RESOURCE STEWARDSHIP DEPARTMENT Cynthia Wilson Director

Transcription

1 COUNTY COMMISSIONERS Creating Solutions for Our Future Cathy Wolfe District One Sandra Romero District Two Bud Blake District Three RESOURCE STEWARDSHIP DEPARTMENT Cynthia Wilson Director MEMORANDUM TO: FROM: Thurston County Planning Commission Allison Osterberg, Associate Planner DATE: February 11, 2016 SUBJECT: Limits Low Impact Development (LID) Code Update Hard and Impervious Surface Coverage The county s Municipal Stormwater National Pollutant Discharge Elimination System (NPDES) permit requires widespread adoption of Low Impact Development (LID) techniques into local development codes. One objective of this review is to minimize the amount of hard and impervious surfaces in developments to allow more stormwater to infiltrate into the ground on site. This led to a review of the county s approach to limiting impervious surfaces through the zoning code. This memo and the accompanying memo on dimensional standards address proposed changes in the attached redline code. Both topics refer to changes within TCC 20, the Zoning Code for rural Thurston County. These changes will not apply to areas within the Lacey, Tumwater, or Olympia Urban Growth Areas, which are regulated under TCC 21, 22, and 23, respectively. Zoning in the county can be viewed online through Thurston GeoData Viewer: Background Impervious surfaces, by definition, are materials that prevent the infiltration of water into the soil. The most common impervious surfaces in the built environment are roads, rooftops, sidewalks, and patios. While these structures are almost 100% impervious, other features such as gravel roads, compacted soils, and even lawns are impervious to varying degrees, as they allow for less infiltration than forests and other natural ground. As development increases, so does the amount of impervious surface, which leads to changes in the way water is transported and the hydrology of a drainage basin. Stormwater runoff resulting from increased impervious surfaces affects both the quality and quantity of water entering natural water bodies in many ways. Stormwater runoff can lead to environmental impacts such as flooding, habitat loss, erosion, channel widening, and streambed alteration. Along with increased runoff comes decreased infiltration, which reduces groundwater supplies and may lead to a lowering of the water table. Ground water provides a consistent water supply to streams, wetlands, and lakes, and 2000 Lakeridge Drive SW, Olympia, Washington (360) /FAX (360) TDD (360) Website:

2 , February 11, 2016 LID Code Update Impervious Surfaces 2 decreases in ground water supply may cause a stream or wetland to dry out during months when precipitation is low. As a general rule of thumb, when impervious surfaces exceed 10% of a basin (the entire area that drains into a stream) adverse environmental impacts can be measured in the stream although impacts can occur in rural basins at impervious surface thresholds as low as 2%. Stream basins with above 25% impervious area generally have degraded water quality. Currently, within Thurston County s Zoning Code (TCC 20), some zones have impervious surface limits, while others Water Cycle Changes Associated with Urbanization only limit the extent a lot can be covered by buildings (this excludes from consideration hard surfaces such as parking lots, driveways, or patios). Impervious surfaces also are limited within the Shoreline Master Program for most shoreline lots the limit is 30% lot coverage. In addition, any development in unincorporated Thurston County that fits the criteria below requires a review by Thurston County Water Resources staff to ensure it meets runoff flow-control standards: More than 5,000 square feet new impervious surfaces Converting more than three quarters of an acre from native vegetation to lawn or landscaping Clearing of more than two-and-a-half acres of native vegetation to pasture Depending on soils and property-specific characteristics, flow-control mechanisms may be put into place to manage stormwater. The new stormwater manual requirements from Ecology address the total amount of hard surfaces on a site hard surfaces include impervious, paved areas, as well as semi-pervious areas, including permeable pavements and vegetated roofs. Analysis: Thurston County s zoning code has an inconsistent approach to addressing impervious surfaces. Where limits have been set they are typically located within sensitive basins such as McAllister Geologically Sensitive Area, and Green Cove Creek Basin, or on soil types with low infiltration rates. In other rural zoning districts there are sometimes building coverage limits and/or impervious surface limits that range as high as 60% in rural areas, or no mention of limits at all. In addition, many zones have impervious surface limits with thresholds that create arbitrary and inequitable requirements. For example, a lot in the Green Cove Basin that is 1.00 acre can have up to

3 , February 11, 2016 LID Code Update Impervious Surfaces 10,890 square feet of allowed impervious surface, while a lot that is 1.01 acres can only have 2,640 square feet. A 5-acre lot on type C soils that is zoned RRR 1/5 is allowed 21,780 square feet of impervious surfaces, but a lot that is 4.99 acres can have more than four times as much impervious 97,814 square feet. These thresholds are shown in the table below. SUMMARY OF IMPERVIOUS SURFACE THRESHOLDS BY VARIOUS ZONING DISTRICTS Lot Size 5% 6% 10% 25% 45% 60% 75% 85% Other Acres Sq. Ft. Sq. Ft. Sq. Ft. Sq. Ft. Sq. Ft. Sq. Ft. Sq. Ft. Sq. Ft. Sq. Ft. Sq. Ft , ,500 2,700 3,600 4,500 5, , ,000 2,500 4,500 6,000 7,500 8, , ,000 2,500 4,500 6,001 7,501 8, , ,000 1,667 4,167 7,500 10,000 12,500 14, , ,000 1,667 4,167 7,501 10,001 12,501 14,168 10, ,560 2,178 2,614 4,356 10,890 19,602 26,136 32,670 37,026 10, ,996 2,200 2,640 4,400 10,999 19,798 26,397 32,997 37,396 10, ,340 3,267 3,920 6,534 16,335 29,403 39,204 49,005 55,539 10, ,120 4,356 5,227 8,712 21,780 39,204 52,272 65,340 74,052 10, ,900 5,445 6,534 10,890 27,225 49,005 65,340 81,675 92,565 10, ,680 6,534 7,841 13,068 32,670 58,806 78,408 98, ,078 10, ,460 7,623 9,148 15,246 38,115 68,607 91, , ,591 10, ,240 8,712 10,454 17,424 43,560 78, , , ,104 10, ,020 9,801 11,761 19,602 49,005 88, , , ,617 10, ,364 10,868 13,042 21,736 54,341 97, , , ,760 10, ,800 10,890 13,068 21,780 54,450 98, , , , ,580 11,979 14,375 23,958 59, , , , , ,360 13,068 15,682 26,136 65, , , , , ,140 14,157 16,988 28,314 70, , , , , ,920 15,246 18,295 30,492 76, , , , , ,700 16,335 19,602 32,670 81, , , , , ,480 17,424 20,909 34,848 87, , , , , ,260 18,513 22,216 37,026 92, , , , , ,040 19,602 23,522 39,204 98, , , , , ,820 20,691 24,829 41, , , , , , ,600 21,780 26,136 43, , , , , ,260 Large Parcels traditional cluster None Green Cove Creek MGSA RRR1/5; R1/10; R 1/20 & UR 1/5 Soil types C & D RRR1/5; R1/10; R 1/20 & UR 1/5 Soil types A & B; RR1/5*; RL 1/1; RL 2/1*; RL3-6/1*; RL 4-16/1*; AC*; HC*; PI*; LI*; RRI (* lot coverage of structures) RCC NC NA LTA; LTF; PP; MR 3

4 , February 11, 2016 LID Code Update Impervious Surfaces Sixty percent is much higher than the actual impervious area used on an average developed rural residential lot. Indeed, if all new residential development occurred with such a large amount of impervious area, it would likely lead to degradation of stream health and water quality. For a related study, Thurston Regional Planning Council staff digitized the impervious area for 92 properties that contained a single residential dwelling unit built after 1995 and was considered fully developed based on zoning density. Using this sample data set, the following relationship of rural lot sizes to impervious area were developed: Acres Lot Size Square Feet Typical Zoning Density Average Percent Impervious Average Square Feet Impervious Number of Parcels in sample 0.07 to 0.2 3,000-8, to 0.9 8,700-39, units per acre 52% 3, units per acre 2 units per acre 27% 3, to ,200-78, to , , to , , to , ,400 One unit per acre One unit per 2 acres One unit per 5 acres One unit per 10 acres 15% 8, % 8, % 13, % 18, to ,400-1,742,400 One unit per 20 acres 3% 37, ac 1,742,400 plus One unit per 40 acres 1% 36,100 9 The table above shows average percent impervious area. The range is quite high depending on how long driveways are and whether the garage is attached or detached. 4

5 , February 11, 2016 LID Code Update Impervious Surfaces This 2.2 acre property contains a large home, detached garage, and driveway. The impervious area is 10 percent or 9,900 square feet. TRPC also looked at typical impervious area for non-residential uses in the county, as shown in the table below. Use Impervious Area (Rural) Agriculture 2% Forestry 0% Mining 4% Commercial 10% Church 6% School 20% Industrial 5% Parks, Open Space 1% Recommendations: Thurston County staff discussed several options related to hard and impervious surface limits and recommend developing consistent limits for all zones that use the terminology hard surfaces in order to be consistent with the requirements of the revised Drainage Design and Erosion Control Manual (DDECM). The proposed limits are based on typical use within zones. These proposed limits were discussed with a Community Stakeholder Group made up of building and development professionals, as well as other interested parties. This group requested that there be options to allow for flexibility in site design, and staff proposed the limits could be partnered with credits that 5

6 , February 11, 2016 LID Code Update Impervious Surfaces could be applied in exchange for certain desirable practices, such as additional tree retention or use of permeable pavements. The proposed changes include the following recommendations: Wherever possible, clarify definition of impervious surface and hard surface across different sections of the code to be consistent with that used in the DDECM. Use the term hard surface limits rather than impervious surface limits to be consistent with new guidance from Ecology. Develop consistent hard surface limits for all zones, except Public Parks and Preserves and Military Reservation, that do not create inequitable thresholds based on area (see table below with revised thresholds) For smaller residential and resource lots, allow for a minimum square footage allowance, such as is currently allowed in the MGSA zone. Allow preexisting hard surfaces or structures to be replaced within the existing footprint For lots greater than 2.5 acres, an additional 5% may be used for buildings related to agriculture or forestry practices. Use of pervious surfaces can be estimated at 75% of total area for calculating total hard surface area. Hard surface area limit may be increased with a special use permit. Credit Option 1: o Hard surface limits can be increased by 50% under the following conditions: 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. Up to 20% of these trees can be in a critical area or buffer. The development is a Planned Residential Development (PRD) or Planned Rural Residential Development (PRRD) o Hard surface limits can be increased by 100% in residential and resource zones under the following conditions: Landscape plan shows retention of existing native trees and vegetation on at least 65% of the site. Credit Option 2: o Receive credit for an additional 1,000 square feet of hard surfaces above the limit if landscape plan shows 6,500 square feet retention of native trees and vegetation that are outside of any designated critical areas or buffers. o Receive credit for an additional 1,000 square feet of hard surfaces above the limit if landscape plan shows 3,250 square feet retention of native trees and vegetation connecting designated critical areas or buffer. o Receive credit for an additional 1,000 square feet of hard surfaces above the limit if landscape plan shows 3,250 square feet replanting of native trees and vegetation within a riparian or wetland buffer area. 6

7 , February 11, 2016 LID Code Update Impervious Surfaces SUMMARY OF REVISED IMPERVIOUS SURFACE THRESHOLDS BY VARIOUS ZONING DISTRICTS None Green Cove Creek and Ken Lake overlay MGSA For lots 2.5 acres or larger: R 1/10*; R1/20*; RRR1/5; UR 1/5; R1/5; LTF (Same as MGSA for lots 2.5 acres or smaller) RL 1/2; RL 1/1; RL 2/1; R 3-6/1 LTA (same as MGSA for lots 2.5 acres or smaller) RCC; R 4-16/1 NC; AC; HC; PI; LI; RRI NA PP; MR 7 * For lots greater than 2.5 acres, 10% for first five acres, 5 percent for remaining area.

8 , February 11, 2016 LID Code Update Impervious Surfaces 8

9 COUNTY COMMISSIONERS Creating Solutions for Our Future Cathy Wolfe District One Sandra Romero District Two Bud Blake District Three RESOURCE STEWARDSHIP DEPARTMENT Cynthia Wilson Director MEMORANDUM TO: FROM: Thurston County Planning Commission Allison Osterberg, Associate Planner DATE: February 11, 2016 SUBJECT: Low Impact Development (LID) Code Update Dimensional Standards Zoning regulations typically include guidelines that limit the location and size of structures on a parcel these include setbacks, height limits, and minimum lot widths. These standards usually are put in place for either safety reasons or aesthetic considerations. As part of the review of codes for low impact development (LID), one objective was to ensure that standards related to scale and configuration of buildings support onsite stormwater infiltration. Front yard setbacks (which dictate how far houses and other structures must be from the street) can extend driveway lengths and increase impervious coverage of the lot. Side yard setbacks and wide frontages can increase total road length, and reduce flexibility on where buildings are placed in a site design. Building height limits can require larger building footprints for the same capacity, so raising height limits could reduce the amount of total impervious surface. Analysis - Setbacks: Thurston County requires that commercial and residential structures over 120 square feet in floor area meet minimum yard setback requirements. General setback requirements are set out in the table below, though they differ within specific zoning districts: 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-of-way of a flanking street 25 from right-of-way easement or property line; 10 from right-of-way of a flanking street b. Residential exceeding two units per structure 30 ; 10 from right-of-way of a flanking street 20 ; 10 from right-of-way of a flanking street Lakeridge Drive SW, Olympia, Washington (360) /FAX (360) TDD (360) Website:

10 , February 11, 2016 LID Code Update Dimensional Standards Building Type c. Single-family and two-family structures d. Buildings housing animals Arterial, State Highway Collector, Local and Side Rear and RR ROW Private Roads Yard Yard 30 ; 10 from right-of-way of a flanking street 20 ; 10 from right-of-way of a flanking street Open porches, decks, and stairways may project into a setback by 10 feet or 50% of the setback, whichever is less. Sills, cornices, eaves, gutters, and other ornamental features may project up to two feet into the required setback. Chimneys can extend two feet into a side setback, or three feet into a front or read setback. No portion of any structure over 30 inches above grade can be closer than two feet from a property line. Thurston County s setback standards are generally in line with rural standards in other jurisdictions, although they are larger than those in some areas. Type of Front Yard, Front Yard, Development Arterial non-arterial Side Yard Rear Yard Pierce County (18A ) Urban Rural ; (30 Ag, LTF) 0-30 ; (30 Ag, LTF) Kitsap County (17.382) Urban Residential Commercial and Mixed Use Industrial LAMIRD Rural and Resource Agricultural structures King County (21A ) Rural Residential Resource ; (100 for LTF) 10 ; (100 for LTF) Commercial Industrial Jefferson County (18.30) Resource Rural Residential Rural Commercial Rural Industrial Olympia (18.04) 2

11 , February 11, 2016 LID Code Update Dimensional Standards Type of Development Residential Front Yard, Front Yard, Arterial non-arterial Side Yard Rear Yard ; (5 for ; (5 5 (10 5 (10 Ag) Ag) flanking) flanking) Urban/Neighborhood Village Commercial Industrial Lacey (16) Residential Corridors 0 ; (max 15 ) 0 ; (max 15 ) Commercial Industrial Tumwater (18.42) Residential Commercial Industrial Tenino (106.20) Residential Rainier (18.40) MultiFam and Mixed Use Commercial Industrial Residential Commercial Industrial Some communities allow very small setbacks; as low as zero feet, particularly for commercial and industrial zones. Within the building and fire code there are some structural modifications required for buildings that are placed so close to lot lines, for example to minimize damage that could be caused if someone were to drive into a building from the street. These can increase building construction costs, so developers may opt to voluntarily set buildings back farther than required. Thurston County setbacks could be reduced, although both the LID county staff work group and Community Stakeholder Group for LID agreed that front setbacks in residential districts should still be large enough that a driveway will be long enough to park a car. This reduces the likelihood that cars parked in front of a residential building will obstruct roads or other facilities in the right-of-way. The length proposed is a minimum of 20 feet, to match the parking standard for larger vehicles. The groups indicated that setbacks could be smaller for industrial and commercial development, but thought that a zero setback would not be necessary or appropriate in a rural setting. The group felt that larger front setbacks are still warranted for busier roads, such as arterials. County plans review staff and fire officials expressed concern that reducing side setbacks too far would complicate regular maintenance of structures as well as firefighting and rescue from higher stories, if 3

12 , February 11, 2016 LID Code Update Dimensional Standards setbacks do not allow enough room to safely place and access a ladder. Members of the Community Workgroup for LID recommended having consistent side and rear setbacks of 5-feet to allow for flexibility in design of sites. The access concerns could be minimized by reducing the amount that eaves and other ornamental features can encroach into setbacks. In addition, county staff asked that the threshold at which structures trigger the setback requirement be increased from 120 to 200 square feet, in order to match the current requirement in our Building Code that only requires permits for structures exceeding 200 square feet (TCC ). Analysis Height Limits Most zones have a height limit of 35 feet, with the exception of commercial districts, which have a 40- foot limit and Light Industrial, which has a 65-foot limit. Certain structures (e.g., barns, silos, chimneys) are excluded from height limits. The 35-foot limit generally allows for a 2-to-3 story building. This is similar to height standards in other jurisdictions. Pierce County: ft for most zones; 60 ft for commercial centers; 70 ft for Urban Village Kitsap County: 35 ft for Urban residential (except multifamily), rural commercial, rural resource Snohomish County: o Resource = o Rural = 35-45; Rural Industrial = 50 o Other = o Urban = Staff considered raising height limits, particularly for Commercial or Industrial zones, however, greater height limits may not be in keeping with rural character and may not substantially change building footprints, since most development currently is able to infiltrate stormwater on site under the current building height limits. In addition, staff consulted with area fire chiefs, who raised fire safety concerns; fire trucks used in the county carry ladders that can reach 24 to 28 ft, which facilitate a rescue from a second story or (depending on grade) third story window. The only units with ladder lengths beyond these standards are the two aerial ladders operated by the Lacey and Olympia Fire Departments. These units have 105-foot aerial devices for taller building access, however, they are not typically used to respond to emergencies outside of the urban core areas. Currently, buildings that exceed 35-feet (such as those in the Light Industrial zone) must have an approved sprinkler system (TCC ). Any additions to height limits in the rural areas would need to include mandated fire escape accommodations and roof access. 4

13 , February 11, 2016 LID Code Update Dimensional Standards Recommendations: Revised Standard Front yard setbacks Arterial, State Highway Building Type and RR ROW Collector, Local and Private Roads Side Rear Yard Yard a. Commercial, industrial and other nonresidential 3520 from right-of-way easement or property line; 10 from right-of-way of a flanking street 2510 from right-of-way easement or property line; 10 from rightof-way of a flanking street b. Residential exceeding two units per structure 3025 ; 10 from right-of-way of a flanking street 20 ; 10 from right-of-way of a flanking street c. Single-family and two-family structures 3025 ; 10 from right-of-way of a flanking street 20 ; 10 from right-of-way of a flanking street d. Buildings housing animals LTA, Nisqually Agricultural District, LTF, and Agritourism Overlay: maintain larger setbacks because of agricultural/resource use RR 1/5, RRR 1/5, R 1/20, R 1/10, RL 1/2, RL 1/1, RL 2/1, R 3-6/1, R 4-16, MGSA follow revised standard front yard setbacks Would be a change for RR1/5, RL 1/2, RL 1/1, RL 2/1, R 3-6/1, R 4-16, MGSA which have had specific setback requirements for single and two-family residential these were closer to the new recommended setbacks. Shrink setbacks for industrial and some commercial zones (PI, LI, RRI, NC, RCC): front setback = 10 ft, except 20 ft on arterials Retain larger setbacks for Arterial Commercial and Highway Commercial, given the location of these zones near highway traffic Reduce length that eaves and other ornamental features may project into setbacks by one foot Amend minimum size at which a building triggers setback requirements to 200 square feet to match minimum requirement for building permit No proposed changes to height limits 5

14 Thurston County planning commission Work Session DRAFT AMENDMENTS TO CODES FOR LOW IMPACT DEVELOPMENT TCC 20 Zoning Code Impervious and Hard Surface Limits; Bulk & Dimensional Standards Note: Plain text = existing regulation Strike through = proposed deletion to existing regulations Underline = proposed addition Italic = staff comment [Staff Note: Some sections do not include proposed changes and have been included only for context.] Chapter STRUCTURE, INTERPRETATIONS AND DEFINITIONS Definitions. [Staff note: All definitions in this section will be re-numbered after new and revised definitions are inserted. Other definitions in this section will not change other than being re-numbered.] The following definitions shall be used in the interpretation and administration of this title. The definition of various terms as presented in this section does not necessarily represent the same definitions as may be found for the same terms in other chapters of the Thurston County Code. Hard surface means an impervious surface, a permeable pavement, or a vegetated roof, in contrast with vegetated permeable soils Impervious surface means pavement (e.g., compacted gravel, asphalt and concrete), roofs, revetments, or any other manmade surface which substantially impedes the infiltration of

15 precipitation.a non-vegetated surface area which either prevents or retards the entry of water into the soil mantle as under natural conditions prior to development. A non-vegetated surface area which causes water to run off the surface in greater quantities or at an increased rate of flow from the flow present under natural conditions prior to development. Common impervious surfaces include, but are not limited to, roof tops, walkways, patios, driveways, parking lots or storage areas, concrete or asphalt paving, gravel roads, packed earthen materials, and oiled, macadam or other surfaces which similarly impede the natural infiltration of stormwater. Native vegetation means vegetation or plant species, other than noxious weeds, which are indigenous to the area or habitat in question and which reasonably could have been expected to naturally occur on the site. Permeable pavement means pervious concrete, porous asphalt, permeable pavers or other forms of pervious or porous paving material intended to allow passage of water through the pavement section. It often includes an aggregate base that provides structural support and acts as a stormwater reservoir. Pervious surface means any surface material that allows stormwater to infiltrate into the ground. Examples include lawn, landscape, pasture, native vegetation areas, and permeable pavements. Chapter LOT, YARD, USE AND STRUCTURE REGULATIONS Minimum yards required for building setbacks. 1. General Requirements. Except where specifically provided in this title, all structures over one two hundred twenty square feet in floor area shall meet the following minimum yard (setback) requirements: Front Yards Building Type Arterial, State Highway and RR ROW Collector, Local and Private Roads Side Rear Yard Yard a. Commercial, industrial and other nonresidential 3520 from right-of-way easement or property line; 10 from right-of-way of a flanking street 2510 from right-of-way easement or property line; 10 from right-of-way of a flanking street b. Residential exceeding two units per structure 3025 ; 10 from right-of-way of a flanking street 20 ; 10 from right-of-way of a flanking street

16 c. Single-family and two-family structures 3025 ; 10 from right-of-way of a flanking street 20 ; 10 from right-of-way of a flanking street d. Buildings housing animals Yard Regulations for Through Lots. For through lots, minimum front yard requirements shall apply to the yard oriented to the structure s front door. The opposing yard shall be deemed to be the rear yard. 3. These provisions shall not apply in those instances where a lot has been recorded prior to the enactment of this title where the enforcement of this regulation would negate the use of the lot in accordance with the provisions of the zoning district in which it is located and an appropriate variance has been granted Hard and Impervious Surface Limits 1. General standards. In addition to the hard surface coverage limits specified in this title, the following standards shall apply: 2. Credits. a. The total area of hard surfaces does not include access easements serving neighboring property and driveways to the extent that they extend beyond the street setback due to location within an access panhandle or due to the application of requirements to locate features over which the applicant does not have control. b. Pervious surfaces may be calculated at 75 percent area for the purpose of calculating total hard surface area. c. On any lot over 2.5 acres in area, an additional 5 percent of the lot area may be used for buildings related to agricultural or forestry practices. d. Hard surfaces rendered nonconforming by the coverage limits of this title may be replaced within the existing footprint, but not expanded. e. The hard surface coverage area for any lot may be increased beyond the total amount permitted in this chapter subject to approval of a special use permit under Chapter a. Credits apply only to lots 2.5 acres or larger in the following zones: LTA, LTF, RR 1/5, RRR 1/5, R 1/10, R 1/20, UR 1/5, RL ½, RL 1/1, RL 2/1, R 3-6/1, R 4-16, MGSA. 3

17 b. Hard surface coverage limits specified in this title may be increased by 50 percent under any one of the following circumstances: i. Soils on the site allow for, and site design utilizes, full dispersion of stormwater runoff, done in accordance with the Thurston County DDECM, Chapter ii. A minimum of 30 percent of trees or native vegetation is retained on the site as shown in a landscape plan, as specified in Chapter A maximum of 20 percent of this retained vegetation may be within a critical area or critical area buffer. Retained trees shall be recorded on the final plat and in the abbreviated drainage plan. iii. The development is a Planned Residential Development (PRD), TCC 20.30, or a Planned Rural Residential Development (PRRD), TCC 20.30A. b. Hard surface coverage limits specified in this title may be increased by 100 percent under the following circumstances: i. A minimum of 65 percent of trees or native vegetation is retained on the site as shown in a landscape plan, as specified in Chapter Retained trees shall be recorded on the final plat and in the abbreviated drainage plan. c. An additional one thousand square feet of hard surface area may be permitted above the coverage limit for each six thousand five hundred square feet of retained trees and native vegetation that are outside of any designated critical area or buffer. Retained trees shall be recorded on the final plat and in the abbreviated drainage plan. d. An additional one thousand square feet of hard surface area may be permitted above the coverage limit for each three thousand two hundred fifty square feet of retained trees and native vegetation that are outside of any designated critical area or buffer, but connect them. Retained trees shall be recorded on the final plat and in the abbreviated drainage plan. e. An additional one thousand square feet of hard surface area may be permitted above the coverage limit for each three thousand two hundred fifty square feet of trees and native vegetation that are replanted within any degraded riparian habitat area, as specified in Chapter 24.35, or wetland buffer, as specified in Chapter A restoration plan must be prepared by a qualified biologist or other qualified professional, as specified in Chapter Restored areas and replanted trees shall be recorded on the final plat and in the abbreviated drainage plan. Chapter 20.08A - LONG-TERM AGRICULTURE DISTRICT (LTA) 20.08A Design standards. 4

18 The following standards are established as the minimum necessary to ensure that the purpose of this district is achieved and maintained as new lots are created and new buildings are constructed: 1. Maximum Building Height: thirty-five feet; and 2. Minimum Yard Requirements: a. Single-Family Residential. i. Front yard see Chapter 20.07; ii. Side yard fifteen feet; iii. Rear yard twenty-five feet; b. Single-family residential on lots created in accordance with the planned rural residential development chapter: see Chapter 20.30A, c. All other structures: see Chapters and Maximum Coverage by Hard Surfaces. Maximum hard surface coverage for new development in this district is as follows; also see Chapter 20.07: a. Lots 1.5 acres or greater: Fifteen percent. b. Lots less than 1.5 acres: Sixty percent or ten thousand square feet, whichever is less. Chapter 20.08C - NISQUALLY AGRICULTURAL DISTRICT (NA) 20.08C Design standards. The following standards are established as the minimum necessary to ensure that the purposes of this district are achieved and maintained as new lots are created and new buildings are constructed: 1. Minimum yard requirements shall be as follows: a. Single-Family Residential. i. Front yard see Chapter 20.07; ii. Side yard fifteen feet; iii. Rear yard twenty-five feet; b. Single-family residential on lots created in accordance with the planned rural residential development chapter, Chapter 20.30A; c. All other structures (e.g., barns, stables, etc.) are subject to Section or the standards which may be required of special uses in Chapter Maximum building height shall be thirty-five feet subject to Section Maximum lot coverage shall be as follows: 5

19 a. With single-family house, farm housing, farm structures and access roads, excluding manure holding ponds, shall not exceed five percent. b. When a clustered lot subdivision is approved pursuant to Section 20.08C.050 and Chapter 20.30A, Planned Rural Residential Development, these lots and those uses listed in subsection (1) above shall not exceed ten percent. c. Those parcels which have lot coverage exceeding these limitations will not be eligible for the purchase of development rights program Chapter 20.08D - LONG-TERM FORESTRY DISTRICT (LTF) 20.08D Design standards. 1. Maximum Building Height: thirty-five feet; 2. Minimum Yard Requirements. a. Single-Family Residential. i. Front yard varies, see Chapter 20.07; ii. Side yard fifteen feet; iii. Rear yard twenty-five feet; Note: Residences are encouraged to be located at least one hundred fifty feet from any property line abutting or within this district to better ensure land use compatibility between residential uses and adjacent long-term forestry operations; however, such setback is not required. b. Single-family residential on lots created in accordance with the planned rural residential development chapter: See Chapter 20.30A, c. All other structures: See Chapters and 20.54; 3. Where parcels of contiguous ownership total less than six hundred forty acres as of the effective date of this chapter, the parcels may be developed in accordance with the following development standards: a. Maximum residential density of one unit per twenty acres, b. All subdivisions shall be in conformance with Chapter 20.30A, Planned Rural Residential Development, except that such residential lots shall be a minimum of one acre in size and no larger than five acres in size. Where the requirements of Chapter 20.30A conflict with the requirements of this section, the more restrictive standards shall apply; 4. Legal lots from ten to acres in size, under the same ownership since August 23, 1993, may be subdivided one time into a maximum of two lots with a minimum lot size of five acres. Further division of a lot created pursuant to this subsection is prohibited. 5. Maximum Coverage by Hard Surfaces. Maximum hard surface coverage for new development in this district is as follows, also see Chapter 20.07: 6

20 a. Lots 2.5 acres or greater: Ten percent. b. Lots less than 2.5 acres: Sixty percent or ten thousand square feet, whichever is less. Chapter 20.08E - PUBLIC PARKS, TRAILS, AND PRESERVES DISTRICT (PP) 20.08E Design standards. The following standards are established as the minimum necessary to ensure that the purpose of this district is achieved and maintained: 1. Maximum building height thirty-five feet; 2. Minimum yard requirements see Section Chapter 20.08F - MILITARY RESERVATION DISTRICT (MR) 20.08F Design standards. The following standards are established as the minimum necessary to ensure that the purpose of this district is achieved and maintained: 1. Maximum building height see Chapter 20.07; 2. Minimum yard requirements see Section Chapter RURAL RESIDENTIAL ONE DWELLING UNIT PER FIVE ACRES (RR 1/5) Design standards. The following standards are established as the minimum necessary to insure that the purpose of this rural residential, one unit per five acre district is achieved and maintained as new lots are created and new buildings are constructed: 1. Minimum Lot Size: a. Conventional subdivision lot (net) four acres for single-family, eight acres for duplexes; b. Nonresidential use five acres; 2. Maximum Building Height thirty-five feet; 3. Minimum Yard Requirements: a. Single-family and two-family residential: i. Front yard twenty feet from right-of-way easement or property line and thirty feet from right-of-way easement or property line on arterials, except ten feet from rightof-way of a flanking street; 7

21 ii. Side yard six feet; iii. Rear yard ten feet; b. All other structures: See Section (required minimum yards); 4. Maximum Coverage by Hard Surfaces. Maximum hard surface coverage for new development in this district is as follows, also see Chapter 20.07: a. Lots 2.5 acres or greater: Ten percent. b. Lots less than 2.5 acres: Sixty percent or ten thousand square feet, whichever is less. Chapter 20.09A - RURAL RESIDENTIAL/RESOURCE ONE DWELLING UNIT PER FIVE ACRES (RRR 1/5) 20.09A Design standards. The following standards are established to insure that the purpose of this district is achieved and maintained as new lots are created and new buildings are constructed: 1. Subdivision Alternatives. Land within this district may only be divided as follows: a. Large lot subdivisions, or b. Subdivisions or short subdivisions in conformance with Chapter 20.30A, Planned Rural Residential Development; 2. Minimum Lot Size. The minimum lot sizes in this district are as follows: a. Large lot five acres or one-one hundred twenty-eighth of a section, b. Planned rural residential developments none, subject to applicable standards for provision of water and sewage disposal contained in Articles III and IV of the Thurston County Sanitary Code, and c. Special uses for which a minimum lot size is not established by Chapter Five acres, with the exception of fire district facilities which may be located on lots of less than five acres. 3. Maximum Building Coverage. Building coverage for fire district facilities shall be specified through the special use permit process and/or SEPA environmental review process as applicable. For all other special uses with no maximum building coverage specified in Chapter TCC, the maximum building coverage shall be six thousand square feet for parcels five to ten acres in size and twenty thousand square feet for parcels over ten acres in size. 8

22 4. Maximum Building Height. Buildings shall not exceed a height of thirty-five feet, except for structures exempted from this height requirement pursuant to Section Minimum Yard and Setback Requirements. See Chapter Impervious Maximum Surface Coverage by Hard Surfaces. Maximum impervious hard surface coverage for new development in this district is as follows, also see Chapter 20.07: a. Maximum impervious hard surface coverage, including structures, wwithin the Green Cove Creek Drainage Basin, is as follows: i. Lots up to but not including.23 less than four acres (ten twenty-two thousand nineteen six hundred fifty-one square feet) forty five percent or 10,000 square feet, whichever is less. ii. Lots.23 four acres to one acre or more twenty-five percent. Six percent iii. Lots 1.01 acres or more six percent. Where only a portion of a parcel is located within the basin, the impervious hard surface limits are applied to that portion of the parcel only. For example, if two acres of a five-acre parcel lie within the basin, then up to six percent 10,000 square feet of the two-acre portion may be covered with impervious hard surfaces. The provisions of the Drainage Design and Erosion Control Manual (Chapter TCC) may further limit the amount of impervious hard surfaces. b. For all other subdivisions, large lot subdivisions, short plats and new construction: i. Lots 2.5 acres or greater: Ten percent. ii. Lots less than 2.5 acres: Sixty percent or ten thousand square feet, whichever is less. on lots five or more acres in size that are primarily (i.e., more than fifty-one percent) on hydrologic soil groups C or D, as defined in the Thurston County Drainage Design and Erosion Control Manual (Chapter of this code) ten percent, except as provided in subsection (6)(a) of this section; c. For subdivisions, large lot subdivisions, short plats and new construction on lots less than five acres in size that are primarily (i.e., more than fifty-one percent) located on hydrologic soil groups C or D, as defined in the Thurston County Drainage Design and Erosion Control Manual (Chapter of this code) forty-five percent, except as provided in subsection (6)(a) of this section; and d. For all other subdivisions, large lot subdivisions, short plats and new construction sixty percent. 9

23 Chapter 20.09B - RURAL ONE DWELLING UNIT PER TWENTY ACRES (R 1/20) 20.09B Lot size and design standards. All divisions of land, construction of structures, and other development in this district shall comply with the following standards: 1. Subdivision Alternatives. Land within this district may only be divided as follows: a. Large lot subdivisions, or b. Subdivisions or short subdivisions in conformance with Chapter 20.30A, Planned Rural Residential Development. 2. Minimum Lot Size. Minimum lot sizes in this district are as follows: a. Large lot twenty acres, or 1/32 of a section; b. Planned Rural Residential Developments none, subject to applicable standards for provision of water and sewage disposal contained in Articles III and IV of the Thurston County Sanitary Code, and the standards of Chapter 20.30A, Planned Rural Residential Development; and c. Special uses for which a minimum lot size is not established by Chapter Five acres, with the exception of fire district facilities which may be located on lots of less than fiveacres. 3. Maximum Building Coverage. Building coverage for fire district facilities shall be specified through the special use permit process and/or SEPA environmental review process as applicable. For all other special uses with no maximum building coverage specified in Chapter TCC, the maximum building coverage shall be six thousand square feet for parcels five to ten acres in size and twenty thousand square feet for parcels over ten acres in size. 4. Maximum Building Height. Building heights in this district shall not exceed thirty-five feet, except for structures exempted from this height requirement pursuant to Section Minimum Yard and Setback Requirements. See Chapter Maximum Coverage by Hard Surfaces. Maximum hard surface coverage for new development in this district is as follows, also see Chapter 20.07: a. Lots 2.5 acres or greater: Ten percent for the first five acres; five percent for remaining area. [Staff note: For example, a 20-acre parcel would have 21,780 square feet (10% of 5 acres) plus 32,670 square feet (5% of 15 acres), for a total hard surface limit of 54,450 square feet.] b. Lots less than 2.5 acres: Sixty percent or ten thousand square feet, whichever is less. Chapter 20.09C - RURAL ONE DWELLING UNIT PER TEN ACRES (R 1/10) 20.09C Lot size and design standards. 10

24 All divisions of land, construction of structures, and other development in this district shall comply with the following standards: 1. Subdivision Alternatives. Land within this district may only be divided as follows: a. Large lot subdivisions, or b. Subdivisions or short subdivisions in conformance with Chapter 20.30A, Planned Rural Residential Development. 2. Minimum Lot Size. The minimum lot sizes in this district are as follows: a. Large lot subdivision ten acres, or 1/64 of a section; b. Planned Rural Residential Developments none, subject to applicable standards for provision of water and sewage disposal contained in Articles III and IV of the Thurston County Sanitary Code, and the standards of Chapter 20.30A, Planned Rural Residential Development; and c. Special uses for which a minimum lot size is not established by Chapter Five acres, with the exception of fire district facilities which may be located on lots of less than fiveacres. 3. Maximum Building Coverage. Building coverage for fire district facilities shall be specified through the special use permit process and/or SEPA environmental review process as applicable. For all other special uses with no maximum building coverage specified in Chapter TCC, the maximum building coverage shall be six thousand square feet for parcels five to ten acres in size and twenty thousand square feet for parcels over ten acres in size. 4. Maximum Building Height. Building heights shall not exceed thirty-five feet, except for structures exempted from this height requirement pursuant to Section Minimum Yard and Setback Requirements. See Chapter Impervious Surface Maximum Coverage by Hard Surfaces. Maximum impervious surface coverage for new development in this district is as follows, also see Chapter 20.07: a. Lots 2.5 acres or greater: Ten percent for the first five acres; five percent for remaining area. [Staff note: For example, a 20-acre parcel would have 21,780 square feet (10% of 5 acres) plus 32,670 square feet (5% of 15 acres), for a total hard surface limit of 54,450 square feet.] b. Lots less than 2.5 acres: Sixty percent or ten thousand square feet, whichever is less. a. For subdivisions, large lot subdivisions, short plats and new construction on lots five or more acres in size that are located primarily (i.e., more than fifty-one percent) on hydrologic soil groups C or D, as defined in the Thurston County Drainage Design and Erosion Control Manual (Chapter of this code) ten percent; b. For subdivisions, large lot subdivisions, short plats and new construction on lots less than five acres in size that are located primarily (i.e., more than fifty-one percent) on hydrologic soil 11

25 groups C or D, as defined in the Thurston County Drainage Design and Erosion Control Manual (Chapter of this code) forty-five percent; and c. For all other subdivisions, large lot subdivisions, short plats and new construction sixty percent. Chapter 20.09D - URBAN RESERVE ONE DWELLING UNIT PER FIVE ACRES (UR 1/5) 20.09D Lot size and design standards. The following standards are established to insure that the purposes of this district are achieved and maintained as lots are created and buildings are constructed: 1. Subdivision Alternatives. Land within this district may only be divided as follows: a. Large lot subdivisions, or b. b. Subdivisions or short subdivisions in conformance with Chapter 20.30A, Planned Rural Residential Development. 2. Minimum Lot Size. The minimum lot sizes in this district are as follows: a. Large lot subdivision five acres; b. Planned Rural Residential Developments none, subject to applicable standards for provision of water and sewage disposal contained in Articles III and IV of the Thurston County Sanitary Code, and the standards of Chapter 20.30A, Planned Rural Residential Development; and c. Special uses for which a minimum lot size is not established by Chapter five acres, with the exception of fire district facilities which may be located on lots of less than five-acres. 3. Maximum Building Coverage. Building coverage for fire district facilities shall be specified through the special use permit process and/or SEPA environmental review process as applicable. For all other special uses with no maximum building coverage specified in chapter TCC, the maximum building coverage shall be six thousand square feet for parcels five to ten acres in size and twenty thousand square feet for parcels over ten acres in size. 4. Maximum Building Height. Buildings shall not exceed a height of thirty-five feet, except for structures exempted from this height requirement pursuant to Section Minimum Yard and Setback Requirements. See Chapter Impervious Surface Maximum Coverage by Hard Surfaces. Maximum hard surface coverage for new development in this district is as follows, also see Chapter 20.07: a. Lots 2.5 acres or greater: Ten percent. b. Lots less than 2.5 acres: Sixty percent or ten thousand square feet, whichever is less. 12

26 Subdivisions, large lot subdivisions, short plats and new construction on lots five or more acres in size that are located primarily (i.e., more than fifty-one percent) on hydrologic soil groups C or D, as defined in the Thurston County Drainage Design and Erosion Control Manual (Chapter of this code), ten percent; a. For subdivisions, large lot subdivisions, short plats and new construction on lots less than five acres in size that are located primarily (i.e., more than fifty-one percent) on hydrologic soil groups C or D, as defined in the Thurston County Drainage Design and Erosion Control Manual (Chapter of this code) forty-five percent; and b. For all other subdivisions, large lot subdivisions, short plats and new construction sixty percent. Chapter 20.10A - RESIDENTIAL LAMIRD ONE DWELLING UNIT PER TWO ACRES (RL 1/2) 20.10A Design standards. The following standards are established as the minimum necessary to ensure that the purpose of this rural residential, one dwelling unit per two acre district is achieved and maintained as new lots are created and new buildings are constructed: 1. Minimum lot size: a. Conventional subdivision lot (net) one and one-half acres for single-family, three acres for duplexes; b. Cluster subdivision lot one acre for single-family, two acres for duplexes, subject to applicable standards for provision of water and sewage disposal contained in Articles III and IV of the Thurston County Sanitary Code; and c. Nonresidential use two acres. 2. Maximum building height thirty-five feet. 3. Minimum yard requirements: a. Single-family and two-family residential: i. Front yard twenty feet from right-of-way easement or property line and thirty feet from right-of-way easement or property line on arterials, except ten feet from right-of-way of a flanking street; ii. Side yard six feet; and iii. Rear yard ten feet. b. Other uses: See Section (required minimum yards). 13