HomeMy WebLinkAboutWWP273473 (11)RENTON
111E th (II I III < 1 N\ t
Stonegate II
Alternatives Analysis Report
November 2007
Prepared By
Roth Hill Engineering Partners, LLC
2600 116th Avenue NE #100
Bellevue, WA 98004
(425)869-9448
CERTIFICATION
This Stonegate II Alternatives Analysis Report for the City of Renton was prepared by Roth Hill
Engineering Partners, LLC, under the direction of the following:
xt,
ony F sher, PE
Project Manager
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,
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Erik Brodahl, PE
EXPIRES 1 1 -01 -LobB
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EXPIRES 2-25-2-op%
Rot H i I I City of Renton
Stonegate 11 Alternatives Analysis Report
Pate No.
EXECUTIVE SUMMARY..................................................................... E.1
CHAPTER 1 - INTRODUCTION
PROJECTPURPOSE............................................................................... 1.1
BACKGROUND....................................................................................... 1.1
AUTHORIZATION.................................................................................... 1.2
REPORT ORGANIZATION....................................................................... 1.2
CHAPTER 2 - HYDRAULIC ANALYSIS
PLANNING DATA AND FLOW ASSIGNMENTS ......................................... 2.1
MODELANALYSIS.................................................................................. 2.2
ANALYSISRESULTS...............................................................................2.4
Within Field Avenue NE..................................................................... 2.5
Within NE Sunset Boulevard..............................................................2.5
TOTAL DYNAMIC HEAD COMPUTATIONS...............................................2.5
HYDRAULIC JUMP ANALYSIS.................................................................2.6
CHAPTER 3 - ROUTE ANALYSIS
ROUTE ALTERNATIVES..........................................................................3.1
Summerwind Gravity Sewer Alternative ..............................................
3.1
Force Main Alternative #1..................................................................3.2
Force Main Alternative #2..................................................................3.3
Force Main Alternative #3..................................................................3.4
Field Avenue Interceptor Improvements..............................................3.6
Sunset Interceptor Improvements.......................................................
3.7
Proposed Gravity Sewer Service........................................................
3.7
CHAPTER 4 - GEOTECHNICAL AND WETLANDS REPORTS
GEOTECHNICAL REPORT......................................................................4.1
LocalGeology................................................................................... 4.1
ErosionHazards................................................................................ 4.1
Landslide -Steep Slope Hazards.........................................................4.1
SeismicHazards...............................................................................4.2
Groundwater.....................................................................................4.2
Pipe-Bursting/Pipe-Reaming..............................................................4.3
WETLANDSREPORT..............................................................................4.3
RothHill City of Renton
%'' Stonegate 11 Alternatives Analysis Report i
TABLE OF CONTENTS
RENTON
Ini—n, 11.111—
CHAPTER 5 - PERMITTING AND EASEMENT REQUIREMENTS
PERMITTING REQUIREMENTS...............................................................
5.1
General Notes and Comments Concerning Permits .............................
5.2
EASEMENT REQUIREMENTS.................................................................5.2
Summerwind Gravity Sewer...............................................................
5.3
Force Main Alternative #1..................................................................5.3
Force Main Alternative #2..................................................................
5.3
Force Main Alternatives #3A & #313 ....................................................
5.3
EASEMENT VALUATION METHODOLOGY ...............................................
5.4
CHAPTER 6 - OPINION OF PROBABLE CONSTRUCTION COSTS
STONEGATE II LIFT STATION INSTALLATION ........................................ 6.2
SUMMERWIND GRAVITY SEWER ALTERNATIVE....................................6.3
FORCE MAIN ALTERNATIVES.................................................................6.4
FIELD AVENUE INTERCEPTOR IMPROVEMENTS ................................... 6.5
SUNSET INTERCEPTOR IMPROVEMENTS..............................................6.6
PROPOSED GRAVITY SEWER ALTERNATIVES......................................6.7
CHAPTER 7 - RECOMMENDATIONS
RECOMMENDATIONS............................................................................. 7.1
Summerwind Gravity Sewer Alternative .............................................. 7.1
Force Main Alternatives..................................................................... 7.1
Field Avenue Interceptor Alternatives ................................................. 7.1
Sunset Interceptor Improvements....................................................... 7.2
Proposed Gravity Sewer Alternatives.................................................. 7.2
ESTIMATE OF TOTAL PROJECT COST...................................................7.2
LIST OF TABLES
Table E-1 Estimation of Total Project Cost................................................E.2
Table 5-1 Permitting Requirements...........................................................
5.1
Table 5-2 Easement Requirements — Alternative #3A & #313 ......................
5.4
Table 6-1 Opinion of Probable Cost Stonegate Lift Station Installation ........
6.2
Table 6-2 Opinion of Probable Cost Summerwind Gravity
Sewer Alternative.................................................................................
6.3
Table 6-3 Opinion of Probable Cost - Force Main Alternatives ....................
6.4
Table 6-4 Opinion of Probable Cost - Field Avenue Interceptor
Improvements.......................................................................................
6.5
Table 6-5 Opinion of Probable Cost Sunset Interceptor
Improvements.......................................................................................
6.6
Table 6-6 Opinion of Probable Cost Proposed Gravity Sewer
Alternatives..........................................................................................
6.7
Table 7-1 Estimation of Total Project Cost ................................................
7.2
City of Renton RothHill
ii Stonegate 11 Alternatives Analysis Report `--�
RENTON
TABLE OF CONTENTS
LIST OF FIGURES
Figure1-1 Project Area............................................................................ 1.3
Figure 2-1 Stonegate/Summerwind Service Area.......................................2.9
Figure 2-2 Stonegate Service Area Projected Parcel Subdivisions............
2.10
Figure 2-3 Projected Ultimate Capacity Issues ........................................
2.11
Figure 2-4A Projected Maximum HGL in Field Avenue NE
(before improvements)........................................................................
2.12
Figure 2-413 Projected Maximum HGL in NE Sunset Boulevard
(before improvements)........................................................................
2.13
Figure 2-4C Projected Maximum HGL in Field Avenue NE
(post improvements)...........................................................................
2.14
Figure 2-41D Projected Maximum HGL in NE Sunset Boulevard
(post improvements)...........................................................................
2.15
Figure 3-1 Summerwind Gravity Line ........................................................
3.9
Figure 3-2 Force Main Alternative #1......................................................
3.10
Figure 3-3 Force Main Alternative #2......................................................
3.11
Figure 3-4 Force Main Alternative#3A....................................................
3.12
Figure 3-5 Force Main Alternative #3B....................................................
3.13
Figure 3-6 Field Avenue Interceptor Improvements ..................................
3.14
Figure 3-7 Sunset Interceptor Improvements...........................................3.15
Figure 3-8 Proposed Gravity Sewer Alternative#1...................................
3.16
Figure 3-9 Proposed Gravity Sewer Alternative#2...................................
3.17
Figure 5-1 Potential Non Right -of -Way Construction ..................................
5.5
LIST OF APPENDICES
Appendix A — Preliminary Geotechnical Report
Appendix B — Wetlands Technical Memorandum
Appendix C — Construction Cost Estimates
RothHill City of Renton
..-� Stonegate 11 Alternatives Analysis Report iii
Executive
Summary
At the request of the City of Renton, Roth Hill Engineering Partners, LLC prepared this
Alternatives Analysis Report for the proposed Stonegate II project. The analysis
examined the service area and associated sewer facilities tributary to the existing
Stonegate and Summerwind Lift Stations in order to determine current and future
design flows. The analysis also evaluated various potential force main routes to convey
flow from the new lift station to the existing system and identified regulatory and
easement requirements associated with each route alternative. Finally, this analysis
evaluated the feasibility of providing sewer service to a potion of the subbasin between
the existing Stonegate development and 148th Avenue SE, as well as required
improvements to the Field Avenue Interceptor and the Sunset Interceptor.
The goal of the Alternatives Analysis Report was to evaluate alternative solutions and
clarify project requirements before proceeding with design and construction. The
following paragraphs summarize the results of the Alternatives Analysis Report.
The hydraulic analysis performed for this report identified that the new Stonegate II
Lift Station would need a pumping capacity of pump approximately 425 gpm at a Total
Dynamic Head (TDH) of 150 feet for current planning and flow conditions. The new
stations pumping capacity would need to increase to approximately 775 gpm at a TDH
of 180 feet for ultimate conditions. In addition, the following pipe capacity issues were
identified:
• Surcharging in the existing 8-inch sewer main between Manhole (MH) 5303218
and 5303228 in Field Avenue NE.
• Surcharging in the existing 8-inch pipe between MH 5303216 and 5303219 in
NE Sunset Boulevard.
• Surcharging in the existing 8-inch pipe between MH 5303326 and 5303327 in
NE 26th Street under ultimate flow conditions with an expanded Urban Growth
Boundary (UGB) that encompasses all of the land area that can physically drain
to the station via gravity flow. This pipe has adequate capacity to convey the
ultimate flows within the current UGB.
In addition, the Sunset Interceptor Phase 3 Pre -Design Report identified surcharging in
the existing 12-inch and 15-inch sewer mains along NE Sunset Boulevard between
Union Avenue NE (MH 5303185) and Anacortes Avenue NE (MH 5303090).
The hydraulic analysis also evaluated the likelihood of a hydraulic jump occurring in
the Field Avenue Interceptor. The analysis determined that a weak or oscillating jump
Rot N i I I City of Renton
%___ Stonegate 11 Alternatives Analysis Report EA
EXECUTIVE SUMMARY R E N T O N
may occur in the vicinity of MH 5303228 and MH 5303225. Therefore, this report
recommends MH 5303229, MH 5303228, and MH 5303225 receive protective coatings
to combat potential corrosion from hydrogen sulfide gas release. In addition, odors
may be released by the hydraulic jump at these locations. The potential odors may be
mitigated by chemical additives introduced at the lift station.
The route analysis performed for this report evaluated the route and construction
method alternatives for five different pipe segments related to the project. The analysis
also investigated issues related to geotechnical requirements, wetlands requirements,
permitting issues, and easement requirements. The following list summarizes the
recommendations generated from the route analysis and the piping improvements
needed to address surcharging issues.
Summerwind Gravity Sewer:
• Install approximately 245 feet of 8-inch diameter HDPE pipe between the
existing Summerwind Lift Station and MH 5303317 on NE 24'h Court using
horizontal directional drilling technology.
Stonegate Force Main:
• Install approximately 3,925 feet of 8-inch diameter PVC force main along the
route for Force Main Alternative #313.
Field Avenue Interceptor Improvements:
• Upsize approximately 90 feet of 8-inch sewer main along Field Avenue NE
between MH 5303218 and 5303221 with 16-inch diameter HDPE sewer main
using pipe -bursting technology.
• Upsize approximately 880 feet of 8-inch sewer main between MH 5303221 and
5303228 with 14-inch diameter HDPE sewer main using pipe -bursting
technology.
Sunset Interceptor Improvements:
• Construct approximately 65 feet of 18-inch diameter PVC sewer main using
open -trench construction methods along NE Sunset Boulevard between MH
5303185 and a new proposed MH 5303185A located approximately 55 feet east
of MH 5303104.
• Upsize approximately 530 feet of 12-inch and 15-inch concrete sewer main
along NE Sunset Boulevard between the new proposed MH 5303185A and
Whitman Court NE (MH 5303099) with 20-inch diameter HDPE sewer main
using pipe -bursting technology.
City of Renton Rot Hill
E.2 Stonegate 11 Alternatives Analysis Report %__�
R E N T O N EXECUTIVE SUMMARY
• Upsize approximately 790 feet of 12-inch concrete sewer main along NE Sunset
Boulevard between Whitman Court NE (MH 5303099) and Anacortes Avenue
NE (MH 5303090) with 16-inch diameter HDPE sewer main using pipe -bursting
technology.
• Upsize approximately 500 feet of 8-inch concrete sewer main along NE Sunset
Boulevard between MH 5303216 and MH 5303218 with 16-inch diameter HDPE
sewer main using pipe -bursting technology.
• Upsize approximately 120 feet of 8-inch concrete sewer main along NE Sunset
Boulevard between MH 5303218 and MH 5303219 with 14-inch diameter HDPE
sewer main using pipe -bursting technology.
Table E-1 summarizes the project budgets that may be used by the City for planning
purposes for the recommended improvements. Table E-1 does not include any costs
associated with constructing a gravity sewer to serve the lots between 1481h Avenue SE
and the tributary Creek to May Creek. The construction costs shown include tax at
8.9% and a 15% contingency.
Desci•iptiori
Cost:.
Summerwind Gravity Sewer Cost
_.....................................................-..................._................_....................._....__......................................................._....._._..._....................... ...........
$70,715
....................._
Force Main Alternative #3B Cost
_.........................................................................................................................__................................_.1...........__....................................................... ....._.........................
____ .....................
$670,925
Field Avenue Interceptor Cost (Trenchless)
.................................................................._.............................................._._......._......................................................................................
._............. _...... .._.. _._... .............
$254,700
Sunset Interceptor Improvements (Trenchless)
_............................._........__..._........_........_.............._.............................................................._.............._.......................................__................_.........-................._................
- _.......__..............._..............
$561,900
Stonegate lI Lift Station Cost
$1,560,000
TOTAL CONSTRUCTION COST
$3,118,240
Engineering
$749,660
TOTAL PROJECT COST
$3,867,900
Rom H i I I City of Renton
Stonegate 11 Alternatives Analysis Report E.3
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Chapter 1
PROJECT PURPOSE
The purpose of this report is to evaluate the improvements required to efficiently serve
the City of Renton's Stonegate and Summerwind drainage basins. An alternative
analysis of the conveyance systems required to serve the area was performed along with
a hydraulic analysis to determine design flows and piping modifications. Several
routes for the proposed force main were analyzed, including potential impacts during
construction, geotechnical considerations, sensitive area impacts, and permitting and
easement requirements, in order to determine a preferred alternative. In addition,
planning level construction costs and a project plan for the design phase of the
Stonegate 11 project were prepared to assist the City in planning for the project.
BACKGROUND
The City of Renton currently operates sanitary sewer collection and conveyance
systems within its upper May Creek/Honey Creek Subbasins in the northeast portion of
the City bordered by 148`h Avenue SE to the east and May Valley Road to the north.
These systems include two sewer lift stations that serve a large portion of the area. The
existing Summerwind Lift Station serves approximately half of the Summerwind
development and the existing Stonegate Lift Station serves several existing and future
developments along the 148`h Avenue SE corridor. The City has identified a project to
meet ultimate sanitary sewer capacity needs within the identified subbasins by
consolidating the two existing sewer lift stations and constructing piping improvements
to serve the ultimate capacity needs. The project is known as the Stonegate II project.
The project area can be seen in Figure 1-1.
The City of Renton requested Roth Hill Engineering perform an alternatives analysis of
the proposed Stonegate II project. The analysis examined the service area and
associated sewer facilities tributary to the existing Stonegate and Summerwind Lift
Stations in order to determine current and future design flows. The analysis also
evaluated various potential force main routes to convey now from the new lift station
to the existing system and identified regulatory and easement requirements associated
with each route alternative. Finally, this analysis evaluated the feasibility of providing
sewer service to a portion of the subbasin between the existing Stonegate development
and 148`h Avenue SE, as well as required improvements to both the Field Avenue
Interceptor and the Sunset Interceptor.
City of Renton
RO L"n i l l
%-- Stonegate 11 Alternatives Analysis Report 1.1
CHAPTER 1- INTRODUCTION R E N T O N'
The goal of the alternatives analysis was to evaluate alternative solutions and clarify
project requirements before proceeding with design and construction. This report
concludes with alternative recommendations and corresponding planning level opinions
of probable construction costs.
AUTHORIZATION
The City of Renton executed Contract CAG-07-077 with Roth Hill Engineering
Partners, LLC on April 30, 2007.
REPORT ORGANIZATION
The Alternatives Analysis Report includes the following sections:
Executive Summary
Chapter 1 - Introduction
Chapter 2 - Hydraulic Analysis
Chapter 3 - Route Analysis
Chapter 4 - Geotechnical and Wetlands Reports
Chapter 5 - Permitting and Easement Requirements
Chapter 6 - Opinion of Probable Construction Costs
Chapter 7 - Recommendations
Appendix A - Geotechnical Report
Appendix B - Wetlands Technical Memorandum
Appendix C - Construction Cost Estimates
City of Renton RothHill
1.2 Stonegate 11 Alternatives Analysis Report
[ 0/0-manning -Maximum Stonegate Ultimate inside UGB 8-19-08.PRF
189200.0 [
,eel5o.o im 120
198100.0 ■ 0.80 1.00 53om 6 v
188050.0 ■ 0.80 0.80 - - - - - - - - - - - - - 5 - - - - - - - - - - - - - 5303202 5303203 5303201--
< 0.00 53
- O-----��-
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---- -
C
187950.0 _ _ - _ _ - p_ _ _ _ _ - - - - - _ - - - - _ - _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
,53030fi2
18790D.0- - _ O-.. -- - ---- - --- ------- ------ -- ----. -- - - _ -- - - - - - - - - --- --- -- -- - - 5303222--
187850.0 - 5304127 _
/y�{ _ _ _ _ _ _ 5303082
O 5303189
1878W.0 _ 5303061
5303060
187750.0 _ O O 53030058 530309B ..
- 5303069
197700.0 - - - - - 5303083
187660.0- ---- -- - - - -
187600.0 - - - - - _ _ 5303221
5303178
187550.0 O, 5303177 -7.7
SIi037
53303i247 53MI75 O S3D3218167M.0 - C 530�45303217
187450.0-. - - - - - 5303251 530'3093 0____,- _ `..*,1`hD340.5 _
197400.0 - M117 5=161
5303066
187350.0 _ 5303246 - , �.� 5303406
3408
137300.0 - •l 5303252- r •.
5303329 5303249 O l M �
187250.0 -. O [j
187200.0 - _ - - - - - - - J -
5303245 - - - - - ---' Si03328 - -- '--------
--- 5303167
187150.0- - - - - - - > - - - v - - - _ _ _ - _ - _ - - _ _ _ _ _ _ _ _ _ _ _
- •_---.
187050.0 - 1- - 5303193 - -
- _ _ _ O
187050.0 530311503114 p -
18700D.0
186960.0 -. 5303112 5303244 53 � 18 53030192 O
53032D9
186850.0-_ 5303110 5303t11 _ ____ -_ 5303210 ______ _ _ ________ - - - - - - -
530315303178 ZOlOAD3
166800.0-- 5303120 _ - -- ------ _�_-_�__--_ -- ••
1%750.0 •\4 - 53031BB
188700.0tS103_t711
186650.0 - - - - - 1 5303t85 ` - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
�5303172
5303119 5303099- ___ _____�_____ ___
5303106 5303105, 5=118 4 5303096 _ _ _ _ _ _ _ _ _ _ _ _ _
186600.0 O : �5303104 a---F' 0
M103 M03102 MIX1101
186550.0'- _ _ _ _ _ _ _ _ . _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ r _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ - _ _ _
186500.0 - - _ - _ _ _ _ _ - 53D3100 _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ r - _ _ _ _ _ _ _ _ _ _. - _ - - _ - - _ - - _ -
v
losm.0 - _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 5303206 _ _ _ - - _ - - - - - - _ _ _ _ _ _ _ _ _ - _ _ - - _ - - - _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ r _ _ - - _ _ - _ _ _ - _ _ _ _ _ _ _ - - - - -
186400.0 _ 5303348 0 5303211
O
186350.0
C> 530310978
p 5310002 5310006 53100W
5310000
188300.0 00 5310203 53102(11 5310206�.,¢ 5310003 5310001 53100006 --.. ' '- --- .. 'Q
188M.0;' --
- - - - - - - - - - - - - - - - -
- - - - - - - - I - - - - - - - - - - - - - - - - - - - - - - - - - - - -
186150.0 '
SM t
186100.0 _� 53IMM 5310207
186M0-: D�41-
~�-----rrn----rl
1311200.0 1311400.0 1311800.0 131"no 1312000.0 1312200.0 1312100.0 1312800.0 1312910.0 r, 13130MO 1313200.0 1313100.0 1313600.0 13139q.0 1314000.0 1314200.0 1314400.0
Post] p / Q-manning - Maximum Stonegate 2006-Nov 90 Storm 9-11-08 PRF
166Z00.0 11 - ---------------- ----------------
188150.0 ■ 1.20 5303�3
100 1 20 p
168100.0- ■ 0.80 1.00 5303065 5303055S303202 5303203 5363204
---- 03 ---
1BBD50.0 0.60 0.80 5304265 - - - - - - - - - - - - - - .
0.60 O 5003084 5303056 _ _ _ _ _ _. _
1BB000.0 _
5303063
187950.0 O
5303062
187900.0_ _ _ _ -. _ _ O _ _ _ _ - _ . _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ - _ - - _ _ _ _ - _ _ 5306272_ - - -.
5304126 5304127 Q
. o c
187800.0 - 5303061 53MM 53o3o5B
187750.0 - O -
s3a1o69 :.
187700.0- - - - - - - - - - - - - .. - - -53MM- - - - - - -
187650.0
_ d
187600.0 - - - - - -
187550.0 5304212 - 3M3 - - - - 5303247 - - - - - - - - - - - - - - - - - - - - -,,,MMI
5303O-1n - - - - - - - - - - - - - - -Q - - s3Q
5304213175 5303218 _ [
187500.0O _ _ _ _ _ _ _ _ _ _ _ _ _ 5303084_ _ - - - - - - - - - - - - - - --5303217
5303250
187450.0 - p 5303251
5300093 .�--
187400.0 - 5303117 C 5303086
18M ()-304134 p � 5303246 53D^3WnB 53034pg
lei .0- - - - - 0- - - - - 53a�s2 - - - - - - - - - -,.0 - - _ _. - - - - - - - - - - - - - - - - - - - - --
187250.0
5304135 5303329 5=49 p 5303409,-
-_ o o 0 .53D3087
167200.0 - 5300245 8 - ,,5303167
187150.0- - - - -- -- ----- 4 - 5303410 d
-------------
187100.0 ! 5303193 5303253 ,-.0 5303168
187050.0 - 53M11509114 O 5303Zp5303092 --' -
O O + 5303411
7000 18.0- - - ---M-----------530.o'121B- - 53034123 ° - -- --- - - - - -- -- - -- - -----------------
186950.0 5303112 11 5303091/511
0N �
186900.0 ' y p
106660.0 - 5303110 5303111 _ - 5303210
A
- - - - - - - - - - - -
5304230 O C' - _ _ _ _ 530015303178 - _ - _ _ _ _ 21Q4D3
5303243 530312E �E -�Q _ _ _ _ _ _ -
166750.0 5303169
188650.0- 5303185 --- ---------- -- - - - - - - - - - - - -* -- ----
53oazzs - - - - -__ - - --
O 172
- s3o311s 9
- ------- - - - - --
5309108 5303105, 5303118 5303086
O 5303103 5103102 5303101
168550.o-- - - - - O - ____ ____ -- __-_, _ - _ - ____ ____ _____ ____
186600.0- - - - - O 5303100---_-_____ _1__ ..__.---______--
166450.0 - 5303208 5303206
188400.0- - - 5303348_ - - - - - _ _ _ b_ . _ _ _ _ _O _ - - - - - - - - - 5303211- - - _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ -------------
0
O
186350.0- - 530B2i3 530310�8 _ _ - ______ __ _______ -_ _________--__ -_-----___________-
- O 5310002 5310MB 5310007 - 5310008
166300.0 - - �- 5310203 5310204 _ - 5310�-. -- - - 00 - _ _ _ _ _ _ _ _ . Si10004 - _ _ 531pp006
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ .�
186250.0 - O O O O O _ -6
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186t50.0 J0924 - - - ---__-_-_ __ ___.. __
5308266 __ ____ _._ _ .
186100.0 - C, _ _ , .. Q 53---10Z-M � --- ---531OX7
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IOM.0_ _ _ _ _ _ _ _ _ _ _ - - _ - - - _ _ - - _ - 5310Q10-53100/1_ _ _ _ - - - - - - - - - - - - - _ _ _ _ _ _ _ _ _ _ _ _ - - - - - - _ _ _ _ - _ ---
5310208
186960.0 _ O .. - - - _ _ __- -O-_.---+4- ._... -0
1311000.0 13112p.0 1311400.0 1311600.0 131180D.0 1312000.0 131220D.0 1312400.0 13120MO 1312 0D.0 1313000.0 13/3200.0 1313400.0 1313600.0 1313600.0 131400.0 13142MG
w
Link Water Level - 24-11-1990 11:19:18 Stonegate 2006-Nov 90 Storm 9-11-08.PRF
Discharge
0.207
0.198 0.186
0.186
0.181
cfs
NA
Nb
[feet]
411.0 -
410.5-
-
-
----- -
- - - --
--,
410.0-
----
- - - --
r-- -
- ---
-----
-------
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409.0-
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-------------------
408. -
-
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-----
------ -
- - ---
-
--
-----------------
407.5 -
407.0 -
-
-
- -
406.5-
--- - -- - - - - --
I
406.0
405.5
405.0
--------------
404.0-
--- -
- - - --
----------------------
-
403.5-
--
-------�-
----------'-
402.5 -
401.0 -
400.5 -
400.0 -
399.5 -
399.0 -
-
398.5 -
398.0 -
397.5
0.0
50.0 100.0
150.0 200.0
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N STONEGATE II ROUTE ANALYSIS
FIGURE 1-1
W E
PROJECT AREA
S
RothHill
Chapter 2
PLANNING DATA AND FLOW ASSIGNMENTS
The Stonegate/Summerwind service area was broken into five areas in order to develop
population and sanitary sewer flow assignments for sizing the proposed Stonegate 11
Lift Station. The existing properties served by the Stonegate and Summerwind Lift
Stations were determined by reviewing the layout of the existing sewer system.
Locations of developments currently under construction that will be tributary to the
Stonegate Lift Station were provided by City Staff and a review of Roth Hill's in-house
records from overlapping clients. The projected future Stonegate 11 service area within
the UGB was determined by examining the general topography of the area to determine
the expected layout and direction of future sewer mains. City staff was consulted to
' address ongoing or future improvements that may impact the future sewer system
network. The Ultimate Stonegate service area was determined by examining areas
outside the UGB using the same methods as for the projected Stonegate service area
' within the UGB. These five areas are shown in Figure 2-1.
The areas currently served by the Stonegate and Summerwind Lift Stations consist
primarily of single-family residential homes. Population assignments were computed
by determining the number of lots, multiplied by a standard single-family residential
size of 2.5 persons per household, as assumed per City wastewater planning
' recommendations. Populations for areas currently under development were calculated
using similar methodology. These populations were then assigned to representative
manholes within the hydraulic model.
For the projected Stonegate 11 service area inside the UGB and the Ultimate tributary
y
area outside the boundary, the parcels were reviewed using aerial photographs and
parcel tax record data to estimate locations with good potential of future growth. These
locations are shown in Figure 2-2. The areas were determined using G1S, and the
future numbers of lots were calculated assuming R-4 zoning (four single-family
residential lots per acre). All other existing parcels, except for areas zoned as
parks/open space, were assumed to consist of single-family lots in order to establish the
ultimate population.
For portions of the system developed through the year 2001, the computed per -capita
sanitary sewer flow rates from the previously developed 2001 Model were used. For
flow assignments to portions of the system constructed after 2001 and future service
areas, a flow rate of 100 gallons per person per day was assumed for the residential
' population, with a peaking factor of 2.0, consistent with the City's wastewater planning
standard.
RothHill City of Renton
L Stonegate 11 Alternatives Analysis Report 2.1
CHAPTER 2 — HYDRAULIC ANALYSIS RENTON
The computations described above allowed area assignments to be further refined
compared to the efforts relating to previous analyses. These area assignments were
used to generate infiltration and inflow (I&I) in the model. The I&I parameters from
the calibrated 2001 Model were assigned to those portions of the system developed
through the year 2001. For the Ultimate Stonegate II Model, these parameters were
adjusted to generate an I&I increase of 28% from the 2001 Model, to represent
degradation of the system in accordance with King County's methodology.
Infiltration and inflow within the system constructed after 2001 and for future service
areas was assigned at 1,500 gallons per acre per day, consistent with the City's
standards for new portions of the system.
Areas downstream of the Summerwind/Stonegate service areas were included in the
investigation in order to model flows into the Field Avenue and Sunset Interceptors, to
evaluate backwater impacts, and to address capacity issues in the interceptors. The
sanitary and I&I flow assignments for these downstream portions of the system were
consistent with the assignments to the overall Ultimate Model, as described in the
Ultimate Model report, dated July 2006.
MODEL ANALYSIS
The Stonegate and Summerwind Lift Station service areas were previously modeled as
part of the Renton Ultimate Sewer Model using the hydraulic modeling software
program MOUSE Tm by the Danish Hydraulic Institute (DHI). The original analyses
were performed using Renton Traffic Analysis Zone (RTAZ) projections for the area
and broad assumptions to determine the ultimate sewer service boundaries. For this
investigation, the Stonegate II Study Area was separated from the Renton Ultimate
Model. Modifications were made to the physical model reflecting data from the design
survey for the Sunset Interceptor Phase 3 project and an "as -built" survey of the NE
Sunset Boulevard/Duvall Avenue NE Intersection Improvements project. The flow
assignments were re-evaluated using topographic information and a detailed review of
existing and proposed development tributary to the proposed Stonegate II Lift Station,
as described in the previous section of this report.
Two model scenarios were analyzed to determine projected flows to the proposed
Stonegate It Lift Station. These flows were then used to size the lift station facility and
the proposed force main to convey flows from the lift station, as well as to evaluate
necessary improvements to the existing gravity sewer system downstream from the lift
station.
Scenario No. 1 included flows from the existing Stonegate/Summerwind service area
and the projected Stonegate II service area within the UGB. Flows from the projected
sewer service area were added as point loads to appropriate locations in the existing
system based on local topography. The November 24, 1990 storm was used to simulate
City of Renton Rot H i
II
2.2 Stonegate 11 Alternatives Analysis Report %_
' R E N T O N CHAPTER 2- HYDRAULIC ANALYSIS
the 20-year peak storm event. Results of this scenario indicate a peak inflow rate of
approximately 425 gallons per minute (gpm) to the Stonegate II Lift Station.
Scenario No. 2 added the service area modeled in Scenario 1 to the Ultimate tributary
' service area outside the UGB. Again, these inflows were added as point loads to the
system. This scenario yielded a peak inflow rate of approximately 765 gpm.
Therefore, an interim build -out to the current UGB design flow rate of 425 gpm and an
Ultimate design flow rate of 775 gpm were assumed for the proposed Stonegate II Lift
Station project.
' The flow rates mentioned above were used to size the force main. An 8-inch diameter
PVC pipe would experience a velocity of approximately 4.9 feet per second at 775 gpm.
The 8-inch diameter force main would also allow for an adequate scouring velocity of
approximately 2.7 feet per second for the interim design flow rate of 425 gpm,
corresponding to the build -out condition within the UGB. The force main was assumed
' to discharge to MH 5303229, located in the north end of Field Avenue NE.
Additional hydraulic studies were then performed to evaluate the capability of the
downstream Field Avenue and Sunset Interceptors to convey the Ultimate design
pumping rate for the lift station. The section of the Sunset Interceptor reviewed for this
project was previously analyzed during the Sunset Interceptor, Phase 3 project.
However, it was necessary to verify these results with the updated pipe and manhole
data in addition to the updated design flow rate as determined in Scenario No. 2. The
results of this analysis are displayed on Figure 2-3. Significant surcharging occurred
in portions of the Sunset Interceptor in the manholes east of Duvall Avenue NE to Field
Avenue NE. Moderate surcharging was observed in Sunset Boulevard NE between
approximately Whitman Court NE and Anacortes Avenue NE. Significant surcharging
' was apparent in the majority of the pipes in the Field Avenue Interceptor, north from
NE Sunset Boulevard to NE 19th Court.
The model was then used to evaluate the appropriate size of the interceptors to alleviate
the capacity issues. As discussed later in this report, possible options for improving the
capacity include pipe -bursting and open -cut replacement. Given the depths of the
' sewers and anticipated soil conditions, the sewer inverts following pipe -bursting should
closely match the existing inverts. The modeling assumed that the open -trench
alternative would keep the same line and grade as the existing pipe, except where
' realignment was proposed. Therefore, a separate model analysis was not performed for
the open -cut construction alternative.
' The recommended improvements to the Sunset and Field Avenue Interceptors would
eliminate surcharging issues and allow projected pipe flows to comply with the City's
design capacity criteria. A more detailed description of the capacity issues and the
' recommended improvements is provided in the next section.
1
- ------- ------
- -
t
City of Renton
RothHill
.-I Stonegate 11 Alternatives Analysis Report 2.3
CHAPTER 2— HYDRAULIC ANALYSIS R E N T O N
ANALYSIS RESULTS
The pipes in Figure 2-3 were color -coded by peak flows divided by maximum capacity
(Q/Qf,,,,), based on Manning's equation. This color coding scheme is consistent with
the previous results from the various analyses that were provided to the City and is
summarized below:
Peak Q/f,,,,
Color
Greater than 1.2
Red
1.0 to 1.2
0.8 to 1.0
Green
0.6to08
Blue
0.0to0.6
Gray
All pipes with ratios greater than 0.8 (color coded green, orange, or red) are considered
to be exceeding their capacity. Significantly surcharging pipes are coded red with
ratios larger than 1.2. Moderately surcharging pipes are represented by ratios of 1.0 to
1.2 and are color coded orange. Green colored pipes have flows that exceed the pipes
capacity without surcharging. Pipes colored blue indicate pipes that are close to but
not exceeding the capacity standard. Although the color coding identifies most of the
problem areas, some surcharging may occur in adjacent mains upstream from the
identified problem areas due to backwater effects, as was the case for the pipe in NE
Sunset Boulevard to the east of Field Avenue NE (between MH 5303219 and 5303218).
In addition to the color coded plan view, two profile views have been included in this
report to demonstrate the extent of the surcharging before the downstream
improvements. Based on flows from the ultimate expanded UGB, Figure 24A shows
the maximum hydraulic grade line (HGL) in Field Avenue NE, and Figure 24B shows
the maximum HGL in NE Sunset Boulevard. Both profiles have sections where the
maximum HGL is above the manhole rims, indicating that the manholes would be
overtopping, and the side sewers would be backing up.
The Ultimate Stonegate II Model analysis including areas outside the UGB (before
downstream improvements) indicated capacity issues for the Sunset Interceptor in the
manholes east of Duvall Avenue NE to Field Avenue NE. Significant surcharging
occurred upstream from MH 5303216. The pipes downstream from MH 5303216 to
MH 5303090 were upsized during the NE Sunset Boulevard/Duvall Avenue NE
Intersection Improvements and do not appear to have any problems accommodating the
Stonegate 11 Lift Station design discharge. The analysis indicated capacity issues for a
portion of the existing pipe within NE Sunset Boulevard between Union Avenue NE
and Anacortes Avenue NE. Moderate surcharging was shown between MH 5303101 and
MH 5303098. Results of this analysis were compared to those of the Sunset Interceptor
Phase 3 Preliminary Engineering Study Ultimate (2030) Analysis. Capacity issues of
similar magnitude were evident in the same locations as the previous analysis.
City of Renton
K01thmill
2.4 Stonegate 11 Alternatives Analysis Report
tR E N T O N CHAPTER 2— HYDRAULIC ANALYSIS
The majority of the pipes in the Field Avenue Interceptor appear to have capacity
' issues. Significant surcharging is shown between MH 5303218 and MH 5303225,
indicating the existing 8-inch diameter pipe has inadequate capacity to receive the
design discharge rates from the lift station.
' In order to address the capacity issues within Field Avenue NE and NE Sunset
Boulevard, the following gravity main improvements were modeled: The model results
' from upsizing these pipes are shown on Figures 24C and 24D.
Within Field Avenue NE
' • Upsize existing 8-inch pipe to a 12-inch interceptor between MH 5303221 and
5303228.
• Upsize existing 8-inch pipe to a 15-inch interceptor between MH 5303218 and
5303221.
Within NE Sunset Boulevard
• Upsize existing 8-inch pipe to a 12-inch interceptor between MH 5303218 and
MH 5303219.
' • Upsize existing 8-inch pipe to a 15-inch interceptor between MH 5303216 and
MH 5303218.
• Upsize existing 12-inch pipe and 15-inch pipe to an 18-inch interceptor between
Union Avenue NE (MH 5303185) and Whitman Court (MH 5303099).
• Upsize existing 12-inch pipe to a 15-inch interceptor between Whitman Court
NE (MH 5303099) and Anacortes Avenue NE (MH 5303090).
Additional capacity issues were identified in the gravity main immediately upstream of
the Stonegate II Lift Station, to the west in NE 26`h Street for the ultimate flow of 775
gpm. Upsizing the existing pipe from MH 5303326 to MH 5303327 from 8-inch to 12-
inch diameter and increasing the size of the new pipe from MH 5303327 to the new
Stonegate Lift Station to 12-inch pipe would alleviate these future capacity issues.
These mains have adequate capacity to convey flows from the anticipated developments
within the current UGB. However, when the UGB is expanded, the additional service
area triggers the capacity issues. Therefore, the line from NE 26`h Street into the new
lift station would not need to be replaced until that time. For the purposes of this
report, we have assumed that this line will be replaced at a later date when more
information is known regarding build -out and ultimate flows.
Rot H I I I City of Renton
I Stonegate 11 Alternatives Analysis Report 2.5
CHAPTER 2— HYDRAULIC ANALYSIS R E N T O N
TOTAL DYNAMIC HEAD COMPUTATIONS
Using the design flow rates of 425 gpm and 775 gpm identified in the Model Analysis
section above, total dynamic head (TDH) computations were performed to determine
preliminary sizes for the lift station pumps. The TDH is composed of the static
elevation difference and the dynamic head losses from friction, including pipe friction
head losses, minor losses within the system (pumps/valves/fittings/etc.), and velocity
head loss.
The computations were performed assuming a Hazen Williams roughness "C" Value of
140 for PVC pipe, to simulate aged conditions within the system. New PVC pipe may
exhibit a C-Value closer to 150, which would decrease the pipe friction loss by
approximately 4.5 feet for the proposed force main. Based on this assumption, the
pumps may deliver a slightly higher output than the interim design pumping rate of 425
gpm. However, the system is expected to age somewhat before the Ultimate pumping
rate of 775 gpm will be utilized, such that the roughness of the pipe should be closer to
the assumed value.
Based on the initial computations and assuming the preferred conveyance alternative
described in the Route Alternatives section below, the TDH would be approximately
150 feet at 425 gpm and 180 feet at 775 gpm. These TDH values are relatively high
due to the 135 feet of static head that must be overcome to pump to Field Avenue NE.
These design pumping conditions could apply to a single pump in operation or a
combination of two pumps in parallel.
The TDH values herein are approximate values based upon the preliminary layout of
the force main system. The calculations should be refined and verified during the
design phase prior to final selection of the pumps.
HYDRAULIC JUMP ANALYSIS
The proposed gravity system within Field Avenue NE was analyzed to determine the
likelihood of a hydraulic jump forming under the projected flow rates along with the
potential impacts associated with a hydraulic jump. The hydraulic modeling program
F1owMaster by Bentley Systems, Inc. was used for portions of the analysis. Design
discharge rates of 425 gpm and 775 gpm were assumed to enter the system in Field
Avenue NE at MH 5303229 based on the methodology described in the Model Analysis
section above.
The gravity main within the system was assumed to be entirely composed of PVC pipe.
The resultant model demonstrated supercritical or critical flow under the design
conditions when using a default Manning's roughness coefficient of 0.010. The system
was sensitive to changes in the pipe roughness value, with values of 0.011 or 0.012
resulting in a hydraulic jump in the system where the flow profile was shown to
transition from super -critical to sub -critical flow. For the 425 gpm or 775 gpm
City of Renton RothHill
2.6 Stonegate 11 Alternatives Analysis Report %.__1
R E N T O N CHAPTER 2- HYDRAULIC ANALYSIS
discharge cases, a pipe roughness value of 0.012 resulted in a hydraulic jump in the
' vicinity of MH 5303228 or MH 5303225 (possibly both depending upon the flow rate).
The estimated magnitude of the hydraulic jump could reach up to approximately 0.4
feet during the higher pumping discharge conditions, which would likely occur either
' within the manholes mentioned above or the mouth of a connected pipe. The jump
would likely be considered either a weak jump or an oscillating jump (lower magnitude
than a steady jump or a strong jump). Under lower flow conditions, the jump would be
expected to be insignificant (considered an "undular" jump). It should be noted that the
flow conditions within the piping in the north end of Field Avenue NE would mostly be
' in the "transition zone," where actual hydraulic jumps are sensitive to numerous
variables, and are highly unpredictable.
' The estimated magnitude of the potential hydraulic jumps does not appear to be cause
for significant additional analysis of the system from a hydraulic capacity standpoint.
However, the jumps could cause moderate turbulence and result in hydrogen sulfide gas
' release, which could damage un-lined concrete manholes and create odor issues. The
turbulence should not be as significant as a drop connection. Additional turbulence
will likely occur at the discharge of the force main in MH 5303229. Therefore, we
recommend installing a protective coating in Manholes 5303229, 5303228, and
5303225 to combat potential corrosion from hydrogen sulfide gas release. Some odor
may be released at the discharge point and at the hydraulic jump locations, which could
' be mitigated with chemical treatment at the lift station if necessary.
RothHill City of Renton
' %--- Stonegate 11 Alternatives Analysis Report 2.7
CHAPTER 2— HYDRAULIC ANALYSIS R E N T O N '
THIS PAGE INTENTIONALLY BLANK
City of Renton RothHill I
2.8 Stonegate 11 Alternatives Analysis Report
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FIGURE 2-1
STONEGATE/SUMMERWIND `,11Y Off,
Legend SERVICE AREA
Properties Currently Served by Stonegate LS
Properties Currently Served by Summerwind LS
Ultimate Stonegate Service Area outside Current UGB
0 New Development Served by Stonegate LS
Projected Stonegate Service Area within Current UGB Rothffill
Urban Growth Boundary
Park/Open Space
I vI
FIGURE 2-2
STONEGATE SERVICE AREA
PROJECTED PARCEL SUBDIVISIONS
Legend
Parcel Subdivisions Outside UGA
Parcel Subdivisions Within UGA
.._.._.i Urban Growth Boundary
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Roth Hill Engineering Partners, LLC _
"JL AS NOTED CITY 0E
2600 116th Avenue NE k100 RWEI R E N TO N
• Bellevue, M,,hinglm 98004 `..o
R o t h H i I I °� DATUM
Tel Planning/Building/Public Works Dept.
Fan 425869.1190 N0. REVISION BY DATE APPR
STONEGATE
LIFT STATION REPLACEMENT
LIFT STATION SITE PLAN
Cs
10 a 10 20
SCALE IN FEET
Roth Hill Engineering Partners, LLC _
wL 2600 1161h AAS NOTED :-.n CITY OF
Avenue NE p700 �
Ro_t/h /H_i I Be le ue. Yla hington 98004 u R E N T O N
iN 426869.9uT8 0.�.. TVW
V-!za DATUM
Fan d25869.7790 Planning/Budding/Public Works Dept.
NO. REVISION BY DATE APPR
STONEGATE
LIFT STATION REPLACEMENT
LANDSCAPING PLAN
9/12/2008
m
- r
)FLxF
"HECK VALVE: FLxFL
SPECS. (TYP. OF 2)
8' GATE VALVEFLxFL (TYP OF 2)
8" ROMAC
FL. CPLG.
ADAPT
SCH- 80 PVC
SUMP PUMP
DISCHARGE PIPE
8" DI PIPE:
_
_ SUMP PUMP
FLxPE LF AS
(PER SPECS)
i
REO'D.
8" BEND:
FL.FL
Roth Hill Engineering
Partners, LLC
25W 116111 Avenue NE #100
R o_th/H i I I
Washingtm 98004
Te 425.869.9448
S v
Fax 425.869.1190
SUMP PUMP
1-1/2" SCH. 80 PVC (PER SPECS)
SUMP PUMP SUMP W/
DISCHARGE PIPE W/ B CRATE 8 DI 90- BEND:FL.FL
DOUBLE CHECK VALVE
/8' 01 PIPE:FL.PE LF AS
REO'D- (TYP. OF 2)
JA PRESSURE GAUGE
ASSY. (TYP. OF 2)
8" ROMAC STYLE 501 FLEX\
CPLG. W/ ROMAC 611 SERIES
RESTRAINT SYSTEM (TYP. OF 2)
-8 RETAINER GLAND
CAST IN CONCRETE
(TYP. OF 2)
-2'0 TYPE 304
SCH.40 S.S. GUIDE
RAILS (TYP.)
4'x6' ALUMINUM DOUBLE DOOR
ACCESS BECO MODEL JD-3AL
WITH RECESSED PADLOCK HASP.
ADEOUATF FOR 1-20 LOADING,
OFFSET FOR 7- LADDER
CLEARANCE.
8" DI PIPE: PExPE� I 8" ROMAC FL.
LF AS REO'D. CPLG. ADAPT.
(TYP. OF 2) ( (TYP. OF 3)
8 CHECK VALVE:
FL.FI PER SPECS.
(TYP. OF 2) i 8' GATE VALVE
FL.FL (TYP OF 3) �—
I
t
EXTRA HEAVY DUTY
t ALUMINUM ACCESS
( LADDER A/ BILCO
LADDER UP SAFETY
POST MODEL 4
I
t
PUMP & PIPING PLAN VIEW
24' 18' 1�2' 0- 0' 3' '
4"45' 8" DI PIPE: 8- ROMA(
BEND: �FLxPE LF AS FL. CPLC.
FLxFL I HLU U. ADAPT
8 TEE: `-8"x a" WYE: FLxFL 8" METER
FL.FL
ADJUSTABLE. PIPE
STAND (TYP. OF 3)
SECTION B-e
12- 6' 0 12 3'
SCALE. 3/4'mF W
L►B
EXTRA HEAVY DUTY
ALUMINUM ACCESS
LADDER 1b/ BILCO
LADDER UP SAFETY
POST MODEL 4
VALVE VAULT VAULT NO. 8114 nTM LA
8" DI FORCE MAIN
314.33
PRE -CAST CONCRETE
VALVE VAULT UTILITY
VAULT NO. 814-LA
8" DI PIPE:FLxPE
LF AS REO'D.
8' ROMAC FL
CPLC. ADAPT
8"x 8" TEE:FL.FL
8"x 4" W7EFLxFL
8" ROMAC FL.
CPLG. ADAPT
4'x6' ALUMINUM DOUBLE DOOR ACCESS
HATCH, LW PRODUCTS MODEL HD-3E
WITH HANDRAIL TO ASSIST ENTRY
/ I \
71
-
-—320.0'
PIPE PENETRATION
(TYP) (SEE NOTE
i5 THIS SHL)
FRP LADDER
//- CONC.
/ SUPPORT
/
FROM VALVE
315.0' VAULT
TO VALu<
-
3M.4' (FORCE MAIN IE)
VAULT
FIXED FRP LADDER
PER DETAIL
I Vh'- Ph'x VA" S.S.
GRATING (PER
L BRACE W/ >b" S.S.
`STRUCTURAL
I - U-BOLT (TYP)
\PLANS)
(OVERFLOW WIER) 310.9'-
2'0 TYPE
304 SCFL40
S.S. GUIDE
RAILS
TYPE 304
S.S. SLING
I 1-1/2' SCH. 80
RETRACTABLE FRP
— CHAIN (TYP.)
I PVC SUMP PUMP
LADDER PER DETAIL
20- __ DISCHARGE PIPE
ANCHOR BOLTS PER —
I 8'DI SPOOL
MANUFACTURER (TYP)
I LENGTH AS
REO'D.
3-STD- MANHOLE
STEPS ® 12- O.C.
_8'DI ADAPT: FLxMJ
4-INCH SUBMERSIBLE PUMPS
-
I 8"x4" RED.: FL.FL
(2-REO'D.) NOTE: FITTINGS
AND VALVES SHOWN SHALL
BE THE SAME FOR BOTH
PUMP DISCHARGE MAINS.
_
.. ..
60'
60
.9
-7.08-
302.5'
jI l
5._ rjI
�4
301.0'
— 20.76"— —16. 7---
8'-0" -
SECTION A -A
24" 18" 12- 6' 0 1' 2' 3' 4'
SCALE. 14'=1'0' NOTES:
1 ALL DUCTILE IRON PIPING AND FITTINGS SHALL BE EPDXY
LINED CLASS 52 EXCEPT FOR FLANGED SPOOLS OR WHERE
OTHERWISE NOTED ON DRAWINGS. ALL DI PIPING AND FITTINGS
WITHIN WET WELL SHALL HAVE EPDXY COATED EXTERIOR.
2. BACKFILL AROUND STRUCTURES AND WITHIN 5' OF STRUCTURES
SHALL BE SELECT MATERIAL COMPACTED TO 95% MDO-
3. ALL CONCRETE SUPPORTS TO BE FORMED.
4. ALL 4" & LARGER PVC PIPE PENETRATIONS SHALL USE
KOR-N-SEAL BOOTS OR SAND COLLARS- ALL OTHER
PENETRATIONS SHALL BE SEALED INSIDE AND OUTSIDE WITH
A SAND AND PORTLAND CEMENT CONCRETE MORTAR TO
FORM A WATERTIGHT SEAL.
5. ALL MJ JOINT FITTINGS SHALL BE RESTRAINED-/MEGALUGS.
6. WET WELL & VALVE VAULT SHALL BE COATED PER
SPECIFICATIONS.
7. CORE DRILL ELECTRICAL & TELEMETRY PENETRATIONS IN
FIELD AS REQUIRED.
I
GRATING PERK
-TURAL PLANS
0
ABLE FRP
o
12-TIP,
2
1-STD. MANHOLE—,
STEPS P9 12- O.C.
RETRACTABLE LADDER DETAIL
ie 12- - o r 2 a
SCALE: 112/— 0"
Roth Hill Engineering Partners, LLC
2600 1161h Avenue NE #100
R o t h H i I I Bellevue. 9944nglm9800a
/ Tel a25869.9aa8
V Fax 425.869.1190
WET WELL VENT DETAIL
12" 0 2 l'
SrAL- 111 -:.o-
a
CITY OF RENTON
STONEGATE
LIFT STATION REPLACEMENT
I
GENERAL SCOPE OF WORK
3
Roth Hill Engineering Partners, LLC
2600 116th Avenue NE #100
Bellevue, Washington 98004
RothHiell Tel425.869.9448
Fax 425.869.1190
CITY OF RENTON
CITY COUNCIL
MAYOR
MARCIE PALMER, PRESIDENT
DENIS LAW
RANDY CORMAN, PRESIDENT PRO TEM
CHIEF ADMINISTRATIVE OFFICER
DON PERSSON
JAY COVINGTON
TERRY BRIERE
PLANNING/BUILDING/PUBLIC
3 KING PARKER
WORKS ADMINISTRATOR
GREG TAYLOR
GREGG ZIMMERMAN
RICH ZWICKER
UTILITY SYSTEMS DIRECTOR
LYS HORNSBY
CITY OF RENTON
1055 SOUTH GRADY WAY
RENTON, WASHINGTON 98055
CONTACT PERSONNEL
DAVE CHRISTENSEN, PE WASTEWATER UTILITY (425)430-7212
MANAGER
SEATTLE PUBLIC UTILITIES
PUGET SOUND ENERGY
COMCAST CABLE
OWEST
360 NETWORKS
LEVEL 3
TIME WARNER
XO COMMUNICATIONS
EMERGENCY 911
ONE CALL 1-800-424-5555
PROJECT
LOCATION
_IT�Ro sNoavol
VICINITY MAP
LEGEND
EXISTING
PROPOSED
_SSMH
SAN.SEWER MANHOLE
-- — — -- SANITARY SEWER
0 SM
CATCH BASIN (MH)
O/ SANITARY SEWER MANHOLE
U CB
CATCH BASIN
................. I SANITARY SEWER FORCE MAIN
{*UP
UTILITY POLE
�Y LS
LIGHT STANDARD
KEYSTONE RETAINING WALL
O GP
GUY POLE
SECURITY FENCE
O UB
UTIUTY BOX OR VAULT
_______ PERMANENT SEWER EASEMENT
RN wV
WATER VALVE
SURFACING
MON
MONUMENT
GRAVEL
❑ WM
WATER METER
- -
3 ASPHALT SURFACING
R FH
FIRE HYDRANT
-''j
a t.19
MAIL BOX
TREE OR SHRUB
_2 NS
ROAD SIGN
❑ SG
SIGN
,=:c 1D
ROCKERY
SAN.SEWER MAIN, SIDE SEWER
-----W------
WATER MAIN
fl
WATER SERVICE, METER
-----SO-----
STORM DRAIN LINE
I", cc
CONCRETE CULVERT
---G---
GAS MAIN
------ T-------
UNDERGROUND TELECOM LINE
---P---
UNDERGROUND POWER LINE
EDGE OF ASPHALT CONC.
PAVEMENT (ACP)
FLOWLINE
-- -- ---
ROAD CENTERLINE
RIGHT OF WAY
------70----
CONTOUR ELEVATION
-
-,
EDGE OF TREES/BRUSH
CONIFER TREE
tr'
DECIDUOUS TREE
SHEET INDEX
SHT.NO-
DESCRIPTION
C1
COVER SHEET
C2
SHEET INDEX & LEGEND
C3
EXISTING SITE / TESC / DEMOLITION PLAN
C4
SEWER PLAN AND PROFILE
C5
LIFT STATION SITE PLAN
C6
GRADING / DRAINAGE PLAN
C7
SITE / TESC DETAILS
C8
WET / DRY WELL PLAN & ELEVATIONS
C9
PUMP & PIPING PLAN, SECTIONS AND DETAILS
C10
MISC. WET / DRY WELL DETAILS
L1
LANDSCAPING PLAN
Roth Hill Engineering Partners, .LLC
26W 11691 Avenue NE #100
R o_t/h/H_i I I ae14we 99448
V Fax 425869.1190
14
JA5
12
FLAGGED EDGE OF WETLANDAA2 30' I 30'
TRACT A
LQQ:
Q R
KEYSTONE WALL
-------------
1 `!1 Q/r� CHAIN LINK FENCE'-.
NEW TRAI; SFORMER
GENERATOR
VALVE',,
VAULT
,WET. WELL
LIFT
STATION
(30'x2fl
ONE-HOUR
YER
STORAGE
LOF I
ROPOSFD 8"
CRA' TY lvlAiN
c,
:Ji 5
'S1 .0NEGATE
j
PROPOSED
FORCE MAIN eL 4'VADE'ARBOR
'r
WTH,-STONEGATE
OFT WELL SIGN -
ELECTRICAL "CE 14'iAZ—AR66�r T*AE
ON TROL6
CL 4
6 FIR,`.,;* I
Pl
6 CE V;
-/'A
---------------- ------ -----
EXISTI�� G
— — — — - — — — — — - — - - - - - - - - - - - - - - - - - - - - - - - - - - - -
SS .FLU.
TQ 2'TALL LAUREL CONIC
2'TALL LAUF
DRIVE
Roth Hill Engineering Partners, LLC
26M 116W Avenue NE #100
EWIevue. Washrglon 98004
RothHill Tel 425.869.9448
Fax 425 869.1190
r
NE 26TH STREET
45'
NO. I REVISION
AS NOTED
RWB
DSH
BY DATE APPR
m) CITY OF
-AN N. RENTON
Planning/Building/Public Works Dept.
STONEGATE
LIFT STATION REPLACEMENT
SEWER PLAN AND PROFILE
9/12/20081
11 _0
3'x5' ALUMINUM
FRP LADDER
DOUBLE DOOR- FRP LADDER RETRACTABLE LADDER FIND FRP
PER DETAIL
5' ACCESS HATCH PER DETAIL, SHT.10
LADDER
98.8'
�
} I
4
1 12
___
_
___8
CHAIN GATE
,r
AIN, GATE
SUMP
2% MIN-
r
7t
K
h
i.
=
�
O
¢
d
i
r
STILL
_
I :
PER DETAIL.
I FRP GRATING (PER
STRUCTURAL PLANS)
..
FRP
PER
298.8'
2% MIN. SAFETY RAILING (PER Z1 i 12• GRAVITY 2% MIN.
STRUCTURAL PLANS) tt SEWER INLET
PIPE
30-0'
298.1—
WET WELL VENT (PER
DETAIL, SHT.10)
FRP LADDER GUIDE
RAILS
SAFETY RAILING (PER RETRACTABLE
STRUCTURAL PLANS) FRP LADDER �____
FI%EO FRP
LADDER
E�EFE 3
FRP GRATING (PER I 12 GRAVITY
STRUCTURAL PLANS) SEWER INLET
I PIPE
Roth Hill Engineering Partners, LLC
^ 2600 116N Avenue NE #IW 2a- 12' 0 7 6'
Rot/h H_i I I el4.�� �a88'W98°°` 4
/ SCALE IN INCHES /FEET
V Fax 425,869.1190
C8' OUTLET PIPES
TO VALVE VAULT
—4 x8 ALUMINUM
DOUBLE DOOR
ACCESS HATCH
NET WELL VENT
DUCT (PER DETAIL,
SHT.10)
— 320.0'
-8- OUTLET PIPE
TO VALVE VAULT
311.2'
296.5'
8' OUTLET PIPES
TO VALVE VAULT
II
I
1_
3
_______ u_________� ". All
_____________________ _ aL u�c_ ___�______ _____ __I ,
L_________ _Td_ i_i_1_______
� 311.4' (GRAVITY
ELEV.) ,--{�_ _-}____
J i i
306.15' !mac L
�____ -- __ ----------
i
I________________________________
301.0'
_A5
12
IIIYYY FLAGGED EDGE OF WETLAND A2 30'
TRACT, ,,A" .
\~\ l\ tier/IND BUFFfR
r S
6
�1 00 KEYSTONE WALL
-------------
CHAIN LINK FENCE--
NEW TRATSFORMER
Ii, GENERATOR � '
II' I
VAULT
I
�! CONTROL v✓ET vdELL- I
I ` BUILDIt:C
1� l ---,
I
.LIFT
r STATION
r I y ' \ (3O'x2O') $
o � r „� fy ,.LANDSCAPING•<�, S � ..��\~ ,s._, _
NF
STORAGE
LOT I PROPOSED 8, /
'o? owl d .PQ-c GRAVITY MAIN / 1
Zay o .y yTRrACCTI�
., PROPOSED 8" / 1 _ / 5 cE _
y FORCE MAIN., /
` - / 4 wID""ARBOR
. ,EX, '8' DIAM -� \ `..� wliN. STONEGATE
WET WELL L SC
✓�.N - - E.
ryIy ELECTRICAL. •`/ 14 TALL IAt2B0RNtA: I
�i •• CON TROTS�,E L•°IC-( !r IY
P6 f 1
6"FIR 3: r..__ �6
r � / 6 CE • -WE
p� I l%�� •< •ti= P� 414.
� rho"
x
s «
-- -- r-' I
EXISTIy. tN
----------�------ I
e
f Rs s
s
P o' 2' TALL LAUREL CONIC 2 TALL LAURLL"
DRIVE
'r
NE 26TH STREET
Roth Hill Engineering Partners, LLC
^ - 2600 1161h Avenue NE #100
i I I Bel�we. Washirgr�
RothHTel d25.869.9448
%% Fax 425,869.1190
NO.
19&�'
Pin
20 0 20 40
SCALE IN FEET
WJL
RWB
Dsm
BY I DATE II DATE I APPR�'^am
AS NOTED
�� DATUM
TEMPORARY EROSION AND SEDIMENTATION CONTROL NOTES
(1) Approval of this temporary erosion and sedimentation control (TESC) plan does not
constitute an approval of permanent road or drainage design (e.gsize and location of
roads, pipes, restrictors, channels, retention facilities, utilities, etc.)
(2) The implementation of these TESC plans and the construction. maintenance,
replacement, and upgrading of these TESC facilities is the responsibility of the
applicantlTESC supervisor until all construction is approved.
(3) The boundaries of the clearing limits shown on this plan shall be clearly flagged by a
continuous length of survey tape (or fencing. if required) prior to construction. During
the construction period, no disturbance beyond the clearing limits shall be permitted.
The clearing limits shall be maintained by the applicanYTESC supervisor for the duration
of construction.
(4) The TESC facilities shown on this plan must be constructed prior to or in conjunction
with all clearing and grading so as to ensure that the transport of sediment to surface
waters, drainage systems, and adjacent properties is minimized.
(5) The TESC facilities shown on this plan are the minimum requirements for anticipated
site conditions. During the construction period. these TESC facilities shall be upgraded
as needed for unexpected storm events and modified to account for changing site
conditions (e.g., additional sump pumps, relocation of ditches and silt fences, etc.).
(6) The TESC facilities shall be inspected daily by the applicanl/TESC supervisor and
maintained to ensure proper functioning. Written records shall be kept of weekly
reviews of the TESC facilities during the wet season (Oct. 1 to March 31) and of
monthly reviews during the dry season (April 1 to Sept. 30).
(7) Any areas of exposed soils, including roadway embankments, that will not be disturbed
for two days during the wet season or seven days during the dry season shall be
immediately stabilized with the approved TESC methods (e.g., seeding, mulching,
plastic covering, etc .)-
(8) Any area needing TESC measures, not requiring immediate attention• shall be addresses
within fifteen (15) days-
(9) The TESC facilities on inactive sites shall be inspected and maintained a minimum of
once a month or within 48 hours following a storm event.
(10) At no time shall more than one (1) foot of sediment be allowed to accumulate within
a catch basin. All catch basins and conveyance lines shall be cleaned prior to paving.
The cleaning operation shall not flush sediment -laden water into the downstream
system-
(11) Stabilized construction entrances and roads shall be installed at the beginning of
construction and maintained for the duration of the project. Additional measures, such
as wash pads, may be required to ensure that all paved areas are kept clean for the
duration of the project.
(12) Any permanent retention/detention facility used as a temporary settling basin shall be
modified with the necessary erosion control measures and shall provide adequate
storage capacity. If the permanent facility is to function ultimately as an infiltration
system. the temporary facility must be graded so that the bottom and sides are at least
one foot above the final grade of the permanent facility.
(13) Where straw mulch for temporary erosion control is required, it shall be applied at a
minimum thickness.
CITY OF
.� RENTON
Planning/Building/Public Works Dept.
STONEGATE
LIFT STATION REPLACEMENT
TESC PLAN AND NOTES
9/12/20081
[feet]
190600.0
190400.0
190200.0
190000.0
189800.0
189600.0
I
I
NE 24TH S I
1
189400.0 /
189200.0 ` r J
189000.0 1 1
f
188800.0 -
it
188600.0 N E 20TH ST; ��
188400.0 �! w I MH #5303228
f
188200.0 y W MH #5303225' I 1
� > w r `
z 1
188000.0 - / J
W
z Q
187800.0 _ _ w MH #5303219
NE 17TH ST ` a � lit.
187600.0 - CO) MH #5303221 _
187400.0 `r W � Z 1 V 00-10,
MH #5303218
I
187200.0 > z J� MH #5303216
l 1
187000.0 � v�5�
z
186800.0 UJ
MH #5303185 a MH #5303090
186600.0
186400.0 I M #5303099 =
1311000.0 1311500.0 1312000.0 1312500.0 1313000.0 1313500.0 1314000.0
I
■ 1.20
<
■ 1.00
1.20
■ 0.80
1.00
0.60
0.80
<
0.60
1
1314500.0 1315000.0 1315500.0
MH #5303326 MH #5303327
1
NE 26TH
STONEGATE II
LIFT STATION
I
CONCEPTUAL
STONEGATE II
FORCE MAIN
1 '
�r
e
i000.0 1316500.0 1317000.0 1317500.0
[feet]
Figure 2-3
Projected Ultimate Capacity Issues
Downstream of Stonegate 11
Discharge 1.052 1.051 1.050 1.232 1.467 1.708 1.731 cfs
p'P
[feet]
460.0
455.0
450.0
445.0
440.0
435.0
430.0
425.0
420.0
415.0
410.0
405.0
0.0
100.0
Ground Lev.
rn
rn
`-
o
Invert lev.
O
o°19t
cM
Length
88.39
Diameter
0.67
Slope o/oo
3.51
200.0 300.0 400.0
500.0
600.0
700.0
1:0
U)
O
rn
u?
N_
_U)
M
�n
M
cD
v
v
291.58
243.51
161.27
0.67
0.67
0.67
4.12
4.11
4.15
800.0 900.0
•
CO
v coo.
N
O
V:
CO
N
0000
CO N
v
v
85.52
82.12
0.67
0.67
4.21
29.96
1000.0 1100.0 1200.0 1300.0
[feet]
[m]
[m]
371.75 [m]
0.67 [m]
113.14
Figure 24A
Field Avenue NE
Ultimate Flows (before improvements)
Discharge
3.638
13.6271
3.625
1 3.518
1 3.271
1 3.269
13.262
1 3.261 13.236
1
112.06412.065
2.065
1 1.588
1.571
1.550
1.551
1 1.545
10.432
10.432
cfs
q4' pp 00 pp'`
'� '� '� '�
0°� 00
0� 0�
0� �� �" �`l' ��` �p
°� O
�o
' O
1
'�
O O
'� N
n,^
C`I 00
O O
O O
O ��`"r R D� R
�O NO
pp
O� Op 00 00 00 00 Op 00 „� "� Op 00 00 00 Op 00� 00� 00� Opp 00��
[feet] c�`� �'3 �'S �'3 hp h0 h0
�O
h0 hp
h h �p h0 hp h0
�� hp
hp h0
�`�
4,
412.0
410.0
408.0
406.0
404.0
402.0
400.0
398.0
396.0
394.0
392.0
390.0
388.0
386.0
384.0
382.0
380.0
Ground Lev
Invert lev.
Length
Diameter
Slope o/oo
0.0 200.0 400.0 600.0 800.0 1000.0 1200.0 1400.0
o (a 0Mo c` i o
M M (o M CM M
� C9 N O 00 00
� 00 Cl) co co 00
CO M M M M M
131.90 153.05 207.19 137.20 236.11
1.25 1.25 1.25 1.00 1.00 1.00
7.88 4.17 4.64 4.34 7.29 8.89
Cl? O7 �
It � M
O O �
co 0)0
O O O
M M Cl)
154.78
1.25 1.00 1.25
8.42 11.63 6.80
1600.0
1:0
N
N
O
co
09
O
Cl)
249.18
1.25 1.25
26.59 4.82
1800.0
2000.0
2200.0
2400.0
2600.0
2800.0
3000.0 3200.0
[feet]
It
Cn
O0
M
N
CD ((P
� CM
,It
O
0o
O
0
0
0 0
0 [ml
N
0p
�
O
0 CD
� tt
OOP COP [m]
CO
co
NT
It 'IT
289.50
171.25
248.70
218.60
130.34
152.21 120.19 [m]
1.25
1.25
1.25
0.67
0.67
0.67 0.67 0.67 [m]
5.08
11.21
12.46
3.93
3.76
3.22 6.49 4.04
Figure 2-4B
NE Sunset Boulevard
Ultimate Flows (before improvements)
Discharge 1.639 1.816 1.794 1.759 1.751 1.747 1.732 cfs
[feet]
460.0 - - - -
I I
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Figure 24C
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NE Sunset Boulevard
Ultimate Flo"s (post impro-ements)
Chapter 3
ROUTE ALTERNATIVES
This section of the Alternatives Analysis Report for the Stonegate II project evaluated
alternatives associated with five different sewer conveyance pipelines within the
project area. The conveyance pipelines consisted of the gravity sewer line connecting
the Summerwind and Stonegate developments, the proposed force main from the new
Stonegate II Lift Station to the existing system, the Field Avenue Interceptor, the
Sunset Interceptor, and potential gravity service alternatives to serve the existing
properties bordering 147'h Avenue SE and SE 102°d Street. Each of these pipelines
along with their respective route and construction method alternatives are discussed in
further detail below. Representations of each of the pipelines and their alternatives can
be found in Figure 3-1 through Figure 3-9.
Summerwind Gravity Sewer Alternative
The Summerwind Gravity Sewer is a proposed sewer line that is required to connect the
existing Summerwind development with the existing sewer system serving the
Stonegate development. The route for this proposed gravity sewer line was pre-
determined based on the location of the existing Summerwind Lift Station and the end
of the Stonegate gravity sewer system. The proposed route will begin at the existing
Summerwind Lift Station on NE 23`d Court as shown in Figure 3-1 and will flow to the
northeast to the existing Stonegate gravity sewer system, which terminates on NE 24'h
Court at MH 5303317. Based on the hydraulic analysis discussed in the previous
section, the proposed gravity sewer between the Summerwind and Stonegate
developments will need to be 8 inches in diameter and will be approximately 245 feet
long.
The proposed gravity sewer line will need to be installed in an existing utility easement
' across the property at 5305 NE 241h Court. The 4-inch diameter force main from the
existing Stonegate Lift Station is already installed within the easement and would need
to remain in service during construction. The
easement issues are discussed in further detail
later in the report.
Although the proposed route for the
Summerwind gravity sewer was pre -determined,
a couple of alternatives with regard to potential
construction method for installing the proposed
sewer line were evaluated. As seen in the
adjacent photo, the new main will need to be
City of Renton
RothHill
%- Stonegate 11 Alternatives Analysis Report 3.1
CHAPTER 3— ROUTE ANALYSIS R E N T O N
constructed through an existing easement and side yard for the property at 5305 NE 24`h
Court. Other utilities within the easement, as indicated by the junction boxes in the
photo, will complicate construction. The proposed sewer will terminate at the manhole
shown on the bottom of the picture.
Based on our research and discussions with the Geotechnical subconsultant, two
construction methods for the installation of the proposed gravity sewer line were
reviewed. The first method focused on conventional open trench construction and the
second alternative involved horizontal directional drilling (HDD). The installation of
the proposed gravity sewer using conventional open -trench construction methods may
require that the existing utilities be relocated either temporarily or permanently. The
open -trench method would also have the greatest impact on the existing landscaping.
Given these issues, HDD may be a better alternative for installing the gravity sewer
line. HDD would not disturb the existing landscaping along the route, the route has
very good insertion and termination points, and sufficient fall exists between the lift
station and the receiving manhole that slope constraints associated with HDD should
not adversely affect the installation. Specific geotechnical issues and recommendations
can be found in Chapter 4 and in Appendix A.
Force Main Alternative #1
Each of the alternative force main routes are proposed to convey effluent from the new
Stonegate I1 Lift Station, which is assumed to be near the intersection of 1481h Avenue
SE and NE 261h Street, to the Field Avenue Interceptor at a transition point near NE 19`h
Court. The Force Main Alternative #1 (FM#1) route would begin at the proposed
Stonegate 11 Lift Station and run generally southwest through the existing Stonegate
development to the end of NE 241h Court where it would traverse the same easement
that was discussed above for the Summerwind gravity sewer. FM# 1 would then
continue southeast through the existing Summerwind development along Ilwaco
Avenue NE and NE 20`h Street to the existing Field Avenue Interceptor, discharging
flow at MH 5303229. The total length of FM#1 is approximately 3,195 feet and would
consist of 8-inch diameter PVC pipe. The proposed route for FM#1 is shown in Figure
3-2.
The proposed FM#1 route has several issues. The first issue involves disturbances to
the existing community. Both the existing Stonegate and Summerwind developments
are very clean and would be considered higher -end neighborhoods within the City of
Renton. Construction of the proposed FM#1 would be completed using conventional
open -trench construction and could have a significant impact on the surrounding
community with regard to noise, dust, and traffic impacts. One advantage to the FM#1
route is the minimal amount of on -street parking within either of the existing
developments.
Another issue with the proposed FM#1 route is the existing Class 4 stream, which must
be crossed just west of the proposed Stonegate II Lift Station site. Although the
City of Renton RothHill
3.2 Stonegate 11 Alternatives Analysis Report %__�
RE—N- N
CHAPTER 3 - ROUTE ANALYSIS
existing stream appears to dry up during the
summer, it is a classified stream per the preliminary
wetlands report discussed later in this report. The
other factor, as seen by the adjacent photo, is the
depth of the existing culvert. The existing culvert
appears to be an approximately 24-inch x 36-inch
squashed CMP and is only buried with 2 to 2.5 feet
of cover. This will require the proposed force main
to be installed beneath the existing culvert. If this
section of the force main were installed using
conventional open -trench construction, a significant
amount of dewatering could be required even though the stream appears to dry up in the
summer. The amount of dewatering will depend on the depth of the ground water table
during the summer months when construction occurs. Based on this information and
potential permitting issues, this section of the force main may require installation using
a trenchless method of construction such as a bore and jack method. This will need
further investigation during the design phase of the project once the piezometers have
been installed as part of the geotechnical investigation.
The final issue with FM#1 involves the route between the existing Stonegate and
Summerwind developments. FM#1 would be installed within the same easement as the
Summerwind gravity sewer line discussed previously. If both lines were installed using
the proposed HDD construction method, a 24-inch minimum diameter casing would be
required so that both pipes could be placed in a common casing. Having that large of
an HDD for both pipes could be cost prohibitive for this alternative, but would still be
less expensive than drilling two parallel casings.
Force Main Alternative #2
Force Main Alternative #2 (FM#2) would begin at the proposed Stonegate II Lift
Station and run generally southwest through the existing Stonegate development,
similar to FM#l. However, FM#2 would continue south on Lyons Avenue before
turning southwest onto NE 22"d Court. The
proposed force main would then proceed
through an existing fire access road
connecting the Stonegate and Summerwind
developments before entering the
Summerwind development on NE 20`h Place.
The force main would then continue to the
Field Avenue Interceptor, discharging at MH
5303229. The total length of FM#2 is
approximately 3,455 feet and consists of fl-
inch diameter PVC pipe. The route for the
proposed FM#2 is shown in Figure 3-3.
�-. City of Renton
RothHill
Stonegate 11 Alternatives Analysis Report 3.3
CHAPTER 3— ROUTE ANALYSIS R E N T O N
The proposed route for FM#2 faces similar issues as those associated with FM#1.
Similar to FM#l, the proposed route for FM#2 would be constructed within the existing
Stonegate and Summerwind developments using conventional open -trench construction
and would have similar impacts on the surrounding community. FM#2 would also have
to cross the existing stream just west of the proposed lift station and would have the
same construction issues as was discussed with FM#1. The main advantage to FM#2 is
that the proposed route transitions from the Stonegate development to the Summerwind
development at an existing fire access road (see inset picture on previous page) instead
of the easement route described in FM# 1.
Force Main Alternative #3
The purpose of the proposed route for Force Main Alternative #3 is to minimize the
impact on the established Stonegate and Summerwind communities. To accomplish
this, two alternatives have been developed, Force Main Alternative #3A (FM#3A) and
Force Main Alternative #313 (FM#3B). Each route is discussed in detail below.
Force Main Alternative #3A
FM#3A would begin at the proposed lift station and head due east to the intersection of
NE 261h Street and 1481h Avenue SE before heading south along 148`h Avenue SE to SE
102°d Street where it would turn west. The force main would continue west until it
turns south again on 147`h Avenue SE and proceeds to the extension of NE 20`h Place,
as shown in Figure 3-4, where it would again turn west and continue to the Field
Avenue Interceptor, at MH 5303229. The total length of FM#3A is approximately
3,885 feet and the force main would consist of 8-inch diameter PVC pipe.
The main advantage to FM#3A is that the proposed
route minimizes construction within the Stonegate
and Summerwind developments. The existing
community which borders 1471h Avenue SE is older
than and not as developed as the other communities.
As seen in the adjacent picture, 147`h Avenue SE
does not have any existing sidewalks or curb and
gutter to address and would be less expensive to
restore than the proposed routes for FM#1 and
FM#2. Another advantage to FM#3A is that it also
minimizes the amount of construction occurring on 1481h
north -south connector between the May Valley Road and SR
daily traffic loads.
Avenue SE which is a major
900 and sees considerable
FM#3A also has several disadvantages. The proposed route for FM#3A is largely
within King County versus the City of Renton. This will require County permits to be
obtained for construction within the exiting right-of-way and within any required
easements. The City has a franchise agreement which extends to the east side of 1481h
City of Renton --_ I
3.4 Stonegate 11 Alternatives Analysis Report ROthHill
CHAPTER 3 — ROUTE ANALYSIS
Avenue SE so construction within the existing
road is allowed and obtaining the required County
permits should not be a major obstacle. Another
disadvantage to FM#3A is the need to acquire
several easements along the proposed route. Once
the proposed force main reaches the end of 1471h
Avenue SE and turns west, the proposed route will
traverse at least three properties before reaching
the NE 20'h Place right-of-way and the Field
Avenue Interceptor. While this may appear to be
a considerable disadvantage, the proposed route for the force main, as seen in the
adjacent picture, would be constructed within an existing private road and driveway
and would not permanently impact the current use of the properties. The final
disadvantage to FM#3A is the presence of a City opponent within the existing
community bordering 1471h Avenue SE. The City has had prior dealings with the
resident who may oppose the construction of the force main in 147'h Avenue SE and
could cause delays in the project.
Force Main Alternative #3B
Similar to FM#3A, FM#3B would begin at the proposed lift station and head east to
' 1481h Avenue SE. The proposed FM#3B would then turn south and travel along 148'h
Avenue SE, but would continue past SE 102"d Street until it reached the extension of
NE 201h Place, as shown in Figure 3-5. The force main would then turn west and
traverse several easements until reaching the NE 20`h Place right-of-way and the Field
Avenue Interceptor. Again, this proposed route is designed to minimize the amount of
construction within the Stonegate and Summerwind communities. The proposed
FM#3B route is approximately 3,925 feet long and would consist of 8-inch diameter
PVC pipe.
As with FM#3A, the proposed route for FM#3B
would be constructed in less developed roads
without existing sidewalks and curb and gutter
and would minimize construction impacts on the
higher -end communities. The difference between
FM#3A and FM#3B is that FM#3B has more
proposed force main being construction within
1481h Avenue SE. Additionally, FM#3B will
require one or two more easements to be acquired,
although the route through the additional
easements should have minimal impact on the
surrounding properties.
FM#3B has a couple of advantages when compared to FM#3A. The first advantage to
FM#3B is that it is a clean route and reduces the amount of direction changes in the
_Z City of Renton
RothHill
Stonegate 11 Alternatives Analysis Report 3.5
CHAPTER 3— ROUTE ANALYSIS R E N T O N
force main. Another advantage is that the proposed route should have less impact on
the resident along 1471h Avenue SE who is an opponent to construction within the City
of Renton.
Field Avenue Interceptor Improvements
As part of the analysis for the Sunset Interceptor Phase 3 project, the City of Renton
identified flow issues within the existing sewer interceptor in Duval Avenue NE as a
problem to be addressed in a future project. One of the goals of the Stonegate II
project is to divert the flow generated by the new lift station into the interceptor located
in Sunset Avenue via a new Field Avenue NE Interceptor, thereby alleviating the
capacity issues in the Duval Avenue NE Interceptor. In order to accomplish this goal,
the City will need to upsize the existing sewer line located in Field Avenue NE to
handle to project flows.
The existing Field Avenue NE sewer line was
constructed in 1990 and is comprised of 8-inch
diameter PVC pipe. Based on the hydraulic
analysis, the existing Field Avenue NE sewer line
will need to be upsized to 12-inch diameter pipe
beginning at MH 5303228 and terminating at MH
5303221 (approximately 880 lineal feet) and
upsized to 15-inch diameter pipe from MH
5303221 to MH 5303218 (approximately 90 lineal
feet). The proposed modifications to the existing
Field Avenue NE sewer line can be seen in Figure 3-6.
This report investigated two alternatives for the construction of the new interceptor;
conventional open cutting and trenchless pipe bursting. The existing Field Avenue NE
sewer line appears to range from 5 to 9 feet deep. Construction of the new interceptor
using conventional construction methods would have a significant impact on the road
and the community during construction. Pipe bursting or pipe -reaming would limit the
excavation to the location of the existing manholes and side sewers. Pipe bursting
would break the existing pipe using a mandrel while pipe -reaming would "back -ream"
the existing pipe using a horizontal directional drill. Either method would result in a
new, larger HDPE sewer main being installed within the existing alignment of the
interceptor. Based on the preliminary geotechnical report discussed later in this report,
pipe bursting or pipe reaming of the existing Field Avenue NE sewer line are both
viable options. The final proposed method of constructing the new Field Avenue NE
Interceptor should be determined during Phase II of the geotechnical study based on the
potential risk of heaving the existing road surface.
City of Renton Rot Hill
3.6 Stonegate 11 Alternatives Analysis Report .___
R E N T O N CHAPTER 3— ROUTE ANALYSIS
Sunset Interceptor Improvements
' Based on the results obtained from the hydraulic analysis conducted as part of the
Sunset Interceptor Phase 3 pre -design report and reinforced by the analysis completed
for this report, two sections of the Sunset Interceptor would need to be upsized to
handle the ultimate flow. The first section is between MH 5303185 at Union Avenue
NE and MH 5303090 at Anacortes Avenue NE and the second section is between MH
5303216 just east of Duval Avenue NE and MH 5303219 just east of Field Avenue NE.
These sections of existing sewer main were not replaced as part of the Sunset Phase 3
project completed by the City of Renton earlier this year. The proposed pipe
replacements consist of the installation of approximately 595 feet of 18-inch diameter
PVC or HDPE pipe, 1,290 feet of 15-inch diameter PVC or HDPE pipe, and 120 feet of
12-inch diameter PVC or HDPE pipe. The proposed improvements can be seen in
Figure 3-7.
Even with the increased flow proposed from the new Stonegate II lift station, the pipe
sizes identified in the Sunset Interceptor Phase 3 report are still valid. The two
alternatives related to the upsizing of the existing Sunset Interceptor are still
conventional open -trench construction and pipe bursting. The previous pre -design
report concluded that the sections of existing sewer main in question should be replaced
using pipe bursting technology. This report did not discover any information that
' would change that recommendation. Due to the fact that the Sunset report is over two
years old, a new cost analysis of the two alternative construction methods was prepared
and is presented later in this report.
Proposed Gravity Sewer Service
As part of the Alternatives Analysis Report for the Stonegate 11 Project, the City of
Renton had Roth Hill Engineering look at the potential for providing sewer service to
the properties located between the eastern border of the Stonegate development and
' 148'h Avenue SE. The goal of this analysis was to provide sewer service to the existing
properties without the addition of another sewer lift station.
' Two alternative routes were developed to serve the existing properties by gravity. Each
of the alternatives will require utility easements from various properties. Each of the
route alternatives are discussed below. This report also took a cursory look at the
' potential of serving the area by installing a sewer main running north along 148`h
Avenue SE. However, in order to serve the properties along 147`h Avenue SE via this
route, the depth of the proposed manhole at the intersection of SE 102,d Street and
' 148`' Avenue SE would be approximately 38 feet deep. This depth was deemed
unreasonable and this alternative was removed from further investigation.
RothHIII City of Renton
%___ Stonegate 11 Alternatives Analysis Report 3.7
CHAPTER 3— ROUTE ANALYSIS R E N T O N
Proposed Gravity Sewer Alternative #1
The proposed route for Gravity Sewer Alternative #1, as seen in Figure 3-8, consists of
the installation of approximately 3,400 lineal feet of 8-inch diameter sewer main. The
proposed gravity sewer runs along 148`h and 1471h Avenues and connects to the existing
Stonegate sewer system through various easements to the north of SE 102"d Street.
Based on the King County topographic data, the manholes for Alternative #1 would
range in depth from 7 feet to 24 feet, although this depth may be reduced using 12-inch
diameter pipe at minimum slope.
Proposed Gravity Sewer Alternative #2
The proposed route for Gravity Sewer Alternative #2, as seen in Figure 3-9, consists of
the installation of approximately 3,550 lineal feet of 8-inch diameter sewer main.
Similar to Alternative #1, the route for Alternative #2 runs along 1481h and 147`h
Avenues, but connects to the existing Stonegate sewer system through various
easements to the north of SE 102"d Street. The proposed route for Alternative #2 would
require the bisection of a piece of property located off of 1471h Avenue SE and, as such,
would required coordination with the property owner. It is likely that this alternative
would not be possible without the subdivision of the property in question. This
alternative also requires more sewer installation within the existing right-of-way for
1481h Avenue SE. Based on the King County topographic data, the manholes for
Alternative #2 would range in depth from 6 feet to 13.5 feet.
Both of the gravity sewer alternatives are viable and would provide service to the area
in question. It should be noted that there is also some concern about the potential
service of the properties on the west side of 1481h Avenue SE, south of 102"d Street.
The general topography of the area slopes to the west, away from the proposed sewer
line. Some of these properties may have homes with daylight basements that could
require the sewer to be deeper. Although we have shown the proposed sewer within
148`h Avenue SE at a minimum depth of 7 feet, both route alternatives have significant
fall between the manhole in the intersection of SE 102"d Street and 148`h Avenue SE
and the next manhole to the west. Therefore, the line in 148" Avenue SE could be
lowered to accommodate homes with deeper sewer service requirements. Both
alternatives will require further investigation by the City.
City of Renton Rot Hill
3.8 Stonegate 11 Alternatives Analysis Report
STONEGATE II ROUTE ANALYSIS
FIGURE 3-1
SUMMERWIND GRAVITY LINE
0{
RothHill
■ n-
EXISTING FORCE'MAIN
FROM STONEGATE LS-
TOiSUMMERWINi LS
PROPOSED 8" PVC
FORCE MAIN
SUM ERWIND
LIFT STATION
(TO E REMOVED 7
M SERVICE)
EXISTING FORCE MAIN
-FROM
UMMERWIND LS
I I I E 6 DI S
EXISTING 8"r-
GRAVITY SEWE
SYSTEM"
E
MH#5303229
24
EXISTING '�I
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G�
145TH PL SE (PRIVATE)
TRIBUTARY TO
MAY CREEK
MAY CREEK
STONEGATE
LIFT STATION
NE 26TH ST
It
CULVERTED111
STREAM CROSSING
RENTON
CITY -LIMITS
N STONEGATE II ROUTE ANALYSIS .,
w E FIGURE 3-2
FORCE MAIN ALTERNATIVE #1
S RothHill
/ r MAY CREEK
��,STONEGATE
f LIFT STATION
EXISTING FORCE MAIN_
FROM STONEGATE LS
TO SUMMERWIND LS
_ NE 26TH ST
SUMMERWItND PROPOSED 8" I ��
LIFT STATION PVC FORCE MAIN(TO BE CULVERTED
FROM SER IICEED
t STREAM
CROSSING I
TRIBUTARYTO
MAYCREE
N STONEGATE II ROUTE ANALYSIS
w E FIGURE 3-3
FORCE MAIN ALTERNATIVE #2
S RothHill
EXISTING FORCE MAIN
FROM lS1IUMIMERWIND LS
-ILL /! ( NE 13l�D ISl
EXISTING 8"1GRAVITY.
SEWER -SYSTEM, I
EXISTING FORCE MAIN
FROM STONEGATEIS
TO SUMMERWIND LS
SUMMERWIND
LIFT STATION
(TO ,BE REMOVED
FROM SERVICE) 7
H
61
r
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STONEGATE
LIFT STATION
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I
� 14 TH P (PRIVATE)
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PROPOSED
8=PVC
FORCE MAIN
RENTON
CITY LIMITS -
SE 1JND ST
N STONEGATE II ROUTE ANALYSIS
FIGURE 3-4�,-
W E
FORCE MAIN ALTERNATIVE #3A
S RothHill
EXISTING FORCE MAIN
FROM STONEGATE LS
TO SUMMERWIND LS
SUM ERWIND
LIFT TATION
(TO BE REMOVED
FROM SERVICE) 7
EXISTING FORCE MAIN,
FROM SUMMERWIND LS
EXISTING 8' GRAVITY
SEWER SYSTEM /
MH#530
7lw
.A
NE 24
G�
r MAY CREEK
STONEGATE
LIFT STATION
NE 26TH ST
PROPOSED-
8- PVC L �--
FORCE MAIN
RENTON—
CITY-LIMITS
ZN. cl)
STREAM CROSSING
(JACK & BORE)!t
\
SE (PRIVA'
EASEMENTS RE
TRIBUTARY TO
MAY CREEK
STONEGATE II ROUTE ANALYSIS
FIGURE 3-5
FORCE MAIN ALTERNATIVE #313
v
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:• A
y
RothHill
STONEGATE II ROUTE ANALYSIS `� o
N i cJ 'rti
FIGURE 3-6 '�� +
FIELD AVENUE INTERCEPTOR
IMPROVEMENTS
S RothHill
STONEGATE
LIFT STATION
I'
MH#5303327
III
NE-26TH ST
RIM=328.0
IE=321.01 RIM=325.0
I E=312.9
EI 328 0'0 RIM=327 0
IE=319.0
RIM=346.0
TH T IE=339.0 CO
RIM=369.0
IE=345.0
RIM=359.0
IE=345.6
�.L8.A.
G 02 SE 102ND STI
RIM=360.0
IE=346.7
EI 3478�I I`-
L RIM=355.0
IE=349.0
--�
TRIBUTARY
TO MAY CREEK
RIM=333.0
IE=326.0
MAY CREEK
RIM=343.0
IE=336.0
RIM=346.0
I E=339.0
RIMRIM=362.0
--__
IE=344.12
- RIM=383.0
IE=376.0
RIM=395.0
IE=388.0
RIM=405.0
I E=398.0
RIM=412 0
IE=405.0
STONEGATE II ROUTE ANALYSIS
FIGURE 3-8
PROPOSED GRAVITY SEWER
ALTERNATIVE #1
rf_V.�C
RothHill
STONEGATE
LIFT STATION
I-
MH#5303327
I i I
NE-26TH ST
RIM=325.0
IE=312.7 ;o
co
RIM=338.0 r
IE=331.0
2 TH T RIM 339.0
IE= 30.7
00
RIM=3
IE=34 .3
co
Gi
�-L RIM=359.0 8"
� � O� I\ass SE 102ND STI
RIM=360.0
IE=346.7
2
RIM=355.0
CIE=347.8
L RIM=355.0
IE=349.0
TRIBUTARY
TO MAY CREEK _
RIM=333.0
IE=326.0
MAY CREEK
RIM=361.0
RIM=373.0
IE=366.0
RIM=383.0
IE=376.0
RIM=395.0
IE=388.0
RIM=405.0
IE=398.0
RIM=412 0
IE=405.0
STONEGATE II ROUTE ANALYSIS
FIGURE 3-9
PROPOSED GRAVITY SEWER
ALTERNATIVE #2
RothHill
Chapter 4
GEOTECHNICAL REPORT
As part of the investigation for this analysis and report, HWA GeoSciences Inc. (HWA)
was retained by Roth Hill as a subconsultant to prepare a pre -design geotechnical
feasibility report. Their report, dated July 23, 2007, is included in Appendix A.
The HWA investigation was limited to field reconnaissance and the identification and
review of available existing information. Subsurface field explorations were not
performed. The information contained in the HWA report is incorporated directly into
this report and summarized or elaborated upon as appropriate. The following
information presented in this section is summarized from the HWA report dated July
23, 2007.
' Local Geology
' Geologic information for the project site was obtained from the published geologic map
for the area; Surficial Geologic Map of the King County, Puget Sound Region,
Washington (Troost, et al, 2004). The map indicates the surficial geology of the
' subject parcel consists of Vashon till, a non -stratified and non -sorted mixture of clay,
silt, sand, and gravel. The till was deposited over the advance outwash as a deforming
bed of reworked sediment beneath the glacial ice. It forms a very compact unit due to
' the weight of the over-riding glacier. Cobbles are typically scattered throughout the
till, and boulders are often encountered.
IErosion Hazards
The local soils mapped by the Natural Resources Conservation Service (NCRS) indicate
' the site soils pose only a moderate erosion hazard. The highest potential for erosion
will occur during construction where excavations are required and after the vegetation
has been cleared or pavement removed and the soil is directly exposed to the elements.
However, implementation of appropriate best management practices (BMPs) for
handling of stormwater runoff during construction will largely mitigate adverse effects
' associated with soil erosion on site.
Landslide -Steep Slope Hazards
Typically, landslide hazards are defined as those slope areas with a vertical height of
10 feet or more that are potentially subject to mass earth movement based on a
' combination of geographic, topographic, and hydrologic factors. These include areas
' Rot H i I I City of Renton
Stonegate 11 Alternatives Analysis Report 4.1
CHAPTER 4— GEOTECHNICAL & WETLANDS REPORTS R E N T O N
with slopes steeper than 15% that intersect geologic contacts with relatively permeable
sediment overlying a relatively impermeable sediment or bedrock. These areas may
also contain spring or ground water seeps.
Based on observations performed by HWA, slopes steeper than 15% exist along the
northeastern portion of the site where the ground slopes towards the creek situated
between 147`h Avenue SE and Lyons Avenue NE. From just east of Ilwaco Avenue NE
to the creek, the slope is inclined from 10% to approximately 35%. However, the local
geologic mapping indicates the existing native soils consist of granular, glacial till soils
that are very dense, and typically not subject to global failure or deep-seated rotational
sliding, and as such, the proposed sewer system improvements should have minimal
impacts on site slopes and should not increase the hazard level associated with
occurrences of potential shallow landslides.
Seismic Hazards
Seismic hazards are defined as areas subject to a severe risk of earthquake damage as a
result of seismically -induced ground rupture, liquefaction, and settlement. Ground
rupture is the general term used to characterize an area where fault movement occurs.
The nearest known fault considered to be active by the United States Geological Survey
is located approximately 5 miles north of the subject site. Therefore, damage to
structures on this site caused by rupture along the fault zone is relatively unlikely.
Liquefaction occurs when loose, saturated, and relatively cohesionless soil deposits
temporarily lose strength as a result of earthquake shaking. The site soils identified
locally are not subject to liquefaction except for those soils in the area of creek
crossings. Soils in these areas could be subject to liquefaction. The potential for
liquefaction at the creek crossings can be mitigated by replacing the foundation soils
with properly compacted fill or bypassing the liquefiable soils using foundation support
pipe or jacking a casing.
Ground settlement is associated with areas susceptible to liquefaction and, therefore,
could occur at the creek crossings. Again, proper design of the pipeline foundation in
these areas can mitigate any potential structural damage due to ground settlement.
Groundwater
All force main alignments under consideration will involve one creek crossing. Based
on the research conducted as part of the geotechnical report, alluvial soils and/or
reworked outwash soils are expected within tenths of feet on either side of the creek.
Groundwater should be anticipated at shallow depth within approximately 50 feet of
either side of the creek. Perched seepage may be encountered locally at shallow depths
along the transition between fresh and weathered glacial till as the alignment proceeds
uphill towards the Summerwind development and NE 20`h Street.
City of Renton
RothHill
4.2 Stonegate 11 Alternatives Analysis Report
' R E N T O N CHAPTER 4— GEOTECHNICAL AND WETLANDS REPORT
Groundwater seepage at the creek crossing will likely require dewatering by pumping
' out of a sump within the trench or excavated bore pits. Groundwater seepage
encountered at the transition zone described above may be managed by installing a
perforated drain pipe along the trench bottom as the excavation proceeds uphill. The
collected groundwater seepage will need to be treated and would be conveyed to the
creek crossing and discharged.
Pipe-Bursting/Pipe-Reaming
' As part of the investigation for this report, HWA took a preliminary look at the
feasibility of using pipe -bursting or pipe -reaming for the installation of the new Field
Avenue Interceptor. Pipe -bursting uses a hydraulic or pneumatic head to split the
existing pipe and make space for the new, larger pipe. When completed, the
replacement pipe invert very nearly matches the existing pipe invert. Factors affecting
the use of pipe -bursting in this area include the existing line's proximity to other
' utilities, depth below grade, and condition of the trench backfill surrounding the
existing pipe. Pipe -bursting may cause bulging of the existing roadway if the pipes are
too shallow or the existing fill is dense.
Pipe -reaming involves the fragmentation of the original pipe by "back -reaming" using a
Horizontal Directional Drill. When completed, the replacement pipe invert will be
' lower than the original by about half the difference between the original pipe diameter
and the new pipe diameter. This impact would need to be reviewed during the design
phase of the project to ensure that the lower inverts do not adversely affect the
downstream sewer pipes. The primary advantage of pipe -reaming is that it does not
rely on volumetric distortion to break the pipe and therefore does not cause significant
bulging of the fill or roadway.
Both methods should be investigated further as part of the design phase of the project
I WETLANDS REPORT
' A Technical Memorandum, prepared by ESA Adolfson, dated June 26, 2007, shows the
location of a Class 4 stream, which is a tributary to May Creek (a Class 2 Stream). The
Class 4 stream runs north along the east side of the homes along the east side of Lyons
' Avenue NE. The buffer width for this tributary is 35 feet on both sides of the stream.
Force Main Alternative Routes # 1 and #2 would cross this tributary stream on NE 26'h
Street, within the existing road prism, thus minimizing impacts to the stream since it is
' already contained within a culvert at this location. Alternatives #3A and #313 would
cross this same tributary further south at NE 20`h Place ("in the vicinity of SE 104"'
Street" in the Adolfson memo), but not within a road prism. Construction of the
proposed force main under Alternative #3A or# 3B would likely require a trenchless
method such as boring since the stream is not contained within a culvert.
City of Renton
RothHill
`
Stonegate 11 Alternatives Analysis Report 4.3
CHAPTER 4- GEOTECHNICAL & WETLANDS REPORTS R E N T O N
ESA Adolfson recommends a full survey of the stream be completed, to include
flagging the ordinary high water mark and any other areas of concern, once a preferred ,
pipeline route is selected. This survey and delineation will be necessary for permit
submittals. A copy of ESA Adolfson's Technical Memorandum is included as
Appendix B.
City of Renton I
4.4 Stonegate 11 Alternatives Analysis Report RothHill
Chapter 5
PERMITTING REQUIREMENTS
Depending on the alignment route chosen, the proposed sewer project will require
permits from King County as well as the Washington Department of Fish and Wildlife
(WDFW). While portions of all the route alternatives will be constructed within the
City of Renton, no permits will be required from the City since any pipe improvements
would be a City project. A list of possible permits, estimated permitting fees by
jurisdiction and consultant fees is shown in Table 5-1.
Routes
PermittingTable 5-1
Requirements
Permits Fees =
Roth Hill Fees
Potential Issues -
Summerwind
None
None
None
Gravity Line
............. ................... -..... _.................... ...... ..._._.................
... ... ....................
Alternative #1
1) King County Wastewater
.......... .................. _........ _...................
WTD $450
_.......................................................................................................................
Crosses Class 4 Stream
Treatment Division Approval:
HPA 5650
in road prism. Stream is
No Fee
contained within an
2) WDFW HPA: No Fee
existing culvert at the
...................._..._......................._.._........___.................._..._.........._..._....................._._.............._...............--................._..............._......................._......................................._....................._.__
........_...._........._............
proposed crossing.
_........ _-....................................._.................._............._.._..................
Alternative #2
1) King County Wastewater
WTD 5450
Crosses Class 4 Stream
Treatment Division Approval:
HPA 5650
in road prism. Stream is
No Fee
contained within an
2) WDFW Hydraulic Project
existing culvert at the
Approval (HPA): No Fee
proposed crossing.
Alternative #3A &
_............................... .......-............................. ........... .... .....
1) King County Right -of -Way
...._........................................... _.....
ROW 5450
__....--_..... ............... ......_.................... ................ ..................... --- ........... .
Crosses Class 4 Stream
3B
Permit: S 190
KC Grade 5850
by boring
2) King County Grading
WTD 5450
Permit: S 1500 — 2500
(estimated)
HPA 5650
3) King County Wastewater
Treatment Division Approval:
No fee,
4) WDFW HPA: No fee
- - - - - ----- - - -- - - --- -- ---------- -
' Rot H 111 City of Renton
Stonegate 11 Alternatives Analysis Report 5.1
CHAPTER 5 — PERMITTING AND EASTMENT REQUIREMENTS
RENTON '
General Notes and Comments Concerning Permits
• Since this is a City project, a City of Renton Right -of -Way permit will not be
required for work within the City right-of-way. A right of way permit will be
required by King County for any construction within unincorporated King
County and could take 8 to 10 weeks to acquire. King County charges $100 for
the first 1,000 feet of pipe and $90 for each additional 1,000 feet or portion
thereof for its Right of Way permits. For example, 1,001 lineal feet of pipe
equals a permit fee of $190.
• King County DDES may take up to 120 days to approve a Clearing and Grading
permit. Fees for King County Clearing and Grading permits are determined by
the square footage of disturbance and the cubic yards of excavation. A City of
Renton Grading permit is not required for City utility projects located within the
City limits.
• Construction within easements will require restoration of all disturbed areas. For
construction within Unincorporated King County, the restoration requirements
would be set as part of the King County Grading permit process.
• Parcel No. 807901-0740, Tract X, located at the northeast end of NE 23rd Court
contains a City of Renton detention pond and will require the proposed main be
routed either along the north parcel line and then south, or along the east parcel
line and then west to the existing manhole on NE 23d Court. This route could
require the removal of some trees and vegetation, which may require a
restoration and mitigation plan as part of the permitting process.
• The stream crossing would need to be made using jack and bore construction
methods if the crossing is not made in an area where the stream is contained
within a culvert. If the crossing is made where the stream is contained within a
culvert, then conventional open cut construction methods may be feasible if the
WDFW allows the culvert to be held in place while the crossing is made or the
force main can be installed above the culvert while maintaining adequate cover
over the force main and separation from the culvert.
• For the jack and bore construction method, the jacking and receiving pits may be
located within the stream buffer area, but would require mitigation of any
disturbed areas within the buffer. If the pits are located outside the stream
buffer, then mitigation efforts may be avoided. For Alternative Routes 3A and
313, mitigation requirements would be determined by King County DDES as part
of the Clearing and Grading Permit process since the stream crossing is located
within unincorporated King County
• King County Wastewater Treatment approval takes approximately 4 to 6 weeks.
City of Renton I
5.2 Stonegate 11 Alternatives Analysis Report Ro`- H i l l
R E N T O N CHAPTER 5— PERMITTING AND EASEMENT REQUIREMENTS
• A WDFW HPA may be required for the stream crossings, depending on how the
crossing is made. If the stream is contained within a culvert at the crossing and
the proposed force main can be installed above the culvert, then an HPA may not
be required. However, if the force main must cross under the culvert then an
' HPA would probably be required, even if the pipe is installed using jack and bore
construction methods, especially if the crossing is made outside the existing road
prism.
• WDFW may not place a fish window restriction on construction if the proposed
force main is bored under the stream and any adjacent wetlands; approval would
require a dewatering plan for dewatering into the existing wetlands. WDFW
does not enforce buffer zones. Approval of an HPA can take up to six months.
EASEMENT REQUIREMENTS
' The need for easements, and the associated potential cost of these easements varies
with each route. The necessary easements have been identified for each alignment
along with their estimated acquisition costs. The valuation methodology used to
estimate the cost of the easements was one that Roth Hill has successfully used for
many years in the acquisition of hundreds of similar easements and is described later in
this report.
r
Summerwind Gravity Sewer
Construction of this gravity sewer will involve construction across easements between
the Summerwind Lift Station and NE 241h Court. The area of construction is already
' encumbered by an easement that is dedicated to public use that, in addition to the
named water and storm uses, may also be used for the proposed sewer improvements
since the force main from the existing Stonegate Lift Station currently crosses this
easement. Any removal of trees and vegetation would have to be negotiated with the
property owners. Parcel No. 807901-0740 is City -owned, resulting in no easements
being required for that parcel. Therefore, no additional easements will need to be
obtained for this alternative.
Force Main Alternative #1
Force Main Alternative #1 will involve construction across easements between the
Summerwind Lift Station and NE 24`h Court. This area is already encumbered by an
easement that is dedicated to public use that, in addition to the named water and storm
uses, may also be used for the proposed sewer improvements since the force main from
the existing Stonegate Lift Station currently crosses this easement. Any removal of
trees and vegetation would have to be negotiated with the property owners. Parcel No.
807901-0740 is City -owned, as noted above, resulting in no easements being required
' RothH1111 City of Renton
%.__� Stonegate 11 Alternatives Analysis Report 5.3
CHAPTER 5- PERMITTING AND EASTMENT REQUIREMENTS R E N T O N
for that parcel. Therefore, no additional easements will need to be obtained for this
alternative.
Force Main Alternative #2
The only construction associated with this route that is not within right-of-way is
located on Parcel No. 803540-0570, Tract G, which is a City -owned parcel. Therefore,
no easements would be required for this route.
Force Main Alternatives #3A and #313
This route would require several easements between 147`h Avenue SE in King County
and NE 20`h Street within the City of Renton. Some tree removal within the parcels
located between 1471h Avenue SE and Lyons Avenue NE may be necessary and would
have to be negotiated with the property owners and noted on the easement documents.
The force main would be installed within 145`h Place SE, between Lyons Avenue NE
and NE 20`h Place, which is a privately -owned access road, located on Parcel No.
032205-9292, and should not require any vegetation removal.
A list of parcels, parcel owners, values and estimated easement costs is shown in Table
5-2 and the location of each easement is shown in Figure 5-1. This table does not
include parcels owned by the City of Renton. Please note that the easement
requirements will depend on final route selection, which should be evaluated during the
design phase of the project.
Table
5-2
Easement
Requirements
- Alternatives #3A & C
Lot
Esmt Permit
Temp.
=.Req d
Pareet.'
Owner.
Size
L'ot
Market
Fee"- Area . 'Esmt Area
-Permit.:..
Jor
No.
Name.:
(sq,ft)
Value
.Value
`Value (sq.ft) Value. '•;(sq.ft)
Value
Route-
032305
Wolf,
69,696
$200,000
S250,000
$62,500
5,280
S4,740
10,560
$760
#3A &
9159
Richard and
#3B
Beverly
032305
Troske, Sara
4,500
S500
S625
$156
2,250
Slot)
4,500
S 100
#3A &
9192
#3B
032305
Miller, David
41,447
S175,000
S218,750
S54,688
6,550
S8,640
13,101
S1,380
#3A &
9292
and Katrina
#3B
032305
Hyatt(Travis)
28,072
S111,000
S138,750
S34,688
2,149
S2,660
4.286
S425
#313
9045
Kendra L
Ionly
177640
Scherer,
11,998
S75,000
S93,750
S23,438
1,818
S3,550
3,635
S570
#313
0030
Cathy J
only
Note: The above table does not include properties with existing easements or properties owned by the
City of Renton.
City of Renton
Ro
5.4 Stonegate 11 Alternatives Analysis Report ` _ i I
R E N T O N CHAPTER 5- PERMITTING AND EASEMENT REQUIREMENTS
EASEMENT VALUATION METHODOLOGY
The estimated easement values were developed using a methodology Roth Hill has used
to successfully acquire hundreds of easements. The lot size and lot value information
for the subject parcels were obtained from King County's Metroscan records. The
market value for the property was then estimated by adding 25% to the assessed value
of the land.
The fee value represents the use value of the easement. This value is approximately
25% of the market value if the easement is along the property line with only minor
impacts on the property. The value would go up or down depending on the proposed
easements impacts on the use of the property. For instance, if the easement bisects the
property, then the fee value may be 50% or more of the market value of the property.
Conversely, if the easement impacts property that is already impacted by other
easement or roads, then the fee value may be decreased. The lowest limits are typically
10%. For purposes of this report, the fee values were estimated at 25% of the market
value. The fee value was then divided by the total area of the lot and multiplied by the
total area of the easement to establish the value of the easement. Fifteen -foot -wide
easements were assumed for this project.
Most of the easements will require larger temporary construction permits to facilitate
the installation of the improvements. The temporary construction permits essentially
rent additional land area for temporary use by the contractor. In order to determine the
rental value of the temporary permit, the market value determined for property was
multiplied by a use value of 1%. The resultant value was then divided by the total lot
area and multiplied by the temporary permit area to establish the monthly rental value.
This monthly rental value was then multiplied by the number of months the property
would be temporarily impacted by construction. For purposes of this report, three
months (90 days) and a 30-foot width were assumed for each temporary construction
permit.
For the permanent easement values and the temporary construction permits, a minimum
offer of $100 was assumed if the calculations described above resulted in a value under
$100.
Rot Hill City of Renton
Stonegate 11 Alternatives Analysis Report 5.5
PARCEL 0110
CITY- HAS EASEMENT
REQUIRED FOR FM#1
& GRAVITY LINE
H T
G�
PARCEL 0740�
CITY -OWNED
'NO ESMT REQUIRED
PARCEL 0570
CITY -OWNED
NO ESMT REQUIRED
4-F0
RR FM#2
t.
w
w
v
PARCEL 9192 CITY
ESMT REQUIRED FOR TRACT
EXISTING FM#3A/FM#3B PARCEL 9045
R-O-W / \ ESMT ` FOR FM#3QB REQUIRED
I
PARCEL 9292
ESMT REQUIRED
FOR FM#3NFM#3B
PARCEL 9159 PARCEL 0030
ESMT REQUIRED ESMT REQUIRED
FOR FM#3A/FM#3B FOR FM#3B
RENTON CITY LIMITS
STONEGATE II ROUTE ANALYSIS
FIGURE 5-1
NON -RIGHT-OF-WAY CONSTRUCTION
-`NY
11+
RothHill
Chapter 6
In order to further compare the alternatives developed for each of the sewer conveyance
pipelines discussed in the Route Alternatives section, planning level projections of
probable construction costs were prepared for each alternative. The cost projections
were based on the approximate footages of pipe being replaced. These costs may be
used to compare the different routes for the proposed force main from the new
Stonegate 11 Lift Station or the proposed gravity service area. Cost projections were
also prepared to facilitate a review of the different construction methods that may be
used to install various segments of the project. Open -trench construction methods were
compared with trenchless construction methods in determining the cost of pipe
replacement.
The costs generated for each of the sewer conveyance pipelines are discussed in detail
below and include the assumptions used to develop the construction costs. An 8.9%
sales tax rate was applied to determine the projected construction cost for each
alternative. Allied design costs associated with engineering, public outreach, legal, and
City administration costs were not included in the cost projections as these will be
similar for each alternative. The estimated costs associated with easement acquisition
and permit fees have been included as they vary with each alternative. An overall Total
Project Cost was completed for these recommended alternatives for the City to use for
budgeting purposes and includes the cost for engineering and allied construction costs.
This overall cost can be found in the Recommendation section of the report and the
Executive Summary.
A 15% contingency factor was added to the projected total construction costs to allow
for inflation and unknowns on the project. The construction costs are conservative
given the high level of unknowns and the planning level basis used to develop them.
Detailed information on each construction cost projection may be found in
Appendix C.
City of Renton
Rot"n i l l
Stonegate 11 Alternatives Analysis Report 6.1
CHAPTER 6— OPINION OF PROBABLE CONSTRUCTION COSTS R E N T O N
Stonegate II Lift Station Installation
The construction cost analysis conducted for the Stonegate I1 Lift Station assumed the
lift station would be constructed at the existing site on an expanded easement. The
construction costs were largely based on recent bids received on similar public works
lift station projects in areas within close proximity to the City of Renton. Costs were
based on the following significant lift station project components: 12-foot diameter pre-
cast concrete wet well, three submersible Flygt sewage pumps, concrete vault for
emergency overflow storage, pre -cast concrete valve and flow meter vault, coatings for
the below -grade structures, lift station piping, above -grade building housing control
system and standby generator set, upgraded electrical service, a new water service,
paved asphalt concrete access driveway, and landscaping. Table 6-1 summarizes the
cost analysis performed for the Stonegate 11 Lift Station construction.
Table 6-1
Opinion
of Probable Cost
Stonegate
11 Lift Station Installation
`
Lift Station Construction
Construction Costs
S1,224,600
_.........................................................................I ....................................................................................................................................................................................................................................................................................................
Sales Tax @ 8.9%
$109,000
................ __........_..........._...................... _.... ......................... ............ ...._._......................
Subtotal
..... ............ ._..._.... _._.............................................................-----..._.......................................... ........._......_._._.........._........... ..........
S 1,333,600
..............
Contingency @ 15%
S200,000
Total Construction Cost
S1,533,600
Easement Fees
S25,000
Permitting Fees
S1,400
TOTAL COST
$1,560,000
Assumptions:
1. The construction costs include mobilization, materials, excavation and
backfill, shoring and dewatering, TESC, clearing and grading, electrical
and control system work, gravels, and surface restoration. Depths of the
wet well and overflow storage vault were based on rough estimates of the
necessary operational storage volumes.
2. The construction costs include abandonment of the existing Summerwind
and Stonegate Lift Stations with re -channeling and conversion of the
existing wet wells to gravity manholes.
3. Significant facilities for odor control and surge protection were assumed to
be unnecessary, and are not included in the costs.
4. The concrete overflow storage vault was sized to provide storage for two
hours at an Ultimate peak design flow rate of 775 gpm.
City of Renton RothHill
6.2 Stonegate 11 Alternatives Analysis Report %__�
R E N T O N CHAPTER 6— OPINION OF PROBABLE CONSTRUCTION COSTS
Summerwind Gravity Sewer Alternative
The construction cost analysis conducted on the gravity sewer alternative compared two
different methods of construction since the alignment of the proposed route was already
predetermined. Approximately 245 linear feet of 8-inch diameter gravity sewer pipe
will need to be installed between the existing Summerwind Lift Station and MH
5303317 at the end of NE 24`h Court. Table 6-1 summarizes the cost analysis
performed for the Summerwind Gravity Sewer Alternative.
Table 6-2
Opinion of Probable
S urnmerwind Gravity Sewer Alternative
Open -cut ; Trenchless
Construction. Construction (HDD)
Construction Costs
............... ................. ..... ._........................................... _....__................. _....
S44,125 S56,500
.._............ ............................. .._._.............................................. .._......
Sales Tax @ 8.9%
__.._................ ...................._...... ......__........__...........................
................. ......._..
S3,925 S5,000
__........_._.................... _..........._...................... ..__............-...................
.Subtotal
........................... -.......... _..... .......................__......... _...... _................
........ _................_................... ........._......... _........ .............._....._.__.
548,050 S61,500
..._..._.. -..._.............__...__....._............ _... _... _._....._............
Contingency @ 15%
... ............... ........................ .............. -....... ... ........................... ......................
$7,250 $9,200
Total Construction Cost
S55,200 $70,700
Permitting Fees
S 15 S 15
TOTAL COST
$55,215 $70,715
Assumptions:
1. The open -trench construction costs included mobilization, materials,
excavation, shoring, TESC, surface restoration, trench patching, and
asphalt overlays. Pipe depths were based on a review of the proposed pipe
sections to be replaced.
2. Horizontal directional drilling costs were based on a national survey
conducted by Trenchless Technologies. Actual drilling costs may vary.
Ro` N I I I City of Renton
Stonegate 11 Alternatives Analysis Report 6.3
CHAPTER 6 — OPINION OF PROBABLE CONSTRUCTION COSTS
RENTON
Force Main Alternatives
Unlike the gravity sewer alternative discussed above, the construction cost analysis
conducted for the force main alternatives analyzed the costs associated with the
different proposed routes for the force main and did not evaluate different construction
method alternatives.
While FM#3A and FM#313 require more pipe than the first two alternatives, FM#1 and
FM#2 would both constructed in the Summerwind and Stonegate developments and
thus require additional asphalt overlay quantities for restoration after the force main
installation has been completed based on the width of the existing road surface. Table
6-2 summarizes the cost analysis completed for the force main alternatives.
Table 6-3
Opinion
of Probable
:Alternative #1'"
; Alternative #2
Alternative #3A-•
Alternative #313
Construction Costs
....................................... _............. _..... ............ .... ....... ...... .............
S494,300
........ _.................. ......................................................
S504,775
........._.................................................................... .................................................
$516,325
....__.__.._..-.................. .._....._
$515,225
........ _... _.._.............. _.... __.-............ _._......... --
Sales Tax @ 8.9%
S44,000
S44,925
$45,975
S45,875
Subtotal
$538,300
.... $549,700
._. __ ... .. ....
S562,300
_ .._ . .... ...
_ __ .. ...... __......... _ __ ._
S561,100
- - -
Contingency @ 15%
$80,700
$82,500
S84,300
$84,200
Total Construction Costs
$619,000
$632,200
S646,600
$645,300
Easement Fees
$0
SO
S 13,480
S 19,690
Temporary Cosst. Permit ...
$0
.......... ...
... .. $0
S2,240
..... _..............._......_
S3,235
......__ .........._.............._
Permitting Fees
S 15
$15
S2,700
.._........._ ..._
S2,700
TOTAL COST
$619,015
$632,215
$665,020
$670,925
Assumptions:
1. The open -trench construction costs included mobilization, materials, excavation, shoring, TESC,
surface restoration, trench patching, and asphalt overlays. Pipe depths were based on a review of
the proposed pipe sections to be replaced.
2. A full width asphalt overlay was assumed for all sewer replacement in the right-of-way.
3. Horizontal directional drilling costs were based on a national survey conducted by Trenchless
Technologies. Actual drilling costs may vary.
City of Renton RothHill
6.4 Stonegate 11 Alternatives Analysis Report %___
' R E N T O N CHAPTER 6— OPINION OF PROBABLE CONSTRUCTION COSTS
Field Avenue Interceptor Improvements
Similar to the Summerwind Gravity Sewer Alternative, the construction cost analysis
conducted on the Field Avenue Interceptor improvements consisted of comparing two
different methods of construction. The Field Avenue Interceptor Improvements looked
at replacing approximately 970 linear feet of 8-inch diameter PVC with 12-inch and 15-
inch diameter gravity HDPE sewer pipe between MH 5303228 in Field Avenue NE and
MH 5303218 at Sunset Avenue. Table 6-3 summarizes the cost analysis performed for
the Field Avenue Interceptor Improvements.
Table 6-4
Opinion of Probable
Trenchless
Open -Cut ..
Construction`
Construction
(Pipe=Bursting)'
Construction Costs
................................................................-.................. .........._.................................._._............................
S260,950
_....... _........................ _........................... ..............
....................... S203,400
Sales Tax @ 8.9%
................... ...................._.......__................_........ _.............. -... ...__.._............
S23,250
....._._..._._..... _.......... ................................................. ..._..._........... .........................................
.... ..... ...... _............................................... ...................
S18,100
Subtotal
.................. _........._............................ ...._................................... ........_....._...................
$284,200
_....... ........................_............_............................... ....
_............................... ................................ ....... ........
S221,500
......................... ..........................................
Contingency @ 15%
S42,600
................................................_...
S33,200
Total Construction Cost
$326,800
S254,700
Easement Fees
............ ............._..............._....................... ............................. ...... .....
SO
.... ................................ ................................... _.._-._._..._
SO
Temporary Const. Permit
..............................._..................
.... ...... ......_........__..._.._.......
SO
..........-........_..................._.s0....................
....... _...........__..__......._............ ..... .... _ _._.................. .........
$0
PermittingFees
........................_..._......_.$............._...._......
TOTAL COST
$326,800
$254,700
Assumptions:
1. The open -trench construction costs included mobilization, materials,
excavation, shoring, TESL, surface restoration, trench patching, and
asphalt overlays. Pipe depths were based on a review of the proposed
pipe sections to be replaced.
2. Pipe bursting costs included mobilization, materials, excavation, shoring,
TESC, and surface restoration.
3. Side sewer re -connections were assumed for every building lot adjacent to
the sewer.
4. A full width asphalt overlay was assumed for all open cut sewer
replacement in the right-of-way.
Rom i I I City of Renton
Stonegate 11 Alternatives Analysis Report 6.5
CHAPTER 6— OPINION OF PROBABLE CONSTRUCTION COSTS R E N T O N
Sunset Interceptor Improvements
The construction cost analysis performed for the Sunset Interceptor Improvements also
compared two different methods of construction. The lengths and routes were taken
from the original Sunset Phase 3 Pre -Design report. The costs included in that report
were updated to reflect recent trends in construction costs. The Sunset Interceptor
improvements consisted of replacing approximately 2,005 linear feet of 12-inch and 15-
inch pipe along NE Sunset Boulevard with 15-inch diameter and 18-inch diameter
gravity sewer HDPE and/or PVC pipe between Field Avenue NE and Duval Avenue NE
and between Anacortes Avenue NE and Union Avenue NE. Table 6-4 summarizes the
cost analysis performed for the Sunset Interceptor Improvements.
6-5
OpinionTable
Sunset Interceptor
Improvements
.- 'Tren. chless
Open Cut
;Cons.truction.
`. Construction
;(Pipe Bursting) .;,
Construction Costs
_............... _... ..............................._- ....................... _..-....... .................................
$581,725
............................. _._...__._........._................. _.......... ...._.................._............._.
S448,700
....... ....._.............................._............... ............................ .
Sales Tax @ 8.9%
.... ..........._......._............................._...._._.............--...... -................_......................._._...._........._.........._.__..._......_......._..............._...._._._...
S51,775
S39,900
__._.._.__......_..__.....__..._.._._._._...._.............................__.
Subtotal
............................
S633,500
...._......................................._...__..__...-
S488,600
..__............._........_.._................_....._..................................
Contingency @ 15%
S95,000
S73,300
Total Construction Cost
$728,500
S561,900
Easement Fees
_.. ....................... ....................._..__..................................................................................._........................................_..............................._..................._............................_............._..._.....................--
SO
SO
Temporary Const. Permit
SO
—
SO
.............
Permitting Fees
SO
SO
TOTAL COST
$728,500
$561,900
Assumptions
1. The open -trench construction costs included mobilization, materials,
excavation, shoring, TESL, surface restoration, trench patching, and
asphalt overlays. Pipe depths were based on a review of the proposed
pipe sections to be replaced.
2. Pipe bursting costs included mobilization, materials, excavation,
shoring, TESL, and surface restoration.
3. Side sewer connections were determined based on the previous review
of television inspection video for existing side sewer locations that was
performed for the Sunset Interceptor Phase 3 Pre -Design Report.
4. A half -width asphalt overlay was assumed for Sunset Interceptor
improvements.
City of Renton
thHill
6.6 Stone ate 11 Alternatives Analysis Report Ro%I
R E N T O N CHAPTER 6— OPINION OF PROBABLE CONSTRUCTION COSTS
Proposed Gravity Sewer Alternatives
As part of the research conducted for this report, Roth Hill investigated the costs for
providing sewer service to the area located between the creek tributary to May Creek
and 1481h Avenue SE. Construction costs were prepared for two different alternative
routes to provide the needed service. The first alternative consisted of installing
approximately 3,400 linear feet of 8-inch gravity sewer in easements and right-of-way.
The second alternative consisted of installing approximately 3,550 linear feet of 8-inch
gravity sewer in easements and right-of-way. A detailed estimate of the permit and
easement costs was not completed for this analysis. The estimates shown in the table
below are preliminary "and should be refined if the City wants to move forward with
either alternative. For comparison purposes, Alternative #1 would require
approximately three to four separate easements and Alternative #2 would require
approximately three easements. Table 6-5 outlines the cost analysis performed for the
Proposed Gravity Sewer Alternatives.
Table 6-6
Opinion of Probable
Proposed
Alternative. #1 ._ Alternative #2=
Construction Costs
............. ..................................... ...................................... ............._............................
S727,775 .
...................................._... ..... ............ ...........................................
S733,175
_...._...........-._
Sales Tax @ 8.9%
............ ....................................................... ... ........ ........__......._...__..... .............. ........................._......._...._....__.._..................................
S64,225 ....... ..._..._..................................
..... _....... ........................._..
S65,225
............ ...............
Subtotal
-.._.. ......... . --...............................
......................................................................................_....._.....__......................._._
S786,000
.-............... _....................... ..._
...._............................ ._.
_..................$798,400
Contingency @ 15%
S 117,900
..........................
S119,800
Total Construction Costs
S903,900
S918,200
Easement Fees
................... ........... .................................................................... _........................ ............
S 15,000
... ........................... ............... .............. -.................... ....._...........................
.........................$13,000
Temporary Const. Permit
................... ............_................._...................................................................................................................................-...................................................................................
$6,000
... _........................ -..........................
S5,000
Permitting Fees
S2,600
_................................ _..
S2,600
TOTAL COST
S927,500
S938,800
Assumptions
1. The open -trench construction costs included mobilization, materials,
excavation, shoring, TESC, surface restoration, trench patching, and
asphalt overlays. Pipe depths were based on a review of the proposed
pipe sections to be replaced.
2. Side sewer connections were assumed for every building lot adjacent
to the proposed sewer at an average length of 30 feet of 6-inch PVC
pipe per side sewer (10 feet average depth per connection).
3. Manhole depths were determined by reviewing existing contours. The
price of extra depth manholes was included in the cost per manhole.
4. A full width asphalt overlay was assumed for all open cut sewer
replacement in right-of-way.
Rot H i I I City of Renton
1 %_ Stonegate 11 Alternatives Analysis Report 6.7
Chapter 7 Is
RECOMMENDATIONS
This section of the Alternatives Analysis Report for the Stonegate II project provides
recommendations for a preferred alternative associated with each of the five different
sewer conveyance pipelines within the project area. The recommendation for each
sewer conveyance pipeline is discussed separately below.
Summerwind Gravity Sewer Alternative
The recommended alternative for the Summerwind Gravity Sewer is to install the
proposed sewer pipe using horizontal directional drilling. Although the open cut
method appears to be less expensive, using HDD to install the pipe without relocating
the exiting utilities or disturbing the existing landscaping would minimize impacts to
the community and may be worth the additional cost. The overall schedule may also be
reduced since coordination with other utilities would be reduced.
Force Main Alternatives
The recommended alternative for the force main route between the new Stonegate II
Lift Station and the Field Avenue Interceptor is FM#3B, even though it is
approximately $51,700 more expensive than the least expensive alternative (FM#1).
The increased cost of FM#3B is only approximately 8% higher than FM#1. FM#1
would require construction within the existing developments of Summerwind and
Stonegate, which we understand the City would like to avoid. Furthermore, FM#3B is
a cleaner route with less bends and would have fewer impacts on the neighborhood
during construction.
FM#3B is also slightly more expensive than FM#3A. The primary advantage of
t FM#3B compared to FM#3A is that it minimizes construction impacts near existing
residential homes.
Field Avenue Interceptor Alternatives
The recommended alternative for the improvements to the existing Field Avenue
' Interceptor is to construct the improvements using a trenchless technology such as
pipe -bursting or pipe -reaming. Not only is this alternative less expensive, but it will
have less impact on the surrounding neighborhood.
RothHill City of Renton
Stonegate 11 Alternatives Analysis Report 7.1
CHAPTER 7- RECOMMENDATIONS R E N T O N
Sunset Interceptor Improvements
The recommended construction method for the improvements to the Sunset Interceptor
has not changed since the completion of the Sunset Interceptor Phase 3 Pre -Design
Report. It still consists of a combination of pipe -bursting and open -cut with the
majority of the line being installed via pipe -bursting. The only open -cut sections of
construction will be where new pipe is required at the west end of the project near
Union Avenue NE between MH 5303185 and the proposed MH 5303185A.
Proposed Gravity Sewer Alternatives
Both of the alternatives for the proposed gravity sewer are viable and could be
constructed by the City in the future. Alternative #1 is slightly cheaper than
Alternative #2 and Alternative #2 will require significant coordination with the
property owner whose property is bisected. The City will need to perform further
analysis on these options in the future should the need to provide sewers to the area
arise. This analysis was done separately from the Stonegate It analysis and, as such,
the costs for these improvements are not part of the overall project costs shown below.
ESTIMATE OF TOTAL PROJECT COST
Based on the recommended improvements, an overall project budget was developed for
the City to use for its planning purposes. These budgets should be refined as more
information is obtained during the design phase of the project. Additionally, an
evaluation of the Stonegate II Lift Station was not conducted as part of this report per
the City's request. The cost shown in Table 7-1 for the Stonegate II Lift Station does
not account for any required land acquisition as this information cannot be estimated at
this time and is a rough estimation of the construction cost. The Engineering cost has
been increased by 3% to cover City administration costs.
Description
Cost
Summerwind Gravity Sewer Cost
..........................................._...................__.._......_.........__.............._............................_.....__..... _....._._.............._....................................
$70,715
_
Force Main Alternative Cost
..._.......................------..............._.._..........._......._...---..._....__....._................................._....._........................._...................................
$670,925
Field Avenue .Interceptor Cost
. .... .............._.... .............._................................................._... ... -_................................. ................._...__....._.............. ............ ........................................................._.....-
$254,700
.....................
Sunset Interceptor Improvements
................ ........................ __.............____..........................._._-................._......................................................................__...................................
$561,900
Stonegate II Lift Station Cost
$1,560,000
TOTAL CONSTRUCTION COST
$3,118,240
Engineering
$749,600
TOTAL PROJECT COST
$3,867,900
City of Renton Rot Hill
7.2 Stonegate 11 Alternatives Analysis Report I
Appendix A
APPENDIX A
Preliminary Geotechnical Report
HWA GeoSciences, Inc.
City of Renton
Ro`thHill
Stonegate 11 Alternatives Analysis Report
I I
1 4
io
I I
I�
V�, HWAGEOSCIENCES INC.
July 23, 2007
HWA Project No. 2007-080
Roth Hill Engineering Partners, LLC.
2600 1161h Avenue NE, Suite 100
Bellevue, Washington 98004
Attention: Mr. Erik Waligorski, P.E.
Subject: PRE -DESIGN GEOTECHNICAL FEASIBILITY REPORT
PHASE I ROUTE ALTERNATIVES ANALYSIS
RENTON STONEGATE II -SEWER SYSTEM IMPROVEMENTS
RENTON, WASHINGTON
Dear Erik:
In response to your request, HWA GeoSciences Inc. (FIWA) is pleased to present this
preliminary geotechnical report for Phase I geotechnical alternative analysis for the
proposed sanitary sewer and lift station improvements, as part of the Renton Stonegate II
Sewer System Improvement project in northeastern Renton, Washington.
PROJECT UNDERSTANDING
Currently the existing residential developments known as Summerwind and Stonegate,
are served by separate gravity collection systems, lift stations and force main conveyance
systems. The purpose of this project is to combine the flows and utilize a single force
main system. This will be accomplished by converting the existing Summerwind lift
station into a manhole and installing new gravity sewer between the converted wet well
and the existing Stonegate sewer manhole located in NE 24th Court. The combined
Summerwind and Stonegate flows will then be conveyed by the existing Stonegate
gravity system to a new lift station located adjacent to the existing Stonegate lift station at
the northwest corner of NE 261h Street and 148th Avenue SE. It is assumed that the
existing Stonegate gravity sewer has sufficient capacity to handle the increased flow.
From the new Stonegate lift station, combined flow will be conveyed via force main to
the existing Field Avenue sewer system along one of four alternative routes. The existing
Field Avenue system is constructed of mostly 8-inch diameter PVC and the pipe needs to
be replaced/upsized to handle the increased flow. The four force main alignment
alternatives under current consideration are:
Alternative #1: The force main would travel uphill to the west and 19730 - 64th Avenue W.
southwest along NE 26th Street, Lyons Avenue NE and NE 241h Court; Suite zoo
continue around the existing Summerwind Lift station, south on Ilwaco Lynnwood, WA 980365957
Tel: 425.774.0106
Far: 425.774.2714
www. hwageosciences.com
July 23, 2007
HWA Project No. 2007-080
Avenue NE and finally west on NE 201h Street to Field Avenue NE and tie-in with the
exiting gravity system.
Alternative #2: The force main would travel uphill to the west and southwest along NE
26th Street and Lvons Avenue NE, NE 22nd Court, along an easement between the two
developments connecting to NE 201h Street and the gravity system on NE Field Avenue.
Alternative #3: The force main would travel east to 1481h Avenue SE and then proceed
west along SE 102nd which turns south and becomes 147th Ave SE. The force main
would continue south along 1471h Ave SE before turning west and following along an
easement coincident with 20th Avenue NE easement intersecting the improved portion of
20`h Avenue NE at it's terminus at llwaco Avenue NE. The line will continue west and
southwest to the gravity system tie-in on NE Field Avenue.
Alternative #3h: The force main would travel east to 148`I' Avenue SE and continue south
until it is in line with NE 201h Place before proceeding west cross-country along an
alignment coincident with 20th Avenue NE easement intersecting the improved portion
of NE 201h Avenue at it's terminus at Ilwaco Avenue NE. The line will continue west and
southwest to the gravity system tie-in on NE Field Avenue.
The approximate route of each alternative is depicted on Figure 2.
GENERAL SiTE CONDITIONS
Setting
The project site is situated along the northeast edge of the Renton Plateau, a broad
glacially modified upland plain. The project site is dissected by a north -south oriented
unnamed creek with headwaters south of SR 900 (Sunset Blvd.) that drains into May
Creek. The hip -hest point of the project area is located in the southwest along NE Field
Avenue north of SR 900 (Elev. 1 475 MSIJ The low point (Elev. ± 350 MSL) is
proximal to the existing Stonegate lift station in the northeast corner of the project area.
Total relief appears to be at least 125 feet over the area.
Local Geology
Geologic information for the project site was obtained from the published geologic map
for the area; SurTcial Geologic Map of the King County, Puget Sound Region,
Washington (Troost, et al, 2004). The map indicates that the surficial geology of the
subject parcel consists of Vashon till, a non -stratified and non -sorted mixture of clay, silt,
sand, and gavel. The till was deposited over the advance outwash as a defonning bed of
reworked sediment beneath the glacial ice. It forms a very compact unit due to the weight
of the over-riding glacier. Cobbles are typically scattered throughout the till, and boulders
are also often encountered.
Renton Stonente 11 Pre -Design GeoTech Rptnts 2 HWA GEOSCIENCPS INC.
1�
July 23, 2007
HWA Project No. 2007-080
�I t
Soils
u
According to the Soil Survev of King County Area (available online from the Natural
Resources Conservation Service) the subject site is underlain by Alderwood gravelly
sandy loam, on 6 to 15 percent slopes and the Ragnar-Indianola association on sloping
ground. The Alderwood gravelly loam formed on glacial till and poses a moderate
erosion hazard. The Ragnar-Indianola association soils formed on glacial outwash soils
and also pose a moderate erosion hazard. The Alderwood soils are situated along the
upland plateau and hillslopes. The Ragnar- Indianola soils cover the rolling terrain in the
northeast portion of the site.
Geologic Hazards
In this section, the potential for various geologic hazards on site are discussed including
erosion, landslide, and seismic (liquefaction and settlement) hazards.
Erosion Hazards
As discussed above, the local soils mapping by the NRCS indicates that site soils pose
only a moderate erosion hazard. The highest potential for erosion will occur during
construction where excavations are required and after the vegetation has been cleared or
pavement removed and the soil is directly exposed to the elements. However,
implementation of appropriate best management practices (BMPs) for handling of storm
water runoff durine construction will largely mitigate adverse effects associated with soil
erosion on site.
Landslide -Steep Slope Hazards
Typically, landslide hazards are defined as those slope areas potentially subject to mass
earth movement based on a combination of geographic, topographic, and hydrologic
factors, with a vertical height of 10 feet or more. These include the following:
• Areas of historic landslides as evidenced by mapped landslide deposits,
avalanche tracks, and areas susceptible to basal undercutting by streams,
rivers or waves:
• Areas with slopes steeper than 15 percent which intersect geologic
contacts with a relatively permeable sediment overlying a relatively
impermeable sediment or bedrock, and which contain springs or ground
water seeps;
• Areas located in a canyon or an active alluvial fan, susceptible to
inundation by debris flows or catastrophic flooding.
Renton Stonegate 11 Pre -Design Geo 1'ech Rptnts 3 HWA GEOSCIENCIS INC.
'1
July 2'), 2007
' I-IWA Project No. 2007-080
Based on our observations, slopes steeper than 1 percent exist along the northeastern
P P �
portion of the site where the ground slopes towards the un-named creek situated between
' 147th Avenue SE and Lyons Avenue NE. From East of Ilwaco Avenue NE to the un-
named creek the slope is inclined from 10 to about 35 percent. However, the local
geologic mapping indicates the existing native soils consist of granular, glacial till soils
that are very dense, and typically not subject to global failure or deep-seated rotational
sliding. In our opinion, the proposed sewer system improvements will have a minimal
impact on site slopes and will not increase the hazard level associated with occurrences of
' potential shallow landslides.
' Seismic Hazards
Seismic hazards are defined as areas subject to a severe risk of earthquake damage as a
result of seismically -induced ground rupture, liquefaction, ground spreading, and
settlement. A seismic event generates ground movements that are horizontal, vertical, or
isome combination of the two. It can result in permanent ground damage, directly by
ground rupture or indirectly from ground shaking. Ground shaking can damage
underground structures; trigger slippage in areas susceptible to landslides; or cause
liquefaction, ground spreading or settlement.
Ground rupture is the general term used to characterize an area where fault movement
results in a distinct offset at the ground surface, or possibly cracks or fissures. The
nearest known fault considered to be active by the United States Geological Survey is the
Seattle Fault zone, which is located approximately 5 miles north of the subject site near
Factoria. Therefore, damage to structures on this site caused by rupture along this fault
zone is relatively unlikely.
Liquefaction occurs .when loose, saturated, and relatively cohesionless (clean sandy) soil
deposits temporarily lose strength as a result of earthquake shaking. Locally, the site soils
are anticipated to consist predominately of slightly silty to silty, glacially over -
consolidated sands that are not subject to liquefaction. Therefore, the likelihood of
structural damage due to settlement is low except in the area of creek crossings where
alluvial soils are anticipated to exist that could liquefy. Should these conditions be
identified to exist during Phase 11 of this project, the foundation soils in those areas could
be removed and replaced with properly compacted granular fill or the pipeline could be
supported on deep foundations that bye -pass the potentially liquefiable soils.
Ground settlement can occur during or after an earthquake when shaking or liquefaction
results in densification of soils sensitive to vibration effects (such as thick peat deposits,
loose saturated granular soils, and improperly constructed fills). Typically, areas mapped
as seismic hazards associated with liquefaction coincide with areas of settlement hazard.
In consideration of the predominant materials expected -to be -encountered -on -site,, and
Kenton Stonegate 11 Pre -Design Geo'rech Rptnts 4 HWA GEOSCIENCES INC.
July 23, 2007
HWA Project No. 2007-080
assuming that the design recommendations of are followed, however, the likelihood of
structural damage due to settlement is low except in the area of creek crossings where
alluvial soils are anticipated to exist. Should these conditions be identified to exist during
Phase II of this project, the foundation soils in those areas could be removed and replaced
with properly compacted granular fill or the pipeline could be supported on deep
foundations that bye -pass the existing settlement prone soils.
GENERAL GEOTECHNICAL CONSIDERATIONS AFFECTING ALL ALTERNATIVES
The following series of discussions touches on certain aspects of the project that will
require consideration regardless of the force main route alternative constructed.
Summerwind-Stonegate Connection
In order to combine the effluent from the Summerwind development and Stonegate, a
gravity line would be installed connecting the Summerwind Lift Station with the existing
sanitary manhole located in NE 241h Court. The summerwind Lift Station would be
converted to a wet -well structure. The Summerwind Lift Station is situated on the berm
of an existing,= storm water detention pond. Impacts to local property and the existing
pond can be minimized by using trenchless technology, such as horizontal directional
drilling (HDD) or microtunneling, to install the new gravity sewer connection between
the Summerwind Lift Station and the existing Stonegate collection system. This would
require the installation of a launching pit in the street and drilling the new pipe uphill to
intercept the lift station vault. The existing vault could possibly be utilized as a receiving
pit for the bore.
Force Main Creek Crossing
All four alternative force main alignments under consideration will involve one creek
crossing. For Alternatives #1 and 92, the creek crossing is located approximately 300
feet west of the existing and proposed new Stonegate lift station along NE 26th Street. At
this crossing, the creek is conveyed under the road by an approximately 48-inch
corrugated metal pipe culvert. The force main would need to be installed below the
culvert. If conventional open cut construction were considered, the creek would have to
be temporarily diverted and the site dewatered to facilitate excavation. Alternatively,
trenchless construction method, such as pipe jacking could be done. The jacking and
receiving pits would likely need to be shored and dewatered. Due to the amount of
development in the area and the disruption that open cutting would have, we expect that a
trenchless undercrossing may be most preferable at this location.
With regard to Alternatives 43 and 93b, both options will involve a stream crossing west
of 147th Avenue SE that may need to be installed using trenchless construction to avoid
disrupting the creek. However, the condition of this crossing is relatively primitive and it
may be possible that during the dry season a by-pass could be installed to divert any
creek flow temporally while the force main is installed using -standard -(open -cut) --
Renton Stonegate 11 Pre -Design Geo"rech Rptnts 5 HWA GLOScui\`cES Inc.
July 23, 2007
HWA Project No. 2007-080
construction methods. During our site reconnaissance visit of June 12, 2007, we observed
some standing water to the north ofthe culvert, and very little to no flow. Open cut
construction and Culver replacement would provide an opportunity to improve the culvert
- which appears to be set too high in the roadway and lacks appreciable erosion
protection on the up- and down -stream ends.
Impacts to Existing Summer -wind & Stonegate Communities.
Regardless of which route alternative is chosen, the new force main will be tied into the
gravity system on NE Field Avenue. Portions of this line will need to be upsized by either
conventional or trenchless methods. The project is located on relatively quiet residential
streets having two traffic lanes, and typically, room for parked vehicles on one or both
sides. Open -trench interceptor replacement poses issues with traffic control, surface
restoration cost, and possibly dewatering. To reduce surface impacts along the existing
Field Avenue interceptor alignment, where the existing pipe needs to be upsized,
trenchless technology such as pipe -bursting or pipe -reaming is being considered. Each of
these technologies are discussed briefly in the following paragraphs
Pipe -Bursting
The pipe bursting process consists of in -situ fragmentation, displacement, and
replacement of the existing pipe with new polyethylene pipe of equal or larger diameter.
Typically, the existing pipe is split by a hydraulic or pneumatic bursting -head or
nosecone to which the new polyethylene pipe is attached. As the existing pipe is burst,
the new polyethylene pipe is pulled along the alignment of the old pipe. A chain or cable
towline attached to a hydraulic jacking or winch system is used to advance the bursting
head. Typically, the polyethylene pipe installed during the pipe bursting process consists
of 20 to 40 foot sections that are welded together on site. Pipe bursting is normally
conducted between two points of access; i.e., station —to -station with stations consisting of
existing manholes, or insertion and extraction pits. Pipe burst distances up to about 300
feet are typical. When completed, the replacement pipe invert very nearly matches the
original pipe invert.
Factors affecting the use of pipe -bursting in this area will be the existing lines proximity
to other utilities, depth below grade, and condition of the trench backfill surrounding the
existing pipe. Even trenchless methods such as pipe bursting can cause bulging of the
existing roadway if the pipes are shallow or the existing fill is dense. Side sewer
connections would still require excavations if required.
Pipe -Reaming
Pipe -reaming is similar to pipe -bursting in that a replacement pipe is installed as the
original is destroyed without open cuts along the alignment. Pipe -reaming involves the
fragmentation of the original pipe by "back -reaming" using a Horizontal Directional Drill
with a back reamer that reduces the old pipe into pieces which are carried along with soils
by drilling fluid to an extraction point. When completed, the replacement pipe invert will
be lower than the original_b_y- about -half the -original -pipe diameter. -The advantage -of 111-is
Renton Stonegate 11 Pre-Dcsign Gecirech Rptnts
HWA GEOSCIENCES INC.
July 23, 2007
FIWA Project No. 2007-080
method is that it does not rely on volumetric distortion to break the pipe and therefore
does not cause significant bulging of the fill or the roadway. However, this method is not
appropriate for replacement of cast iron pipe. As with pipe -bursting, side sewer
connections require excavations for connection.
ASSESSMENT OF ALTERNATIVE GEOTECHNICAL CONDITIONS
The following sections describe and present our preliminary assessment of the subsurface
conditions expected along each proposed alternative route.
Alternative #1
This alternative involves open cut construction from the existing Stonegate lift station
and a creek crossing. Alternative 1 alignment is generally within the confines of existing
roadways, except for about 300 feet where the alignment goes cross-country between the
NE 24`h Court in Stonegate and NE 23`d Court in Summerwind. From there the route
extends west and then south along Ilwaco Avenue NE before continuing west at the
intersection with NE 201h street to the NE Fields Avenue Interceptor. Based on our review
of local geologic and soils information, the alignment is expected to encounter glacial
outwash sands and gravels along NE 261h Street and up along NE 24th Court, before
encountering glacial till soils near the existing detention pond and further uphill. Alluvial
soils and/or reworked outwash soils are expected within 10's of feet on either side of the
unnamed creek. Groundwater should be anticipated at shallow depth within about 50 feet
on either side of the creek. Perched seepage may be encountered locally at shallow depth
along the transition between fresh and weathered glacial till.
Glacial till and outwash will provide excellent foundation for the force main, although the
presence of coarse material at the pipe invert may require sub -excavation to
accommodate a layer of bedding material to cushion the pipe. Glacial till soils are
typically moisture sensitive and should only be used as trench backfill during dry
weather. Clean sandy glacial outwash soils (i.e., with less than 5% fines content) may be
used during wet weather as trench backfill. Depending upon the composition and relative
density of the alluvial soils, foundation improvement may be required that could consist
of, removal of alluvial soils and replacement with properly compacted granular fill, or the
installation of piles or shafts to glacial soils for pipe support. Alternatively, the force
main could be installed below the alluvial soils by pipe jacking methods assuming the
jacking pits could be efficiently sealed or dewatered.
Alternative 92
This alternative very similar to Alternative u 1 except that instead of proceeding west and
entering Summerwind via the proposed gravity line connector route, this alternative
continues south along NE Lyons Avenue to NE 22"d Court and via an alley to NE 201h
Street. We expect the soil and groundwater conditions to be similar to those expected_ _
Renton Stonegate 11 Pre -Design GeoTech Rptnts
HWA GBOSCL:NCES INC.
July 23, 2007
HWA Project No. 2007-080
along Alternative # 1 except that glacial till may not be encountered until the alignment
traverses NE 22nd Court. Similar geotechnical considerations with regard to soil and
groundwater conditions are expected as discussed for Alternative #1 in the preceding
paragraphs.
Alternative 43
Alternative #3 departs from the proposed Stonegate II lift station east towards 1481h
Avenue SE, where it turns south. for about 750 feet before turning west into SE 102nd
Street to 147`h Avenue SE and continuing south another 730 feet. Near the intersection
with SE 104`h Street (Approximately coincident with NE 201h street in Summerwind) the
route turns due west following a driveway easement, crossing the unnamed creek before
climbing upslope to NE 201h Street and continuing west to connect to the NE Field
Avenue Interceptor.
Based on our review of local geologic and soils information, the alignment is expected to
encounter glacial outwash sands and gravels along NE 26th Street and probably up 148th
Avenue SE, along SE 102nd Street and 1471h Avenue SE to a point west of the creek
crossing where upland glacial till soils are expected. Alluvial soils and/or reworked
outwash soils are expected within 10's of feet on either side of the unnamed creek.
Groundwater should be anticipated at shallow depth within about 20-30 feet on either
side of the creek. Perched seepage may be encountered locally at shallow depth along the
transition between fresh and weathered glacial till as the alignment proceeds uphill
towards the Suirunerwind development and NE 20th Street.
The force main would be relatively shallow and require a relatively narrow and shallow
trench, consequently it could be efficiently installed by conventional open cut methods.
Depending upon the trench depth and time of year shallow groundwater seepage would
be expected within 10's of feet of either side of the creek crossing and may require
dewatering by pumping in sumps within the trench. West of the unnamed creek perched
groundwater seepage could be encountered along the weathered till -fresh till transition
zone that may flow into the trench. This seepage can be managed by installing a
perforated drain pipe along the trench bottom as the excavation proceeds uphill. The
collected groundwater seepage would be conveyed down to the creek crossing and
discharged.
Alternatively, 1-IDD methods may be practical for use installing the pipe up the hill,
although it would probably be drilled downhill. Adequate exploration along the
alignment is critical to determine if the soil is likely to be very dense or contain boulders
that could cause problems for 1-IDD methods.
Renton Stonegate 11 Pre -Design GeoTech Rptnts 8 HWA GEOSciENCES INC.
July 23, 2007
HWA Project No. 2007-080
Alternative #3b
Alternative 93b restricts the route to 148'1i Avenue NE until SE 1041h Street is reached. At
that point, the pipeline traverses cross country to the west between two residential
properties to 1471h Avenue SE before continuing along the driveway easement, crossing
the creek, and climbing upslope to NE 20'h Street in the Sumrnerwind development.
Similar geotechnical considerations with regard to soil and groundwater conditions are
expected as discussed for Alternative #3 above.
SUMMARY & CONCLUSIONS
After our site reconnaissance, review of the published geologic and soils information for
the local area, and our experience with these types of projects, we conclude that project is
feasible along all the proposed alignments. Alternatives 43 and 3b, are most attractive
with regard to limiting disruption to residents within the Stonegate and Summerwind
developments. Moreover, we expect that permitting and access issues may be simpler for
the proposed creek crossing along Alternative 3 and 3b routes, because what will be
designed and constructed would probably be considered a significant upgrade to the creek
conveyance at that location.
PHASE 2 GEOTECHNICAL ENGINEERING STUDIES
Phase 11 will consist of the development of engineering soil parameters, geotechnical
recommendations, and details used to design the project for construction. We presently
are assuming that one preferred route for the force main will have been selected: our
objective will be to evaluate conditions along the chosen alignment. This work will
include drilling a series of exploratory borings along the pipeline routes to evaluate soil
and ground water conditions, trenchless construction, pipe bursting, and open trench
construction, as necessary for the preferred alignment. We will prepare a proposed scope
and budget for this work at the conclusion of the Alternatives Analysis task.
CONDITIONS & LIMITATIONS
We have prepared this preliminary report for the City of Renton and Roth Hill
Engineering Partners for use in design of this project. Experience has shown that soil and
ground water conditions can vary significantly over small distances. Inconsistent
conditions can occur between exploration locations and may not be detected by a
geotechnical study of this nature.
Within the limitations ofscope, schedule and budget, HWA attempted to execute these
services in accordance with generally accepted professional principles and practices in
the fields of geotechnical engineering and engineering geology in the area at the time the
Renton Stone2ate If Pre -Design GeoTech Rptnts 9 I I WA GEOSCIENCES INC.
July 23, 2007
HWA Project No. 2007-080
report was prepared. No warranty, express or implied, is made. The scope of our work
for this phase did not include field exploration, environmental assessments or evaluations
regarding the presence or absence of wetlands or hazardous substances in the soil, surface
water, or ground water at this site.
We appreciate the opportunity to provide geotechnical services on this project. If you
have any questions regarding this proposal, or need additional information, please do not
hesitate to contact us.
Sincerely,
HWA GEOSCIENCES INC.
C+� 1704
4sed GGO
I
STEVEN ELLIOTT GREENE
Steven E. Greene, L.G., L.E.G.
Senior Engineering Geologist
Vice President
Attachments:
Figure 1 Project Site & Vicinity Map
Figure 2 Project Route Alternatives
Oe AND o,9�'
Q 0�2
A .p 3sasa �
��ONAL
EXPIRES 08 / 18 / (��
Erik O. Andersen, P.E.
Geotechnical Group Manager
Renton Stonegate II Pre -Design GeoTech Rptnts 10 HWA GEOSCIENCES INC.
TOPOI map printed on 07/11/07 from "Washington.tpo" and -Untitled.""
122•11 Onn w nrnl w 111—., _ I.. ....._-- _--• _-. _ - -
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' V � HWAGEOSCIENCES INC.
PROJECT SITE & VICINTY MAP
PRELIMINARY GEOTECHNICAL REPORT
SEWER REPLACEMENT -ROUTE ALTERNATIVES
STONEGATE II -PHASE 1
v'
z
b
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FIGURE NO
2007-080
Viul HWAGEOSCIENCES INC.
I � Ex1sW9
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Force Min y
Attern3tive 13
s
Force Main
Alternative #3b
PROJECT ROUTE ALTERNATIVES
PRELIMINARY GEOTECHNICAL REPORT
SEWER REPLACEMENT -ROUTE ALTERNATIVES
STONEGATE II -PHASE I
RENTON. WASHINGTON
t
Ilea
FIGURE NO
PRO_iFCT NO
2007-080
Appendix B
APPENDIX B
Wetlands Technical Memorandum
ESA Adolfson
City of Renton
RothHill
Stonegate 11 Alternatives Analysis Report
539 Avenue NW
E A lA Adolf son
Suite 200shole
'
Seattle, WA 98107
206.789.9658
206.789.9684
memorandum
' date June 26, 2006
' to Scott Goss, Roth Hill Engineering Partners, LLC
from Lisa Adolfson, Ilon Logan
subject Summerwind/Stonegate Lift Station and Pipeline Project - Alternatives Analysis
Introduction
This technical memorandum was prepared as part of the preliminary evaluation phase for the Summerwind/
Stonegate Lift Station and Pipeline Project for the City of Renton. The purpose of our evaluation was to identify
' existing conditions that may influence the selection of an alignment for a new force main and siting of a new lift
station at the current Stonegate location. This memorandum summarizes the results of ESA Adolfson's literature
review and wetland and stream reconnaissance for three alternative force main alignments and lift station location.
Our evaluation consisted of a preliminary review of available literature and a reconnaissance -level field
investigation to identify the presence of wetland and streams. No wetland delineations or other site -specific
studies were conducted as part of this task.
' Project Description
The Summerwind/Stonegate Lift Station and Pipeline Project includes the following components:
' • Construction of a new lift station near the existing Stonegate lift station.
• Construction of a new force main between the new Stonegate lift station to the City's existing sewer
system along Field Avenue NE
' The project area is located in the northern portion of the City of Renton (Figure h). The project area is generally
bounded by May Creek to the north, NE Sunset Boulevard to the south, and 148 Avenue SE to the east. The
' three force main alternative alignments are generally centered around the Summerwind and Stonegate residential
developments and May Creek occurs to the north. Single-family residential development is the predominant land
use in the area.
Field Investigation
ESA Adolfson staff Lisa Adolfson and lion Logan conducted a field investigation of the proposed lift station
location and three alternative alignments on June 5, 2007. The on -site investigation of wetlands followed the
methods outlined by the Washington State Wetlands Identification and Delineation Manual (Ecology Publication
No. 96-94, March 1997), which is consistent with the methodology used to identify and define wetlands using the
1987 Corps of Engineers Manual. The reconnaissance was performed during the growing season after a period of
normal rainfall. Visual observations were made and soil samples were taken from existing utility easements and
right-of-way. No formal data plots were established.
Wetlands and Streams
' Wetlands and stream corridors in the City of Renton were preliminarily identified in the Critical Areas Inventory
(Jones & Stokes Associates, 1992). The inventory shows the main stem of May Creek north of the existing
Stonegate lift station and a tributary of May Creek extending south through the Stonegate development. A large
' scrub -shrub and emergent wetland is also mapped along the main stem of May Creek. The mapped wetland is
identified as "K-7" and is 142 acres in size. Field investigation confirmed the presence of this wetland and along
the main stem of May Creek and the south tributary.
' According to the Renton Municipal Code (RMC), May Creek is a Class 2 stream because it is a perennial or
intermittent salmonids-bearing water and is mapped on Figure Q4, Renton Water Class Map as a Class 2 stream
(RMC 4-3-050 L1). Class 2 streams in Renton have a minimum buffer width of 100 feet (RMC 4-3-050 L5).
Based upon field investigation, we observed that the main channel of May Creek is approximately five to eight
feet wide where it the crosses 148`h Avenue SE.
' The tributary of May Creek that extends south through the study area (NE 26" Street) is also mapped on the
Renton Water Class Map and is a Class 4 stream. Class 4 streams have a 35-foot minimum buffer width. This
tributary appears to be a seasonal channel with an estimated 5-feet width and was dry during the June site visit.
' Wetland K-7 is present on both sides of the 148`h Avenue SE as the May Creek main stem broadens into a
relatively flat topographic area. Scrub -shrub wetland vegetation is present, including Sitka willow (Salix
sitchensis), red alder (Alnus rubra) and reed canarygrass (Phalaris arzmdinacea). On the east side of 1481h
Avenue SE and north of the existing Stonegate station, the wetland boundary extends approximately 75 to 100
feet north of the edge of the maintained grass (Figure 1). Soil investigation in the southern portion of the wetland
(closest to the existing lift station) found sandy loam soils that are very brown (IOYR 2/2) and contain dark
' yellowish brown (10YR 3/4) mottles. Soils were moist but not saturated at the time of investigation, likely due to
lack of precipitation in the previous seven days. Wetland vegetation in the area sampled also contains Sitka
willow, reed canarygrass, Douglas spirea (Spiraea douglasii), and lady fern (Athyrium filix femina). According to
' the RMC, the wetland is considered a Category I wetland because it is greater than 10 acres in size and has three
or more vegetation classes, one of which is open water (RMC 4-3-050 M 1). The wetland also includes May
Creek, which contains listed salmonids, resulting in a Category I rating. Category I wetlands have a required
standard buffer of 100-feet (RMC 4-3-050 M6).
Permitting Considerations
' As described above, the existing Stonegate lift station is located in the vicinity of May Creek and wetland K-7.
Depending upon the limits of construction for the proposed new facility, it appears that construction activities
would not occur near May Creek or it's buffer. It is believed that the wetland boundary for wetland K-7 exists an
estimated 75 to 100 feet north of the edge of the mowed area at the site. From our understanding, it is likely that
' construction activities would not impact the wetland, and that buffer impacts may also be avoided. It is our
recommendation that a formal wetland boundary delineation be conducted at the site when the limits of lift station
construction are determined.
It is our understanding that the majority of each force main route would be constructed in existing road prisms.
Force Main Alternatives l and 2 would cross a tributary of May Creek in NE 261h Street. Force Main Alternative
3 crosses the same tributary of May Creek in the vicinity of SE 104`h Street. As mentioned above, this stream has
a 35-foot buffer according to Renton Municipal Code. To avoid impacting streams in the City of Renton,
trenchless technologies would need to be employed for the estimated 75-foot stream crossing width (this includes
35 foot buffer, 5 foot stream channel, and 35 foot buffer). If trenching this distance is not practical, review and
permitting under the City of Renton's critical areas ordinance would be required. It is our recommendation that a
survey be conducted once a preferred pipeline route is selected. Detailed field work would then be conducted to
flag the ordinary high water mark of the stream and to identify any other areas of concern or possible permitting
considerations.
Limitations
Within the limitations of schedule, budget, and scope -of -work, we warrant that this study was conducted in
accordance with generally accepted environmental science practices, including the technical guidelines and
criteria in effect at the time this study was performed, as outlined in the Methods section. The results and
conclusions of this report represent the authors' best professional judgment, based upon information provided by
the project proponent in addition to that obtained during the course of this study. No other warranty, expressed or
implied, is made.
— Force Main Alternative #1
— Force Main Alternative #2
Force Main Alternative #3
Gravity Sewer Improvements
Existing Sewer Interceptor
.1
Proposed
Stonegate II - �a
Lift Station
• Existing
Stonegate
Lift Station
Gravity
y Sewer
ti
� •�J i M • : 1� F 'v
Improvements ri 0 144 1
dt_
00 • SE t D2nis� • t
- • •• Force Main
�` ` Existing L Itemative #2 •
s Summerwind 1i
` Force Main Lift Station
�} Alternative #1
rIr
Existing
Gravityc •
Sewer
a /_ .. a . F ? APr
a. i
Existing
Sew ' >
r to
sl
Aft-
Y$
Appendix C
APPENDIX C
Construction Cost Estimates
' City of Renton
RothHill
%---� Stonegate 11 Alternatives Analysis Report
City of Renton
Stonegate II Lift Station
Preliminary (Pre-30%) Opinion of Probable Construction Costs
All Costs in Year 2008 Dollars
Prepared by: ELB
Modified by: TF
Last Updated: 9/5/2007
ITEM
DESCRIPTION
QUANTITY
UNIT
UNIT
COST
TOTAL COST
1
Mobilization (Not to Exceed 8% of Contract Total)
1
LS
$75,000
$75,000
2
Temporary Erosion & Sedimentation Control Facilities
1
LS
$20,000
$20,000
3
Filter Fabric Fence
425
LF
$8
$3,400
4
Site Clearing and Grading
1
LS
$15,000
$15,000
5
Temporary Shoring and Dewatering for Lift Station
1
LS
$160,000
$160,000
6
Excavation and Backfill
1
LS
$60,000
$60,000
7
12-foot Diameter Precast Wet Well
1
LS
$50,000
$50,000
8
_
Precast Concrete Valve and Flow Meter Vault
1
_
LS
$32,000
$32,000
9
Concrete Overflow Storage Vault
1
LS
$125,000
$125,000
10
Submersible Sewage Pumps and Motors
3
EA
$25,000
$75,000
11
Lift Station Piping
1
LS
$28,000
$28,000
12
Wet Well Accessories
1
LS
$10,000
$10,000
13
12-foot Diameter Safety Grating
1
LS
$8,000
$8,000
14
Wet Well Coatings _
1
LS
$12,000
$12,000
15
Valve Vault Coatings
1
LS
$7,000
$7,000
16
Overflow Storage Vault Coatings
1
LS
$24,000
$24,000
17
Convert Existing Stonegate Wet Well to Gravity Manhole
1
LS
$5,500
$5,500
18
Control Building
280
SF
$300
$84,000
19
Control Building Plumbing - Roof Drains / Footing Drains
1
LS
$8,000
$8,000
20
Mechanical Work
1
LS
$12,000
$12,000
21
Electrical Work
1
LS
$85,000
$85,000
22
Instrument and Control System
1
LS
$120,000
$120,000
23
Alarm/SCADA/Telemetry System
1
LS
$20,000
$20,000
24
Testing and Startup Services
1
LS
$12,500
$12,500
25
Standby Generator Set
1
EA
_
$65,000
$65,000
26
Trench Shoring Systems
100
LF
$60
$6,000
27
Ductile Iron Sewer Fittings
2000
LB
$4
$8,000
28
Clay Dams
2
EA
$1,500
_
$3,000
_ 29
Heat Shrinkable Manhole Wrap
1
EA
$4,000
$4,000
30
1-Inch Water Service w/ Backflow Preventor, Hot -Box, Yard Hydrant
1
EA
$4,000
$4,000
31
Foundation Gravel (As Required)
50
TON
$25
$1,250
32
_
Quarry Spalls (As Required)
75
TON
$30
$2,250
33
Crushed Surfacing (As Required)
60
TON
$25
_
$1,500
34
Asphalt Concrete Patch
70
SY
$60
$4,200
35
Asphalt Concrete Pavement for Driveway
40
TON
$250
$10,000
36
Miscellaneous Concrete Work
1
LS
$6,000
$6,000
37
Existing Stonegate Lift Station Abandonment
1
LS
$10,000
$10,000
38
Existing Summerwind Lift Station Abandonment
1
LS
$16,000
$16,000
39
Landscaping and Surface Restoration
_
1
LS
$32,000
$32,000
Total
Sales Tax @ 8.9%
$1,224,600
$109,000
Construction Cost with Sales Tax
Contingency @ 15%
$1,333,600
$200,000
Total Probable Construction Cost
$1,533,600
F:\0015\00018.000\Reports\Final Engineering Report\Appendix C - Stonegate 11 LS prelim costs 090407.x1s
APPENDIX C - Opinion of Probable Construction Cost
City of Renton Prepared by:
Stonegate II Route Analysis Edited by:
Preliminary Opinion of Probable Construction Costs Last Updated
All Costs in Year 2008 Dollars
Summerwind Gravity Rawar Oltarnnfiva _ Anon Rid
BPW
TF
11 /12/2007
Item
Description
Quantity
Unit
Unit Cost
Total Cost
1
8-Inch Diameter PVC Sewer Pipe, (Under 10' Depth)
245
LF
$125.00
$30,625
2
Rechannel Existing Manhole
1
EA
$1,000.00
$1,000
3
Utility Relocation
1
LS
$10,000.00
$10,000
4
1 1/2 " Deep Asphalt Overlay Class 'B'
250
SY
$10.00
$2,500
Total
$44,125
Sales Tax @ 8.9%
$3,875
Construction Cost with Sales Tax
$48,000
Contingency @ 15%
$7,200
Total Probable Construction Cost
$55,200
Summerwind Gravitv Sewer Alternative-TrPnchlPsc Cnnsfmrtinn twnni
Item
Description
Quantity
Unit
Unit Cost
Total Cost
1
8-Inch Diameter HDPE Sewer Pipe, Directional Drill (245 LF)
1
LS
$49,000.00
$49,000
2
48-Inch Diameter Sanitary Sewer Manhole
1
EA
$4,000.00
$4,000
3
Rechannel Existing Manhole
1
EA
$1,000.00
$1,000
4
1 1/2 " Deep Asphalt Overlay Class 'B'
250
SY
$10.00
$2,500
Total
$56,500
Sales Tax @ 8.9%
$5,000
Construction Cost with Sales Tax
$61,500
Contingency @ 15%
$9,200
Total Probable Construction Cost
$70,700
Force Main Alternative 1
Item
Description
Quantity
Unit
Unit Cost
Total Cost
1
8-Inch Diameter PVC Force Pipe, ROW
3195
LF
$105.00
$335,475
2
Bore and Jack - Stream Crossing (60 LF)
1
LS
$40,000.00
$40,000
3
8-Inch Diameter PVC Force Pipe, Easement
245
LF
$85.00
$20,825
4
1 1/2 " Deep Asphalt Overlay Class 'B'
9800
SY
$10.00
$98,000
Total
$494,300
Sales Tax @ 8.9%
$44,000
Construction Cost with Sales Tax
$538,300
Contingency @ 15%
$80,700
Total Probable Construction Cost
$619,000
Force Main Alternative 2
Item
Description
Quantity
Unit
Unit Cost
Total Cost
1
8-Inch Diameter PVC Force Pipe, ROW
3455
LF
$105.00
$362,775
2
Bore and Jack - Stream Crossing (60 LF)
1
LS
$40,000.00
$40,000
3
1 1/2 " Deep Asphalt Overlay Class 'B'
10200
SY
$10.00
$102,000
Total
$504,775
Sales Tax @ 8.9%
$44,925
Construction Cost with Sales Tax
$549,700
Contingency @ 15%
$82,500
Total Probable Construction Cost
$632,200
F:\0015\00018.000\Reports\Final Engineering Report\Appendix C - Pipe Costs 113007.xls
APPENDIX C - Opinion of Probable Construction Cost
City of Renton Prepared by:
Stonegate II Route Analysis Edited by:
Preliminary Opinion of Probable Construction Costs Last Updated
All Costs in Year 2008 Dollars
Force Main Alternative 3A
BPW
TF
11 /12/2007
Item
Description
Quantity
Unit
Unit Cost
Total Cost
1
8-Inch Diameter PVC Force Pipe, ROW
3105
LF
$105.00
$326,025
2
8-Inch Diameter PVC Force Pipe, Easement
780
LF
$85.00
$66,300
3
Bore and Jack - Stream Crossing (60 LF)
1
LS
$40,000.00
$40,000
4
1 1/2 "Deep Asphalt Overlay Class'B'
8400
SY
$10.00
$84,000
Total
$516,325
Sales Tax @ 8.9%
$0.09
$45,975
Construction Cost with Sales Tax
$562,300
Contingency @ 15%
$0.15
$84,300
Total Probable Construction Cost
1
$646,600
Force Main Alternative 3B
Item
Description
Quantity
Unit
Unit Cost
Total Cost
1
8-Inch Diameter PVC Force Pipe, ROW
2830
LF
$105.00
$297,150
2
8-Inch Diameter PVC Force Pipe, Easement
1095
LF
$85.00
$93,075
3
Bore and Jack - Stream Crossing (60 LF)
1
LS
$40,000.00
$40,000
4
1 1/2 "Deep Asphalt Overlay Class'B'
8500
SY
$10.00
$85,000
Total
$515,225
Sales Tax @ 8.9%
$45,875
Construction Cost with Sales Tax
$561,100
Contingency @ 15%
$84,200
Total Probable Construction Cost
$645,300
Field Ave Intercentnr Alternative _ t1non Cnt
Item
Description
Quantity
Unit
Unit Cost
Total Cost
1
15-Inch Diameter PVC Sewer Pipe, ROW (Under 10' Depth)
90
LF
$195.00
$17,550
2
12-Inch Diameter PVC Sewer Pipe, ROW (Under 10' Depth)
880
LF
$185.00
$162,800
3
48-Inch Diameter Sanitary Sewer Manhole
6
EA
$4,000.00
$24,000
4
Rechannel Existing Manhole
1
EA
$1,000.00
$1,000
5
Reconnect Existing PVC Side Sewers
21
EA
$1,100.00
$23,100
6
11 1/2 " Deep Asphalt Overlay Class'B'
3250
SY
$10.00
$32,500
Total
$260,950
Sales Tax @ 8.9%
$23,250
Construction Cost with Sales Tax
$284,200
Contingency @ 15%
$42,600
Total Probable Construction Cost
$326,800
F:\0015\00018.000\Reports\Final Engineering Report\Appendix C - Pipe Costs 113007.xls
APPENDIX C - Opinion of Probable Construction Cost
City of Renton Prepared by:
Stonegate II Route Analysis Edited by:
Preliminary Opinion of Probable Construction Costs Last Updated
All Costs in Year 2008 Dollars
Field Ave Interceptor Alternative - Trenchless
BPW
TF
11 /12/2007
Item
Description
Quantity
Unit
Unit Cost
Total Cost
1
16-Inch O.D. HDPE Sewer Pipe - Pipe Burst
90
LF
$170.00
$15,300
2
14-Inch O.D. HDPE Sewer Pipe - Pipe Burst
880
LF
$150.00
$132,000
3
48-Inch Diameter Sanitary Sewer Manhole
7
EA
$4,000.00
$28,000
4
Reconnect Existing PVC Side Sewers
21
EA
$1,100.00
$23,100
5
1 1/2 " Deep Asphalt Overlay Class'B'
500
SY
$10.00
$5,000
Total
$203,400
Sales Tax @ 8.9%
$18,100
Construction Cost with Sales Tax
$221,500
Contingency @ 15%
$33,200
Total Probable Construction Cost
$254,700
Sunset Interceptor Alternative - Onen Cut
Item
Description
Quantity
Unit
Unit Cost
Total Cost
1
12-Inch Diameter PVC Sewer Pipe, ROW (Under 10' Depth)
120
LF
$185.00
$22,200
2
15-Inch Diameter PVC Sewer Pipe, ROW (Under 10' Depth)
620
LF
$195.00
$120,900
3
15-Inch Diameter PVC Sewer Pipe, ROW (10-15' Depth)
670
LF
$225.00
$150,750
4
18-Inch Diameter PVC Sewer Pipe, ROW (10-15' Depth)
595
LF
$235.00
$139,825
5
48-Inch Diameter Sanitary Sewer Manhole
12
EA
$4,000.00
$48,000
6
Remodel Existing Manhole
3
EA
$1,000.00
$3,000
7
Reconnect Existing PVC Side Sewers
3
EA
$1,100.00
$3,300
8
1 1/2 " Deep Asphalt Overlay Class'B'
5100
SY
$10.00
$51,000
9
Remove and Replace Existing Concrete Sidewalk
370
LF
$75.00
$27,750
10
lRemove and Replace Existing Concrete Curb and Gutter
200
SY
$75.00
$15,000
Total
$581,725
Sales Tax @ 8.9%
$51,775
Construction Cost with Sales Tax
$633,500
Contingency @ 15%
$95,000
Total Probable Construction Cost
$728,500
Sunset Interceptor Alternative - Trenchless
Item
Description
Quantity
Unit
Unit Cost
Total Cost
1
18-Inch Diameter PVC Sewer Pipe, ROW (10-15' Depth)
65
LF
$235.00
$15,275
2
14-Inch O.D. HDPE Sewer Pipe - Pipe Burst
120
LF
$165.00
$19,800
3
16-Inch O.D. HDPE Sewer Pipe - Pipe Burst
1290
LF
$185.00
$238,650
4
20-Inch O.D. HDPE Sewer Pipe - Pipe Burst
530
LF
$200.00
$106,000
5
48-Inch Diameter Sanitary Sewer Manhole
14
EA
$4,000.00
$56,000
6
Reconnect Existing PVC Side Sewers
1
EA
$1,100.00
$1,100
7
1 1/2 " Deep Asphalt Overlay Class'B'
700
SY
$10.00
$7,000
8
Remove and Replace Existing Concrete Sidewalk
40
LF
$75.00
$3,000
9
Remove and Replace Existing Concrete Curb and Gutter
25
SY
$75.00
$1,875
Total
$448,700
Sales Tax @ 8.9%
$39,900
Construction Cost with Sales Tax
$488,600
Contingency @ 15%
$73,300
Total Probable Construction Cost
$561,900
F:\0015\00018.000\Reports\Final Engineering Report\Appendix C - Pipe Costs 113007.xis
APPENDIX C - Opinion of Probable Construction Cost
City of Renton Prepared by:
Stonegate II Route Analysis Edited by:
Preliminary Opinion of Probable Construction Costs Last Updated
All Costs in Year 2008 Dollars
Pr000sed Gravitv Sewer Alternativp 1
BPW
TF
11 /12/2007
Item
Description
Quantity
Unit
Unit Cost
Total Cost
1
8-Inch Diameter PVC Sewer Pipe, ROW (Under 10' Depth)
1165
LF
$155.00
$180,575
2
8-Inch Diameter PVC Sewer Pipe, ROW (10-15' Depth)
1175
LF
$180.00
$211,500
3
8-Inch Diameter PVC Sewer Pipe, Easement (Under 10' Depth)
290
LF
$125.00
$36,250
4
8-Inch Diameter PVC Sewer Pipe, Easement (10-15' Depth)
180
LF
$150.00
$27,000
5
12-Inch Diameter PVC Sewer Pipe, Easement (Under 10' Depth)
370
LF
$135.00
$49,950
6
12-Inch Diameter PVC Sewer Pipe, Easement (10-15' Depth)
270
LF
$160.00
$43,200
7
48-Inch Diameter Sanitary Sewer Manhole
16
EA
$4,000.00
$64,000
8
6-Inch Diameter PVC Side Sewer
40
EA
$1,100.00
$44,000
9
11 1/2 " Deep Asphalt Overlay Class 'B'
6530
SY
$10.00
$65,300
Total
$721 775
Sales Tax @ 8.9%
$64,225
Construction Cost with Sales Tax
$786,000
Contingency @ 15%
$117,900
Total Probable Construction Cost
$903,900
Pronesad Gravitv Spwpr Altprnativa 9
Item
Description
Quantity
Unit
Unit Cost
Total Cost
1
8-Inch Diameter PVC Sewer Pipe, ROW (Under 10' Depth)
1070
LF
$155.00
$165,850
2
8-Inch Diameter PVC Sewer Pipe, ROW (10-15' Depth)
865
LF
$180.00
$155,700
3
8-Inch Diameter PVC Sewer Pipe, ROW (15-20' Depth)
320
LF
$210.00
$67,200
4
8-Inch Diameter PVC Sewer Pipe, Easement (Under 10' Depth)
665
LF
$125.00
$83,125
5
8-Inch Diameter PVC Sewer Pipe, Easement (10-15' Depth)
260
LF
$150.00
$39,000
6
8-Inch Diameter PVC Sewer Pipe, Easement (20-25' Depth)
220
LF
$200.00
$44,000
7
48-Inch Diameter Sanitary Sewer Manhole
18
EA
$4,000.00
$72,000
8
6-Inch Diameter PVC Side Sewer
40
EA
$1,100.00
$44,000
9
11 1/2 " Deep Asphalt Overlay Class'B'
6230
SY
$10.00
$62,300
Total
$733,175
Sales Tax @ 8.9%
$65,225
Construction Cost with Sales Tax
$798,400
Contingency @ 15%
$119,800
Total Probable Construction Cost
$9181200
1. All open -trench pipe costs include cost of mobilization, materials, excavation, shoring, TESC, surface restoration, and trench
patching. Depths are based on review of proposed pipe sections to be replaced.
2. All pipe bursting costs include cost of mobilization,materials, excavation, shoring, TESC, surface restoration, and trench
patching. Depths are based on review of proposed pipe sections to be added or replaced.
3. Manhole depths were determined by reviewing existing contours. The price of extra depth manholes is included in the cost per
manhole.
4. Side sewer connections are assumed for every building lot adjacent to the proposed sewer at an average length of 30 feet of 6"
PVC per side sewer (10' average depth per connection). Sunset Interceptor side sewer connections were were determined by
review of television inspection video for existing side sewer locations.
5. Half -width asphalt overlay was assumed for Sunset Interceptor Improvements. Full width asphalt overlay was assumed for all
other open cut sewer replacement in ROW.
6. Directional drilling costs based on national survey conducted by Trenchless Technologies.
F:\0015\00018.000\Reports\Final Engineering Report\Appendix C - Pipe Costs 113007.x1s