The Christmas Lake subwatershed is located along the southern boundary of the MCWD and within the cities of Chanhassen and Shorewood (see Figure 1).  The subwatershed is 742 acres in size (1.2 square miles).

The Department of Natural Resources’ Public Waters Inventory identifies four basins within the Christmas Lake subwatershed as under the jurisdiction of the DNR (see Figure 10).  These include Christmas Lake, Como Lake and two unnamed wetlands. 

Table 2.  Public Waters in the Christmas Lake subwatershed.

Source: Minnesota DNR.  See Figure 10.

The HHPLS included detailed modeling of the current and 2020 hydraulic and hydrologic conditions in the subwatershed.  That modeling includes the following results for modeled locations (lakes, ponds, channels, and crossings) within the subwatershed:

• Existing Normal Water Level;
• Existing High Water Level, peak discharge, and peak velocity for the 1.5 year, 24-hour and 100-year, 24-hour events;
• 2020 predicted HWL, peak discharge, and peak velocity for the 100-year, 24-hour event; and the
• Existing High Water Level for the 100-year, 10-day snowmelt event.

Those detailed results are not reproduced here, but are incorporated by reference.  The HHPLS model predicted no significant increase in high water levels or peak discharges between current conditions and expected 2020 conditions.  However, some landlocked subwatershed units are present, as well as numerous pocket wetlands that local plans indicate may in the future be connected or drained. 

Table 3.  Modeled peak discharge from the Christmas Lake subwatershed (cfs).

Source:  2003 MCWD Hydrologic, Hydraulic, and Pollutant Loading Study (HHPLS)

1. Christmas Lake since 1998 has consistently been scored in the A grade range on the District’s annual lake report cards and very nearly meets its total phosphorus concentration goal of 15 μg/L. 
2. As indicated below, there is a very slow trend of increasing phosphorus and declining water quality in Christmas Lake.



Source: MCWD.

3. Development, redevelopment, and reconstruction in the subwatershed is predicted to increase nutrient and TSS loads from the watershed as well as increased volume of stormwater runoff, potentially degrading water quality in Christmas Lake and streams and wetlands in the subwatershed.
4. The HHPLS identified sediment accumulation and transport in the small channel that discharges into the south end of the lake.  This should be evaluated to determine the source of the sediment, whether it is a source of phosphorus and sediment in the lake, and what erosion control measures or other improvements should be implemented.
5. Steep slopes on the east shore of the lake are erosion prone.  The HHPLS identified several known locations; the District should prepare an inventory to determine where shoreline and slope stabilization should be performed to protect water quality.

1. Several landlocked subwatershed units and individual subbasins are present in the subwatershed.  As identified in the HHPLS, the cities of Chanhassen and Shorewood have contemplated in their Local Water Management Plans connecting and/or draining these basins, altering local hydrology and potentially creating downstream volume impacts.  Within these landlocked basins, any future development or redevelopment should minimize creation of new stormwater volumes.  Outletting will generally be discouraged unless there is a demonstrated threat to property structures or public safety.
2. Development, redevelopment, and reconstruction in the subwatershed is predicted to increase volume of stormwater runoff from the watershed as well as increased nutrient and TSS loads.
3. Stormwater velocity has caused erosion in the channel that conveys drainage from the southern subwatershed unit to the lake.  

1. As described in Section 2.5.4, the subwatershed includes four Preserve classification wetlands that provide high to exceptional vegetation, wildlife, fish habitat and aesthetic values that should be protected.
2. Wetlands with moderate restoration potential in the southern portion of the subwatershed should be evaluated for improvement as opportunities arise.

1. Few opportunities are available to conserve minimally disturbed landscapes, but there are potential restoration opportunities, including wetland restorations to improve and increase habitat; native vegetation restoration along the upper watershed channel corridor for streambank stability, erosion control, and habitat connectivity; and urban forest restoration to increase evapotranspiration and reduce runoff.
2. Wetlands with high ecological values are present and should be conserved and connected to provide wildlife corridors.
3. Christmas Lake is managed as a warm water-cool water lake and stocked with rainbow trout.  It may be sensitive to thermal impacts, or changes in groundwater flow.  Future development or redevelopment should take into account potential thermal impacts to the lake’s biota from direct runoff of stormwater, or from modifications to groundwater inputs.
4. Detailed information is available on aquatic vegetation in Christmas Lake, but no management plan is in place.  Some Eurasian watermilfoil is present.

1. Groundwater input is likely an important component of the Christmas Lake water budget, and changes in water quality over the past decades may be due in part to changes in that input.  A more detailed model and analysis of Christmas Lake is necessary to better understand how both surface and groundwater inputs affect lake levels and water quality and to develop strategies for protecting this resource.
2. The FAW concluded that the wetlands in the southern part of the subwatershed were discharge or combination discharge/recharge. Increased infiltration in the southern subwatershed may be helpful in preserving that hydrology.
3. As shown on Figure 17, there is a large moderate to high aquifer sensitivity area in the northern watershed where any stormwater should be pretreated prior to discharge to an infiltration basin.  Other areas of aquifer sensitivity are associated with wetlands.
4. Stormwater management should be coordinated with wellhead protection plans.

Land use change impacts downstream water quality by increasing the volume of runoff and the concentration and load of nutrients and sediment transported to receiving waters.  Table 9 illustrates how land use change such as the expected conversion of vacant land to low-density residential could be expected to ultimately impact water quality in Christmas Lake.  The table also illustrates the impact of a regulatory program managing these impacts.

Ultimate development in this case is defined as the conversion of all agricultural lands and one-half of the upland forested area that remains undeveloped in the 2020 land use plans.  This conversion may take place by 2030 or require significantly more time; but it is assumed that at some point in the future these conversions will occur.  More detail regarding this modeling can be found in Technical Appendix A.  Because the majority of the watershed is fully developed, there is little/no change in modeling results among the analyzed time period.

Table 9 contrasts three nutrient loading reduction scenarios.  Scenarios 1 and 2 contrast the expected results if there were no regulatory program to the results under the existing regulatory program.  The HHPLS assumed that there would be no load increase from future development; the third scenario in Table 9 indicates that even with a regulatory program that strictly prohibits any new phosphorus loading, additional reductions would be necessary to achieve the desired phosphorus concentration goal of 15μg/L.

Table 9.  Christmas Lake modeled 2020 and ultimate development water quality and the total phosphorus loading reduction necessary to achieve in-lake total phosphorus concentration goals.

MCWD Goal 1 - Abstraction/Filtration

Promote abstraction of surface water where feasible for the purposes of improving water quality and increasing groundwater recharge throughout the watershed.

Discussion

Land development and the associated creation of new impervious surface increases the volume of stormwater runoff.  The new runoff volume can convey more pollutants to receiving waters and may increase erosion and sediment transport, negatively affecting water quality.  Development also decreases the amount of stormwater that naturally percolates into the soil to recharge groundwater, thus reducing baseflow in streams, changing hydrology in groundwater-fed wetlands, and decreasing water availability in drinking water aquifers.  Most of the Christmas Lake subwatershed is developed, and those hydrologic impacts have already occurred.

Abstraction of stormwater (retained on site through infiltration, evapotranspiration, or capture and reuse) reduces the amount of runoff from the site conveying pollutants. The most common type of abstraction, infiltration, reduces runoff, which helps recharge groundwater.  Filtration offers an opportunity to use soil to naturally cleanse stormwater prior to discharge.  Increased abstraction and filtration in the Christmas Lake subwatershed is desirable for three primary reasons: 1) to recharge groundwater inputs and reduce pollutant loading into Christmas Lake; 2) to help prevent localized flooding in landlocked basins with no natural outlet; and 3) to protect the hydrology of discharge (groundwater-fed) wetlands in the subwatershed.  Many of those wetlands have high ecological values and are dependant on groundwater to maintain those functions and values.

A key strategy to achieve this goal is the adoption of a volume management standard for new development and redevelopment that requires the abstraction of one inch of rainfall.   Much of the subwatershed has at least moderate infiltration potential.  Requiring new development and redevelopment to abstract some of the new stormwater generated and encouraging retrofitting to increase infiltration on existing sites would:

1. Minimize additional pollutant loading that would have been conveyed by that stormwater.  The phosphorus load reduction plan for Christmas Lake assumes that permitted new development and redevelopment will achieve a much higher rate of phosphorus load removal than can be achieved through traditional stormwater management such as detention ponds.  Abstraction and infiltration are important tools in achieving the load reductions necessary to maintain the excellent water quality in Christmas Lake, and to prevent further degradation of the other water resources in the subwatershed;
2. Reduce runoff volumes and help reduce future downstream erosion in streams and channels or flooding in landlocked basins; and
3. Help maintain groundwater levels, preserving wetland hydrology and stream baseflows. 

Because the Christmas Lake subwatershed is almost entirely developed, there will be few new opportunities to implement abstraction.  The primary strategies will be providing for infiltration on infill development and redevelopment, and encouraging retrofits on existing development.

Desired Outcomes:  Increased infiltration, reduction in pollutant loading and volumes of runoff to supplement other goals.

Metrics: Acre-feet of infiltration to meet nutrient loading reductions for water quality and volume reductions for water quantity goals.

Goal 1.1 - Christmas Lake

Increase abstraction and infiltration to reduce runoff volumes carrying pollutant loads to Christmas Lake, minimize potential flooding in landlocked basins, and to promote groundwater recharge.

Actions

1. In consultation with LGUs through an appropriate rulemaking process, amend existing or establish new District rules to increase stormwater requirements through consideration of abstraction of the first one inch of rainfall on new permitted development and redevelopment.
2. Develop infiltration strategies appropriate to wellhead protection areas (if designated in the subwatershed in the future) and areas of groundwater sensitivity.
3. Provide technical assistance to LGUs and developers to foster low impact development and redevelopment that minimizes new impervious surface and provides for increased infiltration.
   1. Develop and distribute model ordinances and design standards that incorporate low impact design principles.
   2. Sponsor educational opportunities for LGU staff, developers, elected and appointed officials and other interested parties to provide practical information and opportunities for sharing experiences.
   3. Provide education and training opportunities, technical and planning assistance for property owners and LGUs on methods to reduce runoff from and increase infiltration on their property by incorporating BMPs into landscaping, infrastructure maintenance, and reconstruction.
   4. Develop a small grant program to provide financial assistance to property owners desiring to retrofit their property with BMPs to increase infiltration.
   5. Encourage the use of infiltration as a Best Management Practice within landlocked basins of the subwatershed. 

MCWD Goal 2 - Ecological Integrity 

Promote activities that maintain, support and enhance floral, faunal quantity and ecological integrity of upland and aquatic resources throughout the watershed.

Discussion

Christmas Lake is the primary ecological resource in the subwatershed.  The Christmas Lake subwatershed also includes a number of wetlands with exceptional or high fish or wildlife habitat value as well as wetlands with exceptional or high vegetative diversity.  The Key Conservation Areas identified in Figure 19 of this plan include those wetlands as well as associated upland areas of high ecological value such as maple-basswood forest.  Within these conservation areas, wherever possible, the District would promote the conservation or establishment of native vegetation to increase or maintain infiltration rates; decrease or maintain runoff rates and pollutant conveyance to water resources; and minimize erosion of shorelines and streambanks.  Conservation of those associated upland areas not only provides additional habitat type, but also helps preserve local runoff and infiltration rates and surface water quality.   Sustaining or improving water quality and ecological integrity is necessary to meet the District goals in this plan as well as to meet state and federal nondegradation, water quality and biological integrity requirements and to prevent the need for future TMDLs.

Christmas Lake is home to a sport fishery.  There is some information on aquatic vegetation communities in the lake.  The primary strategies for sustaining or improving aquatic communities are the acquisition of new data such as shoreline vegetation surveys and management plans, and maintenance of water quality.  There are several wetlands in the subwatershed with exceptional or high vegetative diversity.  These would be inspected at least annually for invasive vegetative species.

Desired Outcomes: Functional and healthy ecological corridors and waters throughout the subwatershed.

Metrics:

• Acres of land conserved in Key Conservation Areas
• Acres of restored/created wetland within Key Conservation Areas

Goal 2.1 - Christmas Lake 

Maintain and improve overall ecological integrity within the subwatershed.

Actions

A.  Protect existing fish and wildlife habitat and promote the restoration of habitat areas and corridors by the conservation and restoration of key ecological areas (see Figure 19).

1. Require LGUs to recognize Key Conservation Areas in their natural resources and land use planning and to identify in their Local Water Management plans how they intend to conserve their ecological values.
2. Restore areas of degradation within key conservation areas.
3. Provide education and training opportunities, technical and planning assistance, and financial incentives to LGUs to actively conserve key ecological areas.
4. Work cooperatively with other agencies and organizations to improve upon existing conservation corridors and where practical, develop new conservation corridors to improve ecological integrity.

B.  Provide regulatory incentives for the preservation of undisturbed native vegetation as sites develop.

C.  Require MCWD review of and comment on preliminary plats and vegetation surveys.

Goal 2.2 - Christmas Lake

Maintain conditions suitable for a healthy and varied sport fish community within Christmas Lake.

Actions

1. Work cooperatively with the DNR in Christmas Lake fishery management efforts, and request that fish surveys be conducted regularly.
2. Maintain Christmas Lake water quality and clarity to maintain or improve habitat conditions.
3. Manage aquatic vegetation in accordance with a vegetation management plan that takes into account fishery habitat requirements.

Goal 2.3 - Christmas Lake

Maintain a healthy aquatic vegetation community. 

Goal 3 - Water Quality

Preserve, maintain and improve aesthetic, physical, chemical and biological composition of surface waters and groundwater within the District.

Discussion

The HHPLS used an extensive public input process to establish water quality goals for the primary receiving waters in the District, focusing primarily on identifying target total phosphorus concentrations.  This plan identifies those plus additional goals related to water quality.  This plan sets forth a set of actions the District will undertake to reduce pollutant loading in the subwatershed and achieve and maintain water quality goals.  The achievement of these water quality goals is not only necessary to meet state and federal water quality requirements and to prevent future TMDLs, but also to meet this plan’s ecological integrity goals. 

Desired Outcomes: Achievement of in-lake nutrient concentration goals through achievement of nutrient loading reductions.

Metrics:

• In-lake nutrient concentrations/Trophic State Index Scores (TSI) for Christmas Lake
• Nutrient loading goals (lbs) for Christmas Lake

Goal 3.1 - Christmas Lake

Achieve and maintain an in-lake total phosphorus concentration goal of 15 μg/L in Christmas Lake.

Actions

1.  Conduct a diagnostic study to investigate and determine the likely causes of the slow decline in water quality in Christmas Lake and develop options for reversing that trend.
2. Require LGUs to reduce phosphorus loading from developed uses upstream of Christmas Lake by a minimum of 10 pounds per year within 10 years. 
   1. Provide education and training opportunities, technical and planning assistance for property owners and LGUs on methods to reduce phosphorus and sediment loading by incorporating BMPs into landscaping, infrastructure maintenance, and reconstruction.
3. Provide assistance to LGUs and developers to foster low impact development and redevelopment that minimizes new phosphorus and sediment loading.
   1. Develop and distribute model ordinances and design standards that incorporate low impact design principles.
4. Sponsor educational opportunities for LGU staff, developers, elected and appointed officials and other interested parties to provide practical information and opportunities for sharing experiences.
5. Promote the general application of BMPs across the subwatershed.
   1. Consider developing a small grant program to provide financial assistance to property owners desiring to retrofit their property with BMPs to reduce phosphorus and sediment loading.
6. Continue regular water quality monitoring in Christmas Lake to assess progress toward maintaining the in-lake phosphorus goal.

Goal 3.2 - Christmas Lake  

Achieve and maintain other state lake water quality standards including >1.4 m Secchi clarity and 14 ug/L chl-a, in Christmas Lake.

Actions

1. Achieve and maintain in-lake total phosphorus goals.
2. Manage aquatic vegetation in accordance with a vegetation management plan that takes into account water clarity goals.
3. Develop a water quality index which encompasses the District’s broader definition of water quality.

Goal 3.3 - Christmas Lake  

Minimize pollutant loading contribution to St Albans Bay from Christmas Lake.

Actions

1. Maintain Christmas Lake in-lake total phosphorus concentration goal.
2. Inspect the channel draining the upper subwatershed at least annually to assess whether erosion is occurring.
3. Work cooperatively with the City of Chanhassen to manage flows in the channel to prevent erosion and sediment transport and stabilize streambanks as necessary.

Goal 4 - Public Health

Minimize the risks of threats to public health through the development of programs, plans and policies that improve the quality of surface and groundwater resources. 

Discussion

There are several potential threats to public health in the Christmas Lake subwatershed.  Sewage overflows from breaks or improperly functioning infrastructure could result in overflows discharged to downstream water resources.   An additional potential source of pathogens is waterfowl, which are attracted to open water with easy routes from the water to vegetation on shore.  The District’s role in minimizing the threats to public health in the subwatershed is mainly to provide targeted information to landowners and LGUs.

Desired Outcomes:  Minimization of threats to public health from contact with contaminated surface waters.

Metrics:  Reported cases of illness transmission via surface water contact.

Goal 4.1 - Christmas Lake 

Minimize risks to human health and water quality from land use activities.

Actions

1. Maintain Christmas Lake in-lake total phosphorus concentration goal.
2. Inspect the channel draining the upper subwatershed at least annually to assess whether erosion is occurring.
3. Work cooperatively with the City of Chanhassen to manage flows in the channel to prevent erosion and sediment transport and stabilize streambanks as necessary.

Goal 4.2 - Christmas Lake 

Maintain a vegetated shoreline on Christmas Lake where practical and effective to reduce overpopulation of the lake with waterfowl.

Actions

1. Conduct a shoreline vegetation survey to identify current shoreline status and to identify locations where restoration may be desirable and feasible.
2. Promote native vegetation over structural shoreline stabilization where practical and effective in District policies, regulations, and programs.
3. Work cooperatively with LGUs and property owners to restore native shoreline vegetation where appropriate.
   1. Provide education and training opportunities, technical and planning assistance, and demonstration project funding to LGUs to assist them in restoring shorelines and buffers on public property such as parks and open spaces, taking into consideration the balance between recreational use and ecosystem needs.
   2. Develop and distribute written material to shoreline property owners explaining the benefits of shoreline restoration and buffer creation to waterfowl control and providing design, plant selection, installation, and maintenance advice.

Goal 4.3 - Christmas Lake  

Require LGUs and other agencies to manage public sanitary sewer infrastructure to minimize sewage overflows and to minimize impacts from those overflows on District water resources.

Goal 5 - Water Quantity

Maintain or reduce existing flows from drainage within the watershed to decrease the negative effects of stormwater runoff and bounce from existing and proposed development as well as provide low flow augmentation to surface waters.

Discussion 

Development and the associated creation of new impervious surface increases the volume of stormwater runoff from the landscape, changes the rates and times to peak runoff flow, and decreases the amount of stormwater that naturally percolates into the soil to recharge groundwater.  The District’s long term goal in the Christmas Lake subwatershed is to achieve no increase in the volume of stormwater discharged from the subwatershed into St. Albans Bay. Implementation strategies will include minimizing new runoff volumes from development, encouraging infiltration and groundwater recharge to maintain adequate hydrology to groundwater-fed wetlands and to Christmas Lake itself, and limiting new volumes in landlocked subwatersheds.

A key strategy to achieve this goal is the adoption of a volume management standard for new development and redevelopment that requires the abstraction (removal from runoff through infiltration, capture and reuse, evapotranspiration, etc.) of one inch of rainfall.  Approximately 70 percent of annual runoff volume in Minnesota results from precipitation events of 1” or less (MPCA, 2000).  Requiring new development and redevelopment to abstract (retain on site through infiltration, evapotranspiration, or capture and reuse) runoff from small events would significantly reduce new volumes of runoff flowing downstream and help reduce future erosion in streams and channels; minimize new pollutant loading that would have been conveyed by that stormwater; and help maintain groundwater levels, preserving wetlands. 

Limiting discharges from subwatersheds and basins that are currently landlocked is necessary to prevent further degradation of downstream water quality as well as to limit new volumes discharged downstream to channels that are already experiencing erosion.  Encouraging infiltration in landlocked basins is one means of controlling runoff volumes to help prevent localized flooding.

Table10.  Modeled annual volume of runoff in the Christmas Lake subwatershed, and estimated reductions resulting from application of a proposed 1” abstraction rule for new development and redevelopment (acre-feet).

Some land-locked basins and pockets are identified in local water management plans for possible new outlets.  These should be maintained as is to prevent additional discharge downstream to Christmas Lake.

Desired Outcomes: Management of new annual water volume discharged from the subwatershed.

Metrics:  Acre-feet volume abstraction.

Goal 5.1 - Christmas Lake 

Reduce volume of stormwater runoff from new development and redevelopment and maintain existing water volumes discharged from the subwatershed into St. Albans Bay.

Actions

1. Amend existing or establish new District rules requiring abstraction of the first one inch of rainfall on new permitted development and redevelopment.
2. Track volumes abstracted and new volumes created resulting from permitted development.
3.  Provide assistance to LGUs and developers to foster low impact development and redevelopment that minimizes new stormwater volumes.
   1. Develop and distribute model ordinances and design standards that incorporate low impact design principles.
   2. Sponsor educational opportunities for LGU staff, developers, elected and appointed officials and other interested parties to provide practical information and opportunities for sharing experiences.
4. Encourage the development and maintenance of depressional storage within the subwatershed.

Goal 5.2 - Christmas Lake  

Manage water volumes to the upper watershed channel to prevent further erosion.

Actions

1. Inspect the channel at least annually to assess its condition.
2. Work cooperatively with the City of Chanhassen to reduce volumes as necessary. 

Goal 5.3 - Christmas Lake 

Limit new discharges from land locked basins and subbasins to prevent new impacts to Christmas Lake.

Actions

1. Require the Cities of Shorewood and Chanhassen to continue to manage CL-3 and CL-4 and pocket subbasins as landlocked basins to limit new discharges to Christmas Lake (see Figure 2 for landlocked basin locations.)

Goal 5.4 - Christmas Lake  

Require public stormwater conveyance and control structures in the watershed be sized and maintained properly to convey current and ultimate stormwater flows to minimize flooding and erosion potential.

Actions

1. Require LGUs to provide to the District a copy of their annual NPDES report.

Goal 6 - Shorelines and Streambanks

Preserve the natural appearance of shoreline areas and minimize degradation of surface water quality which can result from dredging operations.

Discussion

Eroding shorelines and streambanks contribute to the degradation of water quality.  Native vegetation can effectively stabilize these areas, filter runoff for sediment and other pollutants, and provide habitat.  Restoration of shoreline and streambanks on Christmas Lake, especially the steep slopes on the eastern shore; the channel draining the upper subwatershed; and wetlands within the subwatershed is a key strategy for meeting this plan’s goals.

Conservation or restoration of native vegetation along shoreline and streambank would provide habitat for both aquatic and terrestrial wildlife; help increase or maintain infiltration rates; decrease or maintain runoff rates and pollutant conveyance to water resources; and help minimize erosion.     Sustaining or improving water quality and ecological integrity is necessary to meet District goals as well as to meet state and federal nondegradation, water quality and biological integrity requirements and to prevent the need for future TMDLs. 

Desired Outcomes: Stable streambanks and shorelines to supplement other goals.

Metrics:  Linear feet of stabilized eroded shoreline and streambank.

Goal 6.1 - Christmas Lake

Promote shoreline restoration and shoreline buffer creation as methods to help meet pollutant loading reduction and ecological integrity goals.

Actions

1. Conduct a Christmas Lake shoreline vegetation survey to identify current shoreline status and to identify locations where restoration may be desirable and feasible.
2. Work cooperatively with the City of Chanhassen to identify and complete potential restoration opportunities along the channel that drains the upper subwatershed.
3. Promote native vegetation over structural shoreline stabilization in District policies, regulations, and programs.
   1. Provide education and training opportunities, technical and planning assistance, and demonstration project funding to LGUs to assist them in restoring shorelines and buffers on public property such as parks and open spaces.
   2. Develop and distribute written material to shoreline property owners explaining the benefits of shoreline restoration and buffer creation to the reduction of pollutant loads and creation of shoreline habitat and providing design, plant selection, installation, and maintenance advice.
   3. Develop a small grant program to provide financial assistance to property owners desiring to restore their shoreline or plant a buffer.

Goal 7 - Navigation

Maintain the hydraulic capacity of and minimize obstruction to navigation without compromising wildlife habitat in watercourses and preserve water quality and navigation appearance in shoreland areas.

Discussion 

The District recognizes the riparian rights of property owners to have and maintain access to public waters.  The District will not participate in the removal of nuisance aquatic vegetation solely for the purpose of improving navigation, but may consider macrophyte control where excessive growth contributes to poor water quality.

Desired Outcomes:   Minimization of impacts on water resources from dredging.

 Metrics:  Compliance with the dredging policy. 

Goal 7.1 - Christmas Lake 

Manage dredging activities so as to preserve the natural appearance of shoreline areas; recreational, wildlife and fisheries resources of surface waters; surface water quality and ecological integrity of the riparian environment. 

 Actions

1. Regulate dredging activities in a manner consistent with local policy and Minnesota Rules Chapter 6115.0200

Goal 8 - Best Management Practices

Improve water quality by promoting best management practices (BMP's), requiring their adoption in local plans and their implementation on development sites.

Discussion

This plan and District regulations stipulate the use of Best Management Practices (BMPs) to reduce stormwater volumes and pollutant loadings, but do not prescribe which practices should be used.  This allows the LGU and developers the flexibility to implement those that are most appropriate for local conditions and opportunities.  A key strategy for plan implementation is providing early consultation with and technical assistance to and education of stakeholders including city staff, residents, and developers to increase knowledge and acceptance of various BMPs and to promote their adoption.  

Desired Outcomes: Implementation of Best Management Practices on private and public property to supplement other goals.

Metrics: Compliance with the early consultation requirement.

Goal 8.1 - Christmas Lake

Promote best management practices as methods to help meet pollutant loading and volume management goals established in this subwatershed plan.

Actions

1. Require LGUs to identify in their local water management plans how they plan to meet specific phosphorus loading minimum reduction goals from developed and agricultural uses through the implementation of BMPs in the subwatershed. 
   1. Provide education and training opportunities, technical and planning assistance for LGUs on methods to reduce phosphorus and sediment loading by incorporating BMPs into landscaping, infrastructure maintenance, and reconstruction
2. To promote BMPs and encourage early consultation by developers, amend District rules to incorporate a requirement for stormwater management plan approval prior to submittal of a preliminary plat.
3. Develop and distribute model ordinances and design standards that illustrate the proper application of various BMPs.

Goal 9 - Education and Communications

Enhance public participation and knowledge regarding District activities and provide informational and educational material to municipalities, community groups, businesses, schools, developers, contractors and individuals. 

Discussion

The District conducts an active strategic education and communication program watershed-wide to provide general information to various stakeholder groups in accordance with its five-year strategic education and outreach plan.  Targeted information will be necessary in the Christmas Lake subwatershed to educate these stakeholders as to the District’s specific goals for this subwatershed, the actions the District plans to take, and their role in conserving water resources in the subwatershed.  The specific targeted messages will emphasize shoreline stabilization on Christmas Lake and volume control in landlocked drainage areas.

Desired Outcomes: Stewardship over water resources by residents of the subwatershed to assist District activities and supplement other goals.

Metrics:  Telephone survey.

Goal 9.1 - Christmas Lake

Provide focused education and outreach opportunities within this subwatershed to supplement the general education and outreach program and assist in the achievement of these subwatershed goals.

Actions

1. Develop and distribute targeted written material to stakeholder groups (e.g., residents, shoreline property owners, developers) explaining the need for shoreline stabilization and stormwater volume management and providing strategies that each stakeholder group can employ to assist in meeting these goals.
2. Sponsor educational events such as for LGU staff, developers, elected and appointed officials, shoreline property owners, and other interested parties to provide practical information and opportunities for sharing experiences.
3. Prepare and distribute timely news releases to coincide with education efforts to inform the public of BMPs and other District actions that affect them directly.

Goal 9.2 - Christmas Lake

Provide participation and outreach activities to increase awareness of water and other natural resources within the subwatershed.

Actions

1. Work cooperatively with the Christmas Lake Association.
2. Recruit and train volunteers to monitor aquatic vegetation in Christmas Lake on an ongoing basis.

Goal 9.3 - Christmas Lake

Work cooperatively with other agencies and groups to coordinate education and outreach efforts to avoid duplication of efforts and maximize resources.

Goal 10 - Public Ditches

Maintain public ditch systems within the District as required under Statutory jurisdiction. 

There are no Public Ditch goals and actions specific to the Christmas Lake subwatershed.

Goal 11 - Wetlands

Preserve, create and restore wetland resources and maximize the benefits and functionality of wetlands to the watershed.

Discussion

The Functional Assessment of Wetlands (FAW) evaluated and classified 58 acres of wetlands in the subwatershed, of which 33 acres were in the Preserve classification (see Table 8 in Section 2.5.4 and Figure 12).  There are several wetlands of exceptional and high quality functions and values within this subwatershed.  Their conservation is integral to achieving ecological integrity goals, as well as water quality, stormwater management, and floodplain management goals.  There are also opportunities for wetland restoration.

A key strategy of this plan is regulation of wetland impacts in accordance with a management classification based on the functions and values findings of the Functional Assessment of Wetlands.  Wetlands are assigned to a classification – either Preserve or Manage 1, 2, or 3 – and allowable impacts would be based on that classification.  The wetlands with the highest values – those in the Preserve classification – would be allowed minimal impacts.  The Manage classifications would be allowed some impacts, such as accepting new stormwater discharges, depending on classification.   This strategy will preserve existing high values such as habitat, vegetative diversity, and sensitivity, while also recognizing that wetlands play an important part in managing stormwater.  Wetlands provide essential storm and flood water storage.

Wetlands of exceptional or high vegetative diversity or fish or wildlife habitat value have been designated key conservation areas (see Figure 19), as have wetlands that are riparian to streams or channels, have high restoration potential, provide key floodplain storage, or are located in important natural resources conservation areas such as wildlife corridors.  Except for those in the Preserve classification, which will be managed to an even higher standard, these conservation wetlands will be managed as if they were Manage 1 classification wetlands, with limitations on the amount of new runoff that can be directed to them, and a requirement to pretreat any new discharges to them.

An important part of achieving the goal of no net loss of wetland size, quality, and type will be tracking wetland impacts to assist in identifying future restoration or wetland creation needs.

Equally important to the regulation of wetlands is the restoration of degraded wetlands within the subwatershed.  Figure 14 identifies wetlands based on restoration potential.  Restoring wetlands increases specific functions and values of the resource within the watershed ranging from management of flows to water quality improvement to enhancement of the overall ecosystem, particularly within identified corridors.

Desired Outcomes:  Maintain existing quantity and quality of wetlands throughout subwatershed; improve wetland and surface water quality within Key Conservation Areas.

Metrics:

• Wetland quantity (acres)
• Wetland quality (acres/management classification)
• Acres of restored/created wetland within Key Conservation Areas

Goal 11.1 - Christmas Lake

Maintain existing acreage of wetlands in the subwatershed and achieve no net loss in their size, quality, type, and biological diversity.

Actions

1. Regulate wetland impacts commensurate with the quality of the wetland as determined by the Management Classifications identified in the Functional Assessment of Wetlands (FAW).
2. In consultation with LGUs through an appropriate rulemaking process, amend existing or establish new District rules requiring mitigation of all fill in Preserve category wetlands; and specifying by management classification stormwater discharge pretreatment, buffer, hydroperiod, and other wetland standards.
3. Require that wetland losses in the Christmas Lake subwatershed be mitigated within the Christmas Lake subwatershed.
4. Track wetland losses resulting from permitted fill.
5. Restore degraded wetlands in Key Conservation Areas to improve vegetative diversity and ecological integrity, with priority given to wetlands where restoration could improve management classification to at least a Manage 1.  Restore other wetlands as opportunities arise.
6. Restore vegetative diversity and ecological integrity of all wetlands in which the District acquires an interest.
7. Update the Functional Assessment of Wetlands to maintain a current inventory of wetland location, size as well as function and value.

Goal 11.2 - Christmas Lake

Increase the quantity, quality, and biological diversity of Christmas Lake subwatershed watersheds through the restoration of impacted wetlands or creation of new wetlands.

Actions

1. Consider the feasibility of restoration of wetlands D-116-23-02-009 and D-116-23-02-002 (see Figure 14 for locations), in a pocket of wooded upland and wetlands west of Curry Farms Park in Chanhassen identified as being of moderate restoration potential.  Two wetlands bisected by Powers Boulevard, E-116-23-02-003 and D-116-23-02-023 are also identified as being of moderate restoration potential and provide a small pocket of wetland and woodland in a fully developed area.

Goal 12 - Groundwater

Protect and maintain existing groundwater flow, promote groundwater recharge and improve groundwater quality and aquifer protection.

Discussion

Maintenance of groundwater recharge is important in the Christmas Lake subwatershed to maintain hydrology to Christmas Lake and groundwater-fed discharge wetlands in the subwatershed as well as to recharge aquifers that supply public and private water wells.  Development, with the associated creation of new impervious surface, increases the volume of stormwater runoff and reduces the amount of stormwater that naturally percolates into the soil to recharge groundwater.

Increased infiltration in the Christmas Lake subwatershed is desirable for three primary reasons: 1) to recharge groundwater inputs and reduce pollutant loading into Christmas Lake; 2) to help prevent localized flooding in landlocked basins with no natural outlet; and 3) to protect the hydrology of discharge (groundwater-fed) wetlands in the subwatershed.   Some of those wetlands are key resources with high ecological values that are dependant on groundwater to maintain those functions and values.  Much of the subwatershed has at least moderate infiltration potential.  Requiring new development and redevelopment to infiltrate some of the new stormwater generated would reduce new volumes downstream and help reduce future erosion in streams and channels; minimize new pollutant loading that would have been conveyed by that stormwater; and help maintain groundwater levels, preserving wetlands. 

Some parts of the subwatershed are areas of aquifer sensitivity or may be designated in the future as drinking water wellhead protection areas, where care should be taken when infiltrating stormwater.  Proper design of infiltration practices is necessary to avoid groundwater contamination. 

Groundwater management in the Christmas Lake subwatershed will focus on increasing the amount of infiltration in the subwatershed, and minimizing opportunity for groundwater contamination from land use practices.

Desired Outcomes: Maintain function of existing groundwater flow, assist in the protection of drinking water supply, no degradation in surficial groundwater quantity or quality.

Metrics:

• Acre-feet volume abstraction
• Surficial groundwater levels and parameters

Goal 12.1 - Christmas Lake

 Protect and maintain groundwater recharge and groundwater quality.

Acti

1. Amend existing or establish new District rules requiring abstraction of the first one inch of rainfall on new permitted development and redevelopment.
2. Establish new District rule requiring an additional level of analysis and review of permitted development and redevelopment where there is a potential to adversely impact groundwater connected to a surface water feature.
3. Require pretreatment of stormwater discharged to wetlands or infiltration areas in the in the areas of high aquifer sensitivity.
4. Coordinate stormwater and groundwater management within identified drinking water management areas and wellhead protection areas with city and private wellhead protection plans
5. Develop infiltration strategies appropriate to wellhead protection areas and areas of groundwater sensitivity.
6. Work cooperatively with Hennepin and Carver Counties, the Minnesota Department of Health, and other agencies charged with managing private and public groundwater wells to assess the potential impacts of surface water management practices on groundwater quality.
7. Provide assistance to LGUs and developers to foster low impact development and redevelopment that minimizes new impervious surface and provides for increased infiltration.
   1. Develop and distribute model ordinances and design standards that incorporate low impact design principles.
   2. Sponsor educational opportunities for LGU staff, developers, elected and appointed officials and other interested parties to provide practical information and opportunities for sharing experiences.
8. Identify a network of surficial aquifer monitoring wells across the entire Minnehaha Creek watershed, monitor groundwater levels and groundwater quality, and if change is detected identify strategies for addressing that change.

Goal 13 - Floodplains

Reduce the severity and frequency of flooding and high water by preserving and increasing the existing water storage capacity below 100-year flood elevations on all waterbodies within MCWD.

Discussion

Flood Insurance Studies have identified no floodplain in the Christmas Lake subwatershed.  However, managing stormwater flows within this subwatershed is still important to help reduce the severity and frequency of localized flooding within the subwatershed.  The primary strategy in the management of stormwater in the Christmas Lake subwatershed is the preservation of the existing stormwater storage provided by wetlands.  Additional storage could be provided through the creation of depressional storage areas on new developments.

Desired Outcomes: No net loss of wetland storage.

Metrics:  Acres net wetland fill. 

Goal 13.1 - Christmas Lake

Preserve the existing water storage capacity.

Actions

1. Minimize loss of the large wetland complexes that provide substantial upstream stormwater storage within this subwatershed.
2. Encourage the development and maintenance of depressional storage within the subwatershed.

1.  Promote the acceptability of minor flooding within the low lying areas.

Goal 13.2 - Christmas Lake

Utilize District hydrologic and hydraulic data to identify potential public infrastructure high water impacts.

1. The HHPLS noted that the natural swale outletting the unnamed wetland, DNR ID 27-892W (see Figure 10 for location), in subwatershed unit CL-2 is predicted to just overtop during the 100-year snowmelt event, which may impact Christmas Lake Road.   Local plans should identify these observed or potential locations and assess whether the risk of occasional flooding is acceptable or should be addressed.  Assist LGUs in determining specific impacts and potential improvements.

Goal 14 - Recreation

Promote the recreational use, where appropriate, of surface waters within MCWD by providing recreation opportunities for citizens by promoting the use and enjoyment of water resources with the intent of increasing the livability and quality of life within the watershed.

Discussion

Christmas Lake is an exceptional recreational water resource in this subwatershed due to its water clarity and its fishery.  The District’s primary strategies in promoting and supporting recreational use of Christmas Lake are protecting its water quality to support swimming and fishing, and managing aquatic vegetation.

Desired Outcomes: Manage surfaces waters to achieve water quality goals so designated use is maintained and unimpaired.

Metrics:

• In-lake nutrient concentrations/Trophic State Index Scores (TSI) for Christmas Lake
• Nutrient loading goals for Christmas Lake

Goal 14.1 - Christmas Lake

Support Christmas Lake recreational use by continuing to meet the State's aquatic recreation standard of 40 μg/L summer mean total phosphorus through the implementation of the programs and projects identified in this plan to reduce phosphorus loads and improve Christmas Lake water quality.

Goal 14.2 - Christmas Lake

Support the Christmas Lake fishery through the implementation of the programs and projects identified in this plan to maintain ecological integrity and promote shoreline restoration.

Goal 15 - Erosion Control

Control temporary sources of sediment resulting from land disturbance and identify, minimize and correct the effects of sedimentation from erosion-prone and sediment source areas.

Discussion

Erosion within the subwatershed can result in sediment being transported to lakes, wetlands, and streams, where it can degrade water quality and habitat.  Steep slopes such as those on the east shore of Christmas Lake are prone to erosion and can negatively impact the lake’s exceptional water quality and clarity.   The HHPLS identified the channel draining the upper subwatershed as another potential location prone to erosion.  Identifying, addressing, and preventing erosion is necessary to meet District goals as well as to meet state and federal nondegradation, water quality and biological integrity requirements and to prevent the need for future TMDLs. 

Requiring new development and redevelopment to infiltrate some of the new stormwater generated would reduce post-development volumes downstream and help reduce future erosion in streams and channels; minimize new pollutant loading that would have been conveyed by that stormwater; and help maintain groundwater levels, preserving wetlands.  Limiting discharges from subwatersheds and basins that are currently landlocked is necessary to prevent further degradation of downstream water quality as well as to limit new volumes discharged to channels that are already experiencing erosion.

Strategies in the Christmas Lake subwatershed will focus on identifying erosion problems and working with LGUs and property owners to correct them.  Identifying existing eroded shoreline locations and potential future locations for shoreline restoration is a priority, as is working cooperatively with the City of Chanhassen to evaluate restoration potential along the upper subwatershed channel. 

Desired Outcomes: Reduction in pollutant loading of temporary and permanent nature from erosion to supplement other goals.

Metrics:

• In-lake nutrient concentrations/Trophic State Index Scores (TSI) for Christmas Lake
• Nutrient loading goals (lbs) for Christmas Lake

Goal 15.1 - Christmas Lake

Identify and address erosion problems in the subwatershed.

Actions

1. Identify, inventory, and prioritize steep slope, shoreline and other erosion problems.

2. Work cooperatively with LGUs to address identified erosion problems.

3. Regulate new development and redevelopment and ensure compliance with erosion control standards.

Goal 15.2 - Christmas Lake

Manage water volumes to the channel draining the upper subwatershed to prevent further erosion.

Actions

1. Implement the regulatory and management activities identified in this plan.

2. Inspect the upper subwatershed channel periodically to assess its condition.

3. Work cooperatively with the City of Chanhassen to reduce stormwater volumes to prevent erosion and sediment transport and stabilize streambanks as necessary.

Goal 16 - Regulation

Promote effective planning to minimize the impact of development and land use change on water resources as well as achieve watershed District Goals.

Discussion

The District’s regulatory program is the means by which many of the goals enumerated here would be accomplished.  As development and redevelopment occurs, property owners and developers are required to treat and control stormwater, limit impacts to wetlands, and meet other standards.  Additional regulation may be necessary in the Christmas Lake subwatershed to implement the actions in this Plan.

Desired Outcomes: Utilize regulatory program to cost-effectively manage land use to achieve other goals.

Metrics:

• Acre-feet volume abstraction
• In-lake nutrient concentrations/Trophic State Index Scores (TSI) for Christmas Lake
• Nutrient loading goals (lbs) for Christmas Lake
• Wetland quantity (acres)

Goal 16.1 - Christmas Lake

In consultation with LGUs through an appropriate rulemaking process, amend existing or adopt new District rules to implement the actions identified here within two years of adoption of this Plan.

Actions

1. Amend District rules as set forth in this Plan within two years of adoption of this Plan.
2. Provide technical assistance to LGUs in the implementation of existing or new rules.
   1. Develop and distribute model ordinances and design standards that could be used to implement existing or new rules.
   2. Sponsor educational opportunities for LGU staff, developers, elected and appointed officials and other interested parties to provide practical information and opportunities for sharing experiences.
3. Promote “Conservation Ordinances” related to low-impact development, tree-conservation, open space conservation, etc.

Goal 17 - Public Involvement

Solicit input from the general public with the intent that policies, projects and programs will address local community values and goals as well as protect historic and cultural values regarding water resources; strive to manage expectations; base decisions on an educated public; foster an educated and informed public within the watershed. 

Discussion

The District has good working relationships with the LGUs within the watershed, and maintains a Citizens Advisory Committee to obtain regular public input on issues of concern to the District and its citizens.  As the District implements the actions identified in this Plan, including the education and communication actions described above, it will be important to obtain direct input from water resource users.  The primary strategy for the Christmas Lake subwatershed will be working cooperatively with the Christmas Lake Association.

Desired Outcomes: Engage the public to encourage involvement in District activities and stewardship of area resources.

Metrics:  Consultations with Christmas Lake Association and other interest groups.

Goal 17.1 - Christmas Lake

Work cooperatively with the Christmas Lake Association.

Actions

1. Provide information and organizational assistance.
2. Attend meetings as requested to share information, hear concerns, and maintain a good working relationship.

As discussed in Section 3.6 above, the subwatershed is mostly developed and future development is expected to contribute only a small amount of additional stormwater volume and pollutant load to Christmas Lake.  To mitigate future impacts and to address other goals such as increased infiltration, wetland management, and improved ecological integrity, additional regulation may be necessary.  A decision on rulemaking needs/standards can only be made after the formal rulemaking process.  In addition, further amendments to the Rules should not be precluded by the content of the plan.

Additional regulatory controls on permitted development and redevelopment will be considered for this subwatershed to add volume management and infiltration requirements, implement wetland management in accordance with management classification, and increase scrutiny of development that may impact groundwater or key conservation resources.  Regulations providing an incentive such as a volume reduction credit to developers to maintain undisturbed areas, reforest, or plant native vegetation will be considered.

The following are revised or additional regulatory controls in this subwatershed that would be necessary to assist the District in meeting the goals of this Plan:

1. Amend existing or establish new District rules requiring abstraction of the first one inch of rainfall on new permitted development and redevelopment.
2. Provide regulatory constraints and incentives for the conservation of undisturbed native vegetation as sites develop.
3. Amend District rules to incorporate a requirement for stormwater management plan approval prior to submittal of a preliminary plat.
4. Amend existing or establish new District rules requiring submittal of a functions and values assessment for all proposed wetland impacts requiring a permit; mitigation of all fill in Preserve category wetlands; and specifying by management classification stormwater discharge pretreatment, buffer, hydroperiod, and other wetland standards.
5. Establish new District rule requiring an additional level of analysis and review of permitted development and redevelopment where there is a potential to adversely impact groundwater connected to a surface water feature.
6. Require pretreatment of stormwater discharged to wetlands or infiltration areas in the in the areas of high aquifer sensitivity.

Key conservation areas are identified on Figure 19.  The District will provide technical assistance to the LGUs to identify and implement strategies for local conservation efforts in support of program goals.  

The District operates a watershed-wide Strategic Education and Communications program that provides general watershed information as well as targeted information.  The targeted education and public input activities identified in this plan will be implemented to assist in the maintenance of existing water quality in Christmas Lake and other water resources in the subwatershed as well as to minimize the impacts of future development.  The specific targeted messages will emphasize stabilization of eroding shorelines on Christmas Lake, and stormwater volume management in landlocked basins.

Hydrologic Data Program

To monitor progress toward meeting water quality and quantity goals, monitoring of Christmas Lake will continue to be routinely monitored through the District’s Hydrologic Data Program.

Aquatic Vegetation

Lake aquatic plant monitoring provides information needed to manage aquatic plants, evaluate control measures, and plan for future actions.   This monitoring is especially useful as water quality management activities are implemented and plant communities change in response to changing water quality.  An aquatic vegetation management plan will be developed using existing aquatic vegetation data, however, one site visit will be required to assess shoreline vegetation and identify areas of shoreline erosion.  The estimated cost of this activity is $6,000.  The survey will be updated by staff/contractor every five years at an estimated cost of $8,000.  Interim monitoring could be conducted by trained volunteers.

Wetland Monitoring

Wetlands with exceptional value vegetation are present in the subwatershed.  Because of the importance to overall subwatershed ecological integrity of preserving these values, these wetlands will be regularly monitored for invasive species by staff or trained volunteers. 

Activities detailed in this implementation plan will require new operations and maintenance activities in this subwatershed.  These include:

Table 11.  Ongoing District operations and maintenance tasks in the Christmas Lake subwatershed.

One of the water quality goals for this subwatershed is the achievement and maintenance of the Christmas Lake in-lake phosphorus concentration goal of 15 μg/L.  The primary means of achieving and maintaining that goal will be limiting new phosphorus loads from development and other sources through the regulatory program, loading reduction allocations to LGUs, and operational programs.  Table 13 below sets forth a summary plan for how this could be accomplished.

The table breaks down modeled phosphorus loading in the subwatershed by source: atmospheric deposition, external sources, and internal sources.  Atmospheric deposition is a regional issue and is not dealt with here.  The primary means of addressing external loading are through the regulation of new loads generated by development and the reduction of existing loads through the general application of BMPs.  Application of the current regulatory program to new development would also reduce the expected load from ultimate development conditions. 

Table 13.  Phosphorus load reduction plan for Christmas Lake.

There are no District capital improvement projects proposed for the Christmas Lake subwatershed for this Plan cycle.   The District may consider collaborative projects with the LGUs to restore wetlands or stabilize streambanks or shorelines.

This Plan identified the need to consider a diagnostic study of long-term water quality trends in Christmas Lake, but that study was not included in the 2007-2016 prioritized CIP.  The Board may consider such a study during the time frame of this Plan if funds are available.

The following tables summarize the proposed implementation action items and their relationship to the problems and issues identified in section 3.0 above, the metrics by which the District will be evaluating progress toward resolving hose issues and problems, the estimated District cost of implementing those actions, and anticipated implementation schedule.

Table 14.  Problems and issues identified in the Christmas lake subwatershed and actions proposed to address them.

Table 15.  Summary of metrics to be used in evaluating progress toward Christmas Lake subwatershed goals.

Table 16.  Summary of Christmas Lake subwatershed implementation Program