C.M.R. 01, 672, ch. 10, APPENDICES, app 672-10-A
Purpose. The purpose of the following is to determine those lakes where a density of one dwelling unit per 150* feet of shoreline of the lake would increase the phosphorus concentration of the lake water by 5 parts per billion or more.
Method. The maximum change in phosphorus loading will be determined by:
(1) [DELTA]L = [DELTA]P x DA x R
where | [DELTA] = change |
L = phosphorus loading | |
[DELTA]P = phosphorus concentration | |
[DELTA]P = .005 grams/meters3 (approximately equivalent to 5 parts per billion) | |
R = run-off coefficient (average annual run-off) | |
DA = drainage area |
Assuming 1/4 time occupancy, four people per dwelling, and a contribution of .4 x 103 grams of phosphorus per person per year to the body of water, the water quality limitation to shoreline development is:
(2) max. [DELTA]L = number of dwelling units .4 x 103 grams per year
If development was allowed to a density of 1 dwelling unit per 150 feet of shoreline, the maximum number of dwellings allowed according to shoreline length only would be:
(3) shoreline length = number of dwelling units 150 feet
If (3) is greater than (2), the lake is a water quality limiting lake;
If (2) is greater than (3), the lake is not a water quality limiting lake;
* Since the minimum shore lot frontage on major water bodies is 150 feet measured as a straight line between the points of intersection of side lot lines with the normal high water mark of the shoreline, and due to the irregularity of shoreline, the actual average shoreline measure along the normal high water mark for such lot is estimated to be 150 feet.
Sample 1
Madawaska Lake, Aroostook County
Characteristics: | |
Drainage area | = 82.9 x 106m2 |
Run-off coefficient | = .5 m/year |
Shoreline length | = 54,000 feet |
[DELTA]P | = .005 grams |
Calculations:
(1) Maximum [DELTA]L = 20.7 x 104 grams per year.
(2) Number of dwelling units allowed based on water quality limitations = 518 dwelling units.
(3) Number of dwelling units allowed based on shoreline length = 360 dwelling units.
Result: Madawaska Lake is not a water quality limiting lake.
Sample 2
Tomah Lake, Washington County
Characteristics: | |
Drainage Area | = 1.8 x 106m2 |
Run-off coefficient | = .6 m/year |
Shoreline length | = 7,000 feet |
[DELTA]P | = .005 grams |
Calculations:
(1) Maximum [DELTA]L = 5.4 x 103 grams per year.
(2) Number of dwelling units allowed based on water quality limitations = 14 dwelling units.
(3) Number of dwelling units allowed based on shoreline length = 47 dwelling units.
Result: Tomah Lake is a water quality limiting lake.
C.M.R. 01, 672, ch. 10, APPENDICES, app 672-10-A