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B. Surface Water Management Plan AmendmentCITY OF Metropolitan Land Planning Act Planning & MEMORANDUM CHMBMSEN Metropolitan Land Planning Act. This act was passed because "problems of Fax: 952.227.1110 • , City g i En ineer/Public Works Director TO. Paul Oehme 7700 Market Boulevard is intended to coordinate local planning efforts, programs and controls to "protect PO Box 147 Chanhassen, MN 55317 FROM: Terry Jeffery, Water Resources Coordinator d y y 7901 Park Place - Phone: 952.227.1300 DATE: May 14, 2012 Administration Section 473.859 subdivision 2 (a) requires that the "land use plan shall include the Phone: 952.227.1100 SUBJ: Comprehensive Land Use Plan Amendment Resulting from Fax: 952.227.1110 Surface Water Management Plan Amendment Building Inspections Minnesota Water Law Phone: 952.227.1180 ISM Fax: 952.227.1190 Engineering Under Minnesota State Statute, the City of Chanhassen must update the Second Phone: 952.227.1160 Generation Surface Water Management Plan which is one element of the Fax: 952.227.1170 Comprehensive Plan. Finance Phone: 952.227.1140 BACKGROUND Fax: 952.227.1110 There are a number of laws and permits at the federal and state level that require Park & Recreation the City to develop and amend a surface water management plan and local Phone: 952.227.1120 controls. It is the overall intent of the surface water management plan to provide Fax: 952.227.1110 one central plan for managing our surface waters and should consider the evolution of surface water management science. These laws, permits and Recreation Center paradigm shifts in surface water management are briefly discussed in the 2310 Coulter Boulevard Phone: 952.227.1400 following sections. Fax: 952.227.1404 Metropolitan Land Planning Act Planning & Minnesota Statutes Chapter 473, Sections 473.851 to 473.871 is known as the atural Resources Phone: l Res rce Metropolitan Land Planning Act. This act was passed because "problems of Fax: 952.227.1110 urbanization and development transcend local government boundaries ". This act is intended to coordinate local planning efforts, programs and controls to "protect Public Works the health, safety and welfare of the residents of the metropolitan area and to 7901 Park Place ensure coordinated, orderly and economic development",. Phone: 952.227.1300 Fax: 952.227.1310 Section 473.859 subdivision 2 (a) requires that the "land use plan shall include the water management plan required by section 103B.235 ". Senior Center Phone: 952.227.1125 Fax: 952.227.1110 Minnesota Water Law Minnesota Statutes, Chapters 103A through 103G are collectively known as the Web Site Minnesota Water Law. Of particular importance to the management of water www.ci.chanhassen.mn.us resources within Chanhassen is the Metropolitan Surface Water Management Act (103B.201- 103B.253) and the Comprehensive Local Water Management (10313.301 — 1038.355). These statutes proscribe surface water planning requirements and implementation responsibilities to various agencies. g:\eng \terry \code ammendments\ stormwater\memo_cc_05142012.doc Chanhassen is a Community for Life -Providing for Today and Planning for Tomorrow Paul Oehme S WMP /Comp Plan Amendment May 14, 2012 Page 2 Minnesota Statute 103B.235 requires that each town with land use regulatory authority within Carver, and other select counties either prepare the Local Water Management Plan themselves or "delegate all or part of the preparation to the county The section continues on to list the required elements for the Local Water Management Plan. Minnesota Statute 103B.325, subd. 1 stipulates that "Local units of government shall amend existing water and related land resources plans and official controls as necessary to conform them to the applicable, approved local water management plan following the procedures in this section." Minnesota Statute 103B.33I, subd. 2 goes'on to state that "The county may regulate the use and development of water and related land resources within incorporated areas when one or more of the following conditions exist: (1) the municipality does not have a local water and related land resources plan or official controls consistent with the local water management plan; (2) a municipal action granting a variance or conditional use would result in an action inconsistent with the local water management plan; ..." Local Water Management Plans There are four watershed districts or joint powers agencies with Local Water Management Plans and jurisdiction in Chanhassen: • Carver County Watershed Management Organization • Lower Minnesota River Watershed District • Riley Purgatory Bluff Creek Watershed District • Minnehaha Creek Watershed District. The City adopted the Second Generation Surface Water Management Plan in August of 2006 and is due to redo the plan in 2016. Meanwhile, the four previously mentioned agencies have recently updated their local water management plans and rules per the schedule shown in the following table: ADOPTION DATES Carver 10/26/2010 Pending MCWD 7/5/2007 6/1/2011 To be compliant with Minnesota Statute, the City of Chanhassen must update our Second Generation Surface Water Management Plan (SWMP) and applicable local controls. Staff has consulted with the Metropolitan Council and has elected to wait until all four overarching local water management plans were updated prior to updating our own plan. The pending re- issuance gAeng \terry \code ammendments \stormwater\memo cc 05142012.doc Paul Oehme SWMP /Comp Plan Amendment May 14, 2012 Page 3 of the National Pollution Discharge Elimination System Municipal Separate Storm Sewer System (MS4) and the likely need to incorporate resulting language into our Local Water Management Plan provided additional rationale for delaying the plan update. National Pollution Discharge Elimination System Permits MS4 The Minnesota Pollution Control Agency is anticipating public notice of the revised draft MS4 permit in the State Register on May 14, 2012 with permit reissuance in August of 2012. As of the last draft, the City of Chanhassen would have 150 days from the date of reissuance to modify our pertinent documents. Construction Stormwater Permit The current NPDES Construction permit has language germane to our SWMP and to our local controls. The Construction permit requires infiltration for all areas discharging to impaired or special waters. The construction permit recommends infiltration for all other projects as a method for managing water quality volume. Minnesota Pollution Control Agency (Agency) Powers and Duties Minnesota Statute 115.03 Subdivision 5(c) charged the Agency with the development of "performance standards, design standards, or other tools to enable and promote the implementation of low- impact development and other storm water management techniques." This section then goes on to define low- impact development "as an approach ..... that mimics a site's natural hydrology as the landscape is developed storm water is managed on -site and the rate and volume of predevelopment storm water reaching receiving waters is unchanged." This has prompted the creation of the Minimum Impact Design Standards (MIDS) work group. This group is working to perform research on various techniques and to develop tools and standards applicable statewide to reduce the volume of water running off developed lands and to mimic natural conditions to the greatest extent practicable. Runoff Volume from 10 -Acre Site Native Conditions and De— rYi =01rsal with No ! MPG As our non - degradation plan indicated, research is showing that runoff volume is o 25 — -- - -- ". one of the biggest threats to the quality of = ` 20 Nat ve.ea our lakes, rivers, streams and wetlands. ; ` ts - C N With an increase in volume comes an . 10 • Developed increase in pollutant loading as although the _ • "- ' T Impervious Developed of a given pollutant may oeve�oped g p Zr 0 �.— � ''` Impervious remain constant it is simply a case of more A B C D Developed 'c being delivered to the receiving water. An Hydrologic Soil Group Impervious(' increase in runoff volume, and the inherent Figure 1. Increase in volume with increased hard cover by soil types decrease in groundwater infiltration also results in diminished groundwater recharge volume, increased "bounce" within our lakes and a decrease in base flow of area streams. g• \eng \terry \code ammendments\ stormwater\memo_cc_05142012.doc Paul Oehme SWMP /Comp Plan Amendment May 14, 2012 Page 4 The impact of increased runoff volumes also has a significant economic impact. Infrastructure must be upsized to accommodate increased flows. System failures become more common and reactive maintenance becomes the normal approach for maintaining the storm sewer system. This is a very expensive method of dealing with maintenance as it relies on waiting for a problem to become as severe as it can be before it is repaired. Many of our larger drainage projects have been in response to increased runoff volumes: West - Central Lotus Lake, Flamingo Drive, Mandan Circle, Harrison Hill and Foxford Road are all projects which typify this. POTENTIAL CHANGES The most noticeable change will be to Chapter 19, Articles V and VII. These are the design standards for storm water treatment. This is also Appendix D of our Surface Water Management Plan. Specifically we will look at the following items: 1. Abstraction requirement. The NPDES MS4 draft, NPDES Construction, Minnehaha Creek Watershed District, and Carver County Watershed Management Organization all require some degree of abstraction. Abstraction ranges from interception by tree canopies to capture and reuse to infiltration into the ground. The least is one -half inch and the greatest is one inch from new impervious surfaces. 2. Exceptions and Limitations. The MPCA and the USEPA have set parameters under which infiltration is an acceptable practice. In instances where the soils are very poorly drained ( "D" hydrologic group and some "C ".); where the depth to bedrock or the water table is 3 feet or less; in sensitive Drinking Water Safety Management Areas (DWSMA); and in several other situations, you cannot infiltrate storm water. 3. Water Quality Volume Credits. MIDS, Carver County and others have developed dozens of alternative methods for achieving the required abstraction. These include, among others, Natural Area Conservation, tree planting, filtration, soil amendment, storm water harvest and reuse, pervious pavement, and other structural and non - structural best management practices (BMPs). 4. Water Quantity Fees Credit. Developers already receive a credit for water quality BMPs. With a reduction in volume should come a reduction in SWMP fees. Whether this reduction is a credit to Water Quality or Water Quantity is yet to be determined. 5. Structural BMP Design Standards. Concurrent to reviewing our water quality and water quantity design standards, staff will evaluate the facility design standards. This might include items such as pond access, pond buffers, the use of fountains, landscaping, and other facility design considerations. In addition to the changes to Chapter 19, there will also be some minor changes required by Appendix C of the Minnehaha Creek Watershed District Local Water Management Plan. This will include items such as identifying potential flooding areas, hydraulically insufficient conveyances and landlocked basins. The majority of his information is available through our model but some updating of the model may be needed. gAeng \terry \code ammendments \stormwater\memo_cc 05142012.doc Paul Oehme SWMP /Comp Plan Amendment May 14, 2012 Page 5 SCHEDULE Because the Surface Water Management Plan is one of three utility components required in our Comprehensive Plan, any amendment to the S WMP will also be an amendment to the Comprehensive Plan and will be subject to those rules. It is the intention of staff to have all amendments completed and approved by October 22, 2012. In order to accomplish this, staff is recommending the following schedule: DATE ACTION August 1, 2012 Agency distribution of draft amendments October 2, 2012 Public hearing held at planning commission RECOMMENDATION This was intended to be informational in nature and does not require an action at this time. It is staff's intention to come before Council at least once more prior to the July 23 distribution with a draft form. If there are items that Council would like further clarification on, please advise staff at this time. The changes to City Code will primarily be to Chapter 19. However, parts of Chapters 18 and 20 will need to be amended as well. For instance, Section 20 -960 references the City's 1994 Surface Water Management Plan when it states; "All development shall comply with the City's Surface Water Management Plan dated February 1994..." g:\eng \terry \code ammendments \stormwater\memo cc_05142012.doc