WARSAW WAL-MART EXPANSION FLOODPLAIN EVALUATION STUDY

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2 WARSAW WAL-MART EXPANSION FLOODPLAIN EVALUATION STUDY BERGMANN ASSOCIATES NOVEMBER 20, 2008 (revised June 8, 2009) TOWN OF WARSAW, WYOMING COUNTY, NEW YORK

3 Memorandum To: Jack Buholtz, PE From: Kenneth Avery, PE, CFM, D. WRE Date: November 20, 2008 (revised June 8, 2009) Re: Floodplain Evaluation Warsaw Wal-Mart Introduction This memorandum summarizes the results of a floodplain evaluation for the Warsaw, NY Wal-Mart. An expansion of this existing 5.35 acre facility has been investigated, and floodplain study requirements have been issued by NYSDEC (letter dated April 5, 2007 from R. Anderson to D. DiMatteo). This floodplain evaluation was performed to determine if either the existing or proposed facility encroaches on the Oatka Creek 100-year floodplain, and if so, does the encroachment exceed the maximum allowable 1.0 feet increase allowed under the National Flood Insurance Program (NFIP). Oatka Creek flows along the northwest side of the Warsaw Wal-Mart site. The location of the 100-yr floodplain at this site is shown in the effective Flood Insurance Study (FIS) for the Town of Warsaw, New York as an unnumbered Zone A. Unnumbered Zone A areas show the approximate 100-year flood limits but have not been studied using detailed hydrologic and hydraulic methods. The Federal Emergency Management Agency (FEMA) and the Town of Warsaw Zoning Code require that proposed development in unnumbered Zone A areas consisting of more than 50 lots or 5 acres include base flood (100-year) elevation data. Thus, a detailed study of the existing and proposed development is required to determine if the proposed construction activity would encroach on the floodplain. The Buffalo District USACE is conducting detailed HEC-HMS and HEC-RAS model studies of the Oatka Creek in the Town and Village of Warsaw. Preliminary versions of both of these models were provided to Bergmann Associates by the Corps. Although the models do not represent the effective FIS, once completed, the results of the HEC-HMS and HEC-RAS model studies will provide a new Zone AE (detailed study) in the project area. Preliminary floodplain mapping, created by the Buffalo District USACE, have been attached. To begin, we compared the existing drainage areas and hydrology. The Village of Warsaw, NY, located approximately 1.9 miles upstream of the Wal-Mart site, includes an effective, detailed FIS of Oatka Creek. The drainage areas calculated in the USACE HEC-HMS model for the Oatka Creek were checked against corresponding values that were reported in the detailed study to verify reliability. This check is summarized in Table 1. The minor difference in the basin delineation and site location could cause the variation that is seen between the reported and calculated drainage area values. The variation between the FIS and the HMS is less than 2% at comparable locations. The values from the HMS model were used in the analysis process because they were considered to be the most current. Table 1: Drainage Area Comparison (Sq. Mi.) Village of Warsaw, Location Effective FIS Study HMS Model USGS Gage Old Buffalo Road Bridge (1) Wal-Mart Site N/A (1) The Old Buffalo Road Bridge is located at the downstream limit of the Village of Warsaw, which is also the downstream limit of the effective FIS study. Phone: Fax: First Federal Plaza / 28 East Main Street / Rochester, New York Architects / Engineers / Planners

4 Memorandum Hydrology Bergmann Associates performed independent peak discharge calculations using statistical analyses of the USGS gage records and USGS regression equations as a check of the HMS and FIS peak flow calculations. The procedure for statistically analyzing the USGS gage records near the Wal-Mart site is published in Bulletin #17B, Guidelines For Determining Flood Flow Frequency. The procedure for adjusting the statistical analyses for the ungaged sites and for performing the USGS regression equations is published in Magnitude and Frequency of Floods in New York: Scientific Investigation Report The comparison of the FIS data with the results of the HEC-HMS model, log-pearson Type III analysis, and the Region 6 Regression Equation is summarized in Table 2: Village of Warsaw Effective FIS Table 2: 100-Yr Flow Rate Comparison (cfs) HMS Model Phone: Fax: First Federal Plaza / 28 East Main Street / Rochester, New York Architects / Engineers / Planners Region 6 Regression Equation Weighted average of Regression and Log-Pearson III Location Log-Pearson III Gaging Station (3) 4990 (5) 4490 (3)(6) Old Buffalo Road Bridge (1)(3)(4) 5430 (5) 4990 (3)(6) Wal-Mart Site 3770 (1)(2) (1)(3)(4) 6230 (5) 5990 (3)(6) 1) Value projected from another location via the drainage area adjustment equation, shown below: Q (100@(2)) Q (100@(1)) A (@(1)) A (@(2)) X Q (100@(2)) = Q (100@(1)) * (A (@(2)) / A (@(1)) ) X, where is the flow rate at a downstream location, is the flow rate at a upstream location, is the drainage area of the upstream location, is the drainage area of the downstream location, and is a constant of the drainage basin, in this case 0.9 (determined from USACE Genesee River Basin study) 2) The drainage areas, used in this projection, are from the HMS model at the Old Buffalo Road Bridge and the Wal-Mart Site. 3) Value based on a Log-Pearson Type III Distribution of annual peak flow data from Gaging Station between 1964 and ) The drainage areas, used in this projection, are from the HMS model at the Gaging Station and the projected site. 5) The drainage areas, used in this calculation, are from the HMS model at the corresponding site. 6) The drainage areas, used in this calculation, are from the HMS model at the Gaging Station and the corresponding site. The values under Village of Warsaw Effective FIS at the Gaging Station and the Old Buffalo Road Bridge were obtained from the Village of Warsaw, NY FIS study. The third value under Effective FIS, for the Wal-Mart site, was obtained through the use of the drainage area adjustment equation. The drainage areas from the HEC-HMS model at the Old Buffalo Road Bridge and Wal-Mart site were used in this calculation. The three values under HMS Model were obtained by reviewing the output from the HEC-HMS model. The HEC-HMS model, developed by the Buffalo Distric USACE, is the most current source of data. The first value under Log-Pearson III is the value that was obtained by performing a Log-Pearson Type III Distribution of the annual peak flow rate data for Gaging Station Gaging Station is located in the Village of Warsaw and contains annual peak flow rates from 1964 to The Log-Pearson III Distribution was performed in accordance with the procedure published in Bulletin #17B of Guidelines For Determining Flood Flow Frequency. The second and third values under Log-Pearson III are values that have been projected from the Log-Pearson III value at the Gaging Station with the drainage area adjustment equation and drainage areas from the HEC-HMS

5 Memorandum model. The values under Region 6 Regression Equation calculated with the Region 6 regression equation, basin characteristics at the Gaging Station, and drainage areas for the respective sites. The Region 6 regression equation and basin characteristics at the Gaging Station were obtained from Magnitude and Frequency of Floods in New York. The basin characteristics were assumed to be constant between the Gage Station and the Wal-Mart site. The respective drainage areas were obtained from the HMS model. The values under the Weighted Average of Regression and Log-Pearson III were calculated according to the procedure published in Magnitude and Frequency of Floods in New York. Respective drainage areas from the HMS model and the results of the Log-Pearson Type III Distribution of Gaging Station data were used to perform these calculations After comparing the results of HEC-HMS model with the USGS Regression Equations and Log-Pearson III gage analysis, we concur that the HMS model provides is a reasonable representation of the hydrology. As a result, we used 5780 cfs as the 100-year discharge rate of Oatka Creek at the Wal-Mart site. Hydraulics Modifications were made to the HEC-RAS stream cross sections to match the topography that was obtained from a detailed survey of the Wal-Mart site performed by Bergmann Associates. The modified stream cross sections and the elevation of the floodplain can be seen in Figures 1 through 4. The elevation of the floodplain at the site can be seen in the Table 3. Figure 5 illustrates how the Oatka Creek Floodplain relates to the proposed Wal-Mart site. Both the FIS and survey of the Wal-Mart site are on NGVD 1929 datum. The new HEC-RAS work performed by the USACE is on the North American Vertical Datum 1988 (NAVD 88). The HEC-RAS output has been converted to the NGVD 1929 in Table 3 for comparative purposes. Table 3: Floodplain Elevation at the Wal-Mart Site Location River Station Flow Rate Floodplain Elevation From HEC-RAS Lowest Grading Elevation (cfs) (NGVD 1929) (1) (NGVD 1929) South Side of the Site South Side of the Wal-Mart Building North Side of the Wal-Mart Building North Side of the Site ) The NGVD 1929 datum is approximately 0.48 ft above the NAVD 88 datum at this location The floor elevation of the existing and proposed Wal-Mart is approximately 993. The extent of the grading around the proposed stormwater management basin, parking area and truck turn-around areas is currently slated to end at an elevation of 975, at the lowest extreme. The Oatka Creek floodplain will not be affect by the fill at this site because all the proposed grading will occur above the 100-year flood elevation. Phone: Fax: First Federal Plaza / 28 East Main Street / Rochester, New York Architects / Engineers / Planners

6 Memorandum 100-yr Water Surface Elevation (El ) Proposed Limits of Grading Figure 1: Proposed Cross Section at the South Side of the Site Proposed Wal-Mart Building Proposed Limits of Grading 100-yr Water Surface Elevation (El ) Figure 2: Proposed Cross Section at the South Side of the Wal-Mart Building Phone: Fax: First Federal Plaza / 28 East Main Street / Rochester, New York Architects / Engineers / Planners

7 Memorandum Proposed Parking Lot Proposed Limits of Grading 100-yr Water Surface Elevation (El ) Figure 3: Proposed Cross Section at the North Side of the Wal-Mart Building Proposed Limits of Grading 100-yr Water Surface Elevation (El ) Figure 4: Proposed Cross Section at the North Side of the Site Phone: Fax: First Federal Plaza / 28 East Main Street / Rochester, New York Architects / Engineers / Planners

8 Memorandum Figure 5: Proposed Wal-Mart Site with Floodplain and Limits of Fill Phone: Fax: First Federal Plaza / 28 East Main Street / Rochester, New York Architects / Engineers / Planners

9 NYSDEC FLOODPLAIN CORRESPONENCE AND MEETING MINUTES MARCH 13, 2007 MEETING WITH NYSDEC, WAL-MART, AND TOWN REPRESENTATIVES MARCH 28, 2007 LETTER FROM TOWN ATTORNEY TO NYSDEC APRIL 5, 2007 LETTER FROM NYSDEC TO TOWN ATTORNEY

10 Memorandum Project: Warsaw NY, Wal-Mart Supercenter Store # Store Type: Expansion Subject: Meeting with DEC Region 9 and Town of Warsaw Representatives Location: Region 9 DEC Offices, Buffalo NY Date: Tuesday, March 13 th, 2007 Attendees: Steven J. Doleski, DEC Permits Penny Dempsey, DEC Permits Drew Reilly, Wendel Duchscherer Karl Grohs, Warsaw Planning Board Greg McKurth, Wyoming Co. SWCD G.R. Pfiefer, Warsaw ZBA Kevin B. Zeches, Councilman, Warsaw Karl Grohs, Warsaw Planning Board Edward Premo, HSE Janice Linn, HSE Gerard Palumbo, DEC Donald Coogan, Jr., TES Gina Marie Mangino, Bergmann Scott Hagadorn, Bergmann David M. DiMatteo, Warsaw Bill Smythe, DEC Maureen Brady, DEC Legal Jack Buholtz, Bergmann Becky Anderson, DEC Jerome Smith, Warsaw (via telephone) Chuck Rosenburg, DEC Doug Borschel, Permits Summary: A meeting was held in DEC s Region 9 offices on March 13 th, 2007, to discuss DEC s concerns regarding the Wal-Mart Warsaw Supercenter project and the status of SEQR lead agency. The discussions revolved around questions raised by Mr. Steven Doleski, Region 9 Regional Permit Administrator, in a letter he sent to the Warsaw Town Attorney on February 8th, Additionally, discussions also included a resolution of DEC s objection to the Town of Warsaw Planning Board becoming SEQR lead agency. Minutes: 1. Stephen Doleski opened the meeting by asking the applicant to provide an overview of the project. Jack Buholtz gave a brief presentation of the site plan to the meeting attendees. 2. Gina Mangino explained the method of floodplain analysis for Oatka Creek that Bergmann would be using on the project. Becky Anderson advised that an analysis of the floodplain should include a HEC-RAS model of (1) predevelopment and (2) post-development conditions to show the current extents of the floodway and floodplain at the project site. 3. Becky Anderson advised that in 2005 the DEC contracted with the ACOE to develop revised floodplain maps for the Town of Warsaw, but that budget constraints may delay this analysis for another two years. Becky advised that

11 the floodplain analysis should employ the data results from the FIRM study completed for the Village of Warsaw. A revision to the Town of Warsaw floodplain maps would require a LOMR to FEMA. 4. Becky Anderson advised that the applicant may need to investigate mitigation measures should the 100-year flood elevation be raised from existing levels as a result of the development. Mitigation measures such as flowage easements were discussed. 5. Becky Anderson advised that the Warsaw Zoning Law does not supercede the Local Law of 1987 regarding floodplain ordinances. The Zoning Law does not address all of the topics covered by the Local Law and therefore those portions of the Local Law of 1987 remain in effect. 6. Steven Doleski advised that the DEC has concerns over the placement of a water quality pond within the floodplain. DEC representatives indicated that an analysis of impact of flooding events on the displacement of nutrients from the pond and potential scouring effects would need to be analyzed by the applicant. 7. Steven Doleski advised that he spoke with Diane Koslowski at the ACOE and she has not confirmed that there aren t any Federal Wetlands on the project site. Don Coogan advised that a request for an ACOE jurisdictional determination has been submitted to the ACOE. Steven Doleski added that if an individual wetland permit from the ACOE was required, the DEC would need to issue a Water Quality Certification. Steven Doleski stated that the Water Quality Certification is a discretionary permit, which the Wal-Mart project team does not agree with. 8. Steven Doleski advised a review of NYS DEC wetlands on the project site is required. Don Coogan advised that the review of the State DEC Freshwater Wetland maps did NOT indicate the presence of State DEC wetlands on the site; adding that the closest one was approximately 4000 feet away. Don Coogan advised that the formal Map Amendment process would be required if the DEC was going to designate new wetlands on the site. The DEC will be coordinating with Connie Evans from the Bureau of Wildlife to follow up with a Map Amendement, if required. Maureen Brady advised that under Article 24 of the Map Amendment process, the DEC may notify a property owner that jurisdictional wetlands may be on their property. Notice to the property owner that the DEC is in the process of determining whether state jurisdictional wetlands may be present gives DEC jurisdiction over the property. The proposed expansion would not be able to proceed if DEC sends Wal-Mart such a notice. 9. Steven Doleski referenced a letter sent from the DEC to the Town of Warsaw regarding the status of the sewage collection system in the existing

12 Wal-Mart plaza which indicated that the Town needs to form a sewer district to allow for this use of the existing system. DEC representatives indicated that their biggest concern is the ownership of the sewer pumpstation. Wal- Mart representatives stated that the Wal-Mart has an existing agreement with the Village of Warsaw through 2011 to pump sewage via force main to the Village s sewer treatment plan. David DiMatteo advised that a consultant will soon be working on the formation of a sewer district to address the DEC s concerns. 10. Maureen Brady advised that records indicate the Village of Warsaw was provided with an EPA grant condition for sewer improvements, and that there may be restrictions on sewage system alterations within the Town. Dave DiMatteo explained that the majority of the referenced funding was applied towards improvements in an Industrial Park and that any conditions to the referenced grant would not impact the Wal-Mart project. 11. A discussion was held regarding the status of SEQR lead agency. Steven Doleski advised that the DEC will assent to the Town of Warsaw Planning Board becoming SEQR lead agency under the conditions that the Town POS- DEC the project, and that the DEC have the ability to review all pre-draft SEQR related documents for the project. David DiMatteo added that he had previously recommended to the Town of Warsaw Planning Board that this project receive a Positive Declaration.

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16 FEMA FLOOD INSURANCE MAP TOWN OF WARSAW WYOMING COUNTY, NEW YORK PANELS NO B-0001 AND 0002)

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19 USACE BUFFALO DISTRICT PRELIMINARY FLOODPLAIN MAPPING TOWN AND VILLAGE OF WARSAW WYOMING COUNTY, NEW YORK

20 PROJECT LOCATION

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