Seawater Intrusion Protection Zones


  • Title: Seawater Intrusion Protection Zones
  • Shapefile name: sipz.shp
  • Source: Jefferson County Central Services - GIS
  • Software format: E.S.R.I. ArcView™ 3.x
  • Coordinate system: Washington State Plane North (5601), NAD83
  • Date of shapefile update: October 16, 2003



Polygon theme showing three types of seawater intrusion protection zones. The base SIPZ was calculated by buffering the Washington State Department of Natural Resources Ordinary Highwater shoreline to a distance of 1,320 feet. At Risk and High Risk SIPZ are based on chloride readings of wells. Information about the seawater intrusion zones and regulations can be found at the Department of Community Development's Seawater Intrusion Page.

Frequency of Update

  • Annual


Since the base SIPZ was based on the DNR OHW shoreline, the zone will not line up precisely with Jefferson County parcels along the parcel shoreline. Many of the well locations were calculated based on the parcel centroid. At Risk and High Risk zones based on these well points may be off by as much as the distance between the parcel centroid and the parcel boundary furthest from the centroid.

For informational purposes only - Jefferson County does not attest to the accuracy of the data contained herein and makes no warranty with respect to its correctness or validity. Data contained in this map is limited by the method and accuracy of its collection.

Attribute Fields


Note: Below are short explanatory notes about the different SIPZ zones. Please consult the actual regulations at the links above for detailed information.
  • Coastal SIPZ: There are no regulations affecting owners in this zone. High chloride wells that fall inside a Coastal SIPZ automatically generate new At-Risk and High-Risk zones. Owners living inside a Coastal SIPZ are encouraged to use drought-tolerant landscaping and conserve water.
  • At Risk SIPZ: The regulations apply only to new home construction. Owners are required to enter into a well monitoring program approved by the County. This is similar to the monitoring agreements that are required when the County issues a permit for an alternative on-site sewage disposal system. There may be a charge to cover the costs of the monitoring. The applicant is also required to install a flow meter and is encouraged to use drought-tolerant landscaping and conserve water.
  • High Risk SIPZ: The regulations are generally triggered by new home construction. Building permit applicants will be required to conduct a hydrogeologic assessment to indicate that their water use will not degrade water quality in the aquifer. If such an assessment can prove that there would be no degradation, the applicant can use the well provided that they install a flow meter and submit a water conservation plan to Jefferson County. If such an assessment cannot be made, the applicant must use another water source for their building. The High Risk SIPZ also expand the Washington State Department of Ecology's "sea-salt water intrusion areas". New wells may be denied in this zone if DOE determines the well would violate the state administrative code.

Contact Information

  • Regulatory Information: Jefferson County Department of Community Development, 360-379-4450.
  • Map Layer Creation: Jeff Miller, Jefferson County Central Services GIS, 360-385-9148.