The goal of low impact development is to conserve and use existing natural site features, to integrate distributed, small-scale stormwater controls, and to prevent measurable harm to streams, lakes, wetlands, and other natural aquatic systems from commercial, residential, or industrial development sites by maintaining a more hydrologically functional landscape. The purpose of this chapter is to establish the requirements for low impact development projects. As part of meeting these purposes and goals, this chapter is intended to fulfill the following purposes:

(1)

Manage stormwater through a land development strategy that emphasizes conservation and use of on-site natural features integrated with engineered, small-scale hydrologic controls to more closely mimic predevelopment hydrologic conditions;

(2)

Encourage creative and coordinated site planning, the conservation of natural conditions and features, the use of appropriate new technologies and techniques, and the efficient layout of streets, utility networks and other public improvements;

(3)

Minimize impervious surfaces and effective impervious surfaces;

(4)

Encourage the creation or preservation of permanent forested open space;

(5)

Encourage development of residential environments that are harmonious with on-site and off-site natural and built environments;

(6)

Further the goals and the implementation of the policies of the comprehensive land use plan.

(Ord. 76-08 Attach. A (part), 2008).

(Ord. No. 23-19, Att. A, 3-19-2019)

This chapter shall apply to all new development in all zones within the Allyn and Belfair urban growth areas. These standards shall not apply to the construction of a single-family unit on a legal lot of record. These standards are in addition to other development regulations. If there are any conflicts between this chapter and other development regulations, the provisions of this chapter shall apply.

(Ord. 76-08 Attach. A (part), 2008).

Stormwater facilities shall be designed in accordance with the 2012 Stormwater Management Manual for Western Washington, as amended in 2014 and hereafter, consistent with the Mason County Shoreline Master Program (MCC 8.52). The thresholds, definitions, minimum requirements and exceptions, adjustment and variance criteria found in the NPDES Phase II Municipal Stormwater Permit. and including the mandatory incorporated provisions of the Stormwater Management Manual are included.

(Ord. 76-08 Attach. A (part), 2008).

(Ord. No. 23-19, Att. A, 3-19-2019)

Uses allowed in a low impact development shall include permitted, accessory and conditional uses allowed in and subject to the conditions of the underlying zone district(s).

(Ord. 76-08 Attach. A (part), 2008).

All uses and development shall conform to all relevant requirements and standards of:

(1)

The zone district(s) within which the low impact development is located, except as may be modified by this chapter;

(2)

The International Building and Fire Codes;

(3)

Title 14 MCC where it does not conflict with the standards and requirements of this chapter;

(4)

All applicable density requirements of the Mason County Development Regulations; and

(5)

Other applicable official controls.

(Ord. 76-08 Attach. A (part), 2008).

(a)

The location of all streets, buildings, parking areas, pedestrian, bicycle and vehicular ways, and utility easements shall be designed to promote public safety, compatibility of uses, minimize effective impervious surface, preserve forested open space, and complement predevelopment site characteristics such as topography, soils, hydrology, and other natural features.

(b)

Low impact development projects shall record an easement or covenant against the land title to ensure that the low impact development features are protected and maintained.

(Ord. 76-08 Attach. A (part), 2008).

(a)

For the purposes of calculating required area, inundated lands shall not be included; however, other sensitive areas and their buffers may be included within the native vegetation area boundaries. Land below an ordinary high water mark shall not be counted towards the required native vegetation.

(b)

Native vegetation areas shall be forested or reforested.

(1)

Native vegetation areas that do not contain sufficient tree canopy coverage shall be planted with native or near native trees with a minimum of one native tree for every six hundred square feet to be replanted. Each tree meeting the minimum replanting size standards of Section 17.80.080(2)(C) shall be counted once, regardless of size. This requirement does not apply to wetlands or delineated wetland buffers.

(2)

Native vegetation areas shall be planted with vegetation that is indigenous to the Pacific Northwest or suitable for the Pacific Northwest climate.

(3)

Reforested areas shall be replanted with trees of two inches caliper or greater. A minimum of twenty-five percent replanted trees shall be of deciduous species and a minimum of twenty-five percent replanted trees shall be coniferous species.

(c)

Existing native vegetation, forest litter and understory shall be preserved to the extent possible in the native vegetation areas in order to reduce flow velocities and encourage sheet flow on the site. Native vegetation areas that do not contain sufficient native vegetation, forest litter and understory shall be replanted.

(d)

Development within native vegetation areas shall be limited to stormwater dispersion facilities, pervious pedestrian trails, and approved surface water restoration projects. Activities within the native vegetation areas shall be limited to passive recreation, removal of invasive species, amendment of disturbed soils consistent with all applicable regulations, and planting of native vegetation. Development shall be consistent with critical areas requirements and restrictions in Chapter 17.01 MCC.

(e)

A permanent protective mechanism shall be legally established to ensure that the required native vegetation area is preserved and protected in perpetuity in a form that is acceptable to both the applicant and the county and filed with the county auditor's office. A permanent native vegetation area shall be established using one of the following mechanisms.

(1)

Placement in a separate non-building tract owned in common by all lots within the subdivision;

(2)

Covered by a protective easement or public or private land trust dedication;

(3)

Preserved through an appropriate permanent protective mechanism that provides the same level of permanent protection as subsection (e)(1) of this section as determined by the approval authority.

(f)

Restrictions on the future use of the native vegetation area shall be recorded on the face of the final plat, short plat or large lot subdivision.

(Ord. 76-08 Attach. A (part), 2008).

The duff layer and native topsoil should be retained in an undisturbed state to the maximum extent practicable. In any areas requiring grading, remove and stockpile the duff layer and topsoil on site in a designated, controlled area, not adjacent to public resources and critical areas, to be reapplied to other portions of the site where feasible.

(1)

Soil Quality. All areas subject to clearing and grading that have not been covered by impervious surface, incorporated into a drainage facility or engineered as structural fill or slope shall, at project completion, demonstrate the following:

(A)

A topsoil layer with a minimum organic matter content of ten percent dry weight in planting beds, and five percent organic matter content in turf areas, and a pH from 6.0 to 8.0 or matching the pH of the original undisturbed soil. The topsoil layer shall have a minimum depth of eight inches except where tree roots limit the depth of incorporation of amendments needed to meet the criteria. Subsoils below the topsoil layer should be scarified at least four inches with some incorporation of the upper material to avoid stratified layers, where feasible.

(B)

Planting beds must be mulched with two inches of organic material.

(C)

Quality of compost and other materials used to meet the organic content requirements:

(i)

The organic content for "pre-approved" amendment rates can be met only using compost that meets the definition of "composted materials" in WAC 173-350-220.

(ii)

The compost must also have an organic matter content of thirty-five percent to sixty-five percent, and a carbon to nitrogen ratio below twenty-five to one. The carbon to nitrogen ratio may be as high as thirty-five to one for plantings composed entirely of plants native to the Puget Sound lowlands region.

(iii)

Calculated amendment rates may be met through use of composted materials as defined above; or other organic materials amended to meet the carbon to nitrogen ratio requirements, and meeting the contaminant standards of Grade A Compost. The resulting soil should be conducive to the type of vegetation to be established.

(2)

Implementation Options. The soil quality design guidelines listed above can be met by using one of the methods listed below:

(A)

Leave undisturbed native vegetation and soil, and protect from compaction during construction.

(B)

Amend existing site topsoil or subsoil either at default "pre-approved" rates, or at custom calculated rates based on specifiers tests of the soil and amendment.

(C)

Stockpile existing topsoil during grading, and replace it prior to planting. Stockpiled topsoil must also be amended if needed to meet the organic matter or depth requirements, either at a default "pre-approved" rate or at a custom calculated rate.

(D)

Import topsoil mix of sufficient organic content and depth to meet the requirements. More than one method may be used on different portions of the same site. Soil that already meets the depth and organic matter quality standards, and is not compacted, does not need to be amended.

(Ord. 76-08 Attach. A (part), 2008).

(a)

To achieve the goals of low impact development, residential lots shall be clustered within the designated development area of the site. Clustering is intended to preserve open space, reduce total impervious surface area, and minimize development impacts on critical areas and associated buffers (Chapter 17.01 MCC). Preservation of open space reduces potential stormwater runoff and associated impacts and provides area for dispersion, filtration and infiltration of stormwater.

(b)

The arrangement of clustered building lots shall be designed to avoid development forms commonly known as linear, straight-line or highway strip patterns.

(Ord. 76-08 Attach. A (part), 2008).

Base densities shall be consistent with the underlying zoning. The total residential density allowed may not exceed the allowed maximum residential density within the development area, pursuant to Mason County Development Regulations Section 1.03.032.

(Ord. 76-08 Attach. A (part), 2008).

(a)

Lot Size. Design objective: minimize area of site disturbance. The minimum lot size of the underlying zone district may be reduced to achieve the purposes in Section 17.80.010 MCC.

(b)

Lot Width. Design objective: minimize street length. The minimum lot width of the underlying zone district may be reduced to achieve the purposes in Section 17.80.010 MCC.

(c)

Building Setbacks. Design objective: minimize impervious surfaces. The setbacks of the zone may be reduced to achieve the purposes in Section 17.80.010 MCC.

(Ord. 76-08 Attach. A (part), 2008).

Circulation and access provisions shall be appropriate to the scale of the project and to anticipated traffic characteristics, and consistent with the requirements of the county road standards. Deviations from these standards may be granted where a bioretention swale with compost amended soils shall be provided within the right-of-way or easement dedicated to Mason County adjacent to the public right-of-way or in islands created by loop roadways.

(Ord. 76-08 Attach. A (part), 2008).

Parking shall conform to the requirements of the overlaying urban growth area under Title 17 MCC.

(Ord. 76-08 Attach. A (part), 2008).

Alternative surfacing including, but not limited to: paving blocks, turf block, pervious concrete, porous asphalt, and other similar approved materials are encouraged. Alternative surfacing methods may be approved for parking areas, emergency parking areas, private roads, fire lanes, road shoulders, bike paths, walkways, patios, driveways, and easement service roads unless site constraints make use of such materials detrimental to water quality. Utilization of alternative surfacing methods shall be subject to review and approval by the county public works department and fire marshal for compliance with other applicable regulations and development standards. Many alternative surfaces are eligible for flow control credit per the requirements of the LID Technical Guidance Manual, current edition.

(Ord. 76-08 Attach. A (part), 2008).

(a)

Land alteration may commence when in compliance with Mason County site development regulations.

(b)

Drainage plans and improvements shall be in compliance with Mason County drainage standards. Alternative BMPs not specifically referenced in the Mason County standards may be considered subject to approval by the public works department and compliance with Department of Ecology standards.

(Ord. 76-08 Attach. A (part), 2008).

Low impact development site design is intended to complement the predevelopment conditions on the site. The development context shall be established by an initial site assessment consistent with the requirements of this section. The initial inventory and assessment process will provide the baseline information necessary to design strategies that preserve natural resources, preserve areas most appropriate to evaporate, transpire, and infiltrate stormwater, and achieve the goal of maintaining pre-development natural hydrologic conditions on the site. The assessment will result in a series of maps identifying streams, lakes, wetlands, and buffers; steep slopes, and other hazard areas; significant wildlife habitat areas; and permeable soils offering the best available infiltration potential. Maps can be combined as hard copies or as GIS layers to delineate the best areas to direct development. Designated development areas, which will contain all impervious surfaces and landscaped areas on the site, should be configured to minimize soil and vegetation disturbance, buffer critical areas, and take advantage of a site's natural stormwater processing capabilities. Designated development area boundaries shall be delineated on site plans and identified on the site during site preparation and construction. Areas outside of the designated development area envelope shall be designated native vegetation areas or reserve areas.

The site assessment shall be a component of the project submittal. The site assessment shall include, at a minimum, the following:

(1)

A survey prepared by a registered land surveyor or registered civil engineer showing existing public and private development, including utility infrastructure, on and adjacent to the site, major and minor hydrologic features, including seeps, springs, closed depression areas, drainage swales, and contours as follows:

(A)

Up to ten percent slopes, two-foot contours.

(B)

Over ten percent to less than twenty percent slopes, five-foot contours.

(C)

Twenty percent or greater slopes, ten-foot contours.

(D)

Spot elevations shall be at twenty-five foot intervals.

(2)

Location of all existing lot lines, lease areas and easements, and the location of all proposed lot lines, lease areas, and easements.

(3)

A soils report prepared by a licensed geotechnical engineer or licensed engineering geologist. The report shall identify:

(A)

Underlying soils on the site utilizing soil pits and soil grain analysis to assess infiltration capability on site. The frequency and distribution of soil pits shall be adequate to direct placement of the roads and structures away from soils that can most effectively infiltrate stormwater.

(B)

Topologic features that may act as natural stormwater storage or conveyance and underlying soils that provide opportunities for storage and partial infiltration.

(C)

Depth to groundwater.

(D)

Geologic hazard areas and associated buffer requirements as defined in Section 17.01.100 MCC.

(4)

A survey of existing native vegetation cover by a licensed landscape architect, arborist, qualified biologist identifying any forest areas on the site, species and condition of ground cover and shrub layer, and tree species, and canopy cover.

(5)

A survey of wildlife habitat by a qualified biologist.

(6)

A streams, wetland, and water body survey and classification report by a qualified biologist showing wetland and buffer boundaries consistent with the requirements of Section 17.01.070 MCC, if present.

(7)

Flood hazard areas on or adjacent to the site, if present.

(8)

Aquifer and wellhead protection areas on or adjacent to the site, if present.

(9)

Any known historic, archaeological, and cultural features located on or adjacent to the site, if present.

(Ord. 76-08 Attach. A (part), 2008).

The applicant must respond to each of the items below but the response may include estimates or approximations where exact figures are not known at the time of submittal. All estimates should be based on the applicant's best knowledge and intent of the proposal. When estimates or approximations are used they must be identified as such. The applicant should be aware that any estimates or approximations provided may be used to set development conditions or thresholds.

(1)

Title report (issued no more than thirty days prior to formal application) for all land located within the boundaries of the proposed LID project. The title report shall show all persons having an ownership interest in the property included in the LID project and a legal description that describes the exterior boundary of the LID project and lists all encumbrances affecting land within the LID project.

(2)

A statement that confirms the ownership or control of the land within the boundaries of the proposed LID project and the nature of the applicant's interest in the same and the owners. If the development area has multiple owners, then all owners of record shall consented in writing to the LID project review process.

(4)

Description of the proposed LID project including:

(A)

Project narrative showing how the project fulfills the overall goals and each purpose statement in Section 17.80.010;

(B)

Total gross area of the site;

(C)

Total area of reserve area;

(D)

Total project area (total gross site area minus total reserve area);

(E)

Total area of designated development area;

(F)

Total area of native vegetation area;

(G)

Total units proposed;

(H)

Proposed number of dwelling units by type;

(I)

Conventional impervious surface assumptions used for pond reduction calculations;

(J)

Maximum impervious surface proposed for each lot;

(K)

Lot sizes and dimensions;

(L)

Total area of impervious surfacing;

(M)

Proposed ownership of land areas within the LID project both during and after construction;

(N)

Gross density of dwelling units;

(O)

Requested dimensional modifications;

(P)

Development schedule indicating the approximate date when construction of the LID project or stages of the LID project can be expected to begin and be completed.

(5)

Copy of all existing deeds, restrictive covenants, or other legal restrictions which apply to the project site. The applicant may submit a copy of any proposed restrictive covenants that have been drafted.

(6)

The names and addresses of all property owners within three hundred feet of the site taken from the latest equalized tax roles.

(7)

Preliminary drainage report as described in the Mason County site development standards. The report should clearly state the assumed conventional storage volume and LID storage volume in the introduction.

(Ord. 76-08 Attach. A (part), 2008).

An initial site plan and any supporting graphics, narrative descriptions and maps to show existing conditions and major details of the proposed LID project. The initial site plan and supporting graphics and maps in combination shall provide a level of detail appropriate to the scale of the project and sufficient to demonstrate how the project complies with the provisions of this chapter.

(1)

Proposed name of the development, north point, scale, date and address, and telephone number of the preparer of the site plan/supporting maps.

(2)

All information included in the site assessment in Section 17.80.170 MCC, should be provided at a legible scale appropriate to the area covered by the proposal at the discretion of the administrator.

(3)

Designated development areas.

(4)

Native vegetation areas.

(5)

Reserve areas.

(6)

Areas of disturbed soils to be amended.

(7)

The existing and proposed circulation system of arterial, collector and/or local streets, including right-of-way street widths, off-street parking areas, and major points of access to public rights-of-way (including major point of ingress and egress to the development). Notations of proposed ownership, public or private, shall be included where appropriate.

(8)

Location and width of existing and proposed sidewalks and trails.

(9)

Proposed lots and dimensions.

(10)

For residential structures, provide the types and number of residential units in each structure or the range of residential structures proposed together with the range of the type and number of units per structure.

(11)

For nonresidential buildings, the gross floor area of each building.

(12)

The location and square footage or approximate location and square footage or acreage of all areas of all areas to be conveyed, dedicated or reserved as common open spaces, public parks, recreational areas, school sites, and similar public and semi-public uses with notations of proposed ownership included where appropriate.

(13)

Landscaping and open space improvements plan or concept.

(14)

The proposed treatment of the perimeter of the LID project, including materials and techniques used such as screens, fences and walls.

(15)

The location of existing and proposed utilities including sanitary sewers, water lines and storm drainage facilities intended to serve the development.

(16)

Existing zoning and comprehensive plan boundaries for the site and adjacent property.

(17)

Information of contiguous properties within three hundred feet of the proposed LID project including:

(A)

Existing and, if known, proposed land use and streets; and

(B)

Existing structures excluding accessory buildings, ownership, tracts and unique natural features of the landscape, if readily accessible.

(18)

A vicinity map showing the location of the site and its relationship to surrounding areas, including existing streets, major physiographic and cultural features such as railroads, lakes, streams, shorelines, schools, parks or other prominent features.

(19)

Landscape plan including a tree planting plan for native vegetation areas.

(Ord. 76-08 Attach. A (part), 2008).

(a)

The owner is responsible for properly maintaining the LID stormwater management facilities to minimize the risk of failure, and to accomplish this purpose, shall:

(1)

Obtain approval from Mason County public works before altering the LID stormwater management facility;

(2)

Assure a complete initial evaluation of the system components and/or property by a licensed civil engineer to determine functionality, maintenance needs and compliance with this chapter and any permits. An engineer's report shall be completed at the time of evaluations and submitted to Mason County public works.

(3)

Complete and submit annual evaluations of the LID stormwater management facilities to the Mason County public works department unless more frequent inspections are required.

(4)

Provide maintenance and needed repairs to promptly return the system to a proper operating condition;

(5)

Protect the LID stormwater management facilities from:

(i)

Cover by structures or impervious material;

(ii)

Soil compaction, for example by vehicular traffic or livestock; and

(iii)

Damage by soil removal and grade alteration.

(6)

At the time of property transfer, provide to the buyer, a copy of the maintenance and reporting requirements on file with the Mason County public works department, and any available maintenance records, in addition to the completed seller disclosure statement in accordance with Chapter 64.06 RCW for residential real property transfers.

(Ord. 76-08 Attach. A (part), 2008).

(a)

The public works director shall enforce the provisions of this chapter and may refer cases within their jurisdiction to the prosecutor's office.

(b)

When a person violates the provisions under this chapter, the public works director, or prosecutor's office, may initiate enforcement or disciplinary actions, or any other legal proceeding authorized by law, including but not limited to any one or a combination of the following:

(1)

Informal administrative conferences, convened at the request of the public works director or owner, to explore facts and resolve problems;

(2)

Orders directed to the owner of the LID stormwater management facilities and/or person causing or responsible for the violation of the rules of this chapter;

(3)

Denial, suspension, modification, or revocation of permits, approvals, or certification; and

(4)

Civil action or criminal action.

(c)

Orders authorized under this section include the following:

(1)

Orders requiring corrective measures necessary to effect compliance with this chapter which may include a compliance schedule; and

(2)

Orders to stop work until all permits, certifications, and approvals required by rule or statute are obtained.

(d)

Enforcement orders issued under this section shall:

(1)

Be in writing;

(2)

Name the person or persons to whom the order is directed;

(3)

Briefly describe each action or inaction constituting a violation of the rules of this chapter;

(4)

Specify any required corrective action, if applicable;

(5)

Specify the effective date of the order and a period of thirty days for correction of the violation;

(6)

Provide notice of the consequences of failure to comply or repeated violation, as appropriate. Such notices may include a statement that continued or repeated violation may subject the violator to:

(i)

Denial, suspension, or revocation of a permit approval, or certification if violations are not corrected within ninety days, and/or

(ii)

Referral to the office of the county prosecutor, and/or

(iii)

Other appropriate remedies;

(7)

Provide the name, business address, and phone number of an appropriate staff person who may be contacted regarding an order.

(e)

Enforcement orders shall be personally served, certified mail, or in a manner showing proof of receipt.

(f)

The public works director shall have the right of entry to inspect any LID stormwater management facility. Should any person refuse to allow the public works director to enter onto property for the purpose of enforcing these rules and regulations, the public works director may, with the assistance of the prosecuting attorney, present an affidavit, naming the person so refusing, the property involved and the reason entry is necessary, to the Mason County district court, from which an authorizing warrant may issue.

(Ord. 76-08 Attach. A (part), 2008).