6/21/2011 SEWER COMMISSION Minutes

Home Browse Search

TECHNICAL MEMORANDUM June 21, 2011 To Town of Mashpee Sewer Commission Copy to Watershed Nitrogen Management Plan From J. Jeff Gregg, P.E. Tel 774-470-1640 Subject DRAFT Hydraulic Load Tests Job No. 8612001 The Town of Mashpee (Town) is undertaking a Watershed Nitrogen Management Plan to address nitrogen enrichment issues in the Town's estuaries. One management approach is to collect wastewater, treat it to a very high level, and then recharge the treated effluent back to the ground. A key element of that planning process is identifying sites in the Town where treated effluent can be recharged to the groundwater. The purpose of this memorandum is to summarize the findings of a hydraulic load test performed at one of these sites, Site 4 (Transfer Station Site). The memorandum describes the testing that was completed and estimates this site's suitability for receiving and infiltrating treated effluent. 1 Site History 1.1 Background The Town identified a number of sites to be considered for treated effluent recharge. After a preliminary evaluation of the identified sites, the Town decided to move forward with hydraulic load testing on one site (Site 4—Transfer Station)to determine a reasonable rate of recharge that could be expected. 1.2 Preliminary Site Characterization Approximately 13 acres on the eastern side of the Mashpee municipal landfill/transfer station property is currently an undeveloped parcel in the Upper Mashpee River subwatershed of the Popponesset Bay watershed. The 2008 Draft Alternative Scenarios Analysis and Site Evaluation Report indicated that the site has the advantages of easy'access, central location, flat topography, outside of a Zone II area (contribution to an existing water supply well), and was initially identified as outside of a rare species habitat. The disadvantages of the site that were identified were the proximity of residential properties and location within the Town-designated groundwater protection district. The site is also located within one of the more sensitive watersheds, Upper Mashpee River. In addition to these disadvantages, the site was later remapped by the Division of Fisheries &Wildlife as being located within a Priority Habitat and Estimated Habitat. The site was also identified by the Massachusetts Historical Commission as a possible location of archaeological deposits. A detailed archaeological site study was performed by the Public Archaeology Laboratory and the results of the testing"identified no archaeological deposits in the areas tested." Because of the favorable nature of the site, and allowance for site investigations, the hydraulic loading tests were allowed to proceed. OHID Inc. 1545 ly-annough Poad His MA 02 1 USA T 1 774 470 1630 F 1 774 470 1631 E hyamail@glhd.com W a,Awm. d.com