Grand Haven Pond Study: An Investigation to Reduce Nutrient Loads and Evaluate Alternative Management Practices in Stormwater Ponds Mark Clark Wetlands and Water Quality Extension Specialist Partnership for Water, Agricultural and Community Sustainability at Hastings Soil and Water Science Department

Stormwater Pond Regulatory Function Protect infrastructure from flooding and reduce impacts on downstream environment due to changes in the quantity and quality of stormwater runoff from development. Minimum treatment expectation is 80% load reduction of contaminants. Actual load reduction for wet detention ponds is more likely 40-60% phosphorus reduction and 40% nitrogen reduction. Why? Limited removal potential in conventional pond design for dissolved contaminants. Minimum treatment expectation is 80% load reduction of contaminants. Actual load reduction for wet detention ponds is more likely 40-60% phosphorus reduction and 40% nitrogen reduction. Why? Limited removal potential in conventional pond design for dissolved contaminants.

Stormwater Pond Aesthetic Expectations Pond frontage often sold as “Lake Front Property”, homeowner expectation is clear water, minimal plant growth, pristine low nutrient water body. Typical Management Approach: Suppress algae and plant growth using herbicides, with little attention paid to nutrient retention function of ponds and source control. Typical Management Approach: Suppress algae and plant growth using herbicides, with little attention paid to nutrient retention function of ponds and source control. Reality: Stormwater pond reflects nutrient loads from watershed and soils underlying pond often resulting in planktonic and filamentous algae blooms or growth of submerged aquatic vegetation. Reality:

Management Conundrum Algae and vegetation is growing in stormwater ponds in response to nutrient runoff from watershed. Plant growth in ponds can reduce water column nutrient levels thus improve water quality function of stormwater pond reducing downstream impacts. Herbicide suppression of vegetation is often used to improve aesthetics in pond, but may reduce treatment potential of ponds. Many state waters are being listed as impaired due to excess nutrients that are partly the result of inadequate treatment of stormwater Copper Sulfate – the most widely used herbicide for pond management – may be banned for use in stormwater ponds.

Grand Haven CDD Symposium (January 22, 2008) “What ecologically sound and fiscally responsible measures can the governmental organizations, Hampton Golf, and all property owners/residents of Grand Haven take to: 1. Maintain the health of our storm water detention ponds (aka “lakes”)? 2. Correct and prevent recurring problems such as algae blooms?”

Factors Contributing to Pond Issues (Fill Soils Phosphorus Concentration) Fill Material pH = 7.3 leachable P = ppm (5,400% increase) Fill Material pH = 7.3 leachable P = ppm (5,400% increase) Native Soil pH = 5.0, leachable P = ppm Native Soil pH = 5.0, leachable P = ppm 77% of soils tested in Grand Haven tested high or very high with respect to available phosphorus indicating no need for addition of phosphorus fertilizer

In 2008 approximately 4 tons of nitrogen and 2 tons of phosphorus were applied to common areas and the golf course through reclaimed water. No accounting of these nutrients when made when determining fertilizer application rates Irrigation rate was three times UF/IFAS recommended rate in common areas Factors Contributing to Pond Issues (Nutrients in Reclaimed Water)

Grand Haven Project Underway Source Control is Key to long-term reduction in nutrient load to ponds –Community adopting Florida Fertilizer Task Force / UF/IFAS Landscape Best Management Practices –Presently evaluating ways to reduce and account for nutrient loads in reclaimed water –Promoting establishment of minimum maintenance pond bank vegetation above waterline –Community monitoring 5 ponds under LAKEWATCH program Initiating study of stormwater pond alternative management practices

Alternative Pond Treatments Littoral Shelf Planting Aeration Carp Control / SAV Copper Sulfate

Project Status and Broader Application of Information All treatments implemented (April 2009) Web based “Pond observer” and on site volunteer monitoring to be initiated in June 2009 –Water quality, aesthetics, aquatic ecology Periodic assessment of treatment efficacy to be disseminated to homeowners. Findings will be used to guide future landscape and pond management decisions to improve pond and downstream water quality.

I’d like to thank those members of the Grand Haven CDD Board, HOA, Management and Citizen Volunteers that are stepping up to address these issues. Through their willingness and efforts we will increase knowledge and guidance for others.