Delaware Administrative Code
Title 7 - Natural Resources and Environmental Control
5000 - Division of Watershed Stewardship
7400 - Watershed Assessment Section
7402 - Shellfish Sanitation Regulations
Appendix 11 - Policy To Determine Shellfish Growing Area Classification in and Around Wet Slip Basins and Artificial Lagoons
I. Introduction:
In 1988 the ISSC determined that human sewage may be discharged from boats and thereby may pose a human health threat due to consumption of sewage contaminated shellfish. The fecal discharge from one adult person is potentially the pathogenic equivalent to that from hundreds to thousands of people via a sewage treatment plant, depending upon the level of treatment. In 1988 the ISSC adopted the FDA Guideline, "Evaluation of Marinas By State Shellfish Sanitation Control Officials," to be used by the states as a basis for developing and implementing regulations establishing shellfish harvest buffers around wet slip basins associated with marinas and dry stack facilities. This is now NSSP doctrine.
The sewage discharge from boats is unpredictable and not uniformly distributed throughout the water column. Detection of human pathogen indicator bacteria by current methods may not provide sufficient information to properly classify the waters in and around wet slip basins. Therefore, the FDA Guideline requires restrictions on shellfish harvesting in and around wet slip basins based on the theoretical sewage discharge from the basins without regard to levels observed by monitoring.
In addition, precedent exists for the restriction of shellfish harvesting in artificial lagoons based on the poor water quality and/or the concentration of potential pollution sources often found in such lagoons.
Delaware's "Policy to Determine Shellfish Growing Area Classification In and Around Wet Slip Basins and Artificial Lagoons" is based on the FDA Guideline and the precedents established regarding artificial lagoons.
II. Definitions:
A. Artificial Lagoon: A man-made, dead-end waterway, interconnected with another waterway.
B. Average Depth: The average depth of the water at mean low water in a proscribed area.
C. Average Number of People Per Boat: The average number of people occupying each boat during the daily use of the boats in a specific survey area.
D. Background: The ambient biological, chemical and/or physical conditions of a water body.
E. Best Management Practices (BMPs): Initiatives that in theory reduce the theoretical waste discharge of a wet slip basin.
F. Charter Boat: A commercial boat hired to perform services for patrons, typically for a flat fee.
G. Commercial Boat: A boat used primarily as a means of making money.
H. Dilution Formula: The following formula used to calculate the area impacted by wet slip TWDR x 2 e9 FC x # of people/boat x wet slip capacity shellfish harvest standard average depth
I. Dilution Formula Loading Factor(Loading Factor): The following components of the dilution formula are loading factors, as follows:
Theoretical Waste Discharge Rate (TWDR).
Two Billion (2 e9) Fecal Coliform Bacteria (FC) per person per day (this is a constant).
Average number of people per boat.
Wet slip capacity.
J. Discharge: Any actual or theoretical release of fecal material, pathogenic microorganisms, poisonous and deleterious substances. This includes the escape, disposal, spillage, leaking, pumping, emitting, pouring, dumping or emptying of such discharges.
K. Dry Stack Facility: A boating facility which stores boats on dry land, including but not limited to: dry stack facilities; boatels; valet storage; pigeon hole storage; and stackominiums. A dry stack facility may have wet slip capacity.
L. Dump Station: A mechanical and/or gravity fed connection to an approved sewage disposal facility used for the purpose of the disposal of human generated waste, such as the sewage from a porta-pottie.
M. Head Boat: A commercial boat hired to perform services for patrons, typically for a fee per patron.
N. Marina: Any water area with a structure (dock, basin, floating dock, etc.) which is utilized for docking or otherwise mooring vessels and is constructed to provide temporary or permanent docking space for more than ten boats. The definition of marina shall include all related ancillary structures and functions such as docks, piers, boat storage areas, boat ramps, anchorages, breakwaters, channels, moorings, basins, boat repair services, boat sales, sales of supplies normally associated with boating such as fuel, bait, and tackle, boat rentals, and parking areas.
O. Marine Head: A toilet or other human waste catchment device with retention and/or discharge capability. A marine head may or may not be an MSD. MSD is the term for a Coast Guard approved marine head.
1. Type I MSD: A device that produces an effluent having a fecal coliform bacteria count not greater than 1,000 per 100 milliliters and no visible floating solids.
2. Type II MSD: A device that produces an effluent having a fecal coliform bacteria count not greater than 200 per 100 milliliters and suspended solids not greater than 150 milligrams per liter.
NOTE:A marine head and holding tank capable of being discharged into receiving waters and into a pumpout unit is defined here as a Type II MSD.
3. Type III MSD: A device designed for containment of sewage within a holding tank with the capability to discharge only into a pumpout unit (Type III Coast Guard definition without a Y-valve).
4. Porta-potty: A portable, self contained sewage retention device that must be removed from the boat and dumped.
P. Occupancy Rate: The percentage of boats in a wet slip basin that are occupied during the course of a day relative to the total number of occupied slips in the wet slip basin at the time of the collection of this information.
Q. Overnight Use Boat: Any boat used for overnight habitation.
R. Potential Sewage Discharge Rate: The percentage of boats in a wet slip basin with marine heads capable of discharging sewage directly into receiving waters (This excludes only Type III MSDs, as Type III MSD is defined in this policy) relative to the total number of boats surveyed in the wet slip basin at the time of the collection of this information.
S. Pumpout Facility: A mechanical device which is temporarily connected to a boat for the purpose of removing sewage from a marine head holding tank to an approved sewage disposal facility.
T. Sewage: Human body wastes and wastes from toilets and other receptacles intended to receive and/or retain human body wastes.
U. Shellfish Growing Area Standard: The median or geometric mean of Fourteen Fecal Coliform Bacteria (FC) per 100 milliliters (ml) (or the equivalent: 3962 FC/cubic foot) of water must be maintained in shellfish growing water in order to harvest and market shellfish from that water.
V. Theoretical Waste Discharge: Theoretical waste discharge rate multiplied by two billion Fecal Coliform bacteria per person per day multiplied by the average number of people per boatmultiplied by the wet slip capacity.
(TWDR x 2 e9 FC x # of people/boat x wet slip capacity)
W. Theoretical Waste Discharge Rate(TWDR): The potential sewage discharge rate multiplied by the occupancy rate.
X. Wet Slip: A place in the water where a boat may be docked or otherwise moored to a fixed or floating structure, including but not limited to a dock, pier, mooring or anchorage.
Y. Wet Slip Basin: A natural waterway and/or artificial lagoon and/or portions thereof containing more than ten wet slips. A wet slip basin may be associated with a marina and/or with a dry stack facility.*
*An exception shall be made to the >10 boat qualifier if the theoretical waste discharge and/or the potential for waste discharge in the basin is determined by the DNREC to be great enough to require restrictions on shellfish harvesting in or adjacent to and in the basin.
Z. Wet Slip Basin Classification: A determination as to the type of wet slip basin. Differentiation as to wet slip basin type based on the parameters listed reflects variation in the theoretical waste discharge. The types of wet slip basins are as follows:
1. Commercial Wet Slip Basin: A wet slip basin which has a significant number of commercial boats.
2. Overnight Use Wet Slip Basin: A wet slip basin which has a significant number of overnight use boats.
3. Residential Wet Slip Basin: A wet slip basin which has primarily non-commercial boats, most of which are less than or equal to 28' and which serves a planned residential community and/or any general residential population(s).
AA. Wet Slip Basin Classification Survey: The collection of the verified information required for classification of a wet slip basin.
AB. Wet Slip Capacity: The total number of wet slips in a wet slip basin.
AC. Work Boat: A boat used primarily for commercial purposes such as the harvesting of marine life for profit, dredging or police work, etc.
III. Policy Specifications:
A. General Policy Specifications:
This policy defines the restrictions on shellfish harvesting in and around wet slip basins associated with marinas and dry stack facilities and also in artificial lagoons.
1. Artificial Lagoons: All artificial lagoons, regardless of intended or actual use, shall be classified as "Prohibited" for the harvesting of shellfish.
2. Wet Slip Basins and Adjacent Areas:
All wet slip basins located in or adjacent to shellfish growing areas shall be classified as Prohibited for the harvesting of shellfish. DNREC shall classify shellfish growing areas or portions thereof adjacent to wet slip basins as other-than-Approved as determined on a volumetric basis. The size of the shellfish growing area(s), or portions thereof classified on the basis of the presence of wet slip basins, shall correspond to the volume of water required for dilution of the theoretical waste discharge from the wet slip basins as determined by the application of dilution formula loading factors. The area required for dilution shall be determined by performing the dilution formula calculations. Dilution formula loading factors shall be collected during sanitary surveys and/or wet slip basin classification surveys. The size and configuration of the shellfish growing area(s), or portions thereof classified based on the theoretical waste discharge from wet slip basins, shall be reevaluated and if necessary adjusted on a regular basis using the best available information. When reliable mean low water depths are not available actual field measurements shall be taken as a basis for determining available dilution volume. DNREC shall determine cumulative wet slip capacity of individual wet slip basins and/or the sum of more than one wet slip basin irrespective of demarcations that may arbitrarily and/or artificially reduce, eliminate or otherwise alter the theoretical waste discharge(s) of the wet slip basin(s). Therefore, DNREC will establish wet slip basin demarcations based on, but not limited to:
common ownership and/or management and/or operation;
sharing common waterways such as an entrance channel; and
being part of a common development plan.
B. Surveys:
1. Sanitary Surveys: A sanitary survey shall be considered valid by definition only if conducted during a time that is reflective of peak use of the facility such as warm season holidays and weekends when the weather is conducive to boating.
2. Wet Slip Basin Classification Surveys:
A wet slip basin classification survey may be performed based on written information and/ or by direct observation of the facility. This allows the classification of both proposed and existing wet slip basins. The minimum information required to constitute a valid wet slip basin classification survey of an existing or proposed marina and/or dry stack facility shall be as listed below.
facility name;
owner or applicant name, address and phone number;
specific facility location narrative and drawing showing the location, dimensions and configuration of the facility;
average depths and areas of the wet slip basin and entry and/or flushing channels;
a breakdown of the size range and numbers of proposed wet slips, (transient and non-transient) and/or dry stack capacity;
size range and types of boats to be accommodated including the presence of commercial boats and/or overnight use boats;
general population served by the facility; for example, residential population of a single community or general residential population or commercial clients, etc;
types of MSDs to be allowed;
best management practices (BMPs) employed, including, but not limited to those listed in section III. D. Best Management Practices;
available hydrographic information; and
any other information that the owner or applicant wishes to submit.
C. Dilution Formula Loading Factors:
1. Loading Factor Application Parameters:
a. Loading factors shall never be smaller than the minimum loading factors required by the National Shellfish Sanitation Program.
b. Loading factors shall be considered valid by definition only if they are reflective of peak use of a wet slip basin, such as the use occurring on warm season holidays and weekends when the weather is conducive to boating, as determined by the DNREC.
c. All loading factors shall be derived from a representative number of boats as determined by DNREC. All loading factors shall be multiplied by the total wet slip capacity of marinas and dry stack facilities.
d. Loading factors may be derived from a survey of an individual wet slip basin and applied only to that facility surveyed.
e. Existing loading factors may be applied to other identically classified wet slip basins.
f. Written information associated with wet slip basin classification surveys may be assessed and applied based on the criteria listed under "Individual Loading Factors."
g. Loading factors derived from a sanitary survey may override loading factors derived from wet slip basin classification survey.
h. Any combination of existing loading factors and wet slip basin classification survey generated or sanitary survey generated loading factors may be applied at the discretion of DNREC, and also irrespective of the classification of the wet slip basin; except loading factors shall never be lower than the minimum required loading factors.
2. Existing Loading Factors:
Loading factors derived from a wet slip basin classification survey shall be no smaller than the following:
a. Residential Wet Slip Basin Minimum Loading Factors (Inadequate or No BMPs Employed)
i. 2 billion fecal coliform bacteria per person per day
ii. 3.3 people per boat
iii. 6.5% theoretical waste discharge rate
b. Residential Wet Slip Basin Minimum Loading Factors (Adequate BMPs Employed by Marina)
i. 2 billion fecal coliform bacteria per person per day
ii. 3.3 people per boat
iii. 4% theoretical waste discharge rate
c. Minimum Loading Factors for Wet Slip Basins (Only the Wet Slip Capacity
is Known)
i. 2 billion fecal coliform bacteria per person per day
ii. 2 people per boat
iii. 100% theoretical waste discharge rate
3. Loading Factor Specifications:
a. Average Number of People Per Boat:
Within a specific survey area, the average number of people per boat shall be determined by counting the number of people in all boats surveyed, and dividing this number by the number of boats surveyed.
b. Potential Sewage Discharge Rate:
i. Boats with no marine head are determined not to be a probable source of sewage, and shall therefore be assigned a 0% potential sewage discharge rate. Boats with type III MSD's (as Type III MSD is defined in this policy) under normal conditions do not discharge sewage into receiving waters and shall therefore be assigned a 0% potential sewage discharge rate. Boats with any other type of marine head are capable of discharging sewage into receiving waters and shall be assigned a 100% potential sewage discharge rate.
ii. An overnight use boat is defined as such due to the increased potential for the discharge of sewage associated with spending extended periods of time on the boat. Therefore, overnight use boats shall be assigned a 100% potential sewage discharge rate unless the installation of a Type III MSD (as Type III MSD is defined in this policy) is proven.
iii. It is possible that any boat with a cabin could carry a marine head. As determined by surveys, the loading factors listed below are reflective of the installation rates for marine heads that are capable of discharging into receiving waters. Unless information to the contrary is determined by direct observation; the following shall apply to a specific survey area or areas as potential sewage discharge rates:
6.5% of all boats < 25'; or the percentage of boats < 25' with cabins, relative to the total number of boats < 25' surveyed, which ever number is greater; and
80% of all boats > 25' or the percentage of boats > 25' with cabins, relative to the total number of boats > 25' surveyed, which ever number is greater
c. Occupancy Rate:
Occupancy rates shall be determined by counting the total number of boats in a wet slip basin that are occupied by a person or persons during the course of a day as a percentage of the total number of wet slips which contain boats sometime during a 24 hour period immediately before or after and inclusive of the time period during which the occupancy rate information was gathered. The aforementioned portion of the 24 hour time period before or after the data collection time period shall be during a time period reflective of peak use of the facility.
d. Theoretical Waste Discharge Rate (TWDR):
The TWDR is determined by multiplying the potential sewage discharge rate by the occupancy rate.
D. Best Management Practices (BMPs):
The TWDR may be adjusted (within the parameters listed in this policy) if BMPs are employed and the marina or dry stack facility only contains boats with Type III MSDs (as Type III MSD is defined in this policy). The following are initiatives that will be given consideration as BMPs by DNREC:
the presence, availability and documented use of pumpout facilities and/or dump stations;
the presence and documented and proven use of dye tablets in MSD holding tanks;
the use of written legal agreements prohibiting the discharge of sewage and which provide substantial penalties for the discharge of sewage;
the use of written legal agreements permitting only boats with Type III MSDs or Type II MSDs with holding tanks capable of being discharged into a pumpout unit;
the use of a harbor master or the equivalent to monitor activities in the marina, such as the illicit discharge of sewage from boats;
the keeping of accurate records; and
the adherence to the seasonal time frame (October 15 through March 15) for the adequate removal boats to allow depuration and the seasonal harvest of shellfish.
NOTE: Other means utilized for the purpose of reducing theoretical waste discharge may be given consideration as BMPs on a case by case basis. Not all BMPs listed are required to be employed to allow the default to the smaller loading factors. The smaller loading factors shall be applied on a case by case basis.
E. Specifications for Shellfish Growing Areas Classified on the Basis of Wet Slip Basins:
1. Shellfish Growing Area Size:
a. Shellfish growing areas or portions thereof classified on the basis of the theoretical waste discharge from wet slip basins shall be no smaller than those required based on the required loading factors.
b. Dilution formula loading factors shall be applied assuming hypothetical zero FC background water. Shellfish growing areas or portions thereof impacted on the basis of the theoretical waste discharge from wet slip basins shall correspond to the volume of water required for dilution of the theoretical waste discharge from wet slip basins to the shellfish growing area standard. The volume of water in wet slip basins is available for dilution and therefore shall be included in the required dilution area.
c. Reclassification of the shellfish growing area or portions thereof beyond a wet slip basin shall not be required if the wet slip basin is large enough for adequate dilution of the theoretical waste discharge produced by the wet slip basin.
d. Reclassification of the shellfish growing area or portions thereof adjacent to a wet slip basin will be required if the volume of water in the wet slip basin is inadequate for dilution of the theoretical waste discharge produced by the wet slip basin.
2. Shellfish Growing Area Configuration:
The boundary lines associated with shellfish growing areas or portions thereof impacted on the basis of the theoretical waste discharge from wet slip basins shall be straight lines established between imaginary points and/or fixed landmarks and marked by buoys and/or signs. These straight lines shall encompass at least the area determined to be impacted based on: the volume of water required for the dilution of the theoretical waste discharge from the wet slip basin(s) to the shellfish growing area standard; and the configuration of the area impacted based on available hydrographic data* and/or by superimposing an arc as measured from the marina entrance channel(s) onto a map, encompassing the area required for dilution. The area determined to be impacted by wet slip basins shall be superimposed over existing shellfish growing areas that are not classified on the basis of the theoretical waste discharge from wet slip basins. However, there shall be no overlap of the required wet slip basin dilution areas regardless of the shellfish growing area classification.
*Only hydrographic data approved by the FDA for use in the determination of the theoretical impact of wet slip basins shall be used when shellfish growing areas specifications are determined.
3. Shellfish Growing Area Classification Adjacent to Wet Slip Basins:
a. The classification of the shellfish growing areas or portions thereof impacted on the basis of the theoretical waste discharge from wet slip basins shall always default to the more restrictive, existing classification or a combination of conditions that provide cumulative required restrictions on shellfish harvesting.
b. Shellfish growing areas or portions thereof adjacent to wet slip basins that are determined to be impacted based on the theoretical waste discharge from wet slip basins may be classified as Seasonally Approved, Conditionally Approved, or Prohibited.
i. Seasonally Approved Classification:
A shellfish growing area or portions thereof (excluding the wet slip basin)
A residential wet slip basin may be declared seasonally vacant by DNREC when all but ten or less boats remain in the wet slip basin, and are to remain out of the basin for the time period (including the depuration period) during which the harvest of shellfish is allowed; OR a residential wet slip basin may be declared seasonally vacant by DNREC if enough dilution volume exists in the basin to accommodate the remaining boats in the basin without requiring additional dilution volume outside of the basin to adequately dilute theoretical loading from the basin.
A wet slip basin not classified as "Residential" may be considered seasonally vacant after an adequate number of boats, as determined by DNREC, are removed from the wet slip basin and are to remain out of the marina for the time period (including the depuration period) during which the harvest of shellfish is allowed.
ii. Conditionally Approved Classification:
DNREC may allow the harvest of shellfish on a seasonal basis in areas determined to be impacted by a wet slip basin, as per pre-established condition(s) which may include seasonal removal of boats from the wet slip basin(s).
iii. Prohibited Classification:
A shellfish growing area or portions thereof determined to be impacted by the theoretical waste discharge from a wet slip basin shall be classified as "Prohibited" if it is determined by the DNREC that a public health threat could result by classifying the area as other than Prohibited.
IV. Examples and Specifications:
Project name: Little Chester Trailer Park & Marina
Applicant information: Recreational Aquatic Profit Entity, Inc.
P.O. Box 666, Washington, D.C. 20002
Project location: Ulva Landing, Indian River Bay
Wet slip basin avg. depth: 5'
Number and size of slips: 102 slips, each slip 18' by 30'
Size and types of boats: Recreational power and sail boats boats to be accommodated:
roughly in the 16' to 25' range
General population served: Private, community residents only
Hydrographic information: None available
BMPs to be employed: One stationary pumpout unit;
Written agreement indicating seasonal removal of boats, as per DNREC Specifications:
Examples 1-A. and 1-B.
Seasonally Approved area size determination is as follows:
TWDR x 2 e9 FC x # of people/boat x wet slip capacity
shellfish harvest standard
average depth
6.5% x 2 e9 FC x 3.3 people/boat x 102 slips
3962 FC/cubic foot of dilution water
5'
= 2,208,884 sq ft = area required for dilution
102 slips @ 18' x 30' each = 55,080 sq ft = area representing volume in marina at 5' average depth available for dilution
2,208,84 sq ft - 55,080 sq ft = 2,153,804 sq ft = area required for dilution beyond the marina basin
1/2 circle radius = * 2,153,804 sq ft x 2
* Pi
= * 4,307,608 sq ft = * 1,371,154.2 = 1170'
* Pi
Example 1-A. The entire impacted area, as determined by superimposition of an arc based on the theoretical waste discharge from the marina, is within a currently classified Prohibited area. Therefore, no change in shellfish growing area classification for the impacted area is required.
Existing Existing Existing
Approved Approved/Prohibited Prohibited
Area Boundary Area
Proposed 2,153,804 sq ft Superimposed
Seasonally Approved area Arc
(area of 1/2 circle)
Proposed Upland
Marina Basin 102 slips Land
Example 1-B. The portion of the Approved shellfish growing area, (in this case 1/2 the total area required for dilution) as determined by superimposition of an arc based on theoretical waste discharge from the marina, is reclassified as Seasonally Approved. NOTE: Rather than actually enforcing a curved boundary, the boundary shall be a straight line encompassing the required 1,076,902 sq ft Seasonally Approved area. Curved lines are not enforceable.
Existing Existing Existing
Approved Approved/Prohibited Prohibited
Area Boundary Area
Proposed 1,076,902 sq ft Superimposed
Seasonally Approved area Arc
(1/2 area of 1/2 circle)
Proposed Upland
Marina Basin 102 slips Land
Example 2: Two 51 slip Residential Marinas, Inadequate BMPs
Existing Existing Existing
Prohibited Approved/Prohibited Approved
Area Boundary Area
Proposed 2,153,804 sq ft Seasonally Approved area
(1,076,902 sq ft x 2)
(Each marina basin is 27,540 sq ft)
Proposed
51 Marina 51
slips Basins slips
NOTE: There is no overlap of dilution areas. The volume of water represented by the shaded area may not be counted for dilution of the theoretical waste discharge from both marinas.
