2021 Kitsap County Stormwater Design Manual
2021 Kitsap County
Stormwater Design Manual

3.5.4 S449: BMPs for Nurseries and Greenhouses

Description of Pollutant Sources: These BMPs are for use by commercial container plant, greenhouse grown, and cut foliage production operations. Common practices at nurseries and greenhouses can cause elevated levels of phosphorus, nitrogen, sediment, bacteria, and organic material, which can contribute to the degradation of water quality.

Pollutant Control Approach: Minimize the pollutants that leave the site by controlling the placement of materials, stabilizing the site, and managing irrigation water.

3.5.4.1 Applicable Operational BMPs

  • Establish nursery composting areas, soil storage, and mixing areas at least 100 feet away from any stream or other surface water body and as far away as possible from drainage systems.

  • Do not dispose of collected vegetation into waterways or storm sewer systems.

  • Do not blow, sweep, or otherwise allow vegetation or other debris into the drainage system.

  • Regularly clean up spilled potting soil to prevent its movement, especially if fertilizers and pesticides are incorporated (Haver 2014).

  • Use soil mixing and layering techniques with composted organic material to reduce herbicide use and watering.

  • Utilize soil incorporated with fertilizers and/or pesticides immediately; do not store for extended periods (Haver 2014).

  • Cover soil storage and compost storage piles. (See Vol II–3.5.2 S429: BMPs for Storage or Transfer (outside) of Solid Raw Materials, Byproducts, or Finished Products)

  • Dispose of pathogen-laced potting substrate and diseased plants appropriately.

  • Place plants on gravel, geotextile, or weed cloth to allow infiltration and minimize erosion, including inside greenhouse structures (Haver 2014).

  • Properly reuse, recycle, or dispose of used polyfilm, containers, and other plastic-based products so that they do not collect stormwater (FDACS 2014).

  • Evaluate and manage irrigation to reduce runoff, sediment transport, and erosion.

    • Place irrigation inputs to keep moisture primarily in the plant’s root zone. This will significantly reduce nutrient related impacts from fertilizers (FDACS 2014).

    • Avoid over-irrigating. This may exceed the soil’s water-holding capacity and lead to runoff or leaching (FDACS 2014).

    • Consider and adjust as needed the uniformity of application, the amount of water retained within the potting substrate, and the amount of water that enters containers compared to that which exits the containers and/or falls between containers (FDACS 2014).

    • Consolidate containers and turn off irrigation in areas not in production. This may require individual on/off valves at each sprinkler head (Haver 2014).

    • Based on the stage of plant growth, space containers and flats as close as possible to minimize the amount of irrigation water that falls between containers (FDACS 2014).

    • Group plants of similar irrigation needs together (FDACS 2014).

    • Consider minimizing water losses by using cyclic irrigation (multiple applications of small amounts) (FDACS 2014).

    • Consider using sub-irrigation systems (e.g. capillary mat, ebb-and-flow benches, and trays or benches with liners); these systems can conserve water and reduce nutrient loss, particularly when nutrients are supplied in irrigation water that is reused (FDACS 2014).

    • See S450 BMPs for Irrigation in Volume IV of the Ecology Manual for additional BMP considerations.

  • See S443 BMPs for Fertilizer Application and S435 BMPs for Pesticides and an Integrated Pest Management Program in Volume IV of the Ecology Manual.

3.5.4.2 Applicable Structural BMPs

  • Use windbreaks or other means (e.g. pot in pot) to minimize plant blow over (FDACS 2014).

  • Cover potting areas with a permanent structure to minimize movement of loose soil. Use a temporary structure if a permanent structure is not feasible (Haver 2014).

  • Control runoff from central potting locations that have a watering station used to irrigate plants immediately after potting. Either:

    • Collect runoff in a small basin and reuse the runoff.

    • Or, route runoff through an onsite vegetative treatment area.

    • Or, use a graveled area and allow runoff to infiltrate.

  • Surround soil storage and compost storage areas with a berm or wattles.

  • Utilize a synthetic (geotextile) groundcover material to stabilize disturbed areas and prevent erosion in areas where vegetative cover is not an option (FDACS 2014).

  • In areas with a large amount of foot traffic, use appropriate aggregate such as rock and gravel for stabilization (FDACS 2014).

  • Store potting substrate that contains fertilizer in a dedicated area with an impermeable base. If the storage area is not under a roof to protect it from rainfall, manage runoff by directing it to a stormwater treatment area (FDACS 2014).

In addition to the requirements listed above, Kitsap County also requires the following for site access:

  • Limit vehicle access and exit to one route, if possible.

  • Stabilize access points with a pad of quarry spalls, crushed rock, or other equivalent BMPs, to minimize tracking sediment onto roads. See BMP C105: Stabilized Construction Access in Volume II of the Ecology Manual.

  • Locate wheel wash or tire baths on site, if the stabilized entrance is not effective in preventing tracking sediment onto roads. See BMP C106: Wheel Wash in Volume II of the Ecology Manual.

  • If sediment is tracked off site, clean the affected roadway thoroughly at the end of each day, or more frequently as necessary (for example, during wet weather). Remove sediment from roads by shoveling, sweeping, or pickup and transport of the sediment to a controlled sediment disposal area.

  • Conduct street washing only after sediment removal in accordance with the previous bullet. Control street wash wastewater by pumping back on site or otherwise preventing it from discharging into systems tributary to waters of the State.