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CSGP: Assess Your Site

There is quite a lot of research that should be conducted prior to completing the Notice of Intent (NOI) and the Stormwater Pollution Prevention Plan (SWPPP) for your site. It may be helpful to look at our Example NOI and Ecology’s SWPPP template as you assess your site to get an idea of what information you may need. This information includes, but is not limited to, the items below: 

Site History

Gathering information regarding the history of your site can be a crucial step in gaining permit coverage without delay. You will want to gather any information about your site that you can find. This can be existing site maps or drawings, information regarding any previous activities that occurred on the site, or existing geotechnical or environmental reports.

The State Environmental Policy Act (SEPA) is a process used to determine the potential environmental impact of projects in the state. In many cases, a SEPA checklist may have already been completed for your site. This document will provide important information that will help you fill out these permit documents and determine the site-specific regulatory requirements for your site such as specific site needs or endangered species that may be present in the area. For more information, see our SEPA page.
Considerations When Purchasing or Leasing an Existing Site
If a site is being redeveloped by a previous property owner it is important that some investigation has been done to prove that the soil or groundwater is not contaminated on-site from a previous activity. If the site has contaminated soils or groundwater, there are additional provisions that must be taken.


You will need to collect the contact information of the site owners and operators. It is important that the site owner is aware of the permit requirements, and has given proper authority to the operator via contract and/or signatory authority.  It is also important to identify who the operator is, and if that will change throughout the life of the project, requiring a Transfer of Coverage.

Transfer of Coverage
When identifying the operators, you should consider if and how the operators will change over the life of the project. In many cases the operator will be a general contractor, however, there are projects where one type of operator transfers responsibility to another. This type of change often requires a Transfer of Coverage. Some projects, such as home building, may have several Transfers of Coverage. It is important to have a good understanding of all the parties that are going to be involved in the project and to identify who will ultimately have permit responsibilities at each phase of construction.

Soil Type 

It is crucial to understand the soil type that you will be working in. The composition of soil plays a critical role in determining the most effective ways of preventing erosion and sediment control issues and staying in compliance with your stormwater permit. 

There are several ways to evaluate the soils on your site, but one of the most universal ways is to access the USDA Web Soil Survey. If you put in your address or get close to the area and draw an AOI (area of interest) box where land clearing will occur, you will be provided a narrative description of the surrounding soil types. These surveys may also be accessed via a plug-in to Google Earth.

Weather Patterns

It is important to consider how the climate your facility is in will affect your site. Different areas of Washington can experience significantly different weather patterns. Western Washington, for example, is known for its long periods of light rain during the winter, while areas of Eastern Washington are often drier but may experience heavier downpours or significant snowfall. The rainfall intensity (how hard it is raining), duration (how long it is raining), and seasonality (what time of year it rains) can play an important role in how stormwater is managed on your site, and how to most efficiently finish your project. 

Predictive Weather Resources

Receiving Waters & Sensitive Species

It is important to know where the stormwater goes after it leaves your site. Some sites may simply run off into a field and infiltrate into the ground, while others may enter a complex system of ditches and drainages before entering a sensitive water body. It may be useful to use local GIS mapping to see where any of these conveyances lead. The receiving waters your stormwater enters can play a critical role in sampling, monitoring, and treatment requirements, so it is important that the receiving waters are correctly identified.

Impaired Waters
Ecology assesses the water quality of rivers, lakes, and marine waters to ensure resource protection under the Clean Water Act. If identified, polluted waters are added to an impaired waterbodies list commonly referred to as the 303(d) list, and are often later prescribed a TMDL to help improve water quality. Facilities that discharge to waters on this list will likely be required to adhere to more stringent water quality standards for their stormwater discharge and may be required to perform additional sampling. The Ecology integrated report and Water Quality Atlas map can assist with locating and identifying these impaired waters.
Sensitive Species
Wildlife can also influence your stormwater management practices on construction activity. Wildlife influences are often communicated through the SEPA process, but the Department of Fish and Wildlife or the Department of Natural Resources might be options for you to make those discoveries as well.
It is important to also identify any wetlands or drywells in or surrounding the property. These must be identified on site maps and may influence stormwater management practices on the project. Wetlands inventories are available on the National Wetland Inventory page or often with your local jurisdiction.

Local Requirements

Local jurisdictions may have requirements that will influence BMP selection, drainage design, and operational influences (noise restrictions, traffic flow, etc). These jurisdictions may also have lower disturbance thresholds that require additional permitting. It is important to review local codes and regulations before starting a project.