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2h. Wetland permit Walker NURP Pond Summit at Near Mtn 1 C � TY ,-% F P C DATE: 4/15/92 -- i \ \ C 11 A 1 11 A C C E CC DATE: 5/4/92 I CASE #: 92 -4 WAP 1 By: Olsen:v 1 STAFF REPORT 1 . PROPOSAL: Wetland Alteration Permit to Construct a Walker Pond Within the Upland Fringe of a Class A Wetland Iz Q LOCATION: Summit at Near Mountain I 0. APPLICANT: Lundgren Bros. 1 n" 935 East Wayzata Boulevard ' Wayzata, MN 55391 1 , 1 PRESENT ZONING: PUD -R, Planned Unit Development Residential 1 ACREAGE hen Vy City Mmintshsta DENSITY: sbnrs ADJACENT ZONING AND Rejected ed LAND USE: N - Shorewood; future single family Date mot- `i - `•' `�" I S - RSF; single family Dee submitted to Commissic 4 E- PUD -R; single family y " 1 s 9 v 1 ti W - RSF; single family Date Submitted to Cour►c+! Q WATER AND SEWER: Available to the site. I LLJ PHYSICAL CHARAC1ER.: The site is heavily vegetated with very steep slopes and a Class I A wetland on the northern edge. The site is between Lotus and Silver Lakes. M I 2000 LAND USE PLAN: Residential High Density 1 1 r Summit at Near Mountain WAP April 15, 1992 Page 2 BACKGROUND On March 23, 1992, the City Council approved the final plat for Summit at Near Mountain. The applicant is also in the process of receiving approval for final plans and specifications. As the final design of the project has been completed, staff has been able to determine the actual amount of storm water that will be created by the development of the site. This storm water runoff will be entering the Class A wetland located at the north side of the ' project through the storm water system. With the past additions to Near Mountain and Trappers Pass, storm water has either been contained within ponds on site or it has directly entered the wetland located at the northern portion of the site. Since there was no location ' on the Summit site for on -site ponding, the option to direct storm water to the wetland was going to be used. Sufficient storage area is available within the wetland due to construction of retention ponds in past Near Mountain developments adjacent this wetland. Once staff saw the amount of storm water runoff that would be entering the Class A wetland (14 acres of storm water runoff) and due to the steep terrain of the site, staff felt ' it was necessary to provide a ponding area for the runoff to be contained prior to entering the wetland. Staff therefore requested that the applicant provide a NURP pond at the base of the slope and at the edge of the Class A wetland to provide improved water quality prior to entering the Class A wetland. Storm sewers within the proposed development (the Summit at Near Mountain) are also being constructed with sump catch basins to trap larger sediments prior to reaching the NURP pond. ' ANALYSIS 1 The applicant is proposing to construct a 370' x 65' NURP pond at the base of the steep vegetated slope and at the southerly edge of the Class A wetland. The proposed pond meets the NURP standards for storm water treatment and nutrient removal. Construction of the proposed NURP pond will disturb approximately 0.8 acres, 0.45 acres of which is within the Class A wetland upland fringe. The NURP pond was located where it would ' have the least impact to the existing slope and mature vegetation, and the least impact to the Class A wetland. The proposed ponding area is being required by staff to prevent detrimental affects to the Class A wetland as a result of direct storm water runoff from the ' Summit development. Therefore, although there is an area of the wetland fringe that is being altered with the construction of the pond, the ultimate result of the installation of the pond will be an improvement to the wetland over what was previously proposed. 1 Due to the anticipated poor soils in this area, the pond's slopes of 4 to 1 may not be obtainable. Staff recommends that during the construction process, if the proposed side ' slopes are not obtainable, the slopes should be flattened out and the depth of the pond be increased to approximately 8 feet to compensate for the reduced pond volume with the flatter slopes. A two foot high berm is being constructed along the easterly half of the pond 1 Summit at Near Mountain WAP 1 April 15, 1992 Page 3 in an effort to promote water quality by discharging the water via sheet drainage into the wetland. Erosion control fence Type I is proposed between the NURP pond and the wetland to the north. It is recommended that the applicant be responsible for removal of the erosion control fence once the pond has been re- established with vegetation. PLANNING COMMISSION ACTION I The Planning Commission unanimously recommended approval of the wetland alteration permit as recommended by staff. 1 STAFF RECOMMENDATION Staff recommends the City Council adopt the following motion: I "The City Council approves Wetland Alteration Permit #92 -4 as shown on the plans dated 1 April 9, 1992, with the following conditions: 1. Due to the anticipated poor soils in this area, the pond slopes of 4:1 may not be 1 obtainable. Staff recommends that during the construction process, if the proposed side slopes (4:1) are not obtainable, the slopes should be flattened out and the depth of the pond be increased to approximately 8 feet to compensate for the reduce pond I volume with the flatter slopes. 2. The applicant shall be responsible for removal of the erosion control fence once the I • pond has been re- established. 3. Staff shall be notified 48 hours prior to initiating construction of the NURP pond and I 48 hours after the NURP pond is completed. 4. The applicant will be required to provide as-built plans of the NURP pond." I ATTACHMENTS 1 1. Memo from Dave Hempel dated April 8, 1992. 2. Planning Commission minutes dated April 15, 1992. 1 3. Plans dated April 9, 1992. 1 • 1 1 •1 CITYOF CHANHASSEN 690 COULTER DRIVE • P.O. BOX 147 • CHANHASSEN, MINNESOTA 55317 (612) 937 -1900 • FAX (612) 937 -5739 1 MEMORANDUM TO: Jo Ann Olsen, Senior Planner ' FROM: Dave Hempel, Sr. Engineering Technician ZW DATE: April 8, 1992 SUBJ: Review of Construction Plans for NURP Pond at 1 Summit at Near Mountain Wetland Alteration Permit No. 92 -4, Project No. 92 -4 ' Upon review of the construction plans prepared by Sathre - Bergquist dated April 7, 1992 for Wetland Alteration Permit No. 92 -4, I offer the following comments and recommendations: A preliminary construction plan was also sent to Ismael Martinez at Bonestroo & Assoc. for review. According to Mr. Martinez, the pond appears to be adequately ' sized from a water quality standpoint. Mr. Martinez comments are enclosed and have been incorporated into this review. Since the initial review of. the NURP pond by staff, Sathre - Bergquist has resubmitted a revised drawing incorporating some of staff's recommendations contained herein. The attached plan includes ' most of the modifications. The following conditions still should be incorporated into the conditions of approval for the wetland alteration permit. ' 1. Due to the anticipated poor soils in this area, the pond slopes of 4:1 may not be obtainable. Staff recommends that during the construction process, if the proposed side slopes (4:1) are not obtainable, the slopes should be flattened out and the depth of the pond be increased to approximately 8 1 feet to compensate for the reduced pond volume with the flatter slopes. 2. A 2 -foot high berm is being constructed along the easterly half of the ' pond in an effort to promote water quality by discharging the water via sheet drainage into the wetland. Erosion control fence (Type I) is proposed between the NURP pond and the wetlands to the north. It is ' recommended that the applicant be responsible for removal of the erosion control fence once the pond has been re- established with vegetation. ' ktm c: Charles Folch, City Engineer Ismael Martinez, BRA 1 1 t PRINTED ON RECYCLED PAPER Otto G. Borestroo. PE. Keith A Gordon, P.E. James R. Maland, P.E. Rene C. Plumart. A.I.A. I B onestroo Joseph C Anderlik, P.E. Richard W. Foster. P.E. Kenneth P Anderson, P.E. Agnes M. Ring, A.I.0 P Marvin L. Sorvala, PE. Jerry A Bourdon. P.E. Mark R. Bolts. P.E. Jerry D Pertzsch. P.E Rosene Richard E Turner, P.E. Mark A Hanson. P.E. Thomas E. Angus. P.E. Cecil* Olivier. P.E. Glenn R. Cook. P.E. David O. Loskota. P.E. Daniel J Edgerton. P.E. Gary W Morien. PE AndeNik & Thomas E. Noyes. PE Robert C. Russek, A LA Mark A. Seip. P.E. Karen L Wlemen. PE. - VI Robert G. Schunicht. P.E. Howard A. Sanford. P.E. Philip J Caswell. P.E. Keith R. Yapp, P.E. Susan M. Eberlin. C.P.A. Donald C. Burgardt. P.E. Ismael Martinez. P.E. Michael P Rau. P.E. A ssociates Ted K. Feld, P.E. Mark D. Wallis, P.E. Charles A. Erickson Michael T. Rautmann. P.E. Thomas R Anderson. A.I A Leo M. Pawelsky Robert R. Pfefferle. PE Gary F Rylander, P.E. Harlan M Olson Engineers & Architects Thomas W Peterson, PE. Miles 8 Jensen, P.E. Michael C. Lynch. P.E. L. Phillip Gravel ill. P.E MEMO 1 TO: Jo Ann Olsen, City of Chanhassen Fax No. 937 -5739 . 1 FROM: Ismael Martinez _" <� I DATE: April 7, 1992 Re: The Summit At Near Creek Mountain File No. 393Gen 1 BACKGROUND We have performed a storm water and water quality review of the proposed development -- I . The Summit At Near Creek Mountain development. This analysis concentrates mainly in the review of the proposed NURP pond design as shown in the map drawings and design 1 calculations dated.March 30, 1992, as submitted by Sathre - Bergquist, Inc. Comments were given previously to Dave Hemphill regarding the overall characteristics of the development. The NURP pond will be built in an existing wetland located downstream from the proposed I development. ASSUMPTIONS I The proposed ponds as shown in the plans will have the following parameters: 1 Bottom Elev 893.0 1 NWL 899.0 HWL Same as wetland I Maximum depth 6' Drainage area 14 Acres Wet Volume 2.2 AF I The construction of the pond will require excavation in order to obtain the bottom elevations shown above in an area where the soils are expected to be peat and muck. I 1 2335 West Highway 36 • St. Paul, Minnesota 55113 • 612 - 6364600 1 • 1 - 1 ' RESULTS We performed an analysis considering the assumptions mentioned above. The proposed ponds meets the treatment /nutrient removal criteria and can work without any significant modifications. ' COMMENTS The side slopes of the proposed pond consist of 4' horizontal at 10H:1V. The NURP ' criteria recommends benching of the first vertical 2' at a 10:1 slope for safety purposes.Due to the fact that the pond will be built in an open area in the wetland and any change in size would significantly affect the wetland vegetation. We recommend 1' vertical of benching at ' a 10:1 slope. This bench which result in 10' horizontal of emergent vegetation hopefully cattails. A cattail barrier or any other emergent vegetation would provide additional skimming. I If the soil consists of peat and muck it will be very unlikely that the side slopes would stand at 3H:1 V. In the event that a 4:1 (bottom width will be 5') is not feasible the pond would 1 significantly loose wet volume capacity for treatment. The City should certify during the construction stage what side slopes are feasible and determine what the maximum depth could be to estimate the level of treatment and the need to expand the length required. ' The plans do not specify the type of outlet, although it can be assumed that there will be by creating some sheet flow in the entire length of the pond. We recommend to define the location of the outlet preferable in the opposite side of the inlet. A 20 foot long cutoff can serve as an outlet either by leaving a bump along the pond to an elevation of 899.5 or by lowering the wall to elevation 898.5 (assuming that the Normal Water Level is 899.0) at the outlet location. ' If you have any comments please give me a call at 636 -4600. Have a nice day ! 1 1 1 1 1 1 - , n Otto G Borestroo, P.E. Keith A. Gordon. P.E Ja mes R. Maland P.E Rene C. Plumart. A.I.A. Bo nestroo Marvin L So la. PE J erry A. Bourdon. PE. Mark R. Rorfs. P , P.E �� D ertzs h. PE P ichard W Foster. P.E. Richard E Turner. P.E. Mark A Hanson, P.E. Thomas E. Angus, P.E. Cecilia Olivier. P.E. Rosene Glenn R. Cook. PE. David O Loskota, P.E. Daniel J Edgerton. P.E. Gary W Morten. P.E. • 1111 Anderlik & Thomas E. Noyes. PE Robert C. Russek. A.I.A. Mark A. Sep. P.E. Karen L Wiemeri, P.E. Robert G- Schunrcht, P.E Howard A Sanford, P.E. Philip J. Caswell, P.E. Keith R. Yapp. PE. Susan M. Eberlin, C P.A Donald C Burgardt. PE. Ismael Martinez. PE. Michael P Rau. P.E. A ssociates Ted K. Feld, P.E. Mark D. Wallis. P.E Charles A. Erickson Michael T. Rautmann, PE Thomas R Anderson, A.I.A. Leo M. Pawelsky I Robert R Pfefferle. PE. Gary F Rylander, PE. Harlan M Olson Engineers & Architects Thomas W Peterson, P.E Miles B. Jensen, PE. Michael C. Lynch. P.E. L. Phillip Gravel III, P.E MEMO 1 TO: Jo Ann Olsen, City of Chanhassen Fax No. 937 -5739 . 1 FROM: Ismael Martinez j ; , //76 DATE: April 7, 1992 Re: The Summit At Near Creek Mountain 1 File No. 393Gen 1 BACKGROUND We have performed a storm water and water quality review of the proposed development -- I The Summit At Near Creek Mountain development. This analysis concentrates mainly in the review of the proposed NURP pond design as shown in the map drawings and design L calculations dated March 30, 1992, as submitted by Sathre - Bergquist, Inc. Comments were given previously to Dave Hemphill regarding the overall characteristics of the development. The NURP pond will be built in an existing wetland located downstream from the proposed I development. ASSUMPTIONS I The proposed ponds as shown in the plans will have the following parameters: 1 Bottom Elev 893.0 1 • NWL 899.0 HWL Same as wetland 1 Maximum depth 6' Drainage area 14 Acres Wet Volume 2.2 AF I The construction of the pond will require excavation in order to obtain the bottom elevations shown above in an area where the soils are expected to be peat and muck. 1 1 2335 West Highway 36 • St. Paul, Minnesota 55113 • 612- 636 -4600 1 1 1 ' RESULTS We performed an analysis considering the assumptions mentioned above. The proposed ' ponds meets the treatment /nutrient removal criteria and can work without any significant modifications. ' COMMENTS The side slopes of the proposed pond consist of 4' horizontal at 10H:1V. The NURP ' criteria recommends benching of the first vertical 2' at a 10:1 slope for safety purposes.Due to the fact that the pond will be built in an open area in the wetland and any change in size would significantly affect the wetland vegetation. We recommend 1' vertical of benching at a 10:1 slope. This bench which result in 10' horizontal of emergent vegetation hopefully cattails. A cattail barrier or any other emergent vegetation would provide additional skimming. If the soil consists of peat and muck it will be very unlikely that the side slopes would stand ' at 3H:1 V. In the event that a 4:1 (bottom width will be 5') is not feasible the pond would significantly loose wet volume capacity for treatment. The City should certify during the construction stage what side slopes are feasible and determine what the maximum depth ' could be to estimate the level of treatment and the need to expand the length required. The plans do not specify the type of outlet, although it can be assumed that there will be ' by creating some sheet flow in the entire length of the pond. We recommend to define the location of the outlet preferable in the opposite side of the inlet. A 20 foot long cutoff can serve as an outlet either by leaving a bump along the pond to an elevation of 899.5 or by ' lowering the wall to elevation 898.5 (assuming that the Normal Water Level is 899.0) at the outlet location. If you have any comments please give me a call at 636 -4600. Have a nice day ! 1 CHANHASSEN PLANNING COMMISSION REGULAR MEETING APRIL 15, 1992 Chairman Emmings called the meeting to order at 7:35 p.m.. MEMBERS PRESENT: Tim Erhart, Ladd Conrad, Matt Ledvina, Steve Emmings and Jeff Farmakes , MEMBERS ABSENT: Brian Batzli and Joan Ahrens STAFF PRESENT: Paul Krauss, Planning Director;_Jo Ann Olsen, Senior Planner; and Sharmin Al - Jaff, Planner I PUBLIC DARING: WETLAND ALTERATION PERMIT TO CREATE A WALKER NURP POND IN A CLASS B WETLAN LOCATED ADJACENT TO SILVER LAKE AS PART OF THE PROCESS FOR THE FINAL PLAT OF SUMMIT AT NEAR MOUNTAIN, LUNDGREN BROS. CONSTRUCTION. Public Present: ' Name Address Mike Pflaum Lundgren Bros. Construction 1 Rick Sathre Sathre - Bergquist Inc. Emmings: It seems pretty straight forward. Is there anything you want 9 Y to add to the report that's here? Okay. Are there any comments from the applicant? ' Mike Pflaum: My name is Mike Pflaum. I'm with Lundgren Bros. Construction and with me is Rick Sathre of Sathre- Bergquist. The project's consulting engineers. I have no further comments but we would certainly look forward I to the opportunity to answer any questions that you might have. Emmings: And you've seen the conditions in the report as have been written, up by the staff and don't have any problems with the conditions? Okay. Thank you. This is a public hearing. Are there any members of the public here who would like to comment on this? Is there a motion to close the I public hearing? Erhart moved, Conrad seconded to close the public hearing. All voted in favor and the motion carried. The public hearing was closed. Erhart: Can someone explain how this berm works to promote water quality by discharging water, I read it twice and I don't quite understand it. Does, anybody know? Rick Sathre: The water's going to come north down through the hills it's II piped and this is the ponding... The basic idea is to have a barrier along this end of the pond that wouldn't allow the water to overflow the wetland until it ran down through the pond a ways. 5o you'd get more retention time for the water within the pond so... Erhart: What you're terming as the berm actually is that... 1 Planning Commission Meeting II April 15, 1992 - Page 2 ' Rick Sathre: Edge of the pond and then it would just be a foot or so higher than the wetland. 1 Erhart: Okay. I guess I was wondering if that was something else. Then it's clear. And the reason we don't deal with further south is because... Rick Sathre: ...the mature trees and the mature wetland. Erhart: That's my only question on that. Conrad: That's my question too. The trade off between where we put it and why not a... ' Jo Ann Olsen's statement was not picked up by the microphone. Conrad: But it is an A wetland? It is an A right? And typically we don't really allow too much dredging in an A. Olsen: The actual area... Erhart: On the map, where does the actual open water start? Rick Sathre: This is Silver Lake over here. This is Lotus Lake. This is the big mountain or the hill. This is the wet area itself. The Chanhassen border is about there so this is where that pond is purported to go. That white area is open of trees but this is trees upland down here and this is a willow orchard, shurb kind of marshy growth to the north. But you know, ' throughout that whole basin in 1987 there wasn't really any standing water. Erhart: That whole swamp filters the water as it goes towards what is that, Silver Lake? Rick Sathre: It drains right out through here. Conrad: Rick, show me again where the basin is? Rick Sathre: This is the wetland edge about like this. Then it comes up ' this way into Shorewood. So this white area here is more of an open wetland and this area is a willow...and I don't know why that has wetland characters except this might have been hayed at one point in time many ' years ago. That's in Shorewood. Jo Ann Olsen's comment was not picked up on the microphone. ' Conrad: No other alternatives? You're comfortable with it Jo Ann? Olsen: Right...I'm comfortable with it. Conrad: My only question is, it's better than what had been planned but still our standard is to try to improve things over the way they were to begin with which means today. The standard says zero. When you tamper with an A wetland, you're not saying well, when we approved the plat or plan before and this is am improvement and it is an improvement but the standard really is, as we allow dredging in wetlands, is that it's going to 1 Planning Commission Meeting April 15, 1992 - Page 3 1 improve the quality or maintain that or try to maintain whatever quality will currently have. Erhart: But do you think this improves it or degrades it? 1 Conrad: My guess is it degrades it. Erhart: Okay. Is this going to be permanent water in here? ' Rick Sathre: That would be a 6 foot deep to the middle, permanent water. It would probably develop cattails around the edge of this...380 feet wide"! and... It might make a better diversity in the wetland. I hope. Conrad: It might? Emmings: .I thought the need for this is that all of the runoff, what is all that runoff going to do to the wetland if we don't have this? Conrad: That's the other alternative. Well, you're right. Improvement I over another situation. Emmings: Yeah. So that doesn't exist yet. 1 Erhart: I'd almost look at it you're taking, what we still consider flat, taking about one acre from a Class B and turning it into a Class A wetland So in that effect it could be an improvement. Conrad: Particularly if it was a Class B. Olsen: It had the qualities of a Class 8... Conrad: Okay, no more questions. , Ledvina: In the comments in the staff report, there's a discussion regarding the peat and muck and the potential need to lessen or decrease 1 the slope. I'm wondering if you have those type of soil materials or are you going to really do a lot of, or disturb this area severely with equipment and such? And would it be even possible to get equipment down there given the occurence of the peat and muck? Rick Sathre: Well, anytime you try to get down a slope that steep to that'll site, sure. It's a probable difficulty. You wouldn't want to have to go down there very much. But the slope isn't a drop.off. It isn't thai bad so sure, it will be hard to do it but if it's something we agree is good for the environment... It will probably have to be dug out with a backhoe il or most of it... Ledvina: But any other areas that are disturbed as a result of this construction, that's outside of this specific area that you show here will I be restored? Olsen: Right...along an easement... ' Ledvina: That will be a disturbed area already? Okay. 1 Planning Commission Meeting April 15, 1992 - Page 4 Rick Sathre: I would think we would stay within the boundary of where the pond would be and take it from either side. We would be working from outside the limits of that. 1 Ledvina: Okay. So you'd be working from the inside and then just throwing it up there on the side that you create the bank? Okay. 1 Rick Sathre: I would start at the far end and work back towards our hill. Start at the west end and then... Ledvina: No further comments. Emmings: Does this pond, to be effective for this purpose, have to be maintained in the future? How do they get access to it in the future? Olsen: We do have that 20 foot easement. 1 Emmings: Easement in the same area as the pipe runs? Olsen: Correct. Emmings: Alright. I don't have anything else. Jeff? ' Farmakes: I have no further comments. Erhart: Is it to be reseeded? The berm is seeded, is.that what it is? Rick Sathre: Yes. Erhart: And what kind of vegetative cover are you putting on that? Olsen: You can dictate exactly what kind that needs. Erhart: Some of the things that we're talking about in our storm water ' committee is mitigation where given some thought, there's seeds available that are more diverse in terms of wildlife. Olsen: Than just a MnDot mix, yeah. Erhart: Right. Maybe you could just provide the developer with a list of those. Olsen: That list that we have? Erhart: Yeah. Olsen: Okay. Emmings: Anymore, have you got anything or is there a motion? ' Erhart: I'll move the Planning Commission recommend approval of Wetland Alteration Permit #92 -4 as shown on the plans dated April 9, 1992 with the four conditions listed in the staff report. 1 1 Planning Commission Meeting April 15, 1992 - Page 5 Farmakes: I'll second that. 1 Emmings: It's been moved and seconded. Is there any further discussion? Erhart moved, Farmakes seconded that the Planning Commission recommend approval of Wetland Alteration Permit *92 -4 as shown on the plans dated April 9, 1992, with the following conditions: 1. Due to the anticipated poor soils in this area, the pond slopes of 4:1 may not be obtainable. Staff recommends that during the construction process, if the proposed side slopes (4:1) are not obtainable, the slopes should be flattened out and the depth of the pond be increased to approximately 8 feet to compensate for the reduced pond volume with the flatter slopes. 1 2. The applicant shall be responsible for removal of the erosion control fence once the pond has been re- established. 3. Staff shall be notified 48 hours prior to initiating construction of the NURP pond and 48 hours after the NURP pond is completed. 4. The applicant will be required to provide as -built plans of the NURP II pond. All voted in favor and the motion carried. 1 CONCEPT PLAN AND REZONING FOR A CONFERENCE /SPA CENTER ON 19+ ACRES OF PROPERTY ZONED A2. AND LOCATED AT 1350 FLYING CLOUD DRIVE (FORMER ASSUMPTION SEMINARY PROPERTY). LELAND GOHLIKE. Public Present: ' Name Address Leland Gohlike Applicant Jennifer Luhrs Representative for Applicant Everette Olson 1675 Flying Cloud Drive Joe Huber 1458 Goodrich, St. Paul Mike Huber 1746 Presidential Lane, Shakopee Debra T. Olufson 761 Sierra Trail Anne Karels- Delaney 1161 Sluff Creek Drive Lee K. Anderson 10441 Bluff Circle Sharmin Al -Jaff presented the staff report on this item. Emmings: Let's see. This isn't really a public hearing. Are people here in the audience who have come because of this proposal? Okay. The applicant is here too with a presentation I think and Paul, did you preceive that this would be open up to the people who are here for comments? • 1 Krauss: I think so Mr. Chairman. That would be useful so the point of a 1