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Home My WebLink About2001-10-09 BRAA Ltr to OPH Re Oak Park StationBonestroo NEW Rosene Anderlik & Associates En & Architects October 9, 2001 Bonestroo, Rosene, Anderlik and Associates, Inc. is native Action/E Opportunit Emplo and Emplo Owned Principals: Otto G. Bonestroo, P.E. - Marvin L. Sorvala, P.E. ■ Glenn R. Cook, PE. - Robert G. Schunicht, P.E. ■ Jerr A. Bourdon, RE. Senior Consultants: Robert W. Rosene, PE. ■ Joseph C. Anderlik, P.E. ■ Richard E. Turner, RE. ■ Susan M. Eberlin, C.P.A. Associate Principals: Keith A. Gordon, RE. ■ Robert R. Pfefferle, PE. ■ Richard W. Foster, RE. ■ David D. Loskota, PE. ■ Mark A. Hanson, RE. ■ Michael T. Rautmann, RE. ■ Ted K. Field, PE. ■ Kenneth P Anderson, RE. ■ Mark R. Roffs, RE. ■ David A. Bonestroo, M.B.A. ■ Sidne P Williamson, PE., L.S. ■ A M. Rin M.B.A. ■ Allan Rick Schmidt, PE. ■ Thomas W. Peterson, PE.. James R. Maland, RE. ■ Miles B. Jensen, RE. ■ L. Phillip Gravel 111, RE. ■ Daniel J. Ed PE. Ismael Martinez, P.E. ■ Thomas A. S RE. ■ Sheldon J. Johnson ■ Dale A. Grove, RE. ■ Thomas A. Roushar, RE. ■ Robert J. Dever P.E. Offices: St. Paul, St. Cloud, Rochester and Willmar, MN a Milwaukee,. Wl ■ Chicacio, IL Website: www.bonestroo.com Ms. Kris Danielson CnInmunit Development Director Cit ot'Oak- Park Hei '4168 Oak Park Blvd., i P. 0, Box 2007 Oak Park Hei -N 5508'62-2007 Hei Re: Oak Park Station Preliminar Plat & Concept Development Plan Rev'%.. Bones t roo File -No. 5 -01 -000 Dear 1--,ris: � EcEiv 1W Vie hav(C. reviewed the preliminar plat and concept development plans for the proposod Oiik Park Statlon development. in the Kem Center as E.Libmitted b METRO Lan' .J Stiryevinkj t� Encrincel-Inc'T 4t) and have the followinor comments/recommendations: C-) fe Site.. Lavout[AccesS Loca-tions: I I ch • he propcisen, n1a op. t creates a private street that lo s from Memorial Avei-we North to 58' Str.r,N%_1t North. Sam) .;t'ar sewer and water main afe proposed within the private Street ririmarilv -e Hicrhwa 51) Sanitar selver and water serv'c cs t i� Jere!: the four lots adjacent to State 4:) .1 %.� I S .[,%r the t hr " -- M c lots aqjacent to emorial, Avenue North are in place from previous Kern Ce.ater 'I m P r o v m n s. jio Citv ma want to consider re the propo _.d internal street to be a street (a 4m -dncy- to publii c uffl; ties '1 es within this street should be public" • sin...--. Lil- 110 * 11.1 1 nonnet_.L I., I C -e -trn---,t over oat)`c uJI'lities ma rc6uft in d1'S-DUteS Mentorial AverMe North. Havin a private b V L A. jl* 4- -,Y. or mainlenank,-c ana upkeep of LleS eV01-11 need re�)ai Un la t, antics in. the Wture should th e Utiti -* L 1_' e. - S 1. r e e t itself be q uestioned. Re the street to be public woluld ensul-e-,, fli-lat the str and associated utilities are constn.icted to t,,it standards, and the iSSLIC' of ow.1iiership and/cil.- I x v - Mintenance would be clear. As such, the street should be c.onst!.- Act1(_,0 to . standard C*t. t . 'Widths for rurb and g utter and ri -of-wav, and to the appropriate tonnaue clas.,sifil cation for .01 commercial./industrial areas. Sanl�lar, Sewer: as , orel'ninar sanitar sewer la in the proposed internal street is acceptable. T ire O rel' X submitted. it is assumcd that the three lots adjacent- to Memorial Avenue North will utilize 0h existin sanitar sewer services provided b previous Kern Center improv,,--.-Iments. If'riot5 Z:) thes.e, services will need to be properl abandoned. 2335 West Hi 36 m St. Paul, MN 55113 w 651-636-4600 ■ Fax: 651-636-1311 Water Main: 4. A 6" water main is proposed to loop through the site, connecting to two existing services off Memorial Avenue N. provided by previous Fern Center improvements. Sewer and water services were provided at four different locations along Memorial Avenue North to serve this site. With the new plat configuration, water services now need to reach the four lots proposed along S.H. 5. The developer /engineer should verify that a 6" main line will provide adequate fire protection volumes and pressures for the new lot layouts. A better looping scenario is for the proposed Water main in the internal street to connect to the main lines in Memorial Avenue N. and in 58 "' Street North. However, this will require cutting across both streets to make connections (via wet taps). 5. The 6" services provided along Memorial Avenue N. should be utilized for the three adjacent lots, otherwise properly abandoned if not to be used. 6. Proposed locations of valves and hydrants need to be reviewed with Publics Works and the Fire Department. Grading & Drainage /Storm Sewer: 7. Grading for the proposed site does not change ultimate drainage patterns tributary to the existing Kenn Center pond. The existing Kern Center pond has a 42" diameter outlet pipe currently restricted to a 12" opening. With this restriction, the pond is at maximum capacity for the development currently existing in the Kern Center. The proposed grading and drainage plan shows enlarging the existing Fern Center pond (in Outlot A). However, from discussions with METRO, the additional pond storage accounts only for the difference between a 65% impervious site and an 80% impervious site, not for the increase in runoff from. existing conditions to post - development conditions. METRO needs to calculate how much additional ponding is required due to their development with the 12" outlet restriction, in place, and provide for this additional storage (increase the Kern Center pond accordingly). 8. We have analyzed the entire Kern Center as is relates to the existing pond storage and water levels under ultimate developed conditions: With the pond outlet unrestricted (opened up to its 42" diameter pipe size), the pond surface area needs to be increased by 1.0 acres to accommodate ultimate development within the entire Fern Center (see attached Conversation Record between Erik Peters of our office and Doug Litterer of METRO Land Surveying and Engineering). We are currently calculating hove much the existing pond surface area needs to be increased to accommodate ultimate development within the entire Kern Center with the 12" outlet restriction remaining in place. Assuming the 12" outlet restriction Will remain in place indefinitely (i.e. regional improvements to the wetland west of the Kern Center by Brown's Creek Watershed District not occurring any time soon), oak Park Station will need to enlarge the pond to handle their proposed development, as mentioned in 7. above, at a minimum. Once we have the entire Kern Center modeled under ultimate development conditions with the 12" outlet restriction in place, we can determine how much larger the existing pond will need to be, and/or how much ponding is required for those portions of the Kenn Center currently undeveloped. If physically possible, enlarging the existing pond is more desirable, both economically and hydraulically, than each development providing its own on -site ponding. 9. Two catch basins are proposed on the internal street to handle all internal storm water runoff. Draina calculations and a draina area map should be submitted to verif the proposed storm sewer can handle storm water flows, and/or whether more storm sewer is needed. 10. The appropriate watershed district (Valle Branch) should be contacted b the develop er/en for compliance with an re the ma have. F.q(zPMPnt(z- 11. Existin draina and utilit easements alon existin lot lines within Oak Park Station will need to be vacated and new draina and utilit easements established as part of this plat. If y ou have an q uestions re this review, please contact me at (651) 604-4815. Sincerel BONESTROO, ROSENE, ANDERLIK & ASSOCIATES INC Dennis M. Postler, P.E. cc: Scott Richards — Northwest Associated Consultants, Inc. Kim Kamper, Actin Cit Administrator Ja Johnson, Public Works Director Jim Butler, Buildin Official DMP, DDH, File — Bonestroo K:15 5 \01d\Oak Park Station - P re 1. P I at & Concept De v. P lan s— 10-9 -0 1. do c Conversation Record . . .. . . .............. ..... . ........ .... . .................... ............... .... . .......... Bonestroo By: Erik Peters Date: Oct. 3, 2001 o Rosene Anderlik & Associates Project Name: oak Park Station Project No: 55 -Gen Engineers & Architects Spoke with: Doug Litterer Phone Number: 651 - 766 -0112 Title Organization: Metro Land surveying and Engineering Subject: Ponding requirements Pond Sizing for Flood Control: I clarified for Doug a few issues regarding pond design for flood control. 1. The existing HWL cannot increase to maintain existing discharge rates. Additional flood storage volume will need to be provided. The most cost effective means for the developer to provide the flood storage is to expand the existing Kerns center Pond. Expanding the Kerns center Pond is also what we as the city want to see. Centralizing the ponding allows full utilization of the added storage volume. The city also needs to have the pond expanded (see item 3). I directed him to expand the Kerns center Pond. 2. The preliminary estimate of additional flood storage volume is the runoff volume difference between existing conditions and fully developed conditions. I told him that we assumed existing conditions to be weedy, grass field with a CN of 66. He would need to estimate future build -out conditions. once we receive a grading plan with the expansion to the Kerns Pond we can determine if the discharge rate will be maintained. 3. The desired HWL for Kerns Pond is 934, however the existing HWL is 935' +. The desired HWL is based on estimated low floor elevations from adjacent properties. Today's higher HWL leaves less freeboard for flood protection. I told him that ultimately the city needs the Kerns Center Pond to have a minimum surface area of 3.5 acres at the NWL and 23.5 acre -feet of flood storage between the NWL (928.6') and HWL of 934. The pond currently has a surface area of 2.5 acres. Pond Sizing for Water Quality: 1. For water quality the wet storage is governed by two issues a. Desired average depth of 4 feet (minimum average depth of 3 feet). b. Review with the water quality model (PondNET) to restrict pollutant (phosphorus) discharge to 200 ppb outflow concentration. 2. Since this is a pond expansion and not an individual pond, use of PondNET is a little difficult for the developer to quantify given the additional offsite drainage area. Hence I told him to meet item #1 a and provide wet storage volume equal to NURP (runoff from 2.5 -inch rainfall event). Providing the NURP volume will likely be comparable with the city's water quality standard. K:\ 55\ 55GEN \Word\correspondence\DMP_EGP" conversation with Doug Littier.doc Bonestroo, Rosene, Anderllk and Associates 2335 West Highway 36 St. Paul, MN 55113 Phone: 651-636-4600 I__4 Fax: 651-636-1311