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HomeMy WebLinkAbout20- Task Order 3 - DOWL, LLC - Dontown Stormwater DesignEXHIBIT 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 Getaber `l , 20 �Ia between the City and the Contractor. 1.0 PROJECT REPRESENTATIVES: ■ City: Kyle Mehrens, Stormwater Program Coordinator ■ Contractor: Wade Trion, 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) By: Dennis Taylor Title: Interi City Manager / —\IL ' Signature 1 APPROVED AS TO FORM: By: Greg Sullivan Title: City Attorney Signature: Stormwater Design Professional Services Agreement Page 1 1 DOWL, LLC (CONTRACTOR) By: Wade Irion Title: Water Practice Lead Signature: 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: Page 1 DOWL Task Order #03, Exhibit A — Scope of Services Downtown Stormwater Mains Rehabilitation Evaluation F1 O1M1TAYI ■ • 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 Page 2 Task Order #03, Exhibit A — Scope of Services Downtown Stormwater Mains Rehabilitation Evaluation DOWL 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. Page 3 Task Order #03, Exhibit A — Scope of Services Downtown Stormwater Mains Rehabilitation Evaluation D O W L 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 Page 4 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 Page 4 —W—W WW'" WW W L L W W W—W 3 5 5 5 5 5 5� s 5 5 5 5 5 5 5 s—s 5 5 5 LAMME ST. � -w 5w 5w 5 5 5 5w W --WW 5 5- -- s s 5 O—s 11 D ---- w w s s s s rr 3 �®' gr7 `LIT 3 �' ` I I � wr �. 3 1 J 3 ] \� ; 3 M 'I r i r 3 l i. ri r.:. 3 3 9 I =m ] 5 --�Y—S ,y—ig -WSW W w �� w W W W W W W� w W_�w�v $ S S S S S S� ,. S rsj _w_W 0 is s s m SDS ,, fu. -'fry �� a so ? . EXISTING 27" CLAY I M F04.00060 STORMWATER MAIN. (49 L.F.) P N� V I 3 3 ,EXISTING 36" CLAY TILE-� I, M.Fa4.001 0 + a1 N STORMWATER MAIN. p M.F'4.000 9 i II3 (358 L.F.) L I• i - - �': 3 o p '.D 0 Sp — SO p - 3 0 0 M.F 4.00058I4"I.FO .00340 a 0 M.F04. 1 0057 LU I UTILITY BORE THROUG TS.F,04.00004 STORMW 'TER MAIN. LU RS F04.000 3 p ° Q > I� b Q r ! EXISTING 30" CLAY TILE v U STORMWATER MAIN. ; Q Ir (348 L.F.) C0 Ovii awma 10 C 3 I I SDS x I WW W W W W ,� ... MAIN ST. III J-5 S I 5 5 5 5 5 5 5 n i a M.1704.00075 � I. F04.00001 p m m N� u LEGEND U msD PHASE 1 STORMWATER MAINS N ® MDT ROUSE AVE RECONSTRUCTION In — so— STORMWATER MAINS co 0 STORMWATER MANHOLES J 50 o so loo ME STORMWATER INLETS m SCALE IN FEET M.Y V,4.VVV01 .T Fnd Inn In r, W w s s s s ss s I.F04.I00002 �0 3 _I 1 1 d- MDT N. ROUSE AVE - RECONSTRUCTION PROJECT AND 42" RCP STORMWATER MAIN REPLACEMENT MENDENHALL ST. _ww w W ww I w— ' --- s s s s s s l s s 9 -�'so SD— SD d SO EXISTING 36" CLAY TILE) STORMWATER MAIN. (564 L.F.) -w w w _S_s_ A4.FD4.0063 SD �� SD 5D 3 M.F04.00062 TO BE REPLACED W TH MDT ROUSE �' Q R CONSTRUCTION, 7I"0 TYPE 3 MH. w 3 io I MAIN ST. 5' w w w N wW 5 5 S S 5 5 5 S - s. s S -si 3 N D