HomeMy WebLinkAbout19- Task Order 2 - DOWL, LLC - Westridge Stormwater Treatment Project V 9�
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EXHIBIT A TO PROFESSIONAL SERVICES MASTER TASK ORDER AGREEMENT
TASK ORDER#2—WESTRIDGE STORMWATER TREATMENT PROJECT
Issued under the authority of Professional Services Agreement between the City of Bozeman (City)and
DOWL, LLC(Contractor)for a range of professional and technical services, including, but not necessarily limited
to, engineering design, preparation of construction documents, project bidding,and construction administration
services for various stormwater improvement projects, as requested by the City through the issuance of
individual and consecutively numbered Task Orders on an as-needed basis.
This Task Order is dated October_jLA, 20 between the City and the Contractor.
1.0 PROJECT REPRESENTATIVES:
■ City: Kyle Mehrens,Stormwater Program Coordinator
■ Contractor: Wade Irion, Water Practice Lead
2.0 SCOPE OF WORK:
■ Attached Exhibit A-Scope of Services for the Westridge Stormwater Treatment Project
3.0 COMPENSATION:
■ The City shall reimburse the Contractor on a Lump Sum basis not to exceed$21,980.
■ The Contractor shall invoice once monthly for services provided in the prior month.
4.0 WORK GOVERNANCE:
■ The provisions of the Professional Services Master Task Order Agreement and any Special Terms and
Conditions and Exhibits or Attachments to this Task Order shall govern the Work.
5.0 SIGNATURES:
IN WITNESS WHEREOF,the parties authorized to commit resources of the companies have executed this Task Order:
CITY OF BOZEMAN, MONTANA(CITY) DOWL, LLC(CONTRACTOR)
By:Andrea Surratt By:Wade Irion
Title: City Manager Title:Water Practice Lead
Signature: Signature:
APPROVED AS TO FORM:
By:Greg Sullivan
Title:City Attorney
Signature:
Stormwater Design Professional Services Agreement Page 1
Task Order #2
Exhibit A - Scope of Services
Westridge Stormwater Treatment Project
Introduction
The City of Bozeman (City)would like to add water quality treatment to the Westridge Drive storm drain
immediately upstream of the outfall near the intersection of Westridge Drive and Overbrook Drive (see Figure
1). Installation of the treatment structure (assumed to be a Contech CDS unit) is planned to be in one of the two
alternate configurations/locations listed below.This scope of services describes the tasks to be completed by
DOWL and the deliverables that will be provided upon project completion.
• Alternative 1:A junction manhole within the boulevard and in the approximate location of the first
manhole upstream of the outfall
• Alternative 2:A combination inlet/junction manhole at the location of the first inlet south of the
alternative 1 location.
Scope of Services
Task 1. Hydrology and Hydraulics
DOWL will perform hydrologic modeling and hydraulic routing of precipitation events for the existing Westridge
Drive storm drain from the intersection of Westridge Drive and Arnold Street to the outfall near the intersection
of Overbrook Drive and Westridge Drive(see Figure 1).The total approximate contributing basin area is
anticipated to be 5 to 10 acres.
Hydrologic analyses will be based on precipitation hyetographs recently developed by DOWL for use on other City
of Bozeman Stormwater Division projects.The source of this data is the 2017 revision of Appendix B,Table 61 of
the MDT Hydrology manual for the Bozeman Airport precipitation gage. Hydraulic routing will be completed using
the program Autodesk Storm and Sanitary Analysis(ASSA).The results of this modeling will be used to size a water
quality treatment structure for the Westridge Drive storm drain. We understand that the water quality event is
somewhat flexible and is often driven by the size of the unit that is realistic given other project constraints. The
City believes that a 5-ft diameter Contech CDS water quality structure may be the upper limit for treatment
structure size at this location given site constraints. The ASSA modeling will provide estimates of peak flows for
the water quality storm as well as more severe precipitation events;these peak flows will be used to determine
the final structure size based on the Washington State Department of Ecology general use level designation for
pretreatment of total suspended solids.
The Westridge storm drain discharges to private stormwater ponds with an outfall to Figgens Creek in the
northwest quadrant of the intersection of Westridge Drive and Overbrook Drive. Detailed analysis and design
storm routing through the ponds will not be completed; rather, a limited analysis of the ponds will be completed
to estimate the pond water surface elevation for various precipitation events. This is anticipated to be an
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Task Order#2, Exhibit A—Scope of Services
Westridge Stormwater Treatment Project
important factor in the design, as the water surface elevation in the ponds is the tailwater elevation for the
treatment unit and may control certain aspects of the design of the treatment structure.
Task 2. Utility Locates and Survey
Survey base mapping will be developed for the project corridor. Services performed under this task will include
requesting utility locates,survey of utilities,and topographic survey of the project vicinity. DOWL will develop and
submit a utility locate request and will survey the locations of utilities within the project corridor. Rim elevation
survey and measure-downs to pipe inverts will be completed to document existing pipe elevations and sizes for
use in hydraulic analyses. The survey will be completed in NAD83 state plane coordinates and using the vertical
datum NAVD88.Survey within the private storm water ponds will be limited and may not completely characterize
the existing depth of the ponds. The pond outlet pipe elevations will be surveyed for use in hydraulic analyses.
DOWL will notify the City of Bozeman in advance of the utility locates and survey to obtain permission to enter
private property in the vicinity of the project.
Task 3. Construction Documents and Design Documentation
Services performed under this task will include development of final construction drawings stamped and sealed
by an Engineer licensed in the State of Montana and a design memo documenting the basis of the design.
Once the size of the structure has been determined through hydrologic and hydraulic analysis, an alternatives
analysis will be completed to estimate the relative construction costs for Alternative 1 and Alternative 2 and
determine the most cost-effective location for the treatment structure.Alternative 1 would include installation of
the treatment structure at the existing junction manhole location; whereas, Alternative 2 would include
installation of a combination manhole at the location of the nearby inlet south of the Alternative 1 location. The
alternatives analysis (-15% design submittal) deliverable will consist of 1) a brief alternatives analysis summary
memorandum,2)a plan view depicting the two alternatives and existing utilities mapped through the project,and
3)the estimated construction cost of each alternative.
The survey base mapping and results of the hydraulic analyses will be used to determine the final elevations for
the treatment unit. Pipe elevations at the location of the treatment structure will be based on the measure downs
to existing pipe inverts. Given the recency of this storm drainage infrastructure and the existing size of the pipes,
pipe stubs and dissimilar pipe couplings to accommodate potential future increases in pipe sizes are not
anticipated. Modifications to the existing pipes will be depicted in the plans. It is assumed that the existing outfall
pipe will be able to be modified and reused without impacting the adjacent stormwater pond. It is anticipated
that construction may impact several panels of the adjacent sidewalk, the driveway to the west of the current
junction manhole,curb and gutter in the vicinity of the existing inlet structure,and asphalt pavement. Details will
be provided in the plans for replacement or restoration of these features if they will be impacted during
construction.
Given the proximity of the treatment structure to the private stormwater ponds and Figgens Creek, a portion of
the manhole may be below the groundwater elevation. DOWL will evaluate buoyant forces and provide a factor
of safety of at least 2.0 to resist floatation.
Construction Drawing submittals will be made at 85% design and final design. A design review meeting will be
conducted after the 85% submittal. Final construction drawings will include a bid quantities sheet itemized with
project materials,type, and quantity.
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Task Order#2, Exhibit A—Scope of Services
Westridge Stormwater Treatment Project
Task 4. Floodplain Permitting
The project is within the mapped extents (Zone AE) of the base flood as shown on FEMA map number
30031C0818D;therefore, a floodplain development permit will be required for construction. DOWL will prepare
the permit using the Montana Joint Application. The Westridge Stormwater Treatment Project will include
restoration of ground surface (e.g., boulevard, pavement, sidewalks, curb and gutter) in the vicinity of the
treatment manhole to the pre-project conditions and will therefore have no adverse impact on the floodplain.
The project and any impacts will be described qualitatively, and it is assumed that a hydraulic model will not be
necessary for development of the permit.
Task 5. Plant Species List
DOWL will provide a species list of native plants that could be planted within and around the private storm water
ponds downstream of the outfall. The species list will be customized with plants appropriate for the area of
Bozeman, MT and will include what the planting conditions should be for each species (e.g., below the ordinary
high-water mark but in water less than 3 feet, within 12-inches above the ordinary high water, greater than 12
inches above the ordinary high water).Guidelines on appropriate plant material sizes,timing of planting,and plant
protection will also be provided. DOWL will coordinate with the City of Bozeman in establishing the objectives of
the plantings (i.e. herbaceous or woody plant types or both, any aesthetic objectives, planned approach to
management or maintenance of the ponds, etc.). The species list will be provided in the format of a technical
memorandum that could be handed off from the City of Bozeman to the home owner's association.
Schedule and Compensation
Survey will be completed in the fall of 2019. Final plans will be completed during the winter of 2019 to facilitate
bidding for spring 2020 construction.This is based on notice to proceed in October,2019.Table 1 outlines DOWL's
fee for the services included.
Table 1 Compensation
Task Description Estimated
Fee
Task 1. Hydrology and Hydraulics $ 7,560.00
Task 2. Utility Locates and Survey $ 3,600.00
Task 3. Construction Documents and Design Documentation $ 9,245.00
Task 4. Plant Species List $ 1,575.00
Total $21,980.00
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Task •- • ••- of Services
Westridge StormwaterProject
Figure 1 • of Existing Westridge
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