YarrowBay promotes no net increase in phosphorus to Lake Sawyer

Black Diamond, Wash. – January 31, 2011 – In a letter to the City of Black Diamond, YarrowBay announced a “no net increase” plan with regards to phosphorus runoff to Lake Sawyer from The Villages and Lawson Hills MPDs. Phosphorus is responsible for algal blooms and other water quality issues and in order to protect the quality of Lake Sawyer, YarrowBay will implement a number of mechanisms to ensure that the lake’s existing phosphorus levels are not increased as a result of its MPD developments.

A major criticism of urban development, phosphorus runoff is limited by city code; however, unlike most master planned communities in Washington, YarrowBay is self-imposing a “no net increase” standard for its phosphorus runoff mitigation. This goes above and beyond the standards put in place by the Lake Sawyer Management Plan and exceeds all existing state and local requirements, including the Department of Ecology’s 2005 Stormwater Management Manual for Western Washington, which the City of Black Diamond has adopted and identifies phosphorous removal guidelines and treatment strategies.

“After reviewing the data on existing phosphorus runoff and estimates of the runoff from the planned MPD developments, we are confident that we can provide no net increase in the amount of phosphorus flowing into Lake Sawyer from our property,” said Colin Lund, YarrowBay’s Chief Entitlement Officer. “We want Black Diamond to remain an attractive place to live, and protecting Lake Sawyer is an important part of building this community.”

YarrowBay will implement “source controls,” such as requiring the use of phosphorus-free fertilizers in all parks, and will employ stormwater treatment facilities, such as large wetponds or large sand filters, to remove phosphorous from the MPDs’ stormwater runoff. In addition, low impact development techniques will be employed where appropriate on the MPD sites and YarrowBay will look for opportunities to use other phosphorus mitigation measures elsewhere in the City. As a result, The Villages and Lawson Hills MPDs will not cause any increase to Lake Sawyer’s existing phosphorus levels.

“Because YarrowBay has a long-term vision for these new districts of Black Diamond, they plan to invest in the monitoring necessary to assess their true potential impacts and in turn put in place the mitigations necessary to protect Lake Sawyer,” said Al Fure, a consultant with Triad Associates. “Small, piecemeal developments often aren’t able to assess and correct for their environmental impacts to this degree, but the size and scale of the YarrowBay developments present a unique opportunity to do this.”

YarrowBay will monitor phosphorus levels of stormwater currently exiting their MPD properties and draining toward Lake Sawyer to establish a baseline and, with its proposed monitoring program, will undertake all necessary mitigation measures to ensure “no net increase” of phosphorus levels above this baseline condition.

Fast Facts:

- “Old fashioned” methods of drainage control, such as roadside drainage swales, are now shown to provide a superior stormwater management benefit versus the curbs and pipelines seen in most new development. This is one example of “low impact development”.
- Individual responsibility can go a long way to protecting a shared treasured resource like Lake Sawyer:
- Washing your car on the lawn versus the roadway keeps phosphorous-laden detergent from entering the drainage system.
- Limiting fertilizer use and using phosphorous-free fertilizers keep phosphorous from entering the lake system.
- Being diligent in maintenance of your septic tank and drain field can help keep nutrients from finding their way to the streams and/or lake.
- Collection and proper disposal of pet waste can help protect nutrients from entering the drainage system and finding their way to the lake. Six dogs (or three chickens) are equal to one human’s waste.
- Erosion of soil is a major contributor to phosphorous pollution and is a reason erosion control protections during the winter rainy season are so important – the straw mulch you often see on cleared sites is a means of keeping the soil stabilized and keeping water from getting muddy while leaving the site.
- A variety of stormwater treatment solutions are now known to be effective in removing phosphorous from stormwater runoff. Some are commonly seen, such as large stormwater ponds, which settle out phosphorous-laden sediment, others are invisible to the untrained eye, such as bioretention swales, rain gardens and subterranean sand filter and settlement vaults.