Zoning Design Standards. Low Impact Development Code Update Thurston County Planning Commission March 2, 2016

Transcription

1 Zoning Design Standards Low Impact Development Code Update Thurston County Planning Commission March 2, 2016

2 Background Zoning regulations include limitations on the size and location of structures within a parcel Setbacks Height Limits Lot widths Impervious surface limits Standards are in place for either safety reasons or aesthetic preferences Allowing more flexibility with dimensional standards can help when utilizing LID site designs Impervious limits reduce the amount of paved area

3 Focus on Dimensional Standards Can setback distances be minimized to increase flexibility in regard to house or building location? Can the maximum building height be increased if building footprints are reduced? Can code be revised to incentivize or encourage minimizing building footprints?

4 Focus on Bulk and Dimensional Building Type a. Commercial, industrial and other nonresidential Arterial, State Highway Collector, Local and Side Rear and RR ROW Private Roads Yard Yard 35 from right of way easement or property line; 10 from right ofway of a flanking street 25 from right of way easement or property line; 10 from right ofway of a flanking street b. Residential exceeding two units per structure 30 ; 10 from right ofway of a flanking street 20 ; 10 from right ofway of a flanking street c. Single family and two family structures 30 ; 10 from right ofway of a flanking street 20 ; 10 from right ofway of a flanking street 6 10 d. Buildings housing animals

5 Recommendations Building Type a. Commercial, industrial and other nonresidential Arterial, State Highway Collector, Local and Side Rear and RR ROW Private Roads Yard Yard 3520 from right of way easement or property line; 10 from right ofway of a flanking street 2510 from right ofway easement or property line; 10 from right of way of a flanking street b. Residential exceeding two units per structure 3025 ; 10 from right ofway of a flanking street 20 ; 10 from right ofway of a flanking street c. Single family and two family structures 3025 ; 10 from right ofway of a flanking street 20 ; 10 from right ofway of a flanking street d. Buildings housing animals

6 Recommendations Amend minimum building size from 120 sq ft to 200 sq ft Maintain larger setbacks in agricultural/resource districts Shrink setbacks for industrial and some commercial zones (PI, LI, RRI, NC, RCC) Retain larger front setbacks in Arterial Commercial and Highway Commercial zones No change to height limits

7 Background: Impervious Limits Impervious surfaces prevent water from infiltrating into the ground and create larger volumes of stormwater runoff

8 Focus on Impervious Surfaces Does the code include maximum impervious surface limits for different land use types? Can the maximum impervious surface limits be reduced in residential areas?

9 Focus on Impervious Surfaces Thurston County currently has inconsistent impervious surface limits within the Zoning Code (TCC 20) Several residential zones allow up to 60% coverage by impervious surfaces this is far more than is used for most development New guidance from Ecology focuses on all hard surfaces, as well as impervious surfaces

10 Focus on Impervious Surfaces Arbitrary thresholds Green Cove 1.00 acre lot = 10,890 sq ft impervious 1.01 acre lot = 2,640 sq ft impervious RRR 1/5, Type C/D soils (slow infiltration capacity) 5.00 acre lot = 21,780 sq ft impervious 4.99 acre lot = 97,814 sq ft impervious Home in the Green Cove Basin

11 Focus on Impervious Surfaces Small Lots Average impervious area coverage on lots between 0.9 to 1.8 acres =15% Range: 7 28% This 1 acre property contains a large home, detached garage, and driveway. The impervious area is 19% or 8,200 square feet. This 1.5 acre property contains a large home, detached garage, and driveway. The impervious area is 14.5% or 9,500 square feet. Images are from 2012

12 Focus on Impervious Surfaces Small/Medium Lots Average impervious area coverage on lots between 1.8 to 4.6 acres =8% Range: 3 14% The 1.9 acre property below contains a large home with attached garage and large parking area. The impervious area is 10% or 8,200 square feet. The 2.2 acre property above contains a large home, detached garage, and driveway. The impervious area is 10% or 9,900 square feet. Images are from 2012

13 Focus on Impervious Surfaces Medium Lots Average impervious area coverage on lots between 4.6 to 9.5 acres =5% Range: 2 12% This 5 acre property contains a primary residence, garage, and driveway. The impervious area is 8.5% or 19,000 square feet. This 5.5 acre property contains a primary residence, attached garage, and driveway. The impervious area is 4.5 percent or 10,000 square feet. Images are from 2012

14 Focus on Impervious Surfaces Large Lots Average impervious area coverage on lots between 9.5 to 40 acres =5% Range: 2 12% The 15 acre property below contains a primary residence, driveway, and access road. The impervious area is 3.9% or 25,000 square feet. The 25 acre farm above contains a primary residence and numerous access roads. The impervious area is 5.8% or 66,000 square feet. Images are from 2012

15 Recommendations Use consistent definitions of impervious surface and hard surface across different areas of the code Develop consistent hard and impervious surface percentage limits for all zones Square foot limit for smaller lots Preexisting surfaces and structures can be replaced Additional 5% allowed for farm and forestry buildings Pervious surfaces calculated at 75% of total area Hard surface limit can be increased with a special use permit

16 Recommendations Credits (residential & resource zones only) Hard surface limits increased by 50%: Soils on site allow for full dispersion of stormwater runoff Landscape plan shows retention of existing native trees and vegetation on at least 20% of the site. The development is a Planned Residential Development (PRD) or Planned Rural Residential Development (PRRD) Hard surface limits increased by 100%: Landscape plan shows retention of existing native trees and vegetation on at least 65% of the site.

17 Recommendations Vegetation/ Restoration Credits Additional 1,000 square feet of hard surfaces above the limit if: 6,500 square feet retention of native trees and vegetation that are outside of any designated critical areas or buffers. 3,250 square feet retention of native trees and vegetation connecting designated critical areas or buffer 3,250 square feet replanting of native trees and vegetation within a riparian or wetland buffer area.

18 Discussion