A new chapter, 12.20 Low Impact Development, has been added to CCMC.  Title 18 Appendix, Development Standards, Division 14 now references the Carson City Drainage Manual. The manual was approved March 18, 2021 and became effective July 1, 2021.

A few changes to note:

  1. Low Impact Development (LID) for flow and volume-based stormwater is required for all new development and redevelopment.
  2. The minimum design storm has been changed from a 5-year, 24-hour storm to a 10-year, 24-hour storm.
  3. Check out the guide of various BMPs in the drainage manual.

Check out Frequently Asked Questions below.

Low Impact Development & Drainage Manual FAQs

Low Impact Development (LID), is a land development practice that improves stormwater quality in urban areas. LID practices reduce the amount of runoff and alters stormwater by slowing, holding, infiltrating, and evaporating stormwater onsite. LID practices filter out pollutants such as oil, bacteria, sediment, and nutrients by allowing the runoff to seep through onsite vegetation and soil. Urbanized areas within the Carson River Watershed can incorporate LID practices into their stormwater management repertoire and gain many benefits that enhance overall watershed health. The benefits of LID include: (1) Reduces Flooding, (2) Improves Air and Water Quality, (3) Restores Aquatic Habitat, (4) Improves Groundwater Recharge, (5) Enhances Neighborhood Beauty, (6) Reduces Cost and Maintenance of Stormwater Infrastructure, and (7) Mitigates Urban Heat Islands.
Carson City has a wonderful, growing community that has a diverse group of residence. We have a beautiful city and we want to keep it that way. By implementing LID improvements to the drainage criteria, we can be better prepared for flooding and have safer and more robust infrastructure designed to handle a wider range of precipitation events. This will lead to a brighter future for the next generations and make an impact on all of us who work or live in Carson City. The more development that comes to Carson City the greater the importance that we create these changes. Additionally, Carson City is required to implement and enforce LID practices through its Stormwater Management Program (SWMP) to reduce the pollutants in its stormwater and discharged through its Municipal Separate Storm Sewer System (MS4).
All new projects that add or modify greater than 10,000 square feet of impervious area or causes disturbance greater than or equal to 1 acre, will be required to meet these new standards.
The drainage manual contains the same requirements previously held in Title 18, Division 14 of the Carson City Municipal Code (CCMC) with the exception of the LID and the minimum design storm requirements. While the changes may bring about new design and construction requirements, the changes provide flexibility. Developers and contractors are uniquely suited to solve our demanding environmental challenges and these new codes will guide development with goals and minimum standards but will also allow for exemptions where these features are not well suited.
Yes. Carson City is already requiring these commitments with new land development projects; these projects are well suited for these new standards as there is available space to plan for the LID and stormwater infrastructure improvements. Infill projects bring greater challenges as the property are often already burdened with mature vegetation, property restrictions, structures, and other hardscape. The City Engineer can evaluate exemptions on a case-by-case basis and may waive or reduce requirements when conditions warrant flexibility.
Carson City does not see any significant increase in maintenance or expenses related to preventative maintenance in relation to these requirements; in some instances, maintenance requirements may be reduced by implementing LID. Proper maintenance and care remain to be key components to ensuring that adequate storage volume and retention/detention characteristics are maintained.
Flooding has been a concern in our basin for decades. For those who have lived through the recent floods of 2017 and/or 1997 can attest to the damage and impacts that flooding has on our region. Designing for a larger storm means that these impacts are mitigated, to a larger extent, more frequently. While there is still the possibility that a storm event exceeds the design storm, the impacts will become less frequent and reduce the total impact. This isn’t just coming from your local government; Carson City residents have asked for greater protection from flooding. Carson City’s new regulations give volume credit for LID facilities against the detention mitigation volume and allows flexibility in LID design based on what the site can support. A recent example of LID being incorporated into the site design is the Carson City Community Center’s west parking lot. A LID infiltration system was installed to capture run-off from the new parking area. The storm water is then infiltrated into the ground along the edge of the parking spaces. Any excess flow can continue downstream to Mills Park. Carson City will continue to incorporate LID components in new projects.
Changes to CCMC can be long and arduous which require staff hours and administrative time to complete. Having a separate design manual will greatly improve the response time in which errors/omissions can be addressed. Confusing statements can be quickly re-written and posted immediately without Board approval. However, changes to the design requirements will still require community outreach and Board approval.
It is difficult to separate development and growth from the Cities’ problems. Development of impervious area is the primary reason why stormwater mitigation is needed. Carons City wishes to partner with developers to solve our community’s problems, rather than view this issue as a point of conflict. We believe that implementation of this will improve our community and make it a more desirable place to live and thus increasing demand for new development.
While Northern Nevada is currently using the 5-year design storm, it should not be discounted that flooding, stormwater impacts, and lawsuits have cost those communities millions to mitigate and plan around. By increasing our mitigation efforts, we will reduce the risk of those impacts both in the short term and long term. These changes also allow us to improve our Community Rating System (CRS) rating class which can lower flood insurance costs to all community members. These changes will also get us in alignment with federal guidelines which help us obtain FEMA grants and other federal monies.
The City already does this and will continue to do this. We want to see developers and contractors find success in moving their businesses and developments to Carson City, but we must do it responsibly. We will always be as upfront and engaged as we can to help new projects get the answers they need and guide them to successful completion.