BBP 1993 Comment Letter
August 7, 2002
on Title 5 Revisions
Charles Gricus, Director of Planning
Wareham Department of Planning
54 Marion Road
Wareham, MA 02571
Re: Tihonet Pond Drainage Report Plan, A.D. Makepeace, Co. proposed subdivision
Dear Mr. Gricus:
Upon your request, the Buzzards Bay NEP has reviewed the submitted "Drainage Report for Tihonet Pond" (dated July 8, 2002) with regard to potential post-development effects this project may have on sensitive resources. This review is without the benefit of an onsite visit as the Buzzards Bay NEP has been denied access to the property (phone conversation with A.D. Makepeace representative on July 26, 2002). Included with the Drainage Report were the following plans:
� Pre-Development Catchment Areas
� Post-Development Catchment Areas
� Structure Catchment Areas
As proposed, this project represents a more traditional-style subdivision plan with the 55 acres of land being subdivided into 35 houselots, a stormdrain system for road drainage, and structural management practices to provide stormwater control as required under the Department of Environmental Protection's (DEP) Stormwater Policy. Discussed in the Drainage Report and identified as water/wetland resources on the subdivision plan are Tihonet Pond and an "isolated wetland".
Wetland Related Issues
1. The Buzzards Bay NEP is unable to review the veracity of the wetland boundary on the plans without a site visit. It is our understanding that the Wareham Conservation Commission approved the wetland delineation shown on the plans through a separate Request for Determination of Applicability prior to the submission of subdivision plans to the Town. However, the Conservation Commission decision was based exclusively on the evaluation and acceptance of the wetland boundaries shown, and did not exclude, or rule out the possibility of other wetlands on the site. Conservation Commission rulings of this type are not uncommon for very large parcels when an application expects only a small portion of the parcel to be altered, and the applicant does not want the expense of flagging areas not expected to be altered. In these cases, Conservation Commissions rule on wetland boundaries on a portion of the lot.
In this regard, it is worth noting the wetlands, as delineated on the plans do not include a wetland area identified by the Massachusetts Wetland Conservancy Program. This three-quarter acre wetland is located towards the back of lots 30 and 35. This wetland area requires further review by the Conservation Commission.
2. The identified "isolated wetland" has a drainage ditch (as depicted on the submitted plans) connecting the wetland to a pond and cranberry bog beyond the northwest corner of the property. Part of this ditch is shown on the USGS map as a stream. Even if this is not a perennial stream with standing water (that is, if it is an intermittent stream), the existence of this hydraulic connection to the pond and bog, may change this wetland resource from isolated to "bordering vegetated wetland" under the wetland regulations. Further investigation may be needed of the boundary of this "isolated" wetland and drainage ditch.
3. The Natural Heritage and Endangered Species Program has identified a Potential Vernal Pool in the first "isolated" wetland (see attached map).
4. A drainage ditch located on the southern portion of the property connects a cranberry bog (offsite) to Tihonet Pond. The status of this ditch (perennial or intermittent stream?) and how it will be regulated under the Wetlands Protection Act to accommodate the proposed swale for the subdivision needs to be determined.
4. The 200-foot jurisdictional boundary established by the Rivers Protection Act may affect the development of some of the lots sloping to the east. For this reason, it is important to establish the jurisdictional boundary of Wankinco River at the north end of the Tihonet Pond.
5. Tihonet Pond has been identified (Commonwealth of Massachusetts 303d list) as a waterbody not expected to meet surface water quality standards; organic enrichment and low dissolved oxygen are the pollutants/stressors of concern.
The DEP Stormwater Policy requires the proponent to provide adequate flood and volume storage to control the increase in runoff associated with the subdivision and adequate pollution practices to remove 80% of the Total Suspended Solids (TSS) generated from the impervious surfaces. Based on the submitted calculations, it is not clear if this 80% rule has been met. In addition, there are several pollutants that the 80% rule does not control that the Planning Board may want to have addressed especially in sensitive resource areas (such as Tihonet Pond).
Surface Water Pollution:
� Pollutants that are water-soluable (such as nitrogen and phosphorus) and are not attached to suspended solids. Stormwater practices designed to remove suspended solids are not always effective in removing water-soluable pollutants. Management practices, whether considered traditional or non-traditional, can be designed (utilizing specific design criteria) to provide treatment for the identified target pollutants. Some suggested design manuals include 2000 Maryland Stormwater Design Manual, New York State Stormwater Management Design Manual, October 2001, and Prince Georges' County Low Intensity Manual, June 1999.
� Pollution resulting from land use changes not controlled by the pollution control practices. For example pollutants associated with lawn maintenance (nutrients, pesticides, etc) that flow directly to Tihonet Pond, the ditches, or wetlands without first flowing into the structural management practices (grass swales and the Downstream Defender). These "untreated" pollutants will have a negative impact on the downstream resources.
� Pollutants that are water-soluble (such as nitrogen) and leach into the soil. Based on the soil information (Carver coarse sand), this area is highly susceptible to groundwater pollution, affecting not only the groundwater resource, but also downstream surface water and wetlands. Based on MassGIS data layer descriptions, the subdivision will be located on a medium yield aquifer (100-300 gallons per minute) and adjacent to a high yield aquifer (greater than 300 gallons per minute).
Management Options to Protect Tihonet Pond and other Receiving Waters
As described above, Tihonet Pond is already affected by low dissolved oxygen and organic enrichment. Low dissolved oxygen is typically as result of excessive nutrients stimulating the growth of algae in a waterbody. The subsequent die off and decomposition of the algae (requiring oxygen) results in low dissolved oxygen levels. Typical pollutants associated with subdivisions are nutrient (over-fertilization of lawns) and organic enrichment (lawn and leaf debris). In freshwater systems, phosphorus is the limiting nutrient that causes eutrophication.
To reduce the impact this subdivision will have on Tihonet Pond, the Planning Board should require the following:
� Limit the amount of impervious surfaces by:
1. Reducing the size of the road widths.
2. Placing deed restrictions on individual lots limiting impervious surface to the amount described in the hydrology calculations.
3. Reducing road lengths through the use of a cluster development.
� Maximize the filtration of stormwater and associated pollutants by:
1. Using vegetated drainage channels instead of the usual pipe drainage system to transport stormwater.
2. Redirecting driveway stormwater flows away from the road system and into upland, vegetated areas.
� Protect sensitive resources by:
1. Creating a cluster development with permanently protected open space.
2. Placing deed restrictions on individual lots restricting the amount and placement of lawn areas.
3. Establish a 150-foot setback of septic systems from surface water threatened by phosphorus eutrophication. This separation enables phosphorus in septic system plumes to be naturally absorbed by soils.
4. The Wareham River estuary has been identified as impaired by excessive nitrogen loading. Nitrogen in this watershed can be managed by requiring the use of nitrogen-reducing septic systems for individual lots or a package-treatment system for all the lots.
The Buzzards Bay NEP encourages the Planning Board to adopt by-laws and/or regulations that allow for low-impact development. The Project can assist the Planning Board in writing such regulations.
If you have any questions, please call the Buzzards Bay NEP.
Joseph E. Costa, Ph.D.
cc: Wareham Conservation Commission