Sussex County, DE Article III Design Requirements and Standards

§ 99-15 General requirements and restrictions.

A. The subdivision plat shall take into account proposals of the adopted Comprehensive Plan as appropriate in the area of proposed development and should relate to existing and proposed adjoining land uses.

B. The subdivision layout shall conform to the provisions of the zoning districts in which it is located and the provisions of the Zoning Ordinance.[1]

[1] Editor's Note: See Ch. 115, Zoning.

C. The subdivision layout shall conform with the principles and standards contained in this chapter.

D. A tract shall be subdivided so that no remnants or landlocked spaces without access are created.

E. Strip development of all types should be limited and avoided as leading to undesirable consequences relative to future development of interior parcels and compromise of the traffic integrity of the roads involved.

F. All major commercial and industrial development or subdivision along the major arterial roadways of Sussex County shall be prohibited unless the major commercial and industrial development shall provide service roads adjacent to all major arterial roadways.

[Added 6-11-1991 by Ord. No. 768]

§ 99-16 Suitability of land; preservation of natural features.

A. Land which is unsuitable for subdivision or development due to flooding, improper drainage, steep slopes, adverse earth formations or topography, utility easements or other features which will be reasonably harmful to the safety, health and general welfare of the present or future inhabitants of the subdivision and/or its surrounding areas shall not be subdivided or developed unless adequate methods are formulated by the developer and approved by the County Engineer and where applicable to the rules and regulations of the State Department of Natural Resources and Environmental Control to solve problems created by the unsuitable land conditions. Such lands shall be set aside for uses as shall not involve such a danger.

B. Cut or fill should be limited to those instances where it is required to achieve acceptable street grades, parking areas or building sites or where it will be used to enhance the site, such as by berms or swales which add visual interest or perform a useful function, such as screening or drainage.

C. Subdivision planning should take into consideration critical areas, waterways, natural topography, vegetation and especially historic spots, landmarks and social impacts.

D. It is the intent of the County to stress the preservation of all agricultural lands which are feasible and worthwhile of such preservation in order to conserve such natural amenities. Where residential subdivisions are established adjacent to lands used for agricultural purposes, the subdivider shall ensure that there shall be no negative effect on the agricultural uses. The twenty-foot wide forested and/or landscaped buffer strip required by § 99-5 shall be provided along the outer perimeter of any boundary of a residential major subdivision or development of four or more lots that is adjacent to agricultural farmland. "Agricultural purposes" shall be defined as those uses identified in Chapter 115, Zoning, Article IV, § 115-20, Subsection B(1), (2), (3), (4) and (5).

[Amended 6-15-1993 by Ord. No. 893; 7-29-2008 by Ord. No. 1984]

(1) (Reserved)[1]

[1] Editor's Note: Former Subsection D(1), regarding a space for the signature of an authorized representative of the Sussex Conservation District, as amended, was repealed 6-26-2012 by Ord. No. 2271. See § 99-26A(18).

§ 99-17 Street layout.

A. The street layout shall be designed to create desirable building sizes while respecting existing topography, minimizing street grades and avoiding excessive cuts and fills to the maximum extent possible.

B. The access to the subdivision shall be from a public highway having a width of at least 50 feet, and the number and location of access streets shall be controlled for traffic safety and protection of surrounding properties.

C. Streets shall be laid out to intersect one another at as near right angles as topography and the limiting factors of good design will permit.

D. Proposed collector streets in the subdivision shall provide for the continuation of existing, planned or platted streets on adjacent tracts unless such continuation shall be prevented by topography or other physical condition or unless such extension is found by the Commission to be unnecessary for the coordination of development between the subdivision and such adjacent tracts. When deemed advisable, the Commission may restrict access to proposed collector streets from abutting properties.

E. Where the Commission deems it desirable or necessary to provide access to adjacent tracts not presently subdivided, proposed collector streets in the subdivision shall be extended to the boundary lines with such adjacent tracts, and temporary turnarounds shall be provided within the subdivision at the ends of such streets, by means of temporary easements or otherwise.

F. Where the subdivision abuts a street as designated on the General Highway Map, the Commission may require that measures be taken to reduce the impact of heavy traffic on the residential and commercial lots abutting or fronting upon such street and to afford separation of through and local traffic by one of the following means:

(1) By providing vehicular access to such lots by means of a service drive separated from the street by a planting strip and connecting therewith at infrequent intervals. The Commission may establish a minimum width for the planting strip.

(2) By designing reverse-frontage lots having access only from a parallel internal street or from cul-de-sac or loop streets and with vehicular access to such lots from the street prohibited by deed restrictions or other means.

G. Cul-de-sac streets should not exceed 1,000 feet in length.

[Amended 11-26-1991 by Ord. No. 805]

H. Fire lanes shall be provided in all areas deemed necessary by the State Fire Marshal's office.

I. The access to major commercial and industrial development or subdivision along major arterial roadways shall have but one entrance to the major arterial roadway, and the plan of subdivision shall provide inner roads, or new service drives for each of the parcels created by the subdivision to have access to the major arterial roadway. The inner roads or service drives shall meet the layout requirements established by this section.

[Added 6-11-1991 by Ord. No. 768]

§ 99-18 Street design standards.

[Amended 10-12-1999 by Ord. No. 1345; 6-26-2012 by Ord. No. 2268; 3-28-2017 by Ord. No. 2489]

A. Construction plans shall be prepared by a registered Delaware professional engineer or a licensed Delaware land surveyor.

B. Streets dedicated to public use shall be designed and constructed in accordance with standards established by the Delaware Department of Transportation, Division of Highways.

C. All entrances to the subdivision from a public street shall be designed and constructed in accordance with standards established by the Delaware Department of Transportation. A letter of no objection or other appropriate entrance approval from the Delaware Department of Transportation shall be required prior to final approval of the plan.

D. Private streets to be initially maintained by the developer and ultimately owners of lots within the development may be designed and constructed in accordance with Subsection B or must comply with the following standards.

E. Road geometry. All roads regulated by Sussex County shall meet fire access requirements as required pursuant to the Delaware State Fire Prevention Regulations (DSFPR).

(1) Road width.

(a) The minimum clear/unobstructed road width when using curb and gutter shall be 24 feet measured in the case of a vertical curb from face of curb to face of curb, and in the case of a rolled curb from flowline to flowline. The curb and gutter shall meet the DelDOT Standard Construction Details, latest edition, or stone set in place.

[Amended 2-5-2019 by Ord. No. 2629]

(b) The minimum clear/unobstructed road width when using open drainage shall be 24 feet.

(c) The minimum clear/unobstructed road width for one-way traffic shall be 14 feet.

(d) See Subsection E(7) in this section for additional information regarding on-street parking.

(2) Center-line radii.

(a) The minimum center-line radii for all roads posted at 17 miles per hour or less shall be 50 feet.

(b) The center-line for roads posted higher than 17 miles per hour shall be increased using the AASHTO (American Association of State Highway and Transportation Officials) Green Book for normal crown roads.

(3) Minimum and maximum longitudinal slope.

(a) The minimum slope for a curbed street is 0.30%.

[Amended 2-5-2019 by Ord. No. 2629]

(b) The minimum slope for an open ditch street is 0.50%.

[Amended 2-5-2019 by Ord. No. 2629]

(c) The minimum slope across a flowline is 0.50% unless a concrete valley gutter is used.

(d) The maximum longitudinal slope for all roads shall be 10%.

(4) Culs-de-sac.

(a) No island: The minimum radius for culs-de-sac without an internal island is 38 feet.

(b) Island: The paved area of a cul-de-sac with an internal grass island shall be 14 feet wide for one-way traffic and 20 feet for two-way traffic. The outer and inner radii shall be able to accommodate a ladder truck and subject to approval by the State Fire Marshal's Office.

(c) Culs-de-sac are required for dead-end streets: (i) greater than 300 feet in length as measured from the nearest turnaround area; or (ii) that serve more than four dwellings.

[Amended 2-5-2019 by Ord. No. 2629]

(5) Alternative turnarounds. The following alternative turnarounds are permitted:

(a) Those listed in the DSFPR.

(b) A looped road that meets DSFPR.

(c) Alternative accesses not listed above that meets DSFPR.

(d) The maximum length of a dead-end street (as measured from the nearest approved turn-around area) shall neither exceed 300 feet without an additional alternative turnaround nor serve more than four dwellings.

[Amended 2-5-2019 by Ord. No. 2629]

(6) Cross slope.

(a) The road cross slope can be a normal crown, superelevated or reverse crown.

(b) The maximum cross slope shall be 4%.

(c) The minimum cross slope shall be 2%.

(7) On-street parking.

(a) On-street parking shall be prohibited within the following locations:

[1] Fifteen feet of both sides of a fire hydrant and marked in accordance with DSFPR.

[2] Twenty feet of a traffic control device (i.e., stop sign/signal).

[3] Ten feet of the point of tangent/point of curvature of an intersection.

[4] Ten feet of a crosswalk.

[5] Ten feet of a driveway.

(b) These on-street parking requirements shall not affect nor be calculated as part of the parking requirements of Chapter 115, § 115-162A and B.

(8) Right-of-way and/or access easements. Rights-of-way shall be used in major subdivisions. Access easements shall be used in developments where all of the underlying land of the development will be held in common ownership. The right-of-way or access easements for non-state-maintained roads shall be:

[Amended 2-5-2019 by Ord. No. 2629]

(a) Placed three feet behind the back of curb.

(b) Placed one foot behind the ten-year stormwater surface of roadside swales.

(9) Sidewalks. Sidewalks shall satisfy the following requirements:

[Amended 2-5-2019 by Ord. No. 2629]

(a) They shall be placed within the right-of-way or deeded easement in favor of the owner of the common elements.

(b) A sidewalk can be adjacent to the travel lane using additional pavement that can be added but must be differentiated from the travel lane using demarcation every 300 feet.

(c) If the sidewalk is to be located between the parking space(s) and the roadway, the parking space shall extend a minimum of 18 feet beyond the edge of the sidewalk.

(d) For projects with open drainage (with or without grass strips), the sidewalk must be placed along the edge of the travel lane.

(e) Sidewalks must have five feet of clear width.

(f) Sidewalks that are not constructed adjacent to the travel lane using additional pavement must be constructed using a mix of 4,000 PSI with fiber mesh.

(g) All sidewalks must have a minimum cross slope of 1% and a maximum cross slope of 2%.

(h) All sidewalk expansion joints shall consist of rubber or other nonbiodegradable material approved by the Sussex County Engineer or his or her designee.

(i) All sidewalks adjacent to curbing shall have expansion joints that are sealed and caulked with materials approved by the Sussex County Engineer or his or her designee.

(j) Street crosswalk markings shall be placed at intersections and mid-block crossings where average daily traffic counts are equal to or greater than 1,000.

(10) Utilities. All utilities shall be placed within an easement and typically located within the following utility corridor wherever possible:

(a) Sewer: center line of road or travel lane.

(b) Water: under sidewalk (where installed) or five feet behind edge of pavement or back of curb.

(c) CATV/telephone: back of sidewalk or behind top of ditch bank.

(d) Gas/propane: two feet behind right-of-way.

(e) Electric: five feet behind right-of-way.

(11) Roundabouts. Roundabouts shall be designed to accommodate a ladder truck entering, exiting and traveling around the roundabout and subject to approval by the Fire Marshal's Office.

(12) Eye brows. Eye brows are noncircular culs-de-sac that have various shapes and sizes that may provide design flexibility. Eye brows shall be designed to accommodate a ladder truck entering and exiting the eye brow and subject to approval by the Fire Marshal's Office.

(13) Internal intersections. The minimum radius at edge of pavement for an internal intersection shall be 25 feet.

(14) Sight distance. No vegetation or ground/monument signs may be placed within 50 feet of the point of tangent/point of curvature of an intersection with a height greater than three feet, unless shown otherwise with a site triangle.

(15) Curb islands. All landscaped curbed islands shall have an underdrain or liner along back of curb to prevent oversaturation from undermining the curb.

(16) Alleys.

(a) The maximum clear/unobstructed pavement width shall be 16 feet.

(b) The minimum clear/unobstructed pavement width shall be 12 feet.

(c) The longitudinal cross slopes shall comply with Subsection E(3) and (6) of this section.

F. Storm drainage.

(1) Design storm. Storm drainage systems within roadways regulated by Sussex County shall be designed using the Rational Method to convey the ten-year storm event. The Sussex County Rainfall Intensity Duration Frequency Curves and Rainfall Intensity Table as defined in the DelDOT Roadway Design Manual shall be used for design purposes.

(2) Additional requirements. For drainage along roadways with greater than 3,000 ADT that serve communities with a single access point, the Sussex County Engineer or his or her designee may require additional analysis to demonstrate that the road remains passable during the twenty-five-year storm event. For purposes of this requirement, "passable" shall mean that the roadway may have stationary water of up to six inches higher than the crown of the road.

(3) Open drainage. Open drainage systems are allowed for subdivisions with a minimum lot width of 100 feet, or a width less than 100 feet if utilizing shared driveways with an adjacent lot, and shall consist of concrete or grass open swales designed in accordance with the following design criteria:

(a) Minimum slope:

[1] The minimum slope of a concrete swale shall be 0.30%.

[2] The minimum slope of a grass swale shall be 0.50%.

(b) Bottom width:

[1] Concrete swale: two feet wide with one inch depth valley gutter in the middle. Porous concrete will be subject to the requirements of Subsection G.

[2] Grass lined swale: minimum width of two feet for trapezoidal channel or V-ditch section.

(c) Side slopes:

[1] Front slope: four-foot horizontal minimum: one-foot vertical.

[2] Back slope: three-foot horizontal minimum: one-foot vertical with appropriate matting per approved erosion and sedimentation control (ESC) plans.

[3] Driveway culvert embankments: three-foot horizontal minimum: one-foot vertical with appropriate matting per approved ESC plans.

(d) Swale depth:

[1] Minimum of one foot except at furthest upstream end, where a six-inch depth is required.

[2] Maximum of 2.5 feet contiguous to single-family lots, except where approved otherwise by the Sussex County Engineer or his or her designee.

(e) Freeboard: The design stormwater surface elevation for open swales shall not exceed the edge of pavement or travel lane.

(4) Closed drainage. Closed drainage systems shall consist of pipe, inlet and manhole network systems.

(a) Minimum size: Minimum pipe size is a diameter of 15 inches or equivalent.

(b) Pipe velocity: The minimum full flow pipe velocity shall be two feet per second.

(c) Freeboard: The hydraulic grade line cannot exceed the rim elevation during the design storm event. The design storm surface elevation for the downstream stormwater management facility or receiving water shall be used as the tailwater for the design of the closed drainage system, or the water surface elevation at time of peak inflow. Where there is no downstream tailwater impact, the starting downstream hydraulic grade line elevation shall be the crown of the discharge pipe. For tidal discharges, the minimum tailwater shall be mean high water elevation. The tailwater elevation should be noted on the submitted computations.

(d) Pipe material: All pipe shall be reinforced concrete pipe (RCP) or high-density polyethylene pipe (HDPE), (AASHTO M294 Type S or AASHTO M252 Type S). Flexible pipe (HDPE) shall have a minimum cover of one foot, as measured from top of pipe to bottom of bituminous concrete pavement, or to the wearing surface of concrete pavement. Rigid pipe (Class III/IV RCP) shall have 12 inches of cover to the wearing surface of asphalt pavement or nine inches of cover to the top of stone in a concrete pavement section. Cover requests less than those specified above for RCP must be accompanied with load calculations based on methodology in the American Concrete Pipe Association's Concrete Pipe Design Manual. Alternate pipe materials for pipe diameters greater than 36 inches shall be allowed by the Sussex County Engineer or his or her designee on a case-by-case basis.

(5) Cross road culverts.

(a) Minimum size: The minimum size is 15 inches in diameter or equivalent.

(b) Pipe slope: The minimum full pipe flow velocity shall be two feet per second.

(c) Personnel safety grates: All culverts shall have a personnel safety grate as required by the Department of Natural Resources and Environmental Control.

(6) Driveway culverts:

(a) Minimum size: The minimum culvert size is 12 inches in diameter.

(b) Pipe slope: The minimum full pipe flow velocity shall be two feet per second.

(c) Pipe material: Pipe shall be RCP or HDPE (AASHTO M294 Type S). HDPE shall be allowed with minimum six inches cover of stone over the pipe during homebuilding operations and Type B Graded Aggregate Base Course (GABC) backfill.

(d) Analysis: An analysis of driveway culverts is required on the downstream portion of a lot to ensure that they are sufficiently sized to convey water without impeding drainage in the roadside ditch. Culvert size for each individual lot shall be shown in the construction plans required by § 99-30.

G. Stormwater management in street or road rights-of-way. Stormwater management design within all street or road rights-of-way shall be in accordance with the Delaware's Sediment and Stormwater Regulations and accompanying technical documents, or as otherwise approved by the Sussex Conservation District, or other applicable regulation. The stormwater management plan shall be approved by the Sussex Conservation District.

(1) Several best management practices are suitable for use within the right-of-way, as listed below, and shall be designed in accordance with the Department of Natural Resources and Environmental Control's Technical Document, Chapter 3.06.02, Post Construction Stormwater BMP Standards and Specifications, as that document may be amended or supplemented.

(a) Sheet flow to filter strip.

(b) Bioretention.

(c) Vegetated channel/bioswale.

(d) Infiltration practices.

[1] Infiltration trench.

[2] Perforated pipe with infiltration.

(e) Permeable pavement systems, as follows, may be used in the right-of-way at the discretion of the Sussex County Engineer or his or her designee.

[1] Porous asphalt.

[2] Pervious concrete.

[3] Permeable pavers.

(f) Soil amendments.

(g) Detention practices (underground). Detention systems under the pavement section may be approved on a case-by-case basis by the Sussex County Engineer or his or her designee.

(h) Proprietary practices as may be approved by the Sussex County Engineer or his or her designee.

(i) Other practices that become approved by the Department of Natural Resources and Environmental Control or the Sussex Conservation District, as allowed by the Sussex County Engineer or his or her designee.

(2) Stormwater management practices outside of the right-of-way that are designed to treat roadway drainage must be located in a deeded open space area and contained within an easement.

H. Road pavement design.

(1) Average daily trips. For the purposes of this chapter, the following average daily trips (ADTs) per unit shall be used:

(a) Single-family dwelling: 10 ADTs per unit.

(b) Townhouse: seven ADTs per unit.

(c) Multifamily dwelling (not townhouse): six ADTs per unit.

(d) Manufactured home: five ADTs per unit.

(e) Retirement community: four ADTs per unit.

(2) Subbase course for standard pavement must include one of the following:

(a) Graded aggregate base course: eight-inch maximum lift.

(b) Crushed concrete: eight-inch maximum lift.

(c) Millings: eight-inch maximum lift.

(3) Bituminous concrete for standard pavement must include one of the following:

(a) Type bituminous concrete base course: four-inch maximum lift.

(b) Type B: four-inch maximum lift.

(c) Type C: two-inch maximum lift.

(4) Porous bituminous concrete.

(a) May be permitted in consultation with the Sussex County Engineer or his or her designee.

(b) Must include a maintenance management plan.

(5) Porous Portland cement concrete.

(a) May be permitted in consultation with the Sussex County Engineer or his or her designee.

(b) Must include a maintenance management plan.

(6) Pavers.

(a) May be permitted in consultation with the Sussex County Engineer or his or her designee.

(b) Must include a maintenance management plan.

(7) Structural numbers (SN).

(a) One to 50 ADT shall require SN > 2.42 based on California Bearing Ratio 10. Base course sections shall be equivalent to 80% of the SN; provided, however, that the topcoat shall not be less one-and-twenty-five-hundredths-inch Type C.

(b) Fifty-one to 3,000 ADT shall require SN > 3.06 based on California Bearing Ratio 10. Base course sections shall be equivalent to 80% of the SN; provided, however, that the topcoat shall not be less one-and-twenty-five-hundredths-inch Type C.

(c) Greater than 3,001 ADT: Pavement section shall be determined by a geotechnical engineer.

I. Unless otherwise provided herein, all materials used in work governed by this section shall meet or exceed the DelDOT Standards and Specifications for Road and Bridge Construction, as amended.

J. The Sussex County Engineer shall have, in appropriate circumstances and upon a written finding of good cause, the ability to grant administrative waivers from the requirements of this section.

§ 99-19 Lots.

A. The lot design shall be such that all lots will provide satisfactory building sites properly related to topography and the character of surrounding development.

B. The dimensions and areas of all lots shall comply with the requirements of the zoning district in which they are located. In any case where public water supply and/or public sewerage are not available or are not to be provided, all residential lots shall comply with the minimum lot dimensions and areas established by the State Department of Natural Resources and Environmental Control after appropriate water percolation tests and soil evaluations have been performed, provided that these lot size requirements are greater than required under the Zoning Ordinance.[1]

[1] Editor's Note: See Ch. 115, Zoning.

C. Excessive lot depth in relation to lot width should be avoided. A ratio of depth to width of 2:1 is desirable.

D. Corner lots shall have sufficient width to permit appropriate building setbacks from both streets in accordance with the Zoning Ordinance.[2]

[2] Editor's Note: See Ch. 115, Zoning.

E. Every lot shall abut upon and have access to a street.

F. Double-frontage and reverse-frontage lots shall be avoided, except where their use is essential to overcoming special topographic problems or to separating residential development from heavy street traffic.

G. Insofar as possible, side lot lines should be substantially at right angles or radial to the street line, except where a variation in this requirement will provide an improved street and lot layout.

H. The minimum street frontage of any lot shall be 30 feet measured along the right-of-way line. Minimum lot widths shall comply with the appropriate district regulations of the Comprehensive Zoning Ordinance.[3]

[3] Editor's Note: See Ch. 115, Zoning.

§ 99-20 Easements.

A. Easements shall be provided where necessary to meet public utility requirements. All subdivision lots shall have five-foot-wide easements along all lot lines for a total easement width of at least 10 feet along a lot line common to two lots. Easements of greater width may be required along lot lines or across lots, where necessary. Easements along perimeter boundaries of the subdivision shall be no less than 10 feet in width on the interior side of the boundary.

B. Where a proposed subdivision is traversed by any stream, waterway or drainageway, the subdivider shall make adequate provision for the proper drainage of surface water, including the provision of easements along such waterways and drainageways.

C. No building, structure or other permanent obstruction shall be placed on any easement.

§ 99-21 Public sites and open spaces.

[Amended 12-7-2004 by Ord. No. 1734]

A. Where the proposed subdivision includes lands proposed for use as parks, playgrounds, playfields, public landings or school sites in the Comprehensive Plan, the subdivider shall indicate the location of such lands on the subdivision plat and shall reserve the right of purchase of such lands by the appropriate jurisdiction for the time period specified herein. If the reserved lands are not purchased by the appropriate jurisdiction within the specified time limit, the subdivider shall be free to market such lands for an alternate purpose as specified on the approved subdivision plat.

B. Park, playground and playfield areas may be required to be reserved for a period of two years from the date of recording the subdivision, and school sites shall be reserved for four years from such date.

C. Where deemed essential by the Commission upon consideration of the type of development proposed in the subdivision, the subdivider may be required to dedicate other areas or sites of a character, extent or location suitable to meet the needs of such development. In lieu of dedication, such additional areas may be reserved for the common use of all property owners in the proposed subdivision through deed restrictions or agreements approved by the Commission, which restrictions or agreements may include a right of enforcement by the County Council.

D. For residential subdivision and other residential land development, the following table shall serve as a guide for determining the minimum percentage of the total site which shall be set aside for park and open space uses:

[Amended 12-16-2008 by Ord. No. 2022]

Gross Density (dwelling units per acre)	Minimum Percentage of Open Space
2 to 5	10
6 to 10	15
Over 10	25 or more