Agriculture, National Cooperative Soil Survey, the site consists of
one major soil classification. The soil is tally, blanchard, and flathead soils at 0% to 3%
slopes, and eroded, with a hydrologic rating of B. This soil accounts for approximately
85% of the site. The remaining soils on the site also have a hydrologic rating of B, and
can be described as a Kalispell loam, 0% to 3% slopes. Historical drainage patterns for
Phase 2C are southwest via overland flow and channelized flow through the south
portion of Phase 2D to the Stillwater River. Historical drainage patterns for Phase 2D
are southwest to the Stillwater River via overland flow and channelized flow.
Currently the site has been mass graded and reseeded to facilitate future construction
grades. This chapter will address the Pre -Development impacts based on the historical
land use and drainage patterns. See Table 4-1 for Pre -Development runoff rates for the
2, 10 and 100-year 6-hour events and runoff volumes for the 10-year 6-hour event. At
the end of this chapter, Figure 2— Pre -Development Conditions shows the existing site
and drainage conditions.
4-1
Silverbrook Estates Preliminary Plat II, Kalispell, Montana
2008 Enaineerina Report Chaater 4 — Stormwater
TABLE 4-1
SUMMARY OF PRE -DEVELOPED RUNOFF
Basin
2-year
10-year
100-year
Phase 2C Basin Runoff cfs
0
0.36
1.86
Phase 2C Basin Storage (cf)
0
2,810
22,350
Phase 2D Basin Runoff (cfs)
0
0.58
3.01
Phase 2D Basin Storage (cf)
0
4,622
36,739
4.4 PROPOSED CONDITIONS
Improvements impacting storm water runoff in the Phase 2C basin will include 23.8
acres of residential lots and 12.3 acres of roads. Road acreage includes impacts form
Church Drive to the north of both phases and Siverbrook Drive. Post development
flows will be southwest to a storage basin as shown in Figure 3, at the end of the
chapter.
Improvements impacting storm water runoff in the Phase 2D basin will include 34.9
acres of residential lots and 10.9 acres of roads. Road acreage includes impacts form
Church Drive to the north of both phases and Siverbrook Drive. Post development
flows will be southeast to a storage basin as shown in Figure 3.
See Table 4-2 for post development runoff rates for the 2, 10 and 100-year 6-hour
events and runoff volumes for the 10-year 6-hour event. Table 4-3 on the following
page shows the storage requirements based on the 10-year 6-hour storm. Bold items in
Table 4-2 and Table 4-3 represent design criteria for Post Development Storage
facilities as required by the City of Kalispell. Figure 3— Post -Development Conditions
shows the developed site and drainage conditions including designated storage basin.
TABLE 4-2
SUMMARY OF POST -DEVELOPED RUNOFF
Basin
2-year
10-year
100-year
Phase 2C Basin Runoff (cfs)
0.13
0.92
3.58
Phase 2C Basin Storage (cf)
759
10,908
42,647
Phase 2D Basin Runoff (cfs)
0.2
1.49
5.71
Phase 2D Basin Storage (cf)
1,248
17,910
70,014
:A
Silverbrook Estates Preliminary Plat II, Kalispell, Montana
2008 Engineering Report Chapter 4 — Stormwater
TABLE 4-3
SUMMARY OF POST -DEVELOPED STORAGE REQUIREMENTS
BASED ON 10-YEAR
Post -Developed
Area
(acres)
Pre -Developed
(cf)
Post -Developed
(cf)
Storage Required
(cf)
Phase 2C Basin
40.7
2,810
10,908
8,098
Phase 2D Basin
67.2
4,622
17,910
13,288
4-3
P"T
'A .s
LANDWORKS
-4
w
Phase IA
Block 55
Phase 2D
Pre Developed
Basin
93 and Church, LL C
C:T;�
Phase 2F
Pre Developed
0
0
Phase 2A
D
G
Phase 213
n
Silverbrook Estates
Pre Development Drainage Basins
for Preliminary Plat II
December 26, 2008
Kalispell, Montana
21111
E
Contour Interval : 5'
40
NORTH
0 250' 500' 1000'
OPEN
SPACE
0
Phase IA
Block 55
OPEr
Phase 2D
Alternative
Storage Basin
Impacts from Church Drive and
Silverbrook Drive are included
for both Phase 2C and Phase 2D
Phase 2D
Open Space
Outside of Developed Area
PHASE 2A
DRAINAGE ADDRESSED
IN PHASE 1 PLAT
PHASE 2B
DRAINAGE ADDRESSED
IN PHASE 1 PLAT
Phase 2C \_
Open Space
Outside of Developed Area
Phase 2C
Storage Basin
Phase 2D
Storage Basin
Silverbrook Estates
lik Post Development Drainage Conditions
for Preliminary Plat II NORTH
December 26, 2008
93 and Church, LL C Kalispell, Montana 0 250' 500' 1000'
APPENDIX A
Attached are documents, showing the process and approvals carried out to receive
wastewater system capacity approval for Silverbrook Estates. These approvals identify
capacity for Silverbrook in its entirety. In the Kalispell to DEQ, Health Department and
to CTA, letters and in paragraph 3, a commitment was made to Silverbrook for 378
gpm, which will handle all of Silverbrook wastewater flows as fully developed. This data
as enclosed shows a dedicated capacity to Silverbrook Estates.
Enclosed are:
1. DEQ Deviation application, August 8, 2007
2. Engineering Report Addendum #2 August 61" 2007
3. City to DEQ Facility Plan Approval, August 8, 2007
4. City to Engineer Facility Plan Approval, August 8, 2007
5. City to Health Department Facility Plan Approval, August 8, 2007
6. City to DEQ Engineering Plans and Specification Approval August 14, 2008
1-1
Montana repartment cW
ENVIRONMENTAL QUALITY
PUBLIC WATER SUPPLY DEVIATION REQUEST
Project Name: Highway 93 Water and Wastewater System- Extensions
EQ Number (if known):
Engineer Name: CTA
Circular.. � DEQ-1 Water Works = IF DEQ-3 Small Water Systems
X DE-2 Wastewater Facilities - DEQ-4 Subsurface Wastewater Treatment
STANDARD: Chapter 30 - Paragraph 32• Design Capacity and Construction.
EXISTING STANDARD:
"In general, sewer capacities should be designed for the estimated ultimate tributary
population, except in considering parts of the systems that can be readily increased in
capacity. Similarly, consideration should be given to the maximum anticipated capacity of institutions,
industrial parks, etc. Where future relief sewers are planned, economic analysis of alternatives should
accompany initial permit applications. See Sections 11.24 and 20.2."
PROPOSED STANDARD:
A new proposed standard is not being requested, but recognition of the City's plan to provide system
improvements and additional capacity prior to exceeding system capacity, by the City's preparation of
the Wastewater System Facility Plan and system improvement projects identified in the Facility Plan.
JUSTIFICATION: attach additional information as necessary
• Attached is an Addendum to the Municipal Utility Extension Engineering Report for the City
of Kalispell Highway 93 North submitted in January 2007. This addendum summarizes
capacities and anticipated flows through the City's collection system. With excerpt from the
City's Facility Plan being prepared.
• Attached are City of Kalispell System Capacity letters to DEQ, Flathead County Health
Department and CTA that addresses the City's sanitary sewer collection system and ability to
provided necessary capacity.
In accordance with ARM 17.38.101 (e), I certify that strict adherence to the above standard is not
necessary to protect public health and the quality of state waters.
G te2CY�
(Signature of Professional Engineer) (Dale Signed) 0; Mo&
Montana P.E. Number f�0�%4�c� ri pATWCKJ.
WHITE
14090PE
ADDENDUM NO.: 02
DATE: August 6, 2007
PROJECT: City of Kalispell, Highway 93 North
Municipal Utility Extension Engineering Report
ARCHITECT: CTA ARCHITECTS ENGINEERS
13 N. 23rd St
PO Box 1439
Billings, MT 59103-1439
CTA PROJECT REF.: 93CHURCH2 PER
Highway 93 Waster and Wastewater System Extensions
Enclosed herewith are the following documents and additional data, intended to supplement the
Municipal Utility Extension Engineering Report, dated January, 2007.
1. City of Kalispell Collection System Capacity Narrative
2. Table - 1 WASTE WATER FLOW GENERAGTION
3. Table - 2 KALISPELL HISTORICAL FLOW PER RESIDENTIAL LOT
4. Table - 3 WASTE WATER FLOW CAPACITY
5. HDR Chapter 5: Existing Sewer Collection System Excess Capacity*
6. HDR Figure 5-2 Sewer Collection and Conveyance System Analysis*
*Items S and 6 are provided with permission by HDR and are portions of the Draft
Facility Plan being completed for the City of Kalispell.
MAJ0BS\HWY93UTIL\TeresaTER Report Addendum-02.DOC AD2 -I
CITY OF KALISPELL 93CHURCH2
HIGHWAY 93 NORTH
KALISPELL, MT
City of Kalispell Collection System Capacity Narrative
The Montana Department of Environmental Quality requires as part of the review and approval
process, that the City of Kalispell shall provide documentation to quantify and verify the ability
of the municipal water and wastewater system to support extensions, and additional load to the
City utility systems. The following information has been provided by the City of Kalispell and
their Facility Planning Consultant HDR and is summarized to show current and future loads on
the wastewater collection system that is affected by Hwy 93 Water and Wastewater System
Extensions and other development that are planning to connect to the same collection system.
The Collection system's upper end is a gravity system running south along Highway 93 to the
Grandview Lift Station. The Grand view Lift Station pumps wastewater through a force main to
a gravity sewer system which conveys flow to the Wastewater Treatment plant. The following
information shows a static system with peak demands and capacities. The system however, is
dynamic and by the diurnal flow characteristics and physical points of connection, the actual
flow regime will be attenuated through -out the system.
A Wastewater Facility Plan is being completed by HDR, and has proposed wastewater system
improvement project numbers 1 and 2 to address the conveyance system that the Highway 93
North near -term improvements are being designed for (Silverbrook), as well as other
developments currently under construction or being designed. Portions of the Draft Facility Plan
are attached showing these proposed projects.
Grandview Lift Station
The Grandview Lift Station currently operates under an incoming Peak flow of 251 gpm and has
a capacity of 460 gpm.
Proposed Project 91 will install new 30 Horsepower Pumps and bring the wastewater lift station
and associated force main to a peak operating capacity of 860 gpm with one pump on.
Gravity Sewer Downstream of the Grandview Lift Station
The gravity sewer downstream of the Grandview lift station has a current conveyance capacity of
460 gpm.
Proposed Project 92 will install a parallel force main or a parallel gravity sewer to increase
conveyance capacity to 860gpm.
Conclusion
A System capacity of 860 gpm will be provided by City of Kalispell planned projects and will
exceed the peak Demand load of 593 gpm as shown in the remainder of this document.
AD2-2
Table -1 WASTE WATER FLOW GENERATION
Data Source
Extension /
Development
Q Peak
Hourly / Q
Design Ave.
(gpd)
Peak Demand
(gpm)
Cumulative
Demand (gpm)
Scheduled time for Flow
Generation
CTA PER Report
Jaunuary 2007
Silverbrook
792,000
550
City of Kalispell - Flow per
Residential Lot
Silverbrook
(See Table 2)
378
378
0 to 5 year build out
Begin Flow in Summer 2008
City of Kalispell
Hutton Ranch Plaza
48
426
Summer 2008
City of Kalispell
New High School
60
486
Sep-07
City of Kalispell
West View Estates
84
570
0 to 5 year build out
City of Kalispell
Holiday Inn Espress
21
591
Connected
City of Kalispell
Forest Service
2
593
2008
Table -2 KALISPELL HISTORICAL FLOW PER RESITDETIAL LOT
Silverbrook Land Use
Description
Area acres
DU/GA
Pop/DU
Equilvalent
Residential
Lots
Population
Peak Demand =
0.62 gpm /
Residential lot
Residential Lots`
2.5
586
1465
Commercial Lots'
6
4
2.5
?4
60
Total
I
I
1
1 610
1525
378
The City of Kalispell has measured and documented throught the wastewater collection system, that through flow
attenuation over time, the Peak flow atributed to each residence is 0.62 gpm.
Using 0.62 gpm per residence, Table 1 has been modified to show City Anticipated flow from Silverbrook
City Anticipatd flow will be 0.62 gpm ' 610 equivelent Residential lots equals 378 gpm
Silverbrook ultimate population has been revised down during platting and final design from an preliminary population projection of 2,200
as reported in the January 2007 PER to the current population projection of 1,525.
Table - 3 WASTE WATER FLOW CAPACITY
Data Source
Existing and Future
Condition
Grandview
Wastewater
Lift Station
Flow (gpm)
Downstream
Graivty Sewer
Capacity
(gpm)
Scheduled
Time for Flow
Generation
City of Kalispell
Current Peak Flow
255
Existing
City of Kalispell
Current Capacity
460
460
Summer 2008
City of Kalispell / HDR
Project # 1
Grandview Lift Station
Pump Up -sizing
860
To be
Determined
City of Kalispell / HDR
Project #2
Conveyance Systen
Improvements
460
860
To be
Determined
Collection and Conveyance System Capacity after implementing the planned Projects 1 and 2
will provide excess capacity for the propsed wastewater utility system extension and developments.
The System capacity will be 860 gpm and the peak demand will 693 gpm. Excess capacity will be avaliable.
Chapter 5:
Sewer Collection and Conveyance System Analysis
Chapter 5: Sewer Collection and Conveyance
System Analysis
5.1 Introduction
A computer -generated hydraulic model was developed for the City's sewer
collection system using SewerGems software that works in conjunction with a
GIS environment. This model was used to evaluate the existing collection
system and to identify improvements that may be needed to serve existing
customers and future population growth. The primary data source for building
the sanitary sewer model was an AutoCAD drawing of the existing sewer system
maintained by the City of Kalispell. This drawing shows the pipe network and
the location of the pump stations and the treatment plant. The collection and
conveyance system outside of the City limits was delineated into six analysis
areas, as shown in Figure 1-3.
5.2 Sewer Flow Analysis
The sewer system model includes the existing City system along with potential
future system expansions. These future expansion locations were determined
preliminarily in meetings between the consultants and the public works
department. The locations were further developed by examining topography,
roadway locations (potential pipe right-of-way), ground water, and other physical
limitations.
Preliminary sewer conveyance system modeling of the Kalispell area was
performed using the ultimate build out population of 215,100. Pipes and lift
stations were placed according to locations identified by the City and other
logical locations identified during the modeling process. This model resulted in
pipe sizes ranging from 8 inch to 60 inch in size. The theoretical build -out
scenario assumes that every available parcel of land is built upon according to
likely densities developed with public works and planning staff during the basis
of planning phase of this project. The potential for current growth rates to be
sustained over the long term is uncertain. It is expected that population growth
will slow once the "baby boomer" generation has passed. It was determined by
the project team that for the purposes of sizing future infrastructure it would be
overly conservative and costly to design for the ultimate build -out population
scenario. A design year population of 2035 was selected for sizing utility
extensions. Utility routes and easements should be planned with additional right-
of-way set aside for future utilities beyond the 2035 design year.
August 6, 2007 City of Kalispell Wastewater Facility Plan 5-1 Rev 3
Chapter 5: OBSewer Collection and Conveyance System Analysis
5.3 Collection and Conveyance System Analysis
5.3.1 Existing System Analysis and Proposed Improvements
The existing sewer collection system was modeled using SewerGEMS.
SewerGEMS is a Bentley software product that offers interoperability with
AutoCad, ArcView, and Microstation.
There are four main interceptor sewers that collect sewage from the Kalispell
service area and convey it to the wastewater treatment plant. Figure 5-1 is a map
of the existing collection system highlighting these main interceptors. There are
35 sewage lift stations as described in Chapter 3, two of which, the Grandview
pumping station (Lift Station 3) and Fairways pumping station (Lift Station 9),
were evaluated in detail because they serve regional areas with significant growth
pressure and are vital to the city's ability to provide service to these areas. The
forcemains for both of these pumping stations were up -sized in 2007 utilizing
pipe bursting technology to increase capacity.
Line A serves the west side of Kalispell and the Highway 93 corridor north of the
Meridian Road and Highway 93 intersection via the Grandview pumping station.
A significant amount of growth is being planned for the area west and north of
Kalispell. Line A and the Grandview pumping station were evaluated to
determine how much excess capacity, if any, exists for serving growth in these
areas, and if improvements could be made to increase capacity, if necessary, to
serve this growth. The Grandview Lift Station currently has a pumping capacity
of 460 gallons per minute (gpm). It currently sees a peak inflow of 251 gpm
leaving an excess capacity of 209 gpm. The Grandview Lift Station could serve
approximately 372 additional single family units. The gravity sewer main
downstream of the forcemain discharge is at capacity with the Grandview Lift
Station pumping 460 gpm. The maximum capacity of the Grandview pumping
station, if upgraded, was determined to be 860 gallons per minute. Line A, on its
upper end, along Northern Lights and Liberty Streets is already capacity limited
and cannot convey the potential maximum capacity of the Grandview pumping
station and serve customers currently connected to these lines. The system was
modeled with part of the flow directed down Parkway Drive and part of the flow
directed down Northern Lights Street. The Northern Lights and Liberty Streets
route could handle 460 gallons per minute of the Grandview pumping station
flow. If a split structure is constructed at the intersection of Parkway Drive and
Northridge Drive and a second, parallel pipe is installed parallel to the first four
sections of sewer in Parkway Drive this route could handle 400 gallons per
5-2 Rev 3 City of Kalispell Wastewater Facility Plan August 6, 2007
Chapter 5:
Sewer Collection and Conveyance System Analysis
minute from the Grandview pumping station. If new pumps are installed in the
Grandview pumping station so that its full 860 gallon per minute capacity is
achieved, and a split stricture and parallel sewer is constructed in a portion of
Parkway Drive, it is estimated that an additional 1,085 homes could be served by
Line A.
August 6, 2007 City of Kalispell Wastewater Facility Plan 5-3 Rev 3
City of Kalispell
2007 Facility Flan
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Figure 5-2 Existing Sewer
_ Collection System
Excess Capacity Summary
fal City of Kalispell a�MAIEERRLsow
City of Kalispell Public Works Department
Post Office Box 1997, Kalispell, Montana 59903-1997 - Telephone (406) 758-7720, Fax (406) 758-7831
August 8, 2007
Department of Environmental Quality
Public Water Section
Kalispell Regional DEQ Office
109 Cooperative Way, Suite 105
Kalispell, MT 59901
Attention: Emily J. Gillespie, P.E.
RE: Silverbrook Estates
U.S. 93 Utility Main Extension
Kalispell, Montana
Dear Emily,
The City of Kalispell 2007 Wastewater Facility Plan Update (draft) addresses the
sanitary sewer collection system deficiencies below the Silverbrook Estates
development. The areas of concern are (1) the Grandview Lift Station and (2) the
gravity collection system below the Grandview Force Main discharge.
The existing peak flows at the Grandview Lift Station and in the gravity system (just
below the force main) are 251 gallons per minute (gpm). The lift station and the
gravity lines have an existing capacity of 460 gpm. This is derived from the (single)
pump capacity in the duplex lift station and the open channel capacity in the 8" line (8"
vitrified clay, d/D=0.94, n=0.013) below the force main.
Silverbrook Estates will create a peak flow at the Grandview Lift Station of 378 gpm
(610 equivalent residential units X 0.62 gpm peak flow per unit). The City has current
unused commitments at the lift station of 215 gpm. This will create a peak flow of 844
gpm.
The facility plan update defines two projects that will create the necessary capacity to
serve Silverbrook Estates. These projects include: (1) Replace the existing 20 hp
pumps with 30 hp pumps, which will increase the (single) pump capacity to 860 gpm,
and (2) Install a parallel gravity main from Northridge Drive (along Parkway Drive) to
Meridian, which will divert excess flows from the existing 8" gravity main.
When these construction projects are completed, the Kalispell sanitary sewer collection
system will have adequate capacity to serve this development. The City will monitor
the time line of the construction of the residential units within Silverbrook Estates and
construct the upgrades prior to the need for the capacity.
Please feel free to call if you have any questions.
Sincerely,
Frank Castles, P.E.
Assistant City Engineer
cc: Pat White, CTA Architects
City of Kalispell Public Works Department
Post Office Box 1997, Kalispell, Montana 59903-1997 - Telephone (406) 758-7720, Fax (406) 758-7831
August 8, 2007
CTA Architects Engineers
13 N. 23rd Street
Billings, MT 59101
Attention: Pat White, P.E.
RE: Silverbrook Estates
U.S. 93 Utility Main Extension
Kalispell, Montana
Dear Pat,
The City of Kalispell 2007 Wastewater Facility Plan Update (draft) addresses the
sanitary sewer collection system deficiencies below the Silverbrook Estates
development. The areas of concern are (1) the Grandview Lift Station and (2) the
gravity collection system below the Grandview Force Main discharge.
The existing peak flows at the Grandview Lift Station and in the gravity system (just
below the force main) are 251 gallons per minute (gpm). The lift station and the
gravity lines have an existing capacity of 460 gpm. This is derived from the (single)
pump capacity in the duplex lift station and the open channel capacity in the 8" line (8"
vitrified clay, d/D=0.94, n=0.013) below the force main.
Silverbrook Estates will create a peak flow at the Grandview Lift Station of 378 gpm
(610 equivalent residential units X 0.62 gpm peak flow per unit). The City has current
unused commitments at the lift station of 215 gpm. This will create a peak flow of 844
gpm.
The facility plan update defines two projects that will create the necessary capacity to
serve Silverbrook Estates. These projects include: (1) Replace the existing 20 hp
pumps with 30 hp pumps, which will increase the (single) pump capacity to 860 gpm,
and (2) Install a parallel gravity main from Northridge Drive (along Parkway Drive) to
Meridian, which will divert excess flows from the existing 8" gravity main.
When these construction projects are completed, the Kalispell sanitary sewer collection
system will have adequate capacity to serve this development. The City will monitor
the time line of the construction of the residential units within Silverbrook Estates and
construct the upgrades prior to the need for the capacity.
Please feel free to call if you have any questions.
Sincerely,
Frank Castles, P.E.
Assistant City Engineer
City of Kalispell Public Works Department
Post Office Box 1997, Kalispell, Montana 59903-1997 - Telephone (406) 758-7720, Fax (406) 758-7831
August 8, 2007
Environmental Health Services
Flathead City -County Health Department
1035 First Avenue West
Kalispell, Montana 59901
Attention: Dick Montgomery, P.E.
RE: Silverbrook Estates
U.S. 93 Utility Main Extension
Kalispell, Montana
Dear Dick,
The City of Kalispell 2007 Wastewater Facility Plan Update (draft) addresses the
sanitary sewer collection system deficiencies below the Silverbrook Estates
development. The areas of concern are (1) the Grandview Lift Station and (2) the
gravity collection system below the Grandview Force Main discharge.
The existing peak flows at the Grandview Lift Station and in the gravity system (just
below the force main) are 251 gallons per minute (gpm). The lift station and the
gravity lines have an existing capacity of 460 gpm. This is derived from the (single)
pump capacity in the duplex lift station and the open channel capacity in the 8" line (8"
vitrified clay, d/D=0.94, n=0.013) below the force main.
Silverbrook Estates will create a peak flow at the Grandview Lift Station of 378 gpm
(610 equivalent residential units X 0.62 gpm peak flow per unit). The City has current
unused commitments at the lift station of 215 gpm. This will create a peak flow of 844
gpm.
The facility plan update defines two projects that will create the necessary capacity to
serve Silverbrook Estates. These projects include: (1) Replace the existing 20 hp
pumps with 30 hp pumps, which will increase the (single) pump capacity to 860 gpm,
and (2) Install a parallel gravity main from Northridge Drive (along Parkway Drive) to
Meridian, which will divert excess flows from the existing 8" gravity main.
When these construction projects are completed, the Kalispell sanitary sewer collection
system will have adequate capacity to serve this development. The City will monitor
the time line of the construction of the residential units within Silverbrook Estates and
construct the upgrades prior to the need for the capacity.
Please feel free to call if you have any questions.
Sincerely,
Frank Castles, P.E.
Assistant City Engineer
cc: Pat White, CTA Architects
City of Kalispell Public Works Department
Post Office Box 1997, Kalispell, Montana 59903-1997 - Telephone (406)758-7720, Fax (406)758-7831
August 14, 2007
Department of Environmental Quality
Public Water Supply Section
Permitting and Compliance Division
109 Cooperative Way, Suite 105
Kalispell, Montana 59901-2389
Attention: Emily Gillespie, P.E.
Environmental Engineer
RE: Silverbrook Estates
U.S. 93 Utility Main Extension
Kalispell, Montana
Dear Emily,
This letter is to confirm that the City of Kalispell has reviewed and approved the
construction plans and specifications prepared by CTA Architects and Engineers, Inc.,
for the water main(s), sanitary sewer main(s), sewer force main(s), sewage pumping
station and appurtenant items.
The Kalispell water distribution system and sanitary sewer system has adequate
capacity to serve the project.
Please feel free to call if you have any questions.
Sincer I
Fra Castles, P.E.
Deputy Public Works Director/Assistant City Engineer
cc: Pat White, P.E.
CTA Architects and Engineers, Inc.
P.O. Box 1439
Billings, Montana 59101
r City of Kalispell Public Works Department
Post ice Box 1997, Kalispell, Montana 59903-1997 - Telephone (406) 758-7720, Fax (406) 758-7831
August 14, 2007
Environmental Health Services
Flathead City -County Health Department
1035 First Avenue West
Kalispell, Montana 59901
Attention: Dick Montgomery, P.E.
RE: Silverbrook Estates
U.S. 93 Utility Main Extension
Kalispell, Montana
Dear Dick,
This letter is to confirm that the City of Kalispell has reviewed and approved the
construction plans and specifications prepared by CTA Architects and Engineers, Inc.,
for the water main(s), sanitary sewer main(s), sewer force main(s), sewage pumping
station and appurtenant items.
The Kalispell water distribution system and sanitary sewer system has adequate
capacity to serve the project.
Please feel free to call if you have any questions.
Sinc r y,
F nk Castle , P.E.
Deputy Public Works Director/Assistant City Engineer
cc: Pat White, P.E.
CTA Architects and Engineers, Inc.
P.O. Box 1439
Billings, Montana 59101