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3a Seminary Fen Setback CITYOF 690 City Center Drive PO Box 147 Chanhassen, Minnesota 55317 Phone 952.937.1900 Generd Fax 952.937.5739 Engineering Deparm~ent Fax 952.937.9152 Building Departnu~tt Fax 952.934.2524 Web Site www. cl. cha,hassen, mn. tv MEMORANDUM To: Todd Gerhardt, Acting City Manager From: Loft Haak, Water Resources Coordinator Date: July 10, 2001 Re: Calcareous Fen Setback PURPOSE Following a visit to the Assumption Seminary site and conversations with representatives from several governmental agencies on June 4, 2001, Commissioners Sacchet and Kind requested that staff explore an increased 'setback-for the Seminary Fen to Protect it from potential damage (water quality decrease, loss of ecosystem, loss of rare plants) and to prevent exotic species from invading and out-competing native plant species. This memo outlines staff recommendation regarding an increased setback from calcareous fens. BACKGROUND The Seminary Fen is located in the southern portion of Chanhassen, west of Bluff Creek Drive and south of the Hennepin County Regional Trail Corridor. The 90 acres of calcareous seepage fens are within a 500-acre wetland complex that also contains wet meadows, emergent marshes, and shrub swamps. _ The City of Chanhassen has significant precedent in determining the Seminary Fen to be important to the community and worthy of protection. The Seminary Fen has been identified in the Surface Water Management Plan (Attachment 1), the Bluff Creek Watershed Natural Resources Management Plan (Attachment 2), and the City of Chanhassen's Comprehensive Plan (Attachment 3) as the highest priority for conservation. The Surface Water Management Plan states that the fen should be protected from developmental impacts in the adjacent uplands and in-flowing water by use of upland buffer zones and setbacks. The Bluff Creek Watershed Natural Resources Management Plan states that "the Seminary Fen should receive the highest level of protection to avoid declines in wetland quality... [as it] is an ~e Cit~ o£Cbanbassen. A ,~,'owine community with clean lakes, cluality schools, a charmin¢ downtown, thrivine businesses, and beautihd oarks. A ereat dace to live, work. a,d Calcareous Fen Setback July 10, 2001 Page 2 extremely rare type of wetland found in the state." It also reflects a desire to see the areas preserved as a natural area, or protected with conservation easements. In the Comprehensive Plan, it is said, "preserving and protecting this resource should be at the top of the city's wetland protection and preservation policies." The Seminary Fen is a high regional priority for the Department of Natural Resources (DNR), and it is protected by the Wetland Conservation Act (Attachment 4). Because calcareous fens are so rare, they have special status in the state wetland law. The current wetland setback for a pristine wetland in the City of Chanhassen is 100 feet, with a buffer strip of 20-100 feet, and a minimum average width of 50 feet (see Attachment 5). The Seminary Fen complex is currently classified as "pristine" because of the high quality of the ecosystem and the presence of rare plants. It is the only pristine wetland complex remaining within Chanhassen. RATIONALE The Seminary Fen is of great value to the City of Chanhassen for several reasons: . Fens have a variety of functions necessary to the survival of diverse ecosystems in the surrounding area. They control floods, filter pollutants from water, sustain biodiversity, provide plant and animal habitats, contribute to the water flow, and store carbon in their peaty' soils, which aids in the healthy development of plants. 2. The Seminary Fen is one of Minnesota' s rarest plant communities and is home to eight rare plants including three "special concern" species (Twig rush, Marsh arrow-grass and Small white lady' s slipper) and five "threatened" species (Sterile sedge, Beaked spike rush, Hair- like beak rush, Whorled nut rush and Valerian). . The Seminary Fen is a calcareous fen. Calcareous fens are created when cold ground water picks up dissolved calcium and magnesium as it flows through hillsides rich in these minerals. These fens are extremely rare. They create a unique set of ecological conditions: there are specific types of plants that exist in, and prefer, the cold and alkaline water. Twenty percent of approximately five hundred calcareous fens in the world are in Minnesota. The Seminary Fen makes up five percent of the area of all the fens in Minnesota. 4~ The Seminary Fen is relatively untouched: it is in its pre-settlement condition. However, exotic species such as leafy spurge and buckthorn are currently hovering on the edge, ready to invade the fen. Thus, a management plan is needed in the near future to preserve the existing ecosystem. The City of Chanhassen has joined with other governmental and non- governmental organizations to apply for a DNR Greenways Planning Grant. The grant would help fund the development of a Stewardship and Protection Plan for the Assumption Seminary area. Working with the Lower Minnesota River Watershed District (LMRWD), the City would provide the residents of the area with: information about the uniqueness of Calcareous Fen Setback July 10, 2001 Page 3 Assumption Creek, the Seminary Fen, and the surrounding area; several means by which residents can protect their properties; and an opportunity to be involved in the development of the stewardship and protection plan. 5~ Assumption Creek contains a naturally reproducing trout population. Creeks like Assumption Creek are extremely rare natural formations. Assumption Creek is codependent with the calcareous fen for minerals and groundwater and would thus be negatively impacted if the fen were to decrease in size or quality. Assumption Creek is one of 15 streams in the Metro area with a naturally reproducing trout population, and the only one in the West Metro with a native brook trout population. OTHER CALCAREOUS FENS The two calcareous fens in closest proximity to the Assumption Seminary property are the Savage Fen in Savage and the Nelson Fen near Stewartville. Savage .The Savage Fen is a 425-acre wetland complex owned by the U.S. Fish and Wildlife Service (USFWS) and private owners. It sits amid highways, housing developments, and industrial buildings in Scott County. The-calcareous fen is in the heart of the wetland complex and _. comprises 64 acres. In 1997, there was question as to whether Scott County officials could build a four-lane highway through the center of the complex, and they requested a bridge be allowed to span the fen. However, the Minnesota Environmental Partnership said that bridge construction would alter the fen's hydrology, and road salt could destroy rare plants. These changes could have threatened the wetland' s survival and allowed exotic species to invade. Because of the potential dangers to the ecology of the fen, the proposal of the bridge and highway construction was defeated. A traffic analysis study was completed in 1999 to determine a route for a new highway in the vicinity of the fen, but it indicated that a road through the fen would not ease congestion in the Savage area. Possible road construction is not the only danger to the Savage Fen. Increased groundwater withdrawal for public water supply in this sensitive area has lowered the water table and adversely affected the calcareous fen. Savage does not currently have a fen setback in place. Stewartville The Nelson Fen is a very small calcareous fen located within a Wildlife Management Area (WMA) in Olmsted County. The fen itself occupies less than one acre within the 80 acre WMA, and a shrub meadow wetland surrounds the fen. There are three state threatened species that live within the Nelson Fen: sterile sedge, valerian, and beaked spike rush. The active management of this WMA consists mainly of prescribed burning. Calcareous Fen Setback July 10, 2001 Page 4 PERTINENT ITEMS Staff has identified the following items that should be taken into consideration as the City contemplates the adoption of a fen setback: 1. There is no precedent in this area. The protective buffers around both calcareous fens are on state-owned land. 2. Though the setback will be more restrictive and thus serve to protect the fen, it will still allow development near the fen, and it acknowledges that development may take place if the land remains in private ownership. 3. The land on which the fen is located is zoned primarily A-2 (Agricultural Estate). The minimum lot size for A-2 is 2 V2 acres and a 1-unit per 10-acres density must be maintained. A portion of the land is zoned RR (Rural Residential). The minimum lot size for RR is 2 V2 acres and a 1-unit per 10-acres density must be maintained. Staff anticipates that, in most cases, the large lots will be able to accommodate a structure that meets the required setbacks. (Staff will provide more details at the Planning Commission meeting.) 4. The City has been encouraged by the DNR, Friends of the Minnesota Valley, the U.S. Fish and Wildlife Service, the LMRWD, and the Minnesota Land Trust to create.-a fen setback. 5. Anything that affects the complex hydrological balance of precipitation, sUrface water flow, and groundwater discharge that provides water for the fen can lead to its degradation. 6. Hydrologic information has not been compiled for the fen because a comprehensive hydrologic study could be destructive to the fen and there would be a negative net gain. Staff is unsure as to the extent of the wetland and fen recharge area; however, increasing the setback would certainly enlarge the amount of recharge area under City protection. 7. According to the Center for Watershed Protection (CWP), increases in the amount of impervious surface (such as pavement) near creeks or wetland areas can have negative impacts on the adjacent water bodies. Citing many independent lines of research, the CWP states that it is extremely difficult to maintain predevelopment quality when watershed development exceeds 10 to 15% impervious cover. Staff has estimated the amount of impervious surface in the watershed to be 5% at present. 8. A setback of 100 feet is necessary for good quality maintenance and protection, according to an Iowa State impact study. To achieve the optimal level of protection, a buffer is also required. 9. A setback with a buffer requirement would prevent the intrusion of non-native plant species to some extent and would help to preserve rare plant species, habitat diversity, and the overall integrity of the ecosystem. 10. According to a study conducted by the Minnesota Storm Water Advisory Group in 1997, wetland buffers should be 25 feet for minimum benefits, and 150 feet or more for the protection of sensitive species. Standards should be increased for higher functions, such as trout streams. The best-suited riparian buffers are more complex combinations of herbaceous and woody native species suited to the area. Calcareous Fen Setback July 10, 2001 Page 5 11. In a study done in 1992, the Shorelands and Coastal Zone Management Program of the Washington Department of Ecology found that to prevent significant water quality impacts, the buffer needs to be 100 feet or greater. Furthermore, buffers need to retain plant structure for a minimum of 200 to 300 feet beyond the wetland to retain wetland- dependent wildlife. RECOMMENDATIONS Staff recommends that the Planning Commission recommend the City Council approve the following motions: "Section 20-403 shall be modified to read: (c) Wetland types. This article establishes three (3) four (4) wetland types and one body type. Wetlands, ag/urban. Wetlands that have been influenced by agricultural or urban (residential, commercial, or industrial) land usage are called ag/urban. Influences include: over nutrification, soil erosion and sedimentation, and water quality degradation. As a result of these influences there is a loss of plant species diversity, over-crowding and domination by invasive species such as reed canary grass, and reduction in wildlife habitat. (2) Wetlands, natural. Natural wetlands are still in their natural state and typically show little sign of impact from surrounding land usage. The vegetative communities of these wetlands are characterized by a diversity of plant species with mixed dominance of species. Other key factors include: presence of natural indicator species, good wildlife habitat, and being aesthetically pleasing. (3) Wetlands, pristine. Wetlands that exist in a natural state and have special and unusual qualities worth protecting at a high level are called pristine. These qualities include: outstanding vegetation community, native species population, rare or unusual species present, and habitat for rare wildlife species. (4) Utilized. Utilized water bodies created for the specific purpose of surface water runoff retention and/or water quality improvements. These water bodies are not to be classified as wetlands even if they take on wetland characteristics. Wetland alteration permits shall not be required to undertake work on these water bodies. (2) Calcareous Fen. A calcareous fen is a peat-accumulating wetland dominated by distinct groundwater inflows having specific chemical characteristics. The water is characterized as circumneutral to alkaline, with high concentrations of calcium and low dissolved oxygen content. The chemistry provides an environment for specific and often rare hydrophytic plants. Calcareous Fen Setback July 10, 2001 Page 6 and "Section 20-406 shall be modified to read: (c) For lots of record containing or abutting a calcareous fen, the following minimum provisions are applicable: (1) Structures shall maintain a minimum setback of 150 feet; and (2) Prairie buffer shall be established and/or maintained within the entire 150-foot setback." ATTACHMENTS 1. Excerpt from Surface Water Management Plan, 1994. 2. Excerpt from Bluff Creek Watershed Natural Resources Management Plan, 1996. 3. Excerpt from City of Chanhassen Comprehensive Plan, 1998. 4. Minnesota Wetland Conservation Act re. Calcareous Fens (MR 8420.1010) 5. Wetland Setbacks, Chanhassen City Code, Sections 20-403 and 20-406. 6. Proposed Ordinance g:Xeng~lonXmemosXfen setback - cc report.doc 4 Proposed improvements at Ponds LOM-P1.3, LOM-P1.4, LOM-P1.8, and LOM-PI.12 described in Section IV-J3. and Appendix C are high priority, highly efficient improvements which contn'bute the most to enhance the water quality of the pristine wetlands. ~ Wetlands Wetlands A34-8(1) and A34-12(1) should be protected from impacts of development of adjacent uplands and from in-flowing water by use of upland buffer zones and minimum setbacks as detailed in the Ordinance. Wetlands A34-8(1) and A34-12(1) should be improved by allowing more water to pass through the railroad grade in the northern portion of A34-12(1). 3~ 4. Wetlands such as A27-16(1) and A27-16(2) should be protected by implementing the upland buffer zones and minimum setbacks as detailed in the Ordinance. . . Purple loosestrife population center at wetland A34-8(1) should be treated in accordance with State guidelines. : IV-K Drainage to Neighboring Communities IV-ICl Drainage to Christmas Lake Watershed Description: The portion of Chanhassen draining to Christmas Lake is located at the north central boundary of the City with a total area of about 234 acres. This area does not receive any runoff from other watersheds inside or outside the City. Topography within the area is fairly steep with a lot of small depressions, wetlands and ponds. Land surface elevations range from about 1,040 feet to 930 at Christmas Lake shoreland. The Christmas Lake area is fairly well developed (about 75%). ., System Description IV-I79 considering the highly developed nature of the watershed that surrounds it. F2. Greenwauj The design of the trails and park system should continue to move forward as the Park and Recreation Commission recommends and under the viewpoints discussed above. Development of the land and transportation routes should continue to move forward with Watershed-Based Zoning and Cluster Development and protection of the primary and secondary zones as discussed in section V.E. The East Gorge area is erosive and it is important that the City require setback regulations beyond the existing bluff ordinance to protect the spring-fed creek. This may require an amendment to the existing bluff ordinance. Much of the area appears to already be divided into large lot residential home sites. Future development would target further subdivision of parcels. The City's efforLs to manage this area should focus on cooperative agreements to protect the area, especially the southern areas where higher quality exists. IV, G Region 5- 5eminlc]r~3 Fen · Approach The Seminary Fen should receive the highest level of protection to avoid declines in wetland quality. This wetland should remain connected to the lower gorge area of Bluff Creek. Naturally reproducing trout within the creek on this property should also be protected. The Seminary Fen is an extremely rare type of wetland found in the state and should be protected from encroachment due to draining, filling and exotic species (see Figure 14). To retain groundwater discharge into this area, development should-be restricted on the bluff top areas so that recharge of groundwater may ocdur. Buffer strips should be a minimum of 100 feet on all sides of this wetland. Disturbances, such as vegetation removal, should not be allowed. This wetland should remain connected to the lower gorge area of Bluff Creek. Naturally reproducing trout within the creek on this property should be protected as well. Bluff Cree~ watershed Natural Re~ob~rce~ Management Plan G.2 ~r~svtwatj. The design of the trails and park system should continue to move forward as the Park and Recreation Commission recommends and under the viewpoints discUssed above. Development of the land and transportation routes should continue to move forward with Watershed-Based Zoningand cluster development and protection of the primary and secondary zones as discussed in section V.E. The City should consider a variety of land uses in this area and should choose the use that is most protective to the area. If possible, a means for limited access for education purposes would be ideal. Maintenance of the fen and trout stream is also important. Therefore, it is practical that lands that are for' sale be acquired and preserved as a natural area. Lands that are not for sale should be protected with conservation easements. IV, H Education The goals for the educational component of the plan were established ' after the following portion of the Steering Committee Vision: _ "...Tine creek serves as a field laborator7 for tt,e schools, teachers and community in order to develop a Stewardship of the land:..." The implications of the vision require tine development of a watershed awareness program for the entire com~nunity (school, otizens, etc.) so tlnat the plan implementation prc, cess is part of an ongoing community education and involvement effort. There are some constraints, i.e., the need for- teacher training time, curriculum develop~nent, field trips, and suppo~-t fi-om the school principals. The awareness program will focus on actively engaging children, ranches. and the general public in lear'ning about Bluff C~'eek, its ecological and cultural characteristics and role. it ,will also consider ways fo~- ti~e pubhc and special groups (nature societies, sclnools, corporate volunteers, 8acden clubs, etc.) to participate in corridor research, restoration, monitoring and demonst~-ation projects. The program will emphasize the need for' co~-~ ~munity support beyo~d private needs to .public support and involvement and the collaboration w~th other educational, community and business entities. The City has initiated efforts to acquire a 100-acre parcel to develop an interpretive nature center in the upper reaches of the watershed between the Minnesota Arboretum and the school site, south of Highway 5 and Bluff Cree~ water~ed I'lah4ral Re~ource~ Management Plan COMP REHENSIVE PLAN 1998 With the increase in Chanhassen's population in recent years, the boat traffic on city lakes has also increased. by either agricultural or urbanization activities. Utility wetlands are water bodies specifically created to manage surface water created by development. As property taxes on lakeshore lots continually increase, the demand for services to manage the ~/_._ problems arising on city lakes will also increase.~, Future lake management within Chanhassen will be finding the balance of protecting and improving water quality, preventing overuse and abuse of the resources, while maintaining accessibility for all Cha~hassen residents. WETLANDS The Seminary Fen located north of Hwy. 212, in the southwest corner of the city, is the only wetland classified pristine. In 1995, the Seminary Fen was identified by the Minnesota Biological Survey as the most important site in all of Hennepin, Carver and Scott Counties. There are approximately 90 acres of calcareous seepage fen in this area with rare and threatened plant species. Preserving and protecting this resource should be at the top of the city's wetland protection and preservation policies. In 1992, the state of Minnesota passed the Wetland Conservation Act (WCA), which put wetland protection and preservation into law. The goal of this act is to replace wetlands lost to previous activil~es and to prevent the loss of existing wetlands. Wetland identification and protection have become integral parts of all development throughout the entire state, including Chanhassen. The City of Chanhassen, who has had wetland ' protection ordinances in place since 1980, has continued to take the lead on the issue of wetlands and their protection. The city's 1994 Surface Water Management Plan (SWMP)included identification and reclassification of wetlands within the city. Low areas were identified as possible wetland sites. Wetland specialists made field identification of these sites and detailed data sheets documenting vegetation, landscape and existing conditions were compiled. These data sheets serve only as a guide for the city and are not to be used as the defining wetland boundaries. Wetland boundaries are to be determined by professional delineations conducted by parties who propose to impact or develop land in and around these areas. In addition, any proposed development will be required to delineate their sites for the existence of wetlands. From this study, a wetlands map was generated and a new wetland classification system was implemented, replacing the state's classification system. The city went to four levels of wetland identification; Pristine, Natural, Ag/Urban and Utility. Pristine wetlands were identified as wetlands that remain in their naturaJ state and have special and unusual qualities worth protecting. Natural wetlands are wetlands that still exist in their natural state and typically show little sign of impact from surrounding land use. Ag/urban wetlands have been impacted With the change in wetland laws, the regulation of wetlands has also. changed. The State of Minnesota appointed the Minnesota Board of Water and Soil Resources (BWSR) to oversee the regulation of the WCA. BWSR, in return, appointed Local Governing Units (LGUs) to implement the WCA for wetland activities. Chanhassen was' appointed as LGU for activities in its own city. This change gave Chanhassen some responsibility and control over wetland activities, but permits and approval were still required from the Army Corps of ..Engineers, the Minnesota Department of Natural · Resources, Minnesota Pollution Control Agency and local watershed districts. In an attempt to simplify regulation, Chanhassen was one of a select few LGUs selected to participate in a program which would make LGUs the sole governing agency in cases where wetland impacts are less than three acres. In addition, 1996 revisions to the WCA allowed LGUs _to develop their own comprehensive wetland plans. The City of Chanhassen has submitted a draft plan to BWSR, and because of previous work done in the SWMP, the city is in the final stages of having their plan approved. 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'~,uo!ss!mmoa ,q{ Xq po^o~dd~ u~ld luomo~}mmm ~ u! ,oj pop!AoJd s~ ldo:)xo p,p~,~op ao p,~,ll~ ,sl~,tllO ,o poilU Jo pou!mp oq lou Xinu suoj snomu~l~D 'fi;lqV'ld .LIq.';ilAI~IDVIqVIAI 0i~01'0~;t'8 t, Lg tls 81 :£SIH ~;g£i;'flt;01 '.IOI'1ti~01 '.90't'l s SIAI :H£flV £V. IS · umlnq!a;s!p jaqlJnj .moq oq~ ol suoj snooxeol~a jo ls!l pompdn tm ~p!^o~d iI~qs ~oumss~mmo, oql 'D 'uo!leooI ~loql pu~ ,llqs § 20°402 CH_ANHASSEN CITY CODE (6) (?) (8) (9) (10) Restricting and controlling the harmful effects of land development on wetlands. Allowing only development that is planned to be compatible with wetland protection and enhancement. Providing standards for the alteration of wetlands when alteration in allowed. Mitigating the impact of development adjacent to wetlands. Educating and informing the public about the numerous benefits and features of wetlands and the impacts of urbanization. (11) Obtaining protective easements over or acquiring fee title to wetlands as appropriate. (Ord. No. 180, § 1, 12-14-92) Sec. 20-403. Delineation of wetlands. (a) Generally. Wetlands shall be subject to the requirements established herein, as well as restrictions and requirements established by other applicable city ordinances and regulations. The Wetland Protection Regulations shall not be construed to allow anything otherwise pro- hibited in the zoning district where the wetland area is located. \ (b) Boundaries; maps. A wetland is'land that meets the definition of "wetlands" set forth in this article. Wetland boundaries and wetland types, as established by officially adopted city maps, shall be prima facie evidence of the location and type of wetland. The official maps shall be developed and maintained by the planning department. If an applicant questions whether a wetland exists or disputes its delineation, the applicant shall have the burden to supply detailed information for reviews supporting the applicant's position. The applicant shall pro- vide appropriate technical information, including, but not limited to, topographical survey and soil data deemed necessary for the city to determine the exact wetland boundary. The planning director shall make a determination to maintain the officially designated wetland boundary or if th~ boundaries need to be corrected on city plans and maps based upon the data that is supplied. Data for wetland determination shall be certified by a registered engineer, surveyor, or a qualified wetland consultant. The applicant may appeal the planning director's determi- nation of the wetland boundary and type to the city council. (c) Wetland types. This article establishes three (3) wetland types and one body type: .(1) (2) Wetlands, ag/urban. Wetlands that have been influenced by agricultural or urban (residential, commercial, or industrial) land usage are called ag/urban. Influences include: over nutrification, soil erosion and sedimentation, and water quality degra- dation. As a result of these influences there is a loss of plant species diversity, over- crowding and domination by invasive species such as reed canary grass, and reduction in wildlife habitat. Wetlands, natural. Natural wetlands are still in their natural state and typically show little sign of impact from surrounding land usage. The vegetative community of these wetlands are characterized by a diversity of plant species with mixed dominance o£ species. Other key factors include: presence of natural indicator species, good wild- life habitat, and being aesthetically pleasing. Supp. No. 7 1188.2 ZONING § 20-406 (3) Wetlands, pristine. Wetlands that exist in a natural state and have special and unusual qualities worth protecting at a high level are called pristine. These qualities include: outstanding vegetation' community, native species population, rare or un- usual species present, and habitat for rare wildlife species. (4) Utilized. Utilized water bodies created for the specific purpose of surface water runoff retention and/or water quality improvements. These water bodies are not to be classified as wetlands even if they take on wetland characteristics. Wetland alteration perm/ts shall not be required to undertake work on these water bodies. (Ord. No. 180, § 1, 12-14-92) Sec. 20-404. No net loss. To achieve no net loss of wetland, except as provided under section 20-416 of this article, or authorized by a wetland alteration permit issued by the city, a person may not drain, grade, fzll, burn, remove healthy native vegetation, or otherwise alter or destroy a wetland of any size or type. Any alteration to a wetland, permitted by a wetland alteration permit must be fully mit/gated so that there is no net loss of wetlands. (Ord. No. 180, § 1, 12-14-92; Ord. No. 202, § 2, 4-25-94) Sec. 20-405. Standards. The following standards apply to all lands within and abutting a wetland: (1) Septic and soil absorption system must be a setback minimum of seventy-five (75) feet from the ordinary high water mark of the wetland. (2) The lowest ground floor elevation is two (2) feet above ordinary high water mark of the wetland~ (3) Docks or walkways shall be elevated six (6) to eight (8) inches above the ordinary higI~ water mark or six (6) to eight (8) inches above the ground level, whichever is greater. (4) Access across a wetland shall be by means of a boardwalk and only upon approval of a wetland alteration permit. (5) The city's Best Management Practices Handbook shall be followed. (Ord. No. 180, § 1, 12-14-92; Ord. No. 202, § 3, 4-25-94; Ord. No. 240, § 11, 7-24-95) ,-~ Sec. 20-406. Wetland buffer strips and setbacks. (a) For lots created after December, 14, 1992, (date of ordinance adoption), a buffer strip shall be maintained abutting all wetlands. All existing vegetation adjacent to a wetland shall be left undisturbed and applied toward the buffer strip unless otherwise approved by city council. Buffer strip vegetation shall be established and maintained in accordance to the following requirements. If the buffer area is disturbed, plant species shall be selected from wetland and upland plants to provide habitat for various species of wildlife. Buffer strips shall be identified by permanent monumentation acceptable to the city. In residential subdivisions, a monument is required for each lot. In other situations, a monument is required for each three SuM No. 8 1188.3 § 20-406 C~SEN CITY CODE hundred (300) feet of wetland edge. The buffer strips and structure setbacks shall meet the following standards: 'Wetland 2~pe Pristine Principal Strut- 100' tare Setback · BufTer Strip 20--100' Natural Ag I Urban Utilized 40' measured 40' measured 0' from the out- from the out- side edge of the side edge of the buffer strip buffer strip 10---30' 0--20' 0' Buffer Strip Miuimum Aver- age Width 50' 20' 10, O' % of Native Vegetation in Buffer Strip Entire Entire Optional Optional The dimensions of the buffer strips may be adjusted by the city based upon the quality of the wetland, local topographic conditions, and the type and design of development being proposed. The table above provides minimum and maximum dimensions for the buffer strip. The use of a meandering buffer strip to maintain a natural appearance is encouraged. Where roadways are constricted next to a wetland, the average buffer strip width for the adjacent wetland shall Supp No. S 1188.4 ZONING § 20-407 be maintained. Structure setbacks are also described in the table. On single-family subdivi- sions in the RSF district, the applicant must demonstrate that each lot provides sufficient area to accommodate the applicable front yard setback, sixty-foot by forty-foot deep building pad, and a thirty-foot rear yard area. All of these elements must be provided outside of designated wetland and buffer strip areas. (b) For lots of record on December 14, 1992 (date of ordinance adoption) within wetland areas and for lands abutting a wetland area, the following minimum provisions are applicable unless alternative plans are approved by the city under a wetland alteration permit: · Pristine Natural Ag / Urban Utilized Setback Princi- 100' 75' 75' 0' pal Structure The city may approve reduced wetland setbacks as outlined in subparagraph (a) above. (Ord. No. 180, § 1, 12-14-92; Ord. No. 240, § 12, 7-24-95) Sec. 20-407. Wetland alteration. (a) An applicant for a wetland alteration permit shall adhere to the following principles in descending order of priority: (1) Avoiding the direct or indirect impact of the activity that may destroy or diminish the wetland; (2) Minimizing the impact by limiting the degree or magnitude of the wetland activity and its implementation; (3) Rectifying the impact by repairing, rehabilitating, or restoring the affected wetland activity and its implementation; (4) Reducing or eliminating the impact over time by preservation and maintenance operations during the life of the activity; and (5) Replacing unavoidable impacts to the wetlands by restoring or creating substitute wetland areas having equal or greater public value as set forth in Minnesota Rules 8420.0530 to 8420.0630. Co) A wetland alteration permit shall not be issued unless the proposed development complies within the provisions of the Mitigation Section of this article, as well as the s~ndards, intent, and purpose of this article. (c) The treatment of wetlands to control nuisance algae. (1) The city must be notified prior to the use of any form of treatment. (2) At the time of notification, a person or company will be required to supply the following information: a. Location of pond. b. Area of pond to be treated. 1188.5 CITY OF CHANHASSEN CARVER AND HENNEPIN COUNTIES, MINNESOTA ORDINANCE NO. AN ORDINANCE AMENDING CHAFFER 20 OF THE CHANHASSEN CITY CODE, THE ZONING ORDINANCE The City Council of the City of Chanhassen ordains: Section 1. Section 20-403 (c) Delineation of wetlands shall be modified to read as follows: (c) Wetland types. This article establishes threc (3) four (4) wetland types and one body type. O) Wetlands, ag/urban. Wetlands that have been influenced by agricultural or urban (residential, commercial, or industrial) land usage are called ag/urban. Influences include: over nutrification, soil erosion and sedimentation, and water quality degradation. As a result of these influences there is a loss of plant species diversity, over-crowding and domination by invasive species such as reed canary grass, and reduction in wildlife habitat. (2) (3) Wetlands, natural. Natural wetlands are still in their natural state and typically show little sign of impact from surrounding land usage. The vegetative communities of these wetlands are characterized by a diversity of plant species with mixed dominance of species. Other key factors include: presence of natural indicator species, good wildlife habitat, and being aesthetically pleasing. Wetlands, pristine. Wetlands that exist in a natural state and have special and Unusual qualities worth protecting at a high level are called pristine. These qualities include: outstanding vegetation community, native species population; rare or unusual species present, and habitat for rare wildlife species. (4) Utilized. Utilized water bodies created for the specific purpose of surface water runoff retention and/or water quality improvements. These water bodies are not to be classified as wetlands even if they take on wetland characteristics. Wetland alteration permits shall not be required to undertake work on these water bodies." (5) Calcareous Fen. A calcareous fen is a peat-accumulating wetland dominated by distinct groundwater inflows having specific chemical characteristics. The water is characterized as circumneutral to alkaline, with high concentrations of calcium and low dissolved oxygen content. The chemistry provides an environment for specific and often rare hydrophytic plants. Section 2. Section 20406 Wetland buffer strips and setbacks shall be modified by adding the following: (c) For lots of record containing or abutting a calcareous fen, the following minimum provisions are applicable: (I) Structures shall maintain a minimum setback of 150 feet; and (2) Prairie buffer shall be established and/or maintained within the entire 150-foot setback. Section 3. This ordinance shall be effective immediately upon its passage and publication. PASSED AND ADOPTED by the Chanhassen City Council this day of ,2001. ATTEST: Todd Gerhardt, Acting City Manager Linda C. Jansen, Mayor (Published in the Chanhassen Villager )