HomeMy WebLinkAboutPN_Hirani Project NarrativePROJECT NARRATIVE
a. Project name, size and location of site: The project will be known as the Hirani Residence
Retaining Wall. The site located at 2708 Williams Avenue in Renton, Washington
encompasses 9,294 square feet and is occupied by an existing single-family residence.
b. Zoning Designation of site and adjacent properties: The site is zoned for residential use
and is bounded to the north and south by single-family residences, to the west by a cul-
de-sac, and to the east by an undeveloped tract owned by the homeowner’s association
(HOA) of the subdivision.
c. Current use of the site and any existing improvements: The lot is occupied by a single-
family residence. The lot comprises a relatively level portion where the residence is
situated, western-sloping driveway, and backyard containing partially constructed
terraced wall composed of PisaLite® blocks. A rockery wall up to about 10 feet tall is
located near the northern property boundary. A rockery wall up to about 6 feet tall is
located near the southern property boundary. The terraced walls are situated between
the two rockery walls.
d. Special Site Features: According to the City of Renton (City), the site contains regulated
slopes classified as landslide hazard areas and erosion hazard areas.
e. Soil Type and Drainage Conditions: Subsurface conditions on the project site were
inferred from the field explorations conducted for a geotechnical engineering study of the
site, visual reconnaissance of the site, and a review of applicable geologic literature.
Subsurface explorations advanced encountered fill, recessional outwash, and glacial till.
The native deposits encountered are in general agreement with mapped geologic
conditions presented on the regional geologic map (Geologic Map of King County,
Washington, Booth, Troost, and Wisher, GeoMap NW, March 2007) which indicates that
the area is underlain by Vashon recessional outwash and glacial till. The interpretation of
the sediments encountered in the explorations agrees with the referenced geologic map.
Groundwater was not observed in the exploration borings completed for this project at
the time of drilling in January 2020. However, it should be noted that perched
groundwater seepage may occur during the winter and spring months. Perched
groundwater occurs when surface water infiltrates down through relatively permeable
soils such as the lodgement till and becomes trapped or “perched” atop a comparatively
impermeable barrier. This infiltration can occur at great distances from the area where
the groundwater is encountered. It should be noted that fluctuations in the level of the
groundwater may occur due to the time of year and variations in the amount of rainfall.
The quantity and duration of flow from excavations made into the perched zone will vary
depending on season, topography, and soil grain size.
f. Proposed use of the property and scope of the proposed development: The use of the
property will remain unchanged as a single-family residence. Improvement plans to the
property will involve removal of the existing non-engineered gravity block walls and
reconstruction of two engineered gravity block walls up to 4 feet tall (exposed height)
using the existing PisaLite blocks and no-fines concrete (NFC) backfill. Improvement plans
will also include installation of new pavers for patio and walkways, decorative aggregate,
artificial turf between the terraced walls and sloping ground above the existing 10-foot-
tall rockery wall along the northern property boundary, and planting beds. The amount
of existing impervious area is about 4,401 square feet and proposed additional
impervious area is about 4,041 square feet.
g. Proposed off-site improvements: None
h. Total estimated construction cost and estimated fair market value of the proposed
project: $100,000
i. Estimated quantities and types of materials involved if any fill or excavation is
proposed:
Excavation of site soils for upper and lower block walls: 54 cubic yards
Wall backfill reusing site soils: 12 cubic yards
Controlled density fill for structural keyway below lower wall: 25 cubic yards
No-fines concrete wall backfill for upper and lower walls: 20 cubic yards
j. Number, type and size of trees to be removed: No trees are present in the area of the
planned improvements.
k. Explanation of any land to be dedicated to the City: Not applicable