Skip to content

ISGP: Assess Your Site

There are several things that need to be considered prior to and during your application for a permit. You will need to conduct quite a lot of research 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 Ecology’s SWPPP Template and this Example NOI as you assess your site to get an idea of what information you may need. Please note that 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 is available to you. This can be existing site maps or drawings, information regarding any previous industrial activity that occurred on the property, information about any permit requirements or challenges previous operators on your site faced, and any information documenting existing contamination on the property. These items will all allow you to fill out the required applications and forms much faster.

The State Environmental Policy Act (SEPA) is a process used to determine the potential environmental impact of projects in the state. In some 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. In cases of new facilities or facilities that are making significant process changes, a SEPA must be completed. Your local jurisdiction or ecology should notify you of your SEPA requirements as you navigate the permitting process. This process can take time and cause delays, so if you are unsure of your facility’s SEPA requirements it may be a good idea to reach out to your local jurisdiction to find out. For more information on the SEPA process, see our SEPA page. It can be helpful to talk with the previous site owner or operator and determine if they had a site permit. If they did, they can likely offer insight into any issues or compliance challenges they faced. If you are conducting the same operations under a new name and/or new management, you will need to conduct Modification of Permit and Transfer of Permit coverage.
Purchasing or Leasing an Existing Site
If purchasing or leasing a site from a previous property owner and a new or different industrial process is expected to occur, it is important that some investigation has been done to prove that the soil or groundwater are not contaminated on site from a previous activity. If the site has contaminated soils or groundwater, there are additional provisions that must be taken. It can be helpful to talk with the previous site owner or operator and determine if they had a site permit. If they did, they can likely offer insight into any issues or compliance challenges they faced. If you are conducting the same operations under a new name and/or new management, you will need to conduct Modification of Permit and Transfer of Permit coverage.


You will need to gather the contact information of the site owner and operators. If the property is being leased, it is important that the landlord is aware of the permit requirements you are required to comply with. You will also want to find out what maintenance services are included in your lease as well as the timing and frequency of those services. Items such as site sweeping and catch basin cleaning are required under the permit, so it is helpful to know if these activities are included in your lease. 

If the corporate office for your operation is out of state, it is important that someone on site is given signatory authority to submit information to ecology and to receive Ecology communications. This information is covered more in-depth in the Apply for Coverage section


You will also need to evaluate your site’s infrastructure and start thinking of how stormwater will interact with it. Walk your site and look closely at the infrastructure. Identify all of the impervious surfaces (hard surfaces that won’t infiltrate such as roofs, roads, parking lots, etc.) on your site and take note of the material they are made from and their condition. You will also want to find all the subgrade piping and other drainage infrastructure noting their materials and conditions. As part of the permitting process, you will be required to identify where these structures flow to, so you may want to reference site maps as you walk your site. You may also want to have discussions with previous site owners or your local jurisdictions to ensure your understanding of the subgrade infrastructure is correct.

Why Infrastructure Considerations Are Important
Many people are surprised at the things that are considered potential sources of stormwater pollution on a site. Potential pollution sources aren’t just the stockpiles of bulk materials, or areas for refueling- they can be things like galvanized roofs that can release zinc into stormwater if left unpainted, or alligatored pavement that can collect pollutants from car and equipment as they drive over the cracked surface. It is much cheaper for a facility to identify these potential sources and implement ways to reduce or eliminate pollution at the source, than it is to get caught up in a non-compliance scenario.
Considerations For Sites With Many Unpaved Surfaces
Some operations may take place in areas with a lot of unpaved surfaces. If this is the case, you may need to consider the soil type you are going to be working in. This can play an important role in how stormwater interacts with your site, and what potential options are available for managing that stormwater. 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.


It is important to start thinking about 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.

Predictive Weather Resources
Two tools that can be useful are the NOAA Predictive Weather Center and Climate Prediction Center. The Western Regional Climate Center also assesses probabilities for certain size storm events and can be a useful tool to help predict site discharge probabilities.

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 all the rivers, lakes and marine waters in the state every two years. This assessment identifies waters with pollution issues in need of cleanup. Waters that are identified as having pollution issues are added to an impaired waterbodies list commonly referred to as the 303(d) list, and are given a prescribed TMDL to help improve water quality. Facilities that discharge to waters on this list are often required to adhere to higher water quality standards for their stormwater discharge and may be required to sample for additional contaminants. The Ecology Integrated Report and Water Quality Atlas Map can assist with locating and identifying these impaired waters.
Sensitive Species
In some cases, the waterbody itself may not be sensitive, but wildlife or plants that utilize that waterbody may be. Threatened or endangered species that utilize the water surrounding the property may require additional stormwater management provisions. Sensitive species are often discovered in 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 will have to be identified on site maps and may influence stormwater management at a facility. Wetlands inventories are available on the National Wetland Inventory website or often with your local jurisdiction.