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HomeMy WebLinkAboutItem 06.eDate: 21 February 2012 Item No. APPROVE PROPOSAL FROM BARR ENGINEERING CO. TO PREPARE THE APPLICATION FOR A LETTER OF MAP REVISION (LOMR) OF THE MARION BRANCH SOUTH CREEK DRAINAGEWAY Proposed Action Staff recommends adoption of the following motion: Move to approve the proposal from Barr Engineering Co. to prepare the application for a Letter of Map Revision (LOMR) of the Marion Branch South Creek drainageway. Overview During review of the recent preliminary Flood Insurance Study (FIS) report and Flood Insurance Rate Map (FIRM) for Dakota County, City staff identified that the FIRM does not accurately reflect existing conditions, specifically public storm sewer improvements, immediately downstream of the Lake Marion outlet. To revise the FIRM such that it identifies the most accurate floodplain information available, the Federal Emergency Management Agency (FEMA) requires that the City complete a Letter of Map Revision (LOMB). Attached is a proposal from Barr Engineering Co. providing the scope of work, estimated costs and schedule for completing the LOMR application. Project funding would be from the Utility Fund (Environmental Resources). The estimated project cost is $23,400 and includes FEMA's LOMR application fee. Primary Issues to Consider • Why is it important to comply with FEMA's floodplain management requirements? This allows the City to remain enrolled in the National Flood Insurance Program (NFIP), which provides residents the opportunity to purchase or renew flood insurance policies, Supporting Information • Barr Engineering Co. Proposal, dated February 6, 2012 Zach'a'ry Joh spn Inter Engi Financial Impact: $23,400 Related Documents (CIP, ERP, etc.): Notes: Budgeted: No Source: Utility Fund (Environmental Resources) February 6, 2012 Mr. McKenzie Cafferty Environmental Resources Manager City of Lakeville 20195 Holyoke Ave Lakeville, MN 55044 resourceful. naturally• engineer and environmental cansjltoros ' • QiiiftiMPANERW Re: Proposal for Professional Services — Lake Marion Outlet LOMR Application Using the Effective HEC -RAS Model Dear Mr. Cafferty: This letter presents a revised proposal for providing assistance in applying for floodplain modifications along the Lake Marion Branch of South Creek betwen Lake Marion and Dodd Boul.vard based on the current effective HEC -RAS model. We have revised our original proposal, dated February 3, 2010 based on conversations with city staff, and to included additional assumptions related to the LOMR submittal. This letter presents our understanding of the project, a list of our assumptions made in preparing this revised proposal, and our proposed work scope, schedule, and cost for completing the work. Project Understanding and Objectives The effective Flood Insurance Rate Map (FIRM) does not reflect existing conditions immediately downstream of the Lake Marion outlet. As a result there are four residential homes that are currently mapped within the floodplain, and have received notifications requiring purchase of flood insurance. It is our understanding that the Minnesota DNR (MnDNR) has informed the City that a LOMR will be required to revise the floodplain in this area. While construction of the outlet modifications has already occurred, there are several outstanding tasks that must be addressed to gain MnDNR and FEMA approval. The following sections include work tasks and cost estimates associated with completing a LOMR between the Lake Marion Outlet and Dodd Boulevard. The storm sewer modifications to the Lake Marion outlet has modified water surface elevations along the Lake Marion Branch Tributary to South Creek. Because a FEMA floodplain along this tributary is shown on FEMA's effective maps, the MnDNR and FEMA will require submittal of a Letter of Map Revision (LOMR) for their approval. FEMA guidelines state that a LOMR should be completed if • The modification results in more than a I,0' increase in the BFE (Base Flood Elevation), and there is no regulatory floodway established. i3aff Engine.erino Co_ 4700 Wes; 77th Stree, Suite 200, Minneapolis, MN 55435 952.022.2600 www.barr.cam Mr. Caf`erly February 6, 2012 Page 2 • The mdoification takes place within the regulatory floodway that would result in any increase in the BFE. In order to be in conformance with FEMA.'s requirements, and receive FEMA's approval for construction, it will be necessary to complete a LOM.R. that will require detailed technical review. To apply for the LOMR the following steps will need to be completed: 1. Additional hydraulics calculations will need to be completed for the Lake Marion Branch Tributary to South Creek. According to FEMA rules, the following models must be created and submitted to FEMA: • Duplicate Effective Model: A copy of the hydraulic analysis used to create the effective floodplain and BFEs (duplicating the existing information). This model would need to be recreated using current software. • Corrected Effective Model: A model that incorporates additional information into the duplicate effective model to represent existing conditions (i.e. new topographic information). • Existing or Pre-project Conditions Model: A model that incorporates any changes that took place within the floodplain since the date of the effective model. • Revised or Post-Project Conditions Model: A model that incorporates the modified Lake Marion outlet. 2. Updated floodplain maps will need to be created based on the results of the new hydraulic models for the 0.2- and 1- percent events as well as the regulatory floodway. The updated floodplain boundary must "tie -in" to a boundary on the effective maps (a location where the old flood levels snatch the new levels within 0,5 feet). In order to find a suitable "tie -in" location, it would be necessary to remap the floodplain to Dodd Bouivard. 3. It may be necessary to collect additional survey information. 4. New FEMA applications forms will need to be completed for this submittal. In addition to the information needed for the LOMR submittal, this submittal would require details about the hydrologic and hydraulic modeling, details on the mapping, details on the current BFEs and descriptions of why BFEs have changed from the effective maps, and details on any structures located within the area being remapped. Assumptions Following discussion with City staff, the scope of work and corresponding costs presented in the February 3, 2012 proposal have been revised to reflect the additional assumptions listed below: • During preparation of the LOMR application submittal Barr staff will attend 1 meeting with city staff at the Barr Engineering Minneapolis office. • The MnDNR will provide the current effective model of the .Lake Marion outlet W: ',Business Units \WR1Pa'aposals12012T022.12 City of Laltevilde Highvicw and Marion Lot• Rl is1Marionlpieces \D2062012Lakeville Marion_Proposal.docx Mr. Cafferty February 6, 2012 Page 3 • The current effective model will have been developed in HEC -RAS, be georefernced, have been developed to FEMA standards, and include supporting documentation. • The hydrology will not be revised from what was used in the current effective model • No duplicate effective or corrected effective models will be required as part of the LOMR application submittal • The installed pipe has been sized appropriately to completely contain the 0.2- percent event, so that the water surface elevation will remain below existing ground and no inundation mapping will be required in the area where the pipe has been installed. • Only 8 hours of support will be provided for addressing FEMA questions following the LOMR application submittal. The assumptions listed above have been added following the February 3, 2012 proposal. The work scope continues to include the assumptions for each specific task that were listed in the February 3, 2012 proposal. Any deviation from the assumptions listed above or those listed in each individual work task will result in a request for scope and corresponding schedule and budget adjustments. In addition, there maybe other unlisted issues that arise that require additional funds to address. In that case we will notify city staff these additional items and complete the work on a time and expense basis. Work Scope The following work scope has been developed assuming that the current effective HEC -RAS model will be used for preparation of the LOMR submittal. Since the current FIS was done with HEC -RAS, this approach to completeing the LOMR would be less expensive than submitting the new XP -SWMM model. It will also be easier to a) deal with FEMA, b) transition between the four required models that have to be submitted, and c) complete the floodway analsyis. Using the HEC -RAS model will also simplify FEMA's review process since HEC -RAS is the most commonly used model for floodplain mapping. The disadvantage of using HEC -RAS is that there would still be two sepreate models with differing flood elevation that the City would need to maintain for regulatory purposes (one for FEMA and one for develops, assuming the City continues with the XP -SWMM modeling updates). Below is a detailed description of each work task and corresponding assumptions. Any deviations from the assumptions will result in a request for scope and corresponding schedule and budget adjustments. In addition there maybe additional issues that arize that will require additional fundes to complete the LOMR application submittal. Should these issues arise we will notify City staff and address these additional items on a time and expense basis. Table 1 includes a summary of the work tasks and associated costs. Task 1— Update HEC -RAS Hydrologic Model to FEMA Specifications for Hydraulic Models (58,600) As part of the LOMR submittal FEMA requires evaluation of the 0.2, 1, 2, and 10- percent flood events and floodway analysis. The HEC -RAS model will be revised as needed for this evaluation. Work items in this task include preparation of models required for a LOMR submittal. Effective Model - For this work task it is assumed that a copy of the current effective model can be provided by the MnDNR. We have assumed that the current effective model will have been developed in HEC -RAS, include supporting docuemtation, is georeferenced, and have been W:1Business Units \WR. \Proposals120121P022.12 City of Lakeville Highview and Marion LOMB \Mari o;'pieces102062©121Iakeville Marion_Prohosal,doox Mr. Cafferty February 6, 2012 Page 4 developed to FEMA standards such that no additional modifications will be required to the current effective model. Duplicate Effective and Corrected Effective Models — Because the effective model will be used we have assumed that for this work task FEMA will not require a duplicate effective or corrected effective model for the LOMR submittal, Revised Conditions Model — For this work task it is assumed that the outlet pipe from Lake Marion has been sized appropriately, such that when the revised outlet pipe is added to the model the 0.2- percent water surface elevation is below existing ground and contained within the pipe. Therefore no inundation mapping will be required in the location of the modified -Lake Marion Outlet. Additional work items to be completed as part of Task 1 include: • Develop models required for FEMA submittal • Complete 1- percent floodway analysis Task 2 — Inter Agency Hydrologic Review Committee ( IAHRC) Submittal (SO) If the effective HEC -RAS model is used for the analysis, we have assumed that the existing hydrology will be used for the analysis as well and a IAHRC review will not be required. We have assumed that this LOMR includes the extension of the outlet pipe from the Lake Marion outlet structure, and that the outlet structure itself has not changed from when the current effective model was developed. Therefore, the existing hydrology is still applicable for this LOMR submittal, Task 3 — Prepare maps to FEMA Specifications for Application (52,000) Based on model results obtained during Task 1 floodplain delineations and annotated FIRMs will be prepared for the LOMR submittal. Work items within this task include: • Prepare floodplain maps for 1 FIRM panels • Prepare topographic working map for 1 FIRM panels • Annotated FIRM for 1 panels Task 4 — Prepare FEMA LOMR Submittal (53,300) Based on model results obtained. during Task 1 the FEMA MT -2 forms will be completed, and supporting information developed for the LOMR submittal. Work items within this task include_ • Complete MT -2 application forms • Prepare project narrative • Package hydrologic and hydraulic model files for FEMA review • Preparation of floodway data tables and flood profiles FEMA requires that nearby property owners are notified of changes to the floodplain on their property. We assume that will not be necessary because the 100 -year floodplain should remain within the existing pipe. Should property owner notifications be required, Barr could assist with this on a time and expense basis as directed by the City. W:113usine5s lh2its1WR\Pmposals120I21P022.12 City of'Lakeville Highview and Mariolz LOMRsNarioa 1pieees1020 62 0 1 21Lakeville _Marion Proposal.doex Mr. Coifed} February 6, 2032 Page 5 Task 5 — Meeting with City and Obtain City Concurrence ($2,400) The LOMR application form requires a signature of a local official to acknowledge they are aware of the application and that the LOMR request is consistent with their local floodplain ordinance. In this case the local official will be a City staff member. It is assumed that City concurrence will not need to go before the City Planning Commission or City council. This work task includes one meeting with City staff at Barr's office to go over the requirements and LOMR application. This work also includes providing regular updates on the project status and coordination with the City and others. Task 6 — Submit application to FEMA ($6,200) We will prepare copies of the FEMA application and supporting materials and submit the application to FEMA. Copies of the materials will also be provided to the City. The cost estimate for this task includes to $5,300 LOMR application fee to FEMA. Task 7 — FEMA follow -up ($900) FEMA will have questions regarding the information submitted for review. We have included 8 hours of time to coordinate with FEMA and respond. to FEMA's questions. Additional correspondence and coordination with FEMA during the review process will be completed on a time and expense basis. Total cost for the Alternative A LOMR submittal: $23,400 Schedule We anticipate that the LOMR application submittal can be prepared within 6 months following authorization to proceed. Work preparing the LOMR application submittal will begin after the MnDNR is able to provide the current effective model. After the LOMR application has been submitted it will depend on how long FEMA takes reviewing the submittal package, before the FIRMs are revised. We look forward to working with you on these projects. If this proposal is acceptable we will work with you to determine the appropriate agreement for performing this work. Please contact Scott Sobiech at 952 -832 -2755 or Brandon Barnes at 952 - 832 -2737 if you need additional information or have questions. Sincerely, Scott Sobiech, PE, CFM Vice President Len Kremer, PE Vice President W:13usiness Units \WR \Propnsills\20I21P022.12 City of Lakev;ne Highview and Marion LOMRsAtarionlpieccs1p2062012!La eviHe tvfarion_ Proposai.doex Work Task ' Estimated Cost • HEC =RAS Task 1- Update XP -SWMM Hydrologic Model to FEMA Specifications for Hydraulic Models $8 1. Adding additional cross sections along trihuatry as required by FEMA specifications 2. Run 500 event & revise cross sections as needed 3. Complete floodway analysis Task 2 - Inter Agency Hydrologic Review Committee Submittal $0 1. Summarize hydrologic information along North Creek for IANRC review 2. Prepare fetter to IANRC and submit model results Task 3 - Prepare maps to FEMA Specifications for Application (Tope Work Map and $2,000 Annotated FIRM) 2. Prepare floodpiain maps for 1 pones 2. Topographic working mop for 1 panel 3. Annotated FIRM for 1 panels 4. floodpiain delineation of the 100- yearfloodploin and delineation of the 100 -year floodway and 500- year floodpiain Task 4 - Prepare FEMA's MT - 2 LOMR Forms (which include tasks listed below) $3,300 1. Complete application forms 2. Narrative on project and submittal. Knowing the project and purpose of the request better ensures the needs of the requester are met. 3, Hydrologic Computations along with digital files of computer models used. 4. Hydraulic Computations along with digital flies of computer models used. 5. Certified topographic map with floodpiain and floadway delineations. 6. Annotated DHS -FEMA FIRM and /or FBFM to reflect changes due to project (FJRMs and /or FMFMs can be ordered on-line at http://stam.rnsc.ferna.gov/). 7. Items required to satisfy any 01-15 -FEMA NF!P regulatory requirements. 8. Prepare flaodway data tables 9. Prepare flood profiles for the 10 -, 50 -, 100- and 500 -year flood events Task 5 - Meeting with City and Obtain City Concurrence $2,400 1. One meeting to review the submittal information and obtain concurrance before submitting materials to FEMA and lAHRCfor review. Task 6 - Submit application to FEMA $6,200 1. Submit hard copies of the application to FEMA and tAHRC. 2. Submit electronic copies of the application submittal to the City 3. Payment of $5,300 FEMA application fee Task 7 - FEMA Follow -up (coordinate with FEMA to address review questions and comments - see assumptions below) 1. Assumes one round of model and map revisions, if necessary, to address FEMA review comments. $900 Additional rounds of revisions, if necessary, following FEMA's initial comments will be completed an a time and expense basis. Total = $23,400 Work Scope Assumptions. - We are not anticipating increases in BFEs and/or floodplainlfioodway boundaries, but if these do occur, property owner notifications to the adversely affected property owners are required by FEMA (these notifications are not included in this icost estimate, but Barr could help with this on a time and expense basis, if notifications are necessary) - City staff will collect necessary survey data required for FEMA submittals, Table 1. Lake Marion Outlet Work Tasks and Costs LOMR Submittal for Lake Marion Outlet City of Lakeville February, 2012