HomeMy WebLinkAbout03-09-20 City Commission Packet Materials - C16. TO3 to PSA w DOWL LLC for Stormwater DesignCommission Memorandum
REPORT TO: Honorable Mayor and City Commission
FROM: Kyle Mehrens, Stormwater Program Coordinator
Mitch Reister, Director of Public Works
SUBJECT: Task Order #3 under the authority of a previously executed Stormwater Design
Professional Services Master Task Order Agreement with DOWL, LLC
MEETING DATE: March 9, 2020
AGENDA ITEM TYPE: Consent
RECOMMENDATION: Authorize the Interim City Manager to sign Task Order #3 under the
authority of a previously executed Stormwater Design Professional Services Master Task Order
Agreement with DOWL, LLC.
BACKGROUND: In 2019, the Stormwater Division advertised a Request for Qualifications for
on-call planning, engineering, and construction services. Staff: (1) selected DOWL, LLC
(Consultant), (2) negotiated a three-year Master Task Order Professional Services Agreement
(PSA) with the Consultant, and (3) delivered the PSA to the Commission for approval and City
Manager ratification on September 16, 2019. Staff utilizes the Consultant as projects arise, and
funding is available. Attached is Task Order #3, ready for the Commission’s consideration.
Task Order #3 contracts with the Consultant for the preliminary design of the City’s Downtown
Trunk Line Rehabilitation Project (Project). The Project includes the rehabilitation of multiple
historical stormwater pipes between Main St. and Mendenhall St. (Attachment B). The pipes are
made of antiquated materials and convey runoff from over 300-acres. A structural failure in the
existing system could result in costly repairs and public safety risks.
Task Order #3 includes a precipitation analysis, existing system evaluation, hydrologic and
hydraulic analysis, alternatives evaluation, and a design report. Once complete, Staff will use the
design report to select the most suitable rehabilitation option and generate an additional Task
Order for final design and construction services, such as inspection, testing, and survey.
UNRESOLVED ISSUES: None
ALTERNATIVES: As suggested by the Commission.
FISCAL EFFECTS: The Commission approved the Downtown Trunk Line Rehabilitation
(Phase 1) with the FY20 Budget, totaling $400,000. The Downtown Trunk Line Rehabilitation
(Phase 2) is an FY21 Capital Improvement Project, totaling $350,000. Staff plans to design and
construct the Projects jointly, as it is more cost-effective; however, Staff will not bid the
construction portion of the Project until the Commission adopts the FY21 Budget.
Task Order #3 is $75,400, which staff found to be commensurate with the proposed services.
Attachments: Attachment A: Professional Services Master Task Order Agreement
Attachment B: Task Order #3 - Downtown Stormwater Mains Rehabilitation
Evaluation
Report compiled on: February 24, 2020
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Stormwater Design Professional Services Agreement Page | 1
EXHIBIT A TO PROFESSIONAL SERVICES AGREEMENT
TASK ORDER #3 – DOWNTOWN STORMWATER MAINS REHABILITATION EVALUATION
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 ____, 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 - Downtown Stormwater Mains Rehabilitation Evaluation
3.0 COMPENSATION:
The City shall reimburse the Contractor on a Time & Materials basis not to exceed $75,400.
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: Dennis Taylor By: Wade Irion
Title: Interim City Manager Title: Water Practice Lead
Signature: ___________________________ Signature: __________________________
APPROVED AS TO FORM:
By: Greg Sullivan
Title: City Attorney
Signature: ___________________________
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Page 1
Task Order #03
Exhibit A – Scope of Services
Downtown Stormwater Mains Rehabilitation
Evaluation
Introduction
As identified in the City of Bozeman (City) Stormwater Capital Improvement Plan, the City would like to move
forward with Phase 1 of the Downtown Trunk Line Rehabilitation Project. The alleyway stormwater mains were
constructed in the early 1900’s and is a critical component of the downtown stormwater conveyance system. The
stormwater mains consist of 36-inch and 30-inch diameter clay tile pipe with numerous active and inactive
building service line penetrations. This phase of the project includes the evaluation of the downtown stormwater
conveyance system and rehabilitation design alternatives of the stormwater mains within the alleyway between
Main Street and Mendenhall Street, beginning at N. Rouse Ave and extending west to N. Tracy Ave, see attached
Exhibit 1. The portion of the stormwater main within the N. Rouse Ave. right-of-way will be replaced by the
Montana Department of Transportation (MDT) as part of their Rouse Ave Reconstruction project currently under
construction.
The first task is to complete a precipitation analysis and develop design storm events representative of Bozeman’s
climate. This information will form the basis for all analysis and design to follow. It is anticipated that the resulting
design storm events will be incorporated into future updates to the City’s stormwater design standards. The
second task is a survey and condition evaluation of the existing stormwater mains and manholes. The third task is
a hydrologic analysis of stormwater runoff within the contributing drainage and review of the hydraulic capacity
of the existing alleyway stormwater main. The fourth task is to complete an evaluation of rehabilitation
alternatives for the downtown alleyway stormwater storm sewer trunk line. Each project task is further described
in the Scope of Services section below. The rehabilitation evaluation associated with this project will be used to
guide development of construction documents to improve the downtown stormwater mains in subsequent task
orders/projects.
Scope of Services
Task 1. Precipitation Analysis
Precipitation frequency analysis for Bozeman recently completed by DOWL under contract with the Montana
Department of Transportation is based on National Climatic Data Center (NCDC) gaging station data at Bozeman
Gallatin Field (cooperative network ID 240622), located in Belgrade, MT (period of record from 01/08/1948 to
12/31/2013). The results of this study are published in Appendix B of the MDT Hydrology Manual and currently
represent the best available precipitation frequency data for Bozeman, MT. An expanded analysis building on this
previous work will be beneficial in the evaluation and rehabilitation design of the downtown alleyway stormwater
main. This analysis will also be beneficial to the City for use on other storm drainage infrastructure improvement
projects throughout the City of Bozeman. Precipitation analyses that will be completed are:
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Task Order #03, Exhibit A – Scope of Services
Downtown Stormwater Mains Rehabilitation Evaluation
Page 2
· Comparative analysis of MSU ORSL data to MDT Hydrology Appendix B data: Raw precipitation data is
available from the Optical Remote Sensor Laboratory (ORSL) at Montana State University (MSU) for the
period of record from 01/06/2005 to current. DOWL will analyze this data and compare it to data
collected for the Bozeman Gallatin Field precipitation gage to confirm the representativeness of the
Bozeman Gallatin Field data for use in the City of Bozeman. MSU ORSL data is not currently published in
a comprehensive, downloadable format on the ORSL website and does not appear to be readily
accessible; it is assumed that the ORSL data can be obtained by the City for use in the study with
coordination of necessary technical data provided by DOWL.
· Develop water quality storm depth for the 6-month, 24-hour event: Review available precipitation data
and perform a precipitation frequency analysis to estimate the total storm depth for the 6-month, 24-
hour storm (i.e. the storm that has the probability of being equaled or exceeded twice annually, on the
long-term average). DOWL will also evaluate this storm relative to the industry accepted rule-of-thumb
to treat the first 0.5 inch of runoff. This analysis may be completed using the MSU ORSL data or the
NCDC Bozeman Gallatin Field data, depending on which is deemed most appropriate.
· Develop synthetic storm hyetographs: Develop a 24-hour synthetic storm precipitation hyetograph using
nested rainfall intensities for each recurrence interval of interest from 2 years to 100 years using the
values published in the MDT Hydrology Appendix B.
· Compile actual storm hyetographs for a variety of recurrence interval storms: Use of a synthetic design
storm is appropriate for evaluating controlling runoff for a range of basin sizes and times of
concentration; however, for larger basins (such as that of downtown Bozeman tributary to the Rouse
Ave. storm drain outfall), the use of a synthetic nested storm may be overly conservative. Therefore,
DOWL will develop a “family” of actual storm events in the 5-year to 10-year recurrence interval range
and including both short-duration, high-intensity events as well as longer-duration, low intensity events
to determine a controlling storm for design of the current project. More severe actual storm
hyetographs will also be compiled to evaluate system performance under these more severe storms,
such as the 25-year and 50-year events. We anticipate much of the actual storm data will need to be
based on the Bozeman Gallatin Field gage data, due to its significantly longer period of record. Gage
data for Bozeman Gallatin Field is hourly data and will require manipulation to generate a hyetograph at
a more refined time step (i.e. 5-minute, 10-minute, 15-minute, etc..). Data from the MSU ORSL is
collected at a more frequent time interval and will therefore also be reviewed for this purpose.
DOWL will incorporate the methodologies and results of these analyses into the Design Report (Task 5). In
addition, DOWL will develop a stand-alone memorandum to document procedures for applying the water quality
storm, synthetic storms, and actual storm hyetographs in the design of storm water infrastructure throughout
Bozeman. One meeting is planned with the City of Bozeman to discuss preliminary results of the precipitation
analyses.
Task 2. Existing System Evaluation
DOWL will complete an evaluation and inventory of the existing stormwater mainline system in the alleyway
between N. Rouse Ave. and N. Tracy Ave.
· Survey & Utility Locates: A limited topographical survey will be completed for the project corridor. The
topographical survey will consist of rim elevation on stormwater manholes of the alleyway mainline as
well as the nearest manhole for incoming storm drains, measure-downs to pipe inverts and utilities within
a 25’ radius of the stormwater manholes. The survey will be completed in NAD83 state plane horizontal
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Task Order #03, Exhibit A – Scope of Services
Downtown Stormwater Mains Rehabilitation Evaluation
Page 3
datum and NAVD88 vertical datum. The survey is intended to provide the necessary horizontal and vertical
data to evaluate the hydraulic capacity of the stormwater main and identify potential utility conflicts if
excavation is necessary during construction of the project.
· Stormwater Service Mapping: DOWL will review the stormwater main inspection videos and supplemental
information, supplied by the City, to identify the stormwater service locations. The active stormwater
service locations will be shown on the construction drawings with an assumed building connection
identified. Additionally, a field investigation will be completed to visually identify exterior stormwater
building connections.
· Stormwater Manhole Condition Assessment: DOWL will complete a condition assessment of the
stormwater manholes identified below. As part of the condition assessment, DOWL will enter the
manholes using OSHA confined space entry procedures and document the identified visual manhole
deficiencies. It is assumed that minor traffic control will be necessary consisting of signage and one
personnel on-site for directing traffic. See Exhibit 1 for manhole locations.
o S. Bozeman Ave (M.F04.0061)
o S. Black Ave (M.F04.00059)
o S. Tracy Ave. (M.F04.0058 & M.F04.00057)
· Utility Coordination: During this task, DOWL will assist the City in contacting and coordinating with the
utility company responsible for boring through the stormwater main directly downstream of the N. Black
Ave. manhole (M.F04.0059). It is assumed that this utility will be relocated at the expense of the utility
company prior to construction of improvements to the stormwater main.
Task 3. Hydrologic and Hydraulic Analysis
DOWL will update the stormwater model of the downtown stormwater collection system used in our design of
the N. Rouse Ave. storm drain system for MDT. Refinements to the model will be made based on surveyed
elevations and pipe sizes as well as any other pertinent information collected in Task 2. The design storm
precipitation events developed in Task 1 will be used in determining design flows for stormwater runoff. This
model will be used to assess the hydraulic performance of the alleyway stormwater main under current conditions
as well as with the various rehabilitation alternatives. For the purpose of budgeting, it is assumed that DOWL will
evaluate the hydraulic performance impacts of two (2) rehabilitation lining thicknesses. In addition, it is assumed
that three (3) alternatives to reduce stormwater contributions to the alleyway stormwater main will also be
evaluated. One of these alternatives will employ underground storage/infiltration galleries within the contributing
drainage basin to reduce runoff. Another alternative would include construction of a secondary west-to-east trunk
line to bypass excess flow to the outfall of the alleyway storm drain (the new N. Rouse Ave. storm drain). A third
alternative is assumed and will be developed pending the results of the other evaluations. A review meeting with
the City will be held to present the results of the hydrologic and hydraulic analysis and to set direction for the
alternatives to be evaluated.
Task 4. Alternatives Evaluation
DOWL will complete an evaluation of alternatives for replacement or in-situ rehabilitation of the alleyway
stormwater main. The alternatives analysis will consist of a review of in-situ lining options available to the local
market including the strengths and weaknesses of each as they apply to this project, the hydraulic restrictions,
potential construction considerations, and per lineal foot cost. An approximate cost of full replacement will also
be provided as a basis of comparison. From this evaluation, a minimum of two alternatives for in-situ rehabilitation
will be selected for development of construction bid alternatives.
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Task Order #03, Exhibit A – Scope of Services
Downtown Stormwater Mains Rehabilitation Evaluation
Page 4
A review meeting with the City will be held to present the rehabilitation alternatives and to select the alternatives
to be advanced to final design and construction documents.
Task 5. Report
DOWL will develop a report summarizing the methodology and findings of Tasks 1 through 4, including
recommendation of the preferred alternative. Stand-alone application instructions for the design storm
precipitation events generated through Task 1 will also be provided. The purpose of the report is to provide the
City with the necessary information for future planning within the contributing basin and for documentation of
the basis of design for the rehabilitation of the N. Rouse Ave. to N. Tracy Ave. alleyway stormwater main. A draft
report will be provided to the City for review and a review meeting will be held to present the work and to select
the preferred alternative for final design and development of construction documents. A final report will be
provided addressing the review comments received.
Schedule and Compensation
The initial survey and condition evaluation of the existing alleyway storm drain will be completed in the
winter/spring of 2020 with the draft report of the evaluation to be completed by the summer of 2020 This
schedule is based on an assumed notice to proceed for Task Order #03 in early March 2020.
Table 1 outlines DOWL’s fee for the proposed Scope of Services.
Table 1 – Task Order #03 Compensation
Task Description Fee
Task 01 – Precipitation Analysis $ 11,400.00
Task 02 – Existing System Evaluation $ 12,200.00
Task 03 – Hydrologic and Hydraulic Analysis $ 25,600.00
Task 04 – Alternative Analysist $ 10,000.00
Task 05 –Report $ 16,200.00
Total $ 75,400.00
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MAIN ST. MAIN ST.
N. BLACK AVE.
N. BOZEMAN AVE.
N. ROUSE AVE.
N. TRACY AVE.
MDT N. ROUSE AVE
RECONSTRUCTION PROJECT
AND 42" RCP STORMWATER
MAIN REPLACEMENT
EXISTING 36" CLAY TILE
STORMWATER MAIN.
(564 L.F.)
EXISTING 36" CLAY TILE
STORMWATER MAIN.
(358 L.F.)
EXISTING 30" CLAY TILE
STORMWATER MAIN.
(348 L.F.)
MENDENHALL ST.
LAMME ST.
EXISTING 27" CLAY
STORMWATER MAIN.
(49 L.F.)
DOWNTOWN STORMWATER MAINS
REHABILITATION EVALUATION PROJECT
406-586-8834
2090 Stadium Drive
Bozeman, Montana 59715
WWW.DOWL.COM
STORMWATER SYSTEM MAP EXHIBIT 1
LEGEND
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