Engineering Improvement Determination Online Form

Engineering Improvement Determination

This request is intended to help an engineer, architect or an owner better understand what is expected of the applicant with regard to engineering improvement determination required when preparing a Single Family Building Permit Application for review and approval as required for new developments within the City of Renton.

 Specific Code Section(s) related to this document
RMC 4-6Street and Utility Standards


  1. Fill out the Engineering Improvement Determination Request information below.
  2. Submit request.
  3. Upon submission, the Applicant will receive a response from the City within three business days with a determination on the required engineering improvements (including potential right of way dedication) and storm drainage review type.
  4. The required engineering improvements and/or drainage review identified in the Engineering Improvement Determination shall be addressed and submitted as part of the Applicant’s Single Family Permit Application. The submittal items noted in the Determination are required to be submitted with the Building Permit Application.






If you need assistance finding your property address and/or parcel number, please visit the City of Renton GIS Mapping application. COR MAPS.




Please check either New Single Family Home, Home/Garage Addition or other site/building improvements and complete the requested information accordingly.

New Single Family Home Home/Garage Addition and/or other improvement

Is this home part of an existing plat or short plat?

Not Sure

 If yes, please list the recorded year, recorded name of the plat or short plat, and the lot number.





Provide a brief description of the addition and/or other improvement. Include type of addition, size (square footage), etc

Existing Site Conditions

Provide existing site condition areas in square feet (SF)

Proposed Site Conditions

Provide proposed site condition areas in square feet (SF)

Security Measure


Impervious Surface Area

A non-vegetated surface area that either prevents or retards the entry of water into the soil mantle as under natural conditions before development; or that causes water to run off the surface in greater quantities or at an increased rate of flow compared to the flow present under natural conditions prior to development (e.g., roofs, driveways, etc.). Common impervious surfaces include, but are not limited to, roof, walkways, patios, driveways, parking lots, or storage areas, areas that are paved, graveled or made of packed or oiled earthen materials or other surfaces that similarly impede the natural infiltration of surface water or stormwater. For the purposes of applying the impervious surface thresholds, permeable pavement, vegetated roofs, and pervious surfaces with underdrains designed to collect stormwater runoff are considered impervious surface while an open uncovered flow control or water quality facility is not.

New Impervious Surface Area

The addition of a man-made, modified, or compacted surface like roofs, pavement, gravel, or dirt; or the addition of a more compacted surface, such as resurfacing by upgrading from dirt to gravel, asphalt, or concrete; upgrading from gravel to asphalt, or concrete; or upgrading from a bituminous surface treatment (“chip seal”) to asphalt or concrete. Permeable pavement and vegetated roofs are considered new impervious surface for purposes of determining whether the thresholds for application of minimum requirements are exceeded, as are lawns, landscaping, sports fields, golf courses, and other areas that have modified runoff characteristics resulting from the addition of underdrains designed to collect stormwater runoff. Open, uncovered retention/detention facilities shall not be considered impervious surfaces for purposes of determining whether the thresholds for application of minimum requirements are exceeded. Open, uncovered retention/detention facilities shall be considered impervious surfaces for purposes of runoff modeling.

New Pollution Generating Impervious Surface (PGIS)

New impervious surface that is pollution-generating impervious surface or any alteration of existing pollution-generating impervious surface that changes the type of pollutants or results in increased pollution loads and/or concentrations.
Pervious Surface Area

Any surface material that allows stormwater to infiltrate into the ground. Examples include lawn, landscape, pasture, and native vegetation areas. Note for purposes of threshold determination and runoff volume modeling for detention and treatment, vegetated roofs and permeable pavements are to be considered impervious surfaces along with lawns, landscaping, sports fields, golf courses and other areas that have modified runoff characteristics resulting from the addition of underdrains.
Pollution Generating Impervious Surface (PGIS)

An impervious surface considered to be a significant source of pollutants in stormwater runoff. Such surfaces include those that are subject to vehicular use, industrial activities, or storage of erodible or leachable materials, wastes, or chemicals and that receive direct rainfall or the run-on or blow-in of rainfall. A covered parking area would be considered PGIS if runoff from uphill could regularly run through it or if rainfall could regularly blow in and wet the pavement surface. Metal roofs are also considered PGIS unless they are coated with an inert, non-leachable material (see Reference Section 11-E); or roofs that are exposed to the venting of significant amounts of dusts, mists, or fumes from manufacturing, commercial, or other indoor activities. PGIS includes vegetated roofs exposed to pesticides, fertilizers, or loss of soil. Other roofing types that may pose risk but are not currently regulated are listed Reference Section 11-E. Lawns, landscaping, sports fields, golf courses, and other areas that have modified runoff characteristics resulting from the addition of underdrains that have the pollution generating characteristics described under the “pollution-generating pervious surface” definition are also considered PGIS.
Replaced Impervious Surface Area

Any existing impervious surface on the project site that is proposed to be removed and re-established as impervious surface, excluding impervious surface removed for the sole purpose of installing utilities or performing maintenance on underground infrastructure. For structures, removed means the removal of buildings down to the foundation. For other impervious surfaces, removed means the removal down to base course or bare soil. For purposes of this definition, base course is the layer of crushed rock that typically underlies an asphalt or concrete pavement. It does not include the removal of pavement material through grinding or other surface modification unless the entire layer of PCC or AC is removed. Replaced impervious surface also includes impervious surface that is moved from one location to another on the project site where the following two conditions are met: (A) runoff characteristics and volumes remain the same or are improved in the area where the existing impervious surface is removed , and (B) impervious surface at the new location is either designated as non-pollution generating or the pollution generating characteristics remain unchanged compared to that of the original location.
Replaced Pollution Generating Impervious Surface (PGIS)

Replaced impervious surface that is pollution-generating impervious surface.

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