City and County of Denver Storm Drainage Design and Technical Criteria, 2013
14.0 Water Quality
This chapter hereby incorporates by reference specified portions of Volume 3 of the DISTRICT MANUAL for purposes of design and implementation of BMPs. Furthermore, application of the criteria contained herein shall be in accordance with the guidelines stated in the Denver Water Quality Management Plan.
Denver requires the following:
1) Facilities shall be designed to be readily maintainable with clearly specified long-term maintenance requirements.
2) Long-term maintenance of structural BMPs must be provided by the facility owner.
3) The facility owner, or owner’s representative, shall submit to the city at the time it seeks plan approval an operations and maintenance plan to assure that all structural BMPs function as intended. Maintenance guidelines are provided in the Denver Water Quality Management Plan and Volume 3 of the DISTRICT MANUAL which Denver may, in its discretion, follow.
Water Quality Management Plan City and County of Denver, 2004
Chapter 6: Stormwater Quality BMP Implementation Guideline
Part 5-3: Maintenance Policies and Guidelines
In order for stormwater BMPs to be effective, proper maintenance is essential. Maintenance includes both routinely scheduled activities, as well as non-routine repairs that may be required after heavy storm events or as a result of other unforeseen problems. Arrangements for BMP maintenance are the responsibility of the entity owning the BMP. More specifically, if Denver owns the BMP, then Denver maintains the BMP. If a private party owns the BMP, then the private party is responsible for arranging for maintenance of the BMP. BMPs should be designed with maintenance as one of the key design considerations, as discussed in the BMP Fact Sheets section of this chapter. This section provides recommendations for Denver to ensure proper maintenance of BMPs, as well as specific guidelines for BMP maintenance. For BMPs currently widely used in the Denver Area, the maintenance guidelines build directly upon Volume 3 of the Urban Storm Drainage Criteria Manual. For BMPs that have been used less frequently in the Denver area, such as green roofs, recommendations for maintenance are provided based on experiences in other parts of the United States.
Defining Maintenance Responsibility for Public and Private Facilities
Defining who is responsible for maintenance of BMPs and ensuring that adequate budget is allocated for maintenance is critical to the long-term success of BMPs. In Denver, maintenance responsibility may be assigned in four different ways:
- Municipally owned BMPs are maintained by Denver, typically through the Wastewater Management Division, but occasionally by Parks and Recreation. Denver personnel responsible for maintenance are trained by Denver’s Department of Environmental Health.
- Regional drainage facilities located outside of Denver parks are maintained by UDFCD when specific criteria are met.
- Privately owned BMP are maintained by the property owner, Homeowner’s Association or property manager.
- Privately owned BMPs are maintained by Denver under a written agreement with the owner, with appropriate fees assessed for maintenance services.
Enforcement of BMP maintenance is required under Denver’s Colorado Discharge Permit System (CDPS) stormwater permit and is accomplished through several full-time staff that conduct inspections of permanent BMPs. Additional legal enforcement may be accomplished by a variety of other mechanisms including:
- Agreements establishing legally binding BMP maintenance requirements and responsibilities.
- Permit obligations specifying BMP requirements.
- Municipal legislative action or rulemaking authority.
Examples of maintenance agreements from several communities throughout the country can be found in Appendix D. Examples of some of the specific requirements suggested for legal agreements by the Watershed Management Institute (1997) include:
General Assurances: Identify requirements for proper operation and maintenance, conditions for modification of facilities, dedicated easements, binding covenants, operation and maintenance plans, and inspection requirements.
Warranty Period: Require the original developer to be responsible for maintenance and operation during a defined short-term period and identify the entity responsible for long-term operation. The party responsible for long-term maintenance must have appropriate legal authority to own, operate, maintain, and raise funds to complete needed maintenance.
Proof of Legal Authority: Require that the entity meet certain conditions verifying its legal authority to ensure maintenance.
Conditions for Phased Projects: Clearly specify how maintenance responsibilities are allocated over the long-term for a project that is phased in over time.
Remedies: Clearly define remedies in the event that inspections determine that the facilitiy is not being properly maintained.
For private facilities, such as those owned and maintained by homeowners associations, there is often a lack of understanding of maintenance required for BMPs. Both Denvers internal staff and outside reviewers of this plan identified maintenance of private facilities as a top priority. One proposed solution was to require a maintenance plan to be submitted as part of the development review/approval process. Recommendations for such maintenance plans are provided below. In addition to maintenance plans, another important step is educating the general public on the purpose and function of stormwater BMPs. This is critical in cases where Low Impact Development (LID) or landscape-based BMPs are implemented on multiple parcels in developments. In addition to legally binding maintenance agreements, it would also be helpful to have easy-to-understand informational brochures that describe the functions and maintenance requirements for these facilities are also provided, in the event that they are approved on a limited basis under site-specific circumstances. BMP maintenance requirements should be posted on the Denver Public Works website for ready access by the public and be incorporated into updates to Denver’s Storm Drainage Design and Technical Criteria Manual. Since some of the BMPs included in this plan are relatively new to Denver, practical experience will likely provide more insight into maintenance needs. As a result, the Denver (www.denvergov.org) and UDFCD (www.udfcd.org) websites should be periodically checked for updates to maintenance recommendations. It is also important to note that the guidelines included in this plan should always be combined with common sense and good judgment based on field observations and practical experiences of staff.
On a general note with regard to BMPs that have a vegetation component or involve weed and pest control, the Mayors Executive Order 121 establishes specific requirements for pesticide use in Denver (Denver 1997). UDFCD and Chapter 7 of this Plan strongly advocate use of Integrated Pest Management (IPM) practices that help to reduce the level of pesticide and herbicide use through a variety of practices. Although water quality monitoring is not typically required as part of maintenance agreements, it is highly encouraged as an effective tool for determining if the BMP is functioning effectively. Stormwater quality monitoring guidelines can be downloaded from the International Stormwater BMP Database website (www.bmpdatabase.org).
Please see section starting on page 6-66 in the Water Quality Management Plan for charts on each BMP and advised maintenance.
BMP MAINTENANCE WILL BE ENFORCED UNDER DENVER’S CDPS STORMWATER PERMIT