Preserving Water Quality Through Watershed Planning
Technical Assistance Series

Capital Coastal Council of Governments (CCCOG, December 1990)
(89 Western Ave., Augusta, Maine 04330)

This publication is presented for "Classroom Use Only."  Its intended use is to stimulate and aid in discussion and role playing within a classroom setting.

Maine has 5,000 clear lakes, but their future water quality is being threatened. Maine's lakes are a precious resource and a critical component of the natural environment. There are approximately 76 lakes and ponds in the Capital Coastal region. The primary threat to the health of our lakes is changing land use.

Phosphorus, one of the major factors impacting lake water quality, has been shown to increase dramatically when land is converted from its naturally vegetated state to residential and commercial development. Even small amounts of phosphorus act as a fertilizer for algae, and cause algae to multiply and turn the water cloudy and green.

More than 300 Maine lakes are expected to decline within the next 25 years if present development trends continue. Of the 76 lakes in the Capital Coastal Region, 66 are considered vulnerable according to criteria developed by the Department of Environmental Protection.

Phosphorus occurs naturally in soil and organic material and is contained in such products as laundry detergents and fertilizers. Storm water runoff is the vehicle which carries phosphorus to the lakes. The forest stores and absorbs much of the rainfall by intercepting it in the leaf canopy, storing it in the irregular depressions on the forest floor and utilizing the nutrient phosphorus for growth. When runoff does occur, it passes through the layer of decaying leaves on the forest floor, which also acts as a filter and sponge for phosphorus. However, when forests are converted to residential or commercial uses, both runoff volume and the phosphorus concentration in runoff can increase dramatically.

Converting land to residential or commercial uses diminishes forested area and replaces it with lawns, driveways, roofs, roads or parking lots. When an effective land cover, such as natural forest, is replaced by residential or commercial development, the phosphorus normally taken up by trees and vegetation is carried away in the increased runoff. If erosion and sedimentation are not carefully controlled, water-borne sediments can constitute a significant source of phosphorus, in addition to naturally occurring phosphorus that has not been able to be absorbed by soil and taken up by plants.

In a nutshell, the transition from predominantly forested, undeveloped land to low-density residential development increases the amount of phosphorus that runs off the land and into lakes. An estimated 98 percent of the water quality problems in Maine's lakes are due to diffuse sources of pollution (as opposed to a single easily-identified source such as a factory). As runoff from development progresses down the watershed, it collects sediments and chemicals from the surfaces it travels over, carrying them into larger water bodies such as rivers, lakes and bays. The excess nutrients, toxic chemicals, sediments, and other contaminants contained in runoff lower water quality and damage sensitive ecosystems.

Erosion can be a particular problem in developed areas, at construction sites, and along roadways - wherever pavement, rooftops, compacted soil, or lack of vegetation allows water to flow freely and wash away accumulated debris. When storms occur, sediments, toxics and nutrients may be washed for miles until they reach the outlet water body. In fact, more than half the annual erosion load can be moved by only 5 to 10 storms.

Maintaining Water Quality

In order to minimize the further degradation of water quality from residential and commercial development, the Department of Environmental Protection has developed a method for reviewing development in lake watersheds. A lake's watershed consists of all the surrounding land that drains into the lake (see picture of Watershed).

Lake protection must extend to the entire watershed.

Based on a lake's water quality and other characteristics, the DEP has calculated a phosphorus coefficient for each watershed. This coefficient represents the amount of phosphorus that could be added to a lake annually resulting in a less than 1 part per billion increase in the phosphorus concentration of the lake.

This allocation can then be divided among the acreage in the watershed that is expected to be developed in the foreseeable future. If every new development contributed levels of phosphorus at or below its allocation, then the water quality of the lake would not be significantly lowered. DEP's handbook entitled Phosphorus Control in Lake Watershed: A Technical Guide to Evaluating New Development contains guidelines for reviewing development to make sure that it does not exceed the phosphorus allocation.

If it is determined that a development does not meet the phosphorus allocation, there are a number of changes that can be made to the design of the development to reduce the amount of phosphorus expected to be contributed to runoff in the watershed. The emphasis for the design changes is to reduce the amount of runoff from each lot. This can be done by limiting the amount of cleared land, diverting runoff from roads into a wooded buffer, reducing the number of lots, clustering lots on good soils, and/or reducing the length of roads. For large developments, engineered systems such as infiltration systems and wet ponds can be used to treat runoff, but should be considered a last resort.

Some simple site development practices that can go a long way to reducing the impact of a site on water quality include:

• avoid clearcutting the existing trees and vegetation on the house site (use native grasses and shrubs that thrive under natural rainfall conditions);
• limit the area of disturbed soil exposed at any one time;
• install gravel-filled trenches along driveways and patios to collect water and allow it to filter gradually into soils;
• minimize the area of surfaces impervious to water such as driveways, parking areas, concrete patios, roof areas;
• divert rain from paved surfaces onto level areas of groundcover, woods or grass to permit gradual absorption; and,
• leave the natural vegetation whenever possible.

For more specific information about the above activities (plant types, specifications for erosion control methods, etc.) contact one of the organizations listed at the end of this bulletin.

CCCOG is designing two brochures designed to inform residents about controlling phosphorus in lake watersheds. These brochures can be given out with building permit applications and boat and fishing licenses, regardless of whether the phosphorus method is incorporated into local ordinances. These simple brochures will be printed on standard 8 1/2" x 11" paper so that they can be easily photocopied at the Town Office. In these small ways, people who live in the watershed and use the lake can become more informed about the impact they have on water quality and what they can do about that.

In recent years, the only water quality protection available to lakes was from shoreland zoning. What really needs to happen is for each community to take a comprehensive look at development trends and natural resources in the entire watershed. In this way a picture of the lake system is developed, and effective protection measures can be developed. The following paragraphs outline the comprehensive planning that should be followed by towns concerned about the water quality of their lakes.

POLICY SECTION

Lake Protection levels (high, medium or low) need to be set for each lake. The town has a certain amount of discretion in determining the acceptable increase in lake phosphorus concentrations. The lake protection level combined with the water quality category determine the extent that the calculated phosphorus coefficient will be applied to a particular watershed. A high level of protection will result in a more stringent phosphorus allocation than a low level of protection.

Regional Consideration

Most local planning is done on a town by town basis. Unfortunately, not all lakes are located entirely in one town, and certainly not all watersheds are located entirely within the bounds of one town. In fact, it is entirely possible for land in one community to drain into a lake that is located entirely in a different community. For this reason it is very important for towns to work together in protecting their lake resources.

Existing Situations That Contribute To Water Quality Problems

The method for controlling phosphorus in lake watersheds described above is an excellent tool for maintaining current water quality. However, this may not be enough for certain lakes that already have water quality problems. Correction of some existing situations that are contributing to water quality problems may go a long way to improving water quality in the watershed.

Existing structures contribute to phosphorus loading and runoff, yet are not subject to any regulations or controls. An educational program might influence a number of owners to make at least partial attempts at reducing the negative water quality impact. During the comprehensive planning process, the committee could walk the lakeshore to inventory potential existing problems, including malfunctioning septic systems as well as erosion problems. Owners of land where the most blatant problems are occurring should be targeted for an information campaign. As these properties request additional building permits, owners might be asked to try to mitigate the existing problems.

The town itself should join in the efforts to improve water quality. An effective way to show its commitment to water quality would be for the town to develop a demonstration project that would correct an existing problem on a town maintained facility. A plan for correcting other identified problems should be pursued as well.

Public and private roads constitute a significant source of phosphorus loading to lakes. An inventory could be made by conducting a road survey shortly after a major rainfall. The town should plan projects to stabilize ditches and culverts, provide water bars across steep road segments, and divert runoff to forested roadside areas. The town itself should provide a good example to residents.

Reference Materials:

Phosphorus Control in Lake Watersheds: A Technical Guide to Evaluating New Development, September, 1989. Available from: Department of Environmental Protection, 289-3901.

Watershed: An Action Guide to Improving Maine Waters, April, 1990. Available from: Capital Coastal Council of Governments.

The Long Lake Watershed Study - A handbook for long-term protection, By Peter Lowell. Available on loan from Capital Coastal Council of Governments.

Brochure: Protecting Maine Lakes from Phosphorus Pollution. A new planning guide for cities and towns, Available from: Department of Environmental Protection, 289-2901.

Brochure: For Your Lake's Sake, prepared by Southern Maine Regional Planning Commission. Available from: Department of Environmental Protection, 289-3901.

For Further Information:

Department of Environmental Protection, Lakes Division
State House Station 17
Augusta, ME 04333
Phone: 289-3901

Capital Coastal Council of Governments
89 Western Avenue
Augusta, ME 04330
Phone: 622-7146

Cobbossee Watershed District
15 High Street
Winthrop, ME 04364
Phone: 377-2234

INVENTORY SECTION

Mapping needs (must be mapped for each watershed)

• Minimum Mapping Needs
• Watershed Boundaries
• Wetlands
• Steep Slopes
• Land Use/Structures
• Hydric soils for Identification of forested wetlands

• DeerYards
• Soils unsuitable for development

• Subdivisions that have occurred in the last 10 years

• Total area (acreage) of the Watershed

• Water Quality Category (based on water quality testing)

• Phosphorus Coefficient (the amount of additional phosphorus that the lake can absorb without increasing the phosphorus concentration by more than 1 part per billion)

Step One: Determine how much land in each watershed is unavailable for development. This can be done by examining the information mapped above. For instance, critical natural resources such as wetlands and steep slopes provide conditions that are too severe to support development. In addition, land on which structures already exist is unavailable for development. If the minimum lot size is one acre, then one acre of land for each structure should be included in the calculation of the land that is unavailable for development. Areas covered by roads, cemeteries, and other structures that would prohibit development can also be included in the calculation.

Step Two: Determine the number of acres in each watershed that are likely to be developed over a 50-year planning horizon. In order to spread the total allowable phosphorous discharge among the areas to be developed, it is necessary to estimate the amount of land likely to be developed. This can be done by looking at subdivision and development trends in the watershed over the last 10 years and projecting them 50 years into the future.

A simpler method would be to use a development factor developed by DEP for various parts of the state to estimate development levels. Using this method, the appropriate development factor (for example 25%) would be multiplied by the acreage available for development. This method assumes that not all of the available land will be developed, but a certain fraction of the land is likely to be developed.

In either case, local knowledge of development trends and the viability of sales in the watershed should be taken into consideration for a refinement of the estimate.

NOTE: If part of the lake or the watershed is located within the boundary of a neighboring town or towns, the Comprehensive Planning Committee will need to work with those towns.

Step One		Step Two
Watershed Area - 500 acres Wetland -50 acres Hydric Soils - 25 acres Steep Soils - 25 acres Existing Development - 25 acres Land unavailable for development -125 acres Land available for development - 375 acres		1 building permit issued each year 1980 - 1990. 50-year projection: 50 acres subject to development. Using 15% from table 3-3 in DEP's Phosphorus Guidebook Alternate 50-year projection: 15% x 375 acres = 56 acres to be developed. Since this is a remote pond, the committee feels that 55 acres is a reasonable estimate.