BOARD00284

• Board Meeting Date: 1/12/1971
• Description: Agenda or Table of Contents, Minutes, Memos
• Board Meetings - Doc Type: Meeting

I

especially with respect to nutrient concentra-
tions and inputs and eutrophication. The
results of this survey are contained in a
report entitled 'Water Quality Conditions in
Grand Lake, Shadow Mountain Lake, Lake Granby'
which will be available by the end of January.
At this time I will paraphrase the summary and
conclusions and read verbatim the recommendations
of this report:

I. The laboratory analyses of samples
collected from Grand Lake, Shadow Mountain Lake
and Lake Granby show that the inorganic nitro-
gen concentrations were uniform throughout the
lakes and averaged 0.107 mgN/I over the survey
period. This concentration is approximately
one-third of that considered necessary to
initiate an algae. bloom (0.30 mgN/I). The
orthophosphate concentration in the three lakes
averaged 0.0255 mgP/I and ranged from 0.0084
mgP/l in Grand Lake to 0.0526 mgP/I in Shadow
Mountain Lake. This average concentration
greatly exceed the minimum level of orthophos-
phate considered by authorities in the field
as necessary to sustain an algae 'bloom'
(O.OlO mgp/I). In addition, the orthophosphate
concentration at the ~ottom of Lake Granby
ranged from two to thirteen times greater than
surface concentrations indicating the possibility
that anaerobic respiration may take place in the
venthic regions.

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2. The average inorganic nitrogen, ortho-
phosphate, and total soluble phosphorus con-
centrations in the natural runoff from the
surrounding watershed were 0.07 mgN/I, 0.007
mgP/I, and 0.064 mgP/l respectively. The
inorganic nitrogen and orthophosphate concen-
trations are much lower than the suggested
limits of 0.30 mgN/I, and O.OlO mgP/I respec-
tively, but the total soluble phosphorus con-
centrations exceeded the suggested limit of
0.05 mgP/l.

3. The domestic wastewater sources in the