[2023 AR] MS4 Permittees

2023 Report

Regulated Stormwater MS4 Permittees

All municipalities with Municipal Separate Storm Sewer Systems (MS4s) permits from the Colorado Department of Public Health and Environment (CDPHE) in the watershed have adopted stormwater programs consistent with Regulation 72 for development and redevelopment projects within their jurisdictions. Both construction-phase and permanent stormwater control measures are required. Regulation 72 requirements are more stringent than MS4 Permit requirements in Regulation 61 Colorado Discharge Permit System Regulations.

In 2023, the MS4 permittees conducted over 13,500  inspections of over 2,400  construction sites. In addition, the MS4 permittees required that construction site owners/operators install 29 new permanent control measures that are designed to reduce or eliminate pollutants in stormwater before it enters Cherry Creek or its tributaries.

Further information on each MS4’s program can be found in their annual reports in the links below.

Find out more about MS4 Permittees' programs​

 

Public Education

In addition to regulating development and redevelopment sites in the Cherry Creek Reservoir basin, MS4 permittees also have programs to educate the public, respond to and eliminate illicit discharges, and reduce or eliminate pollutants in stormwater from municipal operations. Examples of these efforts include:

 

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Grass Swale

Above & Beyond

swale click to learn more

Splash & DC Clear Outreach and Education

In 2023, Splash, an education and outreach cooperative for MS4 permittees in Arapahoe County, conducted over 20 outreach events and 4 Rain Barrel Workshops, Rainbarrel workshops include a barrel, installation guidances, residential water quality eduction and an installation kit.

DC Clear, an education and outreach cooperative for MS4 permittees in DouglasCounty, ran 12 residential and commercial awareness advertisements that reached approximately 80,000 households.

swale click to learn more

Colorado Department of Transportation Swale Study

In 2023, CDOT continued its study to determine the effectiveness of subsoiling as a maintenance practice to reestablish adequate infiltration within permanent water quality swales. CDOT conducted infiltrometer tests in 2023 to determine how well the increased infiltration rates persisted over time. Unfortunately, heavy rains in May of 2023 caused a large amount of erosion and sediment deposition at the test site (see before and after pictures). Infiltrometer test results in 2023 showed a decrease in infiltration below the initial base line. Since the rains in May of 2023 were well above average, CDOT plans to conduct this test at another site within the basin in 2024.

swale click to learn more

Araphahoe County and Douglas County Environmental Health Programs Waste Diversion and Recycling

Douglas County, including Parker, Castle Rock, and Castle Pines and SEMSWA’s service area in Centennial and unincorporated Arapahoe County offer a Hazardous Household Waste (HHW) Program. The program encourages the responsible disposal of HHW and provides a year round collection or convenient drop-off to help prevent improper disposal of hazardous materials which can negatively impact water quality.

The Green Waste Collection and Recycling Program consisted of stationary drop-off locations for all Douglas County residents. This collection helped reduce nutrient pollution in the Cherry Creek Watershed.

2023 Stormwater Permits and Inspections for Construction and Post-Construction Development

 
 
1 Reinspection fees issues
2 SCNs wutg Fubak Acceotabce after 2007
3 Inspections of SEMSWA owned/operated SCMs
4This includes all escalation of violation level with an assessment of a re-inspection fee and/or issuance of formal Stop Work Orders
5All construction sites listed above within the CCB in 2023 meet the tier 2 designation per Reg 72, no active projects meeting the Tier 3 designation in GV/CCB in 2023
6 Sites listed utilitized onsite receiving pervious area to meet requirements for development (we did not previously consider RPA in our total number of BMPs/CMs so to maintain consistency in reporting, 0 new facilities reported)
7All facilities requiring inspection under O&M program were conducted/completed by former GV Engineer in 2021 for current permit term
8This includes the 4 ponds in initial acceptance from question 5 since they are official installed.
9This number includes ponds that went into initial acceptance this year, which means their construction was inspected and finalized.
10 Information for Castle Rock is as a whole. Castle Rock does not track by watershed.
11 These are written notices of violation, including 3 stop work orders for Castle Rock.
12 This includes 147 facilities inspected, 33 facilities maintained, and 0 retrofitted.
13 Town of Parker: 0 Retrofitted Flood Control Facilities and 384 maintained. All facilities requiring inspection under O&M program were conducted/completed by former GV Engineer in 2021 for current permit term
14 CDOT completed permanent CM compliance inspections in 2020 as required by our MS4 Permit which also expired in 2020. CDOT's MS4 Permit has been administratively continued. 27 - Permanent control measure, long-term operations inspections performed in 2023.