Drawdown

1. Drawdown Drawdown Sub Committee Mario Andella Melvin BertramPaula Bertram

2. What is Drawdown? • Drawdown is the lowering of water over the Autumn period to allow oxidation, desiccation and compaction of sediments. Plant growth is affected by freezing the roots, roots then rise and plants are unable to establish themselves.

3. Advantages • May reduce available nutrients or nutrient rations, affecting algal biomass and composition • Opportunity for shoreline clean-up/structure repair • Flood control utility • May provide rooted plant control

4. Disadvantages • Possible impacts on non-target resources • Possible impairment of water supply • Alteration of downstream flows and winter water level • May result in greater nutrient availability if flushing inadequate

5. Studies Recommended/Required • According to Dominic Meringolo of Aquatic Control Technologies several reports/investigations would be needed to minimize impact to flora and fauna and to ensure that sufficient lake levels are maintained to promote healthy flora/fauna environment and to allow recreational uses.

6. Map showing water depths across the entire lake – This could be done by a professional, or by the Lake Association – using a gps sonar device depths are captured around the lake. • Using the depth map professional would evaluate the hydrology of the lake to determine safe level of draw down and environmental impacts associated with drawdown. Things that will be taken into consideration: • Sufficient depths must be maintained to allow fish to overwater. • Impacts to wetland growth must be considered. • Impact to shallow wells and water supply would have to be evaluated (including public well at Woodlands). • Important to understand hydrology budget for the water body to be certain that the water body will refill in a timely fashion. • Depending on local conservation commission, a complete hydrology study may be required.

7. Potential Reviewing Agencies • Lunenburg Conservation Commission • Shirley Conservation Commission • Division of Fisheries and Wildlife • DEP • Nashua River Watershed Association

8. Permitting • According to Lee Lyman of Lycott, the State usually will permit a drawdown of 2’ without difficulty, however anything more than 2’ is an involved permit process. Currently the level of Hickory Hills lake is lowered in accordance with the recommendations of Dam Safety (approx. 16” – 18”). • Lyman commented that the State would want documentation as to why substantial drawdown is required, he recommends a drawdown level of 6-7’to be effective. According to the Mass Lake Management handbook even an additional 12” of drawdown can be effective. • Dominic Meringolo of Aquatic indicated that in his experience typically a permit from the local Conservation only is required. • Lake Shirley’s drawdown Program is permitted by the Lunenburg and Shirley Conservation Commissions in accordance with the Wetlands Protection Act.

9. Permit Submittal Requirements in Accordance with Wetland Protection Act Public and/or Private Water Supplies Determine any wells or water supply intakes which could dry up during a drawdown. Describe mitigation to be provide if water supply impacts are unavoidable. Rare Species Demonstrate the absence of rare wildlife habitat or that drawdown will not adversely effect the habitat if present. Fisheries Estimate area and depth zones to be dewatered. Verify the presence of a deep-water pool or other refuge areas with sufficient dissolved oxygen levels to prevent fish kills. Provide drawdown/refill dates, estimate of refill time, and estimated downstream flow rates during refill. Alternative Analysis The Applicant should consider all reasonable alternatives for controlling target plants and explain why drawdown (or drawdown used with other methods) was chosen. Control of Target Species Provide a map showing the distribution/density of target and non-target plants; a list of target species to be reduced; verification that target species would be reduced; and, verification that target species would be dewatered. Dam/Outlet Control Structures Document maximum drawdown depth and evaluate the dam’s structural integrity to verify that it can withstand drawdown. Document the rate and duration of drawdown, and a contingency plan if the structure is stuck in an open position.

10. Water Quality Discuss potential project impacts to productivity, nutrient cycling, sediment inputs, and potential algal blooms. Address, sediment/erosion controls, removal of accumulated sediments prior to drawdown, and other measures to minimize potential for flushing nutrients and sediments downstream. Fisheries Discuss the potential positive and negative impacts to fish habitat, including downstream impacts to fisheries habitat resulting from low flows during refill. Provide estimated downstream flow rates during drawdown and refilling. Discuss the potential adverse impacts to freshwater shellfish species, including clams and crayfish. Wildlife Habitat Discuss potential impacts on small mammals, waterfowl, invertebrates, amphibians, and reptiles. These impacts may be related to the timing of the drawdown versus the start of hibernation or brumation periods and reductions in vegetation preferred by wildlife. Flood Control and Storm Damage Prevention Discuss the potential for downstream flooding during the drawdown and prevention of damage to public interests by flood waters or storms. Prevention of Pollution Discuss (1) the anticipated impact of drawdown on the productivity, nutrient cycling, sediment inputs and potential for algal blooms and (2) the potential for flushing nutrients, sediments and other pollutants to downstream lakes and ponds. A 401 Water Quality Certificate should also be obtained from the DEP-Division of Water Pollution Control. Bordering Vegetated Wetlands (BVW) Drawdowns commenced after November 1 with refill completed by April 1 will contribute to the protection of BVW. Variability of this date is permissible on a case-by-case basis. However, drawdowns should be completed by December 1 whenever possible to minimize wildlife impacts

11. Drawdown Schedule • The drawdown schedule will be determined by the evaluation of surrounding flora/fauna and the hydrology of the water body.In general Lee Lyman of Lycott recommends a September/October drawdown (State recommends November 1st), and then starting the refilling process after the 1st hard freeze. Dominic Meringolo of Aquatic stressed that starting the re-fill process at the appropriate time is critical, additionally minimum flow has to be maintained to support flora/fauna.

12. Lake Shirley Drawdown Program • Lake Shirley has been using drawdown as a lake management technique for many years to control macophytes. • 2002 NOI sought a 6 foot drawdown, drawdown request in 2005-2006 sought 9’ drawdown • 2006 NOI requests commencement of drawdown on October 8th at rate of 2” per day – drawdown depth anticipated to be reached on November 25th

13. Lake Shirley Drawdown Annual Reporting • Annually the LSIC submits an Annual Drawdown Report to the Shirley Conservation Commission following drawdown in accordance with Shirley Order of Conditions • Report is extensive contains information such as; • Summary of Process • Graph of drawdown levels • Monthly precipitation data • Outflow Measurements • Other Impacts • Conclusions & Recommendations

14. Lake Shirley Costs (2006 Filing) • Consultant Support & Filing Fees - $2,000 • Data Gathering & Hearing Appearances - $0 (completed by LSIC Director) Important to note that Shirley has utilized drawdown for a number of years and had a great deal of studies and data available for NOI filings. • Annual Vegetation Surveys - $3,000 each • Outflow Measuring Program - $0 if setup by River Ways Program; participation requires regular data gathering

15. Expected Costs Drawdown is a relatively inexpensive lake management technique, if the means to conduct a drawdown are present. Where an outlet structure facilitates drawdown, the cost may be as little as what is required to obtain permits, open and close the discharge structure, and monitor. If pumps are required to lower the water level, the drawdown will be more expensive. It is unusual to alter a dam for less than $100,000, but if the structure already supports water level control, costs of $3,000 to $10,000 per year would be a reasonable expectation for permitting and monitoring. Where protected species are present, permitting may be difficult and monitoring and mitigation costs can escalate. (2004 Practical Guide)

16. Areas for Further Investigation • Integrity of sluice gate to be utilized for drawdown • Details of existing limited drawdown program • Compilation of existing reports and data

17. Sources • 2004 Practical Guide to Lake Management in Massachusetts, Executive Office of Environmental Affairs • Aquatic Control Technologies http://www.aquaticcontroltech.com/physicaltreatments.html • Geosyntec Consulting http://projects.geosyntec.com/NPSManual/Fact%20Sheets/Lake%20Level%20Drawdown.pdf • Lycott Environmental http://www.lycott.com/drawdown.html • Carl Luck, Former LSIC Board of Director