Get the free STORMWATER CALCULATION SHEET

JEFFERSON COUNTY DEPARTMENT OF COMMUNITY DEVELOPMENT 621 Sheridan Street Port Townsend Washington 98368 360/3794450 800/8312678 360/3794451 Fax STORMWATER CALCULATION SHEET Pursuant to Unified Development

How to fill out stormwater calculation sheet

How to fill out a stormwater calculation sheet:

1. Gather the necessary information: Before you begin filling out the stormwater calculation sheet, gather all the required data. This may include site dimensions, drainage area, impervious area, rainfall data, and any additional information specific to your project.
2. Determine the applicable stormwater regulations: Familiarize yourself with the stormwater regulations that apply to your project. These regulations may vary depending on your location and the specific requirements set by local authorities or environmental agencies.
3. Identify the sections of the calculation sheet: Separate the stormwater calculation sheet into its different sections. This may include sections for rainfall data, runoff coefficient calculation, drainage area calculations, storage volume calculations, and pollutant load calculations.
4. Fill in the rainfall data: In the rainfall data section, input the relevant rainfall information for your project location. This typically includes the rainfall intensity for various-design return periods.
5. Calculate the runoff coefficient: Determine the runoff coefficient based on the land use types and characteristics of your site. This coefficient represents the portion of rainfall that will become stormwater runoff.
6. Calculate the drainage area: Determine the drainage area of your site. This includes all impervious surfaces, such as roofs, parking lots, and roads, that contribute to stormwater runoff. Measure the area of each impervious surface and sum them up to obtain the total drainage area.
7. Perform storage volume calculations: If your project includes stormwater management practices such as detention ponds or rain gardens, calculate the required storage volume to accommodate the excess stormwater runoff. Consider factors like the design storm frequency and the required water quality treatment volume.
8. Calculate pollutant loads: If applicable, calculate the pollutant loads that will be generated by the stormwater runoff from your site. This involves estimating the concentrations of pollutants based on the land use and applying the appropriate loading rates.

Who needs a stormwater calculation sheet?

1. Construction Companies: Construction companies involved in building or improvement projects are typically required to submit a stormwater calculation sheet as part of the overall stormwater management plan. This ensures compliance with regulations and helps minimize any negative environmental impacts resulting from construction activities.
2. Land Developers: Developers working on new projects or significant modifications to existing sites often need to prepare a stormwater calculation sheet. This allows them to assess the potential impacts of their development on stormwater runoff and design appropriate measures to manage it.
3. Engineers and Design Professionals: Engineers and design professionals responsible for site planning, stormwater management design, or drainage system design rely on stormwater calculation sheets to accurately quantify, analyze, and mitigate stormwater runoff. These professionals use the sheet to ensure compliance with relevant regulations and design effective stormwater management systems.

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What is stormwater calculation sheet?

Stormwater calculation sheet is a document that calculates the volume of stormwater runoff expected at a site based on factors such as impervious surfaces, precipitation rates, and drainage areas.

Who is required to file stormwater calculation sheet?

Property owners or developers who are planning construction projects that will create impervious surfaces and impact stormwater runoff are required to file a stormwater calculation sheet.

How to fill out stormwater calculation sheet?

To fill out a stormwater calculation sheet, one must gather data on impervious surfaces, drainage areas, and precipitation rates for the site. This information is then used to calculate the volume of stormwater runoff expected.

What is the purpose of stormwater calculation sheet?

The purpose of a stormwater calculation sheet is to assess the potential impact of a construction project on stormwater runoff, and to design stormwater management systems to mitigate this impact.

What information must be reported on stormwater calculation sheet?

Information such as impervious surface area, drainage areas, precipitation rates, and calculations of stormwater runoff volume must be reported on a stormwater calculation sheet.